antenna frequency hopping

Antenna Frequency Hopping Feature Parameter Description

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The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute the warranty of any kind, express or implied.

Issue 02 (2009-09-30) Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd. i

BSS Antenna Frequency Hopping Contents

Issue 02 (2009-09-30) Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd.

iii

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 Antenna Hopping Selection Algorithm........................................................................................... 3-1 3.2 Relation Between Antenna Frequency Hopping and Frequency Hopping ................................... 3-1

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

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

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

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

BSS Antenna Frequency Hopping 1 Introduction to This Document


1-1

1 Introduction to This Document 1.1 Scope This document describes the antenna frequency hopping feature. It provides antenna hopping selection algorithm, and relation between antenna frequency hopping and frequency hopping of this feature.

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:

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

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

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

z Feature change Feature change refers to the change in the antenna frequency hopping feature of a specific product version.

z 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:

z 02 (2009-09-30) z 01 (2009-06-30)

02 (2009-09-30) This is the second commercial release of GBSS9.0.

Compared with issue 01 (2009-06-30) of GBSS9.0, issue 02 (2009-09-30) of GBSS9.0 incorporates the changes described in the following table.

Change Type

Change Description Parameter Change

Feature change

None. None.

Editorial change

The structure of the document is optimized.

None.

1 Introduction to This Document BSS

Antenna Frequency Hopping

1-2 Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd.

Issue 02 (2009-09-30)

01 (2009-06-30) This is the first commercial release of GBSS9.0.

Compared with issue 01 (2009-04-30) of GBSS8.1, issue 01 (2009-06-30) of GBSS9.0 remains unchanged.

BSS Antenna Frequency Hopping 2 Overview


2-1

2 Overview During a CS call or a PS data session, a single burst transmitted over the Um interface may be lost due to interference or multipath fading. Thus proper coding and interleaving schemes are adopted in GSM to minimize the impact of interference or multipath fading. If a speech frame is divided into multiple bursts for transmission, the loss of a single burst has minimal impact on the speech quality. Antenna frequency hopping can provide transmit diversity. Antenna frequency hopping can provide transmit diversity. After the antenna frequency hopping is introduced, all the bursts of a speech frame are transmitted on different paths. In this manner, the bursts are unlikely to be lost and the speech quality is ensured.

When traffic channels do not participate in frequency hopping or only a small number of frequencies participate in frequency hopping, antenna frequency hopping brings substantial diversity gains without increasing the number of frequencies in a base station.

In the case of slow-moving MSs with low coding rates, antenna frequency hopping brings substantial diversity gains. In the case of fast-moving MSs with low coding rates (for example, the MSs are moving along high-speed railways in the coverage area), antenna frequency hopping brings few diversity gains. In the case of high coding rates or no coding, antenna frequency hopping brings negative diversity gains.

Antenna frequency hopping provides transmit diversity on the downlink. As shown in Figure 2-1, user data is coded and interleaved to obtain the transmit signal S. S is divided into S1 and S2, which are then transmitted through different antennas. In this manner, the probability that all the data of a user is lost is reduced. In addition, the anti-attenuation capability of the receiver and the speech quality of the slow-moving MS are improved. The downlink coverage area is also enlarged. Downlink transmit diversity is used to overcome fast fading. Therefore, antenna frequency hopping is mainly applied in propagation scenarios where multipath fading exists, for example, in suburban areas where wide coverage is required.

Figure 2-1 Schematic drawing of antenna frequency hopping

S

S1

S2

With antenna frequency hopping, the system selects some TRXs in the serving cell according to the antenna hopping selection algorithm to transmit the downlink data of a user. Thus, the data of the user is transmitted by different antennas connected to these TRXs. All the TRXs used to transmit the data of the same user form a TRX group. Each TRX in the TRX group has the same transmit power, for example, when all the TRXs serve the underlaid or overlaid subcell of a concentric cell. The antennas that are connected to the TRXs in one TRX group form an antenna hopping set. Each antenna hopping set should have at least two antennas.

BSS Antenna Frequency Hopping 3 Technical Description


3-1

3 Technical Description 3.1 Antenna Hopping Selection Algorithm The Cell Antenna Hopping parameter must be set to Yes before antenna frequency hopping is enabled. In addition, the TRX group and TRXHSN must be specified. If radio frequency hopping or no frequency hopping is enabled in the serving cell, the TRX group can contain any TRX in the cell. If baseband frequency hopping is enabled in the serving cell, the TRXs in the TRX group should be the same as those participating in baseband frequency hopping. After the TRX group is configured, each TRX in the TRX group is allocated a TRXIO.

