Title:Framework proposal for LBC mode of Rev C Abstract:This contribution presents a joint proposal...

Title: Framework proposal for LBC mode of Rev C

Abstract: This contribution presents a joint proposal for loosely backward

compatible FDD mode of HRPD Rev C

Source: China Unicom, Huawei Technologies, KDDI, Lucent

Technologies, Motorola, Nortel Networks, QUALCOMM

Incorporated, RITT, Samsung Electronics, ZTE

Date: June 26, 2006

Recommendation: Review and adopt

NoticeContributors 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. Contributors 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 Contributors 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 Contributors 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 Contributors other than provided in the copyright statement above.

Miyazaki City, Japan

C30-20060626-054

2

System Overview (1)

System designed for robust mobile broadband access• Rev C applies to both existing PCS and cellular deployments as well as

new Greenfield applications

• Broadband wireless system optimized for high spectral efficiency and short latencies using advanced modulation, link adaptation and multi-antenna transmission techniques

• Features necessary for mobile operation such as fast handoff, fast power control, and inter-sector interference management are integrated into the design

3

System Overview (2)

Adaptive coding and modulation with resource adaptive synchronous H-ARQ and turbo coding

• Modulation includes: QPSK, 16QAM, and 64QAM

Short HARQ retransmission latency• Approximately 5ms on Forward and Reverse Link

OFDMA Forward Link with MIMO support• Single codeword MIMO with closed loop rate & rank adaptation • Multi-codeword (layered) MIMO with per-layer rate adaptation• Peak rate over 260 Mbps in 20 MHz Forward Link

Efficient frequency diversity and frequency selective Forward Link transmission• Multiplexing of DRCH and BH

Forward Link precoding & SDMA• MISO / MIMO closed loop precoding with low-rate feedback• Combined precoding and space division multiple access

Subband scheduling• Enhanced performance on Forward & Reverse Link • Multi-user diversity gains for latency sensitive traffic

4

System Overview (3)

Quasi-Orthogonal Reverse Link• Orthogonal transmission based on OFDMA• Non-orthogonal transmission with Layer Superposed OFDMA (LS-OFDMA)

Pre-coded CDMA Reverse Link segment • Statistical multiplexing of various Reverse Link control channels • Optional support for low-rate data transmissions, subject to AT capabilities• Fast access with reduced overhead and fast request• Broadband reference for power control and sub-band scheduling• Efficient handoff support

Optimized throughput / fairness tradeoff through power control• Distributed power control based on other cell interference

Interference management through fractional frequency reuse• Improved coverage and edge user performance• Dynamic fractional frequency reuse to optimize bandwidth utilization

Bandwidth Flexibility• Scalable design with fine bandwidth granularity from 1.25 to 20 MHz

Maximize reuse of existing upper layer protocols and layering structure

5

System Overview (4)

Efficient handoff support • support for FL softer handoff group selection to improve edge user performance

Intra-cell SFN transmission to enhance FL traffic and signaling • SFN transmission to softer handoff users on FL• SFN transmission of quick paging channel• SFN transmission of regular pages

Optional frequency reuse on broadcast overhead channels

Rotational OFDM optional for AT and AN

DFT-Spread OFDMA Reverse link under study

6

OFDM Numerology

• Five basic FFT sizes and chip rates • Different operating bandwidths supported through flexible use of guard carriers

• Following is under study• Larger sub-carrier spacing considering various frequency bands with appropriate speeds

Parameter 128 pt FFT 256 pt FFT 512 pt FFT 1024 pt FFT 2048 pt FFT Units

Chip rate 1.2288 2.4576 4.9152 9.8304 19.6608 Mcps

Subcarrier spacing

9.6 9.6 9.6 9.6 9.6 kHz

Bandwidth of Operation

≤ 1.25 1.25 - 2.5 2.5 - 5 5 - 10 10 - 20 MHz

Guard carriersDepends on bandwidth

Depends on bandwidth




Cyclic Prefix 6.51 – 26.04 6.51 – 26.04 6.51 – 26.04 6.51 – 26.04 6.51 – 26.04 μs

Windowing Duration

3.26 3.26 3.26 3.26 3.26 μs

OFDM Symbol Duration

(For 6.51 μ s CP)113.93 113.93 113.93 113.93 113.93 μs

7

FDD Superframe Structure

AN

AT

FL Superframe

PHY Frame

Superframe Preamble

RL Superframe

PHY Frame

PHY Frame

PHY Frame

PHY FramePHY

FramePHY

FramePHY

Frame

PHY Frame

PHY Frame

PHY Frame

PHY Frame

…

…

0 1 2 3 22 23

0 1 2 3 22 23

PHY Frame

Superframe Preamble

PHY Frame

PHY Frame

PHY Frame

PHY FramePHY

FramePHY

FramePHY

Frame

…

…

24 25 26 27

24 25 26 27

time

FL PHYFrame Index

RL PHYFrame Index

A Superframe consist of a superframe preamble followed by 24 PHY Frames for FFT sizes of 256 and larger

• For a 128 point FFT, the superframe consists of a superframe preamble followed by 48 PHY Frames

Each PHY Frame consists of 8 OFDM symbols.

First RL PHY Frame in a superframe is elongated so as to align forward and reverse links.

Superframe preamble carries acquisition pilots and overhead channels for initial acquisition.

• Superframe preamble consists of 8 OFDM symbols for FFT sizes of 512 and higher, 16 OFDM symbols for FFT size of 256, and 32 OFDM symbols for FFT of size 128

8

FDD Forward Link Timeline: under study

Assignment + Data

TransmissionAN

AT

0 1 2 3 4 5 6

ACK Transmission

Assignment + Data (Re)

Transmission

Frame Duration (TTI)

8 OFDM Symbols

Demod + Decode Time16 OFDM Symbols

ACK Decode + Scheduling + Data Encoding

Time16 OFDM Symbols

Retransmission Interval48 OFDM Symbols

(Approximately 5.5ms)

9

FDD Reverse Link Timeline: under study


Assignment Transmission

AN

AT

0 1 2 3 4 5 6 7

Data Transmission

Assignment, ACK

Transmission


8 OFDM Symbols

Demod + Decode + Scheduling + SSCH Encoding16 OFDM Symbols


8

Assignment Decode+ Data

Encode Time16 OFDM

Symbols

Data

(Re)Transmission

9

Assignment Decode+ Data

Encode Time16 OFDM

Symbols

• Above timeline applies to OFDMA data transmission

• Retransmission timeline for CDMA data is under study

10



Assignment + Data

TransmissionAN

AT

0 1 2 3 4 5

ACK Transmission

Data (Re)Transmission

Frame Duration ( TTI )

8 OFDM Symbols


ACK Decode + Scheduling + Data Encoding

Time8 OFDM Symbols

( Approximately 4.55ms )


AN

AT

0 1 2 3 4 5 6 7

Data Transmission

Assignment , ACK

Transmission

Frame Duration ( TTI )

8 OFDM Symbols

Demod + Decode + Scheduling + SSCH Encoding16 OFDM Symbols


Data ( Re ) Transmis

sion

Assignment Decode

+ Data Encode Time

8 OFDM Symbols

Assignment + ACK Decode

+ Data Encode Time8 OFDM Symbols

FDD Five Interlace Timeline: under study

11

AN

AT



Assignment Data Transmission

0 1 2 3 4 5

ACKTransmission


ACK Decode + Scheduling + Encoding Time16 OFDM Symbols

6 7 8

PHY Frame (TTI)8 OFDM Symbols

Data (Re-) Transmission

AN

AT



Assignment

0 1 2 3 4 5

Demod + Decode + Scheduling + SSCH Encoding Time32 OFDM Symbols

6 7 8

PHY Frame (TTI)8 OFDM Symbols

9 10 11

Data Transmissio

n

Data (Re-) Transmission

AssignmentACK

Transmission

Assignment / ACK Decode + Encoding Time16 OFDM Symbols

Assignment Decode + Encoding Time16 OFDM Symbols

Forward Link

Reverse Link

FDD Eight Interlace Structure

Relaxed timeline – reduced AT / AP complexity

Similar half-duplex eight interlace structure

12

Multiple Interlacing Structures

Multiple frame structures • In addition to the one-slot frame, new frame structure to be added.

