CPCWCDMA RAN

USER DESCRIPTION

333/1553-HSD 101 02 Uen B

Copyright

© Ericsson AB 2010. All rights reserved. No part of this document may bereproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due tocontinued progress in methodology, design and manufacturing. Ericsson shallhave no liability for any error or damage of any kind resulting from the useof this document.

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Ericsson is the trademark or registered trademark ofTelefonaktiebolaget LM Ericsson.

All other trademarks mentioned herein are the propertyof their respective owners. These are listed in thedocument Trademark Information.

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Contents

Contents

1 Introduction 1

1.1 Scope 1

1.2 Target Groups 1

1.3 Revision Information 1

2 Overview 1

2.1 FAJ 121 1389: Enhanced Uplink Transmission, CPC 2

2.2 FAJ 121 1476: Enhanced Downlink Reception, CPC 3

3 Technical Description 3

3.1 Enhanced Uplink Transmission, CPC 3

3.2 Enhanced Downlink Reception, CPC 5

4 Activation and Deactivation 7

4.1 FAJ 121 1389: Enhanced Uplink Transmission, CPC 7

4.2 FAJ 121 1476: Enhanced Downlink Reception, CPC 8

5 Engineering Guidelines 8

6 Parameters 9

6.1 Range and Default Values 10

Reference List 11

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CPC

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Overview

1 Introduction

This document describes the operation and function of Continuos PacketConnectivity (CPC) within the WCDMA Radio Access Network (RAN).

1.1 Scope

This document contains an overview description of CPC and the featuresrelated to it. The document also contains information about the activation anddeactivation of the features that are related to CPC. It also includes engineeringguidelines for CPC.

1.2 Target Groups

This document is written for system operators. It is assumed that users of thisdocument are familiar with WCDMA basics and have a working knowledge of3G telecommunication.

1.3 Revision Information

The following table lists the changes in the latest revisions of this document.Other than editorial changes, this document has been revised as follows:

Table 1 Revision Information

Rev Reason for Revision

A This document replaces 333/1553-HSD 101 02/10 Uen C with thesame title. Editorial changes only.

B Chapter 5 added recommendation on inactivity timer values

2 Overview

The control channel (DPCCH) is transmitted continuously on theHS-DSCH/E-DCH. With the introduction of CPC, the User Equipment (UE)can send the control channel discontinuously and thus shut off its transmitter,

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CPC

thereby creating less interference and saving battery power. On the Downlink(DL), the UE can shut off its receiver to save even more battery power.

CPC is a 3GPP Rel-7 optional feature (more information can be found inreference [5]).

The feature constitutes an umbrella of functions and aims at improving thefollowing:

• UE power consumption

• Latency by staying longer on CELL_DCH

In WRAN there are two optional features covering CPC and they are alwaysactivated together. The two features include a subset of the functions definedin the 3GPP standard.

When CPC is activated, the feature operates on connections on EUL/HSDPAradio channels. Both UL TTI 2ms and 10ms are supported. Besides activationor deactivation per RBS and cell level, the operator can configure a separateswitching timer from CELL_DCH to CELL_FACH for CPC capable UE in orderto have operator tuning control.

CPC is supported with maximum one RL in the active set. If a soft/softerhandover addition is triggered a reconfiguration to non-CPC will be madebefore a radio link addition is made.

There is an impact on power control from CPC due to discontinuouslytransmitting the TPC commands (more information on power control canbe found in Power Control). The Uu Load Estimator is modified in the EULScheduler to take discontinuous transmission of active CPC users into account(more information on EUL scheduler can be found in Enhanced UL Scheduler).The procedures for channel switching are updated with CPC capability asdescribed in Channel Switching. Modifications have been made for the HSDPAscheduler to make sure that data is only scheduled in the DRX pattern of theCPC UE (more information on HSDPA scheduler can be found in HSDPAUser Plane).

2.1 FAJ 121 1389: Enhanced Uplink Transmission, CPC

The Enhanced Uplink Transmission feature allows CPC-capable UE tosend the control signalling UL DPCCH discontinuously while inactive onCELL_DCH. This results in lower power consumption for the inactive CPC UEon HS-DSCH/E-DCH, and less uplink interference since the CPC users aretransmitting less control signalling when inactive on CELL_DCH. The functionsof Enhanced Uplink Transmission, CPC are further described in Section 3.1 onpage 3.

