ev-do air interface -20050106-a-1.0

Document number Product name

Applicable for Product version

Drafted by CDMA Network Planning Department

Document version

EV-DO Air Interface

Prepared by Zeng Shuhui Date

Reviewed by Date

Reviewed by Date

Approved by Date

Huawei Technologies Co., Ltd. All rights reserved

Revision Record Date Revision

version Descriptions Author

2003.11.27 V1.00 First draft completed Zeng Shuhui

2004.3.3 V1.01 Revision draft completed Nie Jimin

2004.12.02 V1.02 Revision draft completed Li Ruixi

Table of Contents

EV-DO Air interface ................................................................................................................... 2

1.1 Introduction to 1xEV-DO Air Interface .................................................................................. 2 1.1.1 Structure Reference Model ........................................................................................ 2 1.1.2 Protocol Structure....................................................................................................... 3 1.1.3 1xEV-DO Channel Structure ...................................................................................... 6 1.1.4 Slot Structure.............................................................................................................. 7

1.2 Forward Link Channels......................................................................................................... 7 1.2.1 Forward Channel Structure ........................................................................................ 8 1.2.2 Traffic Channel ........................................................................................................... 9 1.2.3 Control Channel ....................................................................................................... 14 1.2.4 Pilot Channel ............................................................................................................ 15 1.2.5 MAC Channel ........................................................................................................... 15 1.2.6 Working Mode .......................................................................................................... 17

1.3 Reverse Link Traffic Channel ............................................................................................. 21 1.3.1 Reverse Traffic Channel Structure........................................................................... 22 1.3.2 Pilot /RRI Channel.................................................................................................... 23 1.3.3 ACK Channel............................................................................................................ 24 1.3.4 DRC Channel ........................................................................................................... 25 1.3.5 Data Channel ........................................................................................................... 25 1.3.6 Access Channel ....................................................................................................... 28

List of Figures

Figure 1-1 Structure Reference Model ..............................................................................2

Figure 1-2 Air Interface Hierarchical Structure...................................................................3

Figure 1-3 Forward Channel Structure of 1xEV-DO ..........................................................6

Figure 1-4 Reverse Channel Structure of 1xEV-DO ..........................................................6

Figure 1-5 Forward Channel Slot Structure of 1xEV-DO System ......................................7

Figure 1-6 Comparison of CDMA2000 and 1xEV-DO Base Station Transmit Power Sharing...................................................................................................................................8

Figure 1-7 Forward link slot structure ................................................................................9

Figure 1-8 QPSK Constellation........................................................................................11

Figure 1-9 8PSK Constellation ........................................................................................11

Figure 1-10 Signal Constellation for 16QAM Modulation.................................................12

Figure 1-11 Physical Layer Packet of Forward Traffic Channel.......................................13

Figure 1-12 Time-division multiplexing of Control Channel .............................................14

Figure 1-13 Control Channel Structure Physical Layer Packet Bit Size...........................15

Figure 1-14 Multi-slot Data Interleaving With Normal Termination ..................................18

Figure 1-15 Multi-slot Physical layer packet with early termination..................................19

Figure 1-16 Virtual Soft Handoff ......................................................................................20

Figure 1-17 Reverse Channel Structure for the Reverse Traffic Channel (Part 1 of 2)....22

Figure 1-18 Reverse Channel Structure for the Reverse Traffic Channel (Part 2 of 2)....23

Figure 1-19 Time-division multiplexing of reverse pilot channel and RRI channel...........24

Figure 1-20 Physical Layer Packet of Reverse Traffic Channel.......................................27

Figure 1-21 Physical Layer Packet of Access Channel ...................................................28

Figure 1-22 Access probe ...............................................................................................29

Figure 1-23 Generation of access channel ......................................................................30

List of Tables

Table 1-1 Forward link data rates ......................................................................................9

Table 1-2 MACIndex Comparison ...................................................................................16

Table 1-3 MAC Channel Modulation Parameters ............................................................16

Table 1-4 Reverse link data rate......................................................................................21

Table 1-5 Parameters for reverse link encoder................................................................25

EV-DO Air interface Internal open

2004-02-022 All rights reserved Page i of 36

EV-DO Air Interface

Key words:

Abstract:

List of Acronyms and Abbreviations:

1. AN Access Network

2. AT Access Termination

3. DRC Data Rate Control

4. MAC Medium Access Control

5. RA Reverse Activity

6. RLP Radio Link Protocol

7. RPC Reverse Power Control

8. RRI Reverse Rate Indicator

9. UATI Unicast Access Termination Identifier

10. QAM Quadrature Amplitude Modulation

11. QPSK Quadrature Phase Shift Keying

List of References:

1. CDMA2000 High-speed Packet Air Interface Qualcomm


2004-02-022 All rights reserved Page 2 of 36

EV-DO Air interface

This document details the structure and characteristics of forward (downlink) and reverse (uplink) channels. These 1xEV-DO characteristics, which are dictated by EV-DO Physical Layer protocol, vary with requirements of channel type and information data rate.

