Siemens Appendix-C: Fundamentals of Radio Network Planning

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Objectives of Radio Network Planning

To provide service

to many subscribers with high service quality at low costs

Capacity for a traffic model

� service types

� call rate

� mobility

Quality of service

� low blocking

� low wait time

� high speech quality

� low call drop rate

Efficiency

� low number of BS sites

� high frequency re-use

Boundary conditions

Physics: frequency spectrum, radio propagation � coverage & frequencyplanning

System: receiver characteristics, transmit power

channel configuration

cell design & network structure

link quality improvement

focal point of this course !

algorithms and parameter setting

Fig. 1


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As shown in the figure below, the main topic of this course is adjustment of systemparameters for the Siemens Base Station System (SBS) as part of the radio networkplanning process.

Before going into the details of the system features and control parameters, thisintroduction chapter summarizes some basics on radio network planning:

In the first and second section of this chapter the steps within the radio networkplanning process are explained. In sections 3 - 5 simple models concerning radiopropagation, frequency re-use and teletraffic are presented.

As each model they are only an approximation of reality. Nevertheless

� they reflect the main physical effects,

� they help to understand the meaning of parameters and the way of working thealgorithms,

� they allow to estimate parameter values.


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1 Mobile Radio Network Planning Tasks


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The mobile radio network is the connecting element between the mobile telephoneusers and the fixed network.

In this network the base transceiver station equipment (BTSE) is the directinterface to the subscriber. It has to make radio communication channels available tothe users and to care for a satisfactory signal quality within a certain area around thebase station. This area may be split into different sectors (cells) which belong to oneBTSE.

Planning a mobile radio network is a complex task, because radio propagation alongthe earth surface is submitted to many influences due to the local environment.Furthermore the performance requirements to a radio network cover a wide field ofapplications which depend on the operators potentialities and goals. To respond to allthese subjects, it is necessary to observe a certain sequence of tasks.

The first step is to get knowledge about the customers/operators objectives andresources (basic planning data). On this basis it is possible to estimate the size of theproject and to establish a coarse nominal cell plan.

Then it is necessary to install a digital terrain data base into a planning tool whichcontains topo-graphical and morphological information about the planning region.This digital map permits to make more accurate predictions about the radio signalpropagation as compared to the first rough estimation, and to create a more realisticcell structure, including the recommendable geographical positions of the basestations equipment(coarse coverage prediction).

The network elements defined up to this moment have been found on a more or lesstheoretical basis. Now it has to be checked if the envisaged radio site locations mayreally be kept. A site survey campaign in accordance with the customer, who isresponsible for the site acquisition, must clarify all problems concerning theinfrastructure and technical as well as financial issues of the BTSE implementation.Inside a tolerable search area the optimum site meeting all these issues has to beselected.

This site selection should also take into account particular properties of the area,e.g. big obstacles which are not recognizable in the digital maps.

Field measurements, to be carried out in typical and in complex areas must givedetailed informations about the radio characteristics of the planning region. Themeasurement results will then help to align the radio prediction tool for the actual typeof land usage (tool tuning).

Now, fixed site positions and an area-adapted tool being available, it is possible tostart the detailed radio planning. The final network design has to care for bothsufficient coverage and proper radio frequency assignment in respecting the trafficload and the interference requirements.

The last planning step is the generation of a set of control parameters, necessary tomaintain a communication while a subscriber is moving around. These parametershave to comply with the existing cell structure and the needs to handle the traffic loadexpected in each cell.


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After commissioning of the network, the performance must be checked by thenetwork operator by evaluation of statistical data collected in the operation andmaintenance center. Situations of congestion or frequent call rejections may betreated by modification of the pertinent control parameters and lead to an optimizednetwork.

The individual planning steps are considered more closely in the following sections.

1.1 Collection of Basic Planning Data

The requirements of the network operator concerning traffic load and service areaextension are basic data for the design of a mobile network . A coarse networkstructure complying with these requirements can be created on this basis.

Two fundamental cell types are possible; their properties may be determined

a) by the maximum radio range of the involved transceiver stations and mobileterminals; the range is limited by the available transmit power and the noise figureof the receivers. This type is called a noise limited cell; it is typical for rural regions.

b) or it may be determined by the limited traffic capacity of a cell in the case ofhigh subscriber concentration. This leads to the implementation of small cells,mainly in urban areas where interference will become the major problem.

The result of this first planning step is a rough estimate of the network structure,called a nominal cell plan, which gives knowledge about the number of radio stations,their required technical equipment and their approximate geographical positions.Thus allowing to assess the monetary volume of the project.

1.2 Terrain Data Acquisition

Mobile communication occurs in a natural environment. The radio signal propagationis highly affected by the existing terrain properties like hills, forests, towns etc.Therefore the real mapping data must be taken into account by the planning tool.

The signal level encountered by a subscriber in the street is influenced by absorbing,screening, reflecting and diffracting effects of the surrounding objects and along theradio path.

To make realistic signal level predictions, the propagation models implemented in theprediction tool must be fed with the relevant terrain data.


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A very important factor for correct modeling is the morphographic classification of anarea :

� building heights and density of built up areas (metropolitan, urban, suburban,village, industrial, residential) or forest, parks, open areas, water etc.

