networking modes

Networking Modes Feature Parameter Description

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

BSS Networking Modes Contents

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

iii

Contents 1 Introduction ................................................................................................................................1-1

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

2 Overview of Networking Modes ............................................................................................2-1

3 Technical Description ..............................................................................................................3-1 3.1 Networking Modes......................................................................................................................... 3-1

3.1.1 Star Networking Mode .......................................................................................................... 3-1 3.1.2 Chain Networking Mode ....................................................................................................... 3-1 3.1.3 Tree Networking Mode ......................................................................................................... 3-2 3.1.4 Ring Networking Mode ......................................................................................................... 3-3

3.2 LAPD Multiplexing at Abis Interface.............................................................................................. 3-4 3.3 16 kbit/s LAPD Signaling Link ....................................................................................................... 3-4

4 Engineering Guidelines...........................................................................................................4-1 4.1 Configuration Principles of the Star Networking Mode.................................................................. 4-1 4.2 Configuration Principles of the Chain Networking Mode .............................................................. 4-1 4.3 Configuration Principles of the Tree Networking Mode................................................................. 4-1 4.4 Configuration Principles of the Ring Networking Mode................................................................. 4-1

5 Parameters .................................................................................................................................5-1

6 Counters......................................................................................................................................6-1

7 Glossary ......................................................................................................................................7-1

8 Reference Documents .............................................................................................................8-1

BSS Networking Modes 1 Introduction


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1 Introduction 1.1 Scope This document describes the networking modes, LAPD multiplexing at Abis interface, and 16 kbit/s LAPD signaling link.

1.2 Intended Audience This document is intended for:

Personnel who need to understand Networking Modes Personnel who work with Huawei products

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: refers to the change in the networking modes feature of a specific product version. 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), issue 02 (2009-09-30) 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.

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

Compared with issue 01 (2009-04-30) of BSS8.1, issue 01 (2009-06-30) of GBSS9.0 has no change.

BSSBSS Networking ModesNetworking Modes 2 Overview of Networking Modes


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2 Overview of Networking Modes Networking mode refers to the mode of connections between the BTS and the BSC. The networking mode can be star, chain, tree, or ring networking mode. In actual engineering scenarios, a combination of the networking modes is usually applied.

Reasonable application of the networking modes can greatly reduce the investment in the transmission equipment while providing satisfactory service quality. An operator can select an appropriate networking mode according to the actual equipment and transmission.

The BSC supports flexible networking modes over the Abis interface: star, chain, tree, and ring.

Star networking mode The star networking mode applies to common scenarios, especially densely populated areas such as urban areas.

Chain networking mode The chain networking mode applies to sparsely populated areas in the strip-like terrain, such as areas along highways and railway tracks.

Tree networking mode The tree networking mode applies to areas where network structures, BTS distribution, and subscriber distribution are complicated, such as the overlapping areas between the large-scale coverage and the hot spot or between the large-scale coverage and the small-scale coverage.

Ring networking mode The ring networking mode applies to common scenarios. Due to its strong self-healing capability, the ring networking mode is preferably applied so long as the transmission links meet the networking requirements.

The Link Access Protocol on the D Channel (LAPD) link has two configuration modes: LAPD multiplexing at Abis interface and 16 kbit/s LAPD signaling link. All the signaling links of a BTS can be configured in only one mode.

BSSBSSBSS Networking ModesNetworking Modes 3 Technical Description


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3 Technical Description 3.1 Networking Modes 3.1.1 Star Networking Mode In star networking mode, each BTS is directly connected to the BSC and the BTS is not connected to other BTSs. The star networking mode is the commonest networking mode. It is typically used in the densely populated areas, such as cities. Figure 3-1 shows the star networking mode.

Figure 3-1 Star networking mode

BTS

BTSBTS

BSC

Advantages:

Simple networking Easy engineering Convenient maintenance Flexible capacity expansion High network reliability

Disadvantages:

Compared with other networking modes, the star networking mode requires more transmission cables. In the case of small-capacity BTS, the transmission resource usage of the star networking mode is low. To solve this problem, the timeslot cross connection device can be used.

3.1.2 Chain Networking Mode In chain networking mode, BTSs are cascaded on a chain. Each BTS on the chain processes its own timeslots and transparently transmits the signals on the timeslots of the lower-level BTSs. Figure 3-2 shows the chain networking mode.

