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TITLE: HRPD RL Enhancement Proposal

SOURCE: Farooq Khan (+1 973 386 5434) Email: fkhan1@lucent.com

Lucent Technologies grants 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. Lucent Technologies is 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 Lucent Technologies 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 Lucent Technologies. Lucent Technologies specifically reserves the right to amend or modify the material contained herein and to any intellectual property of Lucent Technologies other than provided in the copyright statement above.

ABSTRACT: This contribution presents a proposal for HRPD RL Enhancement .

RECOMMENDATION: Discuss and Adopt

Lucent Technologies Bell Labs Innovations

HRPD RL Enhancement ProposalHRPD RL Enhancement Proposal

Lucent Technologies Lucent Technologies

April 28, 2003April 28, 2003

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Burst Transmission Mode

• Achieves peak data rate of 4Mb/s.

– RL capacity comparable to FL capacity resulting in a symmetric system.

– Allows service providers to offer new services.

• Low latency improves the QoS for Internet applications.

– The packet transmission time is one slot (1.67ms) compared to 26.67ms in the current system.

– The application throughput on the FL also improves thanks to low round-trip times.

• Graceful Evolution of the HRPD standard

– Burst mode is fully backward compatible allowing service provider networks to transition in a smooth, low cost, and faster to market manner.

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Burst Mode – Key features

• Slot-synchronized slot-orthogonal RL transmissions.

• Very high Rise-over-Thermal (RoT) allowed during high-speed burst transmission

– A single mobile within a sector transmits at very high power

– Highly simplified scheduling and resource allocation:• No need to accurately measure the total received power or Rise-

over-Thermal (RoT) etc.

• Achieves maximum gains from techniques already used on the FL:

– Base station controlled fast scheduling, Hybrid ARQ and adaptive modulation and coding (AMC):

• With burst mode, RL structure and operation become similar to the FL structure and operation.

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Illustration of Burst Mode

RL

B: Burst slotPC: Power controlled slotIoc: Other cell interferenceDRC: Data rate control

PC

B

B

B

PCB

B

B

PC

B

B

BPC

B

B

B

Pilots

DRCs

Autonomous lowrate data frommultiple users

Ioc

N0W

ACKs

High-speeddata

Ioc

N0W

High-speeddata

PILOT

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

26.67ms

RoT during PC slots is controlled (as in the current systems) in order toguarantee sufficient coverage and capacity.

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Modes of operation

• Power controlled (PC) mode:

– Autonomous data transmission uses PC mode.

– PC mode is also used for physical layer control signaling• The pilot, DRC and ACK etc. are carried in the PC slots.• The RACH channel is also carried in the PC slots.• The RL power control is performed at 150Hz (for 4 PC slots per frame

case).

• Burst Mode:

– Burst mode is used to perform very high data rate (in most cases at max mobile power) transmissions.

• Total resource (i.e. 26.67ms frame) can be partitioned between PC mode and Burst mode transmissions.

– The resource partitioning can be static or configurable dynamically.

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Burst data rates

• Time multiplexed burst pilot in each slot, serves two purposes;

– channel estimation for demodulation and decoding of the traffic information

– channel quality estimate of the current transmission that allows to select an appropriate rate for any other transmissions to the same user.

Data rate

[Kb/s] Encoder packet

size [bits]

Modulation Coding rate

Number of data chips

Number of pilot chips

T/P ratio [dB]

4003.2 6672 16-QAM 0.834 2000 48 16.20 3686.4 6144 16-QAM 0.768 2000 48 16.20 3072.0 5120 16-QAM 0.640 2000 48 16.20 2457.6 4096 8-PSK 0.688 1984 64 14.91 1843.2 3072 8-PSK 0.525 1952 96 13.08 1228.8 2048 QPSK 0.533 1920 128 11.76 614.4 1024 QPSK 0.276 1856 192 9.85 307.2 512 QPSK 0.276 1856 192 9.85 153.6 256 QPSK 0.276 1856 192 9.85 76.8 128 BPSK 0.276 1856 192 9.85

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PC Mode Data Rates

• In the above Table, PC frame size is assumed at 26.67ms as in the current system.

