high speed access

RAN

High Speed Access

Issue 01

Date 2009-03-30

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RANHigh Speed Access

About This Document

About This Document

Author

Prepared by Fu Song Date 2008-12-26

Reviewed by Ren Wei and Zhang Jianhua Date 2009-01-04

Translated by Wu Gongbo Date 2009-01-15

Tested by Hu Zengqiang Date 2009-02-15

Approved by Li Qiang Date 2009-03-30

Change History

Document Version

Change History Date Author

Draft completed 2008-12-26 Fu Song

Draft The comments of the first review incorporated

2009-01-04 Fu Song

Draft This is the draft of the document for RAN11.0.

2009-01-15 Fu Song

Draft this issue optimizes the description. 2009-03-10 Fu Song

Issue 01 (2009-03-30) Huawei Proprietary and Confidential Copyright © Huawei

Technologies Co., Ltd

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Contents

Contents

1 Change History...........................................................................1-2

2 Information................................................................................2-22.1 Background.....................................................................................................................................................2-2

2.2 Introduction....................................................................................................................................................2-2

2.3 Availability......................................................................................................................................................2-2

2.3.1 Intended Audience.................................................................................................................................2-2

2.3.2 Impact....................................................................................................................................................2-2

2.3.3 Network Elements Involved..................................................................................................................2-2

2.3.4 Software Versions..................................................................................................................................2-2

2.3.5 Protocol Conformity..............................................................................................................................2-2

3 Technical Description..................................................................3-23.1 Principle of High Speed Access.....................................................................................................................3-2

3.1.2 AFC for the DPCH................................................................................................................................3-2

3.1.3 AFC for the PRACH.............................................................................................................................3-2

4 Implementation..........................................................................4-24.1 Enabling High Speed Access..........................................................................................................................4-2

4.1.1 Hardware Requirements........................................................................................................................4-2

4.1.2 Configuring Data...................................................................................................................................4-2

4.1.3 Verifying the Configuration..................................................................................................................4-2

4.2 Disabling High Speed Access.........................................................................................................................4-2

4.2.1 Reconfiguring the Cell Parameters.......................................................................................................4-2

4.2.2 Verifying the Configuration..................................................................................................................4-2

5 High Speed Access Parameters....................................................5-25.1 Description.....................................................................................................................................................5-2

5.2 Values and Ranges..........................................................................................................................................5-2

6 Maintenance Information............................................................6-26.1 Counters..........................................................................................................................................................6-2

6.2 Alarms.............................................................................................................................................................6-2

7 Reference Documents.................................................................7-2



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1 Change History

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

Document and Product Versions

Document Version RAN Version

01 (2009-03-30) 11.0

Draft (2009-03-10) 11.0

Draft (2009-01-15) 11.0

The available time of each feature is subject to the RAN product roadmap.

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

Feature change: refers to the change in the high speed access feature.

Editorial change: refers to the change in the information that was inappropriately described or the addition of the information that was not described in the earlier version.

01 (2009-03-30)

This is the document for the first commercial release of RAN11.0.

Compared with draft (2009-03-10), this issue optimizes the description.

Draft (2009-03-10)

This is the second draft of the document for RAN11.0.

Compared with draft (2009-01-15), draft (2009-03-10) optimizes the description.

Draft (2009-01-15)

This is the initial draft of the document for RAN11.0.



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2 Information

2.1 BackgroundWith the continuous improvement of the radio network coverage, the customers have been imposing increasingly high requirements on its quality. As one of the network coverage applications, the high speed access feature is highly demanded in the telecommunications in high speed railways and expressways in the mature markets such as Europe and America. As high speed railways are under construction or put into operation all over China, China is also in great demand for this feature.

On high speed vehicles, the WCDMA users have higher demands for the services, including not only speech and video services but also high speed data services. The provisioning of better 3G services from the telecom operators will significantly increase the user satisfaction.

WCDMA can provide real-time navigation information, road condition information, traffic flow information, warning information, emergency information, and even real-time video images on the spot.

Since this feature has been written into 3GPP, it becomes a fundamental feature of all NodeBs. As specified in the 3GPP standards, the highest speed is 350 km/h. However, Huawei NodeBs can support the access at the highest speed of 450 km/h, which has been proven in the maglev trains in Shanghai.

2.2 IntroductionSpeed is the biggest advantage of high speed railways, but high speed access imposes a great challenge for the mobile telecommunications. The fast movement of mobile terminals will lead to serious signal fading and Doppler shift, thus severely restricting the improvement of the quality of service (QoS) of the mobile telecommunications system.

