2G Network Dimension Ing

Number/Version Checked by Approved by Page

NTCD ASXX 0455/1.0 en

Owner unit: NTC/CS/PS

03.98 Matti Manninen 03.98 Ari Niininen 1(53)

Company Confidential

DIMENSIONING OF MOBILE AND WLL NETWORKS

Work Instruction

NOKIAThis document is for INTERNAL USE ONLY. Please request written

permission from the responsible person before distribution outside Nokia.

DIMENSIONING OF CELLULAR AND WLL NETWORKS

CONTENTS

1. GENERAL

2. THE PRINCIPLES OF NETWORK DIMENSIONING2.1. Overview2.2. Structure of dimensioning plan2.3. Flow of dimensioning

3. REGION CALCULATION3.1. Coverage calculation

3.1.1. Radio link power budget3.1.2. Location probability for outdoor, incar and indoor3.1.3. Site area3.1.4. Site length

3.2. Capacity calculation3.2.1. RF units, traffic channels and traffic3.2.2. Traffic per subscriber3.2.3. Frequency reuse number3.2.5. Intelligent Underlay Overlay3.2.6. Micro cell Calculations3.2.7. Dual Band3.2.7. Frequency Hopping

3.3. Number of sites3.3.1. Triggers between systems and layers3.3.2. Example: Capacity enhancement triggers

3.4. BTS access transmission3.4.1. General3.4.2. Common information3.4.3. Common information for base station3.4.4. Number of links for different topologies3.4.5. Total number of link3.4.6. Cross Connection equipment3.4.7. ET cards3.4.8. Submultiplexing

3.5. Controller calculation

4. PLAN CALCULATION4.1. Switch calculation4.2. Transmission in a plan

4.2.1. General4.2.4. Transmission for controller - switch interface

4.3. Consolidation of region calculation4.3.1. Region inputs in a plan4.3.3. Configurations base stations and controllers in Excel

Number/Version Date Page

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4.3.4. Transmission configurations

5. CONFIGURATION OF NETWORK ELEMENTS5.1. Base station5.2. Mobile5.3. Controller5.4. Switch5.5. Transmission

7. WIRELESS LOCAL LOOP AND DIMENSIONING7.1. Six approaches to build a WLL network

7.1.1. Easywave Access with mobile phones7.1.2. Easywave Access with PremiCell terminals7.1.3. Easywave System7.1.4. Combined Mobile and WLL network in the same

coverage area7.1.5. Combined Mobile and WLL network with partially

overlapping coverage areas7.1.6. Combined Mobile and WLL network using different

frequencies

8. RELATED DOCUMENTS

DOCUMENT REVISION HISTORY

APPENDICESAppendix 1. BTS RX RF-Input Sensitivity with Mast Head

AmplifierAppendix 2. SensitivityAppendix 3. Isolators, combiners and filtersAppendix 4. Antennae for WLL terminalAppendix 5. Output powers


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1 GENERAL

The purpose of this document is to describe the tool and methods used in network dimensioning within Nokia. Also, the document gives default parameters for base stations, mobiles, terminals, controllers, etc.

Radio link power budget is described in document Power Budget Calculations, Work Instruction. If reader has a need to study power budget more detailed he or she can refer the work instruction.

Network dimensioning tool (NetDim) is described partly in this document. In this document calculation principles are explained. However, there is a user manual for the tool, as well. The manual describes how to install the tool and how to use it.

2. THE PRINCIPLES OF NETWORK DIMENSIONING

2.1. Overview

Network Dimensioning Tool (NetDim) is used to calculate the number of network elements. Calculation is based on radio link power budget, given coverage and capacity requirements. Quality targets are considered partly on power budget and partly in NetDim.

Firstly, the number of sites is calculated based on power budget and capacity requirements. Secondly, the number of controllers is calculated if the selected system(s) is using controllers. Together with controllers transmission is calculated. Finally, the number of switches is calculated.

2.2. Structure of dimensioning plan

The structure of dimensioning plan is shown in the picture below.


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Dimensioning Plan

Area 1 Area nArea 2

System 1 System mSystem 2

Macro layer Micro layer

AreaSubscriberTraffic / SubscriberLocation ProbabilityBlocking Probabilityetc.

AreaSubscriberTraffic / SubscriberLocation ProbabilityBlocking Probabilityetc.

Figure 1. The structure of dimensioning plan. The plan consists of one or several areas (regions). Each area may have several systems and each system has macro and/or micro layer.

Dimensioning plan consists of one or several areas (regions). Geographical area is divided into the regions based on radio wave propagation and traffic distribution. Traffic distribution should be flat in each region and propagation environment should not vary too much. If these two assumptions are not valid in a region, the region should be divided into smaller regions to fulfil the assumptions.

2.3. Flow of dimensioning

As described earlier in dimensioning both coverage and capacity requirements together with quality targets must be fulfilled. However, coverage and capacity calculations can not be separated totally, because capacity needs may have an impact on coverage and vice versa. The following chart shows the flow of dimensioning as implemented in NetDim.


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Figure 2. The flow of dimensioning as implemented in NetDim. The chart presents the flow in plan level. Later in the document the flow charts for BTS, controller, switch and transmission calculation are presented.

In NetDim regions are independent objects that are calculated separately. Firstly, coverage, capacity and quality requirements are given for each area. Secondly, the number of base stations and their configurations are calculated. Thirdly, if there are controllers available (BSCs in GSM) the number of controllers together with configurations are determined. Finally, for each area transmission for BTS access network is calculated if transmission calculation is selected. If there are no controllers available or no transmission is selected, transmission is not calculated.

After all areas are calculated the plan is calculated. If there are switches available in the plan they are calculated as well as controller access transmission. Finally, the results from the plan and areas are consolidated to a summary sheet.

The calculation procedure described above is repeated for all the phases in a plan. It is possible to link phases together (for example, number of sites is not decreasing in time) but the basic calculation is independent on the previous or following phases.


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In the following chapters the parts on the previous flow chart are explained more detailed. First, calculation related to areas is explained. This part is divided into smaller parts because a region is the most important calculation object in NetDim. Special attention is paid on base station calculation. Other parts are controller calculation and transmission calculation. Second, plan calculation is described. This includes switch calculation and consolidation of the area calculation. Third, configuration of network elements are explained and finally and default values for different network elements are given.

3. REGION CALCULATION

Calculation in NetDim is divided to a plan and areas. Each area in a plan may have several systems in used and each system can include both macro and micro layer. The main part of area calculation is related to base stations and theirs configurations. Other parts are controller calculation and base station access transmission calculation. Calculation flow is presented on the following figure.

Figure 3. The flow of area dimensioning as implemented in NetDim. Firstly, the number of sites is calculated based on coverage and quality targets. Secondly, traffic requirements are fulfilled and, if necessary, more sites are added. Finally, controllers and area transmission are calculated.


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3.1. Coverage calculation

In this chapter the calculation of coverage in NetDim is described. In NetDim there are three kinds of base stations. Repeaters will provide only coverage but no capacity, regular base stations are providing both capacity and coverage and there are base stations providing only capacity.

Base stations can be used to cover area (square km or miles) or length (km or miles).

3.1.1. Radio link power budget

Radio link power budget is calculated for each base station in each area and layer. Calculation method is described in the document ‘Power Budget Calculations, Work Instruction’.

The only difference in calculation in NetDim relates to combiner loss. In Power Budget Calculations document combiner loss is fixed but in NetDim combiner loss is changed according to RF unit count per sector (see 5.1).

3.1.2. Location probability for outdoor, incar and indoor

In NetDim location probability can be given for outdoor, indoor or incar. If only outdoor location probability is used in NetDim only standard deviation of field strength is used to calculate slow fading margin.

