microwave network planning and design guidelines v1.0

7/27/2019 Microwave Network Planning and Design Guidelines V1.0

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Microwave network planning and design

guidelinesInternal

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Mobile Backhaul Network

Microwave Network Planning and Design Guideline

V1.0

Huawei Technologies Co, Ltd

All rights reserved


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Microwave network planning and design guidelines INTERNAL


Revision Record

Date Version Description Author

2011-5-12 Draft Zhang Zai

2011-5-25 V1.0

Update with capacity planning, AM/QOS

characteristics,fresnel zone radius,the

criteria of clearance,methods of the

microwave LOS survey,etc.

Zhang Zai


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Contents

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

2.1 Ring Topology ....................................................................................................... 52.2 Star Topology ....................................................................................................... 52.3 Tree Topology ....................................................................................................... 6

Chapter 3 Rules of network design .............................................................................................. 73.1 Route design ......................................................................................................... 73.2 Frequency plan ..................................................................................................... 83.3 Capacity plan ...................................................................................................... 10

3.3.1 Microwave+ optical+ lease line .................................................................. 103.3.2 Calculation method .................................................................................... 103.3.3 Convergence of transmission capacity ...................................................... 113.3.4 AM/QOS .................................................................................................... 11

3.4 Link design .......................................................................................................... 113.4.1 KPI of the link ............................................................................................ 113.4.2 Equipment protection configuration ........................................................... 123.4.3 Space diversity .......................................................................................... 123.4.4 Frequency diversity ................................................................................... 13

3.4.5 Hybrid diversity .......................................................................................... 133.4.6 Algorithms for reliability calculation ............................................................ 133.4.7 Chose for rain region ................................................................................. 143.4.8 Onsite Survey ............................................................................................ 153.4.9 LOS Survey ............................................................................................... 153.4.10 Equivalent Earth Radius K Factor ............................................................ 16


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3.4.11 Fresnel zone radius ................................................................................. 183.4.12 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 networks disaster tolerance capability.

In order to avoid high-low violation in one site, the total hops should be even in aring 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, its recommended to use N+0 hardware protection

to reduce the cost of the project.

2.2 STAR TOPOLOGY

BSC/RNC

BTS/

N

-B/

1

BTS/

N

-B-2

BTS/

N

-B-3

BTS/

N

-B-4BTS/

N

-B-5

Figure 1 ring 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 distance

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.

ROOT

Figure 3 tree topology

HU

BHU

B


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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 networks 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 ROOT 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 installantenna 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 20 KM is called short-haul, while link

distance above 20km is called long-haul.


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According to microwave products parameters, select the appropriate bandwidth

(7MHz14MHz28/29.65MHz40MHz56MHzmodulationQPSK

16/32/64/128/256QAM) and corresponding transmission capacity (4E18E1

16E144E153E175E1STM-1106Mb/s183Mb/s366Mb/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. Vpolarization 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) of each

hop, If the TD value exceeds a preset standard value (usually target TD


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There must have no obvious obstacles around the antenna, when you do the

frequency scanning. Youd 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 cant match the requirement due to shortage of the

frequency resource, its 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 fullybefore 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 the 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 modification 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 is 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 the 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 ofBelow Level

based on the BER of 10-6. The transmission system is Outage when the received


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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:

1Transmission capacity equal to 4E1/8E1:99.995%

2Transmission capacity larger than 16E1:99.997%

3Transmission 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 inorder to decrease the influence for transmission performance due to failure of the

equipment. Overmuch protection of equipment will increase the cost of construction.

So suggest:

11+0 for the terminal hop (or the last 3 hops);

21+0 for links in a ring protection group;

3 1+1(HSB) or N 1+1for 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). Its 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 the reflection fade is less

than 10 dB and annual availability can be satisfied.


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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 the algorithm as follow:

A Chose Vigants-Barnett in USA unless special demand of customer;


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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 layoutplan, the power system configuration, the length of various cable and the cable

laying)

6 The conditions to build a new microwave sitehydrology, 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 using 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 survey 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 introduced the

equivalent earth radius factor K concept in the microwave communication

engineering.

K=Re/R Re is the equivalent radius of the earth


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R is the actual radius of the earth, R=6370km

K=1it 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.

The microwave propagated under the standard atmosphere when the K value is

4/3and 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.

Tx Rx Tx Rx

k=

k=4/3

k=1

k=2/3

k=2/3

k=1k=4/3k=

d1 d2d

d1 d2d

Actual earth surface

hc

Equivalent microwave radiation

b. equivalent propagation traila. actual propagation trail

Actual microwave radiation

Figure 8 introducing the equivalent earth radius K factor


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Value ofkmin 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).


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In the last formula

F1is called the first Fresnel zone radius, the unit is meter

Fnis called the Nth Fresnel zone radius, the unit is meter

is the length of microwave, the unit is meterd1 d2 dthe 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.

Tx RxF1

Pd1 d2

Figure 10 the first Fresnel zone radius

d


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The standard of clearance value

The tape of

obstacle Kmin K=4/3 DescriptionKnife style Hc0 Hc0.6F1

K:equivalent earth radius

factor

Hc:clearance

F1:the first Fresnel zone

radius

Kmin:the minimum of K value

Smooth ground and

othersHc0.3F1 Hc1F1

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/.d is the distance away from the antennaD is the diameter

of the antennais the wavelength.

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