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20 EGPRSAbout This Chapter

20.1 Overview

This describes the EGPRS. The Enhanced Data Rate for GSM Evolution (EDGE) can provide

high-rate data services.

20.2 Availability

This lists the NEs, software versions, licenses, and other conditions required for the

implementation of EDGE.

20.3 ImpactThis describes the impact of EGPRS on system performance.

20.4 Technical Description

This describes the technical aspects of EDGE. EDGE is an evolution stage of PS services. It can

be called as 2.75 G mobile communication technology. If the equipment on the current network

remains unchanged, EDGE can be implemented through the upgrade of relevant software. EDGE

can enhance the transmission r ate of PS data.

20.5 Capabilities

This describes the EDGE capabilities of the built-in PCU and external PCU.

20.6 Implementation

EDGE implementation consists of configuring EDGE with the built-in PCU and configuringEDGE with the external PCU.

20.7 Maintenance Information

This lists the alarms and counters related to EDGE.

20.8 References

The references indicate the documents about EDGE from the related standard organizations.

HUAWEI BSC6000 Base Station Subsystem

BSS Feature Description 20 EGPRS

Issue 03 (2009-06-08) Huawei Proprietary and Confidential

Copyright © Huawei Technologies Co., Ltd.

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20.1 Overview

This describes the EGPRS. The Enhanced Data Rate for GSM Evolution (EDGE) can provide

high-rate data services.

Definition

EDGE consists of the Enhanced GPRS (EGPRS) and the Enhanced Circuit Switched Data

(ECSD).

l EGPRS is the enhanced GPRS. EGPRS uses the 8PSK modulation mode so that the rate

of a single channel is improved. The maximum rate of a single channel is 59.2 kbit/s.

l ECSD is the enhanced High Speed Circuit Switched Data (HSCSD).

NOTE

The Huawei BSS supports only EGPRS. Unless otherwise specified, EDGE referred to in this document

indicates EGPRS.

Purposes

Using the new modulation and coding schemes, EDGE greatly improves the data service rates.

The data transmission rates on the Um interface in EDGE are almost three times those in GSM.

This meets the requirements of high-rate data services.

Term

None.

Acronyms and Abbreviations

Acronym andAbbreviation

Full Spelling

EDGE Enhanced Data Rate for GSM Evolution

GPRS General Packet Radio Service

PCIC Packet Circuit Identity Code

BER Bit Error Rate

BVC BSSGP Virtual Connection

BSSGP Base Station System GPRS Protocol

QoS Quality of Service

TBF Temporary Block Flow

CCCH Common Control Channel

PCCCH Packet Common Control Channel

PACCH Packet Associated Control Channel

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Acronym andAbbreviation

Full Spelling

RLC Radio Link Control

20.2 Availability

This lists the NEs, software versions, licenses, and other conditions required for the

implementation of EDGE.

NEs Involved

Table 20-1 lists the network elements (NEs) involved in EDGE.

Table 20-1 NEs Involved in EDGE

MS BTS BSC PCU SGSN GGSN MSC HLR

√ √ √ √ √ √ - √

NOTE

l -: not involved

l √: involved

Software Versions

Table 20-2 lists the versions of GBSS products that support EDGE.

Table 20-2 GBSS products and software versions

Product Version

BSC BSC6000 V900R008C01 and later versions

BTS BTS3X G3BTS32V302R002C05 and later versions

BTS3012A All versions

BTS3001C All versions

BTS3002C All versions

BTS3002E BTS3000V100R002C01 and later versions

BTS3006C BTS3000V100R002C01 and later versions

BTS3012 DTRU BTS3000V100R001C01 and later versions

QTRU BTS3000V100R008C01 and later versions





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Product Version

BTS3012

AE

DTRU BTS3000V100R001C04 and later versions

QTRU BTS3000V100R008C01 and later versions

BTS3900 GSM BTS3000V100R008C02 and later versions

BTS3900A GSM BTS3000V100R008C02 and later versions

DBS3900 GSM BTS3000V100R008C01 and later versions

Miscellaneous

l The EDGE Support can be configured only when the GPRS Support is configured.

l For the concentric cell, the configuration between the overlaid subcell and the underlaidsubcell should be the same; that is, the overlaid subcell and underlaid subcell should be

configured in such as way that they both support EDGE or both do not support EDGE.

20.3 Impact

This describes the impact of EGPRS on system performance.

Impact on System Performance

l When the EDGE function is enabled, the maximum number of TRXs supported by one E1

cable in different network topologies decreases. Thus, the number of TRXs that each GMPS

or GEPS supports decreases.

NOTE

The number of idle timeslots and TRXs that each E1 cable can be configured with must meet the

following requirement: The number of configured TRXs + the number of configured idle timeslots/

8≤ the maximum number of configurable TRXs.

l When the external PCU is used and the EDGE function is enabled, the capacity of each

RPPU in the PCU decreases. The number of PDCHs that can be activated on each RPPU

decreases from 120 to 100.

Impact on Other Features

None.


This describes the technical aspects of EDGE. EDGE is an evolution stage of PS services. It can

be called as 2.75 G mobile communication technology. If the equipment on the current network

remains unchanged, EDGE can be implemented through the upgrade of relevant software. EDGE

can enhance the transmission rate of PS data.

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20.4.1 8PSK Modulation Mode

This describes the 8PSK modulation mode. In 8PSK modulation mode, symbols represent the

absolute phases of signals. There are eight possible symbols and each symbol represents three

bits of information.

The GSM system uses the Gaussian Minimum Shift Keying (GMSK) modulation mode. In

GMSK modulation mode, bit 0 or 1 indicates the change in signal phases. Each phase change

is represented by a symbol.

In 8PSK modulation mode, symbols represent the absolute phases of signals. There are eight

possible symbols and each symbol represents three bits of information. Therefore, the data rate

on the Um interface in EDGE can theoretically be three times that in GSM.

Figure 20-1 shows the I/Q relations for the modulation and demodulation in GSM and EDGE.

Figure 20-1 I/Q relations for the modulation and demodulation in GSM and EDGE

GPRS:

GMSK modulation

EGPRS:

8PSK modulation

1

0

Q

I

Q

I

(0,1,0)

(0,0,0)

(0,0,1)

(1,0,1)

(1,0,0)

(1,1,0)

(1,1,1)

(0,1,1)

NOTE

In terms of performance, the 8PSK modulation mode is better than the GMSK modulation mode. The

demodulation threshold of the 8PSK mode, however, is higher than the demodulation threshold of theGMSK mode. The modulation mode is radio environment specific. The PCU automatically adjusts the

modulation mode based on the BER report from an MS. Therefore, the modulation and demodulation mode

that EDGE uses can be 8PSK or GMSK.

Table 20-3 lists the modulation bits and corresponding symbols shown in Figure 20-1.

Table 20-3 Modulation bits and corresponding symbols

Modulation Bit Symbol

(1,1,1) 0

(0,1,1) 1





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Modulation Bit Symbol

(0,1,0) 2

(0,0,0) 3

(0,0,1) 4

(1,0,1) 5

(1,0,0) 6

(1,1,0) 7

NOTE

Table 20-3 lists all the modulation bits and corresponding symbols.

20.4.2 EGPRS Transmit Power

This describes the transmit power of a BTS that uses 8PSK modulation mode.

From the perspective of network operation, the transceiver of the BTS in EDGE must have the

same spectrum features as those of an ordinary transceiver. When sending the signals modulated

in 8PSK modulation mode, the transceiver of the BTS in EDGE uses the transmit power that is

2 dB–5 dB less than the average power in GMSK modulation mode. Thus, the requirements for

spectrum can be met. In the system, the cell parameter 8PSK power attenuation grade and the

trx parameter TRX 8PSK Level can be specified to meet the requirements.