If indoor (or incar) coverage is planned, higher field strength on street level is required. To calculate slow fading margin for indoor coverage building penetration loss and its standard deviation are needed. Basically, for indoor coverage, coverage threshold is increased to compensate the loss due to buildings. Then standard deviation of building penetration loss is used to calculate the slow fading margin. However, in NetDim this margin and building penetration loss are added and the sum is called slow fading margin.

The location probability definition used in NetDim is for single, isolated cell. If location probability is calculated over the network the result will be higher. The situation in theory is presented on the following graph.


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0,65

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Single cell area location probability

Mu

ltip

le s

erv

er

loc

ati

on

pro

ba

bil

ity

Figure 4. Multiple server location probability versus single cell location probability. If fading of signals from neighbouring servers are non-correlating the curve shows the relation between single cell location probability and probability over network. In practise location probability over network is not as good as the graph shows.

When entering location probability figures in NetDim user should consider single cell location probability as a way to provide good location probability in a network but not as location probability over a network. Also, user should not that NetDim uses the tightest location probability criterion in calculations. If, for example, the target is 90% outdoor location probability for indoor and incar fairly low location probability values should be given. The low figure could be, for example, 30%.

3.1.3. Site area

NetDim calculates maximum cell ranges for all base station types following area type distribution. Because the formulas to calculate cell area are different for omni, two-sectored or three-sectored base stations NetDim uses base station distribution and corresponding formulas to calculate a weighted average cell area for the region. The formula to calculate cell area is shown in equation below.

Equation 1


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In the formula A is cell area, R is cell range and K is constant for each site type. Based on hexagons for omni site K is 2.6, for two-sectored K is 1.3, three-sectored base stations K is 1.95, etc. K factor may vary because it depends on 3dB beam with of the used antenna. Figure 5 shows the way in which Nokia defines K for three-sector-site (left) and, also, how K factor and site area is sometimes defined (right).

Figure 5. The definition of area of the cell as a function of cell range. On the left there is the way Nokia has used (65 antenna) and on the right the way that has been used commonly (120 antenna).

So far 1.95 as K has been used as a default value for three-sector-base station in NetDim. Considering the studies made with NPS/X, K factor depends on 3dB beam width, side lobes, and front - back ratio of the antenna.

Based on the studies made the following values can be used for different antennae.

Table 1. Recommendations for K factors for antennae with different 3 dB beam width for three-sector-base station.

Antenna type K factor

Omni 2.660 1.9590 2.15120 2.3


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K factors given in the table above are only recommendations. The different K factors are results of the coverage area of a site. If 120 antennae are used coverage area of a site is quite round but with 60 antennae between coverage area looks like a clover. If a site has more than three sectors K factor must be selected according to the shape of coverage area. If it can be assumed that coverage area of a site is circle K factor can be 2.6. Otherwise K factor should be little less.

3.1.4. Site length

Site length is calculated by using cell range and K factor. On the following graph the calculation of site length is described. In the example K would be 3 x R.

Figure 6. The definition of length of the cell as a function of cell range.

3.2. Capacity calculation

Capacity calculation in NetDim is based on the following assumptions. Firstly, traffic is evenly distributed over the target area. If this is not valid the area should be divided into smaller areas where the assumption is valid. Secondly, in the target area all subscribers share the same quality targets (location probabilities, blocking probabilities, etc.). Thirdly, each base station is using its own parameters (max. number of RF units, propagation, capacity features).


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3.2.1. RF units, traffic channels and traffic

In NetDim it is assumed that blocking probability in the air interface can be estimated from Poison distribution. The number of traffic channels, which are needed for given capacity can be calculated by using Erlang B tables. NetDim has functions to calculate either the number of traffic channels needed with given traffic and blocking probability but also the number of RF units (TRXs) needed. In GSM each RF unit has eight time slots for signalling and traffic. The default distribution of time slots for GSM based systems are given in the table below.

Table 2. Traffic and signalling time slots in GSM based air interface. For other systems user can define a multiplier to calculate traffic time slots from the number of RF units. On the table traffic is given with 1%, 2% and 5% blocking probability. In calculation Erlang B formula has been used.

TRXs Time Slots

Traffic TSs*

Signalling TSs

Traffic (1%)

Traffic (2%)

Traffic (5%)

1 8 7 1 2.5 2.9 3.7

2 16 15 1 8.1 9.0 10.6

3 24 22 2 13.7 14.9 17.1

4 32 30 2 20.3 21.9 24.8

5 40 38 2 27.3 29.2 32.6

6 48 45 3 33.4 35.6 39.5

7 56 53 3 40.6 43.1 47.5

8 64 61 3 47.9 50.6 55.6

9 72 69 3 55.2 58.2 63.7

10 80 76 4 61.7 64.9 70.8*TS = time slot

For other than GSM based systems user can define a multiplier that defines how many traffic time slots each RF unit has. For example, in analogue networks the multiplier is 1 (e.g. one RF unit has one traffic channel) and for TETRA the multiplier is 4.

Blocking in the air interface has been normally between 2% and 5%, but lately 1% blocking has been more common.

3.2.2. Traffic per subscriber

The load of the network varies during the day. Also the load varies between weeks and months. To handle this variance in traffic networks are dimensioned for the busy hour usage. This means that in cellular network traffic per subscriber is usually higher than the average traffic load during the day. Currently, traffic per subscriber usually varies in between 10 mErl and 30 mErl in cellular network. In WLL applications traffic can be 100 mErl per subscriber or more.


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3.2.3. Frequency reuse number

The frequency reuse number defines the pattern how frequencies are reused in the network. Frequency reuse number itself does not affect the capacity directly but it defines how many carriers each cell can have. For example, if GSM 900 operator has 5 MHz band available and reuse is 12, operator can have 2.08 carrier per cell in average (5 MHz / (0.2 MHz x 12).

Reuse number and bandwidth are defined for each layer (macro, micro), each system and each area. Reuse is given as a plain number but bandwidth can be given in MHz, number of radio channels or as percentage of total bandwidth.

3.2.5. Intelligent Underlay Overlay

The dimensioning of IUO needs some new inputs. The following list gives the most common inputs needed in IUO calculation.

The total number of channels available for regular layer The total number of channels available for super reuse layer Frequency reuse numbers for regular layers Frequency reuse numbers for super reuse layers Number of interferes C/I threshold

In this chapter the calculation of IUO layer is presented. First, the possible configurations are calculated based on frequency reuse numbers. Second, the capacity of each configuration is calculated based on assumptions of evenly distributed traffic, propagation, interference sources, and C/I threshold.

The average number of TRXs is used when the possible configurations in IUO cell are created. When calculating the number for regular or super reuse layer the same formula can be used.

Equation 2

whereaveTRXlayer average TRXs/sector in a layer

chstotal total channels in a layer

reuselayer frequency reuse in a layer


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For both regular and super reuse layers the average TRXs/sector is calculated. However, the minimum value for macro layer is 1 TRX/sector.

The optimal configuration based on the bandwidths and frequency reuse numbers would be aveTRXregular TRXs in regular layer and aveTRXsuper

TRXs in super layer. Because it is not possible to have fractional TRXs in layers there are maximum four combinations that are possible. The combinations are presented below.

TRXs in regular layer + TRXs in super layer floor(aveTRXregular) + floor(aveTRXsuper)floor(aveTRXregular) + ceiling(aveTRXsuper)ceiling(aveTRXregular) + floor(aveTRXsuper)ceiling(aveTRXregular) + ceiling(aveTRXsuper)

Function ‘floor’ rounds down the parameters to the nearest integer and ‘ceiling’ rounds up the parameter to the nearest integer. For example, floor(2.3) equals to 2 and ceiling(2.3) equals to 3.

Capacity of IUO cells depends on the total number of TRXs in a cell, how TRXs are shared between regular and super reuse layers, traffic distribution, C/I threshold, propagation of radio waves, interference sources and cell sizes. Before capacity can be calculated some of these inputs must be given and some interim results must be calculated.