The screening by hills which may affect the coverage of a service area must be madeevident by consideration of the terrain profile (height contour lines).

The procurement of digital maps with these informations may be rather expensive.The prediction accuracy is directly related to the size of area elements (resolution)and to the reliability of these information (obsolescence of maps!)

1.3 Coarse Coverage Prediction

On the basis of the digital terrain data base and by using standard propagationmodels, which have been preselected to fit for special terrain types, it is possible tomake field strength predictions without having a very detailed knowledge of theparticular local conditions.

By variation and modification of the site positions and antenna orientations, coveragepredictions of rather good quality may be attained.

Yet, the definitive site locations are subject to a later scheduled site selection processin accordance and by cooperation with the customer.

The particular local characteristics must be introduced later by comprehensive surveymeasurements. These measurements will be used to upgrade the propagationmodels.


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1.4 Network Configuration

The results of the “coarse prediction“ steps will allow to define the radio networkconfiguration and the layout of individual base stations.

A first frequency allocation plan may also be derived from these predictions. Theresult might already be a well functioning network. But it is still based onassumptions. The actual impact of the natural environment must be considered in thefollowing steps. Nevertheless, the “coarse planning“ results will help to better assessthe special details brought in by the real situation.

In designing the radio network one has to keep in mind the requirements emergingfrom an increasing subscriber number. A multiple phase implementation plan has togovern the network configuration concepts.

In the initial phase a relatively low number of users has to be carried. On the otherhand complete coverage of the service area has to be provided from the beginning.Existing sites of the first implementation phase must be useable in later phases.Increasing subscriber numbers (synonymous with increasing interference tendency!)should be responded by completion of the existing TRX-equipment and by addition ofnew sites. This means reconfiguration of the existing cell patterns and frequencyreassignment. The planner should anticipate the future subscriber repartitions andconcentrations from the beginning, in creating cell structures capable to respond tofuture needs. Increasing interference problems arising with higher site density maybe overcome by downtilting of directional antennas initially mounted for maximumsignal range, as now the radio cell areas will be smaller.


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1.5 Site Selection

The site positions found in the coarse planning process on a theoretical basis, mustnow be verified in a joint campaign, called site survey, between the customer and theradio network planner. All site candidates within a tolerable search area around thetheoretical site positions must be checked.

This check includes the availability of electric power and of data transmission lines.

The most important topic is the possibility to install the antennas in a suitable heightabove the roofs or above ground.

Environmental influences (screening obstacles, reflectors) have also to be regarded.The best fitting site should be selected.

Another important task of this campaign is to declare a certain number of the radiosites be suitable to serve as „survey sites“. This means that radio field measurementsshall be done with these stations as transmitters. The resulting measurements will beused for the alignment of radio propagation models.

The environment of the survey sites should be typical for a considerable number ofother radio sites.

1.6 Field Measurements

Digital terrain data bases (DTDB) as derived from topographical maps or satellitepictures do not contain all details and particularities of the existing environment.Especially in fast developing urban areas maps cannot keep pace with reality andthus reflect an obsolete status. Keeping maps on this quality level would be veryexpensive.

The characteristics of built up zones and vegetation areas with respect to radiopropagation differ in a wide range if we regard different countries. Even climaticconditions may influence the signal level. Knowledge about this specific behaviormust be acquired by measurements.

The survey measurements have to be carried out in typical areas. Evaluation of thesemeasurements will result in models that can be applied in comparable areas as well.

Special measurements must be carried out in very complex topographical regionswhere standardized propagation models will fail. The resulting models are validexclusively for this measurement zone.


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1.7 Tool Tuning

The measurement results have to be compared with the predictions of provenstandard models. The standard parameters will be slightly modified to achieveminimum discrepancies with the measurements, i.e. to keep the mean error and rms-error as low as possible. As the signal level is subject to statistical variations whichcannot be predicted, the rms-error will never be zero.

The reliability of the created models increases with the number of measurement runsthat can be exploited.

The new specific model may also be applied in other base stations located in similarenvironment.

1.8 Network Design

The area-specific models are the basis for the final planning steps. The detailednetwork design has to care for

� a suitable signal level throughout the planning area

� sufficient traffic capacity according to the operators requirements

� assignment of the pertinent number of RF-carriers to all cells

sufficient decoupling of frequency reuse cells to respect the interferencerequirements for co-channels and adjacent channels.

Moreover, attention has to be paid to an optimized handover scenario in heavy trafficzones.

The detailed planning process commits the final structure of the radio network andthe configuration of the base stations.

The capacity of digital data links connecting the radio stations to the fixed networkelements may now be defined.


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1.9 Data Base Engineering

A cellular network is a living system with moving subscribers. The service must bemaintained while mobiles change radio cells and superior organization units, calledlocation areas. All control parameters, necessary to support this task, have to beadministered and supervised in central data bases.

There is a permanent signaling information exchange between mobiles, base stationsand control centers.

This signaling communication occurs on predefined time slots, called controlchannels which are assigned to one of the RF-carriers of each radio cell.

