bsspar chapter 09 coverage enhancement features mo

8/14/2019 BSSPAR Chapter 09 Coverage Enhancement Features MO

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Nokia Networks Oy 1 (8)

COVERAGE ENHANCEMENTFEATURES


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Coverage Enhancement Features

2 (8) Nokia Networks Oy

The information in this document is subject to change without notice and describes only theproduct defined in the introduction of this documentation. This document is intended for theuse of Nokia Networks' customers only for the purposes of the agreement under which thedocument is submitted, and no part of i t may be reproduced or transmitted in any form ormeans without the prior written permission of Nokia Networks. The document has beenprepared to be used by professional and properly trained personnel, and the customerassumes full responsibility when using i t. Nokia Networks welcomes customer comments aspart of the process of continuous development and improvement of the documentation.

The information or statements given in this document concerning the suitability, capacity, orperformance of the mentioned hardware or software products cannot be considered bindingbut shall be defined in the agreement made between Nokia Networks and the customer.However, Nokia Networks has made all reasonable efforts to ensure that the instructionscontained in the document are adequate and free of material errors and omissions. NokiaNetworks will, if necessary, explain issues which may not be covered by the document.

Nokia Networks' liability for any errors in the document is limited to the documentarycorrection of errors. Nokia Networks WILL NOT BE RESPONSIBLE IN ANY EVENT FORERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL ORCONSEQUENTIAL (INCLUDING MONETARY LOSSES), that might arise from the use of thisdocument or the information in it.

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Other product names mentioned in this document may be trademarks of their respectivecompanies, and they are mentioned for identification purposes only.

Copyright Nokia Networks Oy 2004. All rights reserved.


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Contents

9 Coverage Enhancement Features 49.1 Module Objectives 49.2 Intelligent Coverage Enhancement 49.2.1 Idea 49.2.2 Handover between Low / High Power TRX 59.3 Inverse Intelligent Coverage Enhancement 69.3.1 Idea 69.3.2 Handover for Inverse ICE 8


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9 Coverage Enhancement Features

9.1 Module Objectives

At the end of the module the participant will be able to:

Explain the motivation for ICE

Discuss the handover mechanism between high and low powerTRXs

Demonstrate the difference between ICE and inverse ICE

Discuss the handover mechanism between hopping and nonhopping TRXs

9.2 Intelligent Coverage Enhancement

9.2.1 Idea

The basic idea of this feature is to realise the coverage and capacitylayer with TRXs of different power. Each cell has at least one BCCHTRX transmitting with high power for coverage, and one TRX

transmitting with lower power for capacity. This network structureimplicates handover between coverage and capacity layer triggered bysignal receive level. During call set up the MS is allocated to a highpower TRX. If the downlink receive level is good enough, then the MS ishanded over to a low power TRX. If the receive level falls below acertain threshold again, the MS is handed over back to the coveragelayer. This mechanism is analogue to IUO, where the handover betweencoverage and capacity layer is based on the C/I ratio. Therefore for ICEthe terms regular (= coverage) and super (= capacity) layer often areused as well.

ICE is enabled by the same parameter superReuseEstMethod (METH)(HOC)(AVE,MAX,ICE,NONE)(NONE)as IUO, but now it has to be set to

ICE instead to AVE or MAX. The type of TRX is defined again by theparameter trxFrequencyType (FRT)(TRX)(0..16)(0). 0 indicates aregular (now high power) TRX, 1 to 16 the frequency group of a super(now low power) TRX as usual (see Fig. 9-1).


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NOKIA BSSPAR / 10.05.2004

CoverageEnhancement

Features

Normal ICE(Idea)

Hopping TRX'sHigh power TRX (BCCH)

Low power TRX (no BCCH)

Two layer network

Coverage layer = high power TRXs (BCCH)Capacity layer = low power TRXs (no BCCH)

Basic parameters

superReuseEstMethod AVE, MAX, ICE, NONE must be s et t o ICEtrxFrequencyType 0..16 0 = coverage (BCCH) TRX

1..16 = capacity (non BCCH) TRX

Fig. 9-1: Normal ICE (idea)

9.2.2 Handover between Low / High Power TRX

The handover between coverage and capacity layer now is triggered bythe downlink receive level. It is measured and averaged as usual. If the

receive level is better than the threshold defined bysuperReuseGoodRxLevThreshold (CGR)(HOC)(-110..-47)(-80),handover from high to low power TRX is triggered. The threshold isconsidered to be exceeded, if at least Px (CGP)(HOC)(1..32)(8)of thelast Nx (CGN)(HOC)(1..32)(10)average samples are above the limit. Ifthe receive level falls below the threshold defined bysuperReuseBadRxLevThreshold (CBR)(HOC)(-110..-47)(-85),handover from low to high power TRX is triggered. The limit must beexceeded by at least Px (CBP)(HOC)(1..32)(2) of the last Nx (CBN)(HOC)(1..32)(6)average samples (see Fig. 9-2).