The figure 7 presents how the layers provide service in different parts of IUO cell. The bad C/I area is the same as the outer ring of normal cell and it is calculated based on normal cell size calculations. The area of good C/I depends on traffic distribution, interference, how TRXs are shared between layers and selected thresholds.


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Figure 7. IUO cell. In super reuse area both layers can provide service but outside of that area only regular layer provides service.

In rough network planning the cellular networks are usually presented with hexagons. Based on hexagon grid and frequency reuse numbers C/I can be calculated. Lee 1 gives the formula presented below to calculate the needed frequency reuse number for omni base station. The formula takes into account only the first tier of inteferers (six nearest base stations sharing the same RF channel).

Equation 3

whereK frequency reuse

C/I minimum C/I ratio allowed

decay index, slope

Because frequency reuse number is already given, the minimum C/I ratio can be calculated. However, the equation 3 gives frequency reuse number for omni base stations in ideal environment. The equation can be modified in such way that it could be used for any kind of base station. The modified version of the equation is given below.

Equation 4.

where


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K frequency reuse

C/I minimum C/I ratio allowed

decay index, slope

n number of interferes

Equation 4 gives C/I value on the edge of the serving cell. The interference situation is presented in the figure below.

D

R

Interference

Carrier

I D R

C R

Figure 8. Cell range (R), Reuse distance (D) and interference on the cell edge.

The super reuse area is calculated based on interference thresholds and decay index. Equation 4 gives C/I on the edge of the cell. If the given C/I threshold for super reuse cell is lower than the calculated value on the cell edge, super reuse are defined by reuse factor. Otherwise it is defined by C/I threshold.

The absolute area of super reuse layer is not needed but the area relative to the regular area. The average distance between the cells sharing the same frequency (reuse distance, D) can be calculated from the cell range and frequency reuse number. Equation 5 gives reuse distance 1.


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Equation 5

whereK frequency reuse

D reuse distance

R cell range; regular layer

The range of super reuse area can be calculated from decay index and interference threshold with the equation 8. The assumption for the equation 8 has been that both the carrier (C) and interfering (I) powers are attenuating according the formula presented in equation 6.

Equation 6

whereP Power

D Distance from a site

Decay index; slope

In equation 8 inteferers are assumed to have equal field strength at the serving base station. The situation is presented on the following figure.


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Interference I D r

RCarrier

C r

r

Figure 9. C/I calculation for super reuse cell. Calculation point is not any more on the edge of regular cell. Thus the distance from servicing cell is r and from interfering cells D - r.

C/I is determined in the situation presented in Figure 9 according to the following formula.

Equation 7

whereC/I C/I on the edge of super reuse cell

decay index, slope

D reuse distance

r super reuse cell range

n number of inteferers


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The range of super reuse cell r can be solved if C/I is given as a threshold C/Ith.

Equation 8

whereC/Ith C/I threshold

decay index, slope

D reuse distance

R super reuse cell range

N number of inteferers

In Equation 8 C/I is as an absolute ratio - not a dB value. If C/I threshold is given in dB conversion can be made with the formula show below.

Equation 9

whereC/I C/I threshold; absolute value

C/IdB C/I threshold; dB value

If equation 5 and equation 8 are combined the super reuse cell range can be presented as a function of regular cell range, C/I threshold, frequency reuse and the number of interferes.

Equation 10

Good C/I probability is defined as a ratio between the areas of super reuse cell and regular cell. The ratio is presented in equation 11. Probability is calculated from the squares of super reuse cell range and regular cell range.


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Equation 11

Good C/I probability is needed when the traffic of IUO cell is calculated. Of course, good C/I should be between 0 and 1. If using equation 11 it is possible that Good C/I is large than 1. To avoid this the maximum value of equation 11 is limited to 1.

The next step in calculating the capacity of IUO cell is define mobile distribution between regular and super layer by assuming that the location of a mobile follows binomial distribution. This means that there is a probability p that each mobile is on good C/I area (in Figure 9. inner part of the cell) and probability q = 1-p that a mobile is on bad C/I area (outer part of the cell).

If there are n traffic time slots available in regular layer and m traffic time slots in super layer, traffic of the cell can be calculated with the following formula. The time slots in regular layer are always available. This means that there will be at least n traffic channels available in a cell. If all the mobiles are in bad C/I area there are only n traffic time slots available. Probability for this state is calculated when i = 0 in equation 12. If there is one mobile in good C/I area - and all the others are in bad C/I area - the result is calculated with i = 1. If m mobiles (total m + n) or more are in good C/I area traffic of the cell is maximum. In this case there are m + n traffic channels available. In equation 12 all possible mobile combinations are calculated and traffic of the cell is weighted average of the traffic of each combination.

Traf pm n

npErlbTraf pb n m n i

pm n

i

Area

Area

Area

Area

IUO i n mi

i n mbadC I

total

i

badC I

total

n m i

,

,/ /

, min ,0

1

Good C/ I Bad C/ I

Equation 12

where


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TrafIUO traffic of IUO cell

N time slots in regular layer

M time slots in super reuse layer

I ith combination

Pb blocking probability

AreabadC/I bad C/I area

Areatotal area of the cell

npErlbTraf A formula to calculate traffic according to Erlang B

On table 3 there is an example where it is assumed that in regular layer there can be maximum 7 (n) time slots and in super reuse layer maximum of 8 (m) time slots in used. Traffic of each combination together with probability is calculated. The total traffic of the cell is calculated as a sum of weighted traffic figure for each combination.


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Table 3. An example of IUO capacity calculations. Cell configuration is 1+1 and good C/I probability is 50%.

Note that the total traffic of the cell is less than the traffic of normal 2-TRX-cell (8.1 Erl).

As described earlier there are four different configuration needed to fulfil frequency reuse constrains for regular and super layers. All four combinations can be used when implementing IUO.

There are three constrains for configuration distribution:

sum of all configurations is 100% the average number of TRXs/sector of regular layer must match with

frequency band and reuse number the average number of TRXs/sector of super layer must match with

frequency band and reuse number

If percentage of one of the possible configurations is fixed (afix) the others percentages can be calculated using matrix algebra. The 4 x 4 matrix A presents the constrains, X presents the distribution vector and k presents the values of constrains. However, for all xi xi0.


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Equation 13

wheresi number of super reuse TRXs in ith combinations

ri number of regular TRXs in ith combinations

xi percentage of ith combination

avesru average number of super reuse TRXs

avereg Average number of regular TRXs

afix fix percentage for the first combination

The first row in matrix A defines the constrain where the sum of distributions must be 100% (i.e. 1). The second row presents average TRX number for super reuse layer. This is defined by the bandwidth and frequency reuse number of super reuse layer. The third row presents average TRX number of regular layer. Finally, the last row fixes one combination.

NetDim creates distribution for different configurations based on calculation above. Because the possible combinations in IUO cell depend on how the frequency band is divided between regular and super reuse layer, the selected division may not give to best capacity. That is the reason why the user should test different sets of super reuse channels, regular channels and overlapping between frequency pools.

The base station configurations are presented either based on hardware or IUO configurations. If hardware configurations are presented only the total amount of TRXs per sector are given. For example, configuration with 5 TRXs per sector would be 5 + 5 + 5 (site configuration). However, if IUO configurations are presented the result could be 3 + 2 (sector configuration, 3 regular TRXs and 2 super TRXs).

3.2.6. Micro cell Calculations

Micro cellular dimensioning follows the principles defined for macro layer and IUO. However, there are some details that must be handled differently for micro cells compared to macro layer. This chapter presents the basic procedure and formulas how micro cellular dimensioning is done. The previous chapters are referred if calculation principles are already presented.