Important control informations for each radio cell are :

� cell identification within the network

� control carrier frequency

� potential neighbor cells

� minimum received signal level

� maximum transmit power of a mobile

� power reduction factor to perform power control

� power margin for handover to neighbor cells

1.10 Performance Evaluation and Optimization

Regular performance checks must be carried out after commissioning of the network.These checks comprise the evaluation of statistical data collected in the “operationsand maintenance center“ (OMC) as well as measurements by means of test mobilestations to explore e.g. handover events under realistic conditions; unwantedhandover may lead to traffic congestions in certain cells, or may drain off traffic fromother cells.

Detection of multipath propagation problems caused by big reflecting objects is alsosubject to measurements.

Another goal of these checks is to investigate the real traffic load and its distribution,as subscriber behavior in a living system will not necessarily reflect the originalassumptions of the operator; assumed hot traffic spots may have been changed orshifted after a couple of years.

Careful evaluation of the measurement data will help to optimize the networkperformance by modification of the system parameters. As the number of subscriberswill normally increase in course of time, supervision and control of these parametersshould become a permanent maintenance procedure.


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2 Repetition


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Mobile Radio Network Planning Tasks

� Collection of basic planning data

� Terrain data acquisition

� Coarse coverage prediction

� Network configuration

� Site selection and field measurements

� Tool tuning

� Network design

� Data base engineering

� Performance evaluation and optimization

Collection of basic planning data

� Customer must define basic network performance goals:

� Size of service area and area types

� Traffic load and distribution

� Mobile classes and service quality

� Future development (forecast)

� Available RF - bandwidth

� The resulting nominal cell plan is a first planning approach

� to determine the required number of radio stations

� to figure out the approximate equipment configuration

� to get an idea of the financial volume of the project


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Terrain data acquisition

Topographical and morphographical properties of the planning region must becompiled in a digital data base for further processing.

Contents of the digital terrain data base DTDB:

� Height profile (topography)

� Land coverage and usage (morphography)

Possible sources :

� Scanning of topographic maps

� Processed satellite pictures or air pictures

Coarse coverage prediction

A coarse coverage prediction based on the nominal cell plan and on the digital terraindata base:

� using standard propagation models

� using standard antenna types

Results :

� Geographical distribution of the radio signal level

� Coarse cell structure

� Nominal position of the radio sites and antenna orientation

� Search areas for final site positions

� Knowledge about the attainable degree of signal quality


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Network configuration

Internal configuration of individual radio station:

� Equipment to be installed

Configuration of the radio network (network structure):

� Number of base station controllers BSC

� Number of location areas

� Definition of data lines between the network elements

Site selection and field measurements

� Selection of definitive radio site locations

� Radio measurements in typical areas

� Radio measurements in complex topographical regions

Tool tuning

� Radio measurements are exploited to adapt standard propagation models tospecific environmental conditions

� Resulting models may be applied in similar environment

� or are restricted to the special measurement area


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Network design

The final radio planning is performed by means of the area - adapted models

Planning goals:

� Sufficient signal level throughout the planning region

� Sufficient traffic capacity according to subscriber distribution

� Assignment of radio carriers to all cells

� Low interference level for co-channels and adjacent channels

� Definition of neighbor cells

Data base engineering

Control and maintenance of the radio network requires parameters for

� Identification of serving cell and neighbor cells , i.e.:

cell identity

location area

color code

� Cell - allocated control- and traffic carriers

� Maximum transmit power level

� Minimum receive signal level

� Power margin for handover to each neighbor cell

Performance evaluation and optimization

� By analyzing statistical data from maintenance center

� Measurements performed by a test mobile station roaming about the operatingradio network


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3 Radio Wave Propagation


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There are three main components of radio propagation which are discussed in thenext section:

� mean path loss (loss due to the distance between MS-BS),

� shadowing (long term fading),

� multi path propagation � short term (Raleigh) fading.

3.1 Path Loss

Standard path loss models are of the form:

Lm[dB]= A + B log d [km]

where Lm is the mean propagation path loss between the base station (BS) and themobile station (MS) at a distance d.

A: unit loss at 1 km,

B: propagation index or loss per decade.

The propagation coefficients A and B depend upon:

� the transmit frequency,

� the MS and BS antenna heights,

� the topography and morphology of the propagation area.

Examples are:

1. Free space loss:

L0 = 32.4 + 20 log f [MHz] + 20 log d [km]

or more important propagation in real environment - the famous Hata model:

2. Hata model

The Hata model describes the mean propagation effects for large cells anddistances d > 1 Km. For urban environment one has:

A = 69.55 + 26.16 log f - 13.82 log Hb - a(Hm)

B = 44.9 - 6.55 log Hb


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Frequency: f [Mhz] 150...1000 -Mhz

BS antenna height: Hb [m] 30...200 m

MS antenna height: Hm [m] a(Hm) = 0 for Hm = 1.5 m

Example: Hm = 1.5 m Hb = 50 m f=900 Mhz

� A = 123.3 B = 33.8

Path Loss for LargeCells - Hata Model (GSM 900)

� BS height 50 m

� MS height 1.5 m

90

100

110

120

130

140

150

160

170

180

190

200

210

220

1 10 100

Cell radius [km]

Path

Lo

ss [

dB

] Urban

Urban Indoor

Suburban

Rural (quasi open)

Rural (open)

Fig. 2


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For other environments (suburban, rural-quasi-open) the path loss per decaderemains the same, but the unit loss is reduced by a certain amount. The free spaceloss and the Hata model are illustrated in the figure above.

