chapter5 design of wireless network

8/14/2019 Chapter5 Design of Wireless Network

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Wireless Network Planning Table of Contents

Table of Contents

Chapter 1 Design of Wireless Network .......................................................................................11.1 Design of Base Station Address ........................................................................................11.2 Design of Parameters for Base Station Project................................................................. 3

1.2.1 Environment for Antenna Installation ......................................................................3

1.2.2 Antenna Separation in GSM System ......................................................................5

1.2.3 Antenna Separation Form GSM and CDMA Base Station ......................................5

1.2.4 Antenna Installation Interval................................................................................... 8

1.3 Link Budget..................................................................................................................... 11

1.3.1 Link Budget Model................................................................................................ 11

1.3.2 Reference point for base station sensitivity ..........................................................121.4 Design of Coverage Area ................................................................................................151.5 Capacity Distribution .......................................................................................................17

1.5.1 Voice channel distribution .....................................................................................17

1.5.2 Configuration of control channel........................................................................... 19

1.6 Location Area Design ......................................................................................................20

1.6.1 Definition of location area .....................................................................................20

1.6.2 Division of location areas ......................................................................................21

1.6.3 Calculation of location areas .................................................................................24

1.7 Design of Indoor Coverage System ................................................................................26

1.7.1 Design of indoor antenna system .........................................................................261.7.2 Capacity Analysis and Design ..............................................................................33

1.7.3 Frequency Plan .....................................................................................................35

1.8 Design of Cell Data .........................................................................................................36

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Wireless Network Planning Chapter 5 Design of Wireless Network

Chapter 1 Design of Wireless Network

The most important of all in designing a wireless network concerns the design ofnetwork layout. Such work involves the following in detail:

(1) Decide the way of frequency multiplexing in light of frequency bandwidth;

(2) Estimate the number of base stations required for the network based onexperience;

(3) Determine the theoretic position of the base station;

(4) Estimate network capacity;

(5) Assume parameters relevant to the base station (hierarchical structure of thenetwork, transmitting power, antenna type, height to be hung, direction and angle ofdeclination etc.);

On the basis of determining the basic layout of base station, plan the frequency andadjacent areas, and then complete the related cell data, so as to accomplish theentire planning process.

1.1 Design of Base Station Address

In planning a wireless network, the design of base station address should generallymeet the following requirements:

(1) The address should serve to meet the objective of rational cell structure; make acomprehensive analysis using an electronic map and a paper map of the urban area(information about ground objects and surface relief preferred). Standby stationaddress is required in the course of selecting a base station. For this purpose, it is

required to consider the overall network structure, and make a choice in such majorrespects as coverage, anti-interference and traffic balance. In practice, the operator ispossibly required to consult with the proprietors as to the station to be chosen. Ingeneral, the station address should be arranged within a range of 1/4 radius ofcellular base station (r for minimum width). It is allowed to choose several standbystation addresses within this range.

During the stage where the network is established and there are few base stations,the station should be generally located at the center of an area where most of thesubscribers live. In designing a station address, top priority should be given toensuring good communication in special areas such as the place of governmentalagencies, airport, railway station, news center and major hotels and avoid overlappingcoverage in these areas; for other areas requiring coverage, station addresses shouldbe designed in accordance with standard cellular structure, while address selection

for suburbs, highroads and rural areas with a large area to be covered is free of limiton cellular meshes;

(2) Without affecting the layout of base stations, existing telecommunicationsbuildings and post offices should be chosen as the station address, so that theirfacilities such as equipment room, power supply and iron tower can be fully utilized;

(3) Point the major lobe of antenna to the areas with dense traffic so as to enhancethe signal intensity in this area and thus improve the communication quality; deviatethe direction of antennas major lobe from co-frequency cells, so as to controlinterference in an effective way. In urban areas, it is recommended that the overlappingcoverage of antenna in adjacent sectors should not exceed 10% in depth; the overlapping

depth of cover between the coverage areas in suburbs and towns with the directional

included angle of the sectors no less than 90. Attention should also be paid to the

correspondence between the carrier wave number and the cell in designing. A larger

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number of carrier wave should be configured for a cell of high density.

In designing an azimuth angle, it should be determined not only based on thedistribution of traffic around each base station but also from the perspective of theoverall network. In general, it is recommended to adopt, if possible, the same azimuthfor each urban base station, in order not to make it complicated to plan the networkwhen the cell breaks apart in the future; to avoid trans-regional coverage, the majorantenna lobe in populous downtown area should be kept from facing a straight street.In places such as outskirts and trunk roads, the antenna bearing should be adjustedin light of the objects to be covered.

(4) Generally, high mountains in urban areas or suburbs(over 200 300 metershigher than the urban areas in altitude above sea level ) are not regarded as stationaddresses in order to prevent co-frequency interference and avoid areas with weaksignals within their respective coverage areas, and to ease the difficulty inengineering construction and make it easy for maintenance;

(5) New base stations should be installed in places, where traffic is convenient,electric supply is available, the environment is safe without occupying much fertileland; such places should not be near high-power radio transmitting station or other

interference sources, whose intensity should not exceed the indexes for the shield ofbase station equipment against useless radiation;

(6) The designed station address should be kept far away from the forest so as toavoid the fading of receiving signals;

(7) The designed station address must ensure the transmission link between it andthe base station controller is connected well;

(8) Attention must be paid to the effect of time dispersion in choosing an address frommountainous areas, limnological regions with steep banks or many lakes, hills, citiesand an environment with high buildings. The address for a base station should be aplace near reflecting objects or put the directional antenna back on to the reflectingobjects when the base station is far away;

Note:

Time dispersion mainly refers to the problem of cofrequency interference arising fromthe time difference between master signals arriving at the receiver and othermultipath signals in terms of time for transmission in space (transmission distance);according to GSM protocol, the receiver equalizer must be equipped with a timewindow of 16 ms (equivalent to 4.8 Km). Multipath signals with a time window lessthan 16 ms are harmless and even instrumental; but those with a time window of over16 ms are regarded as the cofrequency interference signals against the mastersignals. In this case, it is required to consider whether the level difference betweenthem meets C/I value, that is, master signals are over 12dB greater than the multi-path signals. The time window of Huawei receivers is more than 20ms.

(9) While choosing an address form urban high buildings, the height of building maybe wisely used to classify the network structure; the antennas for major base stationsshould be a litter taller than the average height of buildings. In general, the basestation antenna in populous urban areas should be as high as 2530 meters but it is4050 meters in the suburbs (or pointing to suburb cells);

(10) In choosing an address for highroads or mountain coverage, we should make themost of land features, such an open area as the turn of a highroad.

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1.2 Design of Parameters for Base Station Project

When an address is selected, it is required to determine the engineering parameters

for each base station, including: the latitude and longitude of the place of a basestation antenna, hanging height, antenna direction, gain, azimuth, angle ofdeclination, feeder line type and transmitting power of each base station cell. Thiswork should be done on the basis of field survey.

We must know well the generation situation about the project before the survey andcollect various data relative to the project, including various project documents,background information, information about existing network and local map. Inaddition, a contract configuration list, latest network planning and exploration surveyof base stations should be prepared. Such instruments as digital camera, GPS,compass, ruler and laptop should be prepared. Make sure that such instruments areusable before setting out.

Attention must be paid to the following during the survey: while using GPS to position

the latitude and longitude of a base station, do not allow other persons to stay aroundGPS, in an effort to make the positioning accuracy less than 30 m; make a detailedrecord of the surroundings around the base station, such as the distribution ofbuildings, whether there is powerful interference equipment and shared addressequipment. On the one side, specify the antenna parameters and on the other side,this record is to avoid oblivion in the case of numerous base stations; in using acompass, substances made of iron should be avoided in order to magnetization,which will cause overlarge difference in measurement.

Survey is an important part to specify the base station layout ultimately. A field surveyfor base station involves optical measurement, spectrum measurement and addresssurvey. Optical measurement is to check if there is a barrier around the base station,which may reflect the electric waves, such as high buildings. Spectrum survey aims toknow if the electromagnetic environment around the base station and the antenna at

present and in the near future is in good condition. Address survey is focused on theconditions for installing antenna and equipment, power supply and naturalenvironment. The focus of the following description is on the installation and design ofantenna.

1.2.1 Environment for Antenna Installation

Installation environment involves the environment near the antenna and theenvironment around the base station. For the environment near the antenna, theinterval between antennas and the effect of an iron tower and building floors on theantenna are the main concern. For the environment around the base station, attentionis mainly focused on the effect of buildings less than 500 meters high ontransmission.

