SkyEdge I I Inbound Overview
Agenda IB Carrier Introduction Configuration Parameters Carrier Types Time Frequency Plan (TFP) DVB-RCS Benefits Slot Types Capacity Requests ICM IB Adaptivity
Agenda IB Carrier Introduction Configuration Parameters Carrier Types Time Frequency Plan (TFP) DVB-RCS Benefits Slot Types Capacity Requests ICM IB Adaptivity
Inbound DVB-RCS Introduction SkyEdge II Inbound Channel is based in DVB-RCS DVB -RCS (EN 301 790) Access Scheme based on dynamic dynamic MF-TDMA Multi-Frequency Time-Division Multiple Access The DVB-RCS standard defines Physical and Media Access Control (MAC) levels of the satellite segment (OSI layers 1 and 2).
Modulation and Coding Access Scheme Capacity Request Burst Formats Timing Synchronization Etc.
Inbound Channel Configuration Parameters Modulation Schemes QPSK 8PSK Coding Scheme Turbo Code MODCODs Available QPSK – QPSK – 1/2, 2/3, 3/4, 4/5, 6/7 8PSK – 8PSK – 2/3, 3/4, 4/5, 6/7 Es/No Dynamic range of 8.9 dB
Inbound Channel MODCOD Es/No Threshold
Mode Code
Es/No
QPSK 1/2
4.5
QPSK 2/3
5.9
QPSK 3/4
6.8
QPSK 4/5
7.1
QPSK 6/7
8.2
8PSK 2/3
10.7
8PSK 3/4
11.9
8PSK 4/5
12.7
8PSK 6/7
13.4
Dynamic Range 8.9 dB
Inbound Channel Configuration Parameters Symbol rates 128, 160, 192, 256, 320, 384, 512, 640, 832, 1024,1536, 2048, 2560 Ksps. Roll off factor 0.20 Inbound BW as low as 153.6KHz (BW = 128 Ksps x 1.20)
Amplitude
BW = Sym bo l Rate x (1 + Roll off Factor)
B W
Frequency
SEII Inbound Introduction The IB carries all the transmissions from the VSATs including:
User Traffic Initial Logon Capacity Requests (Allocations requests) Maintenance Information Offers a Reliable communication link: The MODCODs adaptation and reservation Access mechanisms permit no error correction (no retransmissions are needed) on the IB
The IB Is composed of one or more physical channels that includes one or more Carrier Types (CT)
Inbound Channel Carrier Type CT A Carrier Type (CT) is defined by its symbol rate and an arrangement of slot types in a time frame Up to four CTs can be configured per HSP Slot Type (ST) The ST Is defined by its MODCOD and relative bandwidth inside CT Several ST can be configures in a CT (up to 8 ST per HSP) Each HSP has its own Time and Frequency Plan (TFP)
Inbound Channel Carrier Type Example
Carrier Type
Symbol Rate
Amount of Channels
MODCOD
MODCOD composition percentage
A
128
1
QPSK 1/2
100%
B
160
1
QPSK 3/4
100%
C
256
2
QPSK 3/4
50%
8PSK 6/7
50%
Inbound Channel Carrier Type Example Freq
A
CT- C QPSK ¾
CT- C QPSK ¾
CT- B QPSK ¾
C T- A
QPSK ½
7 / 6 K S P 8
7 / 6 K S P 8
7 / 6 K S P 8
7 / 6 K S P 8
QPSK ¾
QPSK ½
QPSK ¾
QPSK ¾
QPSK ¾
7 / 6 K S P 8
7 / 6 K S P 8
7 / 6 K S P 8
7 / 6 K S P 8
QPSK ¾
QPSK ½
QPSK ¾
QPSK ¾
QPSK ¾
QPSK ½
7 / 6 K S P 8
7 / 6 K S P 8
7 / 6 K S P 8
7 / 6 K S P 8
QPSK ¾
QPSK ½
QPSK ¾
QPSK ¾
QPSK ¾
QPSK ½
C
C
Inbound Channel Time Frequency Plan (TFP) The TFP specifies the layout and usage of the Inbound Carriers on a constant period of time TFP includes
Frequency Plan - list of Carrier’s Center frequencies and Symbol Rates Time Plan - Carrier usage over a period of time (SuperFrame)
Stop Freq Q 1/2
Q 1/2
Q 1/2
Q 1/2
Q 1/2
Q 1/2
Q 1/2
Q 1/2
Q Q 6/7 6/ 7
Q 3/4
Q Q 6/7 6/ 7
Q 3/4
Q Q 6/ 7 6/7
Q 3/4
Start Freq Time
Time Frequency Plan (TFP) Time Structure TFP is constructed to have a full repetition of a SuperFrame every 360 ms Allocation is performed every 40ms and published to all the VSATs Each allocation round is independent. Each allocation round generates its own “allocation table” broadcasted to the network.
