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Planning Guideline: Air Interface dimensioning s

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Planning Guideline:

Air Interface Dimensioning

Issued by Communication Mobile Networks Com MN PG NT NE 1 Munich © SIEMENS AG 2006 The reproduction, transmission or use of this document or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights, including rights created by patent grant or registration of a utility model or design, are reserved. Technical modifications are possible. Technical specifications and features are binding only in so far as they are specifically and expressly agreed upon in a written contract.

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Contents 0 GENERAL INFORMATION..................................................................................................................... 3

0.1 HISTORY ............................................................................................................................................... 3 0.2 ABBREVIATIONS, DEFINITIONS AND EXPLANATIONS ............................................................................ 3

1 INTRODUCTION....................................................................................................................................... 7

2 RADIO PROPAGATION ENVIRONMENT........................................................................................... 8 2.1 CLUTTER TYPES .................................................................................................................................... 8 2.2 CELL TYPES .......................................................................................................................................... 9 2.3 CHANNEL MODEL.................................................................................................................................. 9

3 POWER BUDGET PARAMETERS ....................................................................................................... 10 3.1 BTS TRANSMISSION POWER ................................................................................................................ 11 3.2 MS TRANSMISSION POWER.................................................................................................................. 12 3.3 BTS SENSITIVITY................................................................................................................................ 12

3.3.1 Sensitivity reference ports ............................................................................................................. 14 3.3.2 TMA and noise figure of the system .............................................................................................. 15

3.4 MS SENSITIVITY ................................................................................................................................. 17 3.5 DIVERSITY TECHNIQUES ..................................................................................................................... 18

3.5.1 2 branch RX diversity.................................................................................................................... 19 3.5.2 4 branch RX diversity.................................................................................................................... 20 3.5.3 TX diversity Antenna Hopping ...................................................................................................... 21 3.5.4 TX diversity Time Delay................................................................................................................ 22

3.6 RX/TX ANTENNA GAIN....................................................................................................................... 24 3.7 COMBINER INSERTION LOSSES ............................................................................................................ 24

4 PROPAGATION RELATED PARAMETERS...................................................................................... 26 4.1 LOG-NORMAL FADING AND STANDARD DEVIATION............................................................................. 26 4.2 INDOOR CASE...................................................................................................................................... 28 4.3 INTERFERENCE DEGRADATION MARGIN .............................................................................................. 28 4.4 BODY LOSS ......................................................................................................................................... 29

5 MAXIMUM ALLOWABLE PATHLOSS CALCULATION ............................................................... 30 5.1 EQUIVALENT ISOTROPIC RADIATED POWER EIRP ........................................................................... 30 5.2 POWER BUDGET CALCULATIONS ......................................................................................................... 30 5.3 (E)GPRS LINK BUDGET ...................................................................................................................... 34 5.4 POWER BUDGET BALANCE .................................................................................................................. 37

6 RADIO PROPAGATION PREDICTION .............................................................................................. 38 6.1 PROPAGATION SLOPE .......................................................................................................................... 38 6.2 ONE SLOPE MODEL.............................................................................................................................. 39 6.3 TWO SLOPE MODEL ............................................................................................................................. 41 6.4 CELL SIZE EVALUATION...................................................................................................................... 42

7 GRID PLANNING .................................................................................................................................... 45 7.1 OMNI CELL.......................................................................................................................................... 45 7.2 3-SECTORS SITE................................................................................................................................... 46 7.3 6- SECTOR SITES.................................................................................................................................. 47 7.4 2- OR 1-SECTOR SITES (ROAD SITE) ..................................................................................................... 49

8 LINK BUDGET APPLICATION CASES .............................................................................................. 51

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0 General Information

0.1 History Version Date Reason for Changes 1.0 26.06.2006 1st version of document

0.2 Abbreviations, Definitions and Explanations Abbreviation Definition, explanation 8PSK 8 Phase Shift Keying 2RX Receiver diversity: 2 RX paths 4RX Receiver diversity: 4 RX paths A1/2 Frequency dependent partAcell Cell coverage ACOM Antenna Combiner AH Antenna Hopping AMCO Amplifier Coupler Asite Area covered by one site B Receiver bandwidth BCCH Broadcast Control Channel BER Bit Error Rate BLER Block Error Rate BSRX sensitivity BTS CU sensitivity BSTX pwr BTS CU output power BSTX pwr_max Peak RF power at CU BTS Base Transceiver Station BTSone Classic BTS (e.g. BS20, BS60) BTSplus Base Transceiver Station Second Generation (e.g. BS240) c Clutter correction factor C/(N+I) Carrier to noise and interference ratio C/N Carrier to noise ratio CDF Cumulative Distribution Function CS Circuit Switched CU Carrier Unit D Site-to-site distance d(hMS) MS antenna height correction DCS Digital Communication System DIAMCO Di - Amplifier Multi Coupler DL Downlink du Dense urban

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Abbreviation Definition, explanation Eb Energy of a single data bit Eb/No Signal to noise ratio per bit ECU EDGE Carrier Unit ECU V3 ECU version 3.0 EDGE Enhanced Data rates for GSM Evolution EGPRS Enhanced General Packet Radio Service EIRP Equivalent Isotropic Radiated Power erf Error function ERP Equivalent Radiated Power ETSI European Telecommunications Standards Institute f Frequency F BTS Noise figure of BTS at antenna port FDUAMCO Flexible Duplexer Amplifier Multi Coupler FER Frame Erasure Rate FH Frequency Hopping FICOM Filter Combiner FlexCU Flexible Carrier Unit Fx Noise factor γ Propagation slope GDL Antenna BTS TX antenna gain GDL TX div Downlink diversity gain GMS antenna MS antenna gain GMS antenna MS antenna gain GMSK Gaussian Minimum Shift Keying GPRS General Packet Radio Service Gr Antenna gain GSM Global System for Mobile Communications Gt Transmitter antenna gain GUL antenna UL antenna (RX antenna) gain of the BTS GUL diversity UL diversity gain Gx Power amplification factor hb Antenna height hBS Height of base station hMS Height of MS HPDU High Power Duplexer Unit HT Hilly Terrain HT 100 Hilly Terrain at 100 km/h HW Hardware IR Incremental Redundancy IURS Improved Uplink Receiver Sensitivity

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Abbreviation Definition, explanation k Boltzmann constant L System loss factor (e.g. cable and combiner loss) LA Link Adaptation Lbackoff Static power reduction Lbody loss Body loss Lcombiner loss Antenna combiners insertion loss LDL cable_loss DL cable loss LHPDU HPDU loss Lincar Incar losses Linterference deg Interference degradation margin Llog-normal margin Log-normal fading margin LMS cable loss RF cabling loss of the MS LNF Low Noise Filter LNF margin Log Normal Fading margin LOS Line Of Sight Lpenetration Penetration losses LUL cable loss BTS UL antenna cabling loss MAPL Maximum Allowable Pathloss MCS Modulation and Coding Scheme MS Mobile Station MSRX sensitivity MS sensitivity MSTX pwr max Peak RF power of the MS MUCO Multi Coupler N Number of sites required to cover certain area n Propagation model exponent NF Noise Figure No Noise spectral density P Area to be covered by sites P Noise Thermal noise PCS Personal Communication System PDCH Packet Data Channels Pr Power at the receiver antenna PRACH Packet Random Access Channel PS Packet Switched PSK Phase Shift Keying Pt Transmitter power R Cell range r Distance between the base station antenna and the mobile RA250 Rural Area 250 km/h

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Abbreviation Definition, explanation RBER Residual Bit Error Rates RF Radio Frequency RLC Radio Link Control RX Receiver si Distance dependent part su Suburban T Noise temperature T bit Duration of the bit time TMA Tower Mounted Amplifier TRX Transmitter/Receiver TS Timeslot TU3 Typical Urban 3 km/h TU50 Typical Urban 50 km/h TX Transmitter U Urban UL Uplink USF Uplink State Flag V-pol Antenna with vertical polarization plane x0 Minimum RX input power for (x) % location probability X-pol Antenna with ± 45° polarization planes λ Wavelength σ Standard deviation σ LNF(i) Indoor standard deviation σ LNF(o) Outdoor standard deviation σ LNF(o+i) Standard deviation for both indoor and outdoor Minimum RX input power for 50% location probability

x

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1 Introduction

This document describes Air interface network dimensioning that is to be carried out in a very early phase of network implementation, i.e. prior to any installation or network elements. The purpose of Air interface dimensioning is to estimate how the available geographical area that is to be served by the GERAN radio network can and shall be covered, i.e. how the available geographical area can be subdivided into cells and areas served by particular sites. The following section contains the description of the link budget calculation. It starts with the discussion of the propagation environment in the chapter 2. Then hardware related link budget parameters are described (chapter 3). Afterwards parameters related to the propagation phenomena are outlined (chapter 4). The Maximum Allowable Pathloss can then be calculated based on the directions and formulas presented in chapter 5. With the Maximum Allowable Pathloss, the cell range can be estimated according to the propagation model equations given in Prediction Models description (chapter 6). After selection of an appropriate network layout, according to the information from the Grid Planning section (chapter 7), the site area and the number of required sites can be calculated.