To install a directional antenna on a wall, the antenna transmitting direction ispreferably perpendicular to the wall. If its azimuth angle must be adjusted, theincluded angle between the antenna transmitting direction and the wall is required toexceed 75. In this case, as long as the front-to-back ratio of antenna is more than20dB, the effect of signals reflected from the wall in its negative direction on those inthe radiating direction will be rather meager, as shown in Figure 5-1.

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no more than 15

vertical directionantennas direction

Figure 5-1 Included Angle Between the Antenna and the Wall inInstallation

To get a most desirable coverage, the headroom around the antenna is required to be 50100m. For 900M GSM, the radius of first fresnel zone within this range is about 5m, whichmeans that the base of the base station antenna should be 5 meters higher than itsenvironment. By making a wise use of the height of the buildings around it, we are able toattain the base station coverage as we have expected.

The requirement on the headroom around the antenna is shown in Figure 5-2.

antennaantenna

antenna

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Distance from the antenna to thebuilding edge D(m)

Height from antenna base to building roofH(m)

02 0.5

2 10 1>10 2

1.2.2 Antenna Separation in GSM System

To avoid inter-modulation interference, there must be space between the receiver andtransmitter of the base station: Tx-Rx: 30dB; Tx-Tx: 30dB. This is also applicable tothe shared-address system for GSM900 and GSM1800. The antenna separation issubject to the antenna radiation directional diagram, spatial distance and gain with noregard to the attenuation caused by voltage standing wave ratio. It is worked out asfollows:

For vertical arrangement layout, v=28+40lg(k/) (dB)

For horizontal arrangement layout, Lv=22+20lg(d/)-(G1+G2)-(S1+S2) (dB)

Where Lv refers to required separation, is the length of carrier wave, k is vertical

separation, d is horizontal separation, G1, G2 are respectively the gains of thetransmitting antenna and receiving antenna in their maximum radiation direction (dBi),and S1, S2 are respectively the secondary lobe level of the transmitting antenna andreceiving antenna in the direction of 90 (dBp, negative value relative to masterbeam). Normally, 65 fan-shaped beam antenna S is about -18dBp, 90fan-shapedbeam antenna S is -9dBp, and 120 fan-shaped beam antenna S is -7dBp, subject tothe special antenna directional diagram. In the event of omni-antenna, S is 0.

The antenna mount for GSM900 and GSM1800 systems should meet the followingrequirements:

Directional antenna

In the same system, the horizontal interval between the two antennas in the samesector is equal to or more than 4m; the horizontal interval between the two antennasin the same sector is equal to or more than 0.5m;

Between the two systems, when the two antennas of the same sector are in the samedirection, the horizontal interval between the antennas is equal to or more than 1m;

The vertical interval of antenna is equal to or more than 0.5 meters; the distance fromthe antenna base to the enclosing wall on the roof is equal or more than 0.5 meters;

The included angle between the line connecting the lower antenna edge with theantenna face pointing to the roof and the horizontal direction is more than 150;

The included angle between the connecting line of two antenna mounts and theantenna direction should fall within the following range:

Antenna horizontal plane lobe width 60-70 90 120

Included angle between the connecting line

of two antenna mounts and the antennadirection

>4045 >55 >70

Omni-antenna

antenna horizontal interval 10 meters or antenna vertical interval 0.5 meter; the

distance from the lowerantenna edge to the enclosing wall on the building roof0.5meter.

1.2.3 Antenna Separation Form GSM and CDMA Base Station

The analysis of CDMA and GSM system interference should be based on the relation

between the frequency of two systems and their characteristics in transmitting andreceiving so as to study the interference in detail. The interference mainly involves the

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following three aspects: scattering interference, block interference and inter-modulation interference. Of these three different interferences, scattering interferenceplays a major part and has the most effect. Thus it is the key concern in networkdesign. As there is less inter-modulation interference and block interference than thescattering interference, it is not discussed herein. Take the scattering interference of

CDMA2000 1X against GSM900 for explanation.Currently, the frequency bands of China Unicoms CDMA2000 1X and the presentGSM900 are as follows:

BTS transmission (MHz) BTS receiving (MHz)

GSM900 935-960 890-915

CDMA 870-880 825-835

As the two are too close to each other, interference against each other will easilyoccur. Mostly, the transmission from CDMA2000 1X will interfere with GSM900, whichreceives disclosure signal beyond the CDMA band and fall within the channels ofGSM receiver, thus raising the noise level of GSM receiver only to worsen GSMuplink, reduce the coverage of the base station, and worsen the network quality. Ifthere is no enough separation between two base stations or the send filter interferingthe base station fails to provide enough outband attenuation, then the signals fallinginto the band width of the interfered base station might be very strong, and thusincrease the noise threshold of the receiver. The degree in system performance falldepends on the intensity of interference signals, which in turn remain subject to theperformance of the sending unit of interfering base station, the performance ofreceiving unit of interfered base station, frequency band interval and antennaseparation.

The diagram of an interference model is shown as follows:

Figure 5-3 Diagram of Interference Model

Seen from Figure 5-3, the signals output from the amplifier of interference source base stationare first filtered by the send filter, then attenuate accordingly due to the separation between twobase stations, and finally they are received by the receiver of the interfered base station. Thepower of scattering interference arriving at the antenna terminal of the interfered base stationcan be expressed in the following formula:

IbPTXAMPPattenuationIisolation10 lglgWBinterferferferedWBinterferferfering

where, Ib refers to the interference level (dBm)received at the receiving terminal of theinterfered base station, PTX-AMP is the power (dBm) output from the interference sourceamplifier, Pattenuation is the outband suppressed attenuation of the send filter, I isolationrefers to the separation (dB) between base station antennas, WB interfered is the signalbandwidth of interfered base station, and WBinterfering refers to the measurablebandwidth of interference signals, also understood as the defined bandwidth of the

scattering radiation. In figuring out the interference level of the interfered base station,

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the difference and conversion between the two should be taken into consideration.

Regulate the above formula, and we will get:

IisolationPTXAMPPattenuationIb10 lglgWBinterferferferedWBinterferferfering

If the CDMA2000 1X transmitting frequency band is the last one at high end, that is

878.49MHz. CDMA2000 1X amplification output with the scattering falling within 890-915MHz-13dBm/100kHz. The specific measures for realization is to filter and combine eachtransmitting frequency band using a band-limiting filter with a bandwidth of only 1.23MHz. Theband-limiting filter of this kind has great outband attenuation, and attenuates at 890MHz up to56dB and at 909MHz up to 80dB. All things considered, the worst of all is that the high end ofCDMA system interferes with the frequency at the lowest end of GSM system.

Then,

Iisolation = (-13dBm/100kHz)- 56 - Ib10lg (200kHz/100kHz)

Ib is the maximum interference level (dBm) received by interference base station allowed at itsreceiving antenna terminal. To ensure that the sensitivity is not affected, the externalinterference level is required to be lower than the bottom receiver noise by 10dB. In this case,the affected sensitivity amounts to around 0.5 dB. The bottom noise of GSM receiver is: noisedensity bandwidth noise coefficient. Suppose the receiver noise coefficient is 8, the bottom

noise is expressed in logarithm as follows:

174 noise coefficient lg(200000)=-174+53+8113dBm. Then the possible maximumscattering interference is:

-113-10-123dBm/200kHz

This requires the scattering interference or intermodulation of other systems falling on GSMreceiver should be less than this value. Only in this way will it cause serious interferenceagainst GSM system.

Thus, we can get the following:

Iisolation = (-13dBm/100kHz)- 56 - Ib10lg (200kHz/100kHz)

= -13 - 56 - (-123dBm/200kHz) + 10lg (200kHz/100kHz) = 57 dBm/200kHz

In other words, whether CDMA antenna and GSM900 antenna share a station address, there

should be a separation of 57dB between them.There are many ways to reduce the interference: make the spatial distance between theantennas enough; filter outband channel noises of receiver with the receiver placed on differentequipment, such as receiver, multiplexer and separator.

I. On equipment interference

As stipulated in IA/EIA-97 protocol, the scattering interference of CDMA antennainterface falling with the receiving frequency band of GSM900 should be less than -13dBm/100kHz, that is, CDMA system will cause serious interference against GSM900.On this basis, we consider the problem of interferences between the two and shared-address construction in the initial design. To be specific, at each transmittingfrequency band, use a band-limiting filter with a bandwidth of 1.23MHz for filteringand combination. This band limiting will attenuate greatly outside the band, so as to

reduce the requirement for spatial distance.

