HUawei 2G 2-Antenna Receive Diversity

GSM BSS

2-Antenna Receive Diversity Feature Parameter Description

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GSM BSS 2-Antenna Receive Diversity Contents

Issue 01 (2010-06-30) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

i

Contents 1 Introduction to This Document .............................................................................................1-1

1.1 Scope ............................................................................................................................................ 1-1 1.2 Intended Audience ........................................................................................................................ 1-1 1.3 Change History.............................................................................................................................. 1-1

2 Overview .....................................................................................................................................2-1

3 Technical Description ..............................................................................................................3-1 3.1 Technical Principle......................................................................................................................... 3-1 3.2 Diversity Combining Algorithms .................................................................................................... 3-1

3.2.1 MRC...................................................................................................................................... 3-1 3.2.2 ICC........................................................................................................................................ 3-1 3.2.3 EICC ..................................................................................................................................... 3-2

4 Parameters .................................................................................................................................4-1

5 Counters......................................................................................................................................5-1

6 Glossary ......................................................................................................................................6-1

7 Reference Documents .............................................................................................................7-1

GSM BSS 2-Antenna Receive Diversity 1 Introduction to This Document


1-1

1 Introduction to This Document 1.1 Scope This document describes the working principle of 2-antenna receive diversity and the diversity combining algorithms.

1.2 Intended Audience It is assumed that users of this document are familiar with GSM basics and have a working knowledge of GSM telecommunication.

This document is intended for:

Personnel working on Huawei GSM products or systems System operators who need a general understanding of this feature

1.3 Change History The change history provides information on the changes between different document versions.

There are two types of changes, which are defined as follows:

Feature change Feature change refers to the change in the 2-Antenna receive diversity feature of a specific product version.

Editorial change Editorial change refers to the change in wording or the addition of the information that was not described in the earlier version.

Document Issues The document issues are as follows:

01 (2010-06-30) Draft (2010-03-30)

01 (2010-06-30) This is the first release of GBSS12.0.

Compared with issue draft (2010-03-30) of GBSS12.0, issue 01 (2010-06-30) of GBSS12.0 incorporates the changes described in the following table.

Change Type Change Description Parameter Change

Feature change None. None.

Editorial change Parameters are presented in the form of Parameter ID instead of Parameter Name.

None.

Draft (2010-03-30) This is the draft release of GBSS12.0.

GSM BSS 2-Antenna Receive Diversity 2 Overview


2-1

2 Overview In a wireless communications system, the radio signal from the transmitter arrives at the receiver through two or more paths. This phenomenon is called multipath propagation. With multipath propagation, the amplitude, phase, and angle of the received signal change. This phenomenon is called multipath fading. As a result, the quality of the received signal deteriorates. Diversity is one of the techniques used to handle multipath fading in the communications system. It increases the signal-to-noise ratio by superimposing uncorrelated signals.

The diversity technique in GSM involves time diversity, frequency diversity, and space diversity. In the case of space diversity, multiple antennas are used at the receiver to receive uncorrelated signals of the same source (superimposition of uncorrelated signals). In engineering implementation, generally two antennas (or two polarization ends of the same polarization antenna) are used to receive signals. The signals received from the two antennas can be combined in different ways to obtain desired signals, for example, Maximal Ratio Combining (MRC), Interference Cancellation Combining (ICC), and Enhanced Interference Rejection Combining (EICC).

GSM BSS 2-Antenna Receive Diversity 3 Technical Description


3-1

3 Technical Description 3.1 Technical Principle The 2-antenna receive diversity technique combines the signals received from the two diverse antennas at the receiving end to mitigate multipath interference. Figure 3-1 shows the working principle of 2-antenna receive diversity.

Figure 3-1 Working principle of 2-antenna receive diversity

W1

y(k)

RX channel 1

RX channel 2

x(k)

)(2 kr

)(kr1 )(kS1

)(kS2

W2

Signal

RX signal

RX signal

Noise and interference

Noise and interference

As shown in Figure 3-1:

1. The signal x(k) arrives at the diverse antennas through two RX channels. The two RX signals are identified as r1(k) and r2(k). After the superimposition of interference and noise, the two RX signals are identified as S1(k) and S2(k).