Freq
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
TRF
CSC
SYN
Superframe
CSC
SYN
CSC
SYN
CSC
SYN
CSC
SYN
Time 40 ms ec Allocation Round
360 ms ec SuperFrame
Time Frequency Plan (TFP) Time Slot Types The Time-Frequency Plan (TFP) is composed of 3 slot types: Logon Burst (CSC- Common Signaling Channel) slot Initial Logon Synchronization (SYNC) slot Maintenance (Es/No report about the OB) SAC (Satellite Access Control) field for capacity requests Traffic (TRF) slot User Data SAC field (capacity request as piggybacking)
Slots of different types on the same carrier are multiplexed in time in each CT
Stop Freq
TRF TRF S C Q 1/2 Q 1/2 TRF Q 1/2
Start Freq
TR F TRF Q Q 6/7 6/7
C S TRF Q 1/2 TRF Q 3/4
S
TRF TRF S TRF Q 1/2 Q 1/2 Q 1/2
S
TRF S TRF Q 1/2 Q 1/2
TRF TRF Q Q 6/7 6/7
TRF Q 3/4
TRF TRF Q Q 6/7 6/7
TRF Q 1/2 TRF Q 3/4
Time
Slot Types CSC - Logon Burst Slot Logon Burst (CSC) slot Carries VSAT initial network Logon It is used in contention; collisions may occur The recommended default is to have one CSC per VSAT with a 10 second interval (sizing spreadsheet) CSC MODCOD The CSC slots are located in the most robust CT using the most robust MODCOD If the most robust MODCOD uses 8PSK as the modulation scheme, then the system will define QPSK 6/7 as the MODCOD for the CSC slots
Slot Types CSC - Logon Burst Slot CSC Burst includes: Preamble for burst detection and CRC VSAT information VSAT initial identification (VSAT ID)
VSAT Capab.
VSAT ID
Rand. VSAT Capab.
Rand. VSAT ID
C S C B u r s t (16 bytes)
Slot Types Sync - Maintenance Slot Sync slots are used for: Time, frequency and power maintenance Initial capacity request Transfer information about the received Es/No readings
VSAT Capability Each logged on VSAT is allocated a Sync slot per second Sync MODCOD The Sync will be located at the most robust CT using the most robust MODCOD If most robust MODCOD uses 8PSK as the modulation scheme, then the system will define QPSK 6/7 as the MODCOD for the Sync slots
Slot Types Sync - Maintenance Slot SYNC burst includes Preamble for burst detection Satellite Access Control (SAC) for capacity requests. SYNC slot is 16 bytes
Slot Types TRF - Traffic Slot The TRF (Traffic) slot contains ATM cells that carry user data Each Backbone packet is encapsulated over the ATM cells by AAL5 (RFC 2684) Each TRF burst contains 1, 2 or 4 ATM cells. The default is 2. TRF burst consists of: Preamble for receiver detection SAC (Satellite Access Control) field Used for piggybacked capacity requests
2 ATM Cell Each ATM cell carries 48 user traffic bytes (out of a total of 53 bytes)
Slot Types TRF - Traffic Slot 600 Bytes
IP
618 Bytes
Backbone
618 Bytes 48
48
48
48
AAL5 Data
5
ATM
TRF Slot
Preamble
SA C
Padding
Trailer
48
A TM Cel l
A TM Cel l
Slot Types TRF - Traffic Slot
Guard Preamble – Used for burst detection and acquisition
SAC (Satellite Access Control) = 4 Bytes Used for piggy backed capacity requests ATM cell = 53 bytes (incl. 5 byte header)
ATM Cell
Guard
ATM Cell
FEC applied and FEC bits added after scrambling
TRF Burst
Gilat SEII IB Benefits Uses multiple MODCODS Supports robust slot for fade mitigation Supports more efficient slots to take advantage of better weather conditions Uses multiple Carrier Types Yields better satellite utilization Eliminates the need for additional carrier
DVB-RCS Tables Service Information (SI) Tables
SkyEdge II uses the DVB-S2 Outbound (forward link) to transmit all relevant SI tables to define: Satellite Position Time-Frequency plan for Inbound channels Frequency, power and time corrections VSAT logon slots allocation Individual VSAT parameters
Capacity/BW Allocation Etc.