II. Requirment ofantenna separation

To minimize the above interferences, it is required to keep a proper separationbetween the antennas of two systems. To quote the formula as defined in Section5.2.2:

For vertical arrangement layout, Lv=28+40lg(k/)(dB)

For horizontal arrangement layout, Lv=22+20lg(d/)-(G1+G2)-(S1+S2)(dB)

Here are several circumstances to explain the requirement on the separation betweenCDMA and GSM900 antennas:

1) CDMA and GSM900 antennas do not share a station address with antennas

installed horizontally opposite each other (or shared-address omni-antenna).

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Suppose the effective gains between the two antennas in the maximum radiationdirection are 10dBi respectively (feeder line loss considered) with interference signalsof 890MHz. According to the foregoing analysis, the separation between CDMA20001X equipment and GSM should be at least 57dB.

According to the above formula, we can get the following:

57=2220lg(Dh/)(10+10)

The horizontal interval between the two base station antennas d180m

Effective antenna gain inthe direction of radiation(dBi)

Separationrequirement (dB)

Antenna intervalrequirement (m)

10 57 180

15 57 569

2) CDMA and GSM900 antennas share a station address (antennas placed on thesame platform and separated horizontally), directional antenna.

Suppose GSM900 and CDMA20001X antennas are placed horizontally and bothadopt 65 degree antennas; Suppose the antenna gains of GSM and CDMA20001x in

the direction of radiation are both 15dBi.65antenna plane side lobe is about -18dB in the direction of 90 degrees and then theeffective gains in the said direction are 15-18-3dBi.

57=2220lg(Dh/)(15+15) + ((-18)+ (-18))

According to the above formula, we conclude that the horizontal interval between theantennas is d9m.

Effective antenna gain inthe direction of radiation(dBi)

Separationrequirement (dB)

Antenna intervalrequirement (m)

10 57 315 57 9

3) CDMA and GSM900 antenna share a station address (antennas are scattered ondifferent platforms of the iron tower and vertically separated), omni-antenna anddirectional antenna.

57=28+40lg(k/)

From the above formula, we come to an conclusion that the vertical interval betweenthe antennas is d1.7m.

What is described above is a way of deduction. In practical networking, we will haveto install antennas of other type at shared address, which requires us to figure it outon our own in combination with the equipment indexes. The indexes of importanceare as follows: scattering radiation, calculation of interference power of theinterference signals against the interfered equipment and calculation of antennaseparation.

1.2.4 Antenna Installation Interval

Diversity technology is one of the most effective measures to withstand attenuation. Ifthe two antennas on the plane are 10 wavelengths away from each other, attenuationwill be reduced. Although the receiving diversity requires two or more ports, itobviously reduces attenuation, thus reducing the power of a mobile station andimproving the transmission quality, which serves as an advantage to the entiresystem.

In the event of space diversity, the distance between the two receiving antennas is 1218; 1=0.32m (900MHz); 1=0.16m (1800MHz). In general, the horizontal intervalbetween diversity antennas stands at 0.11 times that of the effective height of theantenna. The higher the antenna is installed, its horizontal interval of diversityantenna will be greater. But when antenna interval is 6m, it is very difficult to install an

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antenna to the tower. In addition, for diversity reception, vertical separation is requiredto stand at 56 times that of the same diversity gain. Generally, in actual project, wedo not adopt vertical diversity but vertical separation, especially for omni-antenna.

When the effective installation height of diversity antenna is less than 30m, anddiversity antenna interval is less than 3m, the two pairs of antenna are within eachothers near field, thus distorting the antenna directional diagram. In order to keep thefluctuation of directional diagram caused by the effect of the two antennas upon eachother below 2dB, the diversity distance should be more than 3 meters in the event ofany antenna effective height.

In addition, attention should be paid to the following in the event of space diversity: tocover a highroad, we generally make the connecting line (diversity plane) of tworeceiving antennas perpendicular to the highroad.

space diversity distance(4--6m for GSM)

actual installed distance

Note:

Figure 5-4 Diagram of Antenna Space Diversity Distance

The following table shows the requirement for GSM antenna interval (suppose thereis no barrier between the antennas; in practical project, for example, the iron towerholds up between all omni-antennas, the horizontal interval can be reducedobviously):

Omni-antenna:

Separation requirement: TX-TX, TX-RX: 30dBVerticalinterval

(recommended)

Horizontal interval Remark

GSM900: TX-TX, TX-RX 0.5m Gain=10dBi: 10mAntenna from

tower 2m

GSM1800: TX-TX, TX-RX 0.25m Gain=10dBi: 5mAntenna from

tower2mGSM900+GSM1800:

TX-TX, TX-RX0.5m Gain=10dBi: 1m

Antenna fromtower2m

Diversity requirement:

GSM900: RX-RX ------4m(recommend

ed 6m)Antenna from

tower2m

GSM1800: RX-RX ------2m(recommend

ed 3m)Antenna from

tower2m

Directional antenna:

Required separation between TX-TX, TX-RX: 30dB

Antenna of the same sectorVerticalinterval

Horizontalinterval

Remark

GSM900: TX-TX, TX-RX 0.5m 4m No effect of theiron tower

structure inantenna

forwarding

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direction

GSM1800: TX-TX, TX-RX 0.25m 2m

No effect of theiron tower

structure inantenna

forwardingdirectionAdjacent sector antenna (placed on

the same platform)Verticalinterval

Horizontalinterval

Remark

GSM900: TX-TX/TX-RX ------ 0.5mGSM1800: TX-TX/TX-RX ----- 0.5m

Diversity requirement

GSM900: RX-RX ------4m

(recommended6m)

No effect of theiron tower

structure inantenna

forwardingdirection

GSM1800: RX-RX ------2m

(recommended3m)

No effect of the

iron towerstructure inantenna

forwardingdirection

GSM900 and GSM1800 are installed in flexible forms, but whatever the form,

GSM900 antenna and GSM1800 antenna shall meet the aforementionedrequirements for their respective interval.

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1.3 Link Budget

After the project parameters for the base station are specified, it is necessary to work

out a link budget in order to further estimate its coverage. At this moment, it isrequired to consider the sensitivity of the base station equipment selected. In mobilecommunication system, the wireless link is divided into uplink and downlink. Anexcellent system should implement power budgeting in design, so as to strike abalance between the uplink signals and downlink signals within the coverage area.Otherwise, if the uplink signal coverage is greater than the downlink signal coverage,and the downlink signals on the edge of cell are relatively weaker, such signals willeasily be engulfed by the strong signals from other cells; if the downlink signalcoverage is greater than the uplink signal coverage, the mobile station will be forcedto wait under this coverage, but the uplink signals are too weak and thus the voicequality is not good enough. Of course, balance is not necessarily absolute equality.From the survey report on Abis interface, we can judge clearly whether there is abalance between the uplink and downlink signals. Normally, when the level difference

between the uplink and downlink signals reaches the sensitivity difference betweenbase station receiver and mobile phone receiver, it is deemed that a balance isreached. However, as the fading of uplink and downlink channels is not totally thesame, and as a result of such factors as the difference in receiver noise deteriorationperformance, this difference will generally fluctuate within a range of 2-3dB.

1.3.1 Link Budget Model

Figure 5-5 Link Estimation Model

To figure out uplink and downlink balance, it is necessary to take into account of avery important component. The active parts of the bases station receiving system andthe thermal movement in RF conductor will cause heat noises, which reduce thesignal-to-noise ratio (S/N) of system reception, so that it restricts the base stationsensitivity from rising and reduces the communication quality. The principle for toweramplifier is to add a low noise amplifier at the front end of base station receivingsystem, i.e. close to the receiving antenna, so as to improve the receivingperformance of the base station.

In terms of technical principle, the tower amplification is to reduce the noise

coefficient of base station receiving system so as to improve the service quality inside

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the service area. In this way, it functions to improve the receiving performance of thebase station. The contributions made by the power amplifier to the uplink shall bedistinguished in light of the performance of its own low noise amplifier rather than onlybased on the gains. Normally, the uplink and downlink balance with amplifier addedshould be modified and worked out according to the test method for its practical

sensitivity.

I. No tower amplifier

Without a tower amplifier, the input interface of the multiplexer on top of the cabinetshould be taken as the reference point for sensitivity.

