Microwave Network Planning and Design Guidelines V1.0

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Product name Microwave network planning and design guidelines Version V 1.0

Confidentiality level Internal Total 20 pages

Mobile Backhaul Network Microwave Network Planning and Design Guideline

V1.0

Huawei Technologies Co, Ltd All rights reserved

Huawei confidential. No spreading without permission.

Microwave network planning and design guidelines

INTERNAL

Revision Record Date

Version

2011-5-12

Draft

Description

Author Zhang Zai

Update with capacity planning, AM/QOS 2011-5-25

V1.0

characteristics,fresnel zone radius,the criteria of clearance,methods of the microwave LOS survey,etc.


Zhang Zai


INTERNAL

Contents Chapter 1 Summarize .................................................................................................................. 5 Chapter 2 Principle of network architecture ................................................................................. 5

2.1 Ring Topology ....................................................................................................... 5 2.2 Star Topology ....................................................................................................... 5 2.3 Tree Topology....................................................................................................... 6 Chapter 3 Rules of network design ..............................................................................................7

3.1 Route design ......................................................................................................... 7 3.2 Frequency plan ..................................................................................................... 8 3.3 Capacity plan ...................................................................................................... 10 3.3.1 Microwave+ optical+ lease line.................................................................. 10 3.3.2 Calculation method .................................................................................... 10 3.3.3 Convergence of transmission capacity ...................................................... 11 3.3.4 AM/QOS.................................................................................................... 11 3.4 Link design .......................................................................................................... 11 3.4.1 KPI of the link ............................................................................................ 11 3.4.2 Equipment protection configuration ........................................................... 12 3.4.3 Space diversity .......................................................................................... 12 3.4.4 Frequency diversity ................................................................................... 13 3.4.5 Hybrid diversity .......................................................................................... 13 3.4.6 Algorithms for reliability calculation ............................................................ 13 3.4.7 Chose for rain region ................................................................................. 14 3.4.8 Onsite Survey ............................................................................................ 15 3.4.9 LOS Survey ............................................................................................... 15 3.4.10 Equivalent Earth Radius K Factor ............................................................ 16



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3.4.11 Fresnel zone radius ................................................................................. 18 3.4.12 The Criteria of Clearance ........................................................................ 19



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CHAPTER 1 SUMMARIZE Microwave transmission is one of the most important means for wireless transmission backhaul in wireless project all over the world, it has a wide application in Radio Access Network (RAN).In order to build up a reliable, high quality and low cost network, microwave planning engineer should follow the principle as described in this document.

CHAPTER 2 PRINCIPLE OF NETWORK ARCHITECTURE

2.1 RING TOPOLOGY If the frequency resource is enough, transmission capacity and the geographical environment can meet the requirement, ring topology network is recommended to improve the network ’s disaster tolerance capability.

BTS/ -B/

BTS/ -B-2

N

N

1

BSC/RNC

BTS/ -B-3 N

BTS/ -B-5 N

BTS/ -B-4 N

Figure 1 ring topology

In order to avoid high-low violation in one site, the total hops should be even in a ring topology, such as 4, 6, 8, 10 hops to comprise a self-healing ring. According to the actual situation, if the total hops have to be odd in the ring network, designer should pay attention to the interference that maybe caused from transmitter to receiver at the same site. In microwave ring network, it’s recommended to use N+0 hardware protection to reduce the cost of the project.

2.2 STAR TOPOLOGY



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In order to reduce the transmission capacity, lower the configuration requirement of each hop. And to avoid the influence that caused by each hop, star topology with a HUB site in the center is recommended.

Figure 2 star topology There should be no more than 10 hops connected to the HUB site for a star network, otherwise it may cause serious interference because of the limited frequency resource. The 1+0 protection configuration is recommended for the last hop in the star network.

2.3 TREE TOPOLOGY In order to save frequency resource (reuse the frequency), shorten the dist ance of each hop, reduce the microwave antenna diameter, tree topology is recommended. The root nodes could be a BSC , a RNC, an optical access point or any site in a ring, the trunk is the Hub site, the leaf are the rest of the sites.