Models of this type are adequate for estimating the received level for large cells.However for a real network planning, refinements of the model and adaptations ofparameters to morphological and topographical data and to measurement values arenecessary (refer to section 1).

The smaller the cells, the more important are the details of e.g. the building structurewithin the cell.

3.2 Shadowing - Long Term Fading

In larger cells where the BS antenna is installed above the roof top level, details ofthe environment near the MS are responsible for a variation of the received levelaround the mean level calculated by the models discussed above.

Usually this variation of level - caused by obstacles near the MS (e.g. buildings ortrees) - is described by the statistical model, i.e. the total path loss Ltot is given by themean „distance“ path loss plus a random shadowing

Ltot [dB] = Lm + S

S<0: free line of sight,

S>0: strong shadowing by e.g. a high building near the MS.

S has a Gaussian distribution (see figure below) with mean value 0 and a standarddeviation s which typically lies in the range s = 4...10 dB.


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-3 -2 32-1 10

0.1

0.2

0.3

0.5

0.4

Sh d i S/ [dB]Fig. 3 Gaussian distribution of shadowing S


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The length scale for variation of the long term fading is in the range 5 ... 100 m, i.e.the typical size of shadowing obstacles.

3.3 Multi Path Propagation - Short Term Fading

The superposition of several reflected waves arriving at the receiver on differentpaths and therefore with different amplitudes and phases causes peaks (constructivesuperposition) and deep fading dips (destructive superposition) of the received level.

The length scale for variation (e.g. peak to peak) is given by the half of thetransmission wave length, i.e. about 15 cm for GSM900 or 7.5 cm for DCS1800. Anexample for the variation of the received level due to short term fading is shown inthe figure below.

A comparison with the length scale for shadowing explains the names for thesefading types.

The statistics of the Raleigh fading is described in the following way:

Consider the received level due the path loss and long term fading which is calledlocal mean: LLOC[dBm]. The received local mean power is then given by

Ploc[mW] = 10LlOC/10

Using this formula the probability density function for the received power P is givenby:

f(P) = 1/Ploc* exp(-P/Ploc)

which means that the probability function for the signal amplitude P = A2 is given by aRaleigh distribution.

Using these formulas and some mathematics, one can calculate the probability thatthe received level L (affected by Raleigh fading) is x dB below the local mean levelLloc:

Prob (L - Lloc< x dB) = 1 - exp ( - 10 x/10)


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Example:

x = 3 dBx = 0 dBx = -3 dBx = -6 dBx = -10 dBx = -20 dB

Prob = 86,5 %Prob = 63,0 %Prob = 39,5 %Prob = 22,0 %Prob = 9,5 %Prob = 1,0 %

Changing the transmission frequency and therefore the wave length, changes theposition of Raleigh peaks and dips. This means that at a given position, the receivedlevel affected by Raleigh fading in general differs for different transmissionfrequencies. The higher the frequency difference the lower is the correlation for thereceive signal for the different frequencies. The coherence bandwidth Bcoh is definedas the frequency difference at which this correlation has decreased to 0.5. Thecoherence bandwidth depends upon the spread of arrival times of the different multi

path components of the received signal. This spread is called delay spread �T:

Coherence Bandwidth and Delay Spread

BT

coh�

1

2��

i.e. the higher the delay spread the lower is the coherence bandwidth.

The delay spread depends upon the propagation environment. Typical values are:

� 10 µs for hilly terrain (corresponding to path length between difference of 3 km).

� 0.1 ... 1 µs for urban area (corresponding to path length between difference of 30... 300 m).

Keeping in mind that a Raleigh fading dip of more than 10 dB occurs with aprobability of 10 %, measures should be provided to combat Raleigh fading:

Means to combat Raleigh fading:

� Averaging of Raleigh fading over speech frames (interleaving of 8 bursts)

Frequency Hoppingspacing between frequencies in hopping sequence >> coherence bandwidth

Motion (speed v)Example: v=50 km/h, distance between bursts = TDMA frame length T = 4.6 ms

� distance between MS positions at subsequent bursts D = 6.4 cm

� distance for 8 bursts_ 8 * D � 50 cm > 3 * wavelength

� Combining of signals received at positions of mutually uncorrelated fading

Antenna Diversityspacing between RX antennas >> half wavelength


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Fig. 4


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Short Term Fading

Fig. 5


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3.4 Maximum Path Loss and Link Budget

The maximum radius of a cell depends on the maximum possible path loss betweentransmitter and receiver, i.e. upon the difference between the maximum output powerlevel EIRP (emitted isotropic radiation power) at the transmitter antenna and therequired input power level (RIPL) at the receiver antenna.