For a downlink signal link, the power of base station transmitter is Poutb, thecombiner loss is Lcb, feeder line loss is Lfb, base station antenna gain is Gab, theloss of space transmission is Ld, the mobile station antenna gain is Gam, thereceiving level of the mobile station is Pinm, its fading margin is Mf and the noisedeterioration at the side of mobile station is Pmn. Then it follows:

Pinm+Mf=Poutb-Lcb-Lfb+Gab-Ld+Gam-Pmn (1)

For uplink signal link, the output power of the mobile station transmitter is Poutm,base station diversity receives a gain of Gdb, the receiving level of the base station isPinb and noise deterioration at the side of mobile station is Pbn. In accordance withthe principle of reciprocity, the gain received and sent by the antenna is equal. Then itfollows:

Pinb+Mf=Poutm+Gam-Ld+Gab+Gdb-Lfb-Pbn (2)

Normally, PmnPbn, after consolidation, the following equation appears

Poutb=Poutm+Gdb+(Pinm-Pinb)+Lcb (3)

II. With tower amplifier

The tower amplifier input interface is taken as the reference point for sensitivity if

there is a tower amplifier. It is not necessary to consider the loss of uplink feeder line,thus Equation (3) will change to Equation (4):

Poutb=Poutm+Gdb+(Pinm-Pinb)+Lcb+Lfb (4)

1.3.2 Reference point for base station sensitivity

I. Definition of sensitivity

Receiver sensitivity refers to the minimum signal level needed to be input from thereceiver input terminal under the circumstances where the receiver meets certain biterror rate.

To measure receiver sensitivity aims to check the performance of receiver analog RFcircuit, intermediate frequency circuit, and modulation and decoder circuit.

Performances to measure receiver error bit rate are the three parameters includingFER, RBER and BER. When the function of bit error detection in the receiverindicates a frame is at fault, this frame will be defined as deleted. FER is defined asthe ratio of the deleted frames to the frames received. For full rate voice channel, thisis normally caused when 3-bit cyclic redundancy check (CRC) detects errors or badframe indication (BFI) arising from other processing functions occurs. For signalingchannel, this is usually caused when the Fire code (FIRE) or other group codesdetect errors. No definition of FER is available for data services.

RBER is defined as the bit error rate of those not announced as deleted frames. Thatis the ratio of number of bit errors in the fame detected as good to the total numberof bits transmitted in good frames.

Bit error rate (BER) is defined as the ratio of bit errors received to all the data bitstransmitted.

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As channel bit error rate is random, we normally measure the receiver bit error rate bystatistical measurement. That is, conduct several sample measurements on eachchannel. When the number of sample measurements is definite, and the bit error rategained from every measurement falls within a certain range of test errors, it isdeemed that bit error rate of this channel has met the requirement on bit error rate as

stipulated. The limit value of sampled number and test bit error should meet thefollowing requirements:

(1) For each independent sample test, the times through a bad unit should be keptas low as possible (probability lower than0.2%);

(2) For each independent sample test, there is a high possibility of passing through abad unit probability higher than 99.7%};

(3) The measurement involves the statistical characteristic of height;

(4) The time for test should be reduced to the minimum.

As a result, we can measure the receiver sensitivity by measuring if the receiver biterror rate meets the requirements as stipulated while inputting sensitivity level to thereceiver.

In light of different transmission conditions, the requirements for reference sensitivitylevel under two conditions are stipulated with respect to receiver sensitivity: staticreference sensitivity level and multi-path reference sensitivity level. Lets talk aboutthe requirements and measurement for these two kinds sensitivity level in GSMsystem as follows.

Static reference sensitivity level

Static reference sensitivity level of a receiver is the signal level added by a standardtest signal to the receiver input terminal. At this point, of the data produced afterreceiver demodulation and channel decoding, its FER, RBER or BER is better than orequal to the value stipulated under static transmission condition for a specified type ofchannel (such as FACCH, SDCCH, RACH and TCH).

Multi-path reference sensitivity level

Multi-path reference sensitivity level of a receiver is the signal level of a standard testsignal at the receiver input terminal. At this point, of the data produced after receiverdemodulation and channel decoding, its FER, RBER or BER is better than or equal tothe value stipulated under multi-path transmission condition for the specified type ofchannel (such as FACCH, SDCCH, RACH and TCH). Typical multi-path transmissionconditions include TU50 (at a urban car speed of 50km/h), RA250 (at a speed of250km/h in rural areas) and HT100 (at a speed of 100km/h in hill environment) etc.

Besides, attention should be paid to the following differences in defining thesensitivity: without diversity sensitivity, with diversity sensitivity; the difference in biterror and error frame indicator under the status of frequency hopping and nofrequency hopping.

II. Sensitivity test point in the event of tower amplifier

Fi

Figure 5-6 Sensitivity Test on Base Station with Tower Amplifier

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III. Sensitivity test point without tower amplifier

Figure 5-7 Sensitivity test of base station without tower amplifier

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1.4 Design of Coverage Area

In practical project planning, the effective coverage of base station is subject to the

following factors: effective transmitting power of base station, the work frequencyband (900MHz and 1800MHz) used, the type and position of antenna, power budget,wireless transmission environment and the coverage indexes required by theequipment buyer. Lets combine the requirement on service quality index for mobilecommunication network (for example), and through examples, give the coverage ofbase station theoretically under various coverage requirements.

Applicationenvironment

Minimumreceiving

power (dBm)Other indexes

Received by mobilephone, inside the

building

-70

Mobile phone sensitivity -102 dBm, fastfading protection 3dB, slow fadingprotection (indoors) 7dB (slow normaldivergency, indoor 7dB, outdoors 8dB,reachability of 90% within the coveragearea), penetration loss of 18dB,interference noise of 2dB, environmentalnoise fading protection 2dB.

Received by mobilephone, in a small

sleeper car orinside the room onthe first floor of anordinary building

-80

Mobile phone sensitivity -102 dBm, fastfading protection 3dB, slow fadingprotection 5dB, penetration loss of 10dB,interference noise of 2dB, environmentalnoise protection 2dB.

Outdoors -90

Mobile phone sensitivity -102 dBm, fastfading protection 3dB, slow fadingprotection 5dB, interference noise of 2dB,environmental noise protection 2dB.

Suppose:

GSM900 and GSM1800 base station antennas are both 30 metershigh;

The sensitivity of GSM900 2W (33dBm) mobile station is -102dBm, and-100dBm for 1800 1W (30dBm) mobile station;

The mobile station antenna is as high as 1.5 meters with a gain of 0dB;

When M900 uses CDU, its sensitivity is -110dBm; and M1800sensitivity is -108dBm;

CDU insertion loss is 5.5dB, SCU insertion loss is 6.8dB;

65-degree directional antenna gain is 13dBd (M900) and 16dBd(M1800);

The feeder line is as long as 50m, 4.03dBm/100 meters (900MHz), and5.87dB/100 meters (1800MHz);

Select Okumura transmission model;

Ordinary urban environment.

The calculation results are as follows:

(1) M900 outdoors coverage radius in urban areas

Mobile phone minimum receiving level is Pmrminminmin = 90dBm. Coverage radius shouldbe the maximum transmitting power of TRX. The maximum transmitting power of

M900 TRX amounts toPbt = 40

W (46dBm).

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The effective radiation power of base station antenna is:

EIRP= Pbt Lcom Lbf+ Gab = 46 5.5 2.01 + 13 + 2.15 = 53.65dBm

WhereLcom is combiner loss, Lbf is feeder line loss and Gab is the gain of base stationantenna,

and maximum transmission loss possible is:

Lp = EIRPPmrminminmin = 53.65 (90) = 143.65dB

According to Okumura transmission model as described above:

Lp = 69.55+ 26.16 lglgf 13.82 lglghb + (44.90 6.55 lglghb ) lglgdAh m

where hb refers to the height of base station antenna, hm is the height of mobilephone antenna, and f=900MHz.

Ahm = (1.1 lglgf 0.7)hm (1.56 lglgf 0.8) = 0.01dB

Substitute the above equation with each known member, and the result is d = 2.8km.

(2) M900 inside a building in urban area

Mobile phone minimum receiving level Pmrminminmin = 70dBm.


d = 0.75km

This indicates the base station can cover an area of 2.8km in radius, but for the userson the first floor of a building 750m away from the base station, the reception qualityfalls short of the requirement.