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2 Radio propagation environment

Mobile radio communication takes place in an environment which varies substantially in the propagation characteristics. The most important propagation factors that define the mobile environment for a particular area are: • Physical terrain structure (heights, morphology), • Man-made structures (number, height, materials), • Foliage and vegetation characteristics, • Weather conditions. Impact of these factors depends on the radio frequency at which the system operates. Moreover, it is influenced by the speed of the mobile. Propagation effects and their magnitude for slow-moving or stationary mobiles are quite different from those for mobiles that move with high speeds. The random nature of the radio propagation requires modelling of the radio channel in a statistical fashion, based on the measurements. Firstly, a propagation model which characterizes signal strength over large transmitter-receiver separation distances is applied. Then slow fading and multi-path fading is modelled.

2.1 Clutter types Physical terrain structure impacts mobile radio signal propagation significantly. In order to distinguish different terrain morphology, special 'clutter types' are defined. During the dimensioning phase, these clutter types are reduced to the main classes: dense urban, urban, suburban, rural and road. Urban The clutter type 'urban' represents areas with high building density as found mostly in urban environments consisting of large buildings, offices, and shops etc. where adjacent buildings are clearly separated from each other by free space. The typical urban scenario should have a mean amount of streets with no distinct street orientation pattern, the major streets are visible on satellite maps. The buildings appear distinct from each other. Some small vegetation can be included. The average height of the buildings is below 40m. Dense Urban These are areas within the urban environment with highly concentrated building density. Single features (i.e. buildings, etc.) do not clearly appear distinct from each other e.g. on a satellite map. Heights of the buildings can be well above 40m. Suburban Areas of housing that include some vegetation, mostly found bordering the urban areas, spreading outwards from the city centre. The average height of the buildings is below 15m.

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Road - Quasi Open This clutter type corresponds to regions (rural areas) outside city areas without large development: villages, smaller vegetation, roads. Rural – Open The rural clutter corresponds to areas without buildings, no vegetation and other obstacles. This is modelled explicitly as open area (Please check if applicable or if Road is more suitable for the area described as Rural in the requirements).

2.2 Cell types In 2G networks different site types can be distinguished: macro, micro and pico sites. The division is based on the antenna heights with respect to the surrounding objects (e.g. buildings) and antenna locations. • Macro antennas located above the rooftop level and outdoor • Micro antennas located below roof level and outdoor • Pico antennas located below roof level and indoor A further distinction of Macro sites can be made depending on the antenna type: omni- or directional sectored. The layout of sectored sites is chosen among two-sector, three-sector and six-sector configuration.

2.3 Channel model The channel model is determined by the subscriber behaviour and location. Link budget parameters are impacted by selection of the channel model. The subscriber location is differentiated to indoor/outdoor. Indoor subscribers served by Macro sites receive a signal level which is attenuated by indoor penetration loss. Apart from that also indoor standard deviation has to be calculated. The subscriber perception of propagation phenomena depends on the subscriber velocity and surrounding environment. Thus the following different channel models, taking into account all the factors, are defined: • Static no multipath • TU3 Typical Urban at 3 km/h • TU50 Typical Urban at 50 km/h • RA250 Rural Area at 250 km/h • HT100 Hilly Terrain at 100 km/h Please note that channel model is related to the used band. Doubling of the frequency for the current channel model reduces the subscriber speed to the half, e.g. TU3 for 900/850 MHz is equivalent to TU1.5 for 1800/1900 MHz.

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3 Power Budget parameters The term 'power budget' considers calculation of transmitting and receiving part of the radio link. At the transmitter side, transmitter output power and all the attenuations / gains in the transmitter path produces output power at the antenna output . At the receiver side, minimum sensitivity level and receiving path attenuations / gains produces minimum signal level at the receiving antenna input . Comparison of both results gives 'Maximum Allowable Pathloss' (MAPL) between transmitter and receiver at which the minimum sensitivity is met, i.e. the received signal after path attenuation must exceed the receiver sensitivity, i.e. the lowest possible receive level the receiver can still manage. Separate power budgets for each link direction shall be created – downlink and uplink respectively. The following main factors shall be considered in downlink: • BTS power (BSTX pwr ) • Antenna combiners insertion loss (Lcombiner loss ) • DL cable loss (LDL cable_loss ) • BTS antenna gain (GDL Antenna ) • MS sensitivity (MSRX sensitivity ) • RF cabling loss of the MS (LMS cable loss) • MS antenna gain (GMS antenna) Factors for the uplink, respectively: • MS power (MSTX pwr max) • RF cabling loss of the MS (LMS cable loss) • MS antenna gain (GMS antenna) • BTS sensitivity (BSRX sensitivity) • RX antenna gain of the BTS (GUL antenna) • BTS UL antenna cabling loss (LUL cable loss )

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3.1 BTS transmission power The output power of the BTSplus base station is determined by the output power of the transceiver modules (Carrier Units, CU), the loss of the combining units and the loss of the internal cabling. These power output values are related to the antenna port of the BTSplus base station.

Figure 3-1: TX power reference port

In GMSK, which is a constant envelope modulation type, the amplitude of the GMSK signal is constant over the whole burst. The power amplifier can operate on a non-linear working point with high efficiency. In contrast, the 8-PSK modulation scheme does not have a constant envelope, which implies higher requirement for linearity in the power amplifier. The working point has to be moved to the linear area. Consequently, the maximum transmit power of a typical ECU (i.e. EDGE CU) is reduced when transmitting an 8-PSK signal (i.e. EDGE signal). ECU can of course transmit GMSK modulated signals (i.e. voice or GPRS). An average power capability reduction of 2-3 dB must be considered in comparison to GMSK.

Please note that rule above is related to the maximum output power. If the CU operates below maximum power level (e.g. static power reduction of 2 or 4 dB implemented by a corresponding setting of parameter PWRRED in the TRX object) the ECU power capability reduction for 8-PSK is not relevant.

Maximum output power for GMSK

[dBm]

Maximum output power for 8-PSK

[dBm]

GSM 850 48,3 46,3 GSM 900 48,3 46,3

GSM 1800 48,3 45,3 ECU V3

GSM 1900 48,3 45,3 GSM 850 47 44 GSM 900 47 44

GSM 1800 47 44 FlexCU

GSM 1900 47 44

Table 3-1 Example typical CU output power

Antenna Interface Module

Transceiver Modules

BTS Cabinet Antenna

Reference Port for TX Power

Jumper Cable Feeder

Cable Jumper Cable

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3.2 MS transmission power MS transmission powers are given in the specification [45.005].

GSM 400 & GSM 900 & GSM 850 DCS 1 800 PCS 1 900

Power class Nominal Maximum

output Nominal Maximum

output Nominal Maximum

output 1 - 1 W (30 dBm) 1 W (30 dBm)

2 8 W (39 dBm) 0,25 W (24 dBm) 0,25 W (24 dBm)

3 5 W (37 dBm) 4 W (36 dBm) 2 W (33 dBm)

4 2 W (33 dBm) - -

5 0,8 W (29 dBm) - -

Table 3-2 GMSK MS transmission power For 8-PSK mobiles power reduction due to linearity constraints, as outlined in chapter 3.1, is required. In general power reduction of 2-3 dB is applicable.

