Bluetooth is a short range (10-100 m) and low-cost wireless network system to replace cables and give RF connection between consumer devices. Bluetooth operates in the unlicensed ISM band at 2.4 GHz.
Bluetooth is a standard and communications protocol primarily designed for low power consumption, with a short range Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, personal computers, digital cameras, and video game consoles over a secure, short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group. Conceived initially by Ericsson
What is Bluetooth
The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, as long as the received transmission is powerful enough. The Bluetooth specification defines a uniform structure for a wide range of devices to connect and communicate with each other. Bluetooth is named after Harald Blåtand (Bluetooth) Gormson of Denmark, who united his country in the 10th century.
Why use it? Eliminates cables Inexpensive Easy to set up and use Readily available Good security Device compatibility
What is the range? Class 3 radios – have a range of up to 1 meter or 3 feet Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 30 feet Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet
Power Speed?
How about power? The most commonly used radio is Class 2 and uses 2.5 mW of power. Bluetooth technology is designed to have very low power consumption. How fast is it? 1 Mbps for Version 1.2 Up to 3 Mbps supported for Version 2.0
How about multiple connections?
Bluetooth enabled electronic devices connect and communicate wirelessly through shortrange, ad hoc networks known as piconets. Each device can simultaneously communicate with up to seven other devices within a single piconet. Each device can also belong to several piconets simultaneously. Piconets are established dynamically and automatically as Bluetooth enabled devices enter and leave radio proximity.
Will it conflict with other wireless technologies? Infrared – not at all WiFi – possibly, but not likely Bluetooth does operate in the 2.4 GHz band like 802.11b and 802.11g, but it uses frequency hopping instead of direct sequencing. Any possible interference would be very short-lived.
Piconet & Scatternet
Piconet
Piconet The technology allows creation of small ad-hoc networks (piconets) consisting of at most 8 simultaneously active devices.
Scatternet
Scatternet Many different piconets may coexist and interoperate in the same physical area.
Piconet & Scatternet…
A piconet consists of one master and up to 7 slaves. The master is the central entity that decides transmit/receive resource allocation to different slaves and thus controls bandwidth usage among slaves. Two or more piconets can be linked together to form a scatternet. In this, one device in each piconet (either a master or a slave) acts like a bridge between them.
Piconet & Scatternet…
Piconet & Scatternet…
A Bluetooth device can function as either a master as or a slave. Each piconet can only have a single master, but a master in one piconet can be a slave in another piconet. This allows a dynamic topology construction of complex scatternet.
Traffic/Signaling
Traffic/Signaling
The network can carry two types of information: Traffic: it concerns all the «user to user» information. It can be voice as well as data. Signaling: the network also requires to carry information for its own working. Their purposes are numerous: traffic data routing, maintenance, security... These data are usually not visible from user’s point of view.
Before GSM: Mobile Telephony Milestones
Before GSM: Mobile Telephony Milestones
1876: The telephone was introduced to the public at the Centennial Exposition of the United States in Philadelphia. Alexander Graham Bell was able to transmit speech electrically, in one direction only, over a copper wire circuit of several hundred feet in length. This “speaking telegraph” was quickly perfected for adequate two-way communication and was offered for business and residential service the following years. Within a short time there were thousands, then tens of thousand, and soon hundreds of thousand of paying customers. End of the 19th century: While the struggle to search for the ways to utilize the copper wire transmission facility more and more efficiently, a young German scientist named Heinrich Rudolf Hertz discovered a strange and wonderful phenomenon: from an electric spark there seemed to emanate invisible waves of force which could be captured at a distant location by a suitably constructed receiving device. Hertz’s own experiments extended only a few yards. 1897: Guglielmo Marconi shows the first wireless transmission over 15 km in Bristol. A few years later(1901), G. Marconi transmitted these waves overseas, and began to call it Radio.
Before GSM: Mobile Telephony Milestones
1946: The first public mobile telephone service was introduced in twenty five American cities. Each system used a single, high-powered transmitter and large tower in order to cover distances of over 50 km in a particular market. Nevertheless these early FM push-to-talk telephone systems of the late 1940s used 120 kHz of RF bandwidth in a half duplex mode (only one person on the telephone call could talk at a time), even though the actual telephone-grade speech because of the kHz of baseband spectrum. The large RF bandwidth was needed because of the difficulty in mass producing tight RF filters and lownoise, front-end receiver amplifiers. 1970: A.Pinet introduced in France the first digital switch. 1982: The first commercial cellular system was turned on in Chicago. 1992: GSM, the first fully digital cellular system, was introduced on in Germany and in France.
Analog Cellular Systems Around the World
Analog Cellular Systems Around the World There are several different types of analog cellular systems: NMT450 and NMT900: Scandinavia, Benelux, Spain, Austria, France, Switzerland AMPS (Advanced Mobile Phone System ) in more 34 countries: U.S.A., Canada, Argentine, Chile, Indonesia, Brazil Australia, Republic of Congo TACS (Total Access Communication System) in UK Ireland and Italy R2000: France C450: Germany NTT (1979) cellular and JTACS (1988) in Japan RTMS: Italy.
AMPS
AMPS is a first-generation cellular technology This cellular service operates in the 800 MHz Cellular FM band. For each market area Its is the analog mobile phone system standard developed by Bell Labs, and officially introduced in the Americas in 1983 and Australia in 1987 As of February 18, 2008, Carriers in the United States were no longer required to support AMPS and companies such as AT&T and Verizon have discontinued this service permanently. AMPS was discontinued in Australia in September 2000
AMPS
AMPS pioneers fathered the term "cellular" because of its use of small hexagonal "cells" within a system. This allowed a larger number of phones to be supported over a geographical area It suffered from some weaknesses when compared to today's digital technologies Very susceptible to static and noise No protection from eavesdropping Later, many AMPS networks were partially converted to D-AMPS
D-AMPS is a digital, 2G standard
Development of the GSM Standard 1991: First system-trial are running at Telecom 91 exhibition. The GSM Recommendations comprise: 1992: Official commercial launch of GSM service in Europe.
Development of the GSM Standard
1993: Aside the GSM has 62 members (signatories) in 39 countries worldwide; and in addition 32 potential members (observers, applicants) in 19 other countries. GSM networks are operational in Denmark, Finland, France, Greece, Ireland, Italy, Luxembourg, Norway, Portugal, Sweden, Switzerland, United kingdom. The end of 1993 shows one millions subscribers to GSM networks, however more than 80% of them are to be found in Germany alone.
GSM (short statistics, 2004)
No. of Countries/Areas with GSM System: 199 Worldwide GSM Subscribers as at end of 2007 = 2,685,060,046
Ratified Operator and Regulator Members = 585 SMS messages sent per month: 24 Billion GSM accounts for 73 % of the World's digital market and 72% of the World's wireless market
GSM (statistics, end of 2007)
GSM Benefits
GSM Benefits The features and benefits expected in the GSM
Superior speech quality (equal to or better than the existing analog cellular technology), Low terminal and services costs, A high level of security (confidentiality and fraud prevention), International roaming (under one subscriber directory number), Support of low power hand-portable terminals, Variety of new services and network facilities.
GSM Benefits
It was a logical consequence of the prevailing reality that a measure of Inter-working compatibility with the services offered by other existing telecommunication networks was sought. In particular, the basis for the services in GSM standard can be found in the ISDN concept.
GSM: System Architecture
GSM: System Architecture
Mobile Station
Mobile Station
The Mobile Station (MS) is composed of three parts:
The handset includes the radio equipment (receiver-transmitter) and the Man-Machine Interface (MMI), The SIM card (Subscriber Identity Module-card): this smart card allows the identification of any subscriber (not only of his equipment) by the network. In particular, he can borrow any mobile without changing anything from the network point of view since he keeps the same SIM-card, The battery.
Mobile Station (MS)
Mobile Subscriber Identity Module (SIM)
Removable plastic card Stores Network Specific Data such as list of carrier frequencies and current LAI (Location Area Identifier). Stores International Mobile Subscriber Identity (IMSI) + ISDN Stores Personal Identification Number (PIN) & Authentication Keys. Also stores short messages, telephone book etc.
SIM-Card and GSM Mobile Equipment
SIM-Card and GSM Mobile Equipment
The subscriber is identified within the system when he inserts the SIM-Card in the mobile equipment and switches it on. This provide a considerable amount of flexibility to the subscribers since they can use any GSMspecified mobile equipment. With the SIM-Card the idea of "personal communication" is already realized: the user only needs to take his smart card on a trip. You can rent a mobile equipment unit at the destination, even in other country, and insert your own SIM-Card. Any call you make will be charged to your home GSM account. Also the GSM system is able to reach you at the mobile unit you are currently using.
The SIM-Card Functions
The SIM-Card Functions
The SIM-Card is a removable smart card, the size of a credit card, and contains an integrated circuit chip with a microprocessor, random access memory, and read-only memory. When a mobile users want to make a call, they insert their SIM-Card and provide their Personal Identity Number (PIN), which is compared with a PIN stored within the SIM-CARD. The PIN can also be permanently bypassed by the subscribers if authorized by the service provider. Disabling the PIN code simplifies the call setup but reduces the protection of the user's account in the event of a stolen SIM-CARD.
Subscriber Identification
The International Mobile Subscriber Identity (IMSI) is the primary identification of the subscriber within the GSM network and is permanently assigned to him. The Mobile Subscriber ISDN Number (MSISDN) is the number that the calling party dials in order to reach the GSM subscriber. It is used by the land networks to route calls toward an appropriate GSM network. MSISDN is stored in HLR.
GSM Mobile Equipment
The Mobile Station (MS) includes radio equipment and the man machine interface (MMI) that a subscriber needs in order to access the services provided by the GSM network. Mobile Stations can be installed in vehicles or can be portable or hand-held stations. The mobile station includes provisions for data communication as well as voice. Mobile Stations transmit and receive messages to and from the GSM over the air interface to establish and continue connection through the system. Each mobile station has an International Mobile Equipment Identity (IMEI) that is permanently stored in the mobile unit. Upon request, the MS sends this number over the signaling channel to the network. The IMEI is used to identify mobile units that are reported stolen or operating incorrectly.
Mobile Identification
Stored inside the Mobile Equipment. Some time can work without SIM card (example: Emergency calls without SIM-Card) or when required by the network (for maintenance). Can be used for EIR (Equipment Identification Register) database updating (when existing):
TAC = 6 digits describing the type of equipment, FAC = 2 digits for identification of the factory, SNR = 6 digits for the serial number of the device.
The type of MS must be given to the NSS at the beginning of each new connection, because this type can change between calls. The subscriber may insert this SIM-Card into another Mobile Equipment (ME).
Trends in Mobile Station
Trends for MS are:
Hands-free (2 W + booster 5 W). Increasing independence:
Supplementary features (e.g. display of calling number). Additional features (e.g. voice recognition). Connection with terminals for data transmission:
idle mode: 40 hours to 140 hours, communication mode: 4 hours to 15 hours,
Modem on PCMCIA board for Laptop PC. Modem integrated.
Dual-band terminal (GSM 900/1800 MHz). Radio organizer (Nokia 9000). Versatile terminal (under JAVA software's): fax, internet, pager, organizer.