In comparison with the low speed mobile telecommunications, the time-selective fading caused by the Doppler shift in the high speed movement will increase the bit error rate. In the WCDMA system, the Doppler shift will decrease the signal energy provided by the correlator, thus affecting the acquisition of the spreading code. As a result, the spreading code of the WCDMA receiver cannot synchronize with that of the received signal and thus the user information cannot be detected.



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The Doppler shift has a positive correlation with the moving speed and communication frequency. When the frequency shift is 800 Hz or higher, the Signal-to-Noise Ratio (SNR) becomes infinite. At this time, the call drop or connection failure may occur.

Huawei NodeBs employ the Automatic Frequency Control (AFC) function to offset the Doppler shift to support the high speed access of mobile terminals. In this manner, the requirements for mobile telecommunications in the high speed traffic system can be met.

2.3 Availability

2.3.1 Intended AudienceThis document is intended for:

System operators who need a general understanding of high speed access feature.

Personnel working on Huawei products or systems.

2.3.2 Impact Impact on the system

− When considerable frequency offset occurs between the UE and the NodeB, the demodulation performance of the system deteriorates even if high speed access is applied.

− When the UE moves at the speed of 450 km/h and its signals are transmitted on the Gaussian channel, the demodulation performance of the Dedicated Channels (DCHs) decreases by at most 0.7 dB, and the demodulation performance of the access channels decreases by at most 4 dB.

Impact on other features

− High speed access may have an impact on the receive performance and handover performance of a UE. The impact on performance varies according to the UE categories. In a test, the poor performance of the UE may lead to call drops during the handover.

− With high speed access, one cell consumes the access resources of three cells. This factor must be taken into consideration during hardware configuration.

− High speed access does not support 4-way RX diversity.

− The radius of a high speed access cell should not be longer than 30 km.

Performance

The UE can access the network at the highest speed of 450 km/h.

2.3.3 Network Elements InvolvedHigh speed access is involved only in the NodeB and has no impact on other network elements (NEs).

Table 2-1 lists the NEs involved in high speed access:



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Table 2-1 NEs involved in high speed access

UE NodeB

RNC MSC Server

MGW SGSN GGSN HLR

– √ – – – – – –

–: not involved √: involved

UE = User Equipment, RNC = Radio Network Controller, MSC Server = Mobile Service Switching Center Server, MGW = Media Gateway, SGSN = Serving GPRS Support Node, GGSN = Gateway GPRS Support Node, HLR = Home Location Register

2.3.4 Software VersionsTable 2-1 describes the versions of the products that support high speed access.

Table 2-1 Versions of the products that support high speed access

Product Version Remarks

BTS3812E/BTS3812AE V100R010 and later versions Configured with the HULP/HBBI/HBOI board

DBS3800 V100R010 and later versions -

DBS3900 V200R010 and later versions -

BTS3900/BTS3900A V200R010 and later versions -

2.3.5 Protocol ConformityThis feature conforms to 3GPP TS 25.101.



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3 Technical Description

3.1 Principle of High Speed AccessThe movement of a UE causes the time variation of the mobile channel. As a result, the received signals incur the Doppler shift. The Doppler shift caused by the fast-moving UE is described as follows:

f d=fC

×v×cos θ

where

fd refers to the Doppler shift.

f refers to the carrier frequency of the WCDMA system.

C refers to the transmission speed of electromagnetic waves.

v refers to the moving speed of the UE.

θ refers to the included angle between the moving direction of the UE and the transmission direction of the signals.

As shown in Figure 3-1, the downlink (DL) frequency of the UE is locked to the NodeB frequency f0; therefore, for the uplink (UL) demodulation of the NodeB, the Doppler shift is 2fd. If the frequency (f) is 2000 MHz, then the 2fd that corresponds to the radial movement at 1 km/h is 3.7 Hz.

Figure 3-1 Doppler shift



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To support high speed access, the NodeB must support the AFC function. The RAKE receiver that does not support AFC cannot correctly demodulate signals even if the SNR infinitely increases when the frequency offset reaches 800 Hz or above. In this case, call drops may occur or the network access may fail.

The UL channel can be classified into the UL Dedicated Physical Channel (DPCH) and the UL Physical Random Access Channel (PRACH). The NodeB must support AFC for both UL DPCH and UL PRACH.

Huawei adopts different solutions to implement the AFC function for the DPCH and the PRACH.