3.3 BTS sensitivity Receiver sensitivity is determined by three components:

RX Sensitivity (dBm) = P Noise (dBm) + F BTS (dB) + C/N (dB) Thermal noise: P Noise (dBm) = 10 log (k · T · B) + 30 k Boltzmann constant, 1,38 ·10-23 W·s/oK T Noise temperature, 298 oK = 25 oC B Receiver bandwidth, 190 kHz The value of 30 in the above equation means: unit conversion from dB into dBm (equivalent of multiplication by 1000 in linear measure). P Noise = - 121.07 dBm Noise figure of the BTS at the antenna port: Friis’ formula is utilised for cascaded units: F BTS (dB) = 10 log ( F1 + (F2 - 1) / G1) F1 Noise factor of receiver front end (combiner antenna port) F2 Noise factor of second stage (CU) G1 Power amplification factor of first stage (combiner) (Rx-Gain Combiner (Ant / Rx-Out) - cable loss (DUAMCO/ CU)

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Figure 3-2 Noise figures of cascaded units

Carrier to noise ratio required for performance defined by GSM standard:

[ ] [ ]( )dBPSKTBN

EdBNC

bit

b 81log10/0

+⎟⎟⎠

⎞⎜⎜⎝

⎛⋅

⋅=

Eb Energy of a single data bit No Noise spectral density Eb/No Signal to noise ratio per bit, simulated decoder sensitivity B Bandwidth T bit Duration of the bit time (3,69 µs) 8PSK (dB) Bit rate / Symbol rate (for EDGE-8PSK only) = 3 10 log 3 = 4.77 [dB],

[ ] ( )PSKEDGEdBdBNE

skHzNE

dBNC bb 877,454,169,3190

1log10/00

−++=⎟⎟⎠

⎞⎜⎜⎝

⎛⋅

+=µ

When RX diversity features (chapter 3.5) are applied the sensitivity of the BTS receiving system is improved. This is reflected in sensitivity values of the Carrier Unit. Separate sensitivity values are reported for CUs in case of: • No diversity • 2RX diversity • 4RX diversity

Combiner F1 G1

Carrier Unit F2 G2

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3.3.1 Sensitivity reference ports RX Sensitivity values are referenced to the Antenna Port of the BTS system. For a BTS without TMA the reference port for RX sensitivity data is the antenna connector of the BTS equipment (i.e. Antenna Interface Modules of the BTS - DUAMCO / FDUAMCO in BTSplus).

Figure 3-3 Sensitivity reference port for a BTS without TMA

Sensitivity of BTS without TMA, referred to the antenna, will be decreased by the loss of the feeder cable (and jumper cables). For the systems with TMA the reference port for RX sensitivity is the antenna connector of the TMA.

Figure 3-4: Sensitivity reference port with TMA

Antenna Interface Module

Transceiver Modules

BTS Cabinet

Antenna

Reference Port for Sensitivity

Jumper Cable Feeder

Cable

Jumper Cable

Antenna Interface Module

Transceiver Modules

BTS Cabinet

Antenna

Reference Port for Sensitivity

Jumper Cable

Feeder Cable

Jumper Cable

TMA

Reference Port for TX Power

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3.3.2 TMA and noise figure of the system

As described in previous chapters receiver sensitivity is determined by three components:

RX Sensitivity (dBm) = P Noise (dBm) + F BTS (dB) + C/N (dB) The BTS RX system consists of the number of cascaded devices (e.g. cable, duplexers, combiners etc.). Each device introduces noise caused by signal processing and thermal noise. In such a case system noise figure is calculated using Friis' formula. For a system without TMA:

Figure 3-5 System without TMA

F BTS (dB) = 10 log (F2 + (F3-1) / G2) F2 Noise factor of combiner (linear units) F3 Noise factor of CU (linear units) G2 Power amplification factor of combiner (linear units)

NF w/o TMAdB linear

Combiner gain 22 158,5Combiner NF 1,9 1,5TRX gain 0 1,0TRX NF 12,5 17,8

System NF 2,19 1,7 Table 3-3 Example of system noise figure calculations without TMA

Please note that the sensitivity reference port is placed after a feeder, and feeder losses have to be taken into account during link budget calculations. In order to improve system performance in UL a Tower Mounted Amplifier (TMA) can be used. The purpose of the TMA is to amplify the received signal before it is further attenuated in the antenna feeder.

Feeder F1=3dB G1=-3dB

Combiner F2=1.9 dB G2=22 dB

RX input F3=12.5dB

G3=0dB

Sensitivity Reference point

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For systems with TMA the sensitivity reference port is changed. Thus the formula for calculations of the system noise figure has to be modified accordingly.

Table 3-4 System with TMA

[ ] ⎟⎟⎠

⎞⎜⎜⎝

⎛⋅⋅

−+

⋅−

+−

+=321

4

21

3

1

21

111log10GGG

FGG

FG

FFdBFBTS

F1 Noise factor of TMA (linear units) F2 Noise factor of feeder (linear units) F3 Noise factor of combiner (linear units) F4 Noise factor of CU (linear units) G1 Power amplification factor of TMA (linear units) G2 Losses of feeder (linear units) G3 Power amplification factor of combiner (linear units) G4 Power amplification factor of CU (linear units)

NF with TMAdB linear

TMA gain 25 316,2TMA NF 1,8 1,5Cable loss -3 0,5Cable NF 3 2,0Combiner gain -1 0,8Combiner NF 6,3 4,3TRX gain 0 1,0TRX NF 12,5 17,8

System NF 2,20 1,7 Table 3-5 Example of system noise figure calculations with TMA

Two aspects of the TMA utilisation have to be considered: the sensitivity reference port is moved to the TMA input, and the system noise figure includes the noise figure of the TMA. The former aspect helps to neglect feeder losses in the link budget calculations. The latter impacts the sensitivity, provided that the TMA noise figure is significantly different than that of the Antenna Interface Module (e.g. FDUAMCO) and the resulting system noise figure is different from the one of the no-TMA case.

Sensitivity Reference

TMA F1=1,8dB G1=25 dB

Feeder F2=3dB G2=-3dB

Combiner F3=6.3 dB G3=-1 dB

RX input F4=12.5dB

G4=0dB

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There are two modes of combiner RX path operation: AMCO mode with LNF Amplifier, and MUCO mode (Multi Coupler) without LNF amplifier. Each mode is characterised by different noise figure and attenuation. With the Siemens TMA (high gain), the combiner must be switched to the 'MUCO mode', which implies that the system gain remains unchanged (the TMA gain is equal to that of the LNF amplifier). Please note that the sensitivity is always related to a certain noise figure, which is resulting from all the elements present in the receiving path – Combiner, CU etc. This means that changes of any element / noise figure (e.g. combiner type with different noise figure) impact the sensitivity figures. Always the system noise figure must be taken into consideration.

3.4 MS sensitivity The reference sensitivity performance in terms of frame erasure (FER), bit error (BER), or residual bit error rates (RBER) (whichever is appropriate) is specified according to the type of channel and the propagation conditions. The sensitivity level is defined as the input level for which this performance is met. Sensitivity shall in any case be better than the specified reference sensitivity level (see table below).

Table 3-6: MS reference sensitivity For (E)GPRS, the MS receiver reference sensitivity is defined as the minimum input signal level for which the reference performance in terms of BLER is met.

Reference Performance

Packet Data Channels (PDCH) BLER ≤ 10%

Uplink State Flags (USF) BLER ≤ 1%

Packet Random Access Channels (PRACH) BLER ≤ 15%

Table 3-7 (E)GPRS MS receiver reference performance

BLER is the Block Error Rate, referring to all erroneously decoded data blocks including any headers, stealing flags, parity bits as well as any implicit information in the training sequence.

GSM 900 MS for GSM 900 small MS -102 dBm for other GSM 900 MS -104 dBm

DCS 1 800 MS for DCS 1 800 class 1 or class 2 MS -100 / -

102 dBm for DCS 1 800 class 3 MS -102 dBm

PCS 1 900 MS for PCS 1 900 MS -102 dBm for other PCS 1 900 MS -104 dBm

Reference sensitivity

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For PDCH the BLER refers to RLC blocks, and hence there can be up to two block errors per 20ms radio block for EGPRS MCS7, MCS8 and MCS9. For USF, the BLER only refers to the USF value. Reference sensitivity figures are presented in the respective specifications [45.005]

3.5 Diversity techniques Diversity techniques help to improve the link performance by using uncorrelated copies of the signal. Diversity can be used in both directions: uplink and downlink. RX diversity helps to mitigate fading effects by combining received paths at the receiver. Rx diversity gives benefits for uplink limited scenarios. When the size of site configurations increase, higher combiner losses may lead to downlink limited scenarios. In such cases, an improvement of the downlink part is required. A common method is to replicate downlink paths in order to obtain uncorrelated signal copies at the MS receiver. The problem is to de-correlate signals at the transmitter side in order to avoid interferences there. Two main methods are used: Antenna Hopping and Time delay.

Figure 3-6: TX diversity

Please note that in case the diversity gain is already considered in the BTS receiver sensitivity, there is no need to count it separately in the Link Budget.

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3.5.1 2 branch RX diversity Antenna diversity provides measures to compensate instantaneous fading phenomena of a single Rx-path by a second, equivalent, but non-correlated Rx-path. The efficiency of antenna diversity, i.e. the improvement of the up-link performance, expressed as 'diversity gain', depends on the obtainable grade of de-correlation of both diversity-RX-paths of the up-link. There are two possible solutions of RX diversity: space diversity due to differing Rx positions and polarization diversity due to differing polarization planes. Space diversity requires two V-pol antennas separated by distance D >10λ, where D means the distance between antennas and λ is wavelength for certain frequency.

Figure 3-7: Example 3 sector site layout with space diversity

Polarisation diversity requires dual-polarized antenna with two antenna arrays within the same physical unit. The two antenna arrays are usually oriented in ± 45º polarization planes. The antenna is also referred to as 'X-pol' or 'cross-pol'.