Base Transceiver Station (BTS) One per cell Consists of high speed transmitter and receiver Function of BTS Controls several transmitters Provides two channels
Signalling and Data Channel
Performs error protection coding for the radio channel
Base Station Controller (BSC)
Controls multiple BTS Functions of BSC
Performs radio resource management
Assigns and releases frequencies and time slots for all the MSs in its area Reallocation of frequencies among cells Hand over protocol is executed here
Time and frequency synchronization signals to BTSs Knows which mobile stations are within the cell and informs the MSC/VLR about this Power Management of BTS and MS know the exact location of a MS before a call is made
Mobile Switching Centre (MSC)
Switching node of a PLMN (Public Land Mobile Network) Allocation of radio resource (RR)
Mobility of subscribers
Handover Location registration of subscriber
There can be several MSCs in a PLMN
Gateway MSC (GMSC) Connects mobile network to a fixed network Entry point to a PLMN Usually one per PLMN Request routing information from the HLR and routes the connection to the local MSC
HLR/VLR
HLR - Home Location Register
For all users registered with the network, HLR keeps user profile MSCs exchange information with HLR When MS registers with a new GMSC, the HLR sends the user profile to the new MSC
VLR - Visitor Location Register
VLR is responsible for a group of location areas, typically associated with an MSC Contains the location of the active Mobile Stations
AuC/EIR/OSS
AuC: Authentication Center is accessed by HLR to authenticate a user for service Contains authentication and encryption keys for subscribers EIR: Equipment Identity Register International Mobile Station Equipment Identity (IMEI) codes allows stolen or fraudulent mobile stations to be identified Operation subsystem (OSS): Operations and maintenance center (OMC), network management center (NMC), and administration center (ADC) work together to monitor, control, maintain, and manage the network
GSM identifiers
International mobile subscriber identity (IMSI):
International mobile station equipment identity (IMEI):
unique 15 digits assigned by service provider = home country code + home GSM network code + mobile subscriber ID + national mobile subscriber ID unique 14 digits assigned by equipment manufacturer = type approval code + final assembly code + serial number + spare digit
Temporary mobile subscriber identity (TMSI):
32-bit number assigned by VLR to uniquely identify a mobile station within a VLR’s area
Explosive Growth in Wireless Data
Motivations Growing demand of data services due to Internet PSTN/ISDN tends to become local islands connected with the IP backbone Solution: To associate the traditional GSM (Circuit switched ) network with Packet switched, all IP network
No hardware/software change is requires in BTSs and BSCs. Same radio interface GPRS uses the same Radio Access Network (RAN) as GSM
A Packet Control Unit is added to the BSS
Basic characteristics
Using from 1 to 8 time slots on the same carrier max bit rate 171.2 kb/s, 8*21.4 kb/s
User charging based on the amount of data transmission …
Thus allowing, Always-On-Connections
Interact with IP Supports various level of QoS
General Packet Radio Service
Important elements
Serving GPRS Support Node (SGSN)
Gateway GPRS Support Node (GGSN)
Tracks the location of the MS Provides routing and mobility management Authenticates the MS Manages the session Collects billing data IP packets from the MS are treated as IP packets first time here Connects the GPRS network to other networks, e.g. the Internet
GSM VLR and HLR are used
GPRS Handovers
There are no GPRS handovers as such
Since there is no circuit to hand over
The MS requests a cell reselection and the packets are routed to the new cell Requires dynamic routing
General Packet Radio Service
GPRS is the first major revolution in GSM data, providing speeds over 100 kbit/s on a pseudo-packet switched radio interface and a real packet switched NSS. This will encourage users to connect to high-speed applications across the wireless network and optimizes the network resources for data transmission. There are however some limitations and the first implementations will have mobility constraints. However, it is likely to attract users to internet type services and provides operators with a natural migration path towards 3G systems.
Universal Mobile Telecommunication System
UMTS, or more precisely IMT2000, will at first provide a capacity advantage for wireless data networks that become overcrowded. But it has to provide more than that. The higher data rates will allow applications such as video and multimedia (support 2mb/s). Open architecture will provide a service environment allowing a wide range of services to be developed by operators and service specialists. Total global roaming is one of the objectives of the specifications.
UMTS
Handover
Compatibility with fixed network services
Seamless handover between cells of one operator Efficient handover between UMTS and 2nd generation ATM an ISDN services GSM services IP based services
Facilities for quality of service provision Private and residential operators High spectrum efficiency Asymmetric band usage Reasonable network cost and complexity
Enhanced Data rate for GSM Evolution
GSM Enhanced Data rate for GSM Evolution or EDGE is often referred to in GPRS context as the combination of the two technologies is seen by some groups in the mobile industry as an alternative for UMTS. This makes EDGE an alternative for operators without an UMTS license who wish to offer medium-speed mobile data services. EDGE is being defined for both GPRS and GSM data services. EDGE is a redefinition of the GSM modulation and coding scheme from GMSK to 8-PSK. It gives up to three times higher throughput compared to GSM, using the same bandwidth. This will enable enduser data rates of maximum 48 kbps per Time Slot for GPRS and 28.8 kbps per TS for GSM services. By combining multiple TSs as with GPRS, data rates of 384 kbps can be achieved.
Traffic/Signaling
Traffic/Signaling
The network can carry two types of information:
Traffic: it concerns all the «user to user» information. It can be voice as well as data. Signaling: the network also requires to carry information for its own working. Their purposes are numerous: traffic data routing, maintenance, security... These data are usually not visible from user’s point of view.
Teleservices
Telephony Emergency Call Short Message Cell Broadcast Short Message Service Fax User's Data Call Features Voice Messaging
Teleservices
Teleservices
Teleservices cover regular telephony, emergency calls, voice messaging, and short messages handling. The most important service provided by GSM users is telephony which enables bi-directional speech calls to be placed between GSM users and any telephone subscriber who is reachable through the general telephony network. Fixed telephone subscribers worldwide as well as mobile network subscribers or subscribers of specific networks connected to a public telephone network can be reached. Before either Mobile Originated or Mobile Terminated calls can be established, the mobile telephone must be switched on and registered into the system.
Teleservices
Teleservices
To place an emergency call enter 112 followed by SEND. Additional means to place such call are also allowed by a dedicated button. The Mobile Telephone supports the initiation of an emergency call without a SIM present in it, regardless of the call being accepted or not by the network. Note that calls to national emergency services may be standard for the country of the serving GSM network (number 17 to call the police in France, number 911 to make an emergency call in U.S.A.). However, with the exception of code "112", these are not treated within the GSM network as "teleservice emergency call" and would require a valid IMSI.
Teleservices
Teleservices
The cell broadcast enables an Information Provider to submit short messages for broadcasting to a specified area within the GSM network. The cell broadcast service has the following features:
The cell broadcast message is sent (on control channels) in a limited area, defined by the originator of the message, by agreement with the GSM Operator. The mobile telephone only receive the broadcast message in idle mode. The short message function running in the mobile is able not to store broadcast messages which are not wanted or which have already been received. The mobile telephone does not send acknowledgment. The GSM network continuously sends cell broadcast messages so that all such messages are sent in turn, an then repeated. On the other hand, the cycle time is short enough for important messages to be received by travelers (subscribers) moving through a group of cells. The maximum length of each cell broadcast message will be 93 characters and GSM specifications allows up to 15 of these 93 character messages treated as segment of a longer message.
Teleservices
Teleservices
Short Message Service (SMS) allows the point to point transmission of a short message to/from MS, using their IMSI. A short message is an alphanumeric string that can be up to 160 characters long. Two different types of short message are defined:
Short message MT/PP (Mobile Terminated / Point to Point), Short message MO/PP (Mobile Originated / Point to Point).
Point to point messages may be sent or received when the MS is engaged on a call (voice or data), or in idle mode. However, messages which overlap the boundary of such a call, or during a handover, may be lost, in which case they will be sent again.
Teleservices
Teleservices
Fax transmissions are possible via a PLMN only with a Fax-group3 (14.4 kbps). Two modes are available:
Manual mode allows to switch alternatively from voice transmission to fax transmission, Automatic mode allows to send and receive a fax without any human intervention;
However, voice transmission is impossible in this mode.
Teleservices
Teleservices
Connections can be made with a suitable data/fax kit adaptation either to other Mobile Station or to other data users on circuit-switched (PSTN). In the case of making a Fax-call to a PSTN subscriber, the GSM network automatically selects the suitable modem for the link to the similar modem at the remote end.
Teleservices
Teleservices
Another service derived from telephony is voice messaging. Many operators offer it as a basic feature. It enables a voice message to be stored for later retrieval by the mobile recipient, either because he was not reachable at time of the call or because the calling party choose to access the voice mailbox of the GSM subscriber directly.
Supplementary Services
Line Identification Call Transfer and Call Forwarding Waiting / Hold and Multi Party Call Barring Call Completion (CCBS) Advice of Charge
Supplementary Services
Supplementary Services
Calling line identification presentation (CLIP) provides the ability to indicate the number of the calling party with possible additional address information to the called party. This identity is provided to the called subscriber before answering, thus enabling him to make the decision of whether to take the call or not. Calling line identification restriction (CLIR) enables the calling party not to send any address information to the called party. Connected line identification restriction (CoLR) enables the called party not to send its phone number to the calling party. Calling Name Presentation (CNAP) provides the calling party name instead of the ISDN number. However, this service is not yet specified by GSM recommendations.
Supplementary Services
Supplementary Services
Call forwarding unconditional (CFU) allows a called mobile subscriber to have the network send all incoming calls, which are addressed to the called mobile subscriber’s directory number, to another directory number. Call forwarding on mobile subscriber busy (CFB): allows a called mobile subscriber to have the network send the incoming calls, which are addressed to the called mobile subscriber’s directory number and which meet mobile subscriber busy, definition to another directory number. Call forwarding on no reply (CFNRy) allows an called mobile subscriber to have the network send the incoming calls, which are addressed to the subscriber’s directory number and which meet no reply, to another directory number. Call forwarding on MS not reachable (CFNRc) provides for a mobile subscriber to have the network send all incoming calls, which are addressed to the called mobile directory number and meet the not reachable definition, to another directory number.
Supplementary Services
Supplementary Services
Call waiting (CW): provides a mobile subscriber with the possibility of being notified of an incoming call while his mobile telephone is in the busy state. Subsequently, the user can either answer, reject, or ignore the incoming call. Both the call waiting and call hold (described further) options are the same as those offered by the PSTN. Call Hold (HOLD): allows a served mobile subscriber to interrupt communication on an existing call and then subsequently, if desired, to reestablish communication. Multi party service (MPTY):
This Supplementary Service provides a mobile subscriber with the ability to have a multi-connection call, in other words a simultaneous communication with more than one party. A precondition for the multi-party service is that the served mobile subscriber is in control of one active call and one call on hold, both calls having been answered. In this situation the served mobile subscriber can request the network to begin the multiParty service. Once a multiParty call is active, remote parties may be added, disconnected or separated (i.e.. removed from the multiParty call but remain connected to the served mobile subscriber). The maximum number of remote parties is 5.
Supplementary Services
Supplementary Services
Barring of all outgoing call (BAOC): makes it possible for a mobile subscriber to prevent all outgoing calls. BOIC except those directed to the home PLMN country (BOIC-exHC) Barring of all incoming international (BAIC). Barring of all incoming calls when roaming outside the home GSM network country (BICRoam): makes it possible for a mobile subscriber to prevent all incoming calls that would otherwise be terminated at his directory number. This only applies to the case when the mobile subscriber roams outside his home GSM network.