• Same signaling mechanism that is used to configure one-slot frames will be extended for new frame structure.

Exact set of structures to be worked out jointly between M and LNQS• For example, in a new structure, a single transmission could consist of two

adjacent PHY Frames

• Retransmission interval would be some multiple of these two PHY Frames, so as to allow sufficient processing time

13

FDD Half-Duplex Superframe Structure

Same as FDD full-duplex except for the following:• Set of PHY Frames divided into two half-duplex interlaces

• FL PHY Frames in one half-duplex interlace correspond to RL PHY Frames in the other half-duplex interlace

• No RL transmission corresponding to the superframe preamble transmission on the FL

• Number of PHY Frames in the superframe for a given FFT size same as in full-duplex operation

• Additional guard time to be inserted between consecutive PHY Frames (not shown in figure)

FL

RL

FL Superframe

PHY Frame

RL Superframe

PHY Frame

PHY Frame

PHY Frame

PHY Frame

PHY Frame

…

…

0 1 11

0 1 11'

PHY Frame

PHY Frame

PHY Frame

PHY Frame

…

…

12 13

12 13

time

FL PHYFrame Index

RL PHYFrame Index

PHY Frame

PHY Frame

PHY Frame

PHY Frame

PHY Frame

PHY Frame

PHY Frame

Superframe Preamble

Superframe Preamble

0' 11' 12' 13'

0'

PHY Frame

12'11

PHY Frame

PHY Frame

Half-duplex interlace 0

Half-duplex interlace 1

PHY Frame

PHY Frame

1'

10'

14

FDD Half-Duplex Forward Link Timeline

FL

RL

0 1 2

Assignment + Data

Transmission

ACK Transmission


8 OFDM Symbols

Assignment/Data Demod + Decode Time

16 OFDM Symbols

ACK Decode + Scheduling + Encoding Time

16 OFDM Symbols



Assignment/ACK+Data (Re)

transmission

3

0 1 2

Assignment + Data

Transmission

Assignment/ACK+Data (Re)

transmission

ACK Transmission

0' 1' 2' 3'

0' 1' 2' 3

15

FDD Half-Duplex Reverse Link Timeline

FL

RL

0 1 2

AssignmentTransmission

Data Transmission


8 OFDM Symbols

Assignment Decode +Data Encode Time16 OFDM Symbols

Demod + Decode + Scheduling + SSCH Encoding Time

16 OFDM Symbols



Assignment, ACK

transmission

3

0 1 2


Assignment, ACK

transmission

Data Transmission

0' 1' 2' 3'

0' 1' 2'

Data (Re)transmiss

ion

Data (Re)transmiss

ion

Assignment/ACK Decode+ Data Encode Time16 OFDM Symbols

3 4 4'3'

4 4' 5

• Above timeline applies to OFDMA data transmission

• Retransmission timeline for CDMA data is under study

16

Half-Duplex Operation

Set of PHY Frames divided into two half-duplex interlaces

FL PHY Frames in one half-duplex interlace correspond to RL PHY Frames in the other half-duplex interlace

Choice of half-duplex interlace: • Terminal picks one of the half-duplex interlaces for access

• Subsequently, the choice of the half-duplex interlace (for a half-duplex terminal) is defined by the assigned MACID

• Odd MACIDs correspond to one half-duplex interlace while even MACIDs correspond to the other half-duplex interlace

• Power control bits for a given MACID are sent only on the corresponding half-duplex interlace

The base station can assign resources to a half-duplex terminal on the half-duplex interlace corresponding to its MACID

The base station can assign resources to a full-duplex terminal on any PHY Frame

17

Resource Management (1)

Resource allocation including rate determination centralized at AP for both forward and reverse links

• For FL, based on FL channel quality reports from AT• For RL, based on measurements of RL channel quality as well as RL feedback

from the AT including resource requests• Network assigns FL and RL resources via Shared Signaling Channel (F-SSCH)• CDMA traffic resource allocation is AT-centric (autonomous) once CDMA traffic

zone has been allocated by the AP

Scheduler goals• Maximize system capacity• Manage QoS requirements such as AT throughput and latency• Maintain fairness across ATs with widely disparate channel qualities• Design ensures that the scheduler has information required to utilize features such

as sub-band scheduling, fractional frequency reuse, precoding, and SDMA to achieve the above goals

• CDMA traffic zone transmissions allow for bursty low bit rate traffic and cell-edge users to communicate without explicitly being scheduled by AP

• CDMA resource allocation is semi-static by the AP• Fast power control enables precise QoS control and slower rate/fairness control

can be enabled with a slow RAB bit.

18

Assignment Management(1/2)

Fundamental unit of assignment is logical subcarrier• A static resource that maps to a

unique physical subcarrier• Mapping of logical subcarriers to physical subcarriers

can change over time (hopping)• Sets of logical subcarriers are specified

using nodes on a channel tree• Each base node addresses 1 channel unit

• Channel unit is 16 tones over 1 PHY Frame (minimum resource allocation unit)

Resource-adaptive synchronous H-ARQ on Forward Link and Reverse Link• Each HARQ transmission follows at a fixed duration after the previous one• If necessary, the resource assigned to a data packet can be changed “starting at

the next HARQ transmission” “for retransmission” using an assignment message• For non-persistent assignment, assignment message is sent for the 1st sub-packet transmis

sion. Assignment message can be sent for sub-sequent sub-packets to change the resource assignment

• For persistent assignment, assignment message is sent for the initial persistent assignment. Assignment message can be sent for retransmission sub-packets to change the resource assignment for retransmission sub-packets. Resources persistently assigned to an AT can be temporarily assigned to other AT using non-persistent assignment message without de-assignment of the persistent assignment, e.g., in case of HARQ early termination (Detailed mechanism is under development). Assignment message can also be sent to override the current persistent assignment.

Logical carriers

nodeChannel Tree

19

Assignment Management(2/2)

Assignments can be persistent or non-persistent• Non-persistent assignments expire after one packet, while persistent

assignments persist until supplemented, decremented, de-assigned or packet loss

• Persistent assignments reduce signaling requirements when multiple users are scheduled simultaneously

• Also can be used to eliminate request latency for RL assignments

• Low-power erasure sequence transmissions used as a keep-alive indication for persistent assignments when no packet is available to send

20

Coding and Modulation

Rate 1/3 convolutional code for block lengths ≤ 128

Rate 1/5 turbo code for block lengths > 128

Code is punctured or repeated to achieve desired code rate.