On the BCCH, the transmit power of the signals modulated in 8PSK modulation mode is at most

4 dB less than the average transmit power of the signals modulated in GMSK modulation mode.

On the timeslot located before the timeslot of the BCCH/CCCH, the transmit power of the signals

modulated in 8PSK mode is at most 2 dB less than that of the signals modulated in GMSK

modulation mode.

20.4.3 MCS-1 to MCS-9 Coding Schemes

This describes MCS-1 to MCS-9 modulation and coding schemes used in EDGE.

EDGE uses MCS-1 to MCS-9 modulation and coding schemes, as listed in Table 20-4.

Table 20-4 Modulation and coding schemes in EDGE

Coding Scheme Modulation Mode Number of Bitsin the Payload ofEach Burst

Rate (kbit/s)

MCS-9 8PSK 2 x 592 59.2

MCS-8 2 x 544 54.4

MCS-7 2 x 448 44.8

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Coding Scheme Modulation Mode Number of Bitsin the Payload ofEach Burst

Rate (kbit/s)

MCS-6 592

544 + 48

29.6

27.2

MCS-5 448 22.4

MCS-4 GMSK 352 17.6

MCS-3 296

272 + 24

14.8

13.6

MCS-2 224 11.2

MCS-1 176 8.8

NOTE

For 544 + 48 and 272 + 24 in the previous table, 544 and 272 indicate the significant bits, and 48 and 24

indicate the padding bits.

The initial coding schemes used in EDGE can be specified through the parameters Uplink

Default MCS Type and Downlink Default MCS Type. When the EDGE service is used,

whether the uplink/downlink is adjusted based on the signal transmission quality depends on the

setting of the parameters Uplink Fixed MCS Type and Downlink Fixed MCS Type.

Figure 20-2 shows the rates of GPRS channels and those of EDGE channels.

Figure 20-2 Rates of GPRS channels and those of EDGE channels

kbit/s60.0

50.0

40.0

30.0

20.0

10.0

0.0CS-1 CS-2 CS-3 CS-4 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9

8.0

12.214.4

20.2

8.811.2

14.8 17.6

22.4

29.6

44.8

54.4

59.2

GPRS

EDGE

GMSK

modulation

8PSK

modulation





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20.4.4 Link Quality Control

This describes the link quality control. The link quality control enables the system to adapt to

the radio transmission environment dynamically by changing modulation and coding schemes

during data transmission, thus improving the link quality.

EDGE uses a set of high-efficient link quality control algorithm. EDGE has two link quality

control modes: Link Adaptation (LA) and Incremental Redundancy (IR). The link quality control

mode is set through the parameter Link Quality Control Mode. For the cells where the signal

quality on the Um interface is good, this parameter is set to LA.

Basic Principle of LA

During data transmission, the sender retransmits the original data block or segments the original

data block into two data blocks and then transmits them. The receiver need not restore the

previous erroneous data blocks.

Basic Principle of IR

During data transmission, the sender does not consider the radio transmission environment at

first and uses a high data rate coding scheme for the data transmission. Although the data rate

is high, the capability of data protection is weak. If the data is received incorrectly, the sender

retransmits additional coding information. The receiver combines the new information with the

previous information and then performs decoding. The previous process is repeated until the

decoding succeeds.

l During uplink data transmission, the system notifies an MS to use the IR mode by setting

RESEGMENT in the uplink resource assignment message to 0 (segmentation forbidden).

In IR mode, the receiver should have sufficient memory to save the history information. If

the network memory is insufficient, the system can notify the MS of the memory

insufficiency by setting RESEGMENT in the UPLINK ACK/NACK message to 1.

l During downlink data transmission, if the memory of an MS is insufficient, the MS can

send MS OUT OF MEMORY to the network through a DOWNLINK ACK/NACK

message. Then, the network cannot use the IR mode in downlink data transmission.

20.4.5 Types of Preferred EGPRS Channels

This describes the types of preferred channels in EGPRS.

The preferred channel types are as follows:

l EGPRS dedicated channel

EGPRS dedicated channels can be used by only EGPRS MSs.

l EGPRS preferred channel

EGPRS preferred channels are preferentially used by EGPRS MSs. The EGPRS preferred

channels can be used by GPRS MSs when the channels are in the idle state. When an EGPRS

MS requests an EGPRS preferred channel, the GPRS MS that occupies the EGPRS

preferred channel should be transferred to other channels. The signals of an EGPRS MS

and those of a GPRS MS cannot be multiplexed onto one EGPRS preferred channel.

l Normal EGPRS channel

Normal EGPRS channels can be used by GPRS MSs and EGPRS MSs.

l GPRS channel

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GPRS channels are used by GPRS MSs. If a cell is not configured with EGPRS channels,

EGPRS MSs in the cell preferentially use GPRS channels to process GPRS services.

l Non-GPRS channel

Non-GPRS channels are not used for packet services.

When configuring Channel Type on the TRX, you can select the channel type through GPRS

Channel Priority Type.

When the system allocates PDCHs, the preferred channel type varies according to packet data

services.

l For the GPRS service, the GPRS channels are preferentially assigned. Then the normal

EGPRS channels are assigned and finally the EGPRS preferred channels are assigned.

l For the EGPRS service, the EGPRS dedicated channels are preferentially assigned. Then

the EGPRS preferred channels are assigned and finally the normal EGPRS channels are

assigned.

On the normal EGPRS channel, the GPRS MS may use the uplink channel, and the EGPRS MS

may use the downlink channel. The parameter Allow E Down G Up Switch can be set to avoid

channel multiplexing. If you want to eliminate the possibility of EDGE/GPRS co-timeslot, do

not configure normal EGPRS channels.

NOTE

Channels should be selected according to the preferred channel type. For example, if the channels on the

TRX that supports EGPRS are configured as GPRS channels, these channels can be used for only GPRS

services. EGPRS dedicated channels can be configured only as static channels. Other three types of

preferred channels can be configured as static or dynamic channels.

20.4.6 CCCH 11Bit EGPRS Access

EDGE supports 11Bit EGPRS access on the CCCH. EDGE reduces the access delay and

improves the access performance of the MS.

The access process of the 11Bit EGPRS on the CCCH is as follows:

1. The MS sends the 11bit EGPRS PAKCET CHANNEL REQUEST message on the CCCH

for one phase packet access.

2. The network assigns the EDGE channel for the MS through the IMMEDIATE

ASSIGNMENT message. Therefore, the EGPRS TBF is established.

Whether to enable CCCH 11Bit EGPRS access depends on the setting of the parameter Support

11BIT EGPRS Access.

20.4.7 Assignment of Idle Timeslots

For packet data services, the Abis interface supports the mapping of several timeslots to one

traffic channel. Then, the timeslots are divided and combined on the TX and RX ends.

The data rate of each timeslot on the Abis interface is 16 kbit/s. In EDGE, the data rate can be

59.2 kbit/s. In GPRS, the CS-3/CS-4 coding scheme needs to be added with a subtimeslot. In

EDGE, each PDCH can be added with three subtimeslots. EDGE coding schemes are MCS1 to

MCS9. The number of Abis links required for different coding schemes is different, as describedin Table 20-5.





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Table 20-5 Coding schemes and number of required Abis links

Coding Scheme Number of Required Abis Links

MCS-1–MCS-2 1

MCS-3–MCS-6 2

MCS-7 3

MCS-8–MCS-9 4

The number of idle timeslots on the Abis interface requested during EDGE coding scheme

adjustment is related to the coding scheme. As described in Table 20-5, when EDGE uses coding

schemes MCS-3-MCS-6, an idle timeslot on the Abis interface is required. The idle timeslots

on the Abis interface in the same BTS can be allocated to any PDCH on any TRX in the same

cabinet group. The idle timeslot on the Abis interface is set through the parameter Idle

Timeslots.