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Technical Description

2.2 FAJ 121 1476: Enhanced Downlink Reception, CPC

The Enhanced Downlink Reception feature allows CPC-capable UE to listendiscontinuously to the scheduling channel (HS-SCCH) while inactive onCELL_DCH. This results in a lower power consumption for CPC-capableUE configured with HS-DSCH/E-DCH. The functions of Enhanced DownlinkReception, CPC are further described in Section 3.2 on page 5.

3 Technical Description

The objective of CPC in WRAN is battery saving gains from permittingCPC-capable UE to turn off their transmitters or receivers, or both, in definedintervals when there is no data transmission. Another benefit is that it willreduce the uplink noise rise from physical control channels of EUL users in thecell. By allowing CPC-capable UE to stay inactive in CELL_DCH state forlonger time periods, the UE can restart transmission after a period of inactivitywith a much shorter delay than would be necessary for reestablishment of anew connection. This will also help to reduce the number of channel switchesbetween CELL_FACH and CELL_DCH.

3.1 Enhanced Uplink Transmission, CPC

The functions of the Enhanced Uplink Transmission, CPC feature are thefollowing:

• UL DTX

• CQI reporting reduction

• MAC DTX

3.1.1 UL DTX

In HS-DSCH/E-DCH, the UL shared resource is the interference headroomin the cell. A non-CPC-capable UE configured with E-DCH continuouslysends the DPCCH uplink control channel. Therefore, when no data is beingtransmitted, interference generated by a UE is entirely due to the DPCCH. WithUL DTX, the CPC-capable UE is ordered by the RNC to periodically switch offthe transmission of DPCCH if no data is to be transmitted. This is illustrated inthe Page 4.

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CPC

DPCCH

E-DCH

E-DCH

DPCCH

Non-CPCuser

CPC user

U0000780A

Figure 1 Principle behind UL DTX

When inactive in CPC, the UE discontinuously transmits a short DPCCHburst to regulate power control and keep synchronization. When the UE istransmitting data, the DPCCH is transmitted continuously, the behavior is thesame as for a non-CPC users. As a consequence, the benefits of the UL DTXfunction, in terms of reduced interference and decreased power use, increaseswith a lower activity factor for the traffic.

The short DPCCH bursts that are sent discontinuously in intervals when theCPC user is inactive are preceded by two slots of preamble and followedby one slot of postamble, as seen in Page 4. The burst and the preambleand postamble consist of ordinary DPCCH slots. The DTX cycle period is 20subframes.

U0000781A

UL DTX cycle

DPCCH burst length

2 slot preamble 1 slot postamble

DPCCH

Figure 2 Illustration of the UL DTX Cycle

3.1.2 CQI Reporting Reduction

The UL DPCCH is not the only control channel that has been modifiedfor CPC. The HS-DPCCH is the control channel used to transmit HARQacknowledgment, together with the CQI reports. The CQI reports in theHS-DPCCH channel are also discontinuously transmitted after a certain periodof HSDPA inactivity. With CQI Reporting Reduction function, the transmissionof those reports depends on whether there has been a recent HS-DSCHtransmission. If no data has been transmitted on the HS-DSCH for a certaintime, CQI reports are transmitted only if they coincide in time with the DPCCHbursts as shown in Page 5.

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Technical Description

U0000782A

ACK/NACK CQI

DPCCH burst transmissions according to the DTX cycle.

CQI reports not transmitted. (The start of CQI fields doesnot overlap with the DPCCH bursts)

Figure 3 CQI Reporting Reduction Function

The CQI Reporting Reduction function will reduce the HS-DPCCH load in UL.There is also a battery gain since it will transmit fewer CQI reports when theCPC user is inactive. If the start of the CQI field overlaps the DPCCH bursttransmission pattern, the CQI is transmitted. Otherwise it is not transmitted.

The CQI Reporting Reduction function allows a further decrease of the controlsignalling overhead for bursty DL traffic. As for UL DTX, the power consumptiondecreases with a lower activity factor for the traffic.

3.1.3 MAC DTX

The MAC DTX function controls the CPC-capable UE so that it does notperform UL data transmission on E-DPDCH and E-DPCCH during the CPC gapthat typically exists between the UL DPCCH bursts. This function is importantto secure the CPC gain on battery since longer CPC gap provides higher CPCgain.