(3) M900 coverage radius in the suburbs

mobile phone minimum receiving level Pmrminminmin = 90dBm


Okumura transmission model for urban areas should be modified as follows:

Lp = 69.55 + 26.16 lglgf 13.82 lglg hb + (44.90 6.55 lglg hb ) lglg d

Ahm 2[lglg(f/28)]2 5.4

So d = 5.4km

It is obvious that in terms of the same configuration of base station, the coverageradius base station in the suburb is better than that in the urban area.

(4) M1800 outdoor coverage radius in the urban area

mobile phone minimum receiving level Pmrminminmin = 90dBm. As the maximum transmittingpower of M1800 TRX amounts to 40W(46dBm), the coverage radius should be themaximum transmitting power of TRX.

EIRP= Pbt Lcom Lbf+ Gab = 46 5.5 2.93 + 16 + 2.15 = 55.73dBm

Lp = EIRPPmrminminmin = 145.73dB

For1800MHz, Okumura transmission model is:

Lp = 46.3 + 33.9 lglgf 13.82 lglghb + (44.90 6.55 lglghb ) lglgdAhm

Besides, f = 1800 MHz, Ahm = (1.1 lglgf 0.7)hm (1.56 lglgf 0.8) = 0.04dB

Substitute the above expression with each known member, and the result will be d =1.7km.

(5) M1800 inside the room of an urban building

mobile phone minimum receiving level Pmrminminmin = 70dBm.

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d = 0.46km.

This indicates the base station is able to cover an area of 1.7km in radius, but for theusers on the first floor of a building 500m away from the base station, the reception

quality falls short of the requirement. The said results are summarized in the followingtable:

Application environmentTRX

transmittingpower (W)

Mobile phoneminimum

receiving power(dBm)

Coverageradius (km)

M900Inside the room

of a building40 -70 0.75

Outdoors inurban areas

40 -90 2.80

In the suburbs 40 -90 5.40

M1800Outdoors in

urban areas40 -90 1.70

Inside theroom of abuilding

40 -70 0.46

From the table, it is clear that the coverage of M1800 is less than that of M900 andthe coverage of an urban base station is less than that in the suburb.

1.5 Capacity Distribution

1.5.1 Voice channel distribution

The capacity of base station refers to the number of channels to be configured for a

base station or a cell. It involves the number of wireless voice channels and numberof control channels. According to the range of base station or cell and user densitydistribution, figure out the total number of users, and then according to the index forwireless channel call loss and traffic, refer to Erl B table and work out the number ofvoice channels to be configured.

(1) According to the bandwidth and multiplexing mode currently used for GSMnetwork within the planned area, we can get the maximum CF number to beconfigured with a base station;

(2) Each CF has 8 channels; minus the number of control channels, we will get themaximum number of voice channels to be configured with each base station;

(3) According to the number of voice number and call loss index (generally 2% fordense traffic area and 5% for other areas), refer to Erl B table, and get the maximum

traffic a base station is able to load (Erl number);

(4) Divide this Erl number by the average user traffic when busy, and you will get themaximum number of users a base station is able to satisfy;

(5) Using the data for user density, we may find out the coverage area of this basestation;

(6) When a region with different user density are specified, we can work out thenumber of base stations to be configured through the area of the region with this userdensity and the actual coverage area of the base station as known above;

(7) For important places, it is necessary to consider the backup of base station andthe realization of CF mutual aid function; at least two base stations are needed for animportant county and at least two CF for an important sector;

(8) For areas with possible bursting traffic (competition venues and seasonal tourist

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resorts etc.), the resources for equipment (carrier frequency, microcell etc.) andfrequency resources should be reserved in advance;

(9) Such dynamic factors as roaming ratio, user mobility factor, new servicedevelopment (GPRS, WAP and SMS etc.), industry competition, rate change, one-way toll and economic growth should be taken into account;

(10) To configure a base station, it is necessary to consider ABIS interfacetransmission, such as the use of ABIS interface at 15:1 and 12:1 and cascading etc.,and save transmission while meeting the capacity;

(11) Actively adopt cellular system plus distributed antennas to meet the urbancoverage and capacity; use economical micro base stations to provide coverage forrural areas and high roads and use HDSL for transmission in these areas;

(12) Reserve in advance some CF, micro cells and micro base stations to cover newlydeveloped areas and for the selection in the optimization period;

(13) In some special areas, base stations made up of omni-directional/directionalmixed cells can be used to give full reign to their respective edges in coverage andcapacity. In this case, attention should be paid to the separation between the omni-

antenna and directional antenna. Installation in light of layers is preferred; in terms oftraffic control, algorithm in light of layers can be used for control;

(14) For some highroads requiring little traffic but large coverage, we may resort to0.5+0.5 cell networking mode with single CF micro base station + power divider + twosets of directional antennas.

Erl traffic model is used to work out the traffic density a network is capable of bearing.Call loss may be 2% or 5% in light of practical conditions. Erl B table is shown asfollows:

CF number foreach cell

TCHnumbe

r

Traffic (Erl)

2% 5%

1 6 2.27 2.962 14 8.2 9.73

3 21 14.03 16.184 29 21.03 23.825 36 27.33 30.65

6 44 34.68 38.557 52 42.1 46.53

8 59 48.7 53.559 67 56.25 61.6310 75 63.9 69.73

From the above table, we can see that the larger the number of cell CF, the large thecall loss rate. The larger traffic each TCH is able to bear, the higher utilization rate ofTCH channel is. Channel utilization rate is an important indicator for assessing the

quality of planning and design. If the number of users in a base station is too small,the construction unit will generally consider delaying the construction of this basestation. As a result of the limit on cell coverage and usable frequency bandwidth, it isnecessary to plan the cell capacity in a rational way in an effort to improve thechannel utilization rate under the precondition of ensuring sound voice quality. Inconsidering the share of traffic between these two in constructing a dual frequencynetwork, wider frequency bandwidth can be used to realize high utilization rate of thechannel.

It is discovered in practical application that when the actual traffic via each line of abase station cell reaches 85%90% of TCH traffic (call loss 2%) given in Erl B table,the probability of congestion in this base station cell will obviously rise. As a result, wegenerally take 85% of the traffic as defined in Erl B table as the reference for thetraffic density a computer network is able to bear. These data estimated for traffic

capacity needs to be counted and completed gradually in the course of network

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construction.

I. Example:

The capacity of local network requires expansion. In accordance with service

development and in combination of population growth and network popularization,users will reach 100,000 in 2 years; considering roaming factor (according to trafficstatistics and development trend) 10%, mobile factor (It mainly refers to the usersmoves within the local network instead of roaming) 10%, dynamic factor 15% (withbursting traffic considered), then we know that the network capacity as required is 10*(1+10%+10%+15%)=135,000; however, in consideration of congestion, we generallyuse 85% of the traffic as given in Erl B table as the reference for the traffic densitythat the computer is able to bear; as a result, the designed network capacity is 13.5/(85%)=158,800, i.e. 160,000.

1.5.2 Configuration of control channel

I. SDCCH distribution

In GSM system, most of the time during the general call creation process andposition update process, the mobile station works on SDCCH channel. The followingtable is the configuration principles recommended for SDCCH.

TRX number

Generalconfiguration(SDCCH/8 +SDCCH/4)

Configuration of theedge of location area

Generalconfiguration

(use Immediateass. on TCH)

1 SDCCH/4 SDCCH/4 SDCCH/4

2 SDCCH/8 SDCCH/8 SDCCH/4

3SDCCH/8 +SDCCH/4

SDCCH/8 + SDCCH/4 SDCCH/8

4SDCCH/8 +

SDCCH/42*SDCCH/8 SDCCH/8

5 2*SDCCH/8 2*SDCCH/8SDCCH/4 +SDCCH/8

6 2*SDCCH/8 2*SDCCH/8+SDCCH/4 2*SDCCH/8

72*SDCCH/8+SDC

CH/43*SDCCH/8 2*SDCCH/8

8 3*SDCCH/8 3*SDCCH/8SDCCH/4 + 2 *

SDCCH/8

It is very difficult to sum up a traffic model for SDCCH channel. In particular, it evenbecomes almost impossible to do so after the large-scale application of layerednetwork and short messages. Fortunately, the equipment of some manufactures atthe present supports SDCCH dynamic allocation. SDCCH channel dynamic allocationenables the dynamic adjustment of SDCCH capacity, so as to reduce the congestion

of SDCCH channel congestion, reduce the effect of SDCCH channel initialconfiguration on system performance and increase the system capacity. This functionmainly involves the following aspects: dynamic allocation from SDCCH to TCHchannel and restoration from SDCCH to TCH channel. Use dynamic allocationalgorithm, and determine whether to perform dynamic configuration according to theinput parameters: at a point when the cells SDCCH chancel is busy and the numberof idle TCH channels exceeds a certain value, then the idle TCH channels will beconverted to SDCCH channels according to corresponding setting. After a while,when the cells SDCCH channel stays idle, BSC will restore SDCCH channeldynamically allocated to TCH channel.