Synchronous HARQ on both links• Channel interleaver• Based on bit-reversal• Provides almost-regular puncture patterns and good interleaver distance properties

at all code rates

Packet formats• Support the following modulation formats

• QPSK, 8PSK, 16QAM, 64QAM• Support a wide range of spectral efficiencies.

Modulation step-down• At high spectral efficiencies, later HARQ transmissions use lower order

modulations• this avoids repetition of coded bits

• Gains up to 1 dB for later transmissions

21

Forward Link

22

Forward Link Channels

CC MAC FTC MAC

F-pBCH0

F-CPICH

F-pBCH1 F-DCH F-SSCH

F-ACQCH

SS MACMAC

Protocols

PHY Channels

F-OSICHF-AuxPICH

F-DPICH

F-pBCH0 – broadcast channel, carries deployment specific parametersF-pBCH1 – broadcast channel, carries sector specific parametersF-OSICH – broadcast channel, carries indication of inter-sector interferenceF-ACQCH – acquisition channelF-CPICH – common pilot channelF-DPICH – dedicated pilot channelF-AuxPICH – auxiliary common pilot channelF-SSCH – shared signaling channel, carries Forward Link control signalingF-DCH – data (traffic) channelCongestion control channel for CDMA is under study

23

Superframe Preamble Structure

Above picture applies to FFT sizes of 512 and above• For the case of a 256 point FFT, superframe preamble consists of 16 OFDM symbols• For the case of a 128 point FFT, superframe preamble consists of 32 OFDM symbols

Different components of the preamble (pBCH0, pBCH1, TDM pilots) are scaled up equally for the smaller FFT sizes

Preamble occupies ~5MHz (512 subcarriers less guard) in any given superframe

In large deployments (> 5MHz), preamble hops over the entire band• Maintain non-coherent processing efficiency in multi-path channel, gain due to random reuse

Under study: position of preamble and pBCH, configurable length of pBCH, preamble structure: frequency domain mapping of sequences to antennas, number of preamble symbols

OFDM Symbol Index (0-7)

F-pBCH0Cyclic prefix

length,Number of guard sub-carriers etc.

TDM 1 + TDM 2, 3 (F-OSICH)

F-pBCH1Odd superframes: - FL Hopping Structure - FL Pilot Structure - FL Control Chanel Structure - Number of Transmit Antennas - etc.Even superframes: - Quick pages.

24

Synchronization Modes

Semi Synchronous mode• TDM pilots change from superframe to superframe

• Different sectors use offsets of the same sequence

• Requires superframe level synchronization between different sectors

• Symbol/chip level synchronization not required• can be used to improve performance (reduce acquisition time, fast sector

switching, interference estimation etc)

Asynchronous mode• TDM pilots are the same from superframe to superframe

• No synchronization requirement between sectors

25

Three acquisition pilots: TDM1, TDM2 and TDM3

TDM1 is used for initial timing acquisition and coarse frequency offset recovery• occupies one OFDM symbol

TDM1 also carries information assisting in system determination by the AT• TDM1 sequence is fixed across the deployment• sequence is selected according to

• System FFT size: 5 options• {128, 256, 512, 1024, 2048}

• Index of a 5MHz carrier on which this TDM1 is populated• 1 option for {128, 256, 512}, 2 options for 1024 and 4 options for 2048

• One bit indicating whether frequency reuse on pBCH0,1 is used• Total of 18 sequences needed• More information needed to assist in system determination TBD

Use GCL sequences for TDM1• Study item to consider GCL instead of Walsh codes for TDM2 and TDM3

• final decision to be based on performance/complexity tradeoff.

Acquisition Pilot Structure (1)

26

Acquisition Pilot Structure (2)

TDM2 and 3 (F-OSICH or F-IAB) are time-domain sector-dependent sequences • Sequences are chosen to be Walsh sequences of length 1024 with PN scrambling

• Walsh sequences allow for efficient correlations using a Fast Hadamard Transform

• 1024 Walsh sequences allow for 512 different sectors each in semi-synchronous and asynchronous modes

• Different sets of Walsh codes are used in semi-synchronous and asynchronous modes

Time-domain sequences are low PAR sequences which enable power boost for improved acquisition performance in thermal limited regime

Time-domain sequences are still generated using FFT structure• Including CP and windowing

27

Acquisition procedure

Superframe preamble carries channels F-pBCH0 and F-pBCH1• F-pBCH0 carries deployment-wide static parameters like cyclic prefix duration, numb

er of guard carriers, in addition to the superframe index• Required only on initial wakeup, coded over 16 superframes

• F-pBCH1 carries sufficient information to enable the AT to demodulate FL data from the PHY Frames

• Info on FL hopping patterns, pilot structure, control channel structure, transmit antennas, multiplexing modes etc

• This info is transmitted every alternate superframe; other superframes used to carry pages • Remaining overhead information broadcast using a regular data channel in predefine

d superframes• Carries information on RL hopping patterns, channel mapping, transmit powers, power contro

l parameters, access parameters, etc

These channels enable a flexible physical layer• Can configure cyclic prefix, number of antennas, pilot structure, etc• Support FL and RL control channels with flexible overheads, which can be matched t

o the current user loads • Can enable or disable features like sub-band scheduling, FFR etc

28

Quick paging design• single coded packet including quick paging IDs • is part of the superframe preamble

• transmitted every even superframe on F-pBCH1

Intra-cell SFN operation • quick paging channel may be transmitted in SFN by sectors belonging to the same quick paging group • SFN transmission of broadband pilot

Better F-QPCH performance• interference reduction in interference limited scenarios• full diversity advantage: slow and fast fading

SFN quick paging is optional at AN and mandatory at AT

Regular pages are carried on F-DCH, can be sent SFN • AN can reserve resources in the adjacent sectors• AN can serve pages through softer handoff groups

SFN operation for quick paging channel

29

High level design• Enable frequency reuse on F-pBCH0,1 as a deployment-wide feature for sectors in semi-synchronous

acquisition mode, optional at AN • support of frequency reuse on F-pBCH0,1 in semi-synchronous acquisition mode is mandatory at AT• frequency reuse implemented by defining orthogonal hopping sequences associated with sector IDs, hence

allowing for frequency planning • no simultaneous support for frequency reuse on F-pBCH0,1 and SFN paging

• No frequency reuse in asynchronous acquisition mode

Observations • presence of frequency reuse is part of system determination• should limit the number of possible reuse schemes

• reuse 1/7 is the working assumption• details to be figured out

Frequency reuse on F-pBCH0,1

30

Forward Link Channelization

Two types of assignments• Distributed Resource Channel (DRCH)

• Set of tones scattered across entire bandwidth

• Hop permutation maps assigned hop ports to frequency

• Hop permutation changes every OFDM symbol

• Channel and interference estimation based on broadband common pilot

• Block Resource Channel (BRCH)• Set of tiles scattered across entire bandwidth

• one tile consists of 8 contiguous OFDM symbols and 16 contiguous tones

• Hop permutation maps assigned hop ports to tiles in frequency; fixed for duration of PHY Frame

• Independent hopping across sectors

• Localized channel and interference estimation over every tile based on a dedicated pilot

• Both types of assignments coexist in each FL PHY Frame

31

Distributed Resource Channel

Total T useful sub-carriers in an OFDM symbol are divided into N groups.