After the last data is transmitted on the E-DCH, the UE has a certain time periodof MAC inactivity to transmit without restriction. When the timer expires, theMAC DTX is started and the UE can only start transmission on the E-DCH atthe MAC DTX cycle pattern.

3.2 Enhanced Downlink Reception, CPC

The function of the Enhanced Downlink Reception, CPC feature is the following:

• DL DRX

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CPC

3.2.1 DL DRX

The HS-DSCH/E-DCH UE is required to monitor up to four HS-SCCHs ineach subframe. On one hand, this allows an optimal scheduling flexibility; onthe other hand, it requires the UE to continuously have its receiver on, whichincrease the UE battery consumption. With the DL DRX function, the UE isordered by the RNC to periodically switch off its receiver if no data is to bereceived. If data needs to be received, CPC UE behavior is the same as thenon-CPC-capable UE behavior.

The network restricts the subframes in which the UE must monitor DLHS-SCCH, E-AGCH, and E-RGCH if no data has been received for a certainperiod.

Note: The E-DCH HARQ Acknowledgement Indicator Channel E-HICHcarrying the HARQ acknowledgement for EUL is for non-CPC and CPCmode monitored when needed. Furthermore, the UE needs to receivethe power control information on the F-DPCH channel in all DL slotscorresponding to UL slots where the UE transmits.

This function is important for CPC battery gain since keeping the receiver oncontinuously has a big impact on UE power consumption.

Page 6 shows an example of the DRX pattern for this function. After anHS-SCCH reception or the first slot of a HS-PDSCH reception, the inactivitytimer is started; the UE must have its receiver on until the timer expires, whenDL DRX is applied.

U0000784A

DL DRX

Inactivity timer for DL DRX

DRX Pattern(Receiver on)Receiver on

Receiver off

t

HS-SCCH reception / HS-PDSCH reception

Figure 4 Example of DL DRX Cycle

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Activation and Deactivation

4 Activation and Deactivation

This section describes activation and deactivation of the CPC features.

The activation or deactivation steps and license key are the same for featureFAJ 121 1389: Enhanced Uplink Transmission, CPC and FAJ 121 1476:Enhanced Downlink Reception, CPC. They are activated simultaneously. Thefeatures cannot be activated or deactivated separately.

4.1 FAJ 121 1389: Enhanced Uplink Transmission, CPC

The Enhanced Uplink Transmission, CPC feature is an optional feature that ishandled with a license key. There is one license CXC 402 0026 per RBS basisthat activates both the Enhanced Uplink Transmission, CPC and EnhancedDownlink Reception, CPC features simultaneously.

4.1.1 Preconditions for Activation

Before FAJ 121 1389: Enhanced Uplink Transmission, CPC can be activated,the following conditions have to be fulfilled:

• The feature requires an installed and activated Enhanced UplinkIntroduction Package (FAJ 121 1023) in the RNC.

• The feature requires an installed and activated F-DPCH (FAJ 121 1481)in the RNC.

4.1.2 Activation

The feature FAJ 121 1389: Enhanced Uplink Transmission, CPC is activatedby installing and activating the license in the RBS. Furthermore, the featureis activated on per cell basis by setting the featureStateCpc parameterto activated.

This will also activate FAJ 121 1476: Enhanced Downlink Reception, CPC.

The parameter cellCapabilityControl.cpcSupport shall be set to "OFF"in this release. The setting of parameter cellCapability.cpcSupportdoes not matter in this release.

4.1.3 Preconditions for Deactivation

There are no preconditions for deactivation of the features.

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CPC

4.1.4 Deactivation

Deactivation on the cell level is done by setting the featureStateCpcparameter to deactivated. Deactivation on RBS level is done by deactivatingthe license key.

4.2 FAJ 121 1476: Enhanced Downlink Reception, CPC

The Enhanced Downlink Reception, CPC feature is an optional feature that ishandled with a license key. There is one license CXC 402 0026 per RBS basisthat activates both the Enhanced Downlink Reception, CPC and EnhancedUplink Transmission, CPC features simultaneously.

4.2.1 Preconditions for Activation

For preconditions for activation, see Section 4.1.1 on page 7.

4.2.2 Activation

For activation, see Section 4.1.2 on page 7.