NOTE

l When the Abis interface uses IP or HDLC transmission, there is no idle timeslot configuration.

l When the Flex Abis feature of the BTS is enabled, if the CS traffic is light, idle timeslots may not be

configured and the EDGE service can still run normally.

l When the Flex Abis feature of the BTS is enabled, if the CS traffic is heavy, idle timeslots should be

configured. Otherwise, the EDGE service may fail for a long time.

20.5 Capabilities

This describes the EDGE capabilities of the built-in PCU and external PCU.

Built-in PCU

The EDGE capabilities of the built-in PCU are as follows:

l The system uses the resource pool redundancy configuration mode. The maximum

configuration that the system can support is 8 + 1 = 9 GDPUPs.

l The maximum number of cells supported by each GDPUP is 1,024.

l The maximum number of activated PDCHs supported by each GDPUP is 1,024. All the

channels support the MCS9 coding scheme.

l The maximum number of configurable PDCHs is 15,360.

l The maximum number of activated PDCHs in full configuration is 8,192. All the channels

support the MCS9 coding scheme.

l The maximum throughput on the Gb interface is 512 Mbit/s.

l The maximum number of uplink PDCHs that can be used by a single MS is 4.

l The maximum number of downlink PDCHs that can be used by a single MS is 5.

l The maximum number of pairs of configured GFGUGs/GEPUGs are 8.

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External PCU

The EDGE capabilities of the external PCU are as follows:

l The BSC supports 256 E1 lines on the Pb interface.

l Each GMPS/GEPS subrack supports 64 E1 lines on the Pb interface.

l Each GEIUP/GOIUP supports 32 E1 lines on the Pb interface.

l The GOIUP provides one STM-1 port, which carries 63 E1 links.

20.6 Implementation

EDGE implementation consists of configuring EDGE with the built-in PCU and configuring

EDGE with the external PCU.

20.6.1 Configuring EGPRS (with Built-in PCU)This describes how to configure EDGE on the BSC6000 Local Maintenance Terminal.

Prerequisite

l The system is configured to support GPRS. For details about how to configure GPRS with

the built-in PCU, see 19.6.5 Configuring GPRS (with External PCU).

l The subrack-OSP mapping is configured. For details, refer to Configuring the Subrack-

OSP Mapping.

l The license is applied and activated. To apply for and activate the license, do as follows:

1. In the BSC6000V900R008 Exceptional Commercial License Application Template,fill in the following information.

– Fill in the number of PDCHs to be purchased in the Number of resources column

corresponding to the Maximum Number of PDCH Groups Activated in the

Resource control items column.

– Fill in the number of TRXs to be purchased in the Number of resources column

corresponding to the Number of the TRX Supporting EDGE in the Resource

control items column.

2. Activate the license on the Local Maintenance Terminal. For details, refer to

Activating the BSC License.

Procedure

Step 1 Configure site idle timeslot.

1. On the Management Tree tab page of the BSC6000 Local Maintenance Terminal, right-

click the target BTS, and then choose Configure Site Idle Timeslot from the shortcut

menu. A dialog box is displayed, as shown in Figure 20-3.





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Figure 20-3 Configure Site Idle Timeslot dialog box

2. In the Idle Timeslot area, click the box under the Idle Timeslots area, and then enter the

number of idle timeslots to be configured.

3. Click Finish to end the configuration.

NOTE

l Idle Timeslots should be configured only when TransType of the BSC is set to TDM.

l When the Flex Abis feature of the BTS is enabled, if the CS traffic is light, idle timeslots may not be

configured and the EDGE service can still run normally.

l When the Flex Abis feature of the BTS is enabled, if the CS traffic is heavy, idle timeslots should be

configured. Otherwise, the EDGE service may fail for a long time.

Step 2 Configure the cell to support EDGE.

1. On the BSC6000 Local Maintenance Terminal, right-click a cell on the Management

Tree tab page, and then choose Set Cell Attributes from the shortcut menu.

2. In the displayed dialog box, double-click the target cell in the Cell view list box to add it

to the Selected cells list box. Then, click Next.

3. In the Cells to be set list box, select the target cell, and then click Set Cell Attributes. A

dialog box is displayed, as shown in Figure 20-4.

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Figure 20-4 Set Other Parameter dialog box

4. Select EDGE Support.

5. Click OK to end the configuration.

Step 3 Configure the channel type.

1. On the BSC6000 Local Maintenance Terminal, right-click a TRX on the Management

Tree tab page, and then choose Configure TRX Attributes from the shortcut menu.

2. In the displayed dialog box, select the target TRX in the TRX view list box, and then click

Configure TRX Attributes.

3. In the displayed dialog box, click the Channel Attributes tab, as shown in Figure 20-5.





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Figure 20-5 Channel Attributes tab page

4. Select Channel No., and then select the channel type that supports packet services such asPDTCH or TCH Full Rate in the Channel Type drop-down list box. Then, set GPRS

Channel Priority Type.


----End

20.6.2 Configuring EGPRS (with External PCU)

This describes how to configure EDGE on the BSC6000 Local Maintenance Terminal.

Prerequisitel The system is configured to support GPRS. For details about how to configure GPRS with

the external PCU, refer to 19.6.5 Configuring GPRS (with External PCU).

l The subrack-OSP mapping is configured. For details, refer to Configuring the Subrack-

OSP Mapping.

l The license is applied and activated. To apply for and activate the license, do as follows:

1. In the BSC6000V900R008 Exceptional Commercial License Application Template,

fill in the following information.

– Fill in the number of PDCHs to be purchased in the Number of resources column

corresponding to the Maximum Number of PDCH Groups Activated in theResource control items column.

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– Fill in the number of TRXs to be purchased in the Number of resources column

corresponding to the Number of the TRX Supporting EDGE in the Resource

control items column.

2. Activate the license on the Local Maintenance Terminal. For details, refer to

Activating the BSC License.

Procedure

Step 1 Configure Site Idle Timeslot dialog box


click the target BTS, and then choose Configure Site Idle Timeslot from the shortcut

menu. A dialog box is displayed, as shown in Figure 20-6.

Figure 20-6 Configure Site Idle Timeslot dialog box

2. In the Idle Timeslot area, click the box under the Idle Timeslots area, and then enter the

number of idle timeslots to be configured.

3. Click Finish to end the configuration.

NOTE

l Idle Timeslots should be configured only when TransType of the BSC is set to TDM.

l When the Flex Abis feature of the BTS is enabled, idle timeslots may not be configured and the EDGE

service can still run normally,if the CS traffic is light.

l When the Flex Abis feature of the BTS is enabled, idle timeslots should be configured. Otherwise, the

EDGE service may fail for a long time,if the CS traffic is heavy.

Step 2 Configure the cell to support EDGE.





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1. On the BSC6000 Local Maintenance Terminal, right-click a cell on the Management

Tree tab page, and then choose Configure Cell Attributes from the shortcut menu.

2. In the displayed dialog box, double-click the target cell in the Cell view list box to add it

to the Selected cells list box. Then, click Next.

3. In the Cells to be set list box, select the target cell, and then click Set Cell Attributes. Adialog box is displayed, as shown in Figure 20-7.

Figure 20-7 Set Other Parameter dialog box

4. Select EDGE Support.


Step 3 Configure the channel type.