1.1

1.1.1

Introduction to 1xEV-DO Air Interface

1xEV-DO is a high data rate air interface providing high-speed, high capacity packet data service for wireless users. This service employs the IP protocol (Internet protocol) for seamless data transfer over the Internet or any private IP network. Because experience with the Internet indicates asymmetrical data flow, where downlink data flow is much higher than uplink data flow, downlink and uplink data flow between AT and BTS (base station) are asymmetrical.

The peak data rates for 1xEV-DO are:

Forward link (downlink)=2.4576Mbps

Reverse link (uplink)=153.6Kbps

Although 1xEV-DO base station can be collocated with an IS-95 or a CDMA200, 1x EV-DO requires a separate CDMA carrier that cannot be used by either IS-95 or CDMA2000. The air interface of 1xEV-DO system is transmitted at full power and produces a large interference for other systems.

Structure Reference Model

Figure 1-1 Structure Reference Model

The reference model includes the air interface between the AT and AN.



1.1.2 Protocol Structure

The air interface is hierarchized and defines corresponding interfaces for each layer (and each protocol at each layer). In this case, the later modifications on the layer or protocol are separate. The air interface consists of physical layer, MAC layer, security layer, connection layer, session layer, stream layer, and application layer from top to bottom. Each layer includes one protocol implementing one or multiple layer functions. Each protocol can be negotiated separately.

The protocol transmits messages to the same entity of other end of air interface through signaling message or header. Figure 1-2 illustrates the air interface hierarchical structure:

Figure 1-2 Air Interface Hierarchical Structure

1.

Application Layer: Provides multiple kinds of applications. It provides

default signaling application used to transmit air interface protocol

messages and default packet application used to transmit user data.

Default Signaling Application Protocols:

Signaling Network Protocol (SNP): Provides message transmission services for signaling messages.

Signaling Link Protocol (SLP): Provides fragmentation mechanisms, along with reliable and best-effort delivery mechanisms for signaling messages.



2.

3.

4.

Default Packet Application Protocols

Radio Link Protocol (RLP): Provides retransmission and duplicate detection for an octet aligned data stream.

Location Update Protocol: Defines location update procedures and messages in support of mobility management for the Default Packet Application.

Flow Control Protocol: Defines flow control procedures to enable and disable the Default Packet Application data flow.

Stream Layer: Provides the multiplexing of different application layers.

The air interface can support up to four parallel application streams. The

first stream (Stream 0) always carries singaling, and the other three can

be used to carry applications with different QoS requirements or other

applications.

Stream protocol: Adds header to each stream to be transmitted and

removes the receive stream headers and then transmits the packets

to correct applications.

Session Layer: Provides the address managment, protocol negotiation, protocol configuration and state maintenance.

Session Management Protocol: Provides a means to control the

activation and deactivation of the Address Management Protocol

and the Session Configuration Protocol. It also provides a session

keep-alive mechanism.

Address Management Protocol: Provides Access Terminal

Identifier (ATI) management.

Session Configuration Protocol: Provides negotiation and

configuration for the protocols used in the session.

Connection Layer: Provides connection management to maintain the established AT/AN air link.

Air Link Management Protocol: Provides the overall state

mechanism management of AT and AN during a connection.

Initialization State Protocol: Provides the procedures that an AT

follows to acquire a network and that an AN follows to support

network acquisition.



5.

6.

Idle State Protocol: Provides the procedures that an AT and AN

follow when a connection is not open.

Connected State Protocol: Provides the procedures that an AT

and AN follows when a connection is open.

Route Update Protocol: Provides the means to maintain the route

between AT and AN.

Overhead Message Protocol: Provides broadcast messages

containing information that is mostly used by Connection Layer

protocols.

Packet Consolidation Protocol: Provides transmit prioritization

and packet encapsulation for the Connection Layer.

Security Layer: Provides authentication and encryption.

Key Exchange Protocol: Provides the procedures followed by the

AT and AN to exchange security keys for authentication and

encryption.

Authentication Protocol: Provides the procedures followed by the

AT and AN for authenticating traffic

Encryption Protocol: Provides the procedures followed by the AT

and AN for encrypting traffic.

Security Protocol: Provides the procedures for generation of a

cryptosync that can be used by the Authentication Protocol and

Encryption Protocol.

MAC Layer: Identifies the procedures used to receive or send transmit data over the physical layer.

Control Channel MAC Protocol: Provides the procedures followed

by the AN to transmit and by the AT to receive Control Channel.

Access Channel MAC Protocol: Provides the procedures followed

by the AT to transmit and by AN to receive the Access Channel.

Forward Traffic Channel MAC Protocol: Provides the procedures

followed by AN to transmit and by AT to receive the Forward Traffic

Channel.



7.

1.1.3

Reverse Traffic Channel MAC Protocol: Provides the procedures

followed by the AT to transmit and by the AN to receive the Forward

Traffic Channel.

Physical Layer: Provides channel structure, frequency, power output, modulation and coding specifications for the forward and reverse links.