Each group consists of regularly spaced T/N sub-carriers.

FL PHY Frame

(16, 0)

(16, 8)

AT A, DRCH

time

freq

subcarrier

AT B, DRCH

DRCH ( 16 , 0 )

DRCH ( 16 , 8 )

time

freq

sub - carrier

Channelization for STBC support

32

8 OFDM symbols

16 ton

es

Format 1 à 24 pilots

8 OFDM symbols

16 ton

es


Pilot symbolData symbol


8 OFDM symbols

16 ton

es

clustercluster

SIMO + MIMO (rank ≤3) MIMO (rank = 4)High delay spread

Block Hopping: FFT size ≥ 512

……

..

……

..

……

..

……

..

16 sub-carriers

Data symbol

F-DPICH (Format 1)

F-DPICH (Format 0)

F-DPICH (Format 2)

OFDM symbol

Frequency

8 OFDM symbols

User 3

User 2

User 1

User 2

User 2

User 1

Pilot patterns• Enough “looks” to capture time & frequency selectivity• MIMO support orthogonal overlapped pilot sequences over each contiguous pilot

cluster • Three patterns trade-off pilot overhead with support for MIMO and high delay spread

channels• Pilot pattern indicated through packet format• It can be further optimized with evaluation results

Pilots and data symbols within block undergo the same transmit processing

Pilot overhead (identical for SIMO and MIMO)• Format 0 14.06 %; Formats 1,2 18.75 %

Efficient support for• Advanced multi-antenna techniques: MIMO, precoding, SDMA• Interference estimation and spatial interference nulling

33

8 OFDM symbols




8 OFDM symbols

8 to

nes cluster

cluster

SIMO + MIMO (rank ≤3) High delay spread

8 to

nes

Block Hopping: FFT size < 512

……

..

……

..

……

..…

…..

8 sub-carriers

Data symbol

F-DPICH (Format 0)

F-DPICH (Format 1)

Frequency

User 1

8 OFDM symbols

User 3

User 2

User 1

User 4

Two tiles of the same minimum assignment

Minimum allocation of 16 tones

• Consists of two non-contiguous tiles of 8 tones

• Allows for better diversity in small bandwidths

• Reduces minimum signaling overhead / granularity without loss in diversity

• shared signaling overhead in units of minimum traffic allocation

Pilot patterns support up to third order MIMO / SDMA and highly frequency selective channels

• Formats 0,1 18.75 % overhead

• It can be further optimized with evaluation results

34

Multiplexing of DRCH and Block Hopping (1)

DRCH and Block Hopping assignments coexist in the same PHY Frame

Two modes of multiplexing these types of assignments

Mode 1: DRCH punctures BH • Overhead channel indicates how many DRCHs are used so that ATs know th

e puncturing pattern • Common pilot is used over entire band

• Common and auxiliary pilot placed on equi-spaced tones both in frequency and time domain

• Pilot staggering is used• Common and auxiliary pilots are time and frequency multiplexed• The density of auxiliary pilots can be further optimized based on performance evalu

ation

• Support by the AT for an assignment that includes both DRCH elements and BH elements to the same AT is TBD

• Additional dedicated pilot for BH is TBD

35


Mode 2: DRCH and BH are only used on different subbands• Overhead channel indicates which subbands are in DRCH and which subba

nds are in BH. Size of a subband is configurable by the BS through overhead channel.

• Common pilot is used for DRCH subband• Common and auxiliary pilot placed on equi-spaced tones both in frequency and ti

me domain• Pilot staggering is used• Common and auxiliary pilots are time and frequency multiplexed• The density of auxiliary pilots can be further optimized based on performance eval

uation

• Dedicated pilot is used for BH subband• It can be further optimized with evaluation results.

• Support for an assignment (or a set of simultaneous assignments) that includes both DRCH elements and BH elements to the same AT is optional at the AT

36


Mode 1 Mode 2

BH

CPICH

DRCH

DPICH

37

Forward Link Control Channels FL control design

• FDM channel present in each PHY Frame• Variable resource allocation

• Minimum of 2 channel units for FFT sizes of 128 and 256• Minimum of 3 channel units for FFT sizes of 512 and larger• Granularity of 1 channel unit• In 5MHz, minimum overhead of 10% with increment of 3.3%

• Specific channels• Shared signaling channel (F-SSCH)• Acknowledgement channel (F-ACKCH)• Power control channel (F-PCCH)• Fast other sector interference channel (F-FOSICH)• Pilot quality indicator channel (F-PQICH)• Need for Reverse Link Congestion Control channel under study

• Unicast signaling enables overhead minimization particularly when targeting users with widely varying channel quality

• Under study is grouped signaling and encoding for efficient resource management (especially VoIP)

• Flexible overhead• Quasi-static bandwidth overhead • Flexible power overhead, adjusted every PHY Frame• Allows the system to tailor the overhead required for signaling for a variety of usage scenarios• No power overhead wasted when signaling needs change rapidly

38

Shared signaling channel

Carries a set of encoded and CRC protected blocks for assignments

(F/R)LAB = Forward/Reverse Link Assignment Block• Sends assignment to a user, indicating the physical resources assigned (subcarriers)

and the modulation/coding/pilot structure for use• Both persistent and non-persistent assignments supported • Supplemental assignments supported• Support for Resource Adaptive HARQ – reassignment of resources during a

continuing packet transmission

Access Grant Block• Transmitted in response to (and scrambled by) a detected access sequence• Provides a user with fine RL timing, a MACID to identify the user, and an initial

channel assignment

MIMO Assignment Blocks• Assign resources to MIMO users• Supports single codeword MIMO assignments providing PF and the number of layers

to transmit• Support multi-codeword MIMO assignments: provides independent PF per codeword

39

Other Forward Link control channels Acknowledgement Channel

• Carries ACKs in response to RL traffic (for ACKing both OFDMA and CDMA RL traffic) • ACKs for OFDMA channelized based on RL channel tree, with an ACK channel

provided for each minimum sized channel available• Additional ACK resources are provided for users operating on CDMA traffic segments• ACKs are encoded over a number of modulation symbols that are placed at different frequencies

to provide channel and interference diversity. Pre-coded ACK transmission is under study

Power Control Channel• Carries commands for closed loop control of reverse link transmit power• Control rate of ~180 Hz

• Faster control rate is under study

Fast other sector interference channel for OFDMA traffic• Carries three-state other sector interference indication• Broadcast every FL PHY Frame• Configurable penetration depth

Pilot quality indicator channel• Indicates reverse link strength of a given AT • Sent every ~50Hz • Used for handoff and power control

Possible support of slow RAB bit for CDMA traffic

40

Voice over IP (1/4)

Basic Design• Group VoIP users together and assign the group a set of shared time-frequency

resource• Two forms of statistical multiplexing possible

• Between group members

• Between initial and subsequent transmissions

• Unused portion of the shared time-frequency resource can be temporarily assigned to other non-VoIP users

• Minimize control channel overhead• Control channel overhead can be divided into two parts

• Call setup messages

• Overhead minimization less crucial

• Group users and address them (allocate resources, etc.) with a group ID

• Frame by frame messages

• Overhead minimization crucial

• Bitmap signaling is used to trunk resources with minimum control

41

Voice over IP (2/4)

2 contiguous slots are concatenated to form a VoIP frame• Transmissions at ~6 ms intervals allow up to ~3 transmissions per vocoder frame (20 ms)

without additional delay

ATs are:• Assigned resources using bitmap signaling

• Group would be assigned a set of resources persistently. • Bitmap signaling is used to determine the exact resources in each group. • Bitmap signaling is used for first and subsequent retransmissions.• Persistent resource can be assigned for first transmission (under study)• A first bitmap is used to indicate which ATs are being served in each voice frame, where each AT

corresponds to a location in the bitmap• A second bitmap may be used to indicate number of assigned resources and/or MCS. • Assigned an ACK position based upon relative position in first bitmap Allows ACKs to be time-

multiplexed.

