Trans-coder Pool

GSM BSS

TC Pool Feature Parameter Description

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

GSM BSS TC Pool 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 Working Principle .......................................................................................................................... 3-1 3.2 Networking .................................................................................................................................... 3-1 3.3 Hardware Cabling.......................................................................................................................... 3-4 3.4 Hardware Management................................................................................................................. 3-7

4 Engineering Guidelines...........................................................................................................4-1

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

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

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

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

GSM BSS TC Pool 1 Introduction to This Document


1-1

1 Introduction to This Document 1.1 Scope This document describes TC pool of Huawei GBSS. It covers the function of and technologies mechanisms regarding TC pool, including working principle, networking, hardware cabling, hardware management. The document also describes the engineering guidelines to the feature. (GBFD-113726 TC Pool)

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 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 TC pool 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.

GSM BSS TC Pool 1 Introduction to This Document


1-2

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

GSM BSS TC Pool 2 Overview


2-1

2 Overview Huawei GBSS allows other BSCs to connect to the transcoder subracks (TCSs) of a certain BSC so that these BSCs share the TC resources. Thus, the TCSs form a TC pool.

When ServiceMode is set to SEPARATE(Separate), the TC resources exist in the remote TCSs.

In non-TC-pool mode, the TCSs belong to and process the CS services of their respective BSCs. These TCSs are not associated. Thus, the TC resources cannot be shared among multiple BSCs. This leads to inefficient use of the TC resources especially in the scenario where multiple BSCs with small capacity are deployed.

In TC pool mode, one to four TCSs of the primary BSC compose the TC pool. The TC resources in the TC pool can be shared among the primary BSC and the secondary BSCs, which work in loading sharing mode, as shown in Figure 2-1.

The primary BSC performs the configuration and maintenance of the TC resources in a TC pool. It is unique in a TC

pool area. The TCSs that form the TC pool belong to the primary BSC. The secondary BSCs, configured with only the Basic Modules (BMs), share the TC resources in a TC pool with the

primary BSC.

Figure 2-1 Allocation of the TC resources in the TC pool

BSC1

BSC2

BSC3

TC Pool3

1 42

Transmission link between the BSC and the TC PoolTransmission link between the BSC and the BTS

Call speech signals1 TC DSP

The primary BSC and the secondary BSCs are connected to the TC pool over the Ater interface, and the TC pool is connected to the MSC over the A interface. Figure 2-2 shows the typical networking of a TC pool.

GSM BSS TC Pool 2 Overview


2-2

Figure 2-2 Typical networking of a TC pool

TC Pool

MSC2

MSC1

MSC3

AterE1/T1 or Ch-STM-1

AE1/T1 or Ch-STM-1

Primary BSC

Secondary BSC1

Secondary BSC2

1-4 TCSs

The primary BSC performs the configuration and maintenance of the TCSs in the TC pool whereas the secondary BSCs share the TC resources in the TC pool.

The TC Pool feature is subject to the parameter IsSupportTcPool. The feature is applicable only to the BSCs whose ServiceMode is set to SEPARATE(Separate).

The benefits of the TC Pool feature are as follows:

Flexible networking The TC Pool feature supports E1/T1 and Ch-STM-1 transmission modes on the Ater interface. In addition, one Ater interface board can be connected to multiple BSCs in the same transmission mode. Thus, the networking is flexible.

Reduced cost for network deployment The TC Pool feature enables multiple BSCs with small capacity to share the TC resources, thus reducing the cost for network deployment.

High reliability The data processing unit (DPU) boards in the TC Pool work in load sharing mode. In this manner, the impact of the failure of one DPU board on the services is reduced. This makes the network highly reliable.

The DPU board performs the conversion and forwarding of the voice formats and the voice coding/decoding. The GSM TC Data Processing Unit REV:a (DPUa), (DPUb), and (DPUc) boards are collectively referred to as the DPU boards in this document.

GSM BSS TC Pool 3 Technical Description


3-1

3 Technical Description 3.1 Working Principle When a BSC in the TC pool area sends a call request to a TCS, the working principle of the TC pool is as follows:

1. The TC pool allocates an A interface CIC based on SUBBSCTID of the BSC and the A interface timeslots.

The TC pool finds the A interface CIC specified in the connection establishment request message from the A interface CICs of the BSCs specified by SUBBSCTID.

2. The TC pool allocates a TC device for the call based on the load balance algorithm. The TC pool manages all the TC devices in the TCS and monitors the load of each device in real time. When allocating the TC device, the TC pool allocates the device with the lowest load to the call at the TCS where the A interface CICs are located. If all the devices in the TCS operate at the maximum load, the TC pool allocates the TC device in other TCSs to the call.

3. The TC pool selects the Ater transmission channel according to SUBBSCTID of the BSC. The TC pool allocates idle Ater transmission channels to the BSC in the TC pool specified by SUBBSCTID.