1xEV-DO Channel Structure

The physical layer of 1xEV-DO provides channel structure, frequency, power output, modulation and coding specifications for the forward and reverse links. The channel structure defined in the 1x EV-DO Physical Layer is shown in Figure 1-4:

Figure 1-3 Forward Channel Structure of 1xEV-DO

Figure 1-4 Reverse Channel Structure of 1xEV-DO



1.1.4 Slot Structure

Forward link data is transmitted in successive 26.67ms frames, which are divided into sixteen slots in which packets of data are transmitted. Physical structure of each slot is shown in Figure 1-5:

Figure 1-5 Forward Channel Slot Structure of 1xEV-DO System

The packet data is transmitted on data fragments of the slot. The packets of only one user for a slot are transmitted.

The duration of single packet transmission is determined by data

transmission rate, ranging from 1 slot to 16 slots.

1.2

The pilot and control information is intervened to the fixed interval of

each frame and sent to AT.

The destination AT information capsule of packet transmission is

included in the packet.

The reverse data link adopts the structure similar to that of 1x, but no the

discrimination of FCH and SCH, adopting 26.667ms frames.

Forward Link Channels

In the 1xEV-DO system, a single forward link channel is divided into four time-division sub-channels, which are:

Data traffic

Control Channel

Pilot

Medium Access Control (MAC)



1.2.1

1.

Forward Channel Structure

Each active user is assigned one of 59 Walsh codes from a 64-order set (5-63), where five codes are pre-assigned. Therefore, a single carrier can be time-divided by 59 active users. This means that although at any one time, only one user is actively receiving data over the data traffic channel, at most 59 users are assigned logical channels on the carrier. A traffic channel assignment indicates the air resources are assigned to the user. The parameter “carrier max. User Number” (see Guide to CDMA EVDO BSS Network Planning Parameter Configuration) can be used to constrain the active user number. The actual number of channels that can be assigned is determined a Maximum Number of Users Supported EMS parameter. Considering that data transfer occurs for a small fraction of the time during a typical downloading pages, causing the AT to enter in and out of a dormant mode at which time the AT surrender is channel assignment. Therefore, the number users that during can be served during busy hour periods may be greater than Maximum Number of Users Supported value.

Transmit Power

Because the data channel is time-divided, there is no need for transmit power sharing as in IS-95 and CDMA2000. Therefore, the base station can transmit traffic data at full power to produce the highest carrier to noise (Eb/No) ratio, allowing high data rate transmission.

In contrast, CDMA2000 base station transmit power must be shared with the pilot, paging, sync and traffic channels as shown in Figure 1-6; while, in 1xEV-DO data transmission is time-divided with small bursts of MAC and pilot pulses. The differences are shown in Figure 1-6:

Figure 1-6 Comparison of CDMA2000 and 1xEV-DO Base Station Transmit Power Sharing



2. 1xEV-DO Frame and Slot Structure

Forward data traffic channel is transmitted within 26.67ms frames, as opposed to 20ms frames in IS-95. Each frame, which consists of 32,768 chips, is divided into sixteen 1.67ms 2048-chip slots as shown in Figure 1-7. The slots are, in turn, divided into two 1024-chip half slots in which the transmission of control and traffic channels, and pilot pulses, MAC, control and traffic channels are time-divided.

Figure 1-7 Forward link slot structure

When no data is transmitted, the MAC and pilot channels are transmitted during their correct timing sequence within the idle slot. Each MAC channel is composed of up 64 code channels, which are atrhogonally spread by 64-order Walsh codeword and BPSK-modulated on a particular phase of the carrier. MAC channel is composed of three sub-channels, including, Reverse Power control

channel, DRCLock channel and reverse activity channel.

1.2.2

1.

Traffic Channel

Forward Link Channel Modulaiton

The different data rates available in 1xEV-DO are achieved by varying the modulation types, Turbo code rate and preamble chips, as shown in Table 1-1:

Table 1-1 Forward link data rates

Data Rate (kbps) Characteristics

38.4 76.8 153.6 307.2 307.2 614.4 614.4 921.6 1228.8 1228.8 1843.2 2457.6

Bits per Packets 1024 1024 1024 1024 2048 1024 2048 3072 2048 4096 3072 4096

Modulation Type QPSK QPSK QPSK QPSK QPSK QPSK QPSK 8PSK QPSK 16QAM 8PSK 16QAM



Preamble Chips 1024 512 256 128 64 128 64 64 64 64 64 64

Code Rate 1/5 1/5 1/5 1/5 1/3 1/3 1/3 1/3 1/3 1/3 1/3 1/3

Physical layer packet duration (ms)

26.67 13.33 6.67 3.33 6.67 6.67 3.33 3.33 3.33 3.33 -- --

Number of slots 16 8 4 2 4 1 2 2 1 2 1 1

Code Rate

The 1xEV-DO uses parallel codes and Turbo decoding techniques, enabling utilization of frame sizes larger than IS-95 and CDMA2000. Code rates of R=1/5 and 1/3 are used on forward channels, and code rates of R=1/4 and 1/2 are used on reverse channels. The code rate R factor identifies the ratio of the number of information bits to total number of information bits plus overhead correction bits transmitted. An R=1/5 factor indicates that for every one information bit transmitted, four correction bits are transmitted to greatly improve the accuracy of the information being transmitted.

Modulation Type

The channel interleaver is provided for modulator and the modulator outputs same-phase modulation and quadrature modulation.