42

Voice over IP (3/4)

ATs are placed into groups (with possible different MCS, e.g., QPSK group, 16-QAM group, etc)

• The same GroupID is assigned to every AT in the group• The GroupID can be used to control the entire group at once, e.g. change the set of shared

time-frequency resources

• The group is assigned a set of shared time-frequency resources

• Each AT is assigned a unique location within group.

• Each AT is assigned an interlace offset indicating in which frame its first transmission will occur

• 1/3 of ATs in the group are assigned to each of the three interlace offsets

43

AT0

Time (slots)

DR

CH

In

de

x

AT2

AT5 AT4

AT5 AT6

AT9 AT8

AT10 AT11

AT16 AT114

AT16 AT19

AT23 AT22

1 0 1 0 1 1 1 0

0 1 2 3 4 5 6 7

1 1 1 1 0 0 1 0

8 9 10 11 12 13 14 15

1 0 0 1 0 0 1 1

16 17 18 19 20 21 22 23

0 0 0 1 0 0 0 0 0 0 1 0 0

Bitmap 1 indicates active users

Bitmap 2, if used, indicates number of resources allocated

to each active user (0=1 resource, 1 = 2 resources)

Set of shared resources is 8

DRCH by 2 time slots. Each user determines its

allocation based on the allocations for all users with a smaller bitmap

position.

Voice over IP (4/4)

24 ATs assigned to this group, with locations 0-23 Wrapping pattern

indicates resource ordering

0

44

Forward Link Packet Formats

Packet formats 10 - 15 are non-decodable at the 1st transmission: allow for high spectral efficiency at target termination

1

Modulation order for each transmission

Packet Format Index

Spectral efficiency on 1st trans-mission

Spectral efficiency on 2nd trans-mission

Max number of trans-missions 1 2 3 4 5 6

0 0.2 -- 6 2 2 2 2 2 2

1 0.5 -- 6 2 2 2 2 2 2

2 1.0 -- 6 2 2 2 2 2 2

3 1.5 -- 6 3 2 2 2 2 2

4 2.0 -- 6 4 3 3 3 3 3

5 2.5 -- 6 6 4 4 4 4 4

6 3.0 -- 6 6 4 4 4 4 4

7 4.0 -- 6 6 6 4 4 4 4

8 5.0 -- 6 6 6 4 4 4 4

9 6.0 3.0 6 6 6 4 4 4 4

10 non-decodable 3.5 6 6 6 4 4 4 4

11 non-decodable 4.0 6 6 6 6 4 4 4

12 non-decodable 4.5 6 6 6 6 4 4 4

13 non-decodable 5.0 6 6 6 6 6 4 4

14 non-decodable 5.5 6 6 6 6 6 4 4

15 NULL NULL

2

45

MIMO Design

Complete OFDMA/MIMO design taking in consideration the following:• HARQ• Rate prediction• Channel estimation• Feedback overhead• Spatial correlation effects• MIMO complexity• Mobility

• Up to 120Km/hr and graceful degradation afterwards

• Simultaneously support both SISO and MIMO users

46

Design Philosophy

Definitions:

• Number of physical antennas: Mt and is fixed

• Number of effective antennas: Me ≤ Mt

• Spatial multiplexing order (rank) M ≤ Me: The number of modulation symbols (a.k.a. layers) transmitted at a time

The goal is to have a flexible design where the data rate and rank are adapted to channel conditions

Two MIMO modes: SCW & MCW

47

Effective Antenna Signaling

1

eMMx1

FrequencyTone 0 1 Me-M Me-M+1 Me-M+2

Eff

ecti

ve A

nte

nn

as

1

t e

e

M M

M

U

u u

1

tM

1

eM

The Mt physical antennas are mapped to Me effective antennas through Matrix multiplication

Directions correspond to different columns of the matrix are called effective antennas

SISO is transmitted form the first effective antenna

MIMO is transmitted from all Me effective antennas

Following item is under study• If M layers are transmitted over effective

antennas, each layer is cycled in the tone-space domain

Flexible to support any value

of transmit antennas• Transmitting over the physical antennas is a

special case

This figure is under study

48

SCW Design

Adapting the rate and rank to channel realizations

One PF is transmitted with M modulation symbols transmitted at a time

H-ARQ similar to SISO

Receiver can employ a linear MMSE or more sophisticated detectors

Low complexity if just linear MMSE is employed

Two main RL feedback channels are used:• CQI, preferred rank on the R-CQICH (SCW report)

• ACK-NACK on the R-ACKCH

TurboEncoder

QAMMap

OFDMMod

OFDMMod

OFDMMod

1

2

M

1

2

MT

1

2

MT

Dem

ulti p

l ex e

r

M

AP ReceiverCQI

RatePrediction

PF PF

Eff

ec t

ive

Ant

en

na

Si g

nal

i ng

49

MCW Design

Two main RL feedback channels are used:• CQI per layer on the R-CQICH (MCW report)• ACK-NACK on the R-ACKCH: one bit per

layer

OFDMMod

OFDMMod

OFDMMod

1

2

M

1

2

1

2

Mt

AP ReceiverCQIMe

TurboEncoder

QAMMap

TurboEncoder

QAMMap

TurboEncoder

QAMMap

Mt

CQI1 Rate

Prediction

1st Data Packet

2nd Data Packet

Mth Data Packet

Eff

ect

ive

An

ten

na

Sig

na

ling

Compared to SCW/MMSE: more complex and memory demanding higher throughput and more tolerant to spatial correlation

CQI feedback for each layer, i.e., rate prediction is done per layer

M PFs are simultaneously transmitted

SIC receiver is used to decouple the M layers

Within the maximum number of HARQ transmissions, no new packets are transmitted on the decoded layers. Total power is equally divided on the outstanding layers

50

Precoding & Space Division Multiple Access

RL feedback information in combination with RL pilot may be used for FL beamforming

• Beamforming gain to SIMO users

• Eigenbeamforming gain to MIMO users• Space division multiple access (SDMA)

• Multiple users scheduled on same time-frequency resource

• Users overlapped using beams pre-defined in codebook

• Increased system dimension; adaptive sectorization gain

51

MAC Support

Requirements• Support for precoding with and without SDMA • Scalability with high granularity in resource allocation to modes

Tree design• Channel tree contains multiple sub-trees• One sub-tree per SDMA cluster with one primary sub-tree• Identical hop pattern across sub-trees

Scheduling • Any user scheduled on only one sub-tree• Users scheduled across different sub-trees overlap • Users scheduled within a sub-tree remain orthogonal

52

Reverse Link

53

Reverse Link Channels

R-DCH R-ACH

Physical Layer Channels

R-BFCH R-SFCH R-PICH

R-CQICH R-REQCH R-ACKCH

R-CQICH – Forward Link channel quality indicator channelR-REQCH – requests Reverse Link resources R-BFCH – feedback channel in support of Forward Link precoding and SDMAR-SFCH – feedback channel in support of Forward Link subband schedulingR-PICH – Reverse Link broadband pilot channelR-ACKCH – Reverse Link acknowledgement in support of Forward Link H-ARQR-ACH – Reverse Link access channelR-DCH – Reverse Link data (traffic) channelR-CDCH -- Reverse Link CDMA Data ChannelR-AuxPICH -- Demodulation pilot for CDMA Traffic channel

54

Reverse Link Traffic Transmission Overview

OFDMA and CDMA traffic is frequency multiplexed • Split of CDMA and OFDMA capacity is configurable by the RAN and is sector and AT

specific.• Both CDMA and OFDMA traffic are power controlled.