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In the previous chapters the general parameters needed in dimensioning were described. The parameters were

The total number of channels available for micro cellular layer (regular + super)

Location probability for micro cells Frequency reuse numbers

Micro cells can be used to improve coverage (specially indoor coverage) or increase capacity in a certain area. Depending the usage of micro cells dimensioning can be done differently.

The area of micro cell is calculated in a similar way as the area of macro cell is calculated. In micro cell layer Okumura-Hata would not be a good propagation model. Walfish-Ikegami propagation model is more suitable for the calculations. The model is described in work instructions Power Budget Calculations.

Area of a site depends on the number of sectors and the antennae used. The following table can be used when calculating the cell/site area.

Table 4. Area of the cell in function of cell range R.

Number of sectors

Type of site Area (default)

1 Omni 2.6 x R2

1 Sectored 0.65 x R2

2 Sectored 1.3 x R2

3 Sectored 1.95 x R2

4 or more Sectored 2.6 x R2

For micro cell omni, one-sector and two-sector –base stations are the most common.

If capacity is the driving force in micro cell calculations, the capacity of one micro cell should be known. As in IUO calculations truncking gain could be taken into account.

Umbrella cellMicrocell

On this area both microcelland umbrella TRXs canprovide service.

Figure 10. Micro cellular network. On micro cell area both umbrella and micro cell can provide service


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Truncking gain in micro cellular network is not very high because capacity of the time slots in overlay are shared by both the subscribers in micro and macro layer. This means that every time slot is potentially shared by many subscribers. That is why the capacity can be calculated separately for both layers without making remarkable error. The following table shows that the truncking gain with different cell sizes in continuous micro cellular network. The percentage presents relative size of micro cell compared to umbrella cell.

Table 5. Truncking gain in micro cellular network. One TRX in overlay and one TRX in micro cell. Micro cell area is relative to overlay cell. The reference level in the calculation has been 1+1 configuration where TRXs are in different cells.

uCell Area Total Traffic GainRelative (%) Erl %

0 5.62 0.0 %10 5.62 0.0 %20 5.62 0.0 %30 5.62 0.0 %40 5.63 0.2 %50 5.68 1.0 %60 5.80 3.2 %70 6.04 7.6 %80 6.47 15.2 %90 7.14 27.0 %100 8.10 44.2 %

Table 5 shows that if there are several micro cells under one umbrella cell truncking gain is low. If micro cells are small compared to macrocells and the number of micro cells is high enough within one macrocell area, the capacity of one micro cell can be estimated simply assuming that there is no truncking gain. This means that capacity is calculated based on the number of TRXs / sector in micro cell as it calculated for overlay. The number of TRXs / sector is calculated based on the base station hardware, frequency reuse and frequency band dedicated for micro cells.

When the total traffic of micro cell is known the total number of micro cells is calculated by dividing the total traffic of micro cellular layer by the traffic of one micro cell.


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3.2.7. Dual Band

In dual band service is provided by two or more networks that are independent or partly independent. Dual band can be realised with

dual band base station two base stations co-located no co-located elements

Currently NetDim assumes that there are no co-located base stations. This means that each system is calculated separately based on the given inputs. For example, the total number of sites is a sum of all sites in every system. In practise some of the sites, if not all, would be used by all the systems.

3.2.7. Frequency Hopping

Frequency hopping is one capacity enhancement that can be used to increase the maximum capacity of the network. In NetDim frequency hopping would be taken into account by decreasing the corresponding frequency reuse number.

Currently it is not yet clear how much frequency hopping will decrease frequency reuse number. However, the magnitude could be around 30% – 40% but the actual gain depends the environment and how well the network will be made.

3.3. Number of sites

NetDim calculates the number of sites based on coverage and capacity requirements. First the number of sites is calculated for coverage. NetDim uses the maximum cell range and K factor to calculate the maximum site area. Next the total area is divided by the average site area and output is the number of sites.

If the sites needed to fulfil coverage requirements with one TRX per sector cannot provide enough capacity NetDim increases the number of TRXs until the provided traffic is high enough. If the traffic demand is very high or base stations cannot provide as high capacity as needed, NetDim increases the number of sites.

The number of sites needed for coverage may change when NetDim is increasing TRXs because combiner loss depends on the number of TRXs per sector. For this reason NetDim is iterating the number of TRXs to fulfil both coverage and capacity requirements.


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3.3.1. Triggers between systems and layers

In NetDim user can defined triggers that are used to divide traffic between different systems or layers. There are three different trigger points which user can define between two layers. The trigger point options are as follows.

No trigger, layers are calculated separately, Coverage vs. Capacity, on the staring layer no sites are added to

increase capacity, i.e. the maximum cell range of each starting station is used,

Cell range vs. Max = nn %, on the staring layer sites are added to get more capacity until cell range vs. maximum cell ranges equals to nn %. In this option the number of sites is determined by capacity, and coverage is better than required.

Triggers can be defined between macro and micro layers within the same system as well as between layers in two different systems.

The following example shows how triggers can be used to divide traffic between layers.

3.3.2. Example: Capacity enhancement triggers

Operator has plans to operate GSM 900 and GSM 1800 networks. Currently, the existing GSM 900 network is congested and operator things the ways to increase capacity to meet capacity requirements in the future. There are following options available.

Intelligent underlay overlay for GSM 900 micro cells for GSM 900 dual band - GSM 1800

Operator may want to build his network in following way. Firstly, IUO will be taken into use when needed. Secondly, micro cells are introduced when macro layer together with IUO cannot handle traffic demand. However, few sites in macro layer can be added to increase traffic. Finally, if micro cells cannot provide enough capacity some of the subscribers are directed to 1800 MHz band. In the same time there are some subscribers using only 1800 MHz band.


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The described case would lead to the following triggers. Firstly, for GSM 900 regular layer IUO introduction phase should be 1 to make sure that IUO is taken into use when needed. The IUO introduction phase tells the phase when IUO is taken in used if needed. Secondly, there should be a trigger point between GSM 900 macro and GSM 900 micro layer. The trigger could be Cell range vs. Max = 90%, to allow some extra site in macro layer to increase capacity. With this trigger new sites are added in GSM 900 macro layer until cell range vs. max. range is 90%. In this case user do not have to entry any area or subscribers for micro layer. For GSM 1800 layer user should enter some subscribers because there were pure GSM 1800 users in the network. In addition to this user should define trigger point between GSM 900 micro layer and GSM 1800 macro layer to direct possible extra traffic from GSM 900 to GSM 1800 network. The trigger point should be Coverage vs. Capacity.

In this example IUO is used only in GSM 900 macro layer. When using IUO user should pay attention to frequency reuse and frequency bands to get optimum dimensioning. If IUO is not needed NetDim combines the channels given for regular and super reuse layer and uses all these channels for regular. When IUO is taken into use channels are used as given in reuse table.

3.4. BTS access transmission

3.4.1. General

This chapter describes transmission between base stations and controllers and between base station and switch. Similar transmission module can be applied between controller and switch with some modifications. Transmission calculation is based on the tool developed by Junshu Zhang.

3.4.2. Common information

The transmission capacity need by each network element can be calculated with the following ways.

Based on hardware, for example the number of TRXs, Based on traffic - Erlang B formula, Based on traffic - Erlang C formula, Combination of hardware and traffic.

In NetDim transmission capacity calculation can be done by using hardware, Erlang B or Erlang C.


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3.4.3. Common information for base station

In this chapter the inputs, outputs and calculations are described more detailed. The transmission capacity need can be calculated based on hardware or Erlang B or C formulae. If hardware is used in calculations the following formula is used.

Capa aTraf RFUnitsTraf Equation 14where

CapaTraf Transmission capacity needed for trafficATraf 64 kb/s time slots needed for single RF unitRFUnits RF units per site

If Erlang formulae are used to calculate transmission capacity of a site the following formula is used.