4. After the call connection channel (A interface—TC device—Ater interface) is established, the TCS returns a call establishment success message to the BSC.

3.2 Networking The TC Pool feature can adjust the networking mode flexibly based on different physical transmission modes.

The Ater interface, which connects the BSCs to the TC pool, supports the E1/T1 and Ch-STM-1 transmission modes. In addition, it supports the TDM or Ater transmission compression (IP over point-to-point protocol (PPP)) modes on the user plane.

The A interface, which connects the TC pool to the MSC, supports the E1/T1 and Ch-STM-1 transmission modes. The primary BSC and secondary BSCs are connected to the MSC through the TCSs. The resources on the A interface can be carried in TDM mode.

Figure 3-1 shows the TC pool networking when the TDM mode is used on the user plane over the Ater interface. In this scenario, the Ater interface supports the E1/T1 and Ch-STM-1 transmission modes.



3-2

Figure 3-1 TC pool networking (TDM used on the user plane over the Ater interface)

TC Pool

MSC2

MSC1

MSC3

TDM

TDM

TDM


AE1/T1 or Ch-STM-1

PrimaryBSC

SecondaryBSC

BSC1

BSC2

BSC3

1-4TCSs

TDM

TDM

TDM

Figure 3-2 shows the TC pool networking when the IP over PPP mode is used on the user plane over the Ater interface. In this scenario, the Ater interface supports the Ch-STM-1 transmission mode.

Figure 3-2 TC pool networking (IP over PPP used on the user plane over the Ater interface)

TC Pool

MSC2

MSC1

MSC3

TDM

TDM

TDM

AterCh-STM-1

AE1/T1 or Ch-STM-1

PrimaryBSC

Secondary BSC

BSC1

BSC2

BSC3

1-4TCSs

IP over PPP

IP over PPP

IP over PPP

Figure 3-3 shows the TC pool networking when both the TDM and the IP over PPP modes are used on the user plane over the Ater interface. In this scenario, the Ater interface supports the E1/T1 and Ch-STM-1 transmission modes.



3-3

Figure 3-3 TC pool networking (both TDM and IP over PPP used on the user plane over the Ater interface)

TC Pool

MSC2

MSC1

MSC3

TDM

TDM

TDM


AE1/T1 or Ch-STM-1

Primary BSC

Secondary BSC

BSC1

BSC2

BSC3

1-4TCSs

TDM

IP over PPP

IP over PPP

For one BSC, only one transmission mode (TDM or IP over PPP) can be used over the Ater interface.

As shown in Figure 3-4, the timeslots on the Ater interface are as follows:

Speech service timeslot When the TDM mode is used on the user plane over the Ater interface, the speech frames are TRAU frames. When the IP over PPP mode is used on the user plane over the Ater interface, the speech frames are pTRAU frames. Only the speech service timeslots on the Ater interface can be carried in Ater transmission compression mode.

Signaling timeslot The Ater signaling timeslots are carried over the Ater signaling link. The Ater signaling timeslots can be carried only in TDM mode.

OM timeslot The Ater OM timeslots are carried on the OM links between the primary BSC and the TC pool. The Ater OM timeslots can be carried only in TDM mode.

A interface SS7 signaling timeslot The SS7 signaling is transparently transmitted to the Ater interface over the A interface SS7 signaling timeslots through the semipermanent connection.



3-4

Figure 3-4 Timeslots on the Ater interface

TCBM

Ater timeslots

TS for pTRAU over PPP or TRAU over TDM

TS for Ater SL over TDM

TS for Ater OML over TDM (not in Secondary BSC)

TS for A SL over TDM

When the Ater transmission compression mode is used on the user plane over the Ater interface, the BMs of the BSC and the TCSs in the TC pool must be configured as adjacent nodes. For details about the Ater transmission compression mode, see Ater Compression Transmission Parameter Description.

As shown in Figure 3-5, the timeslots on the A interface are as follows:

Speech service timeslot A interface SS7 signaling timeslot The SS7 signaling timeslots are carried on the SS7 signaling link on the A interface. The SS7 signaling is transparently transmitted to the Ater interface over the A interface SS7 signaling timeslots through the semipermanent connection.

Figure 3-5 Timeslots on the A interface

MSCTC

A timeslots

TS for PCM over TDM

TS for A SL over TDM

IsMainBSC and SUBBSCTID determine whether the resources carried over the Ater and A interfaces belong to the primary BSC or a secondary BSC.

SUBBSCTID is required for only the secondary BSC.

3.3 Hardware Cabling In TC pool mode, the user plane of the Ater interfaces of different BSCs can use the TDM or IP over PPP transmission mode. In addition, the Ater interface of the same BSC can use only one transmission mode. Three types of hardware cabling are provided between the BM in the BSC in the TC pool area and the TCS in the TC pool.