HU B

HU B

Figure 3 tree topology


ROOT


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It is suggested to configure with 1+1for the link that between Root site and HUB site. In a word, ring network ’s reliability is better than star network, tree network is the worst. Sometimes, because of the limited investment or competition pressure, we have to choose lower network protection configuration. In that case, we could reduce the quantity of ring networks and lower the device protection configuration in microwave links which are not very important.

CHAPTER 3 RULES OF NETWORK DESIGN

3.1 ROUTE DESIGN In order reduce construction costs, designer should make full use of the wireless tower, existed tower or shared tower with other operator. Collect the information about available resources is very important, so it must be done quickly. Shared tower should have high priority to sign intent agreement of rent. As the construction and maintenance costs of microwave repeater station are very high, we could use some means to minimize the number of repeater station, such as: 1、

Move the BTS appropriately without affect the coverage , Maybe the LOS issue

will be resolved without build new repeater; 2、

Sometime LOS will be fine if increase the mounting height of antenna, So

Increase the tower height also a good way to avoid repeater, but should to pay attention the cost of tower; 3、

For some remote isolated sites (which need to build one or more microwave

repeater stations), try to postpone the site to next phase or use leased line solution, even cancel it; 4、

If it can solve several BTS’ transmission problem with building a single

repeater, you may consider to building a microwave repeater station; 5、

Try to minimize the hops of end to end (such as BTS to ROOT station), as show

in figure 4:



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Figure 4 It is not suggested (there is 8 hops from ROOT to end station)

Figure 5 it is suggested (there is only 4 hops from ROO T to end station) 6、

Try to shorten the distance of microwave transmission and reduce antenna

diameter if all the suggestions above can be satisfied, which are beneficial to install antenna and improve transmission quality.

3.2 FREQUENCY PLAN We should get microwave frequency information from customer firstly. To obtain the T/R spacing in each frequency band and the channel arrangement, Or try to propose the microwave frequency according to the ITU recommendation and product parameters. Then submit to customer and get approve. According to the available microwave frequency resource, principles can be defined for different frequency band. Generally, lower frequency is suitable for long distance transmission, while higher frequency is suitable for short range transmission. Commonly, frequency below 10 GHz (6, 7, 8 GHz) is called low band, frequency above 10 GHz is called high band. Also, the link distance which is less than 2 0 KM is called short-haul, while link distance above 20km is called long-haul. Huawei confidential. No spreading without permission.


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According to microwave products parameters, select the appropriate bandwidth (7MHz、14MHz、28/29.65MHz、40MHz、56MHz）、modulation（QPSK、 16/32/64/128/256QAM) and corresponding transmission capacity (4E1、8E1、 16E1、44E1、53E1、75E1、STM-1、106Mb/s、183Mb/s、366Mb/s etc.) for project. We should avoid same frequency band high-low violation at same site because it will cause internal interference, Also try to keep all the frequency band with high or low identity at same site. Same frequency channel high-low violation is strictly prohibited. For polarization, “VVHH” configuration was recommended for the route which turning angle is close to 180 degrees, it can solve the over-reach interference issue. V polarization has better performance against the rain attenuation in high frequency band comparing with H polarization, so it is often used for the links with poor condition transmission. The use of different channels also can solve over-reach interference problem, and try to avoid the H polarization application. Use the existing data and pre-planning link data to analysis frequency interference is an important course in frequency planning. Use the tools to analyze the interference hop by hop, also calculated the threshold deterioration (TD) o f each hop, If the TD value exceeds a preset standard value (usually target TD<3dB), you should find the source of interference and change the frequency and polarization configuration of some hops, until the standard requirements are fulfilled. Otherwise, more frequency channels are needed. For some microwave links with the TD value exceeds the preset standard (such as 3dB). The TD value could be updated to the link performance calculation. If the calculation result can meet the annul availability KPI and recognized by customer, that is ok. Now, microwave interference calculation is more difficult also the calculation result is getting worse. There are two reasons mainly, first, the data in existed network is hard to collect also not so accurate; second is the complex terrain and ground features information. Microwave network planning tool PATHLOSS currently does not support calculating the interference with terrain and ground features information, only for a rough analysis and calculation with plane terrain. With the rapid deployment of radio network overseas, microwave electromagnetic environment is becoming increasingly complex. Interference calculation cannot show the intensity of the interference correctly, so we have to find an available frequency through frequency scanning at site.