Capa ErlangC bp traf qu clTraf ( , , , ) Equation 15where

CapaTraf Transmission capacity needed for trafficBp Blocking probabilityTraf Traffic of a siteQu Queuing timeCl Call length

If queuing time is zero Erlang C formula equals to Erlang B formula.

If signalling capacity is calculated based on hardware. There are three possible signalling needs. RF unit, sector and BTS may have signalling needs. These three needs in the following formulae define signalling capacity need. Signalling need of a base station consists of the signalling need for TRX, sector and base station. All these may not be used in all systems.

Capa aSig RFUnits aSig Secs aSigSig RFUnit BTS sec Equation 16where

CapaSig Transmission capacity needed for signallingaSigRFUnit Signalling need for a single RF unitRFUnits RF units in a BTSaSigsec Signalling need for a single sectorSecs Number of sectors in a BTSaSigBTS Signalling need for a BTS

Based on calculation above the total capacity need can be presented by the following formula.

Capa Capa Capatot Traf Sig Equation 17where


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CapaTot Transmission capacity needed for a BTSCapaTraf Transmission capacity needed for trafficCapaSig Transmission capacity needed for signalling

3.4.4. Number of links for different topologies

Point-to-Point

The number of links for point-to-point topology is derived with the formula below.

Links T sitesTperLinkPtoP PtoP

max ,1

CapaTot Equation 18

whereLinksPtoP Number of links for point-to-point topologyTPtoP Percentage of point-to-point topologyCapaTot Transmission capacity need of a network

elementTperLink Capacity of a link in traffic channelssites Number of sites

Percentage of point-to-point topology tells how many percentages of sites are connected to the controller with point-to-point links. Capacity of link in traffic channels tells how many traffic channels one link can carry.

Multidrop chain

The number of links for chain topology is derived with the formula below.

LinksT sites LperC

ChainL

ChainLLperC TperLink

ChainChain Chain

Chain

,

CapaTot

Equation 19

whereLinksChain Number of links for chain topologyTChain Percentage of chain topologyCapaTot Transmission capacity need of a network elementTperLink Capacity of a link in traffic channelssites Number of sitesLperCChain Max. links per connection for chain topology


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If chain length is less than one, instead of equation 19 the formula for point-to-point connections is used. In chain, multidrop loop and star topology calculations capacity of one link is replaced by capacity of the connection. This means that between two network elements there can be more than one link. For example, if there are microwave radios used capacity of one connection can be 4 x 2Mb/s. Also, capacity need for one base station can be close to 30 time slots (BTS 4 + 4 + 4). In this case in chain there could be 4 BTSs. If the assumption is one link per connection the only possible topology would be point-to-point because in one link there is not enough capacity to handle more than one BTS.

Multidrop Loop

The number of links for loop topology is derived with the formula below.

LinksT sites LperC

Lenght

LenghtLperC TperLink

LoopLoop Loop

Loop

LoopLoop

,

CapaTot

Equation 20

whereLinksLoop Number of links for star topologySites Number of sitesTLoop Percentage of loop topologyTperLink Capacity of a link in traffic channelsLenghtLoop Length of a loopCapaTot Transmission capacity need of a network element

If loop length is less than one, instead of Equation 20 the formula for point-to-point connections is used.

Star

The number of links for star topology is derived with the formula below.

LinksT sites

TperLinkStarStar

CapaTot Equation 21

whereLinksStar Number of links for star topologysites Number of sitesTStar Percentage of star topologyTperLink Capacity of a link in traffic channelsCapaTot Transmission capacity need of a network element

3.4.5. Total number of link

The total number of links is calculated as a sum of different topologies.


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Links Links Links Links LinksPtoP Chain Loop Star Equation 22where

Links Total number of linksLinksPtoP Number of links for point-to-point topologyLinksChian Number of links for chain topologyLinksLoop Number of links for loop topologyLinksStar Number of links for star topology

3.4.6. Cross Connection equipment

Generally, cross connection equipment is used when using loops or stars in transmission. However, the calculation information can be given for all topologies.

Formulae

The number of cross connection equipment is calculated with the following formulae.

Number of cross connection equipment for point-to-point topology.

CrossCn Links

SizeCrossCPtoPPtoP PtoP

PtoP

2 Equation 23

wherenPtoP Percentages of point-to-point links using cross

connection equipmentLinksPtoP Number of links in point-to-point topologyCrossCPtoP Number of cross connection equipment for point-

to-pointSizeCrossCPtoP Size of cross connection equipment in number of

links (point-to-point)

Number of cross connection equipment for multidrop chain topology.

CrossCn Links

SizeCrossCchainChain Chain

Chian

2 Equation 24

wherenChain Percentages of multidrop chain using cross

connection equipmentLinksChain Number of links in chain topologyCrossCstar Number of cross connection equipment for chainSizeCrossCChain Size of cross connection equipment in number of

links

Number of needed cross connection equipment for multidrop loop topology.


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CrossCn Links

SizeCrossCloopLoop Loop

Loop

3 Equation 25

wherenLoop Percentages of multidrop loop links using cross

connection equipmentLinksLoop Number of links in loop topologyCrossCLoop Number of cross connection equipment for loop

topologySizeCrossCLoop Size of cross connection equipment in number of

links

For star configuration the formula is as follows.

CrossC

n links sites

SizeCrossCstarStar Star

Star

Equation 26

wherelinksStar Number of links in star topologynStar Percentages of star links using cross connection

equipmentCrossCStar Number of cross connection equipment for loop

starSizeCrossCStar Size of cross connection equipment in number of

linkssites Number of sites in star topology

The total number of cross connection equipment

The total number of cross connection equipment is calculated with the formula below.

CrossC CrossC CrossC CrossC CrossCloop star chain PtoP Equation 27

3.4.7. ET cards

The number of ET cards is calculated based on the number of links needed. Calculation is simple as the following formula shows.

ETsLinkspET links

SizeET

Equation 28

whereETS Number of ET cardsLinkspEt Number of links per ET cardSizeET Size of ET cards (in number of links per ET

cards)


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3.4.8. Submultiplexing

Submultiplexing is optional in transmission. It can reduce the needed number of links between network elements.

If submultiplexing is used between two network elements the interface can be divided into two interfaces, one that is submultiplexed and the one after transcoder. The transmission capacity in submultiplexed interface is given in traffic channels.

The number of links after submultiplexer (for example, Ater in GSM) is calculated with the following formula.

LinksCapacity

LinkCapaASMSM

Equation 29

whereLinksASM Number of links after submultiplexerCapacity Transmission capacity needLinkCapaSM Capacity of one link with submultiplexing

If it is needed to calculate the links after transcoder the formula below can be applied.

LinksCapacity

LinkCapaATC Equation 30

whereLinksATC Number of links after transcoderCapacity Total number of traffic channels neededLinkCapa Capacity of one link without submultiplexing

3.5. Controller calculation

Controller are used between base stations and switches. In GSM they are called as base station controllers (BSC) but in some systems functionality of a controller is integrated a switch.

In NetDim controllers can be dimensioned with two criteria. Criteria are RF units or traffic.

Currently one criterion can be selected for each system. For example, in GSM the number of RF units would be the right criterion.


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Number of controllers can be calculated manually when user gives the number of each controller type manually. This allows user to take into account geographical facts as well as spare capacity. However, dimensioning for controllers can be calculated automatically, as well. If automatic calculation is used NetDim selects the controllers in a way that first, it minimises the number of controllers and then their sizes. User can select the controllers that NetDim is allowed to use.

Automatic calculation

Controllers are selected. By default all controllers that are defined for the system(s) of the area selected. User can remove from the group the controllers that he/she does not want to use.

