high speed signaling

High-Speed Siganling 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.

Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

BSS High-Speed Siganling Contents

Issue 02 (2009–9–30) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co.,

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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 Implementation of 2 Mbit/s Signaling Link..................................................................................... 3-1 3.2 Comparison Between 2 Mbit/s Signaling Link and 64 kbit/s Signaling Link.................................. 3-3

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

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

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

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

BSS High-Speed Siganling 1 Introduction to This Document


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1 Introduction to This Document 1.1 Scope This document describes the implementation of high-speed signaling links. It also describes the comparison between the high-speed signaling link and the 64 kbit/s signaling link.

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 This section provides information on the changes in different document versions.

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

Feature change Feature change refers to the change in the High-Speed Signaling 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:

02 (2009-09-30) 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 isoptimized.

None.

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

1 Introduction to This Document BSS

High-Speed Siganling

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

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Issue 02 (2009–9–30)

Compared with issue 01 (2009-04-30) of GBSS8.1, issue 01 (2009-06-30) of GBSS9.0 has no change.

BSS High-Speed Siganling 2 Overview


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2 Overview Two types of signaling links are available in the SS7 network: 64 kbit/s signaling link and 2 Mbit/s signaling link.

The 2 Mbit/s signaling link, also called high-speed signaling link, is the No.7 signaling link in the SS7 network with a data rate of N x 64 kbit/s (1 ≤ N < 32). Here, N indicates the number of timeslots occupied by the high-speed signaling link.

The BSC uses the high-speed signaling links when the signaling load of the system is high. The high-speed signaling link has the following features:

A high-speed signaling link occupies multiple 64 kbit/s timeslots with a transmission rate of N × 64 kbit/s (1 ≤ N < 32).

The electrical features of the high-speed signaling link port comply with the ITU-T G.703 and its frame structure complies with the ITU-T G.704.

The naming of the 2 Mbit/s high speed signaling link is specified by the ITU protocols. In actual situations, the maximum data rate of the high-speed signaling link is 1,984 kbit/s.

The BSC uses the high-speed signaling links when the 64 kbit/s signaling links fail to meet the signaling requirements on the A interface due to high traffic volume.

The high speed signaling links are used in the following scenarios:

Some timeslots over a port are used to transmit speech information and the other timeslots are used to transmit signaling information.

A telecom operator chooses high-speed signaling links with different data rates based on the load of the signaling links.

BSS High-Speed Siganling 3 Technical Description


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3 Technical Description 3.1 Implementation of 2 Mbit/s Signaling Link The TDM interface board of the Ater interface or the A interface (EIUa/OIUa/POUc board) processes the signaling of 2 Mbit/s signaling link based on the MTP2 and MTP1 protocols, whereas the 2G signaling processing board (XPUa/XPUb board) processes the signaling based on the MTP3 protocol.

Processing of No.7 Signaling in the BSC The No.7 signaling is processed differently for the BSC subracks configured in different modes.

Figure 3-1 shows the processing of the No.7 signaling in BM/TC separated mode. Figure 3-2 shows the processing of the No.7 signaling in BM/TC combined mode.

Figure 3-1 Signaling link on the A interface (BM/TC separated)

MSC

A

BSC6900

Ater

EIUa

EIUa

EIUa

MPS/EPS TCS

XPUa/XPUb

SCUa

SCUa

1. In the MPS/EPS, the XPUa/XPUb board processes the signaling based on the MTP3, SCCP, and BSSAP protocols, and then forwards the processed signaling to the EIUa/OIUa/POUc board of the Ater interface in the same subrack or in another subrack through the SCUa board.

2. In the MPS/EPS, the EIUa/OIUa/POUc board processes the signaling based on the MTP2 and MTP1 protocols. Then, the processed signaling is forwarded to the EIUa/OIUa/POUc board in the TCS over the Ater interface.

3. In the TCS, the TNU board performs timeslot-based TDM switching of the signaling, and then transmits the signaling to the EIUa/OIUa/POUc board of the A interface.