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There must have no obvious obstacles around the antenna, when you do the frequency scanning. You’d better choose the pre-installed antenna position to scan frequency, requirements are as follows: Scan angle: 360 degrees; Frequency range: frequency that customer could acquire; Scan polarization: V and H; Step angle: 10-15 degrees.

3.3 CAPACITY PLAN Every base station needs one or several E1 in GSM network, which has less demand for transportation capacity. The total capacity of microwave link is depend on the sum of the capacity of the base stations which through it, and 25% redundancy should be considered for network developing. In the case of more demand of bandwidth in the 3rd generation and LTE network, Microwave capacity maybe can’t match the requirement due to shortage of the frequency resource, it’s better to build the backhaul network by mixed transmission network.

3.3.1 MICROWAVE+ OPTICAL+ LEASE LINE Operator usually has a developing plan in 3-5years according to market forecast for the 3rd generation or LET wireless network project. Transmission rate increases as the increasing of the subscribers and type of services. Optical resources in existence and under construction should be utilized f ully before using the microwave. Each separated microwave network can be constructed from the root point, which is an access point of the optical network. A further construction plan of optical transmission network can be made according to the structure of the carrier network and the demand of capacity. Lease line also can be used as transmission root point and solve the transmission problem of remote isolated site.

3.3.2 CALCULATION METHOD



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The terminal link capacity should consider the peak rate of the last base station, and the capacity of the rest link is the sum of the average rate of all connects base station. Peak rate and average rate can be obtained from the long-term wireless network planning. The maximum transmission rate should be configured when transmission capacity exceed the maximum rate of the equipment. It can fulfill t he demand of transmission capacity and used as the protection link in further carrier network.

3.3.3 CONVERGENCE OF TRANSMISSION CAPACITY All the base stations which using the Ethernet protocol as the transmission interface share the transmission bandwidth in 3rd generation and LET network. As a result, the total capacity is not equal to the sum of the link rate but convergence of it. The convergence ratio is different due to different user custom in different wireless network. Transmission rate of every base station should be recorded and analyzed to decide the transmission convergence ratio. It is useful for modific ation of the construction plan and operation plan, or the rent plan of leased line.

3.3.4 AM/QOS AM is an effective method to deal with the decline of KPI in the case of limited size of antenna. Both of the transmission rate and unavailability ratios can be fulfilled. AM function can run properly under uniform QOS strategy. AM function i s a method for developing the network in further, and suggested to disable it.

3.4 LINK DESIGN 3.4.1 KPI OF THE LINK Calculate the probability of the received signal which is lower than th e threshold is a common method in wireless backhaul network. The equipment is on the status of “Below Level” when the received signal is lower than the threshold, at the same time bit error will show up or communication will break down. The receive threshold is related to the transmission BER, and we usually get the percentage of “Below Level” based on the BER of 10-6. The transmission system is “Outage” when the received Huawei confidential. No spreading without permission.


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signal is lower than the threshold according to ITU-T F.1605. Acceptable annual unavailability range from 99.995% to 99.999%, and the exact value is decided by the importance of the link in the network, such as: 1、Transmission capacity equal to 4E1/8E1:99.995% 2、Transmission capacity larger than 16E1:99.997% 3、Transmission capacity larger than STM-1:99.995%

3.4.2 EQUIPMENT PROTECTION CONFIGURATION We can use 1+1 backup to protect the equipment and enhance the reliability in order to decrease the influence for transmission performance due to failure of t he equipment. Overmuch protection of equipment will increase the cost of construction. So suggest: 1、1+0 for the terminal hop (or the last 3 hops); 2、1+0 for links in a ring protection group; 3、 1+1(HSB) or N ×（1+1）for the rests.

