004 EVDO Theory (Ind)

58
Principle and Implementation of CDMA2000 EVDO System CBB_T05_E2 ZTE University CDMA-BSS Team

Transcript of 004 EVDO Theory (Ind)

Page 1: 004 EVDO Theory (Ind)

Principle and Implementation of CDMA2000 EVDO SystemCBB_T05_E2

ZTE University

CDMA-BSS Team

Page 2: 004 EVDO Theory (Ind)

Unit 1

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3G and Beyond

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Goals of Rev A

Increase spectral

efficiency and throughput

Increase peak rates and average

throughput

Support for delay-sensitive

applications

Support for QoS (Quality of Service)

Higher reverse link throughput

Lower latency

Backward compatibility

with Rel 0

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1x EVDO Network Structure

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A Interfaces of 1xEVDO

� Um interface carries the signals exchanged between AT and AN over the air.

� A8 & A9 interfaces are adopted to carry service data and signaling respectively between BSC and PCF.

� A10 & A11 interfaces are adopted to carry service data and signaling respectively between PCF and PDSN.

� A12 interface carries signaling information of access authentication (only include 3 messages: access request, access accept, and access reject).

� A13 interface exchanges signaling when AT is roaming between source AN and target AN

� RADIUS stands for Remote Authentication Dial In User Service. Provides interface between PDSN and AAA to control access to thedata network.

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Comparison of EVDO and 1x Networks

BSCBTS

MSC

PCF PDSN

AN AAA AAA

HLR

MS/AT

AN AAA provides radio access authentication similar to MSC/HLR for CDMA2000 1x data call setup

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Network Implementation

Centralized StructureCentralized Structure

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Upgrading 1x to DO

� BTS side: add EVDO baseband processing part� - If a new EVDO carrier is added,

� Add EVDO baseband processing part

� Add related radio transmission part� Keep antenna and feeder.

� - If upgrading 1x carrier to EVDO carrier� Add EVDO base band processing part� Keep antenna and feeder

� BSC side: add EVDO processing part, upgrade related software for

EVDO Signaling and increased data service capacity requirement

� PCF Side: add data processing module for the increased in capacity

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Unit 2

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Protocol Architecture

Application Message routing, RLP, flow control

Stream Multiplex various application streams

Session Establish and configure data sessions

Connection Establish and manage radio connections

Security Provide authentication and encryption

MAC Data rate control and scheduling

Physical Adaptive modulation, coding and spreading

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EVDO Principles

Forward Channel Structure

Reverse Channel Structure

Key Techniques

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Physical Layer Subtypes

� Physical Layer Subtype 0 � Provides backward compatibility to Rel 0� Supports variable data-rate from 38.4 kbps to 2.4576 Mbps for FL, and 9.6 kbps to 153.6 kbps for RL

� Physical Layer Subtype 1� Supports 9.6, 19.2 or 38.4 kbps transmission on the access data channel for RL

� Physical Layer Subtype 2� Supports variable data-rate from 4.8 kbps to 3.072 Mbps for FL, and 4.8 kbps to 1.8432 Mbps for RL� Supports 9.6, 19.2 or 38.4 kbps transmission on the access data channel for RL

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Forward Channel Structure

New to Rev A

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Forward Data Time Slot

400 40040096 40064 6464 64 96

Data PilotMAC MAC Data Data PilotMAC MAC Data

9664 64

PilotMAC MAC

9664 64

PilotMAC MAC

Idle Slot

Active Slot

½ slot = 1024 chips ½ slot = 1024 chips

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Forward Pilot Channel

� The Pilot channel is transmitted at the full sector power.

� The Pilot channel is sent as 96 chip bursts, each of which is located

at the center of each half slot for easier channel estimation and time

synchronization

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Forward MAC Channel

� RA subchannel� Broadcast Reverse Activity Bit to all ATs to indicate the current status of the reverse traffic channel

� RPC subchannel� Sends power control commands to the AT for closed loop power control

� DRCLock subchannel� Transmits reverse link quality indication used by the AT for forward link serving sector selection.