4. The signaling is transmitted to the MSC over the A interface.

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Figure 3-2 Signaling link on the A interface (BM/TC combined)

A

MSC

BSC6900

EIUa

MPS/EPS

XPUM/XUPb

SCUa

1. In the MPS/EPS, the XPUa/XPUb board processes the signaling based on the MTP3, SCCP, and BSSAP protocols, and then forwards the processed signaling to the EIUa/OIUa/POUc board of the A interface in the same subrack or in another subrack through the SCUa board.

2. The EIUa/OIUa/POUc board of the A interface processes the signaling based on the MTP2 and MTP1 protocols. Then, the signaling is transmitted to the MSC over the A interface.

Configuration Principles The configuration principles are as follows:

Do not allocate timeslot 0 to the 2 Mbit/s signaling link. The timeslots allocated to a 2 Mbit/s signaling link can be discontinuous. When you allocate N (1 ≤ N < 32) 64 kbit/s timeslots to a 2 Mbit/s signaling link, Huawei recommends that N ranges from 8 to 25.

Either 2 Mbit/s signaling link or 64 kbit/s signaling link can be configured for the BSC to communicate with a destination signaling point.

For one EIUa/OIUa board, either 2 Mbit/s signaling link or 64 kbit/s signaling link can be configured. When multiple 2 Mbit/s signaling links are configured, they must be of the same bandwidth.

The 2 Mbit/s signaling links in a BSC must be of the same bandwidth, thus ensuring load balance between different signaling links.

The primary BSC and the secondary BSCs in a TC pool can be configured with 2 Mbit/s signaling links of different bandwidth.

The signaling links in the GSM telecommunications system are very important, and thus the reliability of the 2 Mbit/s signaling links must be taken into account. In actual situations, Huawei recommends that at least two signaling links are available in the same signaling point, and that the two signaling links use different E1 or STM-1. When multiple Ater/A interface boards are configured, the signaling links should be allocated to different boards.

Determine the signaling mode used between the BSC and MSC before configuring the signaling links in the BSC.

Configure the 2 Mbit/s signaling links in the BSC if eight or more 64 kbit/s signaling links are required, considering the signaling transfer capacity between the BSC and MSC.

The TS number of the timeslots allocated for a 2 Mbit/s signaling link must be the same between the BSC and the MSC. Configure the E1 port number based on the connection of the E1 cable.

The BSC6900 supports the MSC POOL feature, which means that one BSC can be connected to multiple MSCs, MSC servers, or MGWs. In this case, you need to configure the No.7 signaling links



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according to the proportion of the A interface CICs between the BSC and the MSCs (MSC Servers or MGWs) to the total A interface CICs.

Each 2 Mbit/s signaling link can be configured only in one E1 port of the Ater/A interface board. Multiple 2 Mbit/s signaling links can be configured in one E1 port of the Ater/A interface board and occupy different timeslots over the E1 port.

If the 2 Mbit/s signaling link on the Ater/A interface board is removed, you need to reset the board before configuring the 64 kbit/s signaling link.

If the 64 kbit/s signaling link on the Ater/A interface board is removed, you need to reset the board before configuring the 2 Mbit/s signaling link.

A maximum of eight 2 Mbit/s signaling links can be configured in one EIUa/OIUa board. A maximum of 64 signaling links can be configured in one POUc board. The number of signaling link timeslots must not exceed 128.

If the 2 Mbit/s signaling links are configured in the BSC, the MTP3 link management entity of the BSC continuously attempts to establish signaling links. Once the signaling links are successfully established, the signaling messages can be transmitted.

3.2 Comparison Between 2 Mbit/s Signaling Link and 64 kbit/s Signaling Link This section compares the 2 Mbit/s signaling link with the 64 kbit/s signaling link in terms of implementation and functions.

Implementation The implementation differences between the 2 Mbit/s signaling link and the 64 kbit/s signaling link are classified into the following types:

Format of signaling messages − The Backward Sequence Number (BSN) and Forward Sequence Number (FSN) in the 64 kbit/s signaling link are 7 bits in length. The BSN and FSN in the 2 Mbit/s signaling link are 12 bits in length, ranging from 0 to 4095. Figure 3-3 shows the formats of the signal units in the 2 Mbit/s signaling link.