Supplementary Services
Supplementary Services
Completion of calls to busy subscribers (CCBS): allows a calling mobile subscriber who encounters a busy called subscriber to be notified by the system operator when the busy called subscriber becomes free and have the operator re-initiate the call if the caller so desires. This feature has to be supported by both the originating and the terminating networks.
Supplementary Services
Supplementary Services
Advice of charge Information (AoCI): informs the user of the real-time information on progress of the cost of the call. Advice of charge Charging (AoCC): the mobile may be a money-operated mobile telephone or a standard mobile station that can display the charging information and can accept either coins or charge a credit-card.
Intelligent Network Services IN and CAMEL
Main IN Services:
Personal Number Virtual Private Network (VPN) Sponsored Cell & Call Prepaid Calling Location Inquiry Geo Zone
Intelligent Network Services IN and CAMEL
The aim of the CAMEL (Customized Application for Mobile network Enhanced Logic) is to provide GSM network operators with the ability to create specific services in their home network, and export these services to their subscribers when roaming outside the home network. CAMEL introduces the ability to provide location dependent IN type of services to mobiles subscribers.
Intelligent Network (IN)
The Intelligent Network or IN is a switching network concept. Its idea is to make GSM services system an open system; that is to say new services modules can always be added on the previous system without changing its architecture. Basic call processing is performed by the switch and when it recognizes that a call requires an IN service, this service processing is provided by another entity, located either in the same site or in a remote site. This concept allows to implement numerous new services such as:
Personal Number: gives the GSM subscribers more control over incoming calls, Virtual Private Network: a set of corporate services that enables similar functions to those of private network, among a group of GSM subscribers, Sponsored Cell and Call: allows a third party, as sponsor, to play announcement at the beginning of the call, Prepaid Calling: allows subscriber to pay in advance for the calls they will make.
Customized Application for Mobile network Enhanced Logic (CAMEL)
To communicate between Intelligent Network platforms, GSM specifications define CAMEL (Customized Application for Mobile network Enhanced Logic). The aim of the CAMEL is to provide network operators with the ability to create specific services in their home network, and export these services to their subscribers when roaming outside the home network. CAMEL introduces the ability to provide location dependent IN type of services to mobiles subscribers: Location Enquiry and Geo Zone.
IN Services: Virtual Private Network
IN Services: Virtual Private Network
Virtual Private Network (VPN) is a set of corporate services that enables private network like features among a group of GSM subscribers and wireline users; thus, corporations can distribute GSM phones to their employees, providing them with many of the services that they use on their existing corporate network: Private Numbering Plan: subscribers can reach all members of the corporate private network, GSM as well as wireline, by dialing their usual internal number instead of the longer, harder to remember, public number. Off Net Calling: subscribers are allowed to call public numbers that are outside the corporate private network. Forced On Net Calling: when a subscriber makes a call to a member of the corporate private network using their public number (he must also be provisioned with Off Net Calling), the feature recognizes the call as a private call and treats it as such (appropriate billing, etc.).
IN Services: Virtual Private Network
White (/Black) List Screening: subscribers with White (/ Black) List, can only (/ can not) place calls to numbers listed on it. Geographic Routing: specific numbers can be configured to route calls differently depending on the location of the caller. Time Screening (/ Routing): some specific numbers can be configured to restrict access (/ to route calls differently) depending on the time of the day, day of the week, day of the year or whether the day is a statutory holiday. Privileged Routing: specific numbers can be configured to route calls differently depending on the identity of the caller. Closer user group (CUG): provides the possibility for a group of subscribers, connected to the GSM network and or to the PSTN/ISDN, to communicate only among themselves or receive external calls; emergency calls still are available.
IN Services: Prepaid Calling
IN Services: Prepaid Calling
Prepaid Calling enables subscribers to control their phone call expenditure, by deciding how much to spend and limiting themselves to that amount if required. Subscribers pay in advance for their calls and get their calls released when the balance becomes null; thus, subscribers get a cost-control (useful for rental companies, hotels, special events, parents wanting to give mobiles to their children). With Prepaid Calling, subscribers are able to:
Make and receive calls (service is totally transparent to the subscriber during normal use), Be notified of a low balance or a pending expiry date (if the threshold is reached, the subscriber can be notified by warning tones before the call is taken down), Use Voice Mail, Query the status of their account at any time from any phone and recharge their account.
IN Services: Prepaid Calling
The subscriber can also be informed of his account balance and of the cost of his last call, at the end of each call, via a short message. Additionally, the Operator can apply different rates to calls and manage the life of prepaid subscriptions. Nortel’s prepaid solution currently supports all major recharging options, for increased service usage and enhanced customer satisfaction:
Automatically, by vouchers (e.g. scratch card), Automatically, by credit card, Manually (through Customer Services), by any means of payment.
IN Services: Sponsored Cell & Call
IN Services: Sponsored Cell & Call
Sponsored Cell & Call allows a third party (the sponsor) to play a promotional announcement at the beginning of a call and for this service, pays for part of the ongoing call. The main features of Sponsored Cell & Call are: Choice to sponsor the call & choice of sponsor based on one or more of the following:
The calling party location, The calling party profile (age ...), Time of day, day of week, Destination (emergency, freephone ...).
Sponsor can change his announcement on the phone. User can specify certain destinations as not sponsored. User can have the choice of having his call sponsored or not. User can cut through the announcement, but the call is not sponsored. User can be prevented from cutting through the announcement.
IN Services: Location Inquiry
IN Services: Location Inquiry
Location Inquiry provides GSM subscribers with information on where to locate useful services in their current area. It enables easy connection to any service they are interested in and wish to talk to. However, while GSM subscribers are out of the office or away from home, they do not have access to this information easily e.g. yellow pages, guides. Most of time, they may be even more reliant on this information because they often are in a foreign environment, e.g. in another part of town or out of town. The Location Inquiry service brings in a third party known as the “Advertiser” who seeks to sell their products/services using the operator’s network. Location Inquiry may also list services such as hospitals, doctors, pharmacies, etc. and be promoted as a personal security service. The main features of Location Inquiry are:
Location dependent information based on subscriber’s cell, Possible customization of the announcement by the advertiser (special offer of the day...).
IN Services: Geo Zone
IN Services: Geo Zone
The main features of the outgoing side of Geo Zone are:
Zone dependent tariffing of outgoing calls:
up to 4 zones per subscriber, each zone has its own tariff,
Information on the current zone available to the subscriber via:
announcement or tones at the beginning of the call, optionally by a display on the mobile (in which case it must support it, which means specific development on the handset).
IN Services: Geo Zone
IN Services: Geo Zone
The main features of the incoming side of Geo Zone are:
Routing of incoming calls according to the subscriber’s location:
if the subscriber is in his Geo Zone, the call is routed to his mobile handset, thus he does not have to pay anything, if the subscriber is out of his Geo Zone, the call can be either routed to his voice-mail, or to his mobile handset; in the last case the subscriber pays for the forwarding leg,
Information on the current zone available to the subscriber, when receiving a call via:
announcement or tones before the call is connected.
Channels Channel can be Signaling or for Traffic These are of two types
Downlink Uplink
TCH/F - Traffic Channel Full Rate
The Full Rate channel in GSM is identified as a 22.8Kbps gross bit rate channel. This channel is bidirectional enabling the transfer of speech or circuit switched data. Signaling associated with this traffic channel will be carried on either the SACCH (Slow Associated Control Channel) or the FACCH (Fast Associated Control Channel). The latest releases of GSM include EDGE (Enhanced Data rates for Global Evolution) functionality which increases the gross rate.
FACCH - Fast Associated Control Channel
The Fast Associated Control Channel appears in place of the traffic channel when lengthy signaling is required between a GSM mobile and the network while the mobile is in call. The channel is indicated by use of the stealing flags in the normal burst. Typical signaling where this may be employed is during cell handover.
SACCH - Slow Associated Control Channel
A GSM signalling channel that provides a relatively slow signalling connection. The SACCH is associated with either a traffic or dedicated channel. The SACCH can also be used to transfer SMS (Short Message Service) messages if associated with a traffic channel.
BCCH - Broadcast Control Channel
This downlink channel contains specific parameters needed by a mobile in order that it can identify the network and gain access to it. Typical information includes the LAC (Location Area Code) and RAC (Routing Area Code), the MNC (Mobile Network Code) and BA (BCCH Allocation) list.
ACCH - Associated Control Channel
The GSM signalling channels associated with a user’s traffic channel or dedicated signalling channel. Two ACCH are defined for GSM Circuit Switched operation. These are SACCH (Slow Associated Control Channel) and FACCH (Fast Associated Control Channel). In GPRS packet operation, a ACCH is allocated in conjunction with a PDTCH (Packet Data Traffic Channel) and is termed a PACCH (Packet Associated Control Channel).
DCCH - Dedicated Control Channel (GSM)
These channels are used for signaling between the network and the mobile. They comprise of the SDCCH (Standalone Dedicated Control Channel), the SACCH (Slow Associated Control Channel) and the FACCH (Fast Associated Control Channel).
DCCH - Dedicated Control Channel (UMTS)
A UMTS (Universal Mobile Telecommunication System) point to point bidirectional channel that transmits dedicated control information between a UE (User Equipment) and the network. This channel is established through the RRC (Radio Resource Control) connection setup procedure.
AGCH - Access Grant Channel
The Access Grant Channel is used to assign resources to a user requesting access to the network. These resources will include the dedicated channel to be used along with timing advance information.
PCH - Paging Channel (Generic)
The Paging Channel is used to alert a mobile that there is a call or text message waiting. The alert is broadcast from all cells within a given area.
PACCH - Packet Associated Control Channel
The Packet Associated Control Channel conveys signalling information related to a given GPRS mobile such as acknowledgements and power control information. The PACCH also carries resource assignment and reassignment messages.
SCH - Synchronization Channel
The Synchronization Channel is a downlink signal channel used for cell search and conveying of synchronization information.
GSM handoffs
Intra-BSS: if old and new BTSs are attached to same base station
MSC is not involved
Intra-MSC: if old and new BTSs are attached to different base stations but within same MSC Inter-MSC: if MSCs are changed
GSM Intra-MSC handoff 1.
2.
3.
4. 5.
6.
Mobile station monitors signal quality and determines handoff is required, sends signal measurements to serving BSS Serving BSS sends handoff request to MSC with ranked list of qualified target BSSs MSC determines that best candidate BSS is under its control MSC reserves a trunk to target BSS Target BSS selects and reserves radio channels for new connection, sends Ack to MSC MSC notifies serving BSS to begin handoff, including new radio channel assignment
GSM Intra-MSC handoff 7.
8.
9. 10.
11.
12.
Serving BSS forwards new radio channel assignment to mobile station Mobile station retunes to new radio channel, notifies target BSS on new channel Target BSS notifies MSC that handoff is detected Target BSS and mobile station exchange messages to synchronize transmission in proper timeslot MSC switches voice connection to target BSS, which responds when handoff is complete MSC notifies serving BSS to release old radio traffic channel
GSM Inter-MSC handoff 1. 2. 3.