II. CCCH allocation

Public control channels mainly include AGCH, PCH and RACH intended to sendaccess grant (i.e. immediate assignment) and paging message. All service channels

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of each cell share CCCH channel. CCCH channel may either share the samephysical channel (one time slot) with SDCCH or solely use a physical channel. Therelated CCCH channel parameters include the following: [CCCH configuration],[number of access grant reserved channels], [frame number coding between identicalpaging].

[CCCH configuration] serves to designate the type of CCCH channel configuration,i.e. Whether to share a physical channel with SDCCH channel. In the case of 1 or 2TRX in the cell, it is recommended that CCCH channel occupy one physical channeland share it with SDCCH; in the case of 3 or 4 TRX, it is recommended that CCCHchannel occupy one physical channel and does not share it with SDCCH channel; inthe case of more than 4 TRX, it is recommended to work out the capacity of pagingchannel in CCCH and perform specific configuration.

[number of access grant reserved channels]decides the ratio occupied by pagingchannel and access grant channel on CCCH. The two parameters of [number ofaccess grant reserved channels] and [CCCH configuration] determine the capacity ofaccess grant channels. The value of [number of access grant reserved channel} inprinciple is: on the precondition of ensuring the access grant channel is not

overloaded, minimize the said parameter as much as possible in order to shorten thetime for mobile station to respond to paging, so as to improve the serviceperformance of the system.

[frame number coding between identical paging]decides how many paging sub-channels the paging group of a cell is divided into. In this way, along with [CCCHchannel configuration] and [number of access grant reserved channels] jointlydetermines the total number of paging sub-channels in a cell. As each subscriber tothe mobile station (corresponding to each IMSI) belongs to a paging group, everypaging group in each cell corresponds to a paging sub-channel. The mobile stationwill work out the paging group where it belongs in light of its own IMSI. After that, itworks out the position of the paging sub-channels belonging to the said paging group.In practical network, the mobile station only listens in the contents in the paging sub-channel it belongs to with no regard to the contents in other paging sub-channels.

1.6 Location Area Design

1.6.1 Definition of location area

Under GSM protocol, the entire mobile communication network is divided intodifference service areas in light of different location area codes, and the network callsthe entire location area in order to call the mobile user. The functions of a locationarea are described as follows: call connection with mobile users should be created atthe side of network. It is necessary to record the location information about the saidmobile user at any time, so that the user may be called when necessary. The basicinformation about the current location of local registered users (information about

MSC/VLR where the user is connected) is kept in the equipment at network side;MSC/VLR, the equipment at network side, keeps the basic information and locationinformation about all the mobile users stationed currently under this MSC (informationabout specific location area); SIM cards of mobile subscribers store the locationinformation of these users (specific information about location area). When a mobilestation is in service, after locked to a broadcast channel, compare the locationinformation, that is, compare to check if the location area information stored in SIMcard is consistent with that delivered by the broadcast channel. If inconsistent, themobile station will start up location update. The task of location update is to registernew location area in the current MSC/VLR. If MSC/VLR is discovered to havechanged, it is then necessary to send signaling to the registration place to modifyMSC/VLR information in HLR and delete old MSC/VLR information. When the mobilestation is in standby state, it will continuously intercept the location area information of

broadcast channels. Once it discovers the location information in SIM card is

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inconsistent with the location information delivered by the broadcast channel, it willstart up location update without delay. When the mobile station is in communicationstate, it will intercept the location information delivered by an associated channel.When it discovers the location information stored in SIM card is inconsistent with theinformation delivered from the associated channel, after the communication is over, it

will start up location update immediately. To ensure the paging to mobile subscriber isnot lost, it is requested that the location information kept in HLR, VLR and SIM card isconsistent with each other at any time.

Location area is a basic unit underlying GSM system, that is, the paging message willbe delivered on the basis of location area with the paging messages of one mobileuser in the location area delivered to all the cells. One location area may include oneor multiple BSC but it belongs to a single MSC, as shown in Figure 5-8.

PLMN

MSC

C E L LLA

C E L L

C E L L

C E L L

C E L LLA

C E L L

C E L L

C E L L

MSC

C E L LLA

C E L L

C E L L

C E L L

C E L LLA

C E L L

C E L L

C E L L

Figure 5-8 Division of service areas

1.6.2 Division of location areas

To specify the location of a mobile station, the coverage of each GSM PLMN will bedivided into many location areas. The size of location area (i.e. coverage of onelocation area code LAC) is a very key factor in the system. The following is theprinciples for location area planning:

(1) Location area cannot be divided into over large or over small areas.

If LAC covers a too small area, the mobile station will undergo an increase in locationupdate processes, thus increasing the signaling flow in the system; on the contrary, ifthe location area covers a too large range, then the same paging message in thenetwork paging mobile station will be delivered in many cells, thus leading to theoverload of PCH channel, and increasing the signaling flow at Abis interface. Thecalculation of location areas is related to the paging strategies of differentmanufacturers. Refer to calculation of location area as described in the next section

for details. Generally, it is recommended that the number of TRX in each location areais around 300. In the initial stage where the network is first constructed, as there is nomuch traffic, the number of TRX one LAC is able to accommodate may be greaterthan this value; however, it is very necessary to monitor PCH load and traffic growthin the long run. Of course, to add a slave BCCH channel may increase PCH capacityeffectively at a sacrifice of one voice channel.

(2) Perform LAC area division in light of the geographic distribution and action ofmobile subscribers, so as to reach the goal that there is fewer location updates on theedge of the location area.

In the event of discontinuous coverage between the suburb and the urban area, it islikely that mobile phone fails to perform location update when the update time is dueat the cyclic position. After the protection time (generally set in MSC) the system willconsider IMSI undergoes hidden separation. If this goes to the urban area, the LAC inthe urban area is consistent with that in the suburb, and then some mobile phones will

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not perform normal location update immediately. Thus there arise some signals,which are not in the service areas. As a result, in allocation of location arrears, thelocation areas used for ordinary suburbs (counties) are different from those in urbanareas. For this reason, the location areas are distributed in the way of a concentriccircle (the urban area in the inner circle may be divided into several location areas

due to capacity factor. Inside the circle, the division may adopt the method in light ofsections or another inner and external ring or mixed way), so as to avoid the abovephenomena. Practice has proved that the LAC division in this way may not onlydecrease users not in the service area but also improve the completion rate and callsuccessful rate, as shown in Figure 5-9:

Figure 5-9 Diagram of LAC Division

In addition, in big cities with high traffic, if there are more than two location areas,such geographic factors as mountains and rivers in the urban areas can be used asthe boundary of location areas, so as to reduce the overlapping depth of differentcells under the two location areas. In the event of no such geographic environment,streets should not be taken as the boundary for dividing location areas, and theboundary shall not put in a place with high traffic (such as shopping malls). Generally,it is required that the boundary of location area should not be parallel or perpendicularto the streets but in oblique crossing. In the areas where the urban area meets thesuburb, the boundary of a location area should be located at the place of base stationon the outskirts, instead of at the place where the city proper adjoins the suburb withdense traffic, so as to avoid the users in this area updating their locations veryfrequently.

A dual-frequency network requires more in respect of location area division. Here issome experience in the construction of a dual-frequency network with regard to thedivision of location area:

(1) If M1800 and M900 use a MSC separately, their location areas will surely differ. Itis required to make the mobile station stay in M1800 cell, which absorbs traffic bysetting parameters, so as to reduce the switch and repeated selection between thetwo frequency bands. At the same time, the load brought to the system arising fromlocation update should be taken into full account in designing signaling channels.

(2) If M1800 and M900 share in one MSC, in the initial period of network construction,as long as the system capacity permits, it is recommended to use the same location

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area; if it is necessary to divide it into two or more location areas due to limited pagingcapacity, there are two ways of design: divided in light of geographic locations andfrequency bands. Refer to Figure 5-10 and Figure 5-11 for details.