Test Your Knowledge 1.
Name the slot types in the TFP___________________________________
2.
How many allocation cycles are in a SuperFrame?___________________
3.
Which type slots carries capacity requests? _____________________________
4.
How many CT can be configured per HSP?______________________________
5.
Calculate the required channel bandwidth for a carrier with symbol rate of 512 Ksps. ___________________________________________________________
6.
What is the user data size in each TRF? ________________________________
7.
How many MODCODs can be configured in a CT?________________________
8.
What is a CSC slot? _______________________________________________
9.
What is carried by the Sync slot? A._________________ B.__________________C._______________________
SkyEdge II Capacity Allocation Methods
Bandwidth Allocation Methods BW Allocation Methods
Req u es t / Pr i o r i ty
Rate
RBDC
C2P (VoIP)
(Rate Based Dynamic Capacity)
AC (Admission Control)
Un s o l i c it ed
ABS (Absolute) High/Medium/Low (Flywheel included here) Volume
VBDC
ABS (Absolute)
(Volume Based Dynamic Capacity)
(Free Capacity Distribution)
or AVBDC (Absolute Volume Based Dynamic Capacity)
FCD
High/Medium/Low
Rate Allocation Methods Rate Based Dynamic Capacity (RBDC) RBDC - Rate Based Capacity Request
Rate based capacity requests originated by the VSAT Granularity of 2Kbps A RBDC request is issued every 200 msec per priority The VSAT refreshes AC, Abs and H, M,L requests once per second
Full multi-frequency allocation (even across different CTs) Prioritization by IB QoS mechanisms C2P (VoIP) priority / AC (Admission Control) priority Abs (Absolute) priority High, Medium or Low flow priority Used for Managed Multimedia Application (VoIP, Video), Trunk Mode (for ABIS), CBR Applications and general non TCP traffic.
Rate Allocation Methods RBDC Priority Levels C2P (Connection Control Protocol) AC (Admission Control) priority Absolute, low jitter, low delay rate based requests Guaranteed bit rate allocation (explicit grant or reject) Minimum jitter capacity request by uniform allocations in the SuperFrame (not more than 10 ms difference) Highest priority in the system
Rate Allocation Methods RBDC Priority Levels Abs (Absolute) Priority
Guaranteed rate based allocation requests Priority used by the VSAT for allocation requests up to the CIR value High, Medium and Low priorities
Weighted fair sharing rate based priority requests Neither rate nor jitter guaranteed Priority used by the VSAT for allocations up to the MIR value Configurable on the DiffServ queues
Rate Allocation Methods RBDC Sources Requests Managed VoIP Applications
Use C2P requests Applications included in this criteria are detected and locally managed by the VSAT application layers Automatic SIP recognition
Rate Allocation Methods RBDC Sources Requests Trunk Traffic (SkyAbis Solution)
Use AC RBDC allocation request Abis traffic is dynamically measured for required satellite demand and low jitter Trunk Mode parameter should be enabled and specific configuration is required in the VSAT
Rate Allocation Methods RBDC Sources Requests CBR (Constant Bit Rate)
Allocates a fixed CBR to the VSATs Used for any application that requires strict CBR Uses an Absolute RBDC allocation request Must be preconfigured on the VSAT
Requested immediately after logon
Rate Allocation Methods RBDC Sources Requests Non TCP traffic
Used for Raw-IP and any UDP applications (TFTP, file-sharing, ICMP, etc.) Up to CIR, use Abs RBDC allocation request After CIR reached, use Low, Medium or High RBDC request The HSP allocated BW according need and overall network demand It is configurable by DiffServ VSAT queue configuration
Rate Allocation Methods Traffic Sense Flywheel Flywheel Mechanism
One of the heuristics mechanism employed in SEII It is a rate based allocation mechanism that shortens response time The mechanism is based on the assumption that an active VSAT will soon need to transmit more traffic even if its DRPP queues are currently empty When any traffic that passes through the VSAT, the flywheel mechanism will be set for three seconds (but not before the DRPP queues are empty) The three seconds are hard coded The flywheel request is configurable in the VSAT by 2 Kbps steps Flywheel may be totally disabled Flywheel uses a Low RBDC request
Volume Allocation Methods Volume Based Dynamic Capacity (VBDC) VBDC Volume Based Dynamic Capacity