� ARQ subchannel (Subtype 2)� Tells each AT if it’s reverse traffic channel packet is successfully received or not.

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MAC Index

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MAC Channel (Subtype 0 and 1)

� The RPC and DRCLock sub-channels are time-division multiplexed� RPC is transmitted in DRCLockPeriod – 1 times

� DRCLock is transmitted once every DRCLockPeriod and repeated forDRCLockLength times.

� The RA sub-channel is code division multiplexed with either RPC or

DRCLock sub-channel

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MAC Channel (Subtype 2)

� H-ARQ or L-ARQ is timeshared (1:3 slots TDM) with the RPC stream.� H-ARQ bit is used to indicate whether the reception of the subpacket resulted in the correct recreation of the entire packet and is transmitted for every subpacket received except the last subpacket.� L-ARQ bit is used to indicate whether the packet was successfully received and is transmitted only after the last subpacket is received

� P-ARQ is timeshared (1:3 slots TDM) with the DRCLock stream.� P-ARQ bit is sent in response to the correct or incorrect reception of the entire physical layer packet. It is transmitted after the time period corresponding to the maximum number of subpackets is over.

� RA is summed together with the RPC stream and DRCLock stream.

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ARQ Early Termination

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ARQ for Failed Transmission

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Forward Pilot / MAC

PilotAll 0’s

RPC bit for each MAC index i

1 bit / 4 slots (150 bps)

HARQ / LARQ for MAC index i

3 bits / 4 slots

RA bit1 bit / slot

192 chips / slot

256 chips / slot

I

IQ

RPC Gain

ARQ Gain

PARQ for MAC index i

3 bits / 4 slots

DRCLock

600 / DRCLockLength bps1 bit / 4 slots

TDM

ARQ Gain

DRCLock Gain

Bit Repeat

Bit Repeat

RA Bit Gain

TDM

SummerSeq. Rep

x 2

TDM

W0

I for even MAC indexQ for odd MAC index

I for even MAC indexQ for odd MAC index

Wi 128

Wi 128

W2 128

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Rev A Key Enhancements

� Transmission Format� Notation to define transmission format and interpret the DRC value to determine the data rate

� The turbo coding rate, modulation type and number of available repetition is specified for each transmission format.

� Multi-user Packet� More than one AT (up to 8) receives data during a 1.67 ms time-slot� Contains one or more Security layer packets destined for one or more ATs and is identified by a multi-user preamble

(<packet length (bits)>, <number of slots>, <preamble length (ch(<packet length (bits)>, <number of slots>, <preamble length (chips)>)ips)>)

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Forward Control Channel

� Transmission Formats� (128, 4, 1024) � 19.2 kbps� (256, 4, 1024) � 38.4 kbps� (1024, 16, 1024) � 38.4 kbps� (512, 4, 1024) � 76.8 kbps� (1024, 8, 512) � 76.8 kbps

� Synchronous Capsule (SC).� Broadcast Overhead messages � Page messages

� Sub-Synchronous Capsule (SSC)� Facilitates shorter wake intervals for enhance standby time.

� Asynchronous Capsule (AC) � deliver ACK messages and RLP Control messages� may be sent at any time during which the AN is not sending a synchronous or sub-synchronous capsule.

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Forward Control Channel

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Forward Traffic Channel

� Supported data rates:� 38.4 to 2457.6 Kbps (Subtype 0 and Subtype 1)� 4.8 to 3072 Kbps (Subtype 2)

� Modulation � QPSK, 8PSK or 16-QAM

� Channel coding rate � 1/3 or 1/5.

� A preamble is attached as the header of each physical

layer packet.