Figure 3-8: 3 Example 3 sector site layout with X-pol antennas

Tx1/Rx1 Rx1 div

Tx2/Rx2 Rx2 div

Tx3/Rx3/ Rx3 div

D Tx1/Rx1

Rx1 div

Tx2/Rx2 Rx2 div

Tx3/Rx3

Rx3 div

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3.5.2 4 branch RX diversity 4-branch RX diversity utilises 4 separate antenna paths. Using a maximum ratio combining of all four receive branches gives an additional diversity gain of up to 2,5 dB, when compared with 2-branch receive diversity. Processing of 4 independent RX paths is performed by means of FlexCU. It requires 2 FlexCU halves working together, so only coverage mode (1 FlexCU acting as 1 TRX) of the unit is possible.

Figure 3-9 FlexCU in 4 RX mode Please note that 4RX requires the double number of antennas and RX paths, however the increased site coverage for uplink limited cases may lead to significant site count reduction. 4RX may be realised on X-pol antennas, however space separation is required between antenna units.

TX-0TX-0

RX-a

RX-b

TX-0

RX-c

RX-d

BasebandSignals

RX-N ... m ain receiverRX-D IV1/D IV3... d iversity receiver

RX-N

RX-D IV1

TX-0

RX-D IV2

RX-D IV3

S ignalProcessing

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Figure 3-10 4RX realization with X-pol antennas

For the most space-critical cases it is possibly to use an 'XX-pol' antenna which holds 2 separate X-pol antennas in one radome. In such a solution sufficient separation between the antenna ports shall be must be ensured by the manufacturer.

3.5.3 TX diversity Antenna Hopping The idea of 'antenna hopping' idea is to transmit each burst on one antenna only, but to change antennas within the interleaving period. This helps to compensate the effects of fast fading, especially in deployments with limited spectrum. This feature can be used in combination with synthesized FH. The gain from antenna hopping can be seen as with frequency diversity where the number of “virtual” hopping frequencies is equal to the number of hopping antennas, multiplied by the number of really hopping frequencies. In particular, the frequency diversity gain would result from an equivalent number of frequencies given by the following relation:

TRX 11 TRX 21

RX 10 20 RX 13 23

TRX 10 TRX 20

Xpol Ant 0

FlexCU-0 FlexCU-1

RX 12 22 RX 14 24

Xpol Ant 1

ACOM ACOM

D

Space

TRX 1 TRX 2

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# Equivalent frequencies = # Frequencies · # Antennas Where: # Antennas stands for the actual number of antennas used for antenna hopping # Frequencies stands for the actual number of frequencies used in the synthesised FH Please note that higher gains of the feature are expected for a limited spectrum. The reason is that the hopping gain tends to saturate for higher number of hopping carriers. Major benefits are expected for static and slow moving MS. The gain depending on terminal velocity is in the range of 0.5 … 2 dB. Voice and circuit switched data benefit well from additional diversity due to their strong forward error correction. High data rate coding schemes of GPRS (e.g. CS4) and EGPRS (e.g. MCS 9) have few forward error correction coding. I.e. these coding schemes perform better without additional diversity. Antenna Hopping is a pure software solution and doesn’t require additional hardware to be added.

3.5.4 TX diversity Time Delay With TX diversity Time Delay the same signals are transmitted simultaneously by two Carrier Units (CU) connected to two different antennas. They operate at the same frequency, one acting as “master” device and the other one as “slave”. Signals are decorrelated by a particular time shift between them. The gain is achieved by the doubled downlink paths and by an increased radiated EIRP output power as seen by receiver.

Figure 3-11: Time shift between signals

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Figure 3-12 No TX diversity (left) and TX diversity Time Delay (right) As can be noticed in the picture above, apart from the double number of TRXs, TX diversity requires the double number of TX paths, which, in some cases, may lead to the necessity to use higher order combiners (e.g. DUAMCO 4:2 instead of DUAMCO 2:2 on Figure 3-12). These solutions, however, increase the losses in the TX path due to higher combiner losses and reduce gains coming from TX diversity. This can be avoided by using double number of combiners and number of antennas (e.g. 2 * DUAMCO 2:2 instead of one DUAMCO 4:2 - Figure 3-13).

Figure 3-13 TX diversity with 4 antennas The solution with 4 antennas requires the double amount of hardware units, however, due to increased cell range in the DL, we can expect significant savings in the number of sites (examples in chapter 8).

CU 3

DUAMCO 2:2

Ant

enna

0

Ant

enna

1

Sect

or 0

TX- 0

TX-1

CU 0 CU 3CU 3

DUAMCO 2:2

Ant

enna

0

Ant

enna

1

Sect

or 0

TX- 0

TX-1

CU 0CU 0 CU 1 CU 3

DUAMCO 4:2

Ant

enna

0

Ant

enna

1

Sect

or 0

Mas

ter

Mas

ter

Sla

ve

Sla

ve

TX-0

TX-2

TX-1

TX-3

CU 0 CU 2CU 1 CU 3

DUAMCO 4:2

Ant

enna

0

Ant

enna

1

Sect

or 0

Mas

ter

Mas

ter

Sla

ve

Sla

ve

TX-0

TX-2

TX-1

TX-3

CU 0 CU 2

CU 1 CU 3

2:2

Ant

enna

0

Ant

enna

2

Sect

or 0

Mas

ter

Mas

ter

Sla

ve

Sla

ve

TX-0

TX-2 - 1 - 3

CU 0 CU 2

2:2

Ant

enna

1

Ant

enna

3

TX TX

CU 1 CU 3

2:2

Ant

enna

0A

nten

na 0

Ant

enna

2

Sect

or 0

Mas

ter

Mas

ter

Sla

ve

Sla

ve

TX-0

TX-2 - 1 - 3

CU 0 CU 2

2:2

Ant

enna

1

Ant

enna

3

TX TX

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Additionally, the advantage of the '4-antenna-solution' is that it can be easily combined with 4RX diversity in order to match the ranges in UL and DL. Example configurations using different TX diversities are presented below.

Table 3-8 Example budget for different TX diversity options

The figures below present the cell area increase when additional gains are achieved due to application of Transmit Diversity.

Figure 3-14 Cell ranges with different diversity options

3.6 RX/TX antenna gain Since usually the same antenna is used for RX and TX, the same antenna gain can be used in downlink/uplink directions. Antenna gains depend on the type and are project specific.

3.7 Combiner insertion losses Antenna combiner insertion losses shall be considered in downlink. They depend on the combiner type. Please note that after the capacity calculation the link budget has to be revised in order to check whether number of TRXs suits assumed combiner order.

No TX diversity TX diversity 2dB DL gainTX diversity 2dB DL

gain + 3dB EIRP

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Figure 3-15: Antenna system elements

Antenna

Jumper connector to antenna

Outdoor jumper cable

Jumper connector to TMA

Tower Mounted Amplifier

Feeder connector to TMA

Feeder cable

Feeder connector to indoor equipment of jumper cable

Jumper connector to BTS

Indoor jumper cable

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4 Propagation related parameters

4.1 Log-normal fading and standard deviation A radio signal is subject of slow fading modelled by a Gaussian distribution. The received signal strength is a random process, and it is only possible to estimate the probability that the received signal strength exceeds a certain threshold. Log-normal fading effect is not considered in standard propagation models, thus the predicted thresholds are with 50 % probability at the cell edge. To consider the probability that more than 50% of the signal strength values are above the threshold, a log-normal fading margin has to be calculated. The standard deviation of the Gaussian distribution must be derived from measurements and depends on the clutter type. Calculations can be performed using Jake’s formulas:

( ) ∫∞

=

⎟⎠⎞

⎜⎝⎛ −

−=≥

0

20

21

0 21

xx

xx

dxexxP σ

πσ ⎟

⎞⎜⎝

⎛ −−=

221

21 0

σxx

erf

where

( )0xxP ≥ Result. loc. prob. at all edge σ Standard deviation x Min. RX input power for 50% loc. prob. x0 Min. RX input power for (x) % loc. prob. The LNF margin is calculated as x * σ, where x is the variable in the cumulative normal function (F(x)) when F(x) has the value of the border percentage given by Jake’s formula. F(x) is usually tabularised.

Location probability at

cell border [%] LNF margin [dB]

50 standard deviation x 0 60 standard deviation x 0.2533471031358 70 standard deviation x 0.524400512708041 75 standard deviation x 0.674489750196082 80 standard deviation x 0.841621233572915 85 standard deviation x 1.03643338949379 90 standard deviation x 1.2815515655446 91 standard deviation x 1.34075503369022 92 standard deviation x 1.40507156030963 93 standard deviation x 1.47579102817917 94 standard deviation x 1.55477359459685 95 standard deviation x 1.64485362695147 96 standard deviation x 1.75068607125217 97 standard deviation x 1.88079360815125 98 standard deviation x 2.05374891063182 99 standard deviation x 2.32634787404084

Table 4-1 LNF margin calculations

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A higher location probability decreases the maximum cell radius. The reason is that, with constant transmitted power and receiver sensitivity, the addition of a fading margin causes the decrease of the cell radius in order to maintain a signal level at the sensitivity threshold.