1. On the BSC6000 Local Maintenance Terminal, right-click a TRX on the ManagementTree tab page, and then choose Configure TRX Attributes from the shortcut menu.

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2. In the displayed dialog box, select the target TRX in the TRX view list box, and then click

Configure TRX Attributes.

3. In the displayed dialog box, click the Channel Attributes tab, as shown in Figure 20-8.

Figure 20-8 Channel Attributes tab page

4. Select Channel No., and then select PDTCH or Dynamic PDCH in the Channel Type

drop-down list box. Then, set GPRS Channel Priority Type.


----End

20.7 Maintenance InformationThis lists the alarms and counters related to EDGE.

Alarms

The alarms related to EDGE consist of alarms related to the built-in PCU and alarms related to

the external PCU, as listed in Table 20-6 and Table 20-7.





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Table 20-6 Alarms related to the built-in PCU

Alarm ID Alarm Name

291 Cell Transmission Delay Abnormal

293 GB BC Faulty

294 TRX Config Error

331 NSVC Faulty

332 NSVL Faulty

333 NSE Faulty

340 Cell PS Service Faulty

341 DSP Resource Overload

342 PTP BVC Faulty

343 NSVL Dynamic Configuration Process Failure

344 FAULTY DSP OVER LIMIT

Table 20-7 Alarms related to the external PCU

Alarm ID Alarm Name

104 All PBSLs in the PCU Are Faulty

128 No Circuit Configured in the PCU

Counters

The counters related to EDGE consist of counters related to the built-in PCU and counters related

to the external PCU, as listed in Table 20-8 and Table 20-9.

Table 20-8 Counters related to the built-in PCU

Counter Description

A331 Delivered Paging Messages for PS Service

ZTA308H Immediate Assignment Requests per BSC (PS

Service)

A031 SGSN-Initiated Paging Requests for PS

Service

L3188D PACKET CCCH LOAD IND Messages Sent

on Abis Interface

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Counter Description

A9201 Number of Uplink EGPRS TBF

Establishment Attempts

A9202 Number of Successful Uplink EGPRS TBFEstablishments

A9203 Number of Failed Uplink EGPRS TBF

Establishments due to No Channel

A9204 Number of Failed Uplink EGPRS TBF

Establishments due to MS No Response

A9205 Number of Uplink EGPRS TBF Normal

Releases

A9206 Number of Uplink EGPRS TBF Abnormal

Releases due to N3101 Overflow (MS NoResponse)


Releases due to N3103 Overflow (MS No

Response)


Releases due to SUSPEND


Releases due to FLUSH

A9210 Number of Uplink EGPRS TBF AbnormalReleases due to No Channel

A9211 Total Number of Sampled Concurrent Uplink

EGPRS TBFs

A9212 Sampling Times of Concurrent Uplink

EGPRS TBFs

AA9213 Average Number of Concurrent Uplink

EGPRS TBFs

A9214 Total Duration of Uplink EGPRS TBF (ms)

AA9215 Average Duration of Uplink EGPRS TBF (s)

A9301 Number of Downlink EGPRS TBF

Establishment Attempts

A9302 Number of Successful Downlink EGPRS

TBF Establishments

A9303 Number of Failed Downlink EGPRS TBF

Establishments due to No Channel

A9304 Number of Failed Downlink EGPRS TBF

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Counter Description

A9305 Number of Downlink EGPRS TBF Normal

Releases

A9306 Number of Downlink EGPRS TBF AbnormalReleases due to N3105 Overflow

A9307 Number of Downlink EGPRS TBF Abnormal

Releases due to SUSPEND


Releases due to FLUSH


Releases due to No Channel

A9310 Total Number of Sampled Concurrent

Downlink EGPRS TBFs

A9311 Sampling Times of Concurrent Downlink

EGPRS TBFs

AA9312 Average Number of Concurrent Downlink

EGPRS TBFs

A9313 Total Duration of Downlink EGPRS TBF

(ms)

AA9314 Average Duration of Downlink EGPRS TBF

(s)

L9201 Total Number of Uplink EGPRS RLC Data

Blocks

L9202 Total Number of Uplink EGPRS MCS1 RLC

Data Blocks


Data Blocks


Data Blocks

L9205 Total Number of Uplink EGPRS MCS4 RLCData Blocks


Data Blocks


Data Blocks


Data Blocks


Data Blocks

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Counter Description


Data Blocks

L9211 Total Number of Valid Uplink EGPRS MCS1RLC Data Blocks

L9212 Total Number of Valid Uplink EGPRS MCS2

RLC Data Blocks


RLC Data Blocks


RLC Data Blocks


RLC Data Blocks


RLC Data Blocks


RLC Data Blocks


RLC Data Blocks


RLC Data Blocks

RL9220 Retransmission Rate of Uplink EGPRS

MCS1 RLC Data Block (%)







RL9224 Retransmission Rate of Uplink EGPRSMCS5 RLC Data Block (%)













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Counter Description

L9229 Number of MCS Upgrades on Uplink EGPRS

TBF

L9230 Number of MCS Degrades on Uplink EGPRSTBF

L9231 Number of Uplink EGPRS RLC Control

Blocks

TL9232 Average Throughput of Uplink EGPRS RLC

(kbit/s)

TL9233 Average Payload of Single Uplink EGPRS

TBF (KB)

L9234 Total Number of Uplink EGPRS TBFs

L9301 Total Number of Downlink EGPRS RLC

Data Blocks

L9302 Total Number of Downlink EGPRS MCS1

RLC Data Blocks


RLC Data Blocks


RLC Data Blocks

L9305 Total Number of Downlink EGPRS MCS4RLC Data Blocks


RLC Data Blocks


RLC data blocks


RLC Data Blocks


RLC Data Blocks


RLC Data Blocks

L9311 Total Number of Valid Downlink EGPRS

MCS1 RLC Data Blocks





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Counter Description



L9315 Total Number of Valid Downlink EGPRSMCS5 RLC Data Blocks









RL9320 Retransmission Rate of Downlink EGPRS

MCS1 RLC Data Blocks (%)















RL9328 Retransmission Rate of Downlink EGPRSMCS9 RLC Data Blocks (%)

L9329 Number of MCS Upgrades on Downlink

EGPRS TBF

L9330 Number of MCS Degrades on Downlink

EGPRS TBF

L9331 Number of Downlink EGPRS RLC Control

Blocks

L9332 Number of Downlink EGPRS RLC Dummy

Blocks





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Counter Description

TL9333 Average Throughput of Downlink EGPRS

RLC (kbit/s)

TL9334 Average Payload of Single Downlink EGPRSTBF (KB)

L9335 Total Number of Downlink EGPRS TBFs

S9101 Number of Times 8PSK_MEAN_BEP=1




S9105 Number of Times 8PSK_MEAN_BEP=5S9106 Number of Times 8PSK_MEAN_BEP=6





















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Counter Description







Table 20-9 Counters related to the external PCU

Counter Description

AR3015A Mean Number of Dynamically Configured

Channels (EDGE) (900/850 Cell)

AR3015B Mean Number of Dynamically Configured

Channels (EDGE) (1800/1900 Cell)

CR3015 Mean Number of Dynamically Configured

Channels (EDGE)

AR3025A Mean Number of Available Channels

(EDGE) (900/850 Cell)

AR3025B Mean Number of Available Channels

(EDGE) (1800/1900 Cell)

CR3025 Mean Number of Available Channels

(EDGE)

R3005A Number of Initially Configured Channels

(Static EDGE) (900/850 Cell)

R3005B Number of Initially Configured Channels

(Static EDGE) (1800/1900 Cell)

R3006A Number of Initially Configured Channels(Dynamic EDGE) (900/850 Cell)