3.4.3 SPACE DIVERSITY Space diversity should be used to deal with multipath and insufficient fade margin in the case of bad transmission condition (such as: Over water /long-haul/large capacity). It’s better design with same size of the main antenna and the diversity antenna, and the distance of the two antennas should be 6-20m. Calculate the precise space between the two antennas through PATHLOSS in the case of severity reflection of water in order to make sure the received signals are complementary as show in Figure 6. Space diversity should also be considered for short distance (less than 20km), over-water links if the external condition is allowed. Unless t he reflection fade is less than 10 dB and annual availability can be satisfi ed.



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Figure 6 Reflection analysis of space diversity

3.4.4 FREQUENCY DIVERSITY Frequency diversity is one of the effective solutions to deal with demanding for large size of antenna in Middle East area such as Bahrain where has poor transmission condition. It is not suggested to apply in the city or suburb but countryside due to the limitation of frequency resources.

The trunk link of

microwave can be configured to mode of N+1 or 2*(N+1), which work as frequency diversity.

3.4.5 HYBRID DIVERSITY A link can be configured with both space diversity and frequency diversity at the same time in order to get double effect of improvement of diversity if is allowed.

3.4.6 ALGORITHMS FOR RELIABILITY CALCULATION There are several algorithms for reliability calculation such as: Vigants-Barnett/KQ Factor/ITU-6/7/8/9/10/11/12. And we usually use ITU-7/8 which is satisfied in most area besides the places where have severe duct type fade, such as the seacoast of the Persian Gulf, the Mediterranean and the West Africa. As a result, ITU-9/10/11/12 are released by ITU. We can choose t he algorithm as follow: A Chose Vigants-Barnett in USA unless special demand of customer ; Huawei confidential. No spreading without permission.


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B Chose KQ Factor in China unless special demand of customer; C Chose ITU-7/8 or ITU-12 for the rest area according to the result of the

arithmetic,

3.4.7 CHOSE FOR RAIN REGION The signal deteriorates when passing through the rain region, which is defined as the rain fading. It should not be ignored when designing the microwave link especially for the high frequency band (Higher than 10GHz). ITU-R divided the whole world into several rain regions (A-Q) based on long-term statistics of rainfall.

Figure 7 world rain regions Possibility of rain of every rain area from 1% to 0.001%, show as follow:



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Both Figure 7 and Table 1 can be obtained from ITU-R P.837-1. It is suggested to use the data got from the customers.

3.4.8 ONSITE SURVEY The main tasks of the microwave onsite survey are to collect relevant site information, to conduct the site measurement, and to provide the survey report. The collected information and submitted reports are used for reference during the microwave planning and system implementation. The main content: 1、

The actual co-ordinates and altitude of the site, and mark the precise location

on the 1:50000 map, or you can mark the location of the antenna will be installed by using Google Earth； 2、

Available tower information on site,(tower heights, tower types, available

antenna height, space and direction)； 3、

360-degree panoramic photos of the microwave site. （take photos every

30-degree and mark the directions）； 4、

The information of the existing microwave link. （capacity, frequency, the

antenna height, size and azimuth, etc.）； 5、

The conditions of the existing microwave site (site layout plan, indoor layout

plan, the power system configuration, the length of various cable and the cable laying)； 6、

The conditions to build a new microwave site （hydrology, geology, roads,

power supply and place etc. ）. A joint-survey is suggested for both microwave and wireless teams to finish the survey at the same time. Alternatively, all the information collection can be done by one team in order to improve the efficiency, accuracy and uniqueness of the survey.

3.4.9 LOS SURVEY The main tasks of the microwave LOS survey are to obtain the terrain information, accurate heights of the ground features, and to provide a terrain profile diagram, or to ensure the LOS. The information is for reference during the microwave routing design. Typical Methods of the Microwave LOS Survey