4. 5. 6. 7. 8.
MS sends signal measurements to serving BSS Serving BSS sends handoff request to MSC Serving MSC determines that best candidate BSS is under control of a target MSC and calls target MSC Target MSC notifies its VLR to assign a TMSI Target VLR returns TMSI Target MSC reserves a trunk to target BSS Target BSS selects and reserves radio channels for new connection, sends Ack to target MSC Target MSC notifies serving MSC that it is ready for handoff
GSM Inter-MSC handoff 9.
10.
11.
12.
13. 14.
15. 16.
Serving MSC notifies serving BSS to begin handoff, including new radio channel assignment Serving BSS forwards new radio channel assignment to mobile station Mobile station retunes to new radio channel, notifies target BSS on new channel Target BSS notifies target MSC that handoff is detected Target BSS and mobile station synchronize timeslot Voice connection is switched to target BSS, which responds when handoff is complete Target MSC notifies serving MSC Old network resources are released
Geometric Representation
Cells are commonly represented by hexagons.
Why hexagon? How about circle? How about square, or triangle?
Hexagonal Cells
Channel Reuse
The total number of channels are divided into K groups.
K is called reuse factor or cluster size.
Each cell is assigned one of the groups. The same group can be reused by two different cells provided that they are sufficiently far apart.
Example K=7
Channel Reuse
Coordinate System
Use (i,j) to denote a particular cell. Example: Cell A is represented by (2,1).
Distance Formula D 3(i 2 ij j 2 ) R 3K R R
where D
K i ij j 2
Reuse factor
2
Air Interface: MS to BTS Uplink/Downlink of 25MHz 890 -915 MHz for Up link 935 - 960 MHz for Down link Combination of frequency division and time division multiplexing FDMA
TDMA
124 channels of 200 kHz Burst
Modulation used
Gaussian Minimum Shift Keying (GMSK)
Number of channels in GSM
Freq. Carrier: 200 kHz TDMA: 8 time slots per freq carrier No. of carriers = 25 MHz / 200 kHz = 125 Max no. of user channels = 125 * 8 = 1000 Considering guard bands = 124 * 8 = 992 channels
Frequency Reusage
If a mobile company got the bandwidth of 12MHz with the guardband of 5 KHz and the seperation band of 10 KHz
How many channels will be available for communication in the above scenario ? How many channels will be available if we have a cluster of K = 19 in a BSC of 380 cells? How many channels will be available if we reuse frequency at level one?
Outgoing call setup
User keys in the number and presses send Mobile transmits request on uplink signaling channel If network can process the call, BS sends a channel allocation message Network proceeds to setup the connection
Network activity:
MSC determines current location of target mobile using HLR, VLR and by communicating with other MSCs Source MSC initiates a call setup message to MSC covering target area
Incoming call setup Target MSC initiates a paging message BSs forward the paging message on downlink channel in coverage area If mobile is on (monitoring the signaling channel), it responds to BS BS sends a channel allocation message and informs MSC
Network activity:
Network completes the two halves of the connection
LAI
Location Area Identifier of an LA of a PLMN
Based on international ISDN numbering plan
(A Public Land Mobile Network is a generic name for all mobile wireless networks that use land based radio transmitters or base stations.)
Country Code (CC): 2,3+ decimal digits Mobile Network Code (MNC): 2,3 decimal digits Location Area Code (LAC) : maximum 5 decimal digits, or maximum twice 8 bits, coded in hexadecimal
Is broadcast regularly by the BTS on broadcast channel
Cell Identifier (CI)
Within LA, individual cells are uniquely identified with Cell Identifier (CI). It is maximum 2*8 bits LAI + CI = Global Cell Identity
Cellular Concept
Base stations (BS): implement space division multiplex
Each BS covers a certain transmission area (cell) Each BS is allocated a portion of the total number of channels available Cluster: group of nearby BSs that together use all available channels
Mobile stations communicate only via the base station, using FDMA, TDMA, CDMA…
Example: Incoming Call Setup MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC MS BSS/MSC
---------------------------------------------------------------------------------
Paging request Channel request Immediate Assignment Paging Response Authentication Request Authentication Response Cipher Mode Command Cipher Mode Compl. Setup Call Confirmation Assignment Command Assignment Compl. Alert Connect Connect Acknowledge Data
(PCH) (RACH) (AGCH) (SDCCH) (SDCCH) (SDCCH) (SDCCH) (SDCCH) (SDCCH) (SDCCH) (SDCCH) (FACCH) (FACCH) (FACCH) (FACCH) (TCH)
Lecture 07 Irshad Ahmed Soomro
GSM Global System for Mobile Communication
Wireless System Definitions Mobile
Station
A station in the cellular radio service intended for use while in motion at unspecified locations. They can be either hand-held personal units (portables) or installed on vehicles (mobiles)
Base station
A fixed station in a mobile radio system used for radio communication with the mobile stations. Base stations are located at the center or edge of a coverage region. They consists of radio channels and transmitter and receiver antennas mounted on top of a tower. Link mobiles through a backbone network.
Wireless System Definitions Mobile
Switching Center
Switching center which coordinates the routing of calls in a large service area. In a cellular radio system, the MSC connections the cellular base stations and the mobiles to the PSTN (telephone network). It is also called Mobile Telephone Switching Office (MTSO)
Subscriber
A user who pays subscription charges for using a mobile communication system Mobile or portable user.
Transceiver
A device capable of simultaneously transmitting and receiving radio signals
Wireless System Definitions Control
Channel
Radio channel used for transmission of call setup, call request, call initiation and other beacon and control purposes.
Forward
Radio channel used for transmission of information from the base station to the mobile
Reverse
Channel Channel
Radio channel used for transmission of information from mobile to base station
Base Station - Mobile Network RVC RCC
FVC FCC
Forward Voice Channel Reverse Voice Channel Forward Control Channel Reverse Control Channel
Wireless System Definitions Handoff
The process of transferring a mobile station from one channel or base station to an other.
Roamer
A mobile station which operates in a service area (market) other than that from which service has been subscribed.
Page
A brief message which is broadcast over the entire service area, usually in simulcast fashion by many base stations at the same time.
What is GSM ? Global
System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation.
GSM: History • Developed by Group Spéciale Mobile (founded 1982) which was an initiative of CEPT ( Conference of European Post and Telecommunication ) • Aim : to replace the incompatible analog system • Presently the responsibility of GSM standardization resides with special mobile group under ETSI ( European telecommunication Standards Institute ) Full set of specifications phase-I became available in 1990 • Under ETSI, GSM is named as “ Global System for Mobile communication “ • Today many providers all over the world use GSM (more than 135 countries in Asia, Africa, Europe, Australia, America) • More than 1300 million subscribers in world and 45 million subscriber in India.
GSM Evolution for Data Access 2 Mbps UMTS
384 kbps 115 kbps
EDGE
GPRS 9.6 kbps GSM
1997
2000
GSM evolution
2003
2003+ 3G
BSC MS
PSTN ISDN PDN
GSM System Architecture
BTS MSC GMSC
BTS
BSC VLR MS EIR
BTS
AUC MS
HLR
GSM: elements and interfaces
GSM: elements and interfaces
GSM System Architecture
Mobile Station (MS) Mobile Equipment (ME) Subscriber Identity Module (SIM) Base Station Subsystem (BSS) Base Transceiver Station (BTS) Base Station Controller (BSC) Network Switching Subsystem(NSS) Mobile Switching Center (MSC) Home Location Register (HLR) Visitor Location Register (VLR) Authentication Center (AUC) Equipment Identity Register (EIR)
System Architecture Mobile Station (MS) The Mobile Station is made up of two entities: MS =
+
ME
1.
2.
SIM
Mobile Equipment (ME) Subscriber Identity Module (SIM)
System Architecture Mobile Station (MS) Mobile Equipment
Portable,vehicle mounted, hand held device Uniquely identified by an IMEI (International Mobile Equipment Identity) Voice and data transmission Monitoring power and signal quality of surrounding cells for optimum handover Power level : 0.8W – 20 W 160 character long SMS.
System Architecture Mobile Station (MS) contd. Subscriber Identity Module (SIM)
Smart card contains the International Mobile Subscriber Identity (IMSI) Allows user to send and receive calls and receive other subscribed services Encoded network identification details - Key Ki,Kc and A3,A5 and A8 algorithms Protected by a password or PIN Can be moved from phone to phone – contains key information to activate the phone
System Architecture Base Station Subsystem (BSS) Base Station Subsystem is composed of two parts that communicate across the standardized Abis interface allowing operation between components made by different suppliers 1. 2.
Base Transceiver Station (BTS) Base Station Controller (BSC)
System Architecture Base Station Subsystem (BSS)
Base Transceiver Station (BTS):
Encodes,encrypts,multiplexes,modulates and feeds the RF signals to the antenna. Frequency hopping Communicates with Mobile station and BSC Consists of Transceivers (TRX) units
System Architecture Base Station Subsystem (BSS) Base Station Controller (BSC)
Manages Radio resources for BTS Assigns Frequency and time slots for all MS’s in its area Handles call set up Handover for each MS Radio Power control It communicates with MSC and BTS
System Architecture Network Switching Subsystem(NSS) Mobile Switching Center (MSC)
Heart of the network Manages communication between GSM and other networks Call setup function and basic switching Call routing Billing information and collection Mobility management - Registration - Location Updating - Inter BSS and inter MSC call handoff MSC does gateway function while its customer roams to other network by using HLR/VLR.
System Architecture Network Switching Subsystem
Home Location Registers (HLR) - permanent database about mobile subscribers in a large service area(generally one per GSM network operator) - database contains IMSI,MSISDN,prepaid/postpaid,roaming restrictions,supplementary services.
Visitor Location Registers (VLR) -
-
Temporary database which updates whenever new MS enters its area, by HLR database Controls those mobiles roaming in its area Reduces number of queries to HLR Database contains IMSI,TMSI,MSISDN,MSRN,Location Area,authentication key
System Architecture Network Switching Subsystem
Authentication Center (AUC) - Protects against intruders in air interface -
-
Maintains authentication keys and algorithms and provides security triplets ( RAND, SRES, Kc) Generally associated with HLR
Equipment Identity Register (EIR) - Database that is used to track handsets using the -
-
IMEI (International Mobile Equipment Identity) Made up of three sub-classes: The White List, The Black List and the Gray List Only one EIR per PLMN
GSM Specifications-1 RF
Spectrum GSM 900 Mobile to BTS (uplink): 890-915 Mhz BTS to Mobile(downlink):935-960 Mhz Bandwidth : 2* 25 Mhz GSM 1800 Mobile to BTS (uplink): 1710-1785 Mhz BTS to Mobile(downlink) 1805-1880 Mhz Bandwidth : 2* 75 Mhz
GSM Specification-II Carrier
Separation : 200 Khz Duplex Distance : 45 Mhz No. of RF carriers : 124 Access Method : TDMA/FDMA Modulation Method : GMSK Modulation data rate : 270.833 Kbps
GSM - TDMA/FDMA
26
GSM call routing
1. MSISDN
LA2
ISDN 4. MSRN BSC
MS
GMSC/I WF
BTS
2. MSISDN MSC 3. MSRN
7. TMSI 7. TMSI
EIR
BSC
AUC HLR VLR
LA1
BTS
7. TMSI
BTS MS
5. MSRN
6. TMSI
8. TMSI
Mobile Communication
27
Incoming Call (11) (9) (7) MS
BTS
(8) BSC
BTS
BTS
(6) MSC
(12)
(10) VLR
(1) Telephone
(5)
PSTN
GMSC
(4)
(2) BSC
BTS
HLR BTS
(3)
Outgoing Call MS sends dialled number to BSS 2. BSS sends dialled number to MSC 3,4 MSC checks VLR if MS is allowed the requested service.If so,MSC asks BSS to allocate resources for call. 5 MSC routes the call to GMSC 6 GMSC routes the call to local exchange of called user 7, 8, 9,10 Answer back(ring back) tone is routed from called user to MS via GMSC,MSC,BSS 1.