(Dynamic EDGE) (1800/1900 Cell)

CR3005 Number of Initially Configured Channels

(Static EDGE)


(Dynamic EDGE)

AL8351 Mean Number of Faulty Circuits on the Pb

Interface





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Counter Description

AL8353 Mean Number of Blocked Circuits on the Pb

Interface

AL8354 Mean Number of Idle Circuits on the PbInterface

AL8355 Mean Number of Busy Circuits on the Pb

Interface

AL8352 Mean Number of Circuits in Maintenance

State on the Pb Interface

L0387 Total Number of Messages Received from

PCU

L8387 Messages Received from a PCU

R3140 Requests for TCH from the PCU

R3141 Successful Requests for TCH from the PCU

AR3011A Mean Number of Dynamically Configured

Channels (PDCH) (900/850 Cell)

AR3011B Mean Number of Dynamically Configured

Channels (PDCH) (1800/1900 Cell)

CR3011 Mean Number of Dynamically Configured

Channels (PDCH)

AR3021A Mean Number of Available Channels

(PDCH) (900/850 Cell)

AR3021B Mean Number of Available Channels

(PDCH) (1800/1900 Cell)

CR3021 Mean Number of Available Channels

(PDCH)


(Static PDCH) (900/850 Cell)


(Static PDCH) (1800/1900 Cell)


(Dynamic PDCH) (900/850 Cell)


(Dynamic PDCH) (1800/1900 Cell)


(Static PDCH)


(Dynamic PDCH)

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Counter Description

ZTA331 Paging Requests on the Abis Interface per

BSC (PS Service)

ZTA301H Immediate Assignment Commands per BSC(PS Service)

ZTL3188D PCH Overloads due to PS Service Counted

through the Indications from the Abis

Interface per BSC

20.8 References

The references indicate the documents about EDGE from the related standard organizations.

The references are as follows:

3GPP TS 50.059

"Enhanced Data rates for GSM Evolution (EDGE); Project scheduling and open issues for

EDGE"





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21 Co-BCCH CellAbout This Chapter

21.1 Overview

This describes the definition and purposes of the Co-BCCH cell. The Co-BCCH cell adopts the

dual-band technique and features expanded cell capacity and minimized handover occurrences.

21.2 Availability

This lists the NEs, software, and hardware configuration of the BTS required for the

implementation of the Co-BCCH cell.

21.3 ImpactThis describes the impact of the Co-BCCH cell on system performance.


This describes the implementation of channel assignment and handover.

21.5 Capabilities

None.

21.6 Implementation

This describes the configuration principle, configuration preparation, scenario analysis,

configuration procedure, and deactivation of the Co-BCCH cell.

21.7 Maintenance InformationThis lists the performance counters related to the Co-BCCH cell.

21.8 References


BSS Feature Description 21 Co-BCCH Cell



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21.1 Overview

This describes the definition and purposes of the Co-BCCH cell. The Co-BCCH cell adopts the

dual-band technique and features expanded cell capacity and minimized handover occurrences.

Definition

The Co-BCCH cell refers to a cell where the GSM900&DCS1800 TRXs coexist (or

GSM850&DCS1800, GSM850&PCS1900). The TRXs on the two bands use one main BCCH.

In a dual-band network, a dual-band MS can work on either of the bands. A single-band MS can

also work normally on its band.

The GSM900 band consists of the P-GSM, E-GSM, and R-GSM.

PurposesThe Co-BCCH cell improves the continuous coverage and sparse coverage in hot spots.

With the rapid increase of mobile users, the dual-band network solution becomes a growing

trend around the globe. The dual-band network has the following three networking modes:

l Independent MSC Networking

l Co-MSC Independent BSC Networking

l Co-BSC Networking

The highlight of the dual-band network with the Co-BCCH cell is that the primary frequency

band and the secondary frequency band are the same and they coexist in one cell. The secondary

frequency band is the extension of the primary frequency band. This feature eliminates the

technical bottleneck on cell reselection and handover in other networking modes. Specifically,

the advantages of the dual-band network with the Co-BCCH cell are listed as follows:

l The capacity of the cell is expanded and the occurrences of cell reselection for the MS are

reduced.

For example, a site is configured with a GSM900 cell and a DCS1800 cell. Each cell is

configured with two TRXs. You can obtain the data as listed in Table 21-1 when querying

the ERLANG B.

Table 21-1 Data in ERLANG B

Networking Mode

QuantityofBCCHs

QuantityofSDCCHs

Quantityof TCHs

Call LossRate

Traffic Volume

Common

dual-band

network

2 2 28 2% 16.40 ERL

Dual-band

network

with Co-

BCCH

cell

1 2 29 2% 21.04 ERL

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l The inter-cell handover occurrences are reduced.

When an MS initiates a handover request, the MS is handed over to the channels on the

other frequency band in the serving cell.

l The number of the BCCH TRXs is reduced and the interference caused by the BCCH TRXs

is reduced.

l Convenient maintenance

The number of cells and neighboring cells of the Co-BCCH cell network is less than that

of the common dual-band network. Thus, the maintenance workload is reduced.

The system assigns channels on different frequency bands to the MS based on the RX level, RX

quality and TA value. The underlaid subcell is used for cell coverage and the overlaid subcell

is used for traffic absorption. Thus, the cell coverage is maximized and the capacity balance

between the overlaid subcell and the underlaid subcell is maintained.

Terms

Terms Definition

M criteria Indicates a criteria that selects only the neighbor cells of which the

RX level is higher than the lowest MS RX level threshold and sorts

the qualified cells in the candidate cell list. The serving cell and

neighbor cells are sorted based on the RX level.

ERLANG B Indicates the relation among the number of common channels, call

loss rate, and traffic volume in busy hours. The ERLANG B is

developed from the ERLANG call loss formula.

Primary frequency

band

Indicates the frequency band containing the main BCCH frequency

in a Co-BCCH cell.

Secondary frequency

band

Indicates the frequency band that does not contain the main BCCH

frequency in a Co-BCCH cell.

Acronyms and Abbreviations

Acronyms and Abbreviations Full Spelling

BCCH Broadcast Control Channel

SDCCH Stand-alone Dedicated Control Channel

PBGT Power Budget

BQ Bad Quality

MR Measurement Report

TA Timing Advance





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21.2 Availability

This lists the NEs, software, and hardware configuration of the BTS required for the

implementation of the Co-BCCH cell.

NEs Involved

Table 21-2 lists the network elements involved in the Co-BCCH cell.

Table 21-2 NEs involved in Co-BCCH cell

MS BTS BSC MSC MGW SGSN GGSN HLR

- √ √ - - - - -

NOTE

l -: not involved

l √: involved

Software Releases

Table 21-3 lists the NEs and software versions that support Co-BCCH cell.

Table 21-3 GBSS products and software versions

Product Version

BSC BSC6000 V900R008C01 and later releases

BTS BTS3012 DTRU BTS3000V100R001C01 and later releases

QTRU BTS3000V100R008C01 and later releases

BTS3012 DTRU BTS3000V100R001C04 and later releases

QTRU BTS3000V100R008C01 and later releases

BTS3006C BTS3000V100R002C01 and later releases

BTS3002E BTS3000V100R008C01 and later releases

DBS3900 GSM BTS3000V100R008C01 and later releases

BTS3900 GSM BTS3000V100R008C02 and later releases

BTS3900A GSM BTS3000V100R008C02 and later releases

BTS2X All releases

BTS3001C All releases

BTS3002C All releases

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Product Version

BTS3X All releases

Double-transceiver BTSs All releases

Miscellaneous

The BTS must meet the following requirements if you configure Co-BCCH.

l Number of TRXs

The number of GSM900 TRXs or DCS1800 TRXs should be less than or equal to four in

a Co-BCCH cell. If the number exceeds four, enough antenna output ports and antenna

models are required. The coverage of the TRXs on the same frequency band should be the

same in the case of antenna installation.

l Antenna types and azimuth

– If the GSM900 TRX and the DCS1800 TRX use the same antenna, the dual-band

antenna is required.