• Shorter frames in the PC mode are under study.

Data rate

[Kb/s] Number of 4-ary

codes Encoder packet

size [bits] Modulation Coding rate

153.6 3 (a 2-ary and a

4-ary code) 4096 BPSK 0.33333

76.8 2 (a single 2-ary

code) 2048 BPSK 0.25000 38.4 1 1024 BPSK 0.25000 19.2 1 512 BPSK 0.12500 9.6 1 256 BPSK 0.06250

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An example of PC Frame Transmission

“Burst” slots

26.67ms

4096 bits EP [153.6Kb/s] (QPSK, 1/3 coding rate)

“PC” slots

4096 bits EP [153.6Kb/s] (BPSK, 1/3 coding rate)

26.67ms PC Transmission over 16 slots

26.67ms PC Transmission over 8 slots

BPSK QPSK

W/O “Burst” slots

W/ “Burst” slots

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AT-AN control signaling (1)

Access Terminal(AT)

RLScheduler

AccessNetwork (AN)

BUFF_INF + R-PICH PWR

Scheduling Grant (Data Rate)

Information used by the scheduler:RL channel qualityAT’s Buffer Status

Reverse link channel quality caneither be derived from:R-PICH power and TPC trackingor Burst pilot received energy

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AT-AN signaling (2)AT AN

EP1 (128 bytes) + BUFF_INF1 (896 bytes) + R-PICH PWR1

EP2 (512 bytes) + BUFF_INF2 (384 bytes) + R-PICH PWR2

EP3 (384 bytes) + BUFF_INF3 (1024 bytes) + R-PICH PWR3

EP5 (512 bytes) + BUFF_INF5 (0 bytes) + R-PICH PWR5

EP4 (512 bytes) + BUFF_INF4 (512 bytes) + R-PICH PWR4

1024 bytesarrive

1024 bytesarrive

AutonomousTransmission

Rate allocation basedon BUFF_INF1, R-PICH

PWR1 and TPCtracking

Rate allocation basedon BUFF_INF2, Burstpilot Ec/Nt, R-PICH

PWR2 and TPCtracking

Rate allocation basedon BUFF_INF3, Burst

pilot Ec/Nt, R-PICHPWR3 and TPC

tracking

Rate allocation basedon BUFF_INF4, Burst

pilot Ec/Nt, R-PICHPWR4 and TPC

tracking

SCHED_GRANT (2.4Mb/s)

SCHED_GRANT (1.8Mb/s)

SCHED_GRANT (2.4Mb/s)

SCHED_GRANT (2.4Mb/s)

Buffer updatewith the new

data

In case where inband signaling is not decoded due to HARQ retransmission, the scheduler can either schedule retransmissions or new transmissions based on previously received signaling information.

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Control Timing

B B PC B B B PC BB B PC B B B PC BRL

TPC

SG SG SGTPC

SG SG SGTPC

SG SG SGTPC

SG SG SG

One-half slot offset

FL

High-speedburst

Pilot, DRCetc.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

TPC: Transmit power controlSG: Scheduling grantB: Burst slotPC: Power controlled slot

TPC Latency: 4 slots (e.g. pilot measured in slot 3,TPC sent on FL slot 5, power updated in slot 7)Scheduling (rate selection) latency: 4-7 slots AT Processing Time to form a subpacket: >1.5-slot (2.5ms)

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RL control signaling

• RL control signaling consists of 4-bits of buffer status information (BUFF_INF) and 4-bits of reverse pilot channel transmit power (R-PICH PWR)

• Total of 8-bits control information is carried inband as part of the encoder packet i.e. control information is CRC protected and coded together with the encoder packet.

• Note that the AT always transmit at the rate indicated by the AN. Therefore, no rate indication information is carried on the RL.

• Inband signaling of QoS information under study.