Mobile Terminated Call 1: calling a GSM subscriber 2: forwarding call to GMSC 3: signal call setup to HLR 4, 5: request MSRN from VLR 6: forward responsible MSC to GMSC 7: forward call to current MSC 8, 9: get current status of MS 10, 11: paging of MS 12, 13: MS answers 14, 15: security checks 16, 17: set up connection 30
Mobile Originated Call 1, 2: connection request 3, 4: security check 5-8: check resources (free circuit) 9-10: set up call
31
Security in GSM Security services access control/authentication
confidentiality
user SIM (Subscriber Identity Module): secret PIN (personal identification number) SIM network: challenge response method voice and signaling encrypted on the wireless link (after successful authentication)
anonymity
temporary identity TMSI (Temporary Mobile Subscriber Identity) newly assigned at each new location update (LUP) encrypted transmission
3 algorithms specified in GSM A3 for authentication (“secret”, open interface) A5 for encryption (standardized) A8 for key generation (“secret”, open interface)
32
Characteristics of GSM Standard
Fully digital system using 900,1800 MHz frequency band. TDMA over radio carriers(200 KHz carrier spacing). 8 full rate or 16 half rate TDMA channels per carrier. User/terminal authentication for fraud control. Encryption of speech and data transmission over the radio path. Full international roaming capability. Low speed data services (upto 9.6 Kb/s). Compatibility with ISDN. Support of Short Message Service (SMS).
Advantages of GSM over Analog system Capacity
increases Reduced RF transmission power and longer battery life. International roaming capability. Better security against fraud (through terminal validation and user authentication). Encryption capability for information security and privacy. Compatibility with ISDN,leading to wider range of services
The End.
Standards
A standard provides a model for development that makes it possible for a product to work regardless of the individual manufacturer They provide guidelines to manufacturers, venders and govt. agencies to ensure the kind of interconnectivity Categories of standards
De-facto (By fact)
Proprietary Non-proprietary
De-jure (By law)
Standards …
Categories of standards De-facto (By fact)
Proprietary :
Non-proprietary :
These standards are those originally invented by a commercial organization as a basis for the operation of its products They called proprietary, because they are wholly owned by the company that invented them Also called Close standards These are developed by the groups or committees that have passed them into public domain Also called open standards
De-jure (By law)
Standards, that have been legislated by an officially recognized body
Standards … Advantages and Important aspects of Standards Standards enable competition Specially if the standards are Proprietary Standards make the interconnection of systems from different vendors possible Standards make users and network operators vendor independent
International services can available easily
International standards are threats to the local industries for large countries but opportunities to the industries of small countries
Standards … Examples of international standardizations Screw thread pitches (ISO, 1960’s) International telephone numbering Frequencies used for satellite and other radio communications Connectors and signals for PC, printer and modem interfaces Cellular telephone systems
Standards … Interested Parties Equipment manufacturers Network Operators Service users Academic Experts Note: Example of Mobile system.
Standard Organization Standards are developed by cooperation among standards creation committees forums, and govt. regulatory agencies
ISO ITU-T ANSI IEEE EIA Internet Society (ISOC) and IETF
ISO International Standards Organization, or International Organization for Standards
Created in 1947 Entirely voluntary organization dedicated to world wide agreement on international standards in a variety of field It is active in developing cooperation in the realms of scientific, technological, and economic activity. In the field of Information Technology, which have resulted in the creation of the Open Systems Interconnection model for network communications
ITU-T International Telecommunications Union-Telecommunication Standards Sector ITU-T is an international standards organization related to the United Nations that develops standards for telecommunications
Two popular standards developed by ITU-T are
V series (V.32, V.33, V.42),
X series (X.25, X.400, X.500),
Define data transmission over phone lines Define data transmission, over public digital networks; email, ISDN
ITU-T is divided into study groups, each devoted to a different aspect of industry National Committees submit proposals to these study groups
If study group agrees, the proposal is ratified and becomes part of ITU-T standard, issued every four years.
ANSI American National Standards Institute
But completely non-profit corporation not affiliated with the U.S federal government However, all ANSI Activates are undertaken with the welfare of the United States and its citizens occupying primary importance
ANSI members include professional societies, industry associates, govt. & regularity bodies and consumer groups
ANSI submits proposals to ITU-T and is the designated voting member from the United States to the ISO National Committees submit proposals to these study groups
IEEE Institute for Electrical and Electronics Engineers
Largest professional engineering society in the world Its aims to advance theory, creativity, and product quality in the fields of electrical engineering, electronics, and radio as well as in al related branches of engineering
IEEE has a special committee for local area networks (LAN), out of which come Project 802(802.3, 802.4)
EIA Electronic Industries Association
Aligned with ANSI, non profit organization Devoted to the promotion of electronics manufacturing concerns
In the field of IT, the EIA has made significant continuations by defining physical connection interfaces and electronic signaling specifications for data communication In particular, EIA-232-D, EIA-449 and EIA-530 define serial transmission between two digital devices
Internet Society (ISOC) & IETF Internet Engineering Task Force
Internet Society (ISOC) & Internet Engineering Task Force are concerned with speeding the growth and evolution of Internet communications Internet Society (ISOC) concentrates on user issues, including enhancements to the TCP/IP protocol suite. IETF is the standards body for the Internet itself.
Reviews Internet Software and Hardware
Important contributions include the development of Simple Network Management Protocol (SNMP), and review the performance standards for bridges, routers and router protocols
Bandwidth Utilization: Multiplexing and Spreading
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Bandwidth utilization is the wise use of available bandwidth to achieve specific goals. Efficiency can be achieved by multiplexing; privacy and anti-jamming can be achieved by spreading.
What is it all about?
Consider an audioconference where
if one person speaks, all can hear if more than one person speaks at the same time, both voices are garbled How should participants coordinate actions so that the number of messages exchanged per second is maximized time spent waiting for a chance to speak is minimized This is the multiple access problem
Some simple solutions
Use a moderator
Distributed solution
a speaker must wait for moderator to call on him or her, even if no one else wants to speak what if the moderator’s connection breaks? speak if no one else is speaking but if two speakers are waiting for a third to finish, guarantee collision
Designing good schemes is surprisingly hard!
MULTIPLEXING Whenever the bandwidth of a medium linking two devices is greater than the bandwidth needs of the devices, the link can be shared. Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link. As data and telecommunications use increases, so does traffic. Channel: Portion of a link that carries a transmission
Topics discussed in this section: Frequency-Division Multiplexing Wavelength-Division Multiplexing Synchronous Time-Division Multiplexing Statistical Time-Division Multiplexing
Dividing a link into channels
Categories of multiplexing
Multiplexing
Analog
FDM
Digital
WDM
TDM
Frequency-division multiplexing
FDM implementation FDM is an analog multiplexing technique that combines analog signals.
Either of following two conditions can lead to the unsuccessful recovery of the original signals
Channel must be separated by strips of unused bandwidth (guard band) to prevent signals from overlapping Carrier frequencies must not interfere with the original data frequencies
FDM process
FDM de-multiplexing example
Example Assume that a voice channel occupies a bandwidth of 4 kHz. We need to combine three voice channels into a link with a bandwidth of 12 kHz, from 20 to 32 kHz. Show the configuration, using the frequency domain. Assume there are no guard bands. Solution We shift (modulate) each of the three voice channels to a different bandwidth, as shown in. We use the 20- to 24kHz bandwidth for the first channel, the 24- to 28-kHz bandwidth for the second channel, and the 28- to 32-kHz bandwidth for the third one. Then we combine them as shown in Figure.
Example
Example
Five channels, each with a 100-kHz bandwidth, are to be multiplexed together. What is the minimum bandwidth of the link if there is a need for a guard band of 10 kHz between the channels to prevent interference? Solution For five channels, we need at least four guard bands. This means that the required bandwidth is at least 5 × 100 + 4 × 10 = 540 kHz, as shown in Figure.
Example
Analog hierarchy
FDMA
AMPS (analog), the First, Generation (1G) used 30 KHz for each user. Pros
Very Simple to design Synchronization is easy No interference among users in a cell
Cons
Narrowband interference Static spectrum allocation Freq. reuse is a problem High Q analog filters or large guard band required
Note
WDM is an analog multiplexing technique to combine optical signals.
Wavelength-division multiplexing
WDM
One may wonder about the mechanism of WDM as technology is very complex, but the idea is very simple. We have to combine multiple light sources into one single light at the multiplexer and do the reverse at de-multiplexer This combining and splitting of light sources are easily handled by a prism.
As a prism bends a beam of light based on the angle of incidence and the frequency
Prisms in wavelength-division multiplexing and de-multiplexing
TDM
Note
TDM is a digital multiplexing technique for combining several low-rate channels into one high-rate one.
TDMA
Can also partition time: users take turns using the channel 2G used same 30 KHz channels, but with three users sharing them (3 slots)
Pros
Better suited for digital Often gets higher capacity (3 times higher here) Relaxes need for high Q filters
• Cons
Strict synchronization and guard time needed Still susceptible to jamming, other-cell interference
Alternative to FDMA and TDMA?
What if we could allow users to share time and frequency?
Eliminates need for tight synchronization among many different users Eliminates need for expensive analog filters May have favorable impact on capacity (?) But: How do we separate the users? Won’t they interfere with each other?