– If the GSM900 TRX and the DCS1800 TRX use the antenna respectively, either the

dual-band antenna or the single-band antenna is allowed. When the sing-band antenna

is used, the azimuth of the antennas used for the GSM900 TRX and the DCS1800 TRX

in the same cell must be the same.

l Type of the combiner

As a combiner cannot support the GSM900 and the DCS1800 at the same time, the GSM900

TRX and the DCS1800 TRX must use different combiners.

l Combination mode

The combination mode of the TRXs on the same frequency band in a cell must be the same.

Otherwise, the TX power levels of the TRXs on the same frequency band in a cell are not

consistent, and the coverage of these TRXs is not consistent. Thus, the Co-BCCH cell

cannot be enabled because of a 3-layer or more-layer concentric cell.

21.3 Impact

This describes the impact of the Co-BCCH cell on system performance.

Impact on System Performance

The impact of the Co-BCCH cell on system performance is as follows:

l Co-BCCH cell can be applied to specific scenarios only. If Co-BCCH is applied to

unqualified scenarios, the network KPI is deteriorated.

For details of the application scenarios of the Co-BCCH, refer to 21.6.3 Risk Analysis of

the Configuration Scenarios.

l The neighboring cell of the Co-BCCH cell is limited.

The neighboring cell of the Co-BCCH cell cannot be GSM900 cell or DCS1800 cell.Otherwise, the traffic volume is unbalanced.





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NOTE

If the GSM900 cell and the DCS1800 cell are at the same layer, they can be neighboring cell of the

Co-BCCH cell.

For details of network layer and network hierarchy, refer to 7.3.2.10 Fast-Moving Micro Cell

Handover.

l The configuration of network optimization parameters of the Co-BCCH cell is more

difficult than that of the common cell.

Impact on Other Features

The Co-BCCH cell and the double-timeslot cell cannot coexist.


This describes the implementation of channel assignment and handover.

21.4.1 GSM900/DSC1800 Co-BCCH Cell Channel Assignment

This describes the Co-BCCH cell channel assignment. Channel assignment strategy of the Co-

BCCH cell complies with the channel assignment algorithm of the concentric cell and is

associated with the frequency band supported by the MS.

The GSM900&DCS1800 (or GSM850&DCS1800, GSM850&PCS1900) Co-BCCH cell is

realized based on the principles of the concentric cell, which are described as follows:

l GSM900 (or GSM850) TRXs are configured in the underlaid subcell for network coverage.

l DCS1800 (or PCS1900) TRXs are configured in the overlaid subcell for traffic absorption.

Therefore, the channel assignment of the Co-BCCH cell should comply with the channel

assignment strategy of the concentric cell. Before the channel assignment, however, the network

needs to determine the frequency bands supported by the MS. If the MS supports the bands in

the underlaid and overlaid subcell, the channel assignment strategy of the concentric cell is

applied. Otherwise, the network assigns only the channels in the underlaid subcell to the MS.

Immediate Assignment

In the immediate assignment procedure, the BSC does not receive any information about the

MS. If TA exists, the BSC assigns underlaid or overlaid channels to the MS based on TA. The

BSC preferentially assigns the channels in the underlaid subcell to the MS to ensure that theconversation can be established.

Assignment

In the assignment procedure, the channel assignment is related to MS classmark 3.

l If the BSC does not obtain MS classmark 3, or if MS classmark 3 indicates that the MS

supports only the underlaid frequency band, then the BSC assigns only the underlaid

channels to the MS.

l If MS classmark 3 indicates that the MS supports the underlaid and overlaid frequency

bands, the BSC assigns underlaid or overlaid channels to the MS based on AssignOptimum Layer and Assign-optimum-level Threshold.

21 Co-BCCH Cell





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Incoming Internal Inter-Cell Handover

In the incoming internal inter-cell handover procedure, the channel assignment is related to MS

classmark 3.

l If the BSC does not obtain MS classmark 3, or if MS classmark 3 indicates that the MSsupports only the underlaid frequency band, then the BSC assigns only the underlaid

channels to the MS.


bands, the BSC assigns underlaid or overlaid channels to the MS based on Pref. Subcell

in HO of Intra-BSC.

Because the inter-cell handover is generally triggered on the cell edge, you are advised to set

the Pref. Subcell in HO of Intra-BSC to Underlaid Subcell.

Incoming External Inter-Cell Handover

In the incoming external inter-cell handover procedure, the channel assignment is related to MSclassmark 3.

l If the BSC does not obtain MS classmark 3, or if MS classmark 3 indicates that the MS

supports only the underlaid frequency band, then the BSC assigns only the underlaid

channels to the MS.


bands, the BSC assigns underlaid or overlaid channels to the MS based on Incoming-to-

BSC HO Optimum Layer.

Because the inter-cell handover is generally triggered on the cell edge, you are advised to set

the Incoming-to-BSC HO Optimum Layer to Underlaid Subcell.

21.4.2 GSM900/DCS1800 Co-BCCH Cell Handover

This describes the GSM900/DCS1800 Co-BCCH cell handover. The Co-BCCH cell handover

is based on the handover algorithm of the concentric cell.

Neighbor Cell Selection

Based on the M criteria, the actual RX level of the serving cell is used for the handover decision

and the RX level of the neighbor cells is used for neighbor cell queuing, no matter the MS is

located in the overlaid subcell or the underlaid subcell. When the MS is in the overlaid subcell,

the underlaid subcell is handled as a special neighbor cell.

Handover Within an Enhanced Concentric Cell

The underlaid subcell can provide better speech quality in a concentric cell. Therefore, the

utilization ratio of the underlaid subcell is maximized.

The underlaid-to-overlaid subcell handover occurs only when the traffic volume in the underlaid

cell is high, the RX level of the MS is high, the RX quality of the MS is good, and the TA value

is low. In other words, all the following conditions must be met:

l DL RX Level ≥ UtoO HO Received Level Threshold

This condition is controlled by RX_LEV for UO HO Allowed.

l DL RX Quality < RX_QUAL Threshold





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This condition is controlled by RX_QUAL for UO HO Allowed.

l TA < (TA Threshold – TA Hysteresis)

This condition is controlled by TA for UO HO Allowed.

l Traffic of the underlaid subcell > Tch Traffic Busy Underlay Threshold

This condition is controlled by Underlaid Subcell HO Step Period (s) and Underlaid

Subcell HO Step Level.

If the serving cell has the highest priority in the neighbor cell queue, the overlaid-to-underlaid

subcell handover occurs when the RX level of the MS, the RX quality of the MS, or the TA

deteriorates. In other words, one of the following conditions should be met:

l DL RX Level < OtoU HO Received Level Threshold

This condition is controlled by RX_LEV for UO HO Allowed.

l DL RX Quality ≥ RX_QUAL Threshold

This condition is controlled by RX_QUAL for UO HO Allowed.

l TA ≥ (TA Threshold – TA Hysteresis)

This condition is controlled by TA for UO HO Allowed.

If the serving cell does not have the highest priority in the neighbor cell queue, the MS is handed

over to another neighbor cell.

Inter-Subcell Handover

The actual RX level of the cell is used for all the handover decision algorithms except the PBGT

handover decision algorithm.