� The transmitted packet = preamble + physical layer

packet

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Modulation Parameters (Subtype 2)

(128, 16, 1024) 1/5 QPSK 4.8

(128, 8, 512) 1/5 QPSK 9.6

(128, 4, 1024) 1/5 QPSK 19.2

(128, 4, 256) 1/5 QPSK 19.2

(128, 2, 128) 1/5 QPSK 38.4

(128, 1, 64) 1/5 QPSK 76.8

(256, 16, 1024) 1/5 QPSK 9.6

(256, 8, 512) 1/5 QPSK 19.2

(256, 4, 1024) 1/5 QPSK 38.4

(256, 4, 256) 1/5 QPSK 38.4

(256, 2, 128) 1/5 QPSK 76.8

(256, 1, 64) 1/5 QPSK 153.6

(512, 16, 1024) 1/5 QPSK 19.2

(512, 8, 512) 1/5 QPSK 38.4

(512, 4, 1024) 1/5 QPSK 76.8

(512, 4, 256) 1/5 QPSK 76.8

(512, 4, 128) 1/5 QPSK 76.8

(512, 2, 128) 1/5 QPSK 153.6

Transmission

Format

Code

Rate

Modulation

Type

Nominal Data

Rate (Kbps)

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Modulation Parameters (Subtype 2)

(512, 2, 64) 1/5 QPSK 153.6

(512, 1, 64) 1/5 QPSK 307.2

(1024, 16, 1024) 1/5 QPSK 38.4

(1024, 8, 512) 1/5 QPSK 76.8

(1024, 4, 256) 1/5 QPSK 153.6

(1024, 4, 128) 1/5 QPSK 153.6

(1024, 2, 128) 1/5 QPSK 307.2

(1024, 2, 64) 1/5 QPSK 307.2

(1024, 1, 64) 1/3 QPSK 614.4

(2048, 4, 128) 1/3 QPSK 307.2

(2048, 2, 64) 1/3 QPSK 614.4

(2048, 1, 64) 1/3 QPSK 1,228.8

(3072, 2, 64) 1/3 8-PSK 921.6

(3072, 1, 64) 1/3 8-PSK 1,843.2

(4096, 2, 64) 1/3 16-QAM 1,228.8

(4096, 1, 64) 1/3 16-QAM 2,457.6

(5120, 2, 64) 1/3 16-QAM 1,536.0

(5120, 1, 64) 1/3 16-QAM 3,072.0

Transmission

Format

Code

Rate

Modulation

Type

Nominal Data

Rate (Kbps)

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Modulation Parameters (Subtype 0/1)

Data rate

(kbps)

Slots per

Packet

Packet Size

(bits)

Code

RateModulation

Number of

Modulation

Symbols

Provided

Repetition

Number of

Modulation

Symbols

Provided

Preamble

(chips)

The

transmitted

packet

38.4 16 1024 1/5 QPSK 2560 9.6 24576 1024 25600

76.8 1024 1/5 QPSK 4.8 512

153.6 4 1024 1/5 QPSK 2560 2.4 6144 256 6400

307.2 2 1024 1/5 QPSK 2560 1.2 3072 128 3200

307.2 4 2048 1/3 QPSK 3072 49/48 6272 128 6400

614.4 1 1024 1/3 QPSK 1536 1 1536 64 1600

614.4 2 2048 1/3 QPSK 3072 49/48 3136 64 3200

921.6 2 3072 1/3 8PSK 3072 49/48 3136 64 3200

1228.8 1 2048 1/3 QPSK 3072 0.5 1536 64 1600

1228.8 2 4096 1/3 16QAM 3072 49/48 3136 64 3200

1843.2 1 3072 1/3 8PSK 3072 0.5 1536 64 1600

2457.6 4096 1/3 16QAM 0.5 64

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Preamble

� Assists the AT with synchronization of variable rate

transmissions on the Forward Traffic Channel and Control

Channel

� Contains all ‘0’ and covered by 64-chip (32-chip for

subtype 0 and subtype 1) sequence then repeated several

times according to the transmit mode

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Forward Traffic / Control / Preamble

Seq. Repx 2

Coding – Scrambling– Interleaving

Forward Traffic of Control Channel

Physical Layer Packets

TDM

PreambleAll 0’s

Walsh Cover – Gain– Summer

Modulation (QPSK, 8PSK, 16QAM)