CDMA (Code Division Multiple Access)
CDMA
All terminals send on the same frequency probably at the same time and can use the whole bandwidth of the transmission channel Each sender has a unique random number, the sender XORs the signal with this random number The receiver can “tune” into this signal if it knows the pseudo number Number, tuning is done via a correlation function Some second generation systems use CDMA Most of third generation systems use CDMA
CDMA
Advantages:
All terminals can use the same frequency, no planning needed Huge code space (e.g. 232) compared to frequency space Interferences (e.g. white noise) is not coded Forward error correction and encryption can be easily integrated
Disadvantages:
Higher complexity of a receiver (receiver cannot just listen into the medium and start receiving if there is a signal) All signals should have the same strength at a receiver
Figure Seven layers of the OSI model
Figure The interaction between layers in the OSI model
OSI Model
Seven layers belongs to 3 sub groups
Layer 1,2 and 3 are network support layers and they deal with the physical aspects of moving data from one device to another Layer 5,6 and 7 are user support layers, and they allow interoperability among unrelated S/W system Layer 4, transport layer, ensures end-to-end, reliable data transmission while layer 2, ensures reliable transmission on a single line
OSI Model … The upper OSI layers are almost implemented in S/W Lower Layers are combination of H/W and S/W , except of Physical layer which is implemented purely in H/W Lower layers always provide services to upper layers
OSI Model …
OSI Model … Physical
layer
It coordinates the functions required to transmit a bit stream over a physical medium Physical characteristics of interfaces and media Representations of bits Line configuration Physical topology
RJ45, Ethernet, Token Ring
OSI Model … Data
Link Layer
Responsible for node-to-node delivery Framing Physical Addressing (using MAC address) Flow control Error control (only detection but not correction) Access control
Frame Relay, PPP, IEEE 802.2, MAC, LLC
OSI Model … Network
Responsible for the source to destination delivery of a packet, possibly across multiple networks
Layer
Logical Addressing Routing
ICMP, BGP, OSPF
OSI Model … Transport
Layer
Responsible for end-to-end delivery of entire message, while network layer deal with individual packets and does not recognize any relation among them
Segmentation & Reassembly Connection control Error control
OSI Model … Session
Layer
Control sessions or logical connections
Dialog control (keep different applications data separate)
Simplex, half duplex, full duplex
Synchronization
Apple Talk, RPC, X-Windows
OSI Model … Presentation
Layer
It concerned with the Syntax & Semantics of information Translation Encryption Compression
MPEG, HTML, GIF
OSI Model … Application
Provide Human interface It enable the user to access the network
Layer
File transfer, access and management Mail services Directory services
FTP, SMTP, HTTP, Telnet, Web browser
Figure Summary of layers
FEDERAL URDU UNIVERSITY
Introduction to Telecommunication Ayaz Arshad
MS (Computer Networks & Communication)
Cell# 0333 6268096 E-mail:
[email protected]
What Telecommunications is ? To be able to communicate at a long distance. The process of transmitting receiving information over a distance by any electrical or electromagnetic medium (via electronic mean). Information may take the form of voice, video or dada.
What Telecommunications is ?
It includes mechanical communication and electrical communication because telecommunications has evolved from a mechanical to electrical form using increasingly more sophisticated electrical systems The main authorities involve in telecom are
Post Telegraph Telephone
What Telecommunications is ?
Here our main concern is electrical and bidirection communications The share of mechanical telecommunications such as conventional mail and press is expected to decrease Whereas electrical, especially bidirectional communication will increase an take the major share of telecommunications in the future
Significance of Telecommunications
Telecommunication networks make up the most complicated equipment in the world
More than 2 billion fixed an cellular telephones with universal access When any of these phones require a call, the telephone network is able to establish a connection to any other telephone in the world No other system in the world exceeds the complexity of telecommunications networks
Significance of Telecommunications
Telecommunications services have an essential impact on the development of a community
In developing countries, the tele-density (fixed), is few than 10 telephones per 1,000 inhabitants In developed countries there are around 500 to 600 fixed telephones per 1,000 inhabitants
The operations of modern community are highly dependent on telecommunications
Govt. organizations that provide public services are as dependent on telecommunications services as are private organizations
Significance of Telecommunications
Telecommunications plays an essential role on many areas of every living
Every day life is dependent on telecom Banking, automatic teller machines, tele-banking Booking of tickets Sales, wholesale and order handling Credit card payments at gasoline stations Booking of hotel rooms by travel agencies Govt. operations, such as taxations
Basic Components of a Communication Network
Encoder
Transmitter
Comm.
Receiver
Decoder
Medium Information
Information
Some of the Factors involved Nature of Information Format of Information Transmission Speed Transmission Medium Transmission Distance Modulation technique Error Control
Telecommunication Networks include Public Switched Telephone Network Data Communication Network Radio Television Fiber Internet
Communications ‘Discussion
The transmission of data from one computer to another, or from one device to another. A communications device, therefore, is any machine that assists data transmission. For example, modems, cables, and ports are all communications devices. Communications software refers to programs that make it possible to transmit data. In human speech, the sender transmits a signal through the transmission medium of the air In telecommunications, the sender transmits a signal through the transmission medium of a cable
Telecommunications
Telecommunications
The electronic transmission of signals for communications, including such means as: Telephone Radio Television
Telecommunication medium
Anything that carries an electronic signal and interfaces between a sending device and a receiving device
Telecommunications
Telecommunications
Communication Media
Types of Media
Twisted pair wire cable
Insulated pairs of wires historically used in telephone service and to connect computer devices
Coaxial cable
Consists of an inner conductor wire surrounded by insulation, called the dielectric The dielectric is surrounded by a conductive shield, which is surrounded by a non-conductive jacket. Coaxial cable has better data transmission rate than twisted pair
Twister Pair
Twisted-pair ‘Discussion’ A type of cable that consists of two independently insulated wires twisted around one another. One wire carries the signal while the other wire is grounded and absorbs signal interference. Twisted-pair cable is used by older telephone networks and is the least expensive type of local-area network (LAN) cable. Other types of cables used for LANs include coaxial cables and fiber optic cables.
Coaxial Cable ‘Discussion’ A type of wire that consists of a centre wire surrounded by insulation and then a grounded shield of braided wire. The shield minimizes electrical and radio frequency interference. Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks. Although more expensive than standard telephone wire, it is much less susceptible to interference and can carry much more data. Because the cable television industry has already connected millions of homes with coaxial cable, many analysts believe that they are the best positioned to capitalize on the much-heralded information highway.
Optical Fibers Fibers of glass Usually 120 micrometers in diameter Used to carry signals in the form of light over distances up to 50 km. No repeaters needed.
Optical Fibers …
Core – thin glass center of the fiber where light travels. Cladding – outer optical material surrounding the core Buffer Coating – plastic coating that protects the fiber. 1980s – OF technology becomes backbone of long distance telephone networks
Advantages of Optical Fibre Capacity: much wider bandwidth (10 GHz) smaller size and lighter weight Longer lasting (unproven) Less Signal Degradation& Digital Signals Crosstalk immunity Signal security
The light from optical fibers does not radiate significantly
Areas of Application Telecommunications Local Area Networks Cable TV CCTV Optical Fiber Sensors
Type of Fibers (Single-mode)
If the fiber core is very narrow compared to the wavelength of the light in use then the light cannot travel in different modes and thus the fiber is call “single-mode”.
The core diameter is typically between 8 and 9μm
less costly operates over a greater temperature range longer operational life
Type of Fibers (Multi-mode) … Inside a multimode fiber, there is a finite number of possible paths for the light to take. These paths are called modes. The number of possible paths depends on the diameter of the core.
For a fiber with a core diameter of 62.5nm using light of wavelength 1300nm, the number of modes is around 400.
Type of Fibers (Multi-mode) …
The problem with multimode operation is that some of the paths taken by particular modes are longer than other paths. This means that light will arrive at different times. Therefore the pulse tends to disperse as it travel through the fiber.
Type of Fibers
Type of Fibers
Total Internal Reflection in Fiber
Optical Fiber Link Input Signal
Transmitter Coder or Light Converter Source
Source-to-Fiber Interface
Fiber-optic Cable
Fiber-to-light Interface
Light Detector Receiver
Amplifier/Shaper Decoder
Output
Disadvantages Higher initial cost in installation Interfacing cost Difficult to repair/maintain Fragility
Tools: Specialized and sophisticated
Attenuation Impurities in the glass can absorb light but the glass itself does not absorb light Variations in the uniformity of the glass cause scattering of light
Types of Media (Unguided) Guided to unguided Transmission
Reception
the signal is guided to an antenna via a guided medium antenna radiates electromagnetic energy into the medium antenna picks up electromagnetic waves from the surrounding medium.
Example
a voice signal from a telephone network is guided via a twisted pair to a base station of mobile telephone network the antennas of the base station radiates electromagnetic energy into the air the antenna of the mobile phone handset picks up electromagnetic waves
Directional and Omni-directional Directional Signal radiates in a single direction the transmitting antenna puts out a focused electromagnetic beam the transmitting and receiving antennas must be aligned Example Satellite communication systems For a satellite located at 35784km above the ground, a 1° beam covers 1962km2
Directional and Omni-directional Omni-directional
Signal radiates in all directions The transmitted signal spreads out in all directions and can be received by many antennas. In general, the higher the frequency of a signal, the more it is possible to focus it into a directional beam Inexpensive antenna Example
mobile communication systems radio broadcasting
Types of Media (Unguided) Microwave
Frequencies in the range of about 30 MHz to 40 GHz are referred to as microwave frequencies 2 GHz to 40 GHz
highly directional beams are possible suitable for point-to-point transmission
30 MHz to 1 GHz
suitable for omni-directional applications
Types of Media (Unguided) Microwave
Line-of-sight devices which must be placed in relatively high locations The distance covered depend on the height of antenna To avoid possible obstructions, microwave antennas often are positioned on the tops of buildings, towers, or mountains. Microwave usage
Information is converted to a microwave signal, sent through the air to a receiver, and recovered
Types of Media (Unguided)
Unlike radio waves, microwaves typically do not pass through solid objects Some Waves can be refracted due to atmospheric conditions and may take longer to arrive than direct waves. These delayed waves can arrive out of phase with the direct wave, causing destructive interference and corrupting the received signal
This effect is called multi-path fading
Types of Media (Unguided) Advantages of Microwave over Fiber Optics
No need to lay cables:
This causes less disruption to the areas where the microwave transmitters and receivers are placed This also means that microwave communication is less expensive than fiber optic cable
Microwave Communications
Satellite Communications
(History)
First ever satellite – SPUTNIK I – in October 1957. First experimental satellite in 1963. First commercial satellite was launched in 1965. Over 250 satellites launched into space for different purposes. Over 800 satellites are launched into space to date for meteorological, defense, remote sensing and geological exploration purposes.
How Communication Occurs? Signals used are Microwaves. Earth stations transmit a signal to a satellite in orbit – UPLINK. Satellites receive this uplink signal, amplify it, shift it to a lower frequency, coupled with satellite antenna and focused into a narrow beam to send back to earth stations – DOWNLINK. 0.25 SEC delay occurs in either direction.
How Communication Occurs?
Satellite transmission
Satellite transmission
The satellite should be geosynchronous Its much like line-of-sight microwave transmission in which one of the station is a satellite and orbiting the earth When using a satellite for long distance communications, the satellite acts as a repeater. An earth station transmits the signal up to the satellite (uplink), which in turn retransmits it to the receiving earth station (downlink). Different frequencies are used for uplink/downlink. Rain is the main cause of atmospheric attenuation (hail, ice and snow have little effect on attenuation because of their low water content).
Satellite transmission
FOOTPRINT
Huge Geographical Area of the Earth.
Space Assets (Satellite)
Source: Union of Concerned Scientists [www.ucsusa.org]
Satellite Missions
Source: Union of Concerned Scientists [www.ucsusa.org]
Satellite Orbits
Source: Federation of American Scientists [www.fas.org]
Geosynchronous Orbit (GEO): 36,000 km above Earth, includes commercial and military communications satellites, satellites providing early warning of ballistic missile launch. Medium Earth Orbit (MEO): includes navigation satellites (GPS, Galileo, Glonass). Low Earth Orbit (LEO): from 80 to 2000 km above Earth, includes military intelligence satellites, weather satellites.
Satellite Orbits
Source: Union of Concerned Scientists [www.ucsusa.org]
GEOs
3 satellites can cover the whole earth. Orbital height above the earth about 23000 miles/35000km This orbit distance means that the satellite is orbiting the earth as fast as the earth is rotating.