Information bitsBUFF_INFR-PICH

PWRCRC Tail

4-bits 4-bits n-bits

Turbo coding

Encoder Packet

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RL control overhead

Data rate [Kb/ s]

Encoder packet size

[bits]

Percentage overhead due to 1-byte (8-bits) inband

header

Selection probability

Overhead

3686.4 6144 0.13% 0.26640 0.035% 3072.0 5120 0.16% 0.06450 0.010% 2457.6 4096 0.20% 0.09890 0.019% 1843.2 3072 0.26% 0.07570 0.020% 1228.8 2048 0.39% 0.14000 0.055% 614.4 1024 0.78% 0.13650 0.107% 307.2 512 1.56% 0.08210 0.128% 153.6 256 3.13% 0.08080 0.253% 76.8 128 6.25% 0.03830 0.239% 38.4 64 12.50% 0.01680 0.210%

Percentage Overhead 1.08%

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Scheduling grant signaling (1)

• Each active AT is allocated a unique MACIndex (AT ID):

– Indicate if a particular AT has been scheduled for RL packet transmission (can be the same as TPC MACIndex).

– Carried in two 64 chips MAC bursts immediately preceding the pilot burst

• Rate Indication (RI) and HARQ control information (56 combinations) is carried in two 64 chips MAC bursts immediately following the pilot bursts:

– The MACIndex 8 to 63 are used for RI+HARQ.

– MAXIndex 4 is used for RAB indication (as in the current standard)

• Scheduling grant structure using coding under study

– For example, AT ID, rate indication and HARQ control information can be coded and CRC protected and transmitted over multiple 16-ary (or 64-ary) Walsh codes in the MAC bursts of the FL slot.

Data(400 chips)

RAB

AT ID

Pilot(96)

Data(400)

RAB

RI+HARQCTRL

Data(400)

RAB

Pilot(96)

Data(400)

RAB

RI+HARQCTRL

RI: Rate Indication (7 rates)HARQ CTRL: Hybrid ARQ Control (4 ARQ channels and 2 ACK/NACK levels)

64 chips 64 chips 64 chips 64 chips

Slot containing scheduling grant(2048 chips)

AT ID

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Scheduling grant signaling (2)• In variable rate burst mode operation, AT ID length is 128 chips (2 bursts

of 64 chips).

• Autonomous operation not requiring scheduling grants can be allowed for the disadvantaged users.

• Fixed rate operation can also be allowed for disadvantaged users. In this case 256 chips in a slot can be used as AT ID.

• Slots containing TPC bits and scheduling grants are orthogonal in time. New ATs will not look for TPC bit in the slots designated for scheduling grants and vice versa.

• Legacy ATs with TPC MACIndex the same as the new scheduled AT MACIndex or RI+HARQ MACIndex can interpret scheduling grant as TPC bit.

• Since only two TPC MACIndices (AT ID and RI+HARQ control) can be active in a slot containing scheduling grant, this will have negligible impact on power control operation for legacy ATs.

• DRCLock Channel is carried in slots orthogonal to slots carrying scheduling grants.

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ACK Channel Operation

• Multilevel ACK/NACK is used in order to simultaneously ACK/NACK up to 3 encoder packets

• For legacy ATs, ACK reliability during a burst slot is guaranteed by appropriately setting the ACKChannelGain public data of the Forward Traffic Channel MAC Protocol

B B PC B B B PC BB B PC B B B PC BRL

TPC

EP4 EP5 EP6TPC

RTXEP1

EP7RTXEP3

TPC

EP1 EP2 EP3TPC

EP8RTXEP5

EP9

One-half slot offset

FL

High-speedburst

ACK/NACK for EP1,EP2 and EP3

ACK EP2NACK EP1 and EP3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

EP: Encoder PacketB: Burst slotPC: Power controlled slot

ACK/NACK for EP4,EP5 and EP6

ACK EP4 and EP6NACK EP5

ACK/NACK for EP1,EP7 and EP3

ACK EP1, EP7 andEP3

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Signaling overhead - observations

• Minimum signaling and control overhead in order to support burst mode:

– Approximately 1% RL overhead

– No additional FL overhead (small degradation due to 150Hz RL power control)

• Signaling and control optimized to reduce delays

– Up to date buffer information available at the base station scheduler

• Every encoder packet carries buffer update information

• Backward compatible control structure

– The new and legacy ATs coexist on the same carrier

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Simulation Assumptions

• Inline with 1xEV-DV evaluation methodology

– 3-sector 19-cell, Wrap-around

– Channel mix etc.