Figure 4-1: Impact of the location probability on the cell radius

Conversion of the cell edge probability into cell area probability can be obtained by Jake’s formula. It gives a relation for the probability that a certain value P at the cell boundary at radius R is exceeded and the corresponding probability for the whole cell. It is based on the log distance path loss model. The area coverage probability:

( )⎩⎨⎧

⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛ +−⎟

⎠⎞

⎜⎝⎛ +++=

baberf

babaerfFu

1112exp121

2

where

a x x= −⋅

0

( )2

log10 10

⋅=

σen

b

( ) ∫=

−=a

v

v dveaerf0

22π

σ Standard deviation hb Antenna height x Min. RX input power for 50 % loc. prob. x0 Min. RX input power for (x) % loc. prob. n propagation model exponent

R

Location probability 50% LNF margin=0 dB Signal level at the cell edge -102 dBm =-102 dBm - 0dB

Location probability 90 % LNF margin=10.5 dB Signal level at the cell edge -102 dBm =-91.5 dBm - 10.5 dB

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erf error function

4.2 Indoor case A Mobile radio signal from the macro station inside the building is attenuated by building structures. The difference between an outdoor and indoor signal level is characterised by the penetration losses. They can be seen as the difference between the average signal strength in the free space next to the building and the average signal strength over the ground floor of the building. The building penetration loss for different buildings is log-normal, distributed with a standard deviation (σ LNF(i) ). Apart from the fluctuation coming from log-normally distributed penetration losses, the indoor signal is subject to outdoor log-normal fading. In order to take into account both effects, a joint standard deviation has to be calculated. The following formula covers both deviations:

2(i)LNF

2(o)LNF i)LNF(o σσσ +=+

Where:

)( ioLNF +σ Standard deviation for both indoor and outdoor

)(oLNFσ Outdoor standard deviation

)(iLNFσ Indoor standard deviation Penetration losses depend on many factors as building materials, structure and environment. Similar to building penetration loss is in-car penetration loss. The margin is added to compensate signal decrease when MS is located inside the car.

4.3 Interference degradation margin Receiver sensitivity estimation is based on a noise-limited scenario where the required carrier to noise ratio (C/N) is taken into account. Interference is not an issue. In interference limited cases C/N is degraded to C/(N+I). In order to take additional interference into account, the required signal level must be increased to combat both noise and interference. Thus, an interference margin is defined for interference limited systems. It can , however, be assumed that the cell coverage is dimensioned in such a way that constant BCCH coverage is assured, which is typically a noise limited scenario. In such a case the noise typically overrides interference and the interference margin can be neglected.

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In case of interference limited scenarios, the cell range is typically limited by the capacity of the network resulting in a cell size which is usually much lower than the one that comes from pure link budget calculations.

4.4 Body loss The proximity of the human body during the call affects the MS performance. There are well known effects, such as absorption of energy by the human head, and deterioration of the antenna efficiency. In order to consider such phenomena, a body loss margin was introduced. The body loss is smaller for higher frequencies than for lower ones. The body loss recommended by ETSI is 3 dB. For handheld data terminals a body loss of 0 dB is assumed.

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5 Maximum Allowable Pathloss calculation

5.1 Equivalent Isotropic Radiated Power EIRP EIRP stands for the power radiated by an isotropic antenna. The radiated power transmitted by a directional antenna is transposed into the power radiated by an isotropic antenna by consideration of the antenna gain and the power at the antenna input. Comparison to the dipole antenna gives ERP; the difference between EIRP and ERP is 2.15 dB. The power at the antenna input considers all the losses: static power reduction, connectors and feeder loses. EIRPBTS = BSTX pwr_max - Lbackoff - LDL cable_loss - Lcombiner loss + GDL Antenna EIRPMS = MSTX pwr_max - LMS cable_loss + GMS Antenna Where Lbackoff static power reduction (corresponds to parameter PWRRED in TRX object) Lcombiner loss antenna combiners insertion loss LDL cable_loss DL cable loss LMS cable loss RF cabling loss of the MS GDL Antenna BTS TX antenna gain GMS antenna MS antenna gain BSTX pwr_max peak RF power at the CU MSTX pwr max peak RF power of the MS

5.2 Power budget calculations The purpose of the power budget calculations is to determine the maximum allowable path loss over the air interface between the antennas of BTS and MS. The maximum Allowable Pathloss (MAPL) is calculated according to the formula: Downlink: MAPLDL = BSTX pwr_max – MSRXsensitivity – LossDL – Margins DL + GainsDL

Where BSTX pwr_max peak RF power at CU MSRX sensitivity MS sensitivity LossDL losses of the system MarginsDL margins coming from the propagation phenomena GainsDL system gains

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Margins: Margins= Linterference deg margin + Llog-normal margin

Linterference deg margin interference degradation margin Llog-normal margin Log-normal fading margin Loss: Loss= Lbackoff + Lcombiner loss + LDL cable_loss + Lbody_Loss_for _handhelds + LMS cable loss Lbackoff static power reduction Lcombiner loss antenna combiners insertion loss LDL cable_loss DL cable loss LMS cable loss RF cabling loss of the MS Lbody loss body loss Lpenetration penetration losses Lincar incar losses Lpenetration and Lincar losses should be also used in above equation if applicable. Gains: Gains= GDL Antenna + GMS antenna + GDL TX div GDL Antenna BTS TX antenna gain GMS antenna MS antenna gain GDL TX div downlink diversity gain Uplink: MAPLUL = MSTX pwr max - BS RXsensitivity - LossUL + GainUL - MarginUL Where MSTX pwr max peak RF power of the MS BSRX sensitivity BTS sensitivity LossUL losses of the system MarginsUL margins coming from the propagation phenomena GainsUL system gains Margins: Margins= Linterference deg margin + Llog-normal margin

Linterference deg margin interference degradation margin Llog-normal margin Log-normal fading margin

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Loss: Loss= Lbody_Loss_for _handhelds + LMS cable loss + LUL cable loss If HPDU is used additional LHPDU loss shall be taken into account. In case a TMA is used LUL cable loss shall be omitted. Lbody loss body loss LMS cable loss RF cabling loss of the MS LHPDU HPDU loss LUL cable loss BTS UL antenna cabling loss Gains: Gains= GUL Antenna + GMS antenna + GUL diversity GMS antenna MS antenna gain GUL antenna UL antenna (RX antenna) gain of the BTS GUL diversity UL diversity gain Power budget elements are roughly presented in the picture below, together with the signal variations.

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Figure 5-1 Power budget elements Bars in the picture above represents signal variations starting from the transmitter output, TX path gains and losses, pathloss of the propagation path and corresponding receiving path items. In the following table example Link Budget calculations for UL and DL are provided:

Max TX output power minus TX Loss

Signal level (dBm)

Max TX output power

Max allowable Pathloss

RX sensitivity

RX Loss

Interference degradation margin

Min SNR requirement

Noise figure

RX system Noise power

Thermal noise power

Max TX output power minus TX Loss plus TX gains

RX power

RX power plus RX Gains RX

power plus RX Gainsminus RXLoss

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MS dataMax. output-power of MS dBm 33,0 MSTX pwr max

MS sensitivity dBm -105 MSRX sensitivity

MS cable loss dB 0 LMS cable loss

MS antenna gain dBi 0 GMS antenna

EIRP MS dBm -105 EIRPMS = MSTX pwr_max - LMS cable_loss + GMS Antenna

BTS dataBS Peak Power at PA output dBm 47,0 BSTX pwr_max

Backoff dB 0,0 Lbackoff

Combiner loss dB 4,30 Lcombiner loss

DL-Cable Loss dB 1,0 LDL cable_loss

DL-Antenna Gain dBi 18,5 GDL Antenna

Receiver Sensitivity dBm -114,0 BSRX sensitivity

UL-Cable Loss dB 1,0 LUL cable loss

UL-Antenna Gain dBi 18,5 GUL antenna

Diversity Gain in Uplink dB 5,0 GUL diversity

Diversity Gain in Downlink dB 5,0 GDL TX div

EIRP BTS dBm 60,19 EIRPBTS = BSTX pwr_max - Lbackoff - LDL cable_loss - Lcombiner loss + GDL Antenna

Planning data urbanStandard deviation (outdoor) dB 7,0 σoutdoor

Standard deviation (indoor) dB 9,0 σindoor

Joint standard deviation dB 11,4 σi = sqrt(σoutdoor + σindoor)Loc. prob. at edge % 90 Probedge