It appears to earth stations that the satellite is stationary, thus making communications more reliable and predictable.
Earth stations is less expensive because
they can use fixed antennas.
GEOs (2)
GEO satellites require more power for communications The signal to noise ratio for GEOs is worse because of the distances involved Note that polar regions cannot be “seen” by GEOs Since they appear stationary, GEOs do not require tracking Round trip time to satellite about 0.24 seconds
GEOs are good for broadcasting to wide areas
MEOs Non-geostationary Orbits, higher than LEOs and lower than GEOs Plans to substitute GEOs with a set of 6-8 MEOs (60°) which can see the full Earth (incl. the Polar region) instead of a combination of GEO and LEO
more complex algorithms, but better view
Mainly used by GPS
LEOs Low earth orbit satellites - say between 100 - 1500 miles ( h<=1000 km) Signal to noise should be better with LEOs Shorter delays - between 1 - 10 ms typical Because LEOs move relative to the earth, they require tracking
LEOs
Television distribution
Direct broadcast satellite
long-distance telephone transmission
video signals are transmitted directly to the home user
suffers from transmission delay
private business networks
Advantages of Satellite
Low maintenance Emergency event-driven capability Ideal for remote locations Data easily shared. Very reliable data transmissions as system is supported governmental agencies Available for environmental or homeland security monitoring applications. (ENVIrinmental SATellite, very reliable)
Major problems for satellites high initial cost Positioning in orbit propagation delay Power Alignment (about solar power and antenna ) Harsh environment
susceptible to noise and interference
Broadcast Radio (Omni-directional) Applications
AM broadcasting
operating frequencies MF (medium frequency): 300 kHz - 3 MHz HF (high frequency): 3 MHz - 30 MHz
HF is the most economic means of low information rate transmission over long distances (e.g. > 300km)
Broadcast Radio (Omni-directional) Applications
FM broadcasting
operating frequencies
VHF (very high frequency): 30 MHz - 300 MHz
TV broadcasting
operating frequencies: VHF UHF (ultra high frequency): 300 MHz - 3000MHz
Infrared The name means "below red" (from the Latin infra, "below"), Line of sight (or reflection) Short wavelength Does not penetrate walls
no security or interference problems
no frequency allocation issue
no licensing is required
Infrared Q: WHAT IS INFRARED BUILDING SCIENCE? Ans: It’s the application of infrared thermographic inspection techniques as a powerful & noninvasive means of monitoring & diagnosing the condition of a building.
Infrared USES FOR INFRARED TV remote control Moisture Detection Mold Detection (Condition conducive for mold growth) Water Leak Detection Moisture behind Exterior Building Maintenance
History of Telecommunication and Data Networks
HISTORY
1830's Gauss and Weber develop a small scale telegraph system (tele=distant, graph=writing) in Gottingen 1844 Morse sets up 40-mile telegraph line between Washington, DC, and Baltimore 1876 Alexander Graham Bell and Thomas A. Watson demonstrate and patent the telephone (tele=distant, phone=voice). 1878 Bell forms the Bell Telephone Company and establishes 1st switching office in New Haven 1896 Guglielmo Marconi develops the first wireless telegraph system 1926 First public crossbar switch exchange opened in Sweden
HISTORY
1927 First commercial radio telephone service operated between Britain and the US 1939 Pulse code modulation (PCM) invented, which later became the basis for digitized voice transmission 1940's First practical crossbar exchanges become popular in the US 1946 First car-based mobile telephone set up in St. Louis, 1946 The L1-carrier system installed to support 1800 telephone circuits using frequency division multiplexing over 3 pairs of coax cables 1948 Claude Shannon publishes two benchmark papers on Information Theory, containing the basis for data compression (source encoding) and error detection and correction (channel encoding) 1950 TD-2, the first terrestrial microwave telecommunication system, installed to support 2400 telephone circuits
HISTORY
1960's Early in the decade, the Improved Mobile Telephone System (IMTS) developed with simultaneous transmit & receive, more channels, and greater power 1960's Early in the decade, AT&T introduced a 2400-bps modem (Bell 201)using 4-phase phase-shift keying (PSK) modulation 1962 The first communication satellite, Telstar, launched into orbit 1963 The American Standard Code for Information Exchange (ASCII) developed for encoding alpha-numeric and control characters into 7-bit binary strings 1964 The International Telecommunications Satellite Consortium (INTELSAT) established, and in 1965 launches the Early Bird geostationary satellite
HISTORY
1970 First low-loss optical fiber announced having an attenuation of 20 dB/km 1970's Packet switching emerges as an efficient means of data communications, 1976 Ethernet invented by Robert Metcalf, leading to 1-Mbps to 10-Mbps Ethernet local area networks (LANs) based on the IEEE 802.3 standard 1977 The Advanced Mobile Phone System (AMPS), invented by Bell Labs, first installed in the US with geographic regions divided into "cells" (i.e., cellular telephone) 1983 January 1, TCP/IP selected as the official protocol for the ARPANET, leading to rapid growth
HISTORY
1980's Late in the decade, Local Area Networks (LANs) emerge as an effective way to transfer data between a group of local computers 1980's Late in the decade, AT&T replaces all its analog multiplexing with digital multiplexing. MCI followed in the early 1990's 1992 One-millionth host connected to the Internet, with the size now approximately doubling every year 1993 Internet Protocol version 4 (IPv4) established for reliable transmission over the internet in conjunction with the Transport Control Protocol (TCP)
HISTORY
1993 Asymmetric Digital Subscriber Lines (ADSL) standardized using the discrete multitone technique to allow greater services 1998 Sprint Corp announces it will offer an advanced packetswitching network to simultaneously send voice, data, and video down a single phone line 1998 Ericsson, IBM, Intel, Nokia, and Toshiba announce they will join to develop Bluetooth for wireless data exchange between handheld computers or cellular phones and stationary computers
Internet Telephony (VoIP)
Overview
Voice Calls are transmitted over Packet Switched Network instead of Public Switched Telephone Networks (PSTN) Modes of Operation: - PC to PC - PC to Telephone - Telephone to PC - Telephone to Telephone
VoIP Architecture
Advantages
Cost ( talk like PSTN and pay like Internet) Can call and talk with many at the same time, unlike PSTN. Exchange of additional data: Audio and video conferences shared applications Unified messaging telephony, e-mail, sms, chat, ... Mobility Universal reach-ability
Disadvantages
QoS Power Outages and failure. Can handle this issue by installing UPS Emergency call (like 15, 911) Sometime Software or Hardware dependent
Overview
New Internet services: “telephone”, “radio”, “television” Components needed:
Audio coding Data transport (RTP, RTCP)
Codec's Signaling (SIP, H.323, IAX2)
Quality of service – resource reservation PSTN inter-working: gateway location, number translation
Why VoIP?
Voice traffic will be in near future a small fraction of total telecom traffic moved around the world Network operators are building high-capacity packet switched infrastructure. Operational Improvement
Business Tool Integration
Common network infrastructure Simplification of Routing Administration Voice mail, email and fax mail integration Web + Call Mobility using IP
New Services
New Integrated Applications
Network Growth
Applications
Real Time
Interactive (Two way) Telephony Streaming (One way) Radio-TV broadcast (Consumed Live) Recording (One way) Replay (Stored at the receiver)
Not Real Time
Short Transfers (e-mail) Long Transfers (large image retrieval)
Components of VoIP
Coding & Decoding of Analog Voice
Signaling
Call setup & tear down Resource & coding negotiation
Transport of Bearer Traffic
Analog-to-Digital and Digital-to-Analog conversions Compression
Voice packet transmission Routing Support of quality of service
Numbering
Phone number, IP address
VoIP Data Transport
Candidate Internet transport protocols:
TCP:
UDP:
connection-oriented, reliable (acknowledgements/ resending) problem: resending causes additional delay connectionless, unreliable problem: no sequence numbers, no timestamps
Both are not appropriate RTP/RTCP (on top of UDP)
What Protocols are Required?
Signaling Protocol: To establish presence,
Media Transport Protocols: To transmit
locate user, set up, modify and tear down sessions. packetized audio/video signal.
Supporting Protocols: Gateway Location,
QoS, AAA, Address Translation, etc.
AAA (Authentication, Authorization, Accounting )
VoIP Protocols
H.323:
SIP:
ITU-T standard, Peer-to-peer protocol that supports terminals communicating over packet based networks IETF standard, RFC 3261 Peer-to-peer protocol for initiation, modification termination of communication sessions between users
MGCP:
ITU-T and IETF collaboration, RFC 3435 Master/slave protocol for media gateway controller to control media gateway
VoIP Protocol Stacks
H.323
Recommendation published by ITU-T framework for multimedia communication Peer-to-peer protocol that supports terminals communicating over packet based networks 2003: Version 5 H.323 includes
Call signaling Media control Audio coding Video coding Data sharing Media transport
H.225 H.245 G.711, G.722, G.723, G.728, G.729 H.261, H263 T.120 RTP, RTCP
Powerful for video-conferencing Bulky, complex Widely deployed
Components Defined in H.323
H.323 defines four major components for a packet network based multimedia communication H.323 Terminal: Client end points that provides real-time communications with other H.323 entities. Functions performed include (1) signaling and control, (2) real-time communications Gateway: Provides the connection path between the packet switched network and the switched circuit network. Gatekeeper: Performs address translation, admission control, bandwidth control, zone management, call control signaling, call authorization, bandwidth management, call management. Multipoint control unit (MCU): Supports conferencing between three or more endpoints. MCU consists of multipoint controller (MC) and multipoint processor (MP). The collection of all terminals, gateways, and MCUs managed by a single gatekeeper is called a zone.
Session Initiation Protocol (SIP)
Developed by IETF since 1999 , RFC 3261 SIP is an application-layer control (signalling) protocol for creating, modifying and terminating sessions with one or more participants Target: develop simpler and more modular protocol for VoIP than the large and complex H.323 by ITU SIP is a text-based protocol similar to HTTP and SMTP, for initiating interactive communication sessions between users
Session Initiation Protocol (SIP)
Not only for VoIP, but in general for multimedia communication Sessions include Internet Multimedia conferences, Internet Telephone calls and Multimedia distribution SIP can be used with different transport protocols, it doesn't even require reliable transport protocols A simple SIP client can be implemented using only UDP Users may use different devices ASCII protocol like SMTP and HTTP Format similar to HTTP
Comparison of H.323 and SIP Item Designed by
H.323 ITU
SIP IETF
Compatibility with PSTN Yes
Largely
Completeness
Full protocol stack
SIP just handles setup
Parameter negotiation
Yes
Yes
Call signaling
over TCP
SIP over TCP or UDP
Message format
Binary
ASCII
Media Transport
RTP/RTCP
RTP/RTCP
Comparison of H.323 and SIP Item
H.323
SIP
Multiparty calls
Yes
Yes
Multimedia conferences
Yes
No
Instant messaging
No
Yes
Encryption
Yes
Yes
Implementation
Large and complex
Moderate
Status
Widely deployed
Up and coming
RTP
Realtime Transport Protocol (July 2003) Provides end-to-end delivery services for data with real-time characteristics (audio and video) Mostly over UDP Supports multicast & unicast Application layer protocol for transmitting real-time data (audio, video, ...) Includes payload type identification, sequence numbering, time stamping, delivery monitoring Its next version is RTP Control Protocol (RTCP) Also a version named by Secure RTP (SRTP)
RTP (Drawbacks)
Does not provide any mechanism to ensure timely delivery or provide other quality-ofservice guarantees No guarantee of delivery Cant prevent out-of-order delivery Assume that the underlying network is reliable and delivers packets in sequence
RTP and RTCP
Both protocols use UDP:
Port numbers:
Session Description Protocol (SDP)
To convey information about the session to the destination Description includes:
Media to be transmitted (e.g., A/V, codec, sampling rate)
Media destination (IP address and port number)
Session name and purpose Times the session is active Contact information
Protocol Family
QoS Considerations for Quality Five components affect the voice quality: Codec used
Packet Loss
End-to-end delay must be <150 milliseconds
Jitter (Variations in packet Arrival time)
Voice can tolerate some packet loss (<10-3), Use packet loss concealment to improve quality
Packet Transfer Delay
Different codec's use different compression algorithms
Too much jitter degrades voice quality Use jitter buffer
Out-of-order delivery Echo
VoIP QoS Measurement
Traditional measure of user perception:
Mean Opinion Score (MOS) from 1 (poor) to 5 (excellent), An expert panel listens the voice samples and scores the quality of the voice MOS=4 is toll quality
ITU-T G.107 presents a mathematical model, known as E-model, to predict QoS (as R value) based on objective impairment measurements.