Number of largest controllers. NetDim selects first the largest controller that is available. The needed capacity is divided by the capacity of the largest controller. The result is rounded down to get the number of largest controllers.

nContTotalCapacity

controllerhighi

max( )

Equation 31

The capacity that is not covered with the largest controllers is calculated by the following formula. This capacity is handled with the smallest possible controller that is available. This means that the capacity of this controller must be higher than Capacitylow.Capacity TotalCapacity nCont Capacitylow high high

Equation 32

Number of low capacity controllers is always one except when the only possible controller that can handle Capacitylow is the largest controller. In this case the number of largest controllers is increased by one.

Controllers are calculated for each system. If there are controllers that can handle several systems, for example GSM 900 and GSM 1800, the capacities of the base stations are first consolidated and then the number of controllers is calculated as it is calculated for one system.

4. PLAN CALCULATION

A plan consists of several regions. The most of calculation is done in regions but there are two main areas that are covered in plan level. The areas are switch calculation and transmission between controllers and switches. Also, in plan the results from regions are consolidated.

4.1. Switch calculation

Switches connect calls between subscribers. In GSM switches are called mobile switching centres (MSC).


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In NetDim switches can be dimensioned with several criteria. Criteria are subscribers, RF units or traffic.

Switch calculation is similar to controller calculation in which both manual and automatic calculation is possible. See controller calculation chapter for more details.

4.2. Transmission in a plan

4.2.1. General

Transmission for a plan is very similar to the transmission in region. The main differences are related to the source of capacity. In region transmission capacity is calculated based on base stations. In plan transmission the starting point can be the transmission capacity need of base stations but also it can be for example traffic generated by subscribers.

4.2.4. Transmission for controller - switch interface

Transmission calculation for controller - switch interface differs from transmission calculation methods described earlier slightly. However, transmission configuration is similar to the other transmission solutions. In this chapter the differences in calculation are explained.

Transmission capacity

In transmission configuration it is possible to select either hardware or traffic based capacity calculation. If hardware is selected for calculation method the total number of RF units in a plan is divided for each controller type based on the system of the controller. Transmission capacity is calculated using the number of RF units per controller and time slots per RF unit that is defined in transmission configuration.

If traffic is selected for capacity calculation method, total traffic generated by subscribers is divided for each controller type. Transmission capacity need is calculated with either Erlang B or Erlang C.

CapacityRFUnits TSperRFUnit HW selected

Erlang bp traf qu cl traffic selectedConti

,

, , , ,

Equation 33

where


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Capacity Transmission capacity needed for transmission

TSperRFUnit Time slots needed per RF unitRFUnitsCont RF units per controller typeErlang Erlang B or C formulabp Blocking probabilitytraf Traffic per controllerqu Queuing timecl Average call length

If queuing time is zero Erlang C formula equals to Erlang B formula.

Excluding transmission capacity calculation described above transmission in plan is calculated similar way as in region. For details see page 28 onwards.

4.3. Consolidation of region calculation

In a plan the results from regions are consolidated. If there are many regions in a plan it is almost impossible to get a clear picture of the plan without a good summary of the results.

4.3.1. Region inputs in a plan

All the main inputs are summarised in a plan. The total number of subscribes, total traffic and the covered area are presented in each phase. This way user can see how the penetration develops during the roll-out.

User should note that on summary all areas entered in regions are added together. This applies to macro and micro layers, as well.

4.3.3. Configurations base stations and controllers in Excel

In Excel sheets which can be generated in NetDim configurations for base stations and controllers are given. For each region the needed configurations are shown and on summary the results are consolidated from the areas.

4.3.4. Transmission configurations

The results from transmission calculation in regions are summarised in a plan. The number of links for each system is added up for each phase. Also, the number of cross connection equipment and ET cards are calculated.

5. CONFIGURATION OF NETWORK ELEMENTS

In NetDim different network elements may have different versions depending on the parameters that have been used. Always the calculation follows the same methods but the selected parameters have an effect on the results. In this chapter the configuration of each network element is described.


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5.1. Base station

Base station is the most complex object in NetDim. Configuration of the base station is divided into three parts. The parts are Global, Sector and Options and they are presented in different tabs in base station configuration.

Global sheet include all the general parameters related to a base stations. The parameters are listed below.

Parameter Explanation

System BTS belongs to one systemUsed for BTS can be used to provide only coverage, only

capacity or bothuCell BTS can be used in macro or in micro layerIUO BTS may have IUO featureAntenna height The height of antenna Sensitivity Dynamic sensitivity defined by BTS product lineTX max. power Maximum output power of TRXJumper loss (optional)Cable loss (optional)Duplex filter loss (optional)Connector loss (optional)Propagation model Okumura-Hata or Walfish-IkegamiCombiner loss Combiner loss can be set for different TRX counts

(optional)Transmission capacity: RF Units

Transmission capacity needed for each RF Unit. (time slots in PCM link), in GSM TRXSig

Transmission capacity: Sector

Transmission capacity needed for each sector. (time slots in PCM link)

Transmission capacity: BTS

Transmission capacity needed for each BTS. (time slots in PCM link), in GSM OMUSig

Antenna gains Antenna gains for transmitting and receiving endsDiversity gains For uplink and downlink directions

Combiner loss calculation is improved compared to the previous NetDim version. Loss is calculated by using linear approximation and the known combiner losses. The figure below shows an example.


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1 TRX 2 TRXs 3 TRXs 4 TRXs

Defined combiner loss value

Combiner Loss

TRXs

Figure 11. Combiner loss calculation. If only one value is given, for all TRX counts the same combiner loss is used. In cases where more than one value is given NetDim calculates combiner loss by using linear approximation. If the TRX count is below the lowest defined value, the lowest value is used. Also, if the TRX count is above the highest given value, it is used for combiner loss. If TRX count is between two given values, combiner loss is calculated as described in the figure.

On Sector sheet the inputs related to sectors is given. In calculations the number of sectors and the maximum number of TRXs are important as well as K factors. If only one sector is used in a BTS it is possible that the antenna configuration is directional or omni. The selection can be done on Sector sheet.

Options sheets include data related to low noise amplifier (LNA), booster (power amplifier installed in base station cabinet) and CEMA (cell extension masthead amplifier, not Nokia’s product at the moment).

LNA is used to improve uplink by compensation cable losses and improving sensitivity of system. LNA calculation is described in work instructions Power Budget. Booster has higher output power than regular TRX so it can be used to improve downlink. When using booster cable and combiner losses are taken into account.

If using CEMA there is no losses because CEMA is installed in a mast and cables from antenna to CEMA are usually short (assumed 0 dB loss).

5.2. Mobile

User can create mobiles for the systems that exists. The inputs must/can be given are.

System, can be selected among the existing systems


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Class (not used in calculation) Receiver sensitivity in dBm Antenna height (in meters) Receiving antenna gain Transmitter antenna gain Output power in dBm Cable loss (optional) Connector loss (optional)

If creating a new mobile or terminal user has to give a name that is used in dimensioning. The name can be used to differentiate mobiles or terminal.

5.3. Controller

User can configure controller based on the system of the controller. For each system user has to give the calculation criteria for controllers and switches. For this reason a controller has only one calculation criterion available. User can define the capacity of controller based on calculation criterion. For example in GSM the capacity of controller is given in number of TRXs. The possible calculation criteria are as follows.

Number of RF units Traffic

In addition to calculation criteria user can define what systems the controller supports.

5.4. Switch

Configuration of switch is very similar to controller. Also for switches the system defines what is the calculation criterion. Criterion is the same as for controllers except number of subscribers is also available.

5.5. Transmission

User can create several transmission options for different purposes. Possible interfaces are Base station - Controller Base Station - Switch Controller - Switch

For each interface there are several inputs. The inputs can be defined to region/plan specific inputs and general inputs. Region/plan specific inputs are

Transmission interface selection Percentage for point-to-point connections


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Percentage for multidrop chain connections Percentage for multidrop loop connections Percentage for star connections

Region/plan inputs are given for each region and plan.