4.2.3 Preconditions for Deactivation

For preconditions for deactivation, see Section 4.1.3 on page 7.

4.2.4 Deactivation

For deactivation, see Section 4.1.4 on page 8.

5 Engineering Guidelines

The purpose of this section is to provide additional information on practicalengineering aspects about how to use parameters to achieve certain behaviors.

With the CPC features a separate HSDPA inactivity timer forchannel switching from CELL_DCH to CELL_FACH for CPC users,hsdschInactivityTimerCpc, is introduced in addition to the existingHSDPA inactivity timer hsdschInactivityTimer for the non-CPC HSDPAusers. Therefore the operator has the opportunity to configure separate HSDPA

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Parameters

inactivity timers allowing to balance between the UE battery consumption andnetwork load based on CPC or non-CPC UE capabilities.

By setting the hsdschInactivityTimerCpc parameter to a high value, theCPC UE will stay longer on CELL_DCH before switching down to CELL_FACHat inactivity. This will in most cases be perceived as an ‘‘always on’’ experiencefor the end user, with lower latency, and reduce the number of channel switches.When using a higher value on the HSDPA inactivity timer the number of allowedHSDPA users needs to be increased in order to avoid unnecessary HSDPAblocking. It is recommended to avoid too long inactivity timer values for CPC ina HW limited situation to avoid the possible degradation on the accessibility KPI.A lower value for the hsdschInactivityTimerCpc parameter can give apotentially higher number of HSDPA users but the network will have an increasein the number of channel switches between CELL_DCH and CELL_FACH.

The default value of the hsdschInactivityTimerCpc parameter is5 seconds for CPC users, and is longer than the default value of thehsdschInactivityTimer parameter of 2 seconds for non-CPC users.

With the introduction of DTX in CPC, the HS-SCCH and E-HICH powercontrol may receive less frequent input as the reporting frequency of CQIsfrom the UE can be reduced. If any degraded detection success rate ordetection performance is experienced when using CPC, minimum HS-SCCH orE-HICH power levels can be tuned, this is further described in the EngineeringGuidelines in Power Control.

By using the observability of the CPC counters, the average number of CPCusers together with the average time spent on CELL_DCH can be observedand analyzed. The UE battery gains related to CPC can be estimated byobserving the UL activity factor on per slot basis for the CPC users.

6 Parameters

This section describes all parameters that the operator can configure to controlWCDMA RAN CPC. Further parameter information can be found in RadioNetwork Parameters.

featureStateCpcControls the feature state (Activated/Deactivated) forCPC (the Enhanced Downlink Reception, CPC andEnhanced Uplink Transmission, CPC features) per cell,indicating whether the feature is activated or deactivatedper cell

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CPC

hsdschInactivityTimerCpcTime after which a CPC-activated connection withlow throughput is switched down from CELL_DCH toCELL_FACH.

This parameter is used instead of parameterhsdschInactivityTimer for CPC-activatedconnections.

cellCapabilityControl.cpcSupportControls the cell capabilities used when the externalRNC represented by this IurLink acts as Drift RadioNetwork Controller (DRNC).

These flags override the value of the cellCapabilityfor the ExternalUtranCells under this IurLink. Theparameter cellCapabilityControl.cpcSupportshall be set to "OFF" in this release.

cellCapability.cpcSupportControls whether CPC is activated in externalUTRAN cells. The setting of parametercellCapability.cpcSupport does notmatter in this release.

6.1 Range and Default Values

This section describes the value ranges and default values for the parametersthat the operator can configure to control WCDMA RAN CPC (see Table 2).

Table 2 CPC Parameter Ranges and Default Values

Parameter Name Default Value Value range Unit

featureStateCpc Deactivated Activated orDeactivated

N/A

hsdschInactivityTimerCpc 50 0... 1000 0.1 s

cellCapabilityControl.cpcSupport

OFF ON or OFF N/A

cellCapability.cpcSupport OFF ON or OFF N/A

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Reference List

Reference List

[1] Channel Switching, 82/1553-HSD 101 02

[2] Enhanced UL Scheduler, 112/1553-HSD 101 02

[3] HSDPA User Plane, 93/1553-HSD 101 02

[4] Power Control, 80/1553-HSD 101 02

[5] Technical Specification, Physical Layer Procedures (FDD), 3GPP TS25.214

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