Output BTS:

EIRPBTS = Power Amplifier Output - Combiner Loss - Downlink Cable Loss + AntennaGain

Power Amplifier Output: 25 Watt = 44 dBm (GSM900)

(higher power amplifier output power in further BTSversions)

Combiner Loss

Combiner Type 1:1 2:1 4:1

Duplexer 2.7 dB 2.7 dB 5.9 dB

Hybrid Combiner 2.0 dB 5.2 dB 8.4 dB

The ratio x:1 denotes the number of carriers which are combined. In the case ofhybrid combiners the signals are fed to 1 transmitter antenna. In the case ofduplexers the signals are fed to 2 antennas (on air combining) which are used fortransmission as well as for reception.

Using these antennas for reception, a two branch (maximum ratio) antenna diversitycombining can be realized. This means that - using Duplexers - two antennas per cellare needed, whereas when using Hybrid Combiners and applying Antenna Diversitytwo receive plus one transmit antenna is needed.

Downlink Antenna Cable Loss: 3 dB (example)

Antenna Gain (example): 16 dB (typical value for 600 half power beamwidth antenna)


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Output MS:

For the MS there is no need combining different carriers; and the cable loss andantenna gain reduce to zero. The EIRP depends upon the power class of the MSspecified in GSM Rec 05.05:

Power Class (GSM 05.05) Max. Output Power(GSM900)

Max. Output Power(DCS1800)

1 -- 1 Watt = 30 dBm

2 8 Watt = 39 dBm 0.25W = 24 dBm

3 5 Watt = 37 dBm 4 Watt = 36 dBm

4 2 Watt = 33 dBm

5 0.8 Watt = 29 dBm

Input BTS:

The required input power level RIPL at the BTS antenna is given by

RIPLBTS =Receiver Sensitivity Level - Antenna Diversity Gain + Uplink Cable Loss

- Antenna Gain

Receiver Sensitivity Level < - 104 dBm

The receiver sensitivity level is defined in GSM Rec. 05.05 for scenarios where shortterm Raleigh fading is (at least) partly averaged either by motion or by frequencyhopping. The receiver sensitivity level has been measured to be better than requiredby GSM Rec. 05.05.

Antenna Diversity Gain: 4 dB (for a typical scenario).

The gain which can be achieved by antenna diversity strongly depends upon thepropagation environment, the velocity of the mobile and on whether frequencyhopping is applied or not.

For a typical urban environment, a mobile speed of 3 km/h and frequency hoppingapplied the antenna diversity gain is about 4 dB.

Uplink Cable Loss 3 dB without tower mounted preamplifier RXAMOD

0 dB with tower mounted preamplifier RXAMOD

The (uplink) cable loss from the antenna to the receiver input can be compensatedusing a tower mounted amplifier called RXAMOD.It should be noted that this preamplifier cannot be used together with on aircombining (Duplexers).

Antenna Gain (example): 16 dB (typical value for 600 half power beam width

antenna)


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Input MS:

For the MS there is neither antenna gain nor antenna diversity gain. Cable losses canbe neglected. Therefore the required input power level at the MS antenna is given bythe MS receiver limit sensitivity as specified by GSM 05.05:

� 104 dBm for class 2 and 3 (GSM900),

� 102 dBm for class 4 and 5 (GSM900),

� 100 dBm for class 1 and 2 (DCS1800)

Maximum allowed path loss (Link Budget)

downlink Ld[dB] = EIRPBTS - RIPLMS

uplink Lu[dB] = EIRPMS - RIPLBTS

Example:

Duplexers 2:1: � no RXAMOD, uplink cable loss = 3 dB

MS of Power Class 3: � EIRPMS= 37 dBm

Antenna Diversity Gain: 4 dB

� Lu[dB] = 37 dBm - (- 104 dBm - 16 dBi + 3 dB - 4 dB) = 158 dB

� Ld[dB] = 44 dBm - 3 dB - 3 dB + 16 dBi - (- 104 dBm) = 158 dB

� i.e. there is a symmetric link budget for uplink and downlink.

� Requirement: Area Coverage Probability: 90 % ��Coverage Probability at CellBorder: 75 %

� Standard Deviation of Shadowing: s= 6 dB � 75 % value of Shadowing: S75%= 4dB

� allowed loss L - S75% = 154 dB

� Lm = L - S75% = 154 dB

Path loss model (Hata): Lm [dB] = 123.3 + 33.7 log d [km]

� Cell Radius: dmax =10 (154-123.3)/33.7 = 8.15 km

Example 2:

Designing a radio cell for mainly MS of Power Class 4 (instead of power class 3), thefollowing values for link budget are obtained:

Lu[dB] = 154 dBLd [dB] = 156 dB

To obtain a symmetric link budget, the power amplifier output power of the BTS hasto be reduced by 2 dB. This is done using the O&M parameter BS_TXPWR_RED:


MN1789EU07MN_000132

Object DB Name Range Meaning

TRX PWRRED 0, 1, ...6 * 2dB Reduction of BTS power amplifieroutput

Reducing the BTS output power has the advantage that less downlink interference iscaused by this cell.