Multiplexing of CDMA and OFDMA traffic• RL CDMA Traffic Channel

• Used for the transmission of low-rate bursty delay-sensitive services (e.g. VoIP, Gaming etc).

• Supports a limited set of transmission formats.• Support for frequency-domain interference cancellation.• Is supported by fast power control and HARQ and slow distributed scheduling.

• RL OFDMA Traffic Channel• Fully scheduled• Support for quasi-orthogonal multiple antenna operation (QORL) and layered sup

erposed OFDMA (LS-OFDMA)

55

……

..

……

..

……

..

……

..

16 sub-carriers

Data symbol

R-DPICH (Format 0)

OFDM symbol

Frequency

8 OFDM symbols

User 3

User 2

User 1

User 2

User 2

User 1

R-DPICH (Format 1)

Reverse Link OFDMA Traffic 8 OFDM symbols

16 to

nes




8 OFDM symbols

16 to

nes

clustercluster

SIMO + QORL (Q ≤3) High delay spread(SIMO + QORL (Q ≤ 2)

Pilot patterns• Patterns contain enough “looks” to capture time & frequency selectivity• QORL and LS-OFDMA support orthogonal overlapped pilot sequences over each contiguous pilot cluster • Two patterns trade-off pilot overhead with support for QORL and LS-OFDMA and high delay spread channels• Pilot pattern indicated through packet format• Pilots and data symbols within every block undergo the same TX processing• Pilot patterns can be further optimized with evaluation results• The use of resource orthogonal pilots for QORL and LS-OFDMA is under study

Pilot overhead• Format 0 14.06 %; Format 1 18.75 %

Softer handoff support with orthogonal pilot patterns need clarification

Subband hopping and diversity hopping can be multiplexed in a frame

Under study: • Multiple interlaces can have common hopping for better channel estimation

56

Multiplexing diversity and subband hopping

Quasi-static resource partitioning between diversity hopping and subband hopping in units of subbands

• Number of diversity hopping subbands signaled via overhead channel

Logical subbands in diversity hopping mode are mapped to physical resources (tiles) scattered across the entire bandwidth

Logical subbands in subband hopping mode are mapped to physical subbands• Tiles within physical subbands that are punctured by diversity hopping are replaced

by available tiles outside subbands

Number of base nodes per subband is independent on resource partitioning• Preserves interference diversity order irrespective of resource partitioning

Mapping of logical subbands in subband hopping mode to physical subbands differs for different interlaces

• Ensures that all physical subbands are available for subband scheduling

57

Reverse Link CDMA Control Channels (I)

Control mode: • Signals FL channel quality (4 bits) for control and SISO traffic across the band• Signals desired FL serving sector indicator to request FL handoff

Single codeword MIMO: (related with MIMO, detail feedback should be deferred to later)

• Signals FL channel quality (5 bits) and rank for single codeword MIMO

Multi codeword MIMO: (related with MIMO, detail feedback should be deferred to later)

• Occupies two R-CQICH instances• Signals channel quality (4 bits) for each of four MIMO layers (=0 for unused layers)

R-CQICH (Channel Quality Indicator channel)

R-REQCH (Request channel)

Reports FL channel quality in various transmission modes

Indicates FL handoff request

configurable report interval

Indicates buffer level

Indicates maximum number of tones supported with nominal power density

Indicates RL handoff request


58

Reverse Link CDMA Control Channels (II)

R-SFCH (Subband Feedback channel)

R-BFCH (Beamforming Feedback channel)

Enables sub-band scheduling and subband specific channel quality reports• Indicates reported subband index • Indicates subband channel channels quality including the anticipated TX/RX processing: subband scheduling gain, precoding, …

configurable report interval Multiple CQIs can be transmitted in case TPR is available. (example: If RAB is applied and the AT prefers to report them)

Enables pre-coding and space division multiple access (SDMA)


R-PICH (Pilot channel)

Broadband pilot channel to support channel-sensitive transmissions

R-ACH (Access channel) Access preamble for initial access and access based handoff

Access latency with preamble power ramping: 99% tail within 22ms

R-AuxPICH (Auxiliary Pilot channel) Demodulation of CDMA Traffic channel etc.

59

CDMA Control Segment - FDD CDMA control segment statistical multiplexing of various control channels

• Flexible load control by changing persistence of different channels• Overhead reduction for access channel • Broadband pilot to support subband scheduling• Fast cell switching through handoff signaling

Control segment spans a number of subbands over one or more RL interlaces• For half-duplex operation, at least one control segment in each half-duplex interlace• Minimum assignment of one subband (1/24 overhead in 5MHz)• Scalable in units of subbands (1/24 granularity in 5MHz)

Control segment hopping in time• R-CQICH provides power control reference across the entire bandwidth• R-CQICH and R-PICH provide broadband pilot that covers all the bandwidth over time

Modulation• All channels of the control segment use Walsh codes (up to 1024)• Sector specific and, when applicable, MACID specific scrambling • Initial access:

– Set of 1024 Walsh sequences (sector scrambling) partitioned according to F-CPICH strength and buffer level– AT chooses a sequence randomly from the appropriate partition

RL PHY Frame

Tota

l b

and

Control segment: scalable in units of subbands

60

R-ACKCH: FFT size ≥ 512 Used to acknowledge FL H-ARQ transmissions

Present on every RL interlace, linked to the corresponding FL interlace

Channel based R-ACKCH• Every base node of the channel tree maps to a 1-bit R-ACKCH • Multi-codeword MIMO assignment spans number of nodes number of layers

Channelization & modulation• Each R-ACKCH bit duplicated on multiple time-frequency tiles• At least 4-th order diversity• Orthogonal code multiplexing of different R-ACKCH bits• Allows for accurate interference estimation with extra code dimensions• Improves link budget • ON/OFF keying• Takes advantage of frequent NACK caused by H-ARQ• Prevents ACK errors in some cases of assignment errors

Overhead• 8 dimensions per R-ACKCH, 128 dimensions per base node 1/16 RL bandwidth