3.1.2 AFC for the DPCHThe AFC function for the DPCH authenticates the frequency according to the phase variation of the fading factors to obtain the frequency offset of current signals, as shown in Figure 3-1. Then, through the loop feedback mechanism, the RAKE receiver performs frequency offset correction on the input signals. The AFC function for the DPCH is always applied to Huawei NodeBs even when the high speed access feature is not enabled.

Figure 3-1 AFC for the DPCH

Figure 3-2 shows the impact of AFC on the demodulation performance of the DPCH.

Figure 3-2 Impact of AFC on the demodulation performance of the DPCH



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3.1.3 AFC for the PRACHThe AFC function for the PRACH is similar to that for the DPCH. The difference is that the non-ring frequency correction mode is adopted for the PRACH because the signal exists for only a very short time (10 ms or 20 ms). The PRACH signal is divided into two routes. One is enabled with AFC while the other is not. Then, the route not enabled with AFC is estimated so as to obtain the frequency correction parameters. With the parameters, the frequency correction is performed on the other route. In addition, the frequency correction density for the PRACH is higher than that for the DPCH. Thus, the accuracy of the frequency correction can be ensured to the maximum. After the frequency correction is complete, the PRACH decoding is performed, as shown in Figure 3-1.

Figure 3-1 AFC for the PRACH

You can use the High Speed Movement Mode parameter to enable or disable the AFC function for the PRACH, and use the Speed Rate (km/h) parameter to set the highest moving speed that the frequency offset corresponds to.

Figure 3-2 and Figure 3-3 describe the impact of AFC on PRACH preamble detection performance and on PRACH message demodulation performance respectively.

Figure 3-2 Impact of AFC on PRACH preamble detection performance



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Figure 3-3 Impact of AFC on PRACH message demodulation performance



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4 Implementation

The following describes how to enable and disable the high speed access feature.

4.1 Enabling High Speed Access

4.1.1 Hardware RequirementsThe NodeBs that support this feature are as follows:

BTS3812E/BTS3812AE configured with the EULP/EBBI/EBOI board

DBS3800

DBS3900

BTS3900/BTS3900A

4.1.2 Configuring DataIn initial data configuration, run ADD LOCELL, MOD LOCELL to set HISPM to TRUE, and set SPR to 500. That is, enable the local cell to support high speed access.

Example: ADD LOCELL: SECT=REMOTE_SECTOR, HISPM=TRUE, SPR=500

4.1.3 Verifying the ConfigurationRun LST LOCELL to check whether the new local cell is successfully configured.

4.2 Disabling High Speed Access

4.2.1 Reconfiguring the Cell ParametersWhen the NodeB is working, run MOD LOCELL to set HISPM to FALSE to disable high speed access.



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4.2.2 Verifying the ConfigurationRun LST LOCELL to check whether the feature is successfully disabled.



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5 High Speed Access Parameters

5.1 Description

Table 5-1 High speed access parameter description

Parameter ID

Description

HISPM High Speed Movement Mode of the Local Cell.

SPR Speed Rate of High Speed Local Cell.

5.2 Values and Ranges

Table 5-1 High speed access parameter values and parameter ranges

Parameter ID

Default Value

GUI Value Range Actual Value Range

Unit MML Command

NE

HISPMFALSE (ADD LOCELL)

FALSE (Not Support), TRUE (Support)

FALSE, TRUE NoneADD LOCELL(Optional)/ MOD LOCELL

NodeB

SPR -250 (250km/h), 400 (400km/h), 500 (500km/h)

250, 400, 500 km/hADD LOCELL(Mandatory)/ MOD LOCELL

NodeB

The Default Value column is valid for only the optional parameters.

The "-" symbol indicates no default value.



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6 Maintenance Information

6.1 Countershigh speed access has impacts on demodulation performance counters. That is, when the UE moves at the speed of 450 km/h and its signals are transmitted on the Gaussian channel, the demodulation performance of the Dedicated Channels (DCHs) decreases by at most 0.7 dB, and the demodulation performance of the access channels decreases by at most 4 dB.

6.2 AlarmsTable 6-1 describes the alarms related to high speed access.

Table 6-1 Alarms related to high speed access

Alarm ID Alarm Name Alarm Type

ALM-4033 Local Cell Unusable Fault



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7 Reference Documents

The following lists the reference documents related to the feature:

1. 3GPP TS 25.101 "User Equipment (UE) radio transmission and reception (FDD), V5.8.0"

2. Basic Feature Description of Huawei UMTS RAN11.0 V1.5

3. Optional Feature Description of Huawei UMTS RAN11.0 V1.5



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