• 10 users with Full buffers

• HARQ based on incremental redundancy

– SHO gain not assumed i.e. ACK/NACK from the serving cell only

• HARQ in SHO is understudy

• All users are scheduled in burst mode

– No autonomous transmissions assumed• Simulations results for the hybrid case where some users are

allowed to transmit in the PC mode as well will be provided later on.

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Simulation parameters

Parameter Value Number of users 10

Traffic model Full buffers PC slots per frame (26.67ms) 4

Burst slots per frame 12 HARQ type IR

RL channel quality delay 4 slots Max number of HARQ transmissions 8

Scheduler PF Rate selection margin () 3dB

Maximum Ec/ Nt 17.8dB

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Rate Selection

• We assume that the BS has knowledge of:

– Background noise, N0:

• In burst mode, background noise can be measured by leaving a slot empty in all the sectors in the system.

• This measurement need to be performed rarely because the background noise does not change over short periods of time.

– RL channel gain (including shadow and fast fading)

• The RL channel gain can be estimated either by using the R-PICH transmit/receive power information or using the TDM pilot (only applies if there was a previous transmission to the same user).

• The received Ec/N0 is calculated assuming that the mobile transmit at the allocated power (maximum of 200mW)

• A margin, dB is subtracted from Ec/N0

• The rate is then selected by link curve look-up:

– The selected rate is the maximum rate that would “provide” 1% or lower FER at (Ec/N0-dB.

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Burst Mode power allocation

• Burst power allocation allows to control the total received RoT thus avoiding any impact on legacy transmissions.

• Two options

– Static power allocation• Max burst transmit powers are set at the time of call setup

based on long-term path loss (can be estimated by e.g. pilot measurements)

– Dynamic power allocation • Burst power is allocated through the scheduling grant message

based on the instantaneous channel gain (including fast fading)

• The simulation results presented in this document are for static power allocation only.

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Capacity, RoT and Ec/Nt

Ec/Nt

RoT

Target RoT [dB] Sector capacity [Kb/ s]

Mean RoT [dB]

Mean Ec/ Nt [dB]

20dB 785 13.5 4.43 10dB 846 9.87 4.17 5dB 718 7.10 2.69 0dB 471 4.35 0.28

Note that Target is set without accounting for the other-cell interference.

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MS Transmit PWR CDF

23dBm

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CDF of Normalized User Throughputs

System becomes fairer as the target RoT is lowered. This is due to the fact that loweringtarget RoT results in the small spread of received powers across users.

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Rate selection probability

Actual rates after HARQ retransmission(s) can be smaller

Rate selection probability

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

3686 3072 2458 1843 1229 614.4 307.2 153.6 76.8 38.4

Rate [Kb/s]

Pro

ba

bil

ity

Target RCV PWR=20dB RoT

Target RCV PWR=10dB RoT

Target RCV PWR=5dB RoT

Target RCV PWR=0dB RoT

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Backward compatibility

• In the presence of legacy users, burst transmission power can be allocated such that the total RoT does not exceed the specified target

– e.g. RoT should be below 7dB 99% of the time.

• DRC from legacy users can be operated in the Gated mode making sure that the DRC transmission only happen in the PC slots.

– Maximizes the burst mode TDM gain

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Further optimizations

• Burst and control strategy:

– New mobiles are allowed to transmit at a higher RoT even if the slot is used by legacy transmission(s).

– Quality for legacy transmissions is guaranteed by increasing the outer loop PC threshold to compensate for the loss in energy due to higher RoT Burst transmission.

• Interference cancellation

– A single Burst user (strongest and known user) can be detected and cancelled from the overall signal in the same sector.

• Scheduler and rate selection optimization

– For example, rate specific margins

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Summary

• Burst Mode meet and exceed CDG SRD requirements (>2.4 Mb/s peak data rate and >600Kb/s capacity in 1.25MHz bandwidth).

• Burst mode provides significant improvements in RL capacity.

– The RL capacity becomes comparable to FL resulting in a symmetric system.

– Allows service providers to offer new services.

• Burst mode provides a fully backward compatible solution

– New Burst mode and legacy mobiles coexist on the same carrier.