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1. Seeing with eyes, use eyes and digital camera to check the LOS of the radio link. When this method is adopted, a telescope, flash of the digital camera, viewfinder, red flag, or hydrogen balloon can help in checking whether the LOS is available ； 2.When two microwave sites are located in suburb areas or in the country field , read the terrain elevation values of the microwave route by usi ng 1:50000 (or smaller proportion), confirm the location of the site and the height of the surface feature onsite, and then generate the terrain profile diagram, determine the microwave antenna height. 3. For the second method, if you cannot acquire the 1:50000 map, you can get the terrain elevation values and the surface feature height by using the GPS altitude meter with the same mode. 4.LOS simulation using satellite technology to provide high- precision of terrain elevation values to guide the determination of the microwave antenna height. During the pre-planning stage of the project, the terrain profile diagram can be generated by using the UTM electronic map, the SRTM electronic map or the map download from Google Earth website. Due to the limitation of the accuracy of the terrain data, it can only as a reference for the route planning, not as a basis to determine the LOS condition. Usually microwave LOS survey should draw up the plan and range of s urvey in order to avoid bundling with the onsite survey. The onsite LOS survey is not necessary if the microwave link can get the terrain elevation values by LOS simulation or it has obviously LOS condition. If there have obvious obstacle on the far-end site and the microwave link route is determined, you can perform both LOS survey and onsite survey.

3.4.10 EQUIVALENT EARTH RADIUS K FACTOR

As a result of atmosphere refraction, the microwave radiation spread in the atmosphere will have a slightly bent (such as optical refraction). It i ntroduced the equivalent earth radius factor K concept in the microwave communication engineering. K=Re/R

Re is the equivalent radius of the earth； Huawei confidential. No spreading without permission.


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R is the actual radius of the earth, R=6370km。 K=1，it is considered the microwave is propagated along a straight line, and is not bent. K=∞，it is considered the microwave curvature is the same as the earth surface curvature, the microwave propagated around the earth parallel to the surface.

Actual microwave radiation

k=∞

Equivalent microwave radiation

k=4/3 Tx

Rx

k=1

Rx

Tx

k=2/3 hc k=2/3 Actual earth surface

k=1 k=4/3

d1

d2

d1

d a. actual propagation trail

k=∞

d2

d b. equivalent propagation trail

Figure 8 introducing the equivalent e arth radius K factor

The microwave propagated under the standard atmosphere when the K value is 4/3，and it is considered the microwave propagation trail slightly bent upward. Under the actual atmosphere, the K value is changed from Kmin to K=∞。 The Kmin value can be found through the ITU-R P.530 curve proposed.



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Value of k min exceeded for approximately 99.99% of the worst month (continental temperature climate)

Figure 9 Kmin and propagation distance K factor is a very important concept which should be considered in microwave engineering.

3.4.11 FRESNEL ZONE RADIUS

The sum of the distance from P to Tx (transmitter) and the distance from P to Rx (Receiver) is constant. The region encircled by the trail of P is an ellipsoid. The field strength of the receiving point(Rx) will change as the radius of the circle section of P changes. When the field strength first reach the max, the radius of the circle section of P is represented by the first Fresnel zone radius (F1).



Rx

F1

Tx

d1

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P

d2 d

Figure 10 the first Fresnel zone radius

In the last formula ： F1 is called the first Fresnel zone radius, the unit is meter ； Fn is called the Nth Fresnel zone radius, the unit is meter ；

is the length of microwave, the unit is meter； d1 d2 d ，the unit is kilometer. 3.4.12 THE CRITERIA OF CLEARANCE

Consider the range of the K value changes, clearance (Hc) should be guaranteed from the obstacle to the microwave straight line. For link with a single obstacle, the value of clearance (Hc) should meet the request below.



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The standard of clearance value The tape of obstacle K:equivalent earth radius Knife style

Hc ≥0

Hc≥0.6F1

factor Hc:clearance

Smooth ground and others

F1:the first Fresnel zone Hc≥0.3F1

Hc ≥1F1

radius Kmin:the minimum of K value

The value of clearance for link with some obstacles should meet the request below: When K=Kmin , the diffraction fading loss caused by obstacles should less than 10dB； When K=4/3， If without fading, the Receive Signal Level should not less than the calculate result with free space. For link with Space Diversity, the clearance to main antennas should meet the demand in the sheet above, and the loss introduced by obstacles should be less than 15dB for the clearance to diversity antennas(for link with one or more obstacles). Moreover, the clearance(Hc) should be greater than the value of the first Fresnel zone radius (F1) for the area away from the antenna which complies with the formula, d>17.1D2/λ.（d is the distance away from the antenna，D is the diameter of the antenna，λis the wavelength）.


Microwave Network Planning and Design Guidelines V1.0

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