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Title: Overview of Extended Cell High Rate Packet Data

Abstract: This contribution provides an overview of Extended Cell High Rate Packet Data (xHRPD) system

Source: Rhys W. Robinson (Rhys.Robinson@terrestar.com).

TerreStar Networks

Sourabh Gupta (Sourabh.gupta@ico.com)

DBSD North America (ICO)

Eric Jacks (Eric.Jacks@LightSquared.com)

LightSquared Communications

Alok Gupta (alokg@qualcomm.com)Qualcomm Incorporated

Date: September 14, 2011

Recommendation: FYINotice

LightSquared Communications, DBSD North America (ICO), TerreStar Networks, and QUALCOMM Incorporated grant a free, irrevocable license to 3GPP2 and its Organizational Partners to incorporate text or other copyrightable material contained in the contribution and any modifications thereof in the creation of 3GPP2 publications; to copyright and sell in Organizational Partner’s name any Organizational Partner’s standards publication even though it may include all or portions of this contribution; and at the Organizational Partner’s sole discretion to permit others to reproduce in whole or in part such contribution or the resulting Organizational Partner’s standards publication. LightSquared Communications, DBSD North America (ICO), TerreStar Networks, and QUALCOMM Incorporated are also willing to grant licenses under such contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for purpose of practicing an Organizational Partner’s standard which incorporates this contribution.

This document has been prepared by LightSquared Communications, DBSD North America (ICO), TerreStar Networks, and QUALCOMM Incorporated to assist the development of specifications by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to be construed as a binding proposal on LightSquared Communications, DBSD North America (ICO), or QUALCOMM Incorporated. LightSquared Communications, DBSD North America (ICO), TerreStar Networks, and QUALCOMM Incorporated specifically reserve the right to amend or modify the material contained herein and nothing herein shall be construed as conferring or offering licenses or rights with respect to any intellectual property of LightSquared Communications, DBSD North America (ICO), TerreStar Networks, or QUALCOMM Incorporated other than provided in the copyright statement above.

Overview of Extended Cell High Rate Packet Data (xHRPD)

3

Outline

• Overview of xHRPD • Physical Layer • MAC and Signaling Layers

4

Overview of xHRPD

5

Background of xHRPD

• Extended Cell HRPD (xHRPD) is an HRPD system adapted to the limited link budget environment

• xHRPD can enable many new services/applications Satellite terrestrial hybrid networks: MSS/ATC

Allow a handset with the same form factor as existing cellular phones to operate in both mobile satellite system (MSS) and ancillary terrestrial component (ATC)

Machine to Machine (M2M) Relax PA requirementsAllow higher in-building losses Reach distant telemetry devices

6

Operation Environment of xHRPD

• Limited link budgetFor example, geostationary satellite path loss is approximately 190

dB

• Long round trip path delay (satellite link) Around 500 ms or longer for GEO satellite

• Large cell For satellite system, the beam (cell) diameter can be as large as

1000 kmLarge signal delay variation exists within a cell

Likely to have highly overlapped cell coverage May need to support more terminals in an extended cell than a

typical terrestrial HPRD cell

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Main Features of xHRPD

• Supported services Low rate voice service: VOIP

Support fixed rate 2kbps vocoder Low rate mobile data service Medium data rates for “big” terminals Broadcast

• New reverse link to maximize reverse link margin

• Minimum changes to the HRPD forward link and upper layers

• No support for active handoff between different extended cells

8

Physical Layer

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Main Features

• Narrowband reverse link to maximize link margin New lower data rates

RL lowest data ratesHRPD : 9.6 kbps for Access and 4.8 kbps for TrafficxHRPD : 2.4 kbps for Access and 640 bps for Traffic

Improve link efficiency for small packets Better coding Reduce overheads (CRC, tail bits, header, etc.)