If there are also some mobiles of Power Class 2 and 3 within the cell designed formobiles of Power Class 4, their maximum transmit power has to be limited for a linkbudget balance. This is the reason behind the following parameters:

SpecificationName

DB Name/Object

Range Meaning

MS_TXPWR_MAX

MSTXPMAX /BTS-B

2...15GSM0...15DCS

* 2 dB

Maximum TXPWR a MS isallowed to use on a dedicatedchannel (TCH or SDCCH) in theserving cellGSM: 2 = 39 dBm, 15 = 13 dBmDCS: 0 = 30 dBm, 15 = 0 dBmPCS: 0 = 30 dBm, 15 = 0 dBm

30 = 33 dBm, 31 =32 dBm

MS_TXPWR_MAX_CCH

MSTXPMAXCH /BTS-C

0...31* 2 dB

Maximum TXPWR a MS isallowed to use on the uplinkcommon control channel(Random Access Channel,RACH) in the serving cell:GSM: 0 = 43 dBm,19 = 5 dBmDCS: 0 = 30 dBm, 15 = 0 dBm

Another effect illustrated by this example is the following:

Since there is a balanced link budget Lu[dB] = Ld[dB], but a difference of the receiversensitivity level for the MS and BTS of 2 dB, there is difference between the meandownlink and uplink received level RXLEV of about 2 dB:

RXLEV_DL - RXLEV_UL � 2 dB.

The consequence is that level threshold for e.g. the handover algorithm have to beset 2 dB higher for the downlink than for the uplink.


MN1789EU07MN_000133

4 Cellular Networks and FrequencyAllocation


MN1789EU07MN_000134

One important characteristic of cellular networks is the re-use of frequencies indifferent cells. By re-using frequencies, a high capacity can be achieved. However,the re-use distance has to be high enough, so that the interference caused bysubscribers using the same frequency (or an adjacent frequency) in another cell issufficiently low.


MN1789EU07MN_000135

Cell Radius R

Re-use

Ditance D

MS

Carrier

Co-channel

Re-use

Cells

Interferer

Fig. 6


MN1789EU07MN_000136

To guarantee an appropriate speech quality, the carrier-to-interference-power-ratioCIR has to exceed a certain threshold CIRmin which is 9 dB for the GSM System(GSM Rec. 05.05).

taking the situation of the example above and a path loss model L = A + B log d, onehas

C/Itot[Watt] = C / (I1 + ... + INI) � C / (NI * I1) NI: number of interferes

or in dB

C/Itot [dB] = C[dB] - Itot[dB] � B log D - B log R - 10 log NI

= B log D/R - 10 log NI > CIRmin + LTFM (x%)

By introducing the long term fading margin LTFM (x%) for a required coverageprobability of x%, the effect of shadowing is taken into account.

For homogeneous hexagonal networks frequencies can be allocated to cells in asymmetric way. Defining the cluster size K as group of cells in which each frequencyis used exactly once, the following relations between Cluster Size, Cell Radius andRe-use Distance are obtained.


MN1789EU07MN_000137

Frequency Re-use and Cluster Size

m

n

Rr

D

D

Fig. 7

Outer Cell Radius � R

Inner Cell Radius � r = 0.5 x 3 x R

Re-use Distance� D = R x 3 x (n m nm)

2 2� �

Kx3=R

D

Cluster Size: Group of cells in which each frequency is used exactly once

K = (n + m + nm)2 2

n,m = 0, 1, 2, 3, ...

K = 1, 3, 4, 7, 9, 12 16 19, , , ...


MN1789EU07MN_000138

Inserting the formula for the cluster size into the formula for the minimum CIR oneobtains:

0.5 * B log 3 K > CIRmin + LTFM (x%) + 10 log NI

which gives a lower bound for the cluster size which can be used.

For a given cluster size K and total number of frequencies Ntot, the number offrequencies per cell Ncell is given by:

Ncell = Ntot/K

i.e. the capacity of a cell can be increased by reducing the cluster size.

A reduction of cluster size can be achieved by

� reducing the number of interferes � Sectorisation.

� reducing the interference from co-channel cells � Power Control, DiscontinuedTransmission, ...

Examples for sectored network structure are shown in the figures below. Methods forinterference reduction are discussed in chapter 6.

Obviously a real network does not have such a regular hexagonal structure andfrequency allocation is performed by planning tools using complex algorithms foroptimizing the CIR in each cell.

The objective is to achieve a high mean value of frequencies per cell <Ncell>. Theratio

<K> = Ntot/Ncell

can viewed as the mean cluster size in such an inhomogeneous environment.

The capacity of the radio network depends upon the available number N of radiochannels per area F (e.g. F = 1 km2).

N

FN x

N

FCPF x

N

K x

1

F / NCPF x

N

K x

1

CAcell

BTS tot

BTS

tot� � �

NBTS: number of BTS

CA: cell area

CPF: channel per frequencies


MN1789EU07MN_000139

Omnicells - Cluster 7

5

3

4

7

6

2

1

5

3

4

7

6

2

1

5

3

4

7

6

2

1

5

3

4

7

6

2

1

5

3

4

7

6

2

1

5

3

4

7

6

2

1

5

3

4

7

6

2

1

Fig. 8 Example for homogeneous frequency allocation


MN1789EU07MN_000140

3-Sector Cloverleaf - Cluster 3 x 3

1a

1b1c

2a

2b2c

3a

3b3c

1a

1b1c

2a

2b2c

3a

3b3c

1a

1b1c

2a

2b2c

3a

3b3c

1a

1b1c

2a

2b2c

3a

3b3c

1a

1b1c

2a

2b2c

3a

3b3c

1a

1b1c

2a

2b2c

3a

3b3c

1a

1b1c

2a

2b2c

3a

3b3c

Fig. 9 Example for homogeneous frequency allocation


MN1789EU07MN_000141

5 Traffic Models


MN1789EU07MN_000142

A traffic model reflects the behavior of the subscribers, as their mobility, the meancall rate or call duration. It is needed e.g. for calculating the required total number ofchannels within a cell and how to split them between traffic and control channels.