Loc. prob. at cell area % 96 Probarea

Log-normal fading margin (indoor) dB 14,6 Llog-normal margin i = f (Probedge, σi )Log-normal fading margin (outdoor dB 9,0 Llog-normal margin o = f (Probedge, σi )Body loss for handhelds dB 3 Lbody loss

Incar loss dB 6 Lincar

Indoor penetration loss dB 15,0 Lpenetration

Interference degradation margin dB 3,0 Linterference deg margin

Max. DL PL outdoor (50 %) dB 164,2

MAPLDL50 = BSTX pwr_max – MSRXsensitivity – LossDL – Linterference deg margin + GainsDL

LossDL = Lbackoff + Lcombiner loss + LDL cable_loss + Lbody_Loss_for _handhelds + LMS cable loss

GainsDL = GDL Antenna + GMS antenna + GDL TX div

Max. UL PL outdoor (50%) dB 163,5

MAPLUL50 = MSTX pwr max - BS RXsensitivity - LossUL + GainUL - Linterference deg margin

Loss= Lbody_Loss_for _handhelds + LMS cable loss + LUL cable loss

Gains= GUL Antenna + GMS antenna + GUL diversity

Max. DL PL outdoor dB 155,2 MAPLDL o = MAPLDL50 - Llog-normal margin o

Max. UL PL outdoor dB 154,5 MAPLUL o = MAPLUL50 - Llog-normal margin o

Max. DL PL indoor dB 134,6 MAPLDL i = MAPLDL50 - Llog-normal margin i - Lpenetration

Max. UL PL indoor dB 133,9 MAPLUL i = MAPLUL50 - Llog-normal margin i - Lpenetration

Max. DL PL incar dB 149,2 MAPLDL incar = MAPLDL50 - Llog-normal margin o - Lincar

Max. UL PL incar dB 148,5 MAPLUL incar = MAPLUL50 - Llog-normal margin o - Lincar

Figure 5-2: Example general link budget

5.3 (E)GPRS link budget With (E)GPRS, the coverage planning becomes more complicated because the reference sensitivity levels of MS and BTS vary with CS’s / MCS’s. It means that in the (E)GPRS coverage planning process it is necessary to check in which area of the radio cell the signal strength is high enough to support a particular coding or modulation and coding scheme. In this way it is possible to determine in which area

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of the cell which the maximum data rate can be offered. This approach refers to a noise limited scenario where interference is not an issue. Below the GPRS link budget for TU50FH is presented. Link budget assumptions (examples): Band 900 MHz Channel model TU50FH outdoor standard deviation бLNF(o) = 8 dB cell area probability 95% cell edge probability 86% Log-normal fading margin 8,7 dB Uplink Voice CS1 CS2 CS3 CS4

Transmitter (MS)MS Output Power [dBm] 33,0 33,0 33,0 33,0 33,0Ms Antenna Gain [dBi] 0,0 0,0 0,0 0,0 0,0Body Loss [dB] -3,0 -3,0 -3,0 -3,0 -3,0EIRP [dBm] 30,0 30,0 30,0 30,0 30,0Receiver (BTS)BTS Receiver Sensitivity [dBm] -116,2 -116,2 -113,7 -112,2 -107,0BTS Antenna Gain [dBi] 18,0 18,0 18,0 18,0 18,0Diversity gain [dB]* 0,0 0,0 0,0 0,0 0,0Cable loss [dB] -3,0 -3,0 -3,0 -3,0 -3,0Indoor loss [dB] -15,0 -15,0 -15,0 -15,0 -15,0Interference degradation margin [dB] -2,0 -2,0 -2,0 -2,0 -2,0Log-normal fading margin [dB] -8,7 -8,7 -8,7 -8,7 -8,7

Allowed Uplink Path Loss [dB] 135,5 135,5 133,0 131,5 126,3* Diversity Gain included in sensitivity

Downlink Voice CS1 CS2 CS3 CS4

Transmitter (BTS)BTS Output Power [ECU V3] [dBm] 48,3 48,3 48,3 48,3 48,3BTS Antenna Gain [dBi] 18,0 18,0 18,0 18,0 18,0Combiner loss (DUAMCO 4:2) [dB] -4,3 -4,3 -4,3 -4,3 -4,3Cable loss [dB] -3,0 -3,0 -3,0 -3,0 -3,0EIRP [dBm] 59,0 59,0 59,0 59,0 59,0Receiver (MS)MS Receiver Sensitivity [dBm] -104,0 -102,0 -99,0 -97,0 -88,0MS Antenna Gain [dBi] 0,0 0,0 0,0 0,0 0,0Diversity gain [dB] 0,0 0,0 0,0 0,0 0,0Indoor loss [dB] -15,0 -15,0 -15,0 -15,0 -15,0Body loss [dB] -3,0 -3,0 -3,0 -3,0 -3,0Interference degradation margin [dB] -2,0 -2,0 -2,0 -2,0 -2,0Log-normal fading margin [dB] -8,7 -8,7 -8,7 -8,7 -8,7

Allowed Downlink Path Loss [dB] 134,3 132,3 129,3 127,3 118,3* Diversity Gain included in sensitivity

Table 5-1 Link Budget calculation for GPRS For the EGPRS case the difference is that for 8-PSK MCS’s the maximum CU transmit power is decreased. Link budget assumptions (examples):

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Band 900 MHz Channel model TU50 outdoor standard deviation бLNF(o) = 7 dB cell area probability 95% cell edge probability 85% Log-normal fading margin 7,3 dB

Uplink Voice MCS1 MCS2 MCS3 MCS4 MCS5 MCS6 MCS7 MCS8 MCS9Transmitter (MS)

MS Output Power dBm 33,0 33,0 33,0 33,0 33,0 33,0 33,0 33,0 33,0 33,08-PSK power decrease dB 0,0 0,0 0,0 0,0 0,0 -3,0 -3,0 -3,0 -3,0 -3,0MS Antenna Gain dBi 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0Body Loss dB -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0EIRP dBm 30,0 30,0 30,0 30,0 30,0 27,0 27,0 27,0 27,0 27,0Receiver (BTS)

BTS Receiver Sensitivity (2RX div) dBm -116,1 -115,4 -113,9 -110,6 -107,3 -108,9 -107,0 -103,3 -99,4 -97,9BTS Antenna Gain dBi 18,0 18,0 18,0 18,0 18,0 18,0 18,0 18,0 18,0 18,0Diversity gain* dB 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0Cable loss dB -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0Indoor loss dB 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0Interference degradation margin dB -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0Log-normal fading margin dB -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3

Allowed Uplink Path Loss dB 151,8 151,1 149,6 146,3 143,0 141,6 139,7 136,0 132,1 130,6* Diversity Gain included in sensitivity

Downlink Voice MCS1 MCS2 MCS3 MCS4 MCS5 MCS6 MCS7 MCS8 MCS9Transmitter (BTS)

BTS Output Power [ECU V3] dBm 48,3 48,3 48,3 48,3 48,3 46,3 46,3 46,3 46,3 46,3BTS Antenna Gain dBi 18,0 18,0 18,0 18,0 18,0 18,0 18,0 18,0 18,0 18,0Combiner loss (DUAMCO 4:2) dB -4,3 -4,3 -4,3 -4,3 -4,3 -4,3 -4,3 -4,3 -4,3 -4,3Cable loss dB -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0EIRP dBm 59,0 59,0 59,0 59,0 59,0 57,0 57,0 57,0 57,0 57,0Receiver (MS)

MS Receiver Sensitivity dBm -104,0 -100,5 -98,5 -94,5 -89,0 -93,0 -91,0 -84,0 -83,0 -78,5MS Antenna Gain dBi 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0Diversity gain dB 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0Indoor loss dB 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0 0,0Body loss dB -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0 -3,0Interference degradation margin dB -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0 -2,0Log-normal fading margin dB -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3

Allowed Downlink Path Loss dB 150,7 147,2 145,2 141,2 135,7 137,7 135,7 128,7 127,7 123,2* Diversity Gain included in sensitivity

EGPRS Link Budget

Frequency 900 Mhz, TU50, outdoor

Table 5-2 Example Link Budget calculation for EGPRS

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5.4 Power budget balance The maximum range of a two-way radio communication system is restricted by the weakest transmission direction. Difference in coverage for uplink and downlink direction gives any benefit since additional transmit power does not mean any improvements in the coverage area but generates additional interference and costs. A balance of uplink and downlink is required to assure that cell ranges in DL and UL are the same. In other words, the sensitivity limit of the MS is reached at the same point as the sensitivity limit of the BTS. Since the antenna gain is symmetrical, the balance is independent of the BTS antenna. Please note that link budget parameters (e.g. penetration losses, log-normal fading) are clutter specific, hence balancing is related to the specific environment and MS class. Moreover it also depends on the service, so even if for voice service the link budget is balanced, for (E)GPRS the system becomes unbalanced. The following actions are possible for an uplink limited scenario: • static decrease of the BTS power (by a corresponding PWRRED parameter

setting) • RX diversity improvements on the BTS side (2RX as standard, improved to 4RX

diversity) • TMA employments • IURS feature activation Downlink limited: • TX diversity at the BTS side • Combiners of lower attenuation

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6 Radio propagation prediction A propagation model gives relations between the path loss L and distance r between the base station antenna and the mobile, the frequency f, the heights of the base station antenna and MS antenna and the clutter type.