The PBGT algorithm calculates the path loss of the neighbor cell at the same layer and hierarchy

by using the RX level of the underlaid cell for handover decision. Because of fast fading of thesignal level transmitted by the DCS1800 TRXs in the overlaid subcell, the handover decision

based on the actual RX level in the overlaid subcell is improper when compared with the RX

level in a neighbor cell. To ensure the accuracy of the PBGT handover decision, the handover

decision should be based on the RX level in the underlaid subcell.

For the incoming inter-cell handover and the incoming-to-BSC handover in the Co-BCCH cell,

to avoid a low handover success rate due to inaccurate signal level of the target cell, set Pref.

Subcell in HO of Intra-BSC and Incoming-to-BSC HO Optimum Layer to Underlaid

Subcell.

21.5 Capabilities None.

21.6 ImplementationThis describes the configuration principle, configuration preparation, scenario analysis,

configuration procedure, and deactivation of the Co-BCCH cell.

21.6.1 Configuration Principles

This describes the configuration principles of the Co-BCCH cell.

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A Co-BCCH cell consists of an overlaid subcell and an underlaid subcell. The specific band

configuration is as follows:

l If the overlaid subcell is configured with the DCS1800 TRX, the underlaid subcell is

configured with the GSM900 or GSM850 TRX.

l If the overlaid subcell is configured with the PCS1900 TRX, the underlaid subcell is

configured with the GSM850 TRX.

NOTE

The path loss of the DCS1800 TRX is fast. At the distance of 0.5 to 1 km, the signal power of the DCS1800

TRX is about 15 dB less than the signal power of the GSM900 TRX.

Configure the Co-BCCH cell based on the following principles:

l Generally, do not assign the overlaid subcell channel to a call, do not assign the incoming

inter-cell handover request directly to the overlaid subcell, and do not forcibly assign a call

beyond coverage of the DCS1800 TRX to the overlaid subcell.

l

Properly assign the traffic volume in the underlaid subcell and the overlaid subcell tomaintain the traffic balance between the overlaid subcell and the underlaid subcell.

l Configure the BCCH in the GSM900 TRX. The priority of the TRX types from high to low

is: P-GSM, E-GSM, and R-GSM.

l Configure the SDCCH, PDCH, and BCCH in the same TRX.

l The frequency hopping between the GSM900 frequencies and the DCS1800 frequencies

is not allowed. The frequency hopping between frequencies within the same frequency

band is allowed.

l Prevent a multi-layer concentric cell due to inconsistent combination mode of the TRXs

on the same frequency band. A multi-layer concentric cell deteriorates the network KPI,

such as handover success rate and assignment success rate.

21.6.2 Preparations for the Configuration

This describes the preparations for configuring the Co-BCCH cell. You are required to be

familiar with the related information based on which the parameter configuration is performed.

Get familiar with the state of the current cell, which includes the following items:

l User distribution and traffic volume in the coverage area of the site

l Ratio of the coverage of the DCS1800/PCS1900 TRX to the coverage of the entire cell

l Ratio of the coverage of the GSM900/GSM850 TRX to the coverage of the entire cell

l Whether the GSM900/GSM850 TRXs can carry all the traffic in the cell.

l Number of the GSM900/GSM850 TRXs and the DCS1800/PCS1900 TRXs. Whether the

frequency reuse on the GSM900/GSM850 band is tight and whether the interference exists.

Pay attention to the following restrictions on network planning:

l Number of TRXs

– If the traffic is distributed mainly in the overlaid subcell and if the congestion is unlikely

to occur in the underlaid subcell, the number of TRXs configured in the underlaid subcell

can be small.

– If the traffic volume in the underlaid subcell is high, the TRXs in the underlaid subcell

should outnumber or be equal to the TRXs in the overlaid subcell to prevent thecongestion in the underlaid subcell.





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– If the TRXs in the underlaid subcell are not enough, the TRXs in a fully-loaded underlaid

subcell are likely to be congested in high traffic hours. This deteriorates the network

KPIs, such as TCH Seizure Success Rate and handover success ratio.

l Neighbor cell

– This factor is neglectable if the Co-BCCH cell is not adjacent to two or more single- band cells at the same time.

– If the Co-BCCH cell is adjacent to two single-band cells using the two bands of the Co-

BCCH cell at the same time, you should consider the network hierarchy.

– This factor is neglectable if the Co-BCCH cell has a low priority.

– If the Co-BCCH cell is adjacent to two single-band cells using the two bands of the

Co-BCCH cell at the same time, you should consider the network hierarchy.

– You should consider the traffic load of neighbor cells if the Co-BCCH cell has

a high priority. If the traffic load of neighbor cells is high, the traffic distributed

on edge of a common cell is absorbed by the Co-BCCH cell. Thus, the TRXs in

the underlaid subcell are likely to be congested and the network KPIs, such asTCH Seizure Success Rate and handover success ratio are deteriorated. In this

case, the Co-BCCH cell is not recommended.

– If the Co-BCCH cell has to be used, you should analyze the traffic distribution

based on the congestion conditions in the underlaid subcell and then adjust the

handover parameters of related cells. The purpose is to prevent the calls on edge

of a common cell from being handed over to the Co-BCCH cell.

21.6.3 Risk Analysis of the Configuration Scenarios

This describes the risk analysis of the configuration scenarios. The configuration scenarios

consist of common and special scenarios.

In the Co-BCCH cell, two types of TRXs with different coverage capabilities are configured.

Therefore, the traffic volume of the overlaid and underlaid subcells should be properly assigned

without deteriorating the network KPIs. The traffic assignment of the overlaid and underlaid

subcells is influenced by two factors. One is the number of TRXs in the overlaid and underlaid

subcells, and the other is the actual coverage of the overlaid and underlaid subcells (represented

by the inter-site distance).

Risk Analysis in Common Scenarios

Table 21-4 lists the risk analysis in common scenarios.

21 Co-BCCH Cell





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Table 21-4 Risk analysis in common scenarios

No.

ScenarioDescription

Scenario Analysis Risk Solution

1 The inter-

site distance

is within

800 m.

The coverage capability of

the DCS1800 TRXs is

equivalent to that of the

GSM900 TRXs.

Therefore, the underlaid-

to-overlaid or overlaid-to-

underlaid handover in the

Co-BCCH cell is unlikely

to fail.

There is no risk,

and the Co-

BCCH cell can

be enabled.

None

2 l The inter-

sitedistance

is from

800 m to

1,600 m.

l The

number

of TRXs

in the

underlaid

subcell is

equal to

or morethan the

number

of TRXs

in the

overlaid

subcell.

The overlaid subcell only

covers about half of thecoverage area of a Co-

BCCH cell. The underlaid

subcell configured with

enough TRXs can cover

the remaining area of a Co-

BCCH cell. Therefore, the

risk is low.

The risk is

small, and theCo-BCCH cell

can be enabled.

Assigns enough traffic

volume to the underlaidsubcell with

precondition that no

congestion occurs in

the underlaid subcell.

Thus, the risk of

underlaid-to-overlaid

handover in high traffic

hours is minimized.

Adjust UtoO HO

Received Level

Threshold to arrange

the traffic of theoverlaid and underlaid

subcells.

l If the value of this

parameter is

reduced, the number

of underlaid subcell

to overlaid subcell

handovers increases.

l If the value of this

parameter is

increased, thenumber of underlaid

subcell to overlaid

subcell handovers

decreases.





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No.

ScenarioDescription


3 l The inter-

site

distance

is from

800 m to

1,600 m.

l The

number

of TRXs

in the

underlaid

subcell is

less thanthe

number

of TRXs

in the

overlaid

subcell.