Repetition - Puncturing

64 to 1024 chips

Wi 64

QI

QI

QI

QI

I

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Coding (1/5) 5120

coding symbol

Forward Traffic Modulation Example

Example for (1024,16,1024) ���� 38.4 kbps

Packet size = 1024

Modulation(QPSK)5120

1 modulation symbol

2560Repetition /Puncturing

(x 9.6)24,576

Preamble(1024 chips) 1024 2457624,576

symbols

25,600 chips

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Time-Division Multiplexing

1024 24576

400 64 96 64 400 224 176 64 96 64 400

EVDO uses 4-slot interlace time division multiplexing of users

PilotMAC

1st slot nth slot 2nd slotnth slot nth slot 16th slot

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Scheduling Algorithm

� Round Robin (RR) lets every active data flow (that has data packets

in queue) to take turns in transferring packets on a shared channel in a

periodically repeated order

� Maximizing Throughput selects the users which have excellent

channels to get as much data as possible through the system.

� Proportional Fair (PF) takes into account latency while selecting the

user with the largest instantaneous data rate relative to its average

throughput. However, consistently underserved users receive

scheduling priority to promote fairness. Most common scheduling

algorithm used in EVDO.

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EVDO Principles

Forward Channel Structure

Reverse Channel Structure

Key Techniques

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Reverse Channel Structure

New to Rev A

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Reverse Access Channel

� The Access Channel is used by the AT to initiate

communication with the access network or to respond to an

access terminal directed message.

� The Access Channel consists of a Pilot Channel and a

Data Channel.

� The AT shall transmit on the Access Channel at a data

rate of 9.6 kbps (packet size 256) for Subtype 0, data rates

of 9.6,19.2, or 38.4 kbps (packet sizes 256, 512,1024) for

Subtype 1 and Subtype 2.

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Access Channel Probe

� Probe � Preamble (Pilot) + Capsule Frames (Pilot + Data)

� The output power of the preamble is independent of the data rate and

is set equal to that of the data portion transmitted at 9.6 kbps.

Pilot channel(I Phase)

Pilot channel(I Phase)

Data channel(Q Phase)

Preamble slots

CapsuleFrames

Pilot channel(I Phase)

Pilot channel(I Phase)

Data channel(Q Phase)

Preamble Frames Capsule Frames

(Access channel physical layer

packets)

Subtype 0Subtype 0

Subtype 1 or 2Subtype 1 or 2

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Reverse Traffic Channel

� The Reverse Traffic Channel is used by the AT to

transmit user-specific traffic or signaling information to AN.

� The Reverse Traffic Data Channel is transmitted in

frames = 26.67ms

PILOT RRI

ACK

DRC

Data

Subtype 0 and Subtype 1

PILOT

Aux PILOT

DSCACK

DRC

Data

Subtype 2

RRI

Subframe (4 slots ) is the minimum transmission of the Data channel for Subtype 2

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Pilot /Auxiliary Pilot Subchannel

� The Pilot Channel enables coherent demodulation at the

AN.

� In the case of Subtype 0/1 , the pilot is time-division

multiplexed with RRI --- the pilot channel occupies the last

7/8 of one slot.

� The Auxiliary Pilot Channel is used by the AT to aid

reverse link channel estimation by the AN. (Subtype 2 only)

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Reverse Rate Indicator Subchannel

� The RRI Channel is used to indicate the payload size and the sub-packet identifier of the physical layer packet transmitted on the Reverse Traffic Channel.

� Subtype 0/1� 3-bit symbol identify corresponding reverse data rate.

� Subtype 2� A 6-Bit RRI symbol used to indicate the data payload size (4-bits) and to provide the sub-packet identifier (2-bits). � The sub-packet identifier of the current transmission facilitates reverse link H-ARQ.� The payload size identification assists in avoiding blind rate detection at the AN.

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Data Rate Control Subchannel

� The DRC Channel is used by the AT to indicate to the AN

the requested Forward Traffic Channel data rate and the

selected serving sector on the Forward Channel.