6.1 Propagation slope The 'free space propagation model' [6] is used to predict the signal strength when a LOS (Line Of Sight) is between transmitter and receiver. This scenario is rather rarely applicable for a real mobile radio environment. However, the free space propagation model shall be treated as a first step of expected signal strength evaluation.

LrGGP

rP rttr 22

2

4 )()(

πλ

=

Where: Pr power at the receiver antenna Pt transmitter power Gt transmitter antenna gain Gr antenna gain λ wavelength r distance between transmitter and receiver L system loss factor (e.g. cable and combiner loss) The equation above shows that the received power falls off as the square of the transmitter-receiver separation distance. Expressed in terms of dB this means that the received power decays with distance at a rate of 20 dB/decade. This power decay is represented by the path loss, which is a positive quantity of signal attenuation. The path loss in the free space propagation model is represented by:

( ) ⎟⎟⎠

⎞⎜⎜⎝

⎛−=⎟⎟

⎞⎜⎜⎝

⎛=

22

2

41010

rPP

dBPLr

t

πλloglog][

The free space propagation model is insufficient for a real mobile radio environment, where is no LOS. The Log-distance Path Loss Model takes into account different propagation environments by using a specific path loss exponent (propagation slope) for a particular type of propagation environment. The propagation slope γ is determined by field measurements. The equation below describes the power decay in dependency of γ.

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γ

⎟⎠

⎞⎜⎝

⎛=rr

rPrP rr0

0 )()(

Pr(r0) reception power level in a close-in reference distance r0 which ensures far

field conditions. Pr(r0) can be obtained by measurements or by prediction of the free space propagation model. The resulting path loss is given by

⎟⎟⎠

⎞⎜⎜⎝

⎛+=

00 10

rrrPLdBPL log)(][ γ

The table below shows propagation slopes for different propagation environments:

Propagation environment Path loss exponent

free space 2urban area 2,7 to 3,5 (3,5)shadowed urban 3 to 5 (3,8)in building LOS 1,6 to 1,8 in building obstructed 4 to 6

Table 6-1: Propagation slopes

6.2 One slope model The Okumura and Hata formula is based on empirical data measured by Okumura in 60’s. Hata developed a formula with correction terms for different environments. The model assumes a quasi flat surface i.e. obstacles like buildings are not explicitly taken into account. Different types of surfaces are distinguished by different correction factors. The model is best applicable for cell ranges of 5 ...20 km. Below a range of 1 km it becomes very rough and unreliable, due to fact that obstacles in the close vicinity of receiver and transmitter are not taken into account in the formula. Okumura Hata model Where: L pathloss f frequency: hBS height of base station hMS height of MS

)log()]log(55.69.44[)()log(82.13)log(16.2655.69 dhchdhfL BSMSBS −+−−−+=

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d distance c clutter correction factor d(hMS) MS antenna height correction du dense urban u urban su suburban Clutter correction factors: This model is applicable in the following range of parameters: Frequency: f = 150 .. 1500 MHz Height of base station: hBS = 30.. 200 m Height of MS: hMS = 1.. 10 m Distance: d = 1.. 20 km COST 231 – Hata model Due to fact that Okumura Hata model is not applicable for frequencies >1500 MHz extended version of Hata model has been developed for the frequency range 1500 - 2000 MHz. Where: L pathloss f frequency hBS height of base station hMS height of MS d distance c clutter correction factor

⎩⎨⎧

−−−−

=sufhf

uduhhd

MS

MSMS ]8.0)log(56.1[]7.0)log(1.1[

,97.4)]75.11[log(2.3)(

2

( )[ ] ( )( )[ ] ( )

⎪⎪⎪⎪

⎪⎪⎪⎪

+−

+−

+⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛⋅

=

quasiff

openff

suburbanfforest

udu

c

94.35log33.18log78.4

94.40log33.18log78.4

4.528

log2

10,0

2

2

2

)log()]log(55.69.44[)()log(82.13)log(9.333.46 dhchdhfL BSMSBS −+−−−+=

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d(hMS) MS antenna height correction The MS antenna height correction formula remains the same as in the previous case. Clutter correction factors: This model is applicable in the following range of parameters: Frequency: f = 1500 .. 2000 MHz Height of base station: hBS = 30.. 200 m Height of MS: hMS = 1.. 10 m Distance: d = 1.. 20 km

6.3 Two slope model To improve the unreliability of a 1-slope model in the closer distances, a 2-slope model was introduced, which has different characteristics in the area close to the transmitter. Usually the transition point is set at distance of 1 km. HATA – COST 231 – HATA two slope model If the equations predict a radio range smaller than 1 km, a transition model is applied. Where: A1/2 frequency dependent part: si distance dependent part:

[ ][ ]⎪

⎪⎪⎪⎪

⎪⎪⎪⎪⎪

+−

+−

+⎥⎦

⎤⎢⎣

⎡⎟⎠⎞

⎜⎝⎛

=

quasiff

openff

suf

forestudu

c

94.35log33.18log78.4

94.40log33.18log78.4

4.528

log2

100

3

2

2

2

)log()(2/1 dschdAL iMS ⋅+−−=

MHzfhfA BS 1500)log(82.13)log(16.2655.691 ≤−+=

MHzfhfA BS 1500)log(82.13)log(9.333.462 >−+=

kmddhs BS 1)log()]log(55.69.44[1 ≥−=

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6.4 Cell Size evaluation The output from the power budget calculations is the Maximum Allowable Pathloss (MAPL). Comparison of the MAPL to the pathloss calculated by assumed propagation model gives the maximum cell size. For instance, for the Okumura-Hata (f<1500MHz) 1 slope model the propagation loss at distance d is: As for maximum cell size L=MAPL we can deduct the maximum cell range: d=10α

where BS

MSBS

hchdhfMAPL

log..))(log.log..(

556944821316265569

−−−−+−

For frequency >1500MHz, the modified Hata formula is used and thus the maximum cell range is:

BS

MSBS

hchdhfMAPL

log..))(log.log..(

5569448213933346

−−−−+−

Please note that the cell size depends on the clutter characteristics and expected coverage targets (indoor, outdoor etc.). For the 2 slope model, if the cell ranges are higher than the intercept point (e.g. 1 km), the formulas as above can be applied, however, if the distance is less than the intercept point, the modified formula shall be used. In the table below the cell ranges for EGPRS are calculated. The 2 slope model is used with the intercept point at 1 km, urban outdoor coverage.

( ) ( )( )( ) kmdfAs 150log

102.0log20log204.322/12 <⋅++−=

)log()]log(55.69.44[)()log(82.13)log(16.2655.69 dhchdhfL BSMSBS −+−−−+=

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MCS Max allowed UL pathloss [dB]

UL coverage radius [km]

Max allowed DL pathloss [dB]

DL coverage radius [km]

MCS1 160,40 5,74 156,70 4,50MCS2 158,90 5,20 154,70 3,95MCS3 155,60 4,19 150,70 3,04MCS4 152,30 3,38 145,20 2,12MCS5 150,90 3,08 147,20 2,42MCS6 149,00 2,72 145,20 2,12MCS7 145,30 2,14 138,20 1,34MCS8 141,40 1,66 137,20 1,26MCS9 139,90 1,50 132,70 0,95

Table 6-2 EGPRS cell ranges in dependency on MCS The balancing of the system is strictly related to the service. Even if for one service the system is well balanced (e.g. voice) it remains unbalanced for data services. The difference in the uplink/downlink coverage radius depends mainly on the difference between the receiver sensitivity values of the MS and the receiver sensitivity values of the BTS. The cell radius decreases with the MCS index for UL. For DL the same tendency can be observed; however, due to better sensitivity of 8PSK MCSs, the cell range is slightly increased for MCS5-9. But in general high data rates are available only close to base station (e.g. based on calculations, MCS9 can only be used in areas whose distance to the base station does not exceed 1030 m. According to the link budget it can be defined at which distance from the BTS which modulation and coding scheme is supported. In the table below the minimum signal level assuring the availability of the individual coding scheme has been calculated. The received signal thresholds for outdoor environment listed in the table are calculated from the assumed values for MS receiver sensitivity, log-normal fading and body loss. Indoor environment requires penetration loss and indoor standard deviation to be taken for calculations. Please also note that body loss shall be considered only for handheld terminals (not for data terminals). The calculated thresholds define the minimum level at certain pixel of the coverage plot that has to be provided to meet the requirements for the corresponding MCS. Frequency 900 Mhz - Urban Areas - TU50 Voice MCS1 MCS2 MCS3 MCS4 MCS5 MCS6 MCS7 MCS8 MCS9