3 Technical Description BSSBSSBSS

Networking ModesNetworking Modes

3-2 Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd

Issue 02 (2009-09-30)

Figure 3-2 Chain networking mode

BTS BTSBTSBSC

The chain networking mode applies to sparsely populated areas in strip-like terrain, such as areas along highways and railway tracks. If the star networking mode is used in this scenario, transmission resources may be wasted. To avoid the waste, the chain networking mode can be applied.

Advantages:

The chain networking mode can reduce the cost of transmission equipment and engineering construction and save the rent for the transmission links.

Disadvantages:

The reliability of the transmission link is poor because the signal transmission passes through multiple nodes.

A faulty BTS may affect the normal operation of its lower-level BTSs. The number of cascading levels must not exceed five.

3.1.3 Tree Networking Mode In tree networking mode, a BTS is connected to more than one lower-level BTS. The tree networking mode is actually a combination of the chain and star networking modes. Figure 3-3 shows the tree networking mode.

Figure 3-3 Tree networking mode

BTS

BTS

BTSBSC BTS



3-3

The tree networking mode has the characteristics of the star and chain networking modes. It has a higher reliability than the chain networking mode but a lower reliability than the star networking mode.

Advantages:

The tree networking mode requires less transmission cables than the star networking mode.

Disadvantages:

In tree networking mode, the signal transmission passes through multiple nodes; therefore, the transmission reliability is relatively low, the engineering construction is difficult, and it is not convenient to maintain.

A faulty BTS may affect the normal operation of its lower-level BTSs. Capacity expansion is difficult because it may require major modification to the network structure. The number of cascading levels must not exceed five.

3.1.4 Ring Networking Mode The ring networking mode is a special chain or star networking mode. Several BTSs form a chain, and the lowest-level BTS is connected to the BSC, thus forming a ring. If there is a breaking point on the ring, the BTSs that precede the breakpoint remain unchanged in networking mode whereas the BTSs that follow the breakpoint form a new chain connection in the reverse direction. For details, see BTS Ring Topology Parameter Description. Figure 3-4 shows the ring networking mode.

Figure 3-4 Ring networking mode

BTSBTS

BTS

BSC

The ring networking mode applies to common scenarios. Due to its strong self-healing capability, the ring topology is preferably applied so as long transmission is permitted.

Advantages:

The ring networking mode has a strong self-healing capability. If the E1 link at a point is broken, a new chain connection can be formed without affecting the ongoing services.

Disadvantages:

There is always a transmission link segment that does not transmit any data.

3 Technical Description BSSBSSBSS



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3.2 LAPD Multiplexing at Abis Interface LAPD multiplexing refers to the multiplexing of the LAPD signaling on the E1 timeslots over the Abis interface. The BSC supports six n:1 (n <= 6) 64 kbit/s multiplexing modes: 1:1, 2:1, 3:1, 4:1, 5:1, and 6:1. The multiplexing of the LAPD signaling can increase the transmission link utilization on the Abis interface and reduce the cost of the operator.

In n:1 E1 timeslot multiplexing mode, the speech rate is 16 kbit/s (full rate) or 8 kbit/s (half rate) and four full-rate (or eight half-rate) speech channels occupy one 64 kbit/s E1 timeslot; the rate of the signaling link is 64 kbit/s, and n signaling timeslots occupy one 64 kbit/s E1 timeslot. The Abis interface board (EIUa/OIUa) in the BSC implements the 64 kbit/s switching of all the timeslots.

A EIUa or OIUa in the BSC can support more than one multiplexing mode at the same time. Signals can be transparently transmitted between cascaded BTSs; therefore, an E1 link can also support multiple multiplexing modes, as shown in Figure 3-5.

Figure 3-5 Application of multiple multiplexing modes

EIUa/OIUaBTS0 BTS1

BTS2

BTS3A0 A1 A3

A2

As shown in Figure 3-5, the four E1 links are A0, A1, A2, and A3. Assume that the multiplexing modes of BTS0, BTS1, BTS2, and BTS3 are 1:1, 1:2, 1:3, and 1:4 respectively. Then, there are four multiplexing modes on the EIUa/OIUa.

There are four multiplexing modes on A0. There are two multiplexing modes on A1: 2:1 and 4:1. There is one multiplexing mode on A2: 3:1. There is one multiplexing mode on A3: 4:1.

Suggestions on Selecting the Multiplexing Mode

When the TRX supports the half rate feature, the 2:1 multiplexing ratio is recommended; if all the TRXs are in full rate, the 4:1 or higher multiplexing ratio is recommended. The LAPD multiplexing mode is specified by Multiplexing Mode.