CDMA ACK is under study

SISO R-ACKCH nodeMIMO MCW R-ACKCH

nodes

SISO assignment

MIMO MCW assignment


8 OFDM symbols

16 to

nes

8 OFDM symbols

16 to

nes

Sub

tile

1

Sub

tile

3

Sub

tile

4

Sub

tile

2

Traffic onlyTraffic

& R-ACKCH

4-t

h o

rder

div

ers

ity

per

R-A

CK

CH

8 c

od

es

for

8 R

-AC

KC

Hs

8 c

od

es

for

inte

rfere

nce

61

R-ACKCH: FFT size < 512 Used to acknowledge FL H-ARQ transmissions

Present on every RL interlace, linked to the corresponding FL interlace

Channel based R-ACKCH• Every base node of the channel tree maps to a 1-bit R-ACKCH • Multi-codeword MIMO assignment spans number of nodes number of layers

Channelization & modulation• Each R-ACKCH bit duplicated on multiple time-frequency tiles• At least 4-th order diversity• Orthogonal code multiplexing of different R-ACKCH bits• Allows for accurate interference estimation with extra code dimensions• Improves link budget • ON/OFF keying• Takes advantage of frequent NACK caused by H-ARQ• Prevents ACK errors in some cases of assignment errors• Nominal number of sub-tiles per tile: 1 for 128pt FFT, 2 for 256pt FFT

Overhead• 8 dimensions per R-ACKCH, 128 dimensions per base node 1/16 RL bandwidth

SISO R-ACKCH nodeMIMO MCW R-ACKCH

nodes

SISO assignment

MIMO MCW assignment


8 OFDM symbols

16 to

nes

8 OFDM symbols

16 to

nes

Sub

tile

1

Sub

tile

3

Sub

tile

4

Sub

tile

2

Traffic onlyTraffic

& R-ACKCH

4-t

h o

rder

div

ers

ity

per

R-A

CK

CH

8 c

od

es

for

8 R

-AC

KC

Hs

8 c

od

es

for

inte

rfere

nce

62

OFDMA Reverse Link Packet Formats 1

Modulation order for each transmission

Packet format index

Spectral efficiency on 1st transmission

Spectral efficiency on 2nd transmission

Max number of transmissions 1 2 3 4 5 6

0 0.25 -- 6 2 2 2 2 2 2

1 0.50 -- 6 2 2 2 2 2 2

2 1.0 -- 6 2 2 2 2 2 2

3 1.5 -- 6 3 2 2 2 2 2

4 2.0 -- 6 3 3 2 2 2 2

5 2.67 -- 6 4 4 3 3 3 3

6 4.0 -- 6 4 4 3 3 3 3

7 6.0 3.0 6 4 4 4 3 3 3

8 non-decodable 4.0 6 4 4 4 4 4 3

9 4.0 -- 6 6 6 4 4 4 4

10 5.0 -- 6 6 6 4 4 4 4

11 6.0 3.0 6 6 6 4 4 4 4

12 non-decodable 3.5 6 6 6 4 4 4 4

13 non-decodable 4.0 6 6 6 6 4 4 4

14 non-decodable 4.5 6 6 6 6 4 4 4

2 Packet formats 7, 8, and 12-14 are non-decodable at the 1st transmission: allow for high spectral efficiency at target termination

63

Support for CDMA Traffic on the reverse link is optional for the AT

AT is assigned a CDMA control sub-segment and may be assigned one or more CDMA traffic sub-segments• CDMA segment at each AP consists of multiple sub-segments, configured

by the network• If an AT supports CDMA traffic, AN can assign any subset of these CDMA

sub-segments to the AT for data transmission• Full flexibility of CDMA sub-segment assignment – can be common across t

he RAN and same for all ATs, or allow for partial overlap across APs• It is also allowed to have control sub-segments only (i.e., no traffic) for all ATs

• Auxiliary pilots are transmitted in frames carrying data transmissions• Occupy the same bandwidth as the data transmission• Auxiliary pilot can also be used for control channel demodulation on frames where

data is transmitted

• Control sub-segment hops over traffic sub-segments

Reverse Link CDMA Traffic - I

64

Packet formats on CDMA traffic segment are optimized for VoIP with an EVRC vocoder

• Requires three packet formats

• Other types of flows may be transmitted on this segment subject to packet format limitation

• CDMA flow-mapping is determined by AT using a distributed AT-centric CDMA MAC• AN will indicate which flows are allowed on the CDMA traffic segment only, OFDMA traffic se

gment only, or both

Rate determination• Rate determination is carried out using an RRI channel or by using blind detection

• Need for an RRI channel is TBD, to be determined based on computational requirements for an interference-cancellation receiver

Control support• F-ACKCH will be allocated for ATs with enabled CDMA traffic

Reverse Link CDMA Traffic - II

65

Features of CDMA Traffic Segment

CDMA access allows for a statistically multiplexed autonomous transmission capability -- useful for bursty low rate traffic as well as for delay-sensitive applications

CDMA capacity can be substantially enhanced with pilot and traffic interference cancellation to make it competitive to quasi-orthogonal OFDMA performance

• can also allow for fractional other sector interference cancellation

CDMA transmissions have low PAPR – beneficial for power-limited users

If network allows frame selection, cell-edge users can further benefit from CDMA traffic transmission

No need for explicit scheduling grants – leads to control signaling overhead savings on the Forward Link especially for cell-edge users

Fast PER control

66

Multiplexing of CDMA and OFDMA

Sub-carrier Mapping

-CP

Time domain Windowing

fC

IFFT

CDMAPilot + Control + Data

OFDMA Pilot + Data

67

Reverse Link Power Control: OFDMA Traffic

Data is transmitted at dB above control

• [min, max] range is chosen to satisfy ICI margin requirement

• Users should transmit at highest possible subject to inter-sector interference

Each sector measures other sector interference and

broadcasts a indication over F-OSICH

AT adjusts its based on F-OSICH

from nearby AN’s

Delta-based power control results in • high for strong users

• low for weak users

Low values

High values

68

Reverse Link Power Control: CDMA Traffic

Ratio of CDMA traffic to the R-AuxPICH fixed based on packet format

Performance based outer-loop to determine the power offset between the CDMA traffic channel (as well as the R-AuxPICH) and the R-PICH• Needed to ensure latency requirements based on QoS traffic

• Updated by the AT based on H-ARQ termination (F-ACKCH statistics)

Possible option to DTX fast power control commands when CDMA traffic is being transmitted is under study

Loading control• Based on admission control

• Use of slow RAB bits for tighter control of CDMA traffic load is TBD

69

Reverse Link Power Control - I

RL Control Channel Power Control • Fast closed loop power control is used to set the transmit power level on

the reverse link control channels that are transmitted periodically

RL Traffic Channel Power Control: CDMA Traffic• The traffic channel power level is set at an offset relative to R-PICH

• The offset is based on traffic channel performance

RL Traffic Channel Power Control: OFDMA Traffic• The traffic channel power spectral density (PSD) level is set at an offset

relative to the control channel PSD level

• This offset is adjusted based on interference indications received from neighboring sectors

• Maximum traffic PSD offset limited by inter-carrier interference

70

Reverse Link Power Control - II

RL Control Channel Power Control • Fast closed loop power control is used to set the transmit PSD levels on the Reverse

Link control channels and traffic channel• Low-power Reverse Link pilot channel (R-PICH) level is used as a common reference for

power control • Fast Power Control commands control the level R-PICH• Outer loop may be used by the RLSS to adjust R-PICH set-point• CDMA control channels: offset relative R-PICH