With the exception of 921.6kbps, rates from 38.4kbps to 1228.8kbps are achieved through quadrature phase shift keying (QPSK) modulation as opposed to binary phase shift keying (BPSK) used in IS-95. Groups of two successive channel interleaver output symbols shall be grouped to form QPSK modulation symbols. Each group of two adjacent block interleaver output symbols shall be mapped into a complex modulation symbol. Figure 1-8 shows the signal constellation of the QPSK modulator:



Figure 1-8 QPSK Constellation

The data rates at 921.6kbps and 1843.2kbps are achieved through 8PSK, which produces a 3-bit symbol per cycle. This modulation scheme can be illustrated by the constellation drawing shown in Figure 1-9. Groups of three successive channel interleaver output symbols shall be grouped to form 8-PSK modulation symbols. Each group of three adjacent block interleaver output symbols shall be mapped into a complex modulation symbol. Figure 1-9 shows the signal constellation of the 8-PSK modulator:

Figure 1-9 8PSK Constellation



Data rates at 1228.8(2) kbps and 2457.6kbps are achieved through 16QAMquadrature phase shift/amplitude modulation (16-QAM) to produce a 4-bit symbol per cycle. The 16-QAM modulation scheme uses a combination of QPSK, yielding a 2-bit value and amplitude modulation, and also yielding a 2-bit value where the combination of both results in a 4-bit symbol. The modulation scheme can be illustrated by the constellation drawing shown in Figure 1-10.Groups of four successive channel interleaver output symbols shall be grouped to form 16-QAM modulation symbols. Each group of four adjacent block interleaver output symbols shall be mapped into a complex modulation symbol. Figure 1-10 shows the signal constellation of the 16QAM modulator:

Figure 1-10 Signal Constellation for 16QAM Modulation

Bits Per Packet

The bit size of the transmitted forward traffic data channel packets varies from 1024 bits, 2048 bits, 3072 bits, and 4096 bits. A forward traffic channel physical layer contains one, two, three or four forward traffic channel MAC layers, depending on the transmission rate. The bit size of the forward traffic channel packets received from the MAC layer is fixed at 1002-bits, as shown in Figure 1-11:



Figure 1-11 Physical Layer Packet of Forward Traffic Channel

Regardless of the sizes of the packet to be transmitted, a Frame Check Sequence (FCS) is performed on the 1002-bit packets received from the MAC layer. The FCS is a cyclic redundancy (CRC), which is a calculation producing 16-bit value which is a function of the distribution of all the “1” bits in the 1002-bit MAC layer packet. When a 1024-bit packet is to be transmitted, the 16-bit CRC value is concatenated with the 1002-bit packet MAC layer packet and a 6-bit tail to form the 1024-bit physical layer packet. The six bits that provide the packet tail are tacked to the very end of physical layer packet, and are always 0-bit values.

After receiving physical layer packet, the AT receiving the packet will perform its own CRC calculation on the 1002-bit MAC layer value to validate the correctness of the transmitted physical layer packet. If the 16-bit CRC value computed by the AT matches the 16-bit CRC value transmitted in the physical layer packet, there is a good possibility that the packet received by the AT is uncorrupted.

When a 2048-bit, 3072-bit, or 4096-bit packet is transmitted, the 2, 3, or 4 MAC Layer packets are concatenated together to form a single physical layer packet. A single FCS is calculated regardless of the number of MAC layer packets encapsulated in the physical layer packet, resulting in one 16-bit CRC value which is tacked onto the end of the physical layer packet, just before the 6 tail bits. To fill the physical layer packet to its appropriate 2k, 3k, and 4k bit sizes, 22-bit padding (pad) is inserted after



the 1002 bit MAC layer packets, as shown in the 22 bit pad bits are encoded as “0” bits, which are ignored by the AT.

2.

1.2.3

Forward Traffic Channel Preamble

To assist the AT in synchronizing to the changing data rates, a sequence of preamble bits must be transmitted together with each traffic and control channel physical layer packets. The preamble sequence is covered by a 32-chip bi-orthogonal sequence, which is repeated at least once depending on the transmit mode. The preamble chips are inserted within the data portion of the slot clock period prior to the start of the packet transmission. If the total number of preamble chips to be inserted exceeds the 400-chip data portion of the half-slot period, the preamble chips are time-multiplexed with the MAC and pilot channel chips.

Control Channel

The functions of IS-95 sync and paging channels are combined into a single control channel in the 1xEV-DO. The control channel, which is interlaced with the transmission of traffic data, is transmitted every 256 slot (426.67ms), for 13.33ms duration to transmit control packet capsule. The control channel is 8 slots wide, and in the same manner as the traffic data channel, each slot is divided into two 1024-chip half slots in which the transmission of control channel data modulation, pilot channels, and MAC channels are time-divided.