General parameters are given for each transmission object in transmission configuration. The given values are used in all regions that are using this transmission object. For this reason the changes will affect even in plans that are made before the changes. General inputs are listed below.

Interface selection for the transmission object Submultiplexing usage and capacity of submultiplexed link Cross connection equipment usage, size of cross connection equipment

and percentage of links using cross connection equipment Transmission capacity calculation method Time slots needed per RF units Blocking probability (if traffic is used as capacity calculation method) Queuing time (if traffic is used as capacity calculation method) Call length (if traffic is used as capacity calculation method) Capacity of one link in time slots Number of ET cards per one link Capacity of an ET card in number of links (currently 1 or 2) Number of traffic channels per one time slot in a link Maximum number of links between two network elements.

User can define several transmission objects for each transmission interface.


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7. WIRELESS LOCAL LOOP AND DIMENSIONING

There are some significant differences between cellular and WLL dimensioning. In this chapter those differences are explained. Also, at the end of this chapter six different approached of building a WLL network are presented.

In WLL network mobility is restricted to few cells or it is totally forbidden. This can help network planning because the neighbour in WLL list do not have to include all the neighbouring cells which would be needed in cellular network. By leaving out intefering neighbours (or interfering frequencies) on the list, capacity of the network can be improved.

If fixed WLL terminals are used the location of the terminal can be chosen to get best performance. The location may be chosen because of coverage. Then the location providing the highest field strength is selected. If location is selected because of capacity the reason for the selection can be the lowest interference level or the number of possible servers.

External antennae can be used in WLL terminals. Specially, in rural areas external antennae can provide much better coverage because of the following facts. Firstly, when using external antennae network can be building for outdoor coverage instead of indoor coverge. Depending on the used building materials the advantage can be from 5 dB to 30 dB. Secondly, external antennae can be directional which means higher antenna gains. Thirdly, external antennae can be installed higher, for example on the roof of the house. This can increase the cell range remarkable because there will be less obstacles in radio path. All these facts should be considered when making WLL dimensioning. If the internal antennae of the terminal are used down link diversity of 1.5 dB can be utilised because the terminal is using selective diversity scheme.

If building WLL network in city area it will be difficult to use external antennae in large scale. This means that from coverage point of view WLL may not differ much from cellular network. However, from capacity point of view, there is a difference because a little bit lower reuse numbers can be applied. This advantage is gained because there is no need to apply any margin because of mobility.

In rural areas where capacity is not constrain there can be remarkable differences between cellular and WLL network. Specially, the usage of external antennae will reduce the number of needed base stations in WLL network. However, if terrain is hilly or there are some other obstacles external antennae may not give full advantage. If the maximum cell range is more than 35 km the planner should note that in these cases (cells) Extended Cell feature is needed.


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7.1. Six approaches to build a WLL network

In this chapter six different approaches to build a WLL network are described. Each case has its own characteristics that the planner should take into account.

These cases are as follows.

1) Easywave Access with mobile phones (hand phones)2) Easywave Access with PremiCell terminals3) Easywave System4) Combined Mobile and WLL network in the same coverage area5) Combined Mobile and WLL network with partially overlapping coverage areas6) Combined Mobile and WLL network using different frequencies

Easywave is a brand name for Nokia’s WLL solutions. Easywave Access is the solutions based on BTSs and DAXnodes that are connected to local exchanges. Easywave System is a WLL solution that is build by using the existing GSM hardware (i.e. MSCs, BSCs, BTSs) but the design is optimised for WLL solution.

PremiCell is the name of Nokia’s WLL terminal. The name is used for 900 MHz, 1800 MHz and 1900 MHz terminals.

Because tariffs in WLL applications are usually lower than in mobile applications it is very essential to minimize both the initial investment costs as well as the operational costs. This is achieved by maximizing the capacity of each base station. In coverage limited cases this leads to maximizing the coverage area of cells with all possible ways (e.g. external antennae, six-sector-base stations, higher antenna heights in both base station and mobile end, boosters, low-noise-amplifiers, etc.). In capacity limited cases the target must be as low reuse as possible.

7.1.1. Easywave Access with mobile phones

Easywave Access with mobile phones is a network that is build by using DAXnodes instead of BSCs. Each DAXnode is connected to a local exchange via V5.1 or V5.2 interface. This type of the network is dimensioned like a standard mobile network with the following exceptions:

Instead of BSC DAXnode 5000 WLL will be used as a controller (DAXnode dimensioning is done by FIW System Marketing Manager),

Frequency reuse can be lower than in a mobile network when targeting similar quality, e.g. 9 can be used as default

Subscriber traffic is higher than in mobile network due lower tariffs


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7.1.2. Easywave Access with PremiCell terminals

If the WLL application is built for PremiCell terminals there are a few important facts. If fixed terminals are used it is possible to used external antennae to extend the coverage area of cells. This will lead to high-capacity-base stations (e.g. 4+4+4 or 6+6+6) even in suburban or rural areas and lower the overall costs of the network.

The following guidelines can be applied.

Frequency re-use 9 can be used as default (frequency hopping can be implemented)

Network will be dimensioned based on outdoor coverage because PremiCells with external antennas can be used in areas where the indoor coverage is not sufficient

Subscriber traffic is higher than in mobile network due lower tariffs Instead of BSC DAXnode 5000 WLL will be used as a controller

(DAXnode dimensioning is done by FIW System Marketing Manager)

PremiCells with external antennae will give the following benefits. MS height is 3 to 8 meters depending on the building type MS antenna net gain is 2 to 12 dB depending on the antenna gain, cable

length and cable thickness

If customer does not approve external antennas then PremiCells should be located high enough near window. In this case the following assumptions can be applied. Building penetration loss close to 7 dB MS antenna diversity gain 1.5 dB (can be implemented as down link

diversity) MS height 2 m

7.1.3. Easywave System

Easywave System is a WLL network that is built by using the GSM hardware and software. The network is build as two previous Easywave solutions except few exceptions. Firstly, all capacity and coverage enhancements features that are used in mobile networks are available in Easywave System. Because of the lack of mobility some features are providing more benefits that in mobile applications. Secondly, BSCs and MSCs are used instead of DAXnodes and local exchanges.

As in the previous cases the reduction of network cost is very essential.


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The following guidelines can be applied.

Frequency re-use 9 can be used as default (frequency hopping can be implemented)

Network will be dimensioned based on outdoor coverage because PremiCells with external antennas can be used in areas where the indoor coverage is not sufficient

Subscriber traffic is higher than in mobile network due lower tariffs Instead of BSC DAXnode 5000 WLL will be used as a controller

(DAXnode dimensioning is done by FIW System Marketing Manager)

PremiCells with external antennae will give the following benefits. MS height is 3 to 8 meters depending on the building type MS antenna net gain is 2 to 12 dB depending on the antenna gain, cable

length and cable thickness

If customer does not approve external antennas then PremiCells should be located high enough and near window. In this case the following assumptions can be applied.

Building penetration loss close to 7 dB MS antenna diversity gain 1.5 dB (can be implemented as down link

diversity) MS height 2 m

7.1.4. Combined Mobile and WLL network in the same coverage area

This network will be dimensioned like a standard mobile network with the following exceptions.

WLL traffic will be collected as far as possible using PremiCells with external antennas,

Subscriber traffic is higher than in mobile network due lower tariffs.

7.1.5. Combined Mobile and WLL network with partially overlapping coverage areas

In this case the dimensioning will be divided into two parts.

a) Mobile and WLL in the same areab) WLL only area

a) Mobile and WLL in the same area


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This case is dimensioned like Combined Mobile and WLL network in the same coverage area.

b) WLL only area

This case is dimensioned like Easywave Access of System WLL case.