Figure 5-10 Divide Location Areas in Light of Frequency Band

900 Cell 900 Cell900 Cell900 Cell

1800 Cell 1800

LA1 LA2

Divide location areas in light of geographic locations

1800 Cell 1800 Cell 1800 Cell 1800 Cell

900 Cell 900 Cell900 Cell900 Cell

1800 Cell 1800

LA1 LA2

Divide location areas in light of geographic locations

1800 Cell 1800 Cell 1800 Cell 1800 Cell

Figure 5-11 Divide Location Areas in Light of Geographic Locations

To divide location areas in light of frequency band requires setting parameters inconsideration of frequent update due to the switch and repeated selection betweentwo frequency bands, so that the mobile station will remain in M1800 cell, whichabsorbs traffic, so as to reduce the switch and repeated selection between the two

frequency bands. At the same time, the load brought to the system arising fromlocation update should be taken into full account in designing signaling channels. Todivide location areas in light of geographic locations may serve to solve the problemof frequent location update arising from dual frequency switch and repeated selection,but it is necessary to modify the office data of the previous M900 network. At thesame time, on the boundary of a location area, there exist the location updatescaused by the switch and repeated selection at the same frequency band and dualfrequency band, thus there is much signaling flow, it is required to design the locationarea boundary carefully.

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1.6.3 Calculation of location areas

I. For non-combination BCCH

(1) Purpose

Work out the number of users or CF number one location area accommodates.

(2) Prerequisite

(a) All the cells are configured with a non-combination BCCH

(b) Number of reserved access grant blocks is A

Note:

Paging block is 9-A

1 frame=4.615ms, 1multiframe=51frame=0.2354s, that is, there are1/0.2354=4.25 frames within 1 second; the number ofpaging blocks is: 4.25(9-A)

(c) The number of paging messages in each paging block is B:

Note:

Paging times each paging block is able to deliver;

Ratio of TMSI to IMSI in paging

X(Y/(Y+1))1 paging sub-block +X(1/(Y+1))2 paging sub-block = 4

Message sub-block number of each paging X=4(Y+1)/(Y+2)

(d) Paging resending ratio is C

(e) Time length of average call is D (unit: second)

(f) Caller: called: received point-to-point short message = E: E: F

Note:

Each paging block consists of 23 bytes, which can send:

2IMSI pages;

2 TMSI and 1IMSI page;

4 TMSI pages

Call times corresponding to each page (caller or called) is: (2*E)/(E+F)

(g) Traffic of each user when busy G (unit: Erl)

(h) In consideration of the distribution of paging commands, we think when it exceeds30%, the paging channel will undergo congestion.

(i) Each TRX has 7.2 TCH on the average, and the maximum of traffic ofeach TRX on the average within 1 hour is 7.2

(3) Formula

Traffic in each location area: 4.25(9-A)B30%2ED/[(E+F)C]

Number of users in each location area: possible traffic in each location area/G

CF number in each location area: possible traffic in each location area/7.2

Note:

If some CF does not aim to improve traffic but to meet its coverage, thenumber of CF it can support can be improved;

If short messages burst suddenly, then the paging amount will increasewith supported users on the decline, which may require flow controlprotection;

Traffic models in different areas and different periods are different, so

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each parameter should be submitted with different value.

(4) Example

If the number of reserved access grant blocks is 2, then 1 multiframe has (9-2)=7paging block and 4.257=29.7 paging blocks can be sent within 1 second.

Suppose IMSI and TMSI paging occupies half, then each paging block is able to send8/3 pages.

Then a maximum of 29.78/3 = 79.2 pages may be delivered within 1 second.

That is, 79.2360030%=85536 pages can be delivered within 1 hour.

Suppose MSC paging resend ratio is 1.1, i.e. it supports 85536/1.1 = 77760 pages.

Suppose the duration of each call is 60S, then the traffic for 1 call is60/3600=0.017ERL.

Suppose caller: called: short message (received) = 5:5:1,

Then 0.017ERL corresponds to 6/10 page, and it may support 57024 calls.

77760/0.60.017=2203.2ERL

If the traffic for each user when busy is 0.03, it may support 2203.2/0.03=73440users,

And supports CF of 2203.2/7.2=306TRX.

II. For combined BCCH, supported number of CF will decrease.

III. For multiple BCCH, the number of supported CF will increase.

With a view to different traffic density, it is recommended to combine BCCH cells,BCCH cells and multiple BCCH cells to make up a location area separately.

Generally speaking, it is necessary to consult with the operators in respect of theplanning for location areas for specification. Domestically, Numbering Rules and Post& Telecommunications 900-1800 Technical System should be the reference for

principles for CGI and CI coding.

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1.7 Design of Indoor Coverage System

Currently, the indoor coverage mainly depends on the extension of existing outdoorcoverage, such as the mode of direct station, outdoor high-power base station and

highly installed antenna. However, these solutions will lead to the following problems: As wall penetration involves a large loss and indoor coverage renders

bad effect, there will be a large number of blind spots impossible forcommunication.

Direct station mode requires much on source level and both theintermodulation interference and co-frequency interference are seriousin bad communication quality at high rate of call drops.

Capacity problem fails to be solved fundamentally. The networkcapacity is limited at a low call successful rate.

It affects the planning of frequency for the entire network. It is difficult toincrease the network capacity.

Serious detached island effect

As a result of quality and capacity, the development of value-addedservices for group users is restricted (such as GPRS data service)

To improve the service level, it is urgently needed to solve the problem of indoorcoverage. In the design intended for a solution to indoor coverage, we need toconsider the following problems:

Try to avoid the effect of newly-built indoor system on the existingnetwork, so as to distinguish indoor from outdoor

How to provide sufficient indoor network capacity

Support new services and new functions

Here is an analysis in terms of design of indoor antenna system, capacity design and

frequency plan.

1.7.1 Design of indoor antenna system

I. RF design

(1) Link budget

For indoor coverage, the formula for link budget is as follows:

Pant = MSsens +RFmargargarg +IFm argargarg +BL +LNFm argargarg +Lpath Gant

Pan t=antenna input interface powerPan t=antenna input interface power

Ssens=

104dBmequipment receiving sensitivitySsens=

104dBmequipment receiving sensitivity

RFm argargarg=

rayleigh fading marginRFm argargarg=

rayleigh fading margin

IFm argargarg=access margin (dependent on environment)IFm argargarg=access margin (dependent on environment)

LNFm argargarg=design access, generally 5dBLNFm argargarg=design access, generally 5dB

B L= 900MHz5dB1800/1900MHz3dBhuman body lossB L= 900MHz5dB1800/1900MHz3dBhuman body loss

Gant=antenna gainGant=antenna gain

Lpath=Path loss

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Where path loss Lpath is:

Lpath32.5+20logd (km)+20logf (MHz)+

In the formula:

Free space loss Lp32.5+20logd (km)+20logf (MHz)

: Loss of other objects, floor and impediments; here are values of some typicalpenetration loss:

Partition wall block: 5~20dB

Floor block:20dB

Block of furniture and other impediments: 2~15dB

Thick glass: 6~10dB

The penetration loss of train carriages: 15~30dB

Penetration loss of lifts: 30dB or so

Loss of signals from fixed signal source at the track curve of tunnels:10~40dB /km

Loss of oblong tunnels: 10~15dB/km

The loss of column tunnel is 35~40dB/km, and thus tunnels usually usedisclosure cables for coverage

During the course of link budgeting, it is necessary to take the following key factorsinto account: in an indoor multi-antenna system, the link budget for test points isusually based on the link with minimum path loss; in the same coverage area, it isensured if possible that the effective radiation power (EIRP) of each antenna interfaceis consistent with its error kept within 10dB; the level of designed level is quite high,and thus it is not necessary to use antenna diversity to improve the density of uplinksignals; to reduce uplink interferences, it is necessary to configure the maximumtransmitting power for mobile phone and meanwhile enable the function of dynamic

power control of the mobile phone; in link budgeting, it is necessary to preserve somemargins in preparation for design error correction and the extension of antennasystem in the future; in estimating and designing interference margins, the marginswill differ in light of the distance away from the external walls of the building. Thecloser to the external wall, the designed interference margins will be larger.

(2) Service quality design (degree of being interfered)

The degrees of being interfered in respect of an indoor cell are described as follows:

The building where the indoor cell is located is at the sameheight as the surrounding buildings;Frequency multiplexing 12

The outdoor system covers the area where indoor cells arelocated not effectively;

The indoor system possesses dedicated frequency involvinglittle cell frequency multiplexing.