� DRCValue (4-bit) : specifies the requested Forward Traffic Channel data rate� DRCCover (8-ary Walsh cover) : indicates the selected serving sector� DRCLength : number of consecutive slots the DRC is repeated

Serving sector is the sector the AT selects for receiving the Forward Traffic channel

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Data Source Control Subchannel

� The DSC Channel is used by the AT to indicate to the AN

the selected serving cell on the Forward Channel.

(Subtype 2 only)

� It provides advance notice of the AT’s intent to switch cell

to reduce inter-cell handoff latency.� DSCValue (3-bit) – indicates the selected serving cell� DSCLength – number of slots the DSCValue stays in effect.

� Time division multiplexed with ACK subchannel and

transmitted on the 2nd half slot.

Serving cell is the cell that contains the serving sector

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ACKnowledgement Subchannel

� The ACK Channel is used by the AT to inform the AN whether or not the physical layer packet transmitted on the Forward Traffic Channel has been received successfully.

� Using ACK allow AN to early-terminate multi-slot packet transmission and increase the actual throughput.

� Time division multiplexed with DSC and transmitted on the 1st half slot for Subtype 2.

TypePositive

Acknowledgement

Negative

AcknowledgementUse

Binary Keying 1 -1 Single User Packet

On-Off Keying (OOK) 1 0 Multi User Packet

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Reverse Traffic ACK Channel

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Reverse Traffic Data Channel

� Supported data rates� 9.6 to 153.6 Kbps (Subtype 0 and Subtype 1)� 4.8 to 1228.8 or optional 1843.2 Kbps (Subtype 2)

� Modulation � BPSK, QPSK or 8-PSK

� Channel coding rate � 1/3 or 1/5

� Subtype 2 introduces Traffic channel to Pilot channel

transmit power ratio (T2P) for reliable estimation of the RL

and quick adjustment of Reverse Traffic Channel data

rates.

QPSK or 8-PSK modulation is used only by Subtype 2

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Modulation Parameters (Subtype 2)

Payload Size (bits)

ModulationEffective Data Rate (kbps) Effective Code Rate and Repetition

4 slots 8 slots 12 slots 16 slots 4 slots 8 slots 12 slots 16 slots

128 B4 19.2 9.6 6.4 4.8 1/5 [3.2] 1/5 [6.4] 1/5 [9.6] 1/5 [12.8]

256 B4 38.4 19.2 12.8 9.6 1/5 [1.6] 1/5 [3.2] 1/5 [4.8] 1/5 [6.4]

512 B4 76.8 38.4 25.6 19.2 1/4 [1] 1/5 [1.6] 1/5 [2.4] 1/5 [3.2]

768 B4 115.2 57.6 38.4 28.8 3/8 [1] 1/5 [1.07] 1/5 [1.6] 1/5 [2.13]

1024 B4 153.6 76.8 51.2 38.4 1/2 [1] 1/4 [1] 1/5 [1.2] 1/5 [1.6]

1536 Q4 230.4 115.2 76.8 57.6 3/8 [1] 1/5 [1.07] 1/5 [1.6] 1/5 [2.13]

2048 Q4 307.2 153.6 102.4 76.8 1/2 [1] 1/4 [1] 1/5 [1.2] 1/5 [1.6]

3072 Q2 460.8 230.4 153.6 115.2 3/8 [1] 1/5 [1.07] 1/5 [1.6] 1/5 [2.13]

4096 Q2 614.4 307.2 204.8 153.6 1/2 [1] 1/4 [1] 1/5 [1.2] 1/5 [1.6]

6144 Q4Q2 921.6 460.8 307.2 230.4 1/2 [1] 1/4 [1] 1/5 [1.2] 1/5 [1.6]

8192 Q4Q2 1228.8 614.4 409.6 307.2 2/3 [1] 1/3 [1] 2/9 [1] 1/5 [1.2]

12288 E4E2 1843.2 921.6 614.4 460.8 2/3 [1] 1/3 [1] 1/3 [1.5] 1/3 [2]

E4E2 is 8-PSK/4-ary Walsh cover plus 8-PSK/Binary Walsh cover

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Modulation Parameters (Subtype 0/1)

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EVDO Principles

Forward Channel Structure

Reverse Channel Structure

Key Techniques

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Adaptive Modulation and Coding (AMC)

� The modulation and coding

is dynamically adjusted

according to the condition of

the radio link.