The overlaid subcell only

covers about half of the

coverage area of a Co-


subcell with few TRXs

may not (or just be able to)

cover the remaining area

of a Co-BCCH cell.

Therefore, most of the

traffic is handed over to

the overlaid subcell in high

traffic hours. Possible

risks are as follows:l Certain calls beyond the

coverage of the overlaid

subcell are likely to be

handed over to the

overlaid subcell and the

handover fails.

l With the increase of cell

traffic, the underlaid

subcell becomes badly

congested while the

overlaid subcell

remains idle. In

addition, the

performance indicators,

such as the underlaid-

to-overlaid handover

success rate and the

DCS1800 channel

seizure success rate are

deteriorated.

The risk is

medium, and

you are advised

not to enable the

Co-BCCH. If

you enable the

Co-BCCH, you

are advised to

enable halfrate

channels in the

underlaid

subcell or to add

underlaidTRXs.

Enable the half-rate

services or increase the

TRXs in the underlaid

subcell.

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No.

ScenarioDescription


4 l The inter-

site

distance

is more

than

1,600 m.

l The

number

of TRXs

in the

underlaid

subcell is

equal toor more

than the

number

of TRXs

in the

overlaid

subcell.

The overlaid subcell

covers less than half of the


BCCH cell and the

underlaid subcell is

configured with enough

TRXs. Based on the

quantity and distribution

of users, either of the

following scenarios may

occur:

l Scenario 1

Most users are in theoverlaid subcell. The

TRXs of the underlaid

subcell can carry the

traffic in coverage of

the underlaid subcell. In

this situation, the

underlaid subcell

should carry most of the

traffic to reduce the risk

cause by the underlaid-

to-overlaid handover in

high traffic hours.

l Scenario 2

Users are distributed

evenly and the

underlaid subcell TRXs

cannot (or just be able

to) carry the traffic in

the coverage area of the

underlaid subcell. Thus,

the underlaid subcell

becomes badly

congested and theoverlaid subcell

remains idle. In

addition, the

performance indicators,

such as the underlaid-

to-overlaid handover


DCS1800 channel


deteriorated.

The risk is

medium.

l For scenario

1, the Co-

BCCH can be

enabled.

l For scenario

2, you are

advised not to

enable the

Co-BCCH. If

you enable

the Co-

BCCH, you

are advised to

enable

halfrate

channels in

the underlaid

subcell or to

add underlaid

TRXs.

None





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No.

ScenarioDescription


5 l The inter-

site

distance

is more

than

1,600 m.

l The

number

of TRXs

in the

underlaid

subcell is

less thanthe

number

of TRXs

in the

overlaid

subcell.

The overlaid subcell

covers less than half of the



subcell with few TRXs

cannot (or just be able to)

carry the traffic in the

coverage of the underlaid

subcell. Possible risks are

as follows:

l The underlaid subcell is

badly congested.

l The overlaid subcell

remains idle.

l The underlaid-to-

overlaid handover


DCS1800 channel


deteriorated.

The risk is large,

and the Co-

BCCH cannot

be enabled.

Enable the half-rate

services or increase the

TRXs in the underlaid

subcell.

The methods for determining the risks are as follows:

l In a common dual-band network, if the congestion does not occur in the overlaid or

underlaid subcell, the related performance indicators have no change after the Co-BCCH

cell is enabled.

l In a common dual-band network, if the congestion in the GSM900 subcell occurs at an

earlier time than in the DCS1800 subcell, a forcible traffic transfer from the GSM900

subcell to the DCS1800 subcell is likely to deteriorate the KPIs. In this case, related

performance indicators are deteriorated if the Co-BCCH cell is enabled. For example, the

underlaid-to-overlaid handover success rate and the DCS1800 channel seizure success rate

are reduced.

Risk Analysis in Special Scenarios

Use the following methods to eliminate problems which may occur when the Co-BCCH cell is

enabled in special scenarios:

l The TRXs number in the overlaid and underlaid subcells is equivalent and most of the

traffic should be assigned in the overlaid subcell.

You can lower the value of UtoO HO Received Level Threshold to increase the traffic

in the overlaid subcell. To avoid ping-pong handovers because of signal level fluctuation,

the value of OtoU HO Received Level Threshold should be less than 25.

l Severe interference exists in the GSM900 subcell.

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– You can suppress the interference to some extent by adjusting the parameters related to

concentric cell.

– When the inter-site distance is less than 1,000 m, add the traffic in the overlaid subcell.

NOTE

You can determine that the GSM900 channel is seriously interfered if the interference band is high,

the RX quality is bad, and the call drop rate is 1.2 times or more than the call drop rate of the DSC1800

channel.

l In a common dual-band network, only few cells are configured to be the Co-BCCH cells.

The neighbor cells are single-band or dual-band cells.

In a common dual-band network, the DCS1800 cell is at Level 2 and the GSM900 cell is

at level 3. That is, the DCS1800 cell level is higher than the GSM900 cell level. In this

situation, the following may occur when the Co-BCCH cell is enabled:

– If the Co-BCCH cell is set to level 2, the traffic absorption capability of the GSM900

TRX becomes enhanced. The traffic of the neighbor cells is absorbed. Thus, the traffic

volume of the cell increases sharply and related performance indicators are deteriorated.– If the Co-BCCH cell is set to level 3, the traffic in the coverage of the DCS1800 TRX

is absorbed by the neighbor cells. The cell traffic volume is decreased.

To avoid these risks, you must enable the Co-BCCH cell in the neighbor sites.

21.6.4 Configuring the Co-BCCH Cell

This describes how to configure the Co-BCCH cell on the BSC6000 Local Maintenance

Terminal.

Procedure

Step 1 Add a Co-BCCH cell


click the target BTS and then choose Add Cell on the shortcut menu. The Add Cell dialog

box is displayed.

2. Click Add Cell. A dialog box is displayed, as shown in Figure 21-1.

Figure 21-1 Add New Cell dialog box





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NOTE

Figure 21-1 takes an example of external PCU. When the PCU is in built-in mode, there is no PCU

Name in Figure 21-1.

3. In Figure 21-1, set Frequency Band to GSM900&DCS1800 or GSM850&DCS1800,

and then click OK . The Add Cell dialog box is returned.

NOTE

If you select GSM850&PCS1900, you must set High Frequency Band to PCS1900.

4. Click Next. The Set Site Attributes dialog box is displayed.

5. Select a site from the Site List, and then click Set Site Device to set related parameters.

NOTE

You must set Add Chain and Manual Abis according to transmission path and customer

requirements.

Step 2 Configure cell attributes

1. Click Next. The Set Cell Attributes dialog box is displayed. Select cells from the Cells to

be set list box, and then click Set Cell Attributes. A dialog box is displayed, as shown in

Figure 21-2.

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Figure 21-2 Set Cell Attributes dialog box

2. Set BCCH IUO Attribute.

Step 3 Assign TRXs for the add cell

1. In the dialog box shown inFigure 21-2, click Frequency Config. A dialog box is displayed,

as shown in Figure 21-3.





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Figure 21-3 Set Cell Frequency dialog box

2. Select the GSM900 frequencies and DCS1800 frequencies, and then click OK to return to

the dialog box shown in Figure 21-2.

Step 4 Set the attributes of the newly assigned TRXs

1. In the dialog box shown in Figure 21-2, click TRX Config. A dialog box is displayed, as

shown in Figure 21-4.

Figure 21-4 Configure TRX Attributes dialog box (1)

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2. On the Frequency Attributes tab page, double-click a target frequency in Available

Frequencies to add the frequency to Assigned Frequencies.

3. On the Device Attributes tab page, check Value of the HW_Concentric Attri

Documents

BSS Feature Description (Continue).pdf