Figure 1-12 Time-division multiplexing of Control Channel

Control Channel Physical Layer Packet



The bit size of control packets is fixed at 1024 bits. A FCS is performed on the1002 bit packets received from MAC layer. The FCS cyclic redundancy (CRC) calculation produces a 16-bit value, which is a function of the distribution of all the “1” bits in the 1002-bit MAC layer packet. The 16-bit CRC value is concatenated with the 1002-bit MAC layer packet and a 6-bit encoder tail (all “”0) to form the physical layer packet of control channel, as shown in Figure 1-13:

Figure 1-13 Control Channel Structure Physical Layer Packet Bit Size

Just as for traffic data, the AT receiving the packet will perform its own CRC calculation on the 1002-bit MAC layer value to validate the correctness of the transmitted physical layer packet. If the 16-bit CRC value computed by the AT matches the 16-bit CRC value transmitted in the physical layer packet, there is a good possibility that the packet received by the AT is uncorrupted.

1.2.4

1.2.5

Pilot Channel

The Pilot Channel shall consist of all “0” symbols transmitted on the I-Channel with Walsh mask “0”. Each slot shall be divided into two half slots, each of which contain a pilot burst. Each pilot burst shall have a duration of 96 chips and be centered at the midpoint of the half slot.

Using the full power for the pilot burst provides the highest possible pilot SNR so that an accurate estimate can be obtained quickly to estimate the radio environment.

MAC Channel

The MAC Channel shall consist of three sub-channels: the Reverse Power Control (RPC) Channel, DRCLock Channel, and the Reverse Activity (RA) Channel. Each MAC Channel symbol shall be BPSK modulated on one of 64-order Walsh codewords (masks). The Walsh functions allocated for the MACIndex value are shown below:



W64i/2 where, i=0,2,4,…,62

W64(i-2)/2+32 where, i=1,2,…,63

i is MACIndex value. When the MACIndex value SN is an even number, the MAC channel is allocated for same phase (I) modulation group. When MACIndex value SN is a odd number, the MAC channel is allocated for same phase (Q) modulation group.The MAC symbol Walsh mask shall be transmitted four times per slot in bursts of 64 chips each. A burst shall be transmitted immediately preceding each of the pilot bursts in a slot and a burst shall be transmitted immediately following each of the pilot bursts in a slot.

The MACIndex comparison when MAC channel and preamble are used is shown in Table 1-2:

Table 1-2 MACIndex Comparison

MACIndex Use MAC channel or not Use Preamble or not

0 and 1 NO NO

2 NO Control channel at the rate of 76.8kbps

3 NO Control channel at the rate of 38.4kbps

4 RA channel NO

5 NO Broadcast channel

6–53 Used for RPC channel and DRCLock channel transmission

Used for forward traffic channel transmission

MAC channel symbol shall be transmitted on the Walsh channel and MAC channel gain can be regarded as time function to change relevant powers. Quadrature Walsh channel should be adjusted to remain the unstable total transmit powers.

The modulation parameters of MAC channel are shown in Table 1-3:

Table 1-3 MAC Channel Modulation Parameters

Parameters RPC Channel DRCLock channel RA channel

Rate (bps) 600×(1--1/DRCLockPeriod) 600/(DRCLockLength×DRCLockPeriod) 600/RABLength

Bit repetition

factor

1 DRCLockLength RABLength

Modulation (channel)

BPSK (I or Q) BPSK (I or Q) BPSK (I)

Modulation symbol rate

2400×(1--1/DRCLockPeriod) 2400/DRCLockPeriod 2400



(bps)

Walsh mask length

64 64 64

Walsh sequence repletion

factor

4 4 4

PN chips/slot

256 256 256

PN chips/bit

256 256× DRCLockLength 256×RABLength

1.2.6

1.

2.

Working Mode

Multi-slot Packet Transmission

The packet data to be transmitted is redundant-coded by the Turbo coder, and the code rate is specified by packet transmission rate. Incremental redundancy is used construct multi-slot transmission structure of physical layer packets at different rates. For example, even through the specification allots four slots to send a packet when transmitting at a 153.6kbps rate, enough packet information bits are sent in each slot to enable the AT to recover and validate the whole packet in less than the specified four slots.

When transmitting at this rate, a redundancy factor of five is used. If the packet data received by AT cannot be validated after the first slot transmission, the packet information transmitted in the second slot provides more and different redundant bits to complement the data bits sent in the first slot, providing AT with a greater opportunity to validate the packet.

If the packet still cannot be validated, different redundancy bits are transmitted in subsequent slots to further increase the opportunity for the AT to validate the packet. In this way, when the RF radio environment is favorable, the receiver can obtain enough data information in a slot period to validate the packet.

Slot Data Interleaving

The Forward Traffic Channel and Control Channel physical layer packets can be transmitted in 1 to 16 slots. When more than one slot is allocated, the transmit slots shall use a 4-slot interleaving. That is, the transmit slots of a physical layer packet shall be separated by three intervening slots, and slots of other physical layer packets shall be transmitted in the slots



between those transmit slots. If a positive acknowledgement is received on the reverse link ACK Channel before all the allocated slots have been transmitted, the remaining un-transmitted slots shall not be transmitted and the next allocated slot may be used for the first slot of the next physical layer packet transmission.

Figure 1-14 and Figure 1-15 illustrate the multislot interleaving approach for a 153.6 kbps Forward Traffic Channel with DRCLength of one slot. The 153.6 kbps Forward Traffic Channel physical layer packet use four slots, and these slots are transmitted with a three-slot interval between them, as shown in the figures. The slots from other physical layer packets are interlaced in the three intervening slots. After receiving each slot packet, the AT calculates the FCS to confirm whether packet data information is received correctly. Figure 1-14 shows the case of a normal physical packet termination.