3.3 16 kbit/s LAPD Signaling Link When the function of the 16 kbit/s LAPD signaling link (OML and RSL) is enabled, each signaling link occupies only 16 kbit/s bandwidth at the physical layer, thus saving the transmission resources on the Abis interface. The multiplexing mode of the 16 kbit/s LAPD signaling link can be specified by Multiplexing Mode.

The typical application scenarios are as follows:

When the capacity of the BTS is low, such as O1 or O2, the 16 kbit/s LAPD signaling link can be used to minimize the transmission resources required over the Abis interface.



3-5

The rent for the satellite transmission resources is very high. The 16 kbit/s LAPD signaling link can save bandwidth, and thus can be used in satellite transmission mode.

The function of 16 kbit/s LAPD signaling link supports the following:

Each RSL timeslot and each OML timeslot occupy a 16 kbit/s sub-timeslot respectively. The 16 kbit/s signaling timeslot and the traffic timeslot can be configured in one 64 kbit/s timeslot on the Abis interface.

The signaling timeslots of different BTSs can be distributed in one 64 kbit/s timeslot.

Disadvantages:

The bandwidth of each signaling link is limited to 16 kbit/s; therefore, for the TRX with high traffic volume, data loss due to RSL congestion may occur.

Constraints:

The BTS that uses the 16 kbit/s LAPD signaling link supports the tree networking mode; however, all the BTSs in the tree topology must use the 16 kbit/s LAPD signaling link.

If the BTS that uses the 16 kbit/s LAPD signaling link supports the Abis bypass function, the OMLs and RSLs distributed (not multiplexed) on a 64 kbit/s timeslot must be distributed on one 64 kbit/s timeslot with the timeslot number unchanged in the E1 links of other cascaded BTSs.

The 16 kbit/s LAPD signaling link cannot be configured in ring networking mode.

BSSBSSBSS Networking ModesNetworking Modes 4 Engineering Guidelines


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4 Engineering Guidelines 4.1 Configuration Principles of the Star Networking Mode

Any BTS in Time Division Multiplexing (TDM) transmission mode is directly connected to the EIUa or OIUa in the BSC through one or more E1 links without the need of other transit BTSs.

Any BTS in transmission optimization mode is directly connected to the GEHUB in the BSC through one or more E1 links without the need of other transit BTSs.

Any BTS in IP transmission mode is connected to a router or switch through an FE port without the transit of other BTSs.

4.2 Configuration Principles of the Chain Networking Mode The chain networking mode is classified into single-link cascading mode and multi-link cascading mode.

Single-link cascading mode: used when the number of cascaded BTSs is smaller than 5 and the total number of TRXs is smaller than 15.

Multi-link cascading mode: used when the number of cascaded BTSs is smaller than 5 and the total number of TRXs is greater than 15. A BTS can provide up to eight E1 ports; therefore, a maximum of eight primary and secondary links can be configured in multi-link cascading mode.

The 3012 and 3900 series base stations can be configured with a bypass board to bypass the E1 signals when the BTS

is powered off, thus ensuring the reliability of the entire chain network. If a BTS is at the lowest level in a chain network, the bypass board can perform the loopback test on the transmission

link when the BTS is powered off. The result of the loopback test can be used for identifying the fault.

4.3 Configuration Principles of the Tree Networking Mode If the BTS directly connected to the EIUa/OIUa is in single-link cascading mode, a maximum of 15 TRXs can be configured on this root BTS.

If the BTS directly connected to the EIUa/OIUa is in multi-link cascading mode, the maximum number of TRXs on this root BTS depends on the number of E1 timeslots.

For the BTSs in transmission optimization mode, the upper-level BTS provides transparent transmission of timeslot signals for the lower-level BTSs.

4.4 Configuration Principles of the Ring Networking Mode Compared with the other networking modes, the ring networking mode requires an extra port on the EIUa/OIUa or GEHUB for each ring.

A maximum of five BTSs can be cascaded on a ring. Each BTS on the ring can have the bypass BTS and they are connected in tree networking mode. Along the connection from the bypass BTS on the ring to the BSC, the number of cascaded BTSs must not exceed five.

According to the physical bearer, the BTSs in only TDM or HDLC transmission mode can form a ring network.

BSSBSSBSS Networking ModesNetworking Modes 5 Parameters


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5 Parameters This chapter describes the parameters related to networking modes.