7.1.6. Combined Mobile and WLL network using different frequencies

In this case WLL network will be planned mostly as separate network. However, the case can be divided into two cases. If mobile and WLL networks are using the same frequency band, BSC capacity and BTS sites can be shared when panning network. In practice this would be achieved by, for example, combining both frequency bands and reuse numbers. This could lead to reuse of 20 to 25 but in the same time more band would be in use. Also, traffic figures should be added before making the calculations. In this way the capacity of the network is shared by mobile and WLL subscribers.

If mobile and WLL networks are using different frequency bands (e.g. GSM900 and GSM1800) networks should be planed as a dual band network where WLL aspects are taken into account. When using dual band approach the capacity of BSCs, MSCs and transmission can be shared.

The assumption has been here that the mobile and WLL networks are covering roughly the same area. If the assumption is not valid, it may be better to make two separate dimension plans in which the systems are separated.

The appendix 4 gives antenna recommendations for WLL terminals. Also, guidelines for cable loss calculation are presented.

8. RELATED DOCUMENTS

Power Budget Calculations, Work InstructionNetDim, User’s Reference Manual

DOCUMENT REVISION HISTORY

DATE ISSUE

AUTHOR SUMMARY OF CHANGES

31 Feb 1998 1.0 Matti Manninen 1st release


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APPENDICES

Appendix 1. BTS RX RF-Input Sensitivity with Mast Head Amplifier

To calculate the RF input sensitivity for BTS when a mast head amplifier is used, it is necessary to apply the Fries’ formula for cascaded networks. The Fries’ formula is presented in the following equation.

F F F G F G GA MHA cable MHA BTS MHA cable ( ) ( )1 1 Equation 34

FMHA is the noise factor of the mast head amplifier and the noise figureNFMHA of the mast head amplifier is assumed to be about 2 dB. Fcable is the noise factor of the cable between mast head amplifier and base station. The noise figure NFcable for the cable is the cable loss in dB (lets assume it to be 3 dB). FBTS is the noise factor of the base station and it can be calculated by using following equation.

FS N

S N

S kT W

E NN kT Wi i i

bi

0 0

0

00, ,

Equation 35

-where E Nb 0 is the receiver output signal to noise ratio, k is the Boltzman constant, T0 is 290K, F is the noise figure for the receiver, and W is bandwidth of 271 kHz (54 dB).

The noise figure NFBTS in dB can now be calculated as follows (assuming that the sensitivity of the base station is -104 dBm):

NF dBm dBm dB dB dBBTS 104 174 54 8 8( )

GMHA is the gain of the mast head amplifier and it can be assumed to be 10

dB. Gcable is the gain of the cable between base station and mast head amplifier and the value is NFcable .

The noise figure in point A (in Figure 12) is:

FA 10 10 1 10 10 1 10 10 2 740 2 0 3 1 0 8 1 0 3, , , ,( ) ( ) ,

NF dBA 10 2 74 4 3810log , ,Equation 36

The RF input sensitivity at the antenna port, point A in Figure 12 can be calculated from equation 36.


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BTS Rx

MHA

Antenna portPoint A

NFMHA

GMHA

Cable

Gcable

Figure 12. BTS MHA (or LNA) connection.

S S NFA W A Equation 37

where SW is the sensitivity of the system (BTS + MHA) when the noise figure of independent mast head amplifier is set to zero dB (in Equation 35) because the noise figure of the whole system (BTS + MHA), NFA, has to be taken into account instead of individual noise figures.

S dB dBm dB dB dBmW 0 174 54 8 112

The result of Equation 37 can be seen from Table 6 when different set of parameters for NFMHA calculations.

Table 6. RF input sensitivity calculation results when MHA is used. The first row is the case 1 and the second row is case 2.

NFMHA NFcable GMHA Gcable NFBTS NFA SWSensitivity

2 dB 3 dB 10 dB -3 dB 8 dB 4,7 dB -112 dBm -107,3 dBm

2,3 dB 4 dB 12 dB -4 dB 6 dB 3,6 dB -112 dBm -108,4 dBm


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Appendix 2. Sensitivity

Sensitivity levels of mobile and base station are given in GSM recommendations (GSM 05.05).

Table 7. Base station and mobile station sensitivities according to GSM recommendations (GSM 05.05).

Type Sensitivity

DCS mobile station -100 dBm (42 dBV/m)GSM hand held -102 dBm (35 dBV/m)GSM mobile station -102 dBm (33 dBV/m)Normal BTS (GSM/DCS) -104 dBm (33/38 dBV/m)

In dimensioning the sensitivity values from GSM recommendation should not be used for base stations because the guaranteed sensitivity levels are better than the ones in GSM recommendations. BTS product line will define the sensitivity levels. On the following table sensitivities of 3rd and 4th generation base stations are given.

Table 8. Typical base sensitivities in fading conditions according to BTS product line.

Type Dynamic Sensitivity

Talk Family (900 MHz) -108.5 dBmTalk Family (1800/1900 MHz) -108.0 dBm PrimeSite (900 MHz) -108.5 dBmPrimeSite (1800/1900 MHz) -108.0 dBm

For mobiles sensitivity values should be according to the GSM recommendations if the usage of different values is not agreed with the customer. For wireless local loop (WLL) applications the sensitivity values from Nokia Mobile Phones (NMP) should be used.

Table 9. WLL terminal sensitivities.

Type Sensitivity

WLL terminal (900 MHz) -102 dBmWLL terminal (1800/1900 MHz) -100 dBm 1

1) typical value -102 dBm


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Appendix 3. Isolators, combiners and filters

Isolator, combiner and filter in transmitting end will decrease output power at the antenna connector of base station. Normally, this can be compensated by increasing the output power of TRX unit. In some cases if uplink is strong output power of TRX may not be enough to balance the power budget. On the following table the losses of combiner units are presented for GSM 900, GSM 1800 and PCS 1900.

Table 10. Combiner losses for different combiner units in 900, 1800 and 1900 MHz.

Combiner type Typical loss

AFE 5.2 dBAFE with bypass 2.2 dBRTC (6 TRX) 4.5 dBRTC (1-4 TRX) 3.5 dB


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Appendix 4. Antennae for WLL terminal

The following table gives the maximum antenna gain for WLL terminal defined by Nokia. In some extreme conditions it is possible to use even higher antenna gains but before doing it, it must be agreed with account team.

Gain Window antenna

Low gain

Medium gain

High gain

900 5 dBi 4 dBi 8 dBi 12 dBi1800/1900 5 dBi 7 dBi 12 dBi 16 dBi

Cable Loss / 100m900 90dB 50 dB 20 dB 20 dB

1800/1900 105dB 80 dB 30 dB 30 dBDiameter 3 mm 5 mm 10 mm 10 mm

The maximum gains are given for external antennae used outdoors. However, it is possible to use so call window antennae with terminal. This antenna is placed on a window. Because the antenna is installed on the window building penetration loss will be lower than normally used in mobile network. Loss can be around 5 – 10 dB.

If external antennae are used the cable loss in terminal end should be included in calculations. Loss in 900 MHz band is close to 1dB/m and in 1800/1900 MHz band up to 1.5 dB/m.


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Appendix 5. Output powers

The typical output powers are presented on the following tables for GSM based systems. User has to notice that the power is measured at the output of the transmitter, not at the antenna connector.

Table 11. Output powers of base stations.

Type Power

Talk Family (900 MHz) 45 dBm 1

Talk Family (1800/1900 MHz) 45.2 dBmPrimeSite (900/1800/1900 MHz) 39 dBm

1 Output power of a TRX

Table 12. Output powers of mobiles and terminals.

Type Power

GSM 900, class IV 33 dBm 1

GSM 900, class V 29 dBm 1

GSM 1800, class I 30 dBm 1

GSM 1800, class II 24 dBm 1

GSM 1900 30 dBmNokia 09 WLL terminal (900 MHz) 33 dBmNokia 18 WLL terminal (1800 MHz) 30 dBm

1 According to GSM recommendations, GSM 05.05.


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