− The Length Indicator (LI) in the 64 kbit/s signaling link is 6 bits in length. The LI in the 2 Mbit/s signaling link is 9 bits in length, ranging from 0 to 511. The 9-bit LI can indicate the 272-octet information field supported by the MTP.

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Figure 3-3 Formats of the signal units in the 2 Mbit/s signaling link

T1178370-96

(a) Basic format of a Message Signal Unit (MSU)

(b) Format of a Link Status Signal Unit (LSSU)

(c) Format of a Fill-In Signal Unit (FISU)

123197

FIB

168

F CK SIF SIO Spare Res FSN Res BSN F

First bit transmitted

LI

8n, n≥2 8

BIB

1231 8

123197

FIB

168

F CK SF Spare Res FSN Res BSN F


LI

8 or 16

BIB

1231 8

123197

FIB

168

F CK Spare Res FSN Res BSN F


LIBIB

1231 8

Error correction methods − The 2 Mbit/s signaling link adopts the basic error correction method. This method detects the error signal units by defining the error time segments with flags.

− The 64 kbit/s signal link adopts the preventive cyclic retransmission method. The sequence-related messages such as Changeover-Order signal (COO) and Changeover-Acknowledgement signal (COA) are different in format.

The basic buffer capacity in error correction is as follows: − The retransmission buffer area at the sending end of the 2 Mbit/s signaling link is 4095 in length, greater than that of the 64 kbit/s signaling link.

− The buffer area at the receiving end of the 2 Mbit/s signaling link is greater than that of the 64 kbit/s signaling link.

Functions Delimitation and alignment of signal units The flag byte (F) can be used to delimit a signal unit. The bit pattern for the flag byte is 01111110. The zero-bit insertion method is applied to ensure that the pattern does not incidentally appear in the signal unit. Loss of alignment occurs when a bit pattern disallowed by the delimitation procedure (more than six consecutive 1 s) is received, or when the allowed length of the signal unit is exceeded.

Acceptance procedure Upon detection of an error signal unit, the acceptance procedure defines the time segment with a flag and starts a counter, which is incremented every time a signal unit error is detected. If the counter exceeds the threshold, the signaling link is defined as invalid.

Error detection The error detection function is performed by means of 16 check bits provided at the end of each signal unit.

Error correction The 2 Mbit/s signaling link adopts the basic error correction method, a noncompelled method in which the positive/negative acknowledgements and the retransmission mechanisms are used to ensure correct transfer of message signal units. Before the positive acknowledgements are received, the



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transmitted signal units are stored in the transmitting sequence. This mechanism enables that the transmitted but not yet positively acknowledged signal units remain available for retransmission. The transmission of new signal units is temporarily stopped during retransmissions.

Initial alignment Initial alignment applies to the activation and restoration of a signaling link.

Error monitoring Error monitoring is performed when a signaling link is either in the error time segments or in the proving state of the initial alignment procedure.

Flow Control Upon detection of congestion at the receiving end of the signaling link, the flow control mechanism is activated at the receiving end. A certain status signal of the signaling link is sent to the transmitting end, informing the transmitting end of stopping transmitting the signal units already acknowledged. − If the congestion is released, acknowledgements of input signal units are resumed by the signaling link.

− If the congestion persists, the receiving end periodically sends a link status signal unit to the transmitting end of the signaling link.

− If the congestion period exceeds a predefined threshold, the transmitting end recognizes a signaling link failure and exits the services.

BSS High-Speed Siganling 4 Parameters


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4 Parameters None.

BSS High-Speed Siganling 5 Counters


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5 Counters None.

BSS High-Speed Siganling 6 Glossary


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

BSS High-Speed Siganling 7 Reference Documents


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7 Reference Documents ITU_T Q.703, "Specifications of Signalling System No. 7 - Message transfer part signalling link" BSC6900 Feature List BSC6900 Optional Feature Description BSS Reconfiguration Guide

high speed signaling

Documents

huawei trademarks

huawei proprietary

implementation of highspeed

bss highspeed siganling

intended audience

gsm basics

technical description

change history