For the meaning of each parameter, see Table 5-1. For the default value, value ranges, and MML commands of each parameter, see Table 5-2.

5 Parameters BSSBSSBSS



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Table 5-1 Parameter description (1)

Parameter Description

BSSBSSBSS Networking ModesNetworking Modes 5 Parameters

30) Copyright © Huawei Technologies Co., Ltd

5-3Issue 02 (2009-09- Huawei Proprietary and Confidential

Parameter Description

Multiplexing Mode

"Timeslot multiplexing mode at the Abis interface of the BTS. The BTS supports two multiplexing modes: statistical multiplexing on a 64 kbit/s timeslot and physical multiplexing on a 16 kbit/s timeslot. The first mode is further classified into the following six types: 1:1, 2:1, 3:1, 4:1, 5:1, and 6:1. A BTS supports the following six types of timeslot objects: OML: operation and maintenance link of the BTS. Each BTS has only one OML. In the case of statistical multiplexing on a 64 kbit/s timeslot, the OML works at 64 kbit/s. In this case, the OML can be multiplexed only with the signaling links in the same cabinet group of the BTS. In the case of physical multiplexing on a 16 kbit/s timeslot, the OML works at 16 kbit/s. In this case, the OML uses a 16 kbit/s timeslot. ESL: extended signaling link of the BTS. If the BTS supports Flex Abis, in the case of statistical multiplexing on a 64 kbit/s timeslot, a 64 kbit/s timeslot needs to be assigned to the ESL. In this case, the ESL is always multiplexed with the OML in the 64 kbit/s timeslot. In the case of physical multiplexing on a 16 kbit/s timeslot, no timeslot is assigned to the ESL. In this case, the ESL shares the same timeslot with the OML. RSL: radio signaling layer link in each TRX. Each TRX has one RSL link. In the case of statistical multiplexing on a 64 kbit/s timeslot, the RSL link works at 64kbit/s. In this case, the RSL link can be multiplexed only with the signaling links in the same cabinet group of the BTS. In the case of physical multiplexing on a 16 kbit/s timeslot, the RSL link works at 16 kbit/s. In this case, the RSL link uses a 16 kbit/s timeslot exclusively. TCH: traffic channels in each TRX. The TCH works at 16 kbit/s. Idle: idle timeslots of the BTS. An idle timeslot works at 16 kbit/s. In the case of statistical multiplexing on a 64 kibt/s timeslot, the idle timeslots can be multiplexed only with the TCHs in the same cabinet group onto one 64 kbit/s timeslot. Semi: monitoring timeslots of the BTS. The monitoring timeslots work at 8 kbit/s, 16 kbit/s, 32 kbit/s, and 64 kbit/s. The monitoring timeslots can be multiplexed only with semi-permanent links. A 2048 Mbit/s E1 contains thirty-two 64 kbit/s timeslots. Timeslot 0 is reserved for synchronization and cannot be assigned. Statistical multiplexing means that signaling timeslots are time-division multiplexed in an E1 timeslot, such as the OML and RSL timeslots or the RSL timeslots. For example, in the case of 4:1 multiplexing, one 64 kbit/s timeslot multiplexes one OML and three RSL links or four RSL links of the BTS. The 64 kbit/s timeslot that multiplexes the OML has a multiplexing ratio of up to 4:1 even if the multiplexing ratio exceeds 4:1.

5 Parameters BSSBSSBSS



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Table 5-2 Parameter description (2)

Parameter Default Value

GUI Value Range

Actual Value Range

Unit

MML Command

Impact

Multiplexing Mode MODE4_1

MODE1_1, MODE2_1, MODE3_1, MODE4_1, MODE5_1, MODE6_1, MODE16K

MODE1_1, MODE2_1, MODE3_1, MODE4_1, MODE5_1, MODE6_1, MODE16K

None

ADD BTS(Optional) BTS

BSSBSSBSS Networking ModesNetworking Modes 6 Counters


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6 Counters None.

BSSBSSBSS Networking ModesNetworking Modes 7 Glossary


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

BSSBSS Networking ModesNetworking Modes 8 Reference Documents


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8 Reference Documents BSC6900 Feature List BSC6900 Basic Feature Description BSC6900 GSM Parameter Reference BSC6900 GSM MML Command Reference

networking modes

Documents

huawei trademarks

star networking mode

chain networking mode

tree networking mode

ring networking mode

huawei proprietary

overview of networking

configuration principles