• Forward link changes mostly in the MAC channel• MAC channels

Adaptation to the longer path delay and lower SINR environment

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Reverse Link Narrowband Channelization

• Divide the 1.25 MHz CDMA spectrum into 192 narrowband FDM (frequency division multiplexing) channels Each channel bandwidth is 6.4 kHz

192 x 6.4 kHz = 1.2288 MHz

• Flexible bandwidth assignment depending on terminal type and system load A terminal can be assigned one or two FDM channels

1 channel: 6.4 kHz bandwidth, 5.6k symbol rate 2 channels: 12.8 kHz bandwidth, 11.2k symbol rate

Always single carrier transmission Contiguous allocation required for 2 channel assignment

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Reverse Link Channel Structure

Differences from HRPD:

• Removed channels: Auxiliary Pilot, ACK, Data Source Control (DSC)

• Data Rate Control (DRC) channel replaced by (FL) Channel Quality Indicator (CQI) channel which is used for sending DRC-like information but without DRC cover

Traffic

Reverse

Medium Access Control

Data

ReverseRate

Indicator

ChannelQuality

Indicator

Access

Data PilotPilot

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Reverse Link Frame Structure

• Basic RL transmission time unit: 20 ms frame

To accommodate vocoder frame duration. Different from the current 26.67 ms HRPD frame duration

• Data, pilot and MAC (RRI and CQI) symbols are time division multiplexed (TDM) into one frame

1 FDM channel assignment case. (BW=6.4 k, sym rate =5.6 k)

2 FDM channel assignment case. (BW=12.8 k, sym rate =11.2 k)

2RRI

2Data

1Pilot

7Data

1Pilot

7Data

1Pilot

7Data

1Pilot

7Data

2CQI

1Data

1Pilot

1Pilot

7Data

4RRI

1Pilot

7Data

3CQI

1Pilot

1Pilot

7Data

1Pilot

7Data

1Pilot

7Data

1Pilot

6Data

1CQI

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RL Data Rate Sets

• Narrowband RL supports 9 data rates, separated into 3 Rate Sets Rate Set 0: 640 bps, 1280 bps

Used for 1 FDM channel assignment Rate Set I: 2.4, 4.8, 9.6 kbps

Used for both 1 and 2 FDM channel assignments Rate Set 2: 12.8, 19.2, 25.6, 38.4kbps

Used for 2 FDM channel assignment

• VOIP traffic needs at least 2.4 kbps, thus can only be sent using Rate Set 1 or 2

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Two Types of RL Physical Layer Packet • Voice dedicated packet

Optimized for vocoder payload 2 kbps vocoder generates 40 bits every 20 msPlus 8-bits CRC, it can fit nicely into the 2.4 kbps channel

Always single frame packet ZERO protocol header/trailer from MAC and layers above

The header/trailer is reconstructed at the receiver end Can tolerate higher packet error decision rate so protected by weaker

CRC8-bit CRC for 48 bits voice packet

• Data packet: normal HRPD physical layer packet Used for sending data and signaling Can last multiple frames Has regular protocol header/trailer Shall be protected by 16-bit CRC

• Packet type is blindly determined at the receiver by testing different CRCs

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Encoding, Modulation, Interleaving & Puncturing

• Two encoding methods Convolutional encoding

Basic code: ¼ rate maximum hamming distance code with constraint length of 11

Tailbiting convolutional code for small size (48 and 96 bits) data block

No tail bits overhead! Regular convolutional code with 10 bits tail for 192 bit data block

Turbo encoding for larger size packet (>192 bits)

Same turbo encoder as in HRPD

• ModulationBPSK, QPSK, 8PSK, 16-QAM and 64-QAM

• Interleaver and puncturing methods similar to those in HRPD Interleaver based code rate puncturing

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PN Covering and Baseband Filtering

• PN quadrature covering Benefits from PN covering

Scrambling, interference averaging PN sequences generation

Common short PNs covered by masks

• Baseband filtering Square-root raised-cosine pulse shaping filter with 14% excess

bandwidth

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Access Channel

• Narrowband Access Channel Dramatically reduced PN search space

A 1000km diameter cell has around 6ms round trip delay variation => more than 7000 CDMA chips PN search space=> only 34 narrowband symbols