MS Receiver Sensitivity [dBm] -104,0 -100,5 -98,5 -94,5 -89,0 -93,0 -91,0 -84,0 -83,0 -78,5Indoor loss [dB] 0 0 0 0 0 0 0 0 0 0Body loss [dB] -3 -3 -3 -3 -3 -3 -3 -3 -3 -3Log-normal fading margin [dB] -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3 -7,3Threshold [dB] -93,7 -90,2 -88,2 -84,2 -78,7 -82,7 -80,7 -73,7 -72,7 -68,2

Table 6-3 MCS thresholds

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In the picture below visualisation of different MCSs ranges is depicted. Please note that, as far as noise-limited scenario has been considered, the utilization of given MCS is determined only by the signal level. It should be kept in mind that the reachable throughput for GPRS and EGPRS data depends also on the interference situation. Thus for a precise network planning it is necessary to consider both restrictions: min signal level and interference situation.

Figure 6-1 EGPRS MCS ranges

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7 Grid planning Based on the determined cell range, the corresponding cell area and site-to-site distance can be calculated. Calculations depend on the selected cell layout. A traditional hexagonal cell model is mainly used. Further steps depend also on sectorisation.

Sector cells generally improve the coverage since in this case higher antenna gains are used which are achieved due to the directional diagram of the antenna. In this case the antenna characteristic shall be adjusted to the cell pattern, which is going to be applied to the area to be covered. Sectorisation additionally helps to cope with interferences since the number of interfering signals per cell is theoretically reduced. The overall C/I distribution is improved, what resulting in a lower clutter size and a higher frequency reuse and, consequently, in a higher total capacity of the network. In fact, many factors have to be considered when deciding about the cell pattern: • Traffic density in the area to be covered In this case coverage or capacity is the

limiting factor during grid planning • Available frequency band frequency reuse to be achieved with assumed cell

layout • Required coverage and structure of the area to be covered: urban area, road, etc. • Costs and possibilities of the site installation • Expected network development path The number of sites N required to cover certain area P is as follows:

siteAPN =

Where Asite is area covered by one site.

7.1 Omni cell Omni-cells may be chosen in low traffic areas with good radio propagation (open area), especially dedicated for isolated sites. The antenna gain must correspond to an omni-directional antenna. The rhomboidal cell layout has to be applied for omni scenario in order to calculate the required site-to-site distance.

Figure 7-1 Cell shape for omni cell

R

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Respective site to site distance:

Figure 7-2 Site to site distance for omni cell

And cell area:

233 2RAcell

*=

7.2 3-sectors site In case of commonly used 3-sectorized sites, a different cell layout can be built depending on the assumed geometrical representation of each cell of the site: hexagon or rhomboid.

Figure 7-3: Cell shape of 3-sectorized site

Depending on the assumed cell model, a different site-to-site distance has to be calculated when planning the homogenous network layout.

Cell range R

Site-to-site Distance D = 1,732 * R

Rhomboidal cells Hexagonal cells

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Figure 7-4: Cell range and site-to-site distance for hexagonal cell

Figure 7-5: Cell range and site-to-site distance for rhomboidal cell

The site coverage can be calculated as follows: Hexagonal cell shape:

2

833 )(** RAcell =

cellsite AA *3=

where R is the cell range. Rhomboidal cell shape:

23 2

max* RAcell =

cellsite AA *3=

7.3 6- sector sites

Site-to-site distance of hexagonal sites D = 1.5 * R

Cell range R

Site-to-site Distance D = 1,732 * R

Cell range R

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The network layout containing 6-sectors site can be modelled in the same way as it is for 3-sector rhomboidal cells. Higher sectorisation allows the usage of higher antenna gains than for 3-sector rhomboidal cells.

Figure 7-6 6 sector cell layout

Figure 7-7 Cell range and site-to-site distance for 6 sector site Cell area:

23 2

max* RAcell =

cellsite AA *6= The cell range is estimated from the link budget parameters and the propagation model. With the same parameters and cell ranges, a 6 sectors site provides significantly higher coverage area compared to the standard 3 sector cloverleaf structure.

Site-to-site Distance D = 1,732 * R

Cell range R

R

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Figure 7-8 3 sector and 6 sectors cell layout comparison

Thus, 6-sector stands for a solution where relatively high coverage per site can be achieved.

7.4 2- or 1-sector sites (road site) Sites along roads can be specified as two- or one-sector sites. In the latter case the cell illumination will be obtained by a combination of two splitters connected to directional antennas. The subsequent reduction (about 3dB) of the resulting overall antenna gain must be taken into account.

Figure 7-9 2 sector road site Site area:

9,2 km

R*1.5 = 13.8 km

R*1.732 = 16 km

1.33/SSCov_gain 36 ==6*2

R*3S2

6 =3*8

R*3*3S

2

3 = 34

RR

SS

23

26

3

6 ⋅=

R

9,2 km

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323 2R

Acell *=

cellsite AA *2= where R is the cell range.

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8 Link budget application cases As outlined in the previous chapters, various link budget enhancements can be used in order to increase the cell range or to balance the link. Gains expected from the features are summarized in the table below.

Table 8-1 Coverage enhancements features

Respective gains can be entered to the appropriate cells of the budgetary calculation tools.

Figure 8-1 Relation of sensitivity and RX diversity

If the RX diversity is already considered in sensitivity figures, there is no need to consider the diversity gain separately. Gains of TX diversity features can be entered to the appropriate cells.

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Figure 8-2 TX diversity gain The impact of the coverage enhancement features was evaluated for scenarios with different feature set activated. General settings: • Urban + outdoor environment • Frequency band: 1800 MHz • Network layout: 3-sectorized clover leaf • HW configurations: BS 240 w/ 4/4/4, FlexCU / FDUAMCO With basic configuration (no coverage enhancements) we can obtain the following results:

Table 8-2 Basic configuration results

The basic scenario is uplink limited: i.e. the path loss difference calculated by MPL DL - MPL UL[dB] establishes a positive result clearly above 0. Thus, in order to enhance the cell range in uplink UL diversity feature shall be used. At first let us utilize 2 RX diversity.

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Table 8-3 2RX diversity configuration Result: the cell's UL range is increased, but we are still UL limited (MPL DL - MPL UL[dB] >> 0 ). The solution is to use TMA.

Table 8-4 Configuration with TMA

Now the link is well balanced (MPL DL - MPL UL[dB] ≈ 0 ), further DL cell range improvements may utilize TX diversity antenna hoping (AH). As this is a pure software feature, no additional hardware changes are required.

Table 8-5 Configuration with Antenna Hopping

There is no big difference in the performance – the reason is that after AH was switched on the cell configuration is now uplink limited and the full advantage of the increased DL range can not be exploited. The solution is to improve UL coverage. As we already utilized 2RX and TMA the only next step is 4RX diversity. This requires additional antennas to be installed and the RX path to be reconfigured. Please note that such a solution is feasible only for FlexCU.

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Table 8-6 Configuration with Antenna Hopping and 4RX diversity

The scenario is now again DL limited (MPL DL - MPL UL[dB] << 0 ), and the AH gain produces an additional increase of cell range. However, please note that we are still able to improve our DL coverage by the TX diversity Time Delay feature. In order to use the feature we have to use the double number of CUs.

Table 8-7 Configuration with TX diversity Time Delay and 4RX diversity

Please note that advanced configurations require additional hardware: CU, combiners, antennas etc. which significantly increases site cost. Nevertheless, such a configuration provides big coverage and the number of sites can be substantially reduced. For each case the cost calculations have to be performed. The cell ranges increase and site count reduction is visualized in the picture below.

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Figure 8-3 UL/DL Cell ranges and site counts

basic scenario (no RX, TX boosts)

UL (2 RX) ; DL (no TX boost)

UL (2 RX+ TMA) ; DL (no TX boost)

UL (2 RX+ TMA) ; DL (Ant.

UL (4 RX+ TMA) ; DL (Ant. Hop.)

UL (4 RX+ TMA) ; DL (Time

2.31

2.76

3.15

3.15

3.56

3.73

3.13

3.13

3.13

3.56

3.73

4.48

79

55 sites / 30 % site

43 / 45 %

43 / 45 %

33 / 58 %

31 / 61 %

1

2

3

4

5

6

Downlink Uplink Cell