• Disjoint links (FLSS different from RLSS): • RoT report from FLSS used to adjust power level• Open loop adjustment for reverse link CDMA control channels based on RL channel quality (F-PQICH) report and

RoT report by AN • Disjoints links may be disabled by the AN (on a per AT-basis)

• R-ACKCH: offset relative R-PICH• IoT report by AN and F-PQICH report used to adjust PSD level • Open loop adjustment based on F-PQICH report and IoT report by AN

RL OFDMA Traffic Channel Power Control• The traffic channel level: offset relative to the control channel level

• Minimum offset based on F-PQICH and IoT reports by AN to target certain QoS driven C/I level • Maximum offset based on F-PQICH and IoT reports by AN to limit the amount of inter-carrier

interference• Boost may apply in case of late H-ARQ terminations

• Offset is adjusted based on interference indication from neighbour sectors

71

L1/L2 Handoff

AT constantly monitors Forward and Reverse channel quality of sectors within AT’s active set

• Acquisition pilot (F-ACQCH) / FL broadband pilot (F-CPICH) for FL quality

• Reverse pilot quality report (F-PQICH) for RL quality

Forward Link and Reverse Link serving sectors need not be the same• Select the strongest FL sector with adequate RL quality to close RL control

• use F-PQICH report by AN

• Select the strongest RL sector with adequate C/I to meet QoS requirements • use IOT reports by AN, • use power headroom and required power based on QoS class

Handoff indication• AT indicates FL preference by sending R-CQICH to the target with desired FL serving

sector (DFLSS) flag set• AT indicates RL preference by sending R-REQCH to the target

Handoff completion• Handoff completes when AT receives assignment from the new sector

Average handoff delay can be as low as 8ms

72

Network may advertise softer handoff groups with the following interpretation• network ensures SFN transmission within the group to a handoff AT

•Sectors in the handoff group transmit the same waveform to the handoff user as serving sector

•BTS can use various forms of diversity: delay diversity, phase sweep diversity, etc.

• network ensures that no interference will be seen by a handoff AT from group members

AT can make handoff decisions based on • combined pilot measurements from all group members to compute the

anticipated SFN channel strength• predict interference level given, e.g., by the overall received power level

less contribution by the group based on pilot measurements from all group members

R-CQICH channel carries channel quality reports corresponding to individual sectors

Softer Handoff Groups

73

Forward and Reverse Link Subband Scheduling

Multi-user diversity gains through frequency sensitive scheduling• Improves fairness through SNR gains to weak users• Enables multi-user diversity gains for latency sensitive users

Design supports two hopping modes• Diversity mode with global hopping across the band• Subband mode with localized hopping

Total bandwidth sub-divided into subbands • Nominal subband size

• 128 subcarriers for FFT sizes of 512 and above• 64 subcarriers for FFT sizes of 128 and 256

• Base nodes hop over the entire subband• Ensures interference diversity

sets of 16 contiguous tones

hops

subband #1

base nodes

subband #2

subband #n

frequency

74

Subband Scheduling: Reporting

Forward Link subband scheduling • Flexible tradeoff between sub-band scheduling gains and reporting load • RL control channel to report subband information • Allow for variable reporting interval

– Average reporting interval defined by AN• Allow for flexible report size

– Report subband index and optionally subband channel quality, mandated by AN • RL broadband pilot (CDMA) enables FL subband channel quality assessment at AN

Reverse Link subband scheduling • Rate prediction & scheduling by AN • RL broadband pilot (CDMA) enables RL subband channel quality assessment at AN

– can use RL CDMA control channels (mainly R-CQICH) as a pilot – can use dedicated RL CDMA pilot (R-PICH)

75

Quasi Orthogonal Reverse Link (1)

Rationale

– Non-orthogonal RL (CDMA): capacity scales linearly with the number of receive antennas

– Orthogonal RL: capacity scales logarithmically with the number of receive antennas

Design

– Superimposing ATs over time-frequency tiles – Multiple antennas to suppress intra-sector interference space-frequency

MMSE receiver– Intra-sector interference diversity through random hopping – Orthogonal pilots to improve channel estimation

76

Define channel tree with sub-trees • ATs scheduled within one sub-tree are orthogonal• different sub-trees map to the same set of time-frequency resources

Orthogonal pilots on different sub-trees • orthogonal (DFT) pilot codes over pilot clusters assigned to different sub-trees • supports QORL: different pilot codes assigned to different ATs • supports softer handoff: different pilot codes assigned to different sectors

Data symbol Pilot symbol, AT A

8 OFD

M sym

bols

16 tones 16 tones

Pilot symbol, AT B

AT 1pilot code 1

AT 2pilot code 2

Sub-tree 1 Sub-tree 2

base nodes

frequency

PHY Frames

Quasi Orthogonal Reverse Link (2)

77

Layered Superposed (LS) OFDMA

Introduce overloading of OFDMA resources by letting users overlap in time/frequency – separate users by interference cancellation/joint decoding

Key idea is to “layer” users according to achievable spectral efficiency – referred to as Layered Superposed OFDMA (LS-OFDMA)

Overloading is possible per spatial dimension, can even be used without multiple antenna receivers

Orthogonalize users with similar spectral efficiency to be within a layer and achieve intra-layer fairness as in a conventional OFDMA system with scheduling

Let users in different layers interfere with each other and occupy the overlapping bandwidth

Separate layers with interference cancellation or joint decoding

Packet format and bandwidth to all users are explicitly allocated by the AN

78

LS-OFDMA Details

Layers hop independently of each other

• Achieved by scheduling ATs of different layers on different sub-trees

• Better interference averaging

• Helps in achieving better fairness – interference cancellation gain from a single user decoding in one layer is spread evenly to many users in the next layer(s)

• Subband hopping allows for joint hopping of large assignments: enables joint decoding

First layer is most aggressive – higher modulation and code-rates and possibly earlier HARQ termination targets

Attempt to first decode all first layer users, cancel those that succeed and then proceed to the next layer

Channel estimation performed for up to first 3 layers of users based on orthogonal pilot resources

Pilot cancellation is performed based on these estimates, and channel estimation is done for the other layers post pilot interference cancellation

Number of non-orthogonal layers will be dynamically determined by AP.

79

Under consideration

Shared sticky assignment of multiple ATs to receive the same FL resource

The baseline case has only one intended recipient AT

Sticky assignment avoids repeated control overhead

Sharing provides possibly better bandwidth utilization

Studying the format, structure, and cost-effectiveness of the design, including the new packet indicator

Multi-user packets: contain messages intended for multiple ATs MUP extends the concept of shared assignment

The packet contains additional header that indicates the intended AT IDs and the segments the bits for different ATs

Provides coding gain from the larger packet sizes

Studying the structure, ACK mechanism, control overhead, power efficiency

80

Open study items

Multi-user MIMO enhancements

Enhanced channel coding based on LDPC

81

Summary

LNQS-LBC is proposed for 3GPP2 air interface evolution phase 2

LNQS-LBC provides high spectral efficiency and high peak rates through the introduction of spatial processing techniques

LNQS-LBC provides a novel design for an advanced mobile wireless system that is optimized for large bandwidth allocations

LNQS-LBC is optimized across large range of bandwidth allocations from 1.25 MHz to 20 MHz

Title:Framework proposal for LBC mode of Rev C Abstract:This contribution presents a joint proposal...

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