It is a volume based capacity allocation dynamically requested by the VSAT The VBDC request is issued every 100 msec for the total amount of traffic which accumulated since last VBDC (only the newly added traffic) Prioritization by IB QoS mechanisms A b s (A b s o l u t e ) p r i o r i t y L o w , M ed i u m o r H i g h p r i o r i t y
It is used for TCP type Traffic AVBDC Absolute Volume Based Dynamic Capacity requests This is a “health mechanism” used for recovery This request type overwrite and replaces all previous VBDC requests AVBDC is sent after timeout interval during which none of the VSAT’s VBDC requests were not allocated
Rate Allocation Methods VBDC Sources Requests TCP Traffic
FTP, HTTP, Telnet, POP3, SMTP, etc. Up to CIR, use Abs VBDC/ AVBDC allocation requests After CIR is reached, use Low, Medium or High VBDC/AVBDC requests The HSP allocated BW according need and overall network demand It is configurable by DiffServ VSAT queue configuration
Free Capacity Distribution (FCD) FCD - Free Capacity Distribution Mechanism
One of the heuristics mechanism employed in SEII It is a unsolicited volume based capacity allocation that assigns the unused capacity The mechanism is based on the assumption that some unused capacity can remain after all pending capacity requests have been processed Allocated by the HSP without any request or signaling from the VSATs The HSP allocates a configurable number of slots equally to each VSATs in “round robin” manner The Free Capacity is distributed equally by the Hub to: All on-line VSATs or All idle VSATs
Inbound Adaptivity
ICM – 3 Dimensions of Adaptivity Multiple Dimensions of IB Adaptivity Adaptive channel rate selection (ICM 1D) Each VSAT is allocated the appropriate symbol rate Adaptive MODCOD selection (ICM 2D) Each VSAT is allocated the best possible MODCOD from the plan Adaptive Uplink Power Control (ICM 3D) The BUC output power is increased or decreased based on the received signal
Multi-Channel Selection
Freq Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
256ks/s
128ks/s
Time
Multi-Channel selection permits the adaptation of Symbol rates All carriers have their own symbol rate Known also as ICM (IB Coding Modulation) 1D
MODCOD Allocation
Freq
8 ¾
8
8
¾
6
8
/7
¾
8
8
¾
6
/7
8 ¾
8
8
8
8
¾
6
¾
¾
/7
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q¾
Q½
Gain per change
Q½
1.1dB
Q½
Q½
4.3dB
Q½
Q½
1.3dB
256ks/s
256ks/s
256ks/s
Time
TRF are allocated on a more robust or more efficient MODCOD within same or even different channels of different Symbol Rates Symbol rate and MODCOD division optimized per network: Different coverage areas Different VSAT capabilities / throughput requirements Known also as ICM (IB Coding Modulation) 2D
Power Loop Also known as Power Adaptive Coding Modulation (P-ACM) or Known also as ICM (IB Coding Modulation) 3D Remote Unit includes Linear BUC with adaptive power control The VSAT can increase TX power as the link faces fade conditions The VSAT determines its 1dB compression point and adapts TX power to changing link conditions so that transmissions are received at a fixed level at the satellite When weather conditions worsen the VSAT first increases TX power until reaches its limit, then robust MODCODs are used
SYNC bursts (every second) Decision to increase/ decrease
Received ES /N0 (in OB to VSAT)
Power Loop The Power loop compensates for: Rain fade Static attenuation (such as cable)
Satellite location offset and aging Temperature and frequency effects on BUC gain The BUC Saturation point is discovered by the Power Loop mechanism once per hour The VSAT increases SYNC bursts TX power and receives SYNC reception power readings from the hub until saturation is reached Saturation: TX power increase doesn’t fully translate into Rx power increase The Power loop is maintain used the Sync slots every second During the Power loop process, TRF Transmission power is not affected
Test Your Knowledge 1. Which allocation mechanism is guaranteed?____________________________ 2. Describe two differences between Volume based and Rate Based Capacity
Requests __________________________________________________________________ __________________________________________________________________ 3. Describe the Flywheel mechanism ____________________________________ 4. What is AVBDC requests used for?____________________________________ 5. How does the VSAT learn the Saturation point of the BUC?
__________________________________________________________________ 6. Can the same VSAT be allocated on a efficient or robust MODCODs in
different CT? __________________________________________________________________