QoS…
End-to-end delay ≤150 msec to be satisfactory (ITUT G.114#) Reasons for End-to-end delay
Packetization delay Coding delay Sending delay (n times) Propagation delay (n times) Queuing delay (n times) Buffering delay Decoding delay
Source of fix delays
QoS …
Packet loss:
Rare packet loss can be tolerated (no lower qos) Can be compensated by TCP, e.g. But retransmission adds significant delay TCP is not used, but UDP
Out-of-order delivery:
compensated by sequence numbering (RTP)
QoS (Delay Examples)
QoS (Latency)
Components: Encoding, Packetization, Network delay, Receiver buffering, Decoding
QoS …
Conclusions: Moderate delay: no lower qos Moderate jitter: compensated by playout buffering Moderate packet loss: no lower qos Out-of-order delivery: compensated by sequence numbering
Voice Codec
MOS (Mean Opinion Score)
Summery of voice Quaility
Bandwidth Required
Depends on codec used, packetization delay, and protocol overhead Packetization delay: Time required to collect voice in the packet payload Packet overhead: RTP, UDP, IP Layer 2 overhead:
ATM Frame Relay Ethernet PPP
Bandwidth required:
(overall length in bits)/ (packetization delay)
Comparison PSTN and VoIP Item
PSTN
VoIP
coding / decoding
PCM
PCM and other codec’s?
multiplexing / switching
TDM and circuit switching (QoS guaranteed)
packet switching (QoS guarantee?)
data transport
B channel
Transport protocol?
addressing
telephone numbers
VoIP addressing?
The phone works – why bother with VoIP user perspective
carrier perspective
variable compression: tin can to broadcast quality no need for dedicated lines
better codecs + silence suppression – packet header overhead = maybe reduced bandwidth
security through encryption
shared facilities simplify management, redundancy
caller & talker identification
advanced services
better user interface (more than 12 keys, cheaper bit switching visual feedback, semantic rather than stimulus) no local access fees (but dropping to 1c/min for PSTN) adding video, application sharing is easy
fax as data rather than voiceband data (14.4 kb/s)
THINK OF INTERNET There are three possible ways to access internet. Broadband access Uses DSL or cable modem at home and T1 or T3 line at office WIFI Uses WIFI routers at home and hotspots on the road Dial Up Connection
NEW TECHNOLOGY Broadband access is too expensive and WiFi coverage is very sparse. The new technology promises High speed of broadband service Wireless rather than wired access Broad Coverage
What is WIMAX? WIMAX stands for Worldwide Interoperability for Microwave Access WiMAX refers to broadband wireless networks that are based on the IEEE 802.16 standard, which ensures compatibility and interoperability between broadband wireless access equipment WiMAX, which will have a range of up to 31 miles, is primarily aimed at making broadband network access widely available without the expense of stringing wires (as in cable-access broadband) or the distance limitations of Digital Subscriber Line.
A WIMAX system consists of 1)
A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area as big as 3,000 square miles (~8,000 square km).
2) A
WiMAX receiver - The receiver and antenna could be a small box or Personal Computer Memory card, or they could be built into a laptop the way WiFi access is today
WIMAX TOWER
WIMAX RECEIVER
MODES OF OPERATION Line of sight Uses a higher frequency range
Non-Line of sight Uses a lower frequency range.
HOW WIMAX works?
WIMAX Scenario Consider a scenario where a WiMax-enabled computer is 10 miles away from the WiMax base station. A special encryption code is given to computer to gain access to base station The base station would beam data from the Internet required for computer (at speeds potentially higher than today's cable modems)
WIMAX Scenario The user would pay the provider monthly fee for using the service. The cost for this service could be much lower than current high-speed Internet-subscription fees because the provider never had to run cables The WiMAX protocol is designed to accommodate several different methods of data transmission, one of which is Voice Over Internet Protocol (VoIP) If WiMAX-compatible computers become very common, the use of VoIP could increase dramatically. Almost anyone with a laptop could make VoIP calls
IEEE 802.16 Range- 30 miles from base station Speed- 70 Megabits per second Frequency bands- 2 to 11 GHz and 10 to 66 GHz(licensed and unlicensed bands respectively) Defines both MAC and PHY layer and allows multiple PHY layer specifications
IEEE 802.16 Specifications
802.16a Uses the licensed frequencies from 2 to 11 GHz Supports Mesh network 802.16b Increase spectrum to 5 and 6 GHz Provides QoS( for real time voice and video service) 802.16c Represents a 10 to 66GHz 802.16d Improvement and fixes for 802.16a 802.16e Addresses on Mobile Enable high-speed signal handoffs necessary for communications with users moving at vehicular speeds
802.16 Architecture
IEEE 802.16 Protocol Architecture has 4 layers: Convergence, MAC, Transmission and physical, which can be mapped to two OSI lowest layers: physical and data link.
FEATURES OF WIMAX Scalability Quality of Service Range Coverage
Scalability The 802.16 standard supports flexible radio frequency (RF) channel bandwidths. The standard supports hundreds or even thousands of users within one RF channel As the number of subscribers grow the spectrum can be reallocated with process of sectoring.
Quality of Service Primary purpose of QoS feature is to define transmission ordering and scheduling on the air interface These features often need to work in conjunction with mechanisms beyond the air interface in order to provide end to end QoS or to police the behaviour or SS.
Requirements for QoS A configuration and registration function to pre configure SS based QoS service flows and traffic parameters A signalling function for dynamically establishing QoS enabled service flows and traffic parameters Utilization of MAC scheduling and QoS traffic parameters for uplink service flows Utilization of QoS traffic parameters for downlink service flows
RANGE Optimized for up to 50 Km Designed to handle many users spread out over kilometres Designed to tolerate greater multipath delay spread (signal reflections) up to 10.0μ seconds PHY and MAC designed with multimile range in mind
Coverage Standard supports mesh network topology Optimized for outdoor NLOS performance Standard supports advanced antenna techniques
BENEFITS OF WIMAX Speed Faster than broadband service
Wireless Not having to lay cables reduces cost Easier to extend to suburban and rural areas
Broad Coverage Much wider coverage than WiFi hotspots
Benefits to Service Providers Allow service providers to deliver high throughput broadband based services like VoIP, high-speed Internet and Video Facilitate equipment compatibility Reduce the capital expenditures required for network expansion Provide improved performance and extended range
Benefits to Customers Range of technology and service level choices from both fixed and wireless broadband operators DSL-like services at DSL prices but with portability Rapidly declining fixed broadband prices No more DSL “installation” fees from incumbent
Why not WIFI Scalability Relative Performance Quality of Service Range Coverage Security
Scalability 802.11 •
•
Wide (20MHz) frequency channels
MAC designed to support 10’s of users
802.16a Channel bandwidths can be chosen by operator (e.g. for sectorization) • 1.5 MHz to 20 MHz width channels. MAC designed for scalability. independent of channel bandwidth •
•
MAC designed to support thousands of users.
RELATIVE PERFORMANCE Channel Bandwidth
Maximum Data Rate
Maximum bps/Hz
802.11
20 MHz
54 Mbps
2.7 bps/Hz
802.16a
1.5 – 20 MHz
100 Mbps
5.0 bps/Hz
Quality of Service 802.11 •
•
•
•
Contention-based MAC (CSMA/CA) => no guaranteed QoS Standard cannot currently guarantee latency for Voice, Video Standard does not allow for differentiated levels of service on a per-user basis
802.11e (proposed) QoS is prioritization only
802.16a •
•
•
•
Grant-request MAC
Designed to support Voice and Video from ground up Supports differentiated service levels: e.g. T1 for business customers; best effort for residential. Centrally-enforced QoS
Range 802.11
802.16a
•
Optimized for ~100 meters
•
•
No “near-far” compensation
•
•
•
Designed to handle indoor multipath delay spread of 0.8μseconds Optimization centers around PHY and MAC layer for 100m range
•
•
Optimized for up to 50 Km Designed to handle many users spread out over kilometers Designed to tolerate greater multi-path delay spread (signal reflections) up to 10.0μseconds PHY and MAC designed with multimile range in mind
Coverage 802.11 •
Optimized for indoor performance
802.16a •
• •
No mesh topology support within ratified standards •
Optimized for outdoor NLOS performance Standard supports mesh network topology Standard supports advanced antenna techniques
Security 802.11
•
•
Existing standard is WPA + WEP 802.11i in process of addressing security
802.16a
•
Existing standard is PKM - EAP
Advantages of WiMax over 3G Using an assortment of proprietary and standards-based technologies, such as OFDM and W-CDMA ,WiMax has a clear advantage over 3G The advantages include Higher Throughput Low Cost Lower Latency
Advantages of WiMax over 3G
Advantages of WiMax over 3G WiMax spectrum is more economical than 3G. The price paid per Hz is as much as 1000 times lower than for 3G spectrum The low cost is a clear driver for service providers to enter the field of wireless services with WiMax
FUTURE WiMax will be deployed in three stages In the first phase WiMaX technology (based on IEEE 802.16-2004) provides fixed wireless connections In the second phase WiMaX will be available as a cheap and self-installing Subscriber Terminal (ST), linked to PC and to antenna The third phase enables portability, thus WiMAX (based on IEEE 802.16e) will be integrated into commercial laptops
Promises
The WIMAX Forum Founded in April 2001 No Profit organization comprised of wireless access system manufacturers, component suppliers, software developers and carriers A wireless industry consortium that supports and promotes WiMAX’s commercial usage Comply with the WiMAX standard and focus on the interoperability Members include Intel, AT&T, Siemens Mobile, British Telecommunications, etc
References www.ewh.ieee.org/r4/chicago/Yu-WiMAX.pdf http://computer.howstuffworks.com/wimax.htm www.wimaxforum.org http://standards.ieee.org/catalog/olis/lanman.html