Link budget advantage

• Collision is a severe issue for narrowband access channel Operation: Slotted Aloha Many access channel operation parameters need to be updated

• Currently the standard supports only one data rate: 2.4kbps

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Summary of RL Physical Layer Changes• Narrowband reverse traffic and access channel

New 6.4 kHz narrowband reverse channel design tailored for limited link budget environment to maximize link margin

Flexible assignment of narrowband frequency channels One or two adjacent channels can be assigned, depending on terminal type and system load

• New data rates and transmission formats Normal data rates: 2.4 kbps to 38.4 kbps Also supports two low data rates 640 bps and 1.28 kbps for low rate data

service

• New voice dedicated physical layer packet format

• Tail-biting convolution code for small size packet

• MAC channel adaptation to long delay and low SINR environment

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Forward Link Physical Layer of xHRPD

• Essentially the same as HRPD Rev A. Forward Link

• All changes are in the MAC channel

Disabled in xHRPD Modified for xHRPD

New addition in xHRPD

MediumAccessControl

Pilot Traffic

ReverseActivity ARQ

Forward

Control

DRCLock Reverse Power

Control

Reverse Frequency

Control

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Disabled FL MAC Channels

• Reverse Activity Channel Reverse Activity Bit (RAB) is used for reverse link load control in

HRPD Not needed for narrowband RL

• DRCLock Channel Transmits a RL quality indication used by the AT for Forward link

serving sector selection Not needed for the GMSA system since no soft handoff is

supported

• ARQ Channel Hybrid ARQ not feasible due to long round trip path delay

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RL Power and Frequency Control Channels

• Modified RL Power Control (RPC) channel RL power control rate can be slowed down significantly due to the

presence of long path delayHRPD: 150 bps power control rate xHRPD: 50bps (1 power control bit per 20 ms RL frame received)

• New RL Frequency Control (RFC) channel May cause significant inter-channel interference if narrowband RL

signal has large frequency offset Open loop frequency error correction is recommended but may

not be enough Closed loop RL frequency error control is needed

Very slow frequency correction rate is needed. The control signal rate can be set to 50 bps

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MAC and Signaling Layers

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xHRPD MAC/Signaling Layer

• xHRPD preserves HRPD protocol stack • Maintains EMPA for multi-flow differentiated QoS• However, changes in the following vs. HRPD –

Reverse Link Physical Layer Packet Encapsulation EMPA – Zero-Header Compression Protocol RLP timers Changes Session Configuration Changes Connection Layer Signaling Changes New RTCMAC for the new Narrowband Physical Layer ACMAC Changes

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Reverse Link Voice-Dedicated Packet Encapsulation

Decapsulation of 48-bit Voice-Dedicated Physical Layer Frame

RLP payload (40 bits)

MAC payload (40 bits) CRC (8 bits)

VoIP payload (40 bits)RTP/IP/UDP header(20 bytes)

VoIP payload (40 bits)

Zero-Header Compression: RTP/UDP/IP header removed

RLP Packet

48-bit Voice-Dedicated Physical Layer Frame Transmitted

VoIP RTP packet – 200 bits

Quarter Rate Vocoder Frame Encapsulation over 48-bit Voice-Dedicated Physical Layer Frame

Voice Data (40 bits)

MAC payload (40 bits)

RTCMAC layer

RL Demod interface reconstructs MAC/Stream/RLP header (formatA connection packet is assumed)

48-bit Voice-Dedicated Physical Layer Frame Received

Coneection/Stream Layer

CRC (8 bits)

Voice Data (40 bits)

RLP header(14 bits)

MAC trailer(8 bits)

stream header(2 bits)

RLP header(14 bits)

Stream header(2 bits)

Voice data (40 bits)RLP header

(14 bits)