The antenna hopping selection algorithm is expressed as follows: TRXI = (S + TRXIO) mod N

Here,

TRXI indicates the index of a TRX in a TRX group. Its value ranges from 0 to N-1.

TRXIO indicates the initial offset of a TRX in a TRX group. Its value ranges from 0 to N-1.

N indicates the number of TRXs in a TRX group.

FN indicates the number of a TDMA frame and it is broadcast on the SCH. The MS synchronizes with the base station by adjusting the FN (ranging from 0 to 2,715,647).

TRXHSN indicates the hopping sequence number (ranging from 0 to 63) of a TRX group.

z If TRXHSN is equal to 0, then cyclic frequency hopping is applied and S is equal to FN. z If TRXHSN is not equal to 0, S is calculated according to the frequency hopping algorithm. For details

of the frequency hopping algorithm, see 3GPP TS 45.002 "Hopping sequence generation."

Based on the obtained TRXI, the system searches the TRX group for a TRX for user data transmission.

3.2 Relation Between Antenna Frequency Hopping and Frequency Hopping Antenna frequency hopping can be applied in the cells of the following types: non-frequency hopping, radio frequency hopping, and baseband frequency hopping. When traffic channels do not participate in frequency hopping or only a small number of frequencies participate in frequency hopping, antenna frequency hopping can bring substantial diversity gains.

If baseband frequency hopping is enabled in a cell, user data is transmitted by different TRXs except the BCCH TRX. This brings about the same effect as antenna frequency hopping. In baseband frequency hopping, timeslot 0 of the BCCH TRX does not participate in frequency hopping. In a GSM cell, timeslot 0 of the BCCH TRX, however, is used by an MS in idle mode to search for the network or by an MS in dedicated mode to measure the receive level of neighboring cells. If an MS is located in an area where it is difficult to receive the messages from the BCCH TRX or if the antenna connected to the BCCH TRX is damaged, then the MS cannot receive the broadcast control messages from the BCCH TRX properly. Similar to baseband frequency hopping, antenna frequency hopping enables the data of all the timeslots on the BCCH TRX to be transmitted on the antennas connected to all the TRXs in the cell in sequence. This increases the space diversity and optimizes the data reception of the MS from the BCCH TRX. Thus, the network performance is improved.

BSS Antenna Frequency Hopping 4 Parameters


4-1

4 Parameters The following describes the parameters related to antenna frequency hopping.

For the meaning of each parameter, see Table 4-1. For the default value, value range, and related MML commands of each parameter, see Table 4-2.

Table 4-1 Parameter description (1)

Parameter Description

Cell Antenna Hopping

Whether to enable the TRX to support antenna hopping In a GSM cell, the BCCH broadcasts the frequency, frame number, system information, and paging group. If an MS is in an unfavorable position or the antenna of the main TRX that carries the BCCH fails, the MS receives poor broadcast control signals or even cannot receive any broadcast control message from the BCCH. To avoid such a problem, the antenna hopping function is involved. With this function, the messages transmitted in the main TRX that carries the BCCH are also transmitted on the antennas of all the other TRXs in the cell in turn. This helps the MSs receive quality broadcast control data. This function can be configured only for dual-frequency BTSs.

Table 4-2 Parameter description (2)

Parameter

Default Value

GUI Value Range

Actual Value Range

Unit MML Command

Impact

Cell Antenna Hopping NONE

NO_HPANT(No), YES_HPANT(Yes), NONE(None)

NO_HPANT, YES_HPANT, NONE None

SET GCELLHOPANT(Optional) Cell

BSS Antenna Frequency Hopping 5 Counters


5-1

5 Counters None.

BSS Antenna Frequency Hopping 6 Glossary


6-1

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

BSS Antenna Frequency Hopping 7 Reference Documents


7-1

7 Reference Documents z 3GPP TS 45.002 "Hopping sequence generation" z BSC6900 Feature List z BSC6900 Optional Feature Description z GBSS Reconfiguration Guide z BSC6900 GSM Parameter Reference z BSC6900 GSM MML Command Reference

1 Introduction to This Document 1.1 Scope 1.2 Intended Audience 1.3 Change History 2 Overview 3 Technical Description 3.1 Antenna Hopping Selection Algorithm 3.2 Relation Between Antenna Frequency Hopping and Frequency Hopping

4 Parameters 5 Counters 6 Glossary 7 Reference Documents