3-5

When the Ater interfaces of all the BSCs in the TC pool area use the TDM mode, the cabling between the BMs and the TCSs is shown in Figure 3-6. To improve the network reliability, the BMs can be evenly connected to the TCSs in the TC pool.

Figure 3-6 Cabling between the BM and the TCS (TDM used over the Ater interface)

EPS TCS A intf.Abis intf.

Gb intf.

EPS

MPS

Abis intf.

Gb intf.

Abis intf.

TCS A intf.

MPSAbis intf.

Gb intf.

BSC1(Primary BSC)

BSC3(Secondary BSC)

BSC2(Secondary BSC)

MPSAbis intf.

TC Pool

Ater TDM

When the Ater interfaces of all the BSCs in the TC pool area use the IP over PPP mode, the cabling between the BMs and the TCSs is shown in Figure 3-7. In this case, multiple optical interfaces on the same POUc board in the BM can be connected to the optical interface of the same POUc board in the TCS. The multiple optical interfaces on the same POUc board in the TCS, however, can be connected to multiple BSCs.



3-6

Figure 3-7 Cabling between the BM and the TCS (IP over PPP used over the Ater interface)


Gb intf.

EPS

MPS

Abis intf.

Gb intf.

Abis intf.

TCS A intf.

MPSAbis intf.

Gb intf.

BSC1(Primary BSC)

BSC3(Secondary BSC)

BSC2(Secondary BSC)

MPSAbis intf.

TC Pool

Ater IP over PPP

When the Ater interfaces of some BSCs use the IP over PPP mode whereas those of other BSCs use TDM mode, the cabling between the BMs and the TCSs is shown in Figure 3-8. In the case of the BSC with the Ater interface in IP over PPP mode, multiple optical interfaces on the same POUc board in the BM can be connected to the optical interface of the same POUc board in the TCS. In the case of the BSC with the Ater interface in TDM mode, each BM can be evenly connected to all the TCSs in the TC pool.



3-7

Figure 3-8 Cabling between the BM and the TCS (both the TDM and IP over PPP modes used over the Ater interface)


Gb intf.

EPS

MPS

Abis intf.

Gb intf.

Abis intf.

TCS A intf.

MPSAbis intf.

Gb intf.

BSC1(Primary BSC)

BSC3(Secondary BSC)

BSC2(Secondary BSC)

MPSAbis intf.

Ater IP over PPP

TC Pool

Ater TDM

3.4 Hardware Management Hardware Involved in TC Pool The hardware involved in a TC pool is one to four TCSs of the main BSC.

The boards configured in the TCSs are as follows:

The boards that carry the TC resources are DPUa, DPUb, and DPUc. The A interface boards are EIUa, OIUa, and POUc. Ater interface board The Ater interface boards in TDM mode are EIUa, OIUa, and POUc. The Ater interface board in Ater transmission compression mode is POUc.

The TDM switching network board is TNUa. The GE switching network and control board is SCUa.

The boards that carry the TC resources work in load sharing mode. Therefore, the N+1 redundancy configuration is recommended. This ensures reliability of the network, because the service is not affected even if one board is faulty.

Hardware Management The main BSC performs the configuration and maintenance on the TCSs in the TC pool through the OM link on the Ater interface. The functions are as follows:

Hardware configuration Configuration of the cabinet and boards.



3-8

Status management Management of the TCS status

Alarm management Management of the faults and alarms on the TCS

Operation and maintenance Manual blocking, unblocking and query of the boards in the TCS

The secondary BSCs cannot perform the configuration and maintenance on the TCSs and can only query the usage of the TC resources.

GSM BSS TC Pool 4 Engineering Guidelines


4-1

4 Engineering Guidelines The setting of TCCRCAllowed must be consistent on the primary BSC and the secondary BSCs. The BSCs connected to the same TC pool must share the same clock source. The TC Pool feature applies only to BSCs in BM/TC separated mode. The feature cannot be enabled in BSCs in BM/TC combined mode or in A over IP transmission mode.

The TC Pool feature supports various voice coding schemes, such as FR, EFR, HR, AMR, and WB-AMR.

In TC pool networking mode, E1/T1 (TDM) and STM-1 (TDM) transmission modes are supported over the A interface, and E1/T1 (TDM) and STM-1 (TDM or IP over PPP) transmission modes are supported over the Ater interface.

If the transmission modes are the same on the Ater interface, different E1/T1 ports on an Ater interface board in a TCS can be connected to different BSCs in the TC pool area.

If the transmission modes are the same on the A interface, different E1/T1 ports on an A interface board in a TCS can be connected to different MSCs or MGWs.

In the case of upgrade, the primary BSC must be upgraded first. When the software version of the secondary BSCs is earlier than that of the primary BSC or when the primary BSC is faulty, the TC pool can continue to provide services for the secondary BSCs.