Figure 1-14 Multi-slot Data Interleaving With Normal Termination

In this case, the AT transmits NAK responses on the ACK channel after the first three slots of the physical layer packet are received indicating that is was unable to correctly receive the Forward Traffic Channel physical packet after only one, two, or three of the nominal four slots. An ACK or NAK is also transmitted after the last slot is received.

The AT transmits an ACK response on the ACK Channel after the first three slots are received indicating that it still cannot correctly receive the Forward Traffic Channel physical layer packet. The AT still must transmit ACK or ANK after the last slot. The ACK transmission indicates that AT receives correctly the packet. If NAK transmission indicates that packet



may be retransmitted within subsequent time at lower rate or RF radio environment of AT is more favorable.

Figure 1-15 shows the case where the forward traffic channel physical layer packet transmission is terminated early.

Figure 1-15 Multi-slot Physical layer packet with early termination

The AT transmits an ACK response on the ACK Channel after the third slot is received indicating that it has correctly received the physical layer packet. When the AN receives such an ACK response, it does not transmit the remaining slots of the physical layer packet. Instead, it may begin transmission of any subsequent physical layer packet.

3. Dynamci Rate Control

The forward transmission rate varies with the radio environment of AT. The rate changes once at least in a 1.667ms slot. The AT continuously monitors the quality of receive pilot pulses from all sectors in the active set. In response, the AT sends back a Data Rate Control (DRC) report to the target base station of active set.

The DRC report identifies the sector with the highest C/I ratio and the highest rate in which the AT can receive quality data from the sector within a margin to insure a low erasure rate. The DRC mask specifies transmit sector and the DRC value is used to specify the required transmit rate.



4. Virtaul Soft Handoff

The selection from one sector to another is called virtual soft handoff. For the soft handoff performed in IS-95, the mobile may simultaneously interact with two or more sectors to realize a signal gain. For the virtual soft handoff performed in the 1xEV-DO, the AT selects a sector with the best signal to provide service so that acquired gain is less than signal gain after the consolidation.

Figure 1-16 Virtual Soft Handoff

When the DRC report from an active AT identifies (points to) Sector 1 as its best serving sector, Sector 1 sends forward data request to AN and AN starts to transmit the data packet. When the DRC reports from the AT point to Sector 2 as its best serving sector for a definable period, sector2 sends forward data request to AN. And then, sector1 sends forward termination indication to AN to confirm that the last frame is transmitted successively. After receiving forward data request from sector2, AN sends a “Flush” command to sector1, and starts to send packet data to the sector2.

5. Scheduling Algorighm

To maximize the overall sector throughput, 1xEV-DO uses a scheduling algorithm that takes advantage of a multi-user pool vying for time on the carrier. Another primary factor in determining current scheduling algorithm is to remain the data throughput Tk and DRC request rate DRCk within recent period of active users. Compare with the DRCk/Tk of all the active users in current sector and select the maximum one for service.



1.3

As a result, when the sum of all the request transmission data is larger than air interface capability, the data throughput of each subscriber is directly proportional to serving rate of environment request. It is fair for each subscriber. The radio environment features random fading and DRC changes dramatically, and the system will provide the service for the subscriber with best DRC to facilitate improving the system throughput.

Reverse Link Traffic Channel

The reverse channel structure consists of a Traffic Channel and an Access channel. The access channel is divided into two sub-channels, which are:

Pilot, for coherent demodulation at the base station.

Data, used by AT to initiate uplink data transmission.

The reverse traffic channel is divided into four sub-channels, which are:

Pilot, for coherent demodulation at the base station.

Reverse Rate Indicator (RRI): which indicates to the base station

the rate in which uplink (reverse) traffic channel is transmitted.

Data Rate Control (DRC): Used by AT to indicate forward traffic

channel data rate requested on forward channel and selected

serving sector for AN.

Acknowledge (ACK): Acknowledges if physical layer packets

transmitted on forward traffic channel are successfully or

unsuccessfully received.

Data: Used by AT to transmit uplink data.

Uplink data is transmitted in successive 26.67ms frames at five different data rates from 9.6kbps to 153.6kbps, as shown in Table 1-4:

Table 1-4 Reverse link data rate

Data Rate (kbps)

9.6 19.2 38.4 76.8 153.6

Bits per packets

256 512 1024 2048 4096

Modulation type

BPSK BPSK BPSK BPSK BPSK

Preamble 1024 512 256 128 64



chips

Code rate 1/4 1/4 1/4 1/4 1/2

PN chips/ bits 128 64 32 16 8

Physical layer packets duration (ms)

26.67 26.67 26.67 26.67 26.67

1.3.1 Reverse Traffic Channel Structure

The structure of reverse traffic channel is shown as the following two figures:

Figure 1-17 Reverse Channel Structure for the Reverse Traffic Channel (Part 1 of 2)



Figure 1-18 Reverse Channel Structure for the Reverse Traffic Channel (Part 2 of 2)

The forward channel uses time multiplexing to separate its four sub-channels. For the Reverse Traffic Channel, the encoded RRI Channel shall be time-division multiplexed with the Pilot Channel. This time-division-multiplexed channel is, the DRC Channel, the ACK Channel, and the Data Channel shall be orthogonaly spread by Walsh functions (also referred to as Walsh mask) of length 4, 8, 16 t a fixed chip rate of 1.2288 Mcps. Each Reverse Traffic Channel shall be identified by a distinct user long code.