These traffic model information is always a mixture between field observations insimilar networks and arbitrary assumptions.

Traffic data are variable in time, therefore statistical characterization is used.

The goal of planning is to manage traffic even in busy hour.

In mobile networks we have to evaluate two main factors:

� user mobility

� communications

User mobility:

The user moves with a velocity v.

For example the handover and location update rates depend on this velocity.

Communications:

The number of subscriber in a cell, the traffic per subscriber has to be considered.

Furthermore, one needs information the mean call duration, the mean call cell rate(or busy hour call attempt BHCA). separately for mobile originating calls (MOC) andmobile terminating calls (MTC).


MN1789EU07MN_000143

An example for a traffic model is given in the table below:

number of call attempts (MOC+MTC) per subscriber per hour 1,1

percentage of MOC 58 %

percentage of ‘engaged’ in the case of an MOC 19,8 %

duration of TCH occupation in the engaged case 3s

no answer from a person called by MOC 14,4 %

mean TCH occupation for this case 30 s

percentage of successful MOC 65,8 %

mean time for ringing (MOC) 15 s

percentage of MTC 42 %

no paging response 32,5 %

duration of TCH occupation in this case 0 s

no answer from a mobile subscriber 13,5%

means TCH occupation fir this case 30 s

successful MTC 54,0 %

mean time for ringing (MTC) 5 s

mean call duration (MOC/MTC) 115 s

mean TCH occupation call attempt 83 s

TCH load per subscriber 0,025 Erl

time for MOC/MTC setup signaling on SDCCH (authentications, ...) 3 s

time for a location update 5 s

number of location update per subscriber per hour 2,2

resulting SDDCCH load per subscriber (no TCH queuing applied) 0,004 Erl

Standard traffic model for GSM

The formula for calculating the load on the respective dedicated channel are given onthe next page.


MN1789EU07MN_000144

Load on Dedicated Channels

SDCCH load[Erl]:

SUBSCR * ((MTC_PR_ph + MOC_ph) * T_SETUP + LU_ph *T_LU+ IMSI_ph * T_IMSI + SMS_ph * T_SMS)