� In the forward link, the C/I is

measured by the AT then

request corresponding data

rate thru the DRC.

� In the reverse link, the

payload size, modulation, and

coding is varied according to

T2P and RAB

0 1000 2000 3000 4000 5000 6000 7000 8000−5

0

5

10

15

slot index

FL

C/I(

dB)

0 1000 2000 3000 4000 5000 6000 7000 80000

500

1000

1500

2000

2500

slot index

Req

uest

ed R

ate(

kbps

)

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Reverse Rate Selection (Rel 0)

� The AP determines the condition of the reverse link and sends RAB to the AT

� The AT calculates the probability that it will increase (RAB=not busy) or decrease (RAB=busy) data rate according to the probability vector, P and q.

� The AT compares the result with the Reverse Rate Limit to check whether the threshold is reached.

NotBusy

9.6kbps

19.2kbps

153.6kbps

P1

38.4kbps

76.8kbps

P2 P3 P4

Busy9.6

kbps19.2kbps

153.6kbps

q1

38.4kbps

76.8kbps

q2 q3 q4

Reverse Rate Limit Message is sent by AP to limit the reverse data rate according to the number of active users

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Reverse Rate Selection (Rev A)

� The AT adjust the pilot channel power according to the power control

commands received from the AN.

� The AT determines the data channel power which is a relative power

offset to the level of the pilot channel.

� AT calculates T2P for the next transmission according to multiple

inputs, including current T2P and RAB of current active set sectors.

� Based on the T2P, the payload size is identified and so is the reverse

data rate.

� Reverse data rates can vary very quickly and in larger steps

compared to Rel 0 (one step rate change).

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Handoff

� FBSS (Fast Base Station

Switching) – the AT keeps

several AP in its active set but

only one AP is serving at any

instance. This is sometimes

referred to as Virtual Soft

Handoff.

AP1AP1

AP4AP4

AP2AP2

AP3AP3

AP1AP1 AP2AP2

TimeTime

Serving APServing AP

t1t1

Serving AP changeServing AP change

Server before t1

Server before t1

Server after t1

Server after t1

current sector forward data rate

Pilot/MAC on FWD linkPilot/DRC/ACK/Traffic on REV Link

(AP’s in AT’s active set)

After handoff AP2 forward data rate

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Serving Sector Selection

Serving Sector Selection

-15

-14-13-12-11

-10

-9-8

-7

-6-5

-4-3

-2

-1

012

3

0 2 4 6 8 10 12 14

time, sec

SIN

R, d

B

Sector 0

Sector 1

Serving Sector Index

AT decides the serving sector based on the pilot signal SINR of AP

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DSC Operation

� AP scans and measures pilot signal strength of all available sectors to determine if a handoff is necessary.

� As AP moves within the sectors of the same cell, the DSC is maintained while DRCCover may change.

� As AP moves to the coverage of another cell, DSC is sent to relay the intention for handoff to another cell.

� During the transition period, the AP still transmits on the current active cell. This reduces the interruption time due to handoff (typically less than 20ms)

Cell AData Source

Cell BData Source

A1

A2

A3

B2

B3

B1

DRC

DSC A B

A2 A2 A3 A3 B1 B1N N N N

Time

Pilot Strength

N: Null DRCCover

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Power Control

� No power control on the forward link.

� Reverse link employ closed-loop and open-loop power

control� In Open-loop power control, the AT will use an algorithm to estimate the minimum necessary transmit power to communicate with the AP.� Closed-loop correction (with respect to the Open-loop estimate) is provided by the AP by sending Power Control Bit (PCB) thru the RPC subchannel. Bit “0” tells the AT to increase power, bit “1” tells the AT to decrease power. Each PCB is either a 1 dB or 0.5 dB step size.

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