1.3.2 Pilot /RRI Channel

The AT shall transmit un-modulated symbols with a binary value of “0” on the pilot channel. The transmission of the Pilot Channel and the RRI Channel shall be time multiplexed on the same Walsh channel and transmitted at the same power.

The RRI Channel is used by the AT to indicate the data rate at which the Data Channel is transmitted. The data rate is represented by a three-bit RRI symbol at the rate of 3-bit symbol per 16-slot physical layer packet.



Each RRI symbol shall be encoded into a 7-bit codeword by a simplex encoder. Then, each codeword shall be repeated 37 times and the last 3 symbols shall be disregarded. The resulting 256 binary symbols per physical layer packet shall be time-division multiplexed with the Pilot Channel symbols and span the same time interval as the corresponding physical layer packet. The time-division-multiplexed Pilot and RRI Channel sequence shall be spread with the 16-chip Walsh function W0

16 producing 256 RRI chips per slot. The RRI chips shall be time-division multiplexed into the first 256 chips of every slot as shown in Figure 1-19:

Figure 1-19 Time-division multiplexing of reverse pilot channel and RRI channel

When no physical layer packet is transmitted on the Reverse Traffic Channel, the AT shall transmit the zero data rate RRI codeword on the RRI channel. The Pilot Channel and RRI Channel shall be transmitted on the I-Channel.

1.3.3 ACK Channel

The ACK channel is used by the AT to inform the AN whether a physical layer packet transmitted on the forward channel has been received successfully or not.

The AT shall transmit an ACK channel bit in response to every Forward Traffic Channel slot that is associated with a detected preamble directed to the AT. The AT shall transmit at most one redundant positive ACK in response to a Forward Traffic Channel slot that is detected as a continuation of the physical layer packet that has been successfully received. Otherwise, the ACK channel shall be gated off.

The ACK channel shall be BPSK modulated. A “0” bit shall be transmitted on the ACK channel if a Forward Traffic Channel physical layer packet has been successfully received. Otherwise, a “1” bit (NAK) shall be



1.3.4

1.3.5

transmitted. A Forward Traffic Channel physical layer packet is considered successfully received in slot n on the Forward Channel, the corresponding ACK channel bit shall be transmitted in slot n+3 on the Reverse Channel.

The ACK Channel transmission shall be transmitted in the first half of the slot and shall last for 1024 PN chips. The ACK Channel shall use the Walsh channel identified by the Walsh function W4

8 and shall be transmitted on the I channel.

DRC Channel

The DRC channel is used by the AT to indicate to the AN the selected serving sector and the requested data rate on the forward traffic channel. The requested Forward Traffic Channel data rate is mapped into a four-bit DRC value as specified by the Forward Traffic Channel MAC Protocol. Any 8-order Walsh function corresponding to the selected serving sector is used to spread the DRC channel transmission. The mask mapping is defined by te public data DRCCover from the Forward Traffic Channel MAC Protocol.

The DRC value shall be block encoded to yield 8-bit bi-orthogonal codewords. Each DRC codeword shall be transmitted twice per slot. Each bit of a repeated codeword shall be spread by an 8-order Walsh function Wi

8. Where, i is equals DRCCover. Each Walsh chip of the 8-order Walsh function shall be further spread by the Walsh function W8

16. The DRC channel shall be transmitted on the Q channel.

Data Channel

The Data Channel shall be transmitted at the data rates give in Table 1-5. Data transmissions shall only begin at slot FrameOffset within a frame. The FrameOffset parameter is public data of the Reverse Traffic Channel MAC Protocol, all data transmitted on the Reverse Traffic Channel shall be encoded, block interleaved, sequence repeated, and orthogonally spread by Walsh function W2

4.

Table 1-5 Parameters for reverse link encoder

Data rate (kbps)

Physical layer packet bit size

Reverse rate index

Code rate

Coder output block length

Code symbol rate (kbps)

Interleaving

Repeat rate

Modulation

Symbol rate (kbps)

PN chip per packet

9.6 256 1 1/4 1024 38.4 8 307.2 128



19.2 512 2 1/4 2048 76.8 4 307.2 64

38.4 1024 3 1/4 4096 153.6 2 307.2 32

76.8 2048 4 1/4 8192 307.2 1 307.2 16

153.6 4096 5 1/2 8192 307.2 1 307.2 8

For example, when transmitting at the 9.6kbps data, the 256-bit packet is spread by undergoing the following:

1.

Turbo encoding at a 1/4 code rate, producing 1024 (254×4) code

symbols that are clocked at 38.4kbps (9.6*4) code symbol rate.

Interleave packets are repeated effectively multiplying the 1024

symbols by a factor of 8 (8,192), producing a modulation symbol rate

of 307.2kbps (38.4*8).