TCH load [Erl]: SUBSCR * (MTC_PR_ph + MOC_ph) * T_CALL

SUBSCR: number of subscribers within the cell

MTC_PR_ph: mobile terminating calls per subscriber per hour with pagingresponse

MOC_ph: mobile terminating calls per subscriber per hour

LU_ph: location updates per subscriber per hour

IMSI_ph: IMSI attach/detach per subscriber per hour

SMS_ph short message service per hour

T_SETUP: mean time [sec] for call setup signaling on SDCCH

T_LU: mean time [sec] for location update signaling

T_IMSI: mean time [sec] for IMSI attach/detach signaling on SDCCH

T_SMS: mean time [sec] for short message service

T_Call: mean TCH occupation time per call

For the values of the traffic model above one has

TCH load per subscriber: 25 mErl

SDCCH load per subscriber: 4 mErl


MN1789EU07MN_000145

n p = 1 % p = 3 % p = 5 % p = 7 % n p = 1 % p = 3 % p = 5 % p = 7 %

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

0.01

0.15

0.46

0.87

1.36

1.91

2.50

3.13

3.78

4.46

5.16

5.88

6.61

7.35

8.11

8.88

9.65

10.44

11.23

12.03

12.84

13.65

14.47

15.29

16.13

16.96

17.80

18.64

19.49

20.34

21.19

22.05

22.91

23.77

24.64

25.51

26.38

27.25

28.13

29.01

29.89

30.77

31.66

32.54

33.43

34.32

35.22

36.11

37.00

37.90

0.03

0.28

0.72

1.26

1.88

2.54

3.25

3.99

4.75

5.53

6.33

7.14

7.97

8.80

9.65

10.51

11.37

12.24

13.11

14.00

14.89

15.78

16.68

17.58

18.48

19.39

20.31

21.22

22.14

23.06

23.99

24.91

25.84

26.78

27.71

28.65

29.59

30.53

31.47

32.41

33.36

34.30

35.25

36.20

37.17

38.11

39.06

40.02

40.98

41.93

0.05

0.38

0.90

1.53

2.22

2.96

3.74

4.54

5.37

6.22

7.08

7.95

8.84

9.37

10.63

11.54

12.46

13.39

14.31

15.25

16.19

17.13

18.08

19.03

19.99

20.94

21.90

22.87

23.83

24.80

25.77

26.75

27.72

28.70

29.68

30.66

31.64

32.62

33.61

34.60

35.58

36.57

37.57

38.56

39.55

40.54

41.54

42.54

43.53

44.53

0.08

0.47

1.06

1.75

2.50

3.30

4.14

5.00

5.88

6.78

7.69

8.61

9.54

10.48

11.43

12.39

13.35

14.32

15.29

16.27

17.25

18.24

19.23

20.22

21.21

22.21

23.21

24.22

25.22

26.23

27.24

28.25

29.26

30.28

31.29

32.31

33.33

34.35

35.37

36.40

37.42

38.45

39.47

40.50

41.53

42.56

43.59

44.62

45.65

46.69

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

38.80

39.70

40.60

41.50

42.41

43.31

44.22

45.13

46.04

46.95

47.86

48.77

49.69

50.60

51.52

52.44

53.35

54.27

55.19

56.11

57.03

57.96

58.88

59.80

60.73

61.65

62.58

63.51

64.43

65.36

66.29

67.22

68.15

69.08

70.02

70.95

71.88

72.81

73.75

74.68

75.62

76.56

77.49

78.43

79.37

80.31

81.24

82.18

83.12

84.06

42.89

43.85

44.81

45.78

46.74

47.70

48.67

49.63

50.60

51.57

52.54

53.51

54.48

55.45

56.42

57.39

58.37

59.34

60.32

61.29

62.27

63.24

64.22

65.20

66.18

67.16

68.14

69.12

70.10

71.08

72.06

73.04

74.02

75.01

75.99

76.97

77.96

78.94

79.93

80.91

81.90

82.89

83.87

84.86

85.85

86.84

87.83

88.82

89.80

90.79

45.53

46.53

47.53

48.54

46.54

50.54

51.55

52.55

53.56

54.57

55.57

56.58

57.59

58.60

59.61

60.62

61.63

62.64

63.65

64.67

65.68

66.69

67.71

68.72

69.74

70.75

71.77

72.79

73.80

74.82

75.84

76.86

77.87

78.89

79.91

80.93

81.95

82.97

83.99

85.01

86.04

87.06

88.08

89.10

90.12

91.15

92.17

93.19

94.22

95.24

47.72

48.76

49.79

50.83

51.86

52.90

53.94

54.98

56.02

57.06

58.10

59.14

60.18

61.22

62.27

63.31

64.35

65.40

66.44

67.49

68.53

69.58

70.62

71.67

72.72

73.77

74.81

75.86

76.91

77.96

79.01

80.06

81.11

82.16

83.21

84.26

85.31

86.36

87.41

88.46

89.52

90.57

91.62

92.67

93.73

94.78

95.83

9689

97.94

98.99

Erlang B formula


MN1789EU07MN_000146


MN1789EU07MN_000147

6 Exercises


MN1789EU07MN_000148


MN1789EU07MN_000149

Exercise

Title: Calculation Loss / Gain

Task

LP�

��

�� 10 log

P

10 dBm

-3reference P = 1 mW

LU�

��

�� 20 log

U

10 dB V

-6� reference U = 1 µV

Loss B A 10 log P

P din

out

��

��

�

��

Gain G B 10 log P

P dout

in

��

��

�

��

P � U

R

2

L BUU�

��

�� 20 log

U

0,775 d reference = 775 mV, 600 �

A 20 log U

U

in

out

��

��

�

��

G ��

��

�

�� 20 log

U

U

out

in

1. Amplifier: 100 mVin, 1 Vout. Calculate the gain

2. Amplifier: 2 mWin, 5 Wout. Calculate the gain

3. Amplifier: 20 dBmin, two steps amplification with 7 dB, 3 dB gain. Calculate thegain.


MN1789EU07MN_000150

Appendix Exercise 1

Power classes for MS/BTS

Class Watt dBm

12345

20852

0,8

4339373329

�

��

�� MS

12345678

320160804020105

2,5

5552494643403734

�

�

��

�

��

BTS

Conversion dBm � Watt

Watt dBm

4 � 10 -14

10 -5

10 -4

10 -3

10 -2

10 -1

122550100

-104-20-10010203033444750

Maximum Range

Example: SBS, GSM

Power Amplifier 25WattCombiner

2:1CableAntenna gain

Sending power

^ 44 dBm - 8 dB - 3 dB+18 dB

51 dBm ^ 125 Watt


MN1789EU07MN_000151

Handy sensitivity -102 dBm

� possible loss 153 dBm

153dBm

^ 8 km free area3 km urban area1 km downtown

Typical loss values:

Fading:Glass:Wall:Shopping Mall:House

6 dB5 dB

12 dB25 dB

15 dB


MN1789EU07MN_000152


MN1789EU07MN_000153

7 Solutions


MN1789EU07MN_000154


MN1789EU07MN_000155

Solution

Title: Calculation Loss / Gain

Task

1. G = 10 log 1

0,1 = 20 dB

��

��

2. G = 10 log 5

0,002 = 34 dB

��

��

3. Power out = 20 + 7 + 3 = 30 dBm

30 dBm ^ 1 Watt


MN1789EU07MN_000156

appendix-c: fundamentals of radio network planning

Documents