Handover between high and low power TRXs always is an intra cellhandover. Handover between low power TRXs of different frequency

groups, which is possible as well, is an intra cell handover also.Like IUO, ICE allows direct access to the capacity layer during call setup, if the receive level for the serving high power TRX is high enough. Ifone average sample exceeds the limit set by directAccessLevel


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(DAL)(TRX)(-109..-47,N)(N), the MS is allocated directly to a low powerTRX. With the default setting direct access is disabled.

Direct access can be a intra or inter cell handover, from high powerSDCCH to low power TCH. If no TCH is available from a low power

TRX, it is taken from a high power TRX in both cases.

NOKIA BSSP AR / 10.05.2004

CoverageEnhancement

Features

Normal IC E(Handover)

- 70

- 80

- 90

-100

-110

superReuseGoodRxLevThreshold -110..-47 dB m

call is handed over to low power TRX

call is handed ove r to high power TRX

High power TRX

Low power TRX

superReuseBadRxLevThreshold -110..-47 dB m

Handover

Threshold exceeded by at least Px of the last Nx average samples-> intra cell handover from one layer to the other

Direct access

On the SDCCH, one average sample exceeds directAccessLevel-> TCH taken directly from low power TRX

Fig. 9-2: Normal ICE (handover)

9.3 Inverse Intelligent Coverage Enhancement

9.3.1 Idea

Frequency hopping usually is used to improve the capacity of a cellularnetwork. Because of the frequency diversity gain, however, frequencyhopping can be used also to improve the coverage.

The frequency diversity gain increases with the number of frequenciesincluded in the hopping sequence. The environment effects the gain aswell. In rural areas often there is direct line of sight between MS andBTS and thus no strong multi path propagation effect. Thus frequencyhopping offers less gain than in a city environment.


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Using frequency hopping to improve coverage, leads to a networkdesign just opposite to ICE, therefore called inverse ICE. The coveragelayer now is built of non BCCH TRXs, as these must be the hoppingones. The capacity layer basically is built of BCCH TRXs, which do nothop in case of RF hopping.

Inverse ICE is enabled by the same way as ICE, by setting theparameter superReuseEstMethod to ICE. The parametertrxFrequencyType, however, now is applied the other way round. Fornon BCCH (hopping) TRXs it is to 0, for BCCH (non hopping) TRXs to1..16 (see Fig. 9-3).

NOKIA BSSPAR / 10.05.2004

CoverageEnhancement

Features

Invers e ICE(Idea)

Hopp ing TRX ' sHopp ing TRX (no BCC H)

Non hopp ing TRX (BCCH)

Two layer network

Coverage layer = hopping TRXs (no BCCH)Capacity layer = at least one non hopping TRX ( with BCCH)Use of BCCH TRX inverse to normal ICE

Use of frequency hopping for coverage improvement

RF hopping requiredGood frequency diversity gain for city environment (about 4 dB)

Basic parameters

superReuseEstMethod AVE, MAX, ICE, NONE must be set to ICEtrxFrequencyType 0..16 0 = coverage (no BCCH) TRX

1..16 = capacity (at least one with BCCH) TRX

Fig. 9-3: Inverse ICE (idea)

Of course, the capacity layer also can have hopping TRXs. Considere.g. a cell with 2 TRXs in the coverage layer (no BCCH,trxFrequencyType = 0 for both) and with 2 TRXs in the capacity layer(one BCCH TRX with trxFrequencyType = 1 and a non BCCH TRX withtrxFrequencyType = 2). The hopping characteristics of TRXs in thecapacity layer are set by the intelligent frequency hopping parametersunderlayHoppingMode, underlayhoppingSequenceNumber,underlayMA, underlayMaioOffset and underlayMaioStep discussed

already in chapter Intelligent Underlay Overlay, section Introduction.


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9.3.2 Handover for Inverse ICE

When a call is set up, the MS first is allocated to a SDCCH taken fromthe BCCH TRX, even if it is at the edge of the cell. This is possible dueto the robustness of the BCCH and SDCCH channels. If the path loss is

too high, however, than a TCH is taken from a TRX of the coveragelayer.

The handover between the two layers of an inverse ICE network istriggered by the same thresholds as for an ICE network. If the downlinkreceive level exceeds superReuseGoodRxLevThreshold, the MS ishanded over from the coverage to the capacity layer. If the receive levelfalls below superReuseBadRxLevThreshold, handover back to thecoverage layer is performed (see Fig. 9-4.

NOKIA BSSP AR / 10.05.2004

CoverageEnhancement

Features

Invers e IC E(Handover)

- 70

- 80

- 90

-100

-110

superReuseGoodRxLevThreshold -110..-47 dB m

call is handed over to non hopping T RX

call is handed over to hopping TRX

Hopping TRXNon hopping TR X

superReuseBadRxLevThreshold -110..-47 dB m

Call set up

SDCCH taken from BCCH TRX even at cell edgeToo high path loss -> TCH taken from hopping TRX

Handover

Threshold exceeded by at least Px of the last Nx average samples-> intra cell handover from one layer to the other

Frequencydivers ity gain

Fig. 9-4: Inverse ICE (handover)

bsspar chapter 09 coverage enhancement features mo

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