2. Based on the maximum signal-to-noise ratio criterion, the adaptive combining coefficients W1 and W2 are calculated and the output signal is obtained through the formula: y(k) = W1 x S1(k) + W2 x S2(k).

The combining algorithms consist of the MRC, ICC, and EICC. In Figure 3-1 the two RX channels correspond to the main and diversity RX channels of the TRX.

You should set RCVMD to Main Diversity to enable the 2-Antenna Receive Diversity feature.

3.2 Diversity Combining Algorithms 3.2.1 MRC MRC performs weighted combining on the two signals received by the BTS based on their respective signal-to-noise ratios. This combining method is ideal for situations with little interference and limited noise. It is applicable to wide coverage and overseas coverage.

3.2.2 ICC ICC is a multi-antenna combining technique developed from MRC. In tight frequency reuse scenarios the interfering signals received at diverse antennas may come from the same interfering source. Therefore, a certain correlation exists among these interfering signals. ICC uses this correlation when combining the signals of the two antennas to eliminate certain interference. The use of ICC can improve the speech quality and data throughput in situations with strong interference, for example, the network where tight frequency reuse is in place. ICC can suppress the interference within the GSM system and from other systems if correlation exists between the interfering signals received on diverse antennas.

GSM BSS 2-Antenna Receive Diversity 3 Technical Description


3-2

3.2.3 EICC EICC is developed from ICC. Generally, the interfering signals received from multiple antennas are both space correlated (among the antennas) and time correlated. The difference between ICC and EICC is that ICC considers only space correlation to eliminate interference whereas EICC considers both space correlation and time correlation to suppress and eliminate interference. EICC is mainly used in high traffic network where tight frequency reuse is in place and in situations where the noise of a single interfering source is limited. The EICC performs better than ICC. (GBFD-115821 EICC)

You should set STIRCALLOWED to YES to select the EICC algorithm of 2-antenna receive diversity.

When STIRCALLOWED is set to NO, the system selects the ICC algorithm by default.

GSM BSS 2-Antenna Receive Diversity 4 Parameters


4-1

4 Parameters Table 4-1 Parameters Description

Parameter ID NE MML Command Description

RCVMD BSC6900 SET GTRXDEV(Optional)

Meaning: RF receive mode of the TRX. The BTS3012, BTS3012AE, BTS3012II, BTS3006C, and BTS3002E do not support Main Diversity. The DBS3900 GSM and BTS3900 GSM support Four Diversity Receiver and Main Diversity. GUI Value Range: INDEPENDENT(Independent Receiver), DIVIDING(Dividing Receiver), FOURDIVERSITY(Four Diversity Receiver), MAINDIVERSITY(Main Diversity), NONE(None) Actual Value Range: INDEPENDENT, DIVIDING, FOURDIVERSITY, MAINDIVERSITY, NONE Unit: None Default Value: INDEPENDENT

STIRCALLOWED BSC6900 SET GCELLSOFT(Optional)

Meaning: Whether to enable the EICC algorithm. Enhanced Interference Rejection Combining combines the signals received by multiple antennas to obtain better signals. EICC is mainly used in high traffic network where tight frequency reuse is in place. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

GSM BSS 2-Antenna Receive Diversity 5 Counters


5-1

5 Counters None.

GSM BSS 2-Antenna Receive Diversity 6 Glossary


6-1

6 Glossary For the acronyms, abbreviations, terms, and definitions, see the Glossary.

GSM BSS 2-Antenna Receive Diversity 7 Reference Documents


7-1

7 Reference Documents [1] 3GPP TS 25.101, "User Equipment (UE) radio transmission and reception (FDD)" [2] 3GPP TS 25.211, "Physical channels and mapping of transport channels onto physical channels

(FDD)" [3] 3GPP TS 25.306, " UE Radio Access capabilities " [4] 3GPP TS 25.308, "UTRA High Speed Downlink Packet Access (HSPDA); Overall description" [5] 3GPP TS 25.321, "Medium Access Control (MAC) protocol specification" [6] BSC6900 Feature List [7] BSC6900 Basic Feature Description [8] BSC6900 GSM Parameter Reference [9] BSC6900 GSM MML Command Reference

HUawei 2G 2-Antenna Receive Diversity

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