Spread by 4-chip Walsh code function W24, producing four chips per

symbol which is clocked at the 1.2288Mcps (4X 307.2 kbps).

In accordance with the information given in Table 1-5, at the 9.6kbps data rate, the number of PN chips per physical layer packet is 128. This number is obtained by dividing the 1 .2288 Mcps chip rate by the 9.6 kbps data rate.

This data rate is the slowest data rate on the reverse channel. The AT will start out transmitting at this data rate to ensure that the base station can acquire the AT, regardless of the current RF environment conditions. If the conditions are favorable, AT is permitted to transmit at a higher data rate. Although the 1.2288Mcps chip rate remains the same regardless of the data rate, higher rates are achieved by reducing packet interleaving repeat rates. At the same time, to offset the reduction of interleaving packet repeat rate, the physical layer packet doubles for each in increasing data rates from 1024 to 2048. Because the data is transmitted at the 1.2288 Mcps, as the physical layer packet size increases, the number of chips per bits is reduced, increase the transmit data rate. At reverse rate index 5, the Turbo code rate is reduced from 1/4 to 1/2 allowing the packet size to be increase from 2048 to 4096, thereby doubling the data rate.

Physical Layer Pakcet Size

When the transmit data rate incrementally doubles from 9.6 kbps to 153.6 kbps, the MAC layer packet bit size used to construct physical



traffic data packet also incrementally doubles from 234 to 4074 as shown in Figure 1-20.

Figure 1-20 Physical Layer Packet of Reverse Traffic Channel

A single FCS is calculated regardless of the MAC layer packet bit size used to construct the physical layer packet. The FCS calculation results in a 16-bit CRC value, which is tacked on to end of the physical layer packet just before the 6 tail bits.

2.

3.

Turbo Encoder/Interleaver

Except for when the 153.6 kbps data rate is used, the content of data channel is encoded at 1/4 code rate by the Turbo encoder/ Interleaver. When the 153.6 kbps data rate is used, the content of data channel is encoded at a 1/2 code rate. The reverse link encoder parameters are shown in Table 1-5.

The redundancy provided by the Turbo encoder enables the base station to reconstruct the received data when a small number of bits sporadically distributed throughout the received bit pattern are corrupted. To minimize the effect of RF noise spikes or shadow fading that will corrupt large clusters of bits from preventing bit pattern reconstruction at the base station, the Turbo-encoded bit pattern is interleaved.

Interleaving will pseudo-randomly scramble bit patterns at the output of Turbo encoder/interleaver. Prior to bit-patter reconstruction at the base station, the received bits are unscrambled. As a result, if any large cluster or bits were corrupted during transmission, the unscrambling process will sporadically distribute the corrupted bits throughout the received bit pattern, enabling the reconstruction of the receive bits.

Walsh Code Spreading

The output of Turbo encoder/interleave is orthogonally spread Walsh function. Then, ACK Channel, DRC Channel, and Data Channel chips are scaled by a factor and the factor provides the gain of each channel to



pilot channel. The relative gains are specified by the parameters of MAC Protocol public data.

The pilot and scaled ACK sequences to form resultant new I sequence. The scaled DRC and Data Channel sequences form resultant Q-Channel sequence.

4.

1.3.6

Quadrature Spreading

The I-Channel and Q-Channel sequences are quadrature spread. The quadrature spreading shall occur at the chip rate of 1.2288Mcps, and it shall be used for the Reverse Traffic Channel and Access Channel. The quadrature spreading operation shall be equivalent to a complex multiply operation of the resultant I-Channel and resultant Q-Channel sequences by the PNI and PNQ PN sequences.

The I and Q PN sequences, that is, PNI and PNQ shall be obtained from the long-code PN sequences, UI and UQ , and the access terminal common short PN sequences, PI and PQ.

Access Channel

The access channel data is transmitted by the AT to either initiate communication with the AN or to respond to a message directed to the AT. The access channel is divided into two sub-channels, data channel and pilot channel.

The access channel is always transmitted at a fixed 9.6 kbps data rate. The physical layer access message packet is 256 bits wide and consists of a 234-bit MAC layer packet followed by a 16-bit FCS value and a 6-bit tail, shown in Figure 1-21:

Figure 1-21 Physical Layer Packet of Access Channel

The access probe consists of a preamble followed by one or more access channels physical packets. During the preamble transmission, only the pilot is transmitted. During the access channel physical layer packet transmission, both the pilot channel and the data channel are



transmitted. The output power of Pilot Channel during the preamble portion of an access probe is higher than its is during the data portion of access probe by and amount such that the total output power of the preamble and data portions of the access probe are the same as shown in Figure 1-22:

Figure 1-22 Access probe

1. Generation of Access Channel

The generation of reverse access channel is illustrated in Figure 1-23:



Figure 1-23 Generation of access channel

2. Data Channel

The access channel is encoded by Turbo encoder at a 1/4 code rate, producing a 1024-bit symbol. Therefore, the code symbol rate is four times the 9.6 kbps access channel data rate, or 38.4 kbps. To improve



3.

the ability of base station to restore the Turbo coded in the event of transmission fading and interface, the access channel