EMPA/Header Decompressor reconstructsRTP/UDP/IP headers

RLP Layerdata (40 bits)

data (40 bits)RTP/UDP/IP header

Stream/Connection Layer bypassed

No RLP header

xHRPD Airlink

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Reverse Link Data-Only Packet Encapsulation (same as HRPD)

Payload 232 bits

MAC payload (232 bits)MAC Trailer

(2 bits)

Signaling data (HDR, SIP, PPP)

Payload 230 bits Stream Layer

Connection Layer Format A

Physical Layer Data FrameFCS+Tail

(16+6 bits)

2bits

6bits Payload 224 bits

Signaling data is divided into multiple RLP packets

RLP Layer

Payload 224 bits

MAC payload (232 bits)MAC Trailer

(2 bits)

Signaling data (HDR, SIP, PPP)

Payload 222 bits Stream Layer

Connection Layer Format B

Physical Layer Data Frame

FCS + Tail(16+6 bits)

Header8bits

2bits

6bits Payload 216 bits

Signaling data is divided into multiple RLP packets

RLP Layer

256-bit frame format Connection layer format B

256-bit frame format Connection layer format A

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Reverse Link Packet Concurrent Voice and Data Encapsulation

Connection layer payload

Stream layer payload

VoIP data

RLP payload

Voice data (40 bits)RTP/UDP/IP header

RLP header(14 bits)

Stream header(2 bits)

Connection Header (8 bits)

Connection layer payload

Stream layer payload

RLP payload

Non-VoIP data

RLP header(14 bits)

Stream header(2 bits)

Connection layerHeader (8 bits)

MAC payload 160 bits

Connection layer padding. . .

MAC trailer (8 bits)

Non-VoIP data

VoIP header removed before passing to RLP

MAC payload 168 bits 16-bit CRC

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EMPA – Zero-Header Compression Protocol

AT

UDP/IP/

PPP

Route protocol

VoIP Client Application

SIP

SIP

RLP

RTP

RTP

RLP

AN

ROHCU-mode

Compressor

Flow protocol Flow protocol

Route protocol

ROHCU-mode

Decompressor

Either Flow Protocol or Route Protocol of EMPA can be configured as zero-header compression protocol similar to RoHC

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xHRPD RLP timers Changes

• The following timers need to be adjusted to account for long path delay MaxAbort Timer Abort Timer

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xHRPD Session Configuration

• New xHRPD Protocol Subtypes Physical Layer RTCMAC ACMAC FTCMAC Idle State Route Update

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xHRPD Connection Layer Changes

• For Reverse Link, a new Channel Record format is introduced for xHRPD to define reverse narrowband channel

• The existing HRPD Channel Record format is applicable for Forward Link Channel

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xHRPD Connection Layer Changes

• Connection Request Message (Idle State Protocol) New field added to indicate narrowband channel bandwidth

requested by AT

• Traffic Channel Assignment Message HRPD channel record indicates only the forward link channel

number New reverse channel record to indicate the reverse link

narrowband channel assigned to the AT

• RouteUpdate Message Channel record contains only forward link channel number Initial CQI

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xHRPD RTCMAC

• Supports narrowband physical layer subtype• Supports multiflow QoS• Optimized for voice packet flow by adding no RLP/MAC

header overhead and tightly-fit voice packet emanating out of the vocoder into voice-dedicated physical layer packet

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xHRPD ACMAC Protocol

• Physical Layer Format Used 192-bit physical layer packet for transmitting over 2.4 kbps

channel

• Access Parameter Message Changes AccessChannelCount: Indicates the number of narrowband

access channels available in a sector NarrowbandChannels: Specifies narrow band access channels AccessChannelOffset: Indicates access offset for each access

channel

• Access Probe Timers Adjusted for long path delay

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xHRPD FTCMAC Protocol

• Based on HRPD FTCMAC

• Hybrid ARQ (H-ARQ) feature has been disabled on the xHRPD protocol to account for the long path delays

• Fixed rate state removed