One BSC can be connected to only one TC pool. If IP over PPP is used over the Ater interface, a pair of POUc boards of the BSC can be connected to only a pair of POUc boards of the same TCS.

GSM BSS TC Pool 5 Parameters


5-1

5 Parameters Table 5-1 Parameters Description

Parameter ID NE MML Description

ServiceMode BSC6900 SET BSCBASIC(Optional) Meaning: Service mode of the BSC. This parameter specifies configuration mode of subracks. GUI Value Range: SEPARATE(Separate), TOGETHER(Together) Actual Value Range: SEPARATE, TOGETHER Unit: None Default Value: SEPARATE

IsSupportTcPool BSC6900 SET BSCBASIC(Optional) Meaning: Whether to support the TC pool function. The TC Pool feature is implemented by connecting the main processing subracks (MPSs) and extended processing subracks (EPSs) in multiple BSCs to the transcoder subracks (TCSs) of one BSC. In this manner, all the involved BSCs share the TC resources, and the shared TC resources form a TC Pool. The TC Pool feature is applicable to only the BSCs whose "Service mode " is set to SEPARATE. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

SUBBSCTID BSC6900 ADD AE1T1(Mandatory) Meaning: ID of the BSC in the TC pool to which an A interface E1/T1 is added GUI Value Range: 1~15 Actual Value Range: 1~15 Unit: None Default Value: None



5-2

IsMainBSC BSC6900 SET BSCBASIC(Mandatory)

Meaning: Whether a BSC in the TC pool is the primary BSC GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: None

TCCRCAllowed BSC6900 SET BSCBASIC(Optional) Meaning: This parameter specifies the cyclic redundancy check (CRC) switch, which can be set to On or Off. The value of this parameter determines whether check is performed on the TRAU frame between the BSC and the BTS. GUI Value Range: OFF(Off), ON(On) Actual Value Range: OFF, ON Unit: None Default Value: ON

NBAMRTFOSWITCH

BSC6900 SET GCELLBASICPARA(Optional)

Meaning: Whether to enable the Tandem Free Operation (TFO) function on the BTS through a CHANNEL ACTIVATION or MODE MODIFY message. This parameter specifies whether to enable the Tandem Free Operation (TFO) function. If the voice quality of an ongoing MS-to-MS call is bad, the TFO function can be enabled to improve end-to-end voice quality. The TFO function cannot be used to improve the voice quality of an MS-to-PSTN call. GUI Value Range: DISABLE(Disable), ENABLE(Enable) Actual Value Range: DISABLE, ENABLE Unit: None Default Value: DISABLE



5-3

BTCFLAG BSC6900 ADD ATERE1T1(Mandatory)

Meaning: The configuration flag specifies the operation is on the BM or TC. GUI Value Range: CFGBM(BM), CFGTC(TC) Actual Value Range: CFGBM, CFGTC Unit: None Default Value: None

NODET BSC6900 ADD ADJNODE(Mandatory) MOD ADJNODE(Optional)

Meaning: This parameter indicates the type of the adjacent node. GUI Value Range: ABIS(Abis Interface), A(A Interface), BSC(Ater Interface on BSC), TC(Ater Interface on TC), IUR_G(IUR_G Interface) Actual Value Range: ABIS, A, BSC, TC, IUR_G Unit: None Default Value: None

BSCID BSC6900 ADD ADJNODE(Mandatory)

Meaning: This parameter uniquely identifies a BSC in the TC pool. GUI Value Range: 0~15 Actual Value Range: 0~15 Unit: None Default Value: None

BSCFLAG BSC6900 ADD AE1T1(Mandatory) Meaning: It indicates whether the A interface E1/T1 is the primary BSC or secondary BSC. GUI Value Range: MAINBSC(MAIN BSC), SUBBSC(SUB BSC) Actual Value Range: MAINBSC, SUBBSC Unit: None Default Value: None



5-4

ServiceMode BSC6900 SET BSCBASIC(Optional) Meaning: Service mode of the BSC. This parameter specifies configuration mode of subracks. GUI Value Range: SEPARATE(Separate), TOGETHER(Together) Actual Value Range: SEPARATE, TOGETHER Unit: None Default Value: SEPARATE

GSM BSS TC Pool 6 Counters


6-1

6 Counters For the counters, see the BSC6900 GSM Performance Counter Reference.

GSM BSS TC Pool 7 Glossary


7-1

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

GSM BSS TC Pool 8 Reference Documents


8-1

8 Reference Documents [1] BSC6900 Feature List [2] BSC6900 Optional Feature Description [3] GBSS Reconfiguration Guide [4] BSC6900 GSM Parameter Reference [5] BSC6900 GSM MML Command Reference [6] BSC6900 GSM Performance Counter Reference