Littleinterference

The use of environment and frequency between the twoGeneralinterference

The building where indoor cells are located is a high-risecompared with the surrounding buildingsFrequency multiplexing 9

Degree ininterference

The actual interference level will vary with the change of network layout and the freshplanning of frequency; the actual interference level can be obtained through field test.

(3) Service quality design (interference design margin)

The higher the interference degree is, there are more interference design margins(IFmarg) within the said area, and the higher the level that mobile phone needs toreceive, as shown in the following table. What needs to be noted is, in adoptingindoor dual-frequency system, the mobile phone will receive the designed level

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according to the indexes as defined in 1800 system.

Actual level interference degreeReceiving level the mobile phone requires(dBm)

Major interference degree -65Medium interference degree -75

Minor interference degree -85

II. Antenna system design

The concept for the design of indoor distributed system is as follows: first survey thetype, structure, indoor structure, interference environment and service targets(general public/business group users) with respect to the building, and then analyzethe path loss; set antennas in light of different areas (type, number and place forinstallation). Hereunder are the antenna design guidelines for some typical areas:

(1) Guideline for the antenna wiring in a single cell

When a single cell achieves the building coverage, each antenna should beconfigured to ensure the equal distribution of signals within the coverage area of thecell. Generally, it is recommended to install the antennas in a zigzag way, as shown inFigure 5-12.

Figure 5-12 Guideline for Antenna Wiring in a Single Cell

(2) Antenna Wiring Guideline for Multiple Cells

When multiple cells achieve the building indoor coverage, it is necessary to note thatthere must be some interval between co-frequency multiplexing cells. Each antenna

should be configured likewise to ensure the equal distribution of signals within thecoverage area of the cell. If it involves compact frequency multiplexing, to ensuresound service quality, it is generally recommended to install the antennas betweendifferent layers in the same position, as shown in Figure 5-13.

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Figure 5-13 Guideline for Antenna Wiring in Multiple Cells

(3) Antenna layout in a closed environment

When the exterior wall of the building is relatively thick, then the signals attenuategreatly with little disclosure and little interference from outdoor co-frequency, thus thefrequencies between floors can be planned with ease, as shown in Figure 5-14.

Figure 5-14 Antenna Layout in Closed Environment

(4) Antenna layout in a half-open environment

If the exterior wall of the building is built of a structure of glass window/wall, there willbe little signal attenuation. If the inside of the building is an open meetingenvironment, it will suffer large interference from outdoor co-frequency, thusnecessitating dedicated frequency for planning; or multi-antenna system with lowoutput power is adopted for this purpose, where the cell edge is confined to inside thebuilding, as shown in Figure 5-15.

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Figure 5-15 Antenna Layout in Half-open Environment

(5) Antenna layout for building of frame structure

When the building has many interior walls and these walls are thick, thus requiringthat the antennas are installed in the corridor, the output power of the antenna isgenerally large so as to ensure sound coverage. In this case, some signals will leakthrough the corridor windows. It requires dedicated frequency for planning. Theinterval between the co-frequency cells of different floors is larger than that in otherenvironments, as shown in Figure 5-16.

Figure 5-16 Antenna Layout for Buildings of Frame Structure

(6) Antenna layout for office buildings

For such areas as offices of indoor business groups that require high service quality,multiple directional antennas and omni-antennas are generally adopted for indoorcoverage. Rational design of effective cell radiation power will easily serve to controlthe cell coverage, and thus having little interference against the outside, as shown inFigure 5-17.

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Figure 5-17 Antenna Layout for Office Buildings

(7) Antenna Layout for Parking Lots

Such areas as parking lots, which require some coverage but have no special need ofcapacity, the receiving level of mobile phone is not required to be high (around-90dBm). The key coverage areas are the lifts with large passage of people,

automatic moving stairs and entrance to parking lots, as shown in Figure 5-18.

Figure 5-18 Antenna Layout for Parking Lot

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(8) Supermarket

Such areas as supermarkets have some requirements in terms of both coverage andcapacity, and the antenna system in these places may be set in light of the actualbuilding structure, as shown in Figure 5-19.

Figure 5-19 Antenna Layout for Supermarkets

III. Survey

Finalize the installation and wiring of antenna through survey, involving the followingaspects:

Area of coverage in detail, requirement of signal coverage quality,different from place to place;

The distribution of existing signals in coverage area; understand theblind spots, hot spots and signal point of impingement;

Composition of buildings in the coverage area; block against signals;

Access position and mode of signals;

Examine the positions where equipment can be installed.

The topological structure, wiring diagram of the final output system, list of materials Inparticular, it should be stressed that omni-antennas are generally installed at thecenter of the ceiling, while the small directional antennas are installed, hung on theexterior wall with its near side radiating indoors, so as to minimize its effect onoutdoor system, and meet the C/I requirement on outdoor system.

If possible, coverage test may be conducted, as shown in Figure 5-20; in accordancewith the test result, adjust the initial antenna design to meet the coverage

requirement; or plan the frequency anew to meet the requirement on voice quality.Normally, if the radiation power of antenna interface is 10dBm, a small indoor omni-

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antenna of 2dBi should be used. In this case, within the range of 30m of the antenna,if there are no dense partition walls, the coverage level may reach -70dBm.

Figure 5-20 Diagram of Coverage Test

IV. Reduce switch from inside to outside through traffic control

The measures are as follows: in Idle status, set CRO and TO etc., to ensurereasonable reselection relationship in the cells indoors and outdoors; as the indoorhigh-rise coverage system with desirable indoor coverage may be regarded

independent of the outdoor system, it is only required to consider the switchrelationship between indoor cell and external cell at the entrance to the building, so asto ease the impact of the switch and external network. At this moment, the prioritylevel of indoor cells may be set higher, so that all the traffic whose level is higher thana certain switch threshold between layers is kept in the indoor cell, while the inter-layer switch threshold and magnetic hysteresis can be specified and adjusted in lightof practical conditions about the network (coverage, interference etc).

1.7.2 Capacity Analysis and Design

Before capacity analysis, it is first required to specify the type of indoor service areas,as shown in the following table:

Type of indoor servicearea Features of the service area Example

Public service area

It is rather difficult toestimate the traffic, for theaverage flow by the day andat night will differ indifferent periods. It isnecessary to take thecharacteristic of unequalcapacity distribution andbursting in a comprehensiveway. However, GOS and thetraffic of each user can bereferred to in accordancewith the outdoor cells.

Airport, shoppingcenter and sports

field etc.

Business service area The utilization rate of the Office buildings, star

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previous fixed telephonenetwork stands high, wherethe traffic is relatively fixedeasy for estimation, but theservice quality is required tobe high. Generally, GOS is1%, and the traffic of eachuser is also high, up to0.1Erl.

commercial hotels

Power

divider

Power

divider

Distributed

antenna system

Distributed

antenna system

Distributed

antenna system

Distributed antenna system



Power

divider

Power

divider

Distributed

antenna system

Distributed

antenna system

Distributed

antenna system




Figure 5-21 (a) Diagram of a Single Cell (b) Diagram of VerticalDivided Multiple Cells

As shown in Figure 5-21, the current distributed system is organized in two cell ways:single cell and vertical split. The former is applicable to indoor coverage requiringsmall capacity, while the latter is applicable to areas with dense indoor traffic.

Likewise, when the capacity for indoor single cell falls short of requirement, it is alsonecessary to perform cell split. But this is vertical split way. In the event of vertical cellsplit, the original single cell is required to split into at least 3 cells so as to ensurefrequency multiplexing; co-frequency cell is generally to be separated at an interval offour layers, as shown in Figure 5-22. To avoid frequency interference, indoor cellshould be prevented from splitting.

Frequency A

Frequency B

Frequency A

The cell frequency for

different floors can be

multiplexed, but there is a

certain space between

them.

Frequency A

Frequency B

Frequency A





them.

Frequency A

Frequency B

Frequency A





them.

Figure 5-22 Vertical Cell Split

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1.7.3 Frequency Plan

If dedicated frequency is adopted indoors, the frequency planning is relatively simple.Generally speaking, the frequency multiplexing for business service areas and publicservice areas is basically the same. If the frequency resources permit, dedicated

frequency band should be adopted for indoor coverage; if the frequency resourcesare not enough, stealthy frequency should be used. As a result of quality and capacityfactors (such as the development of GPRS high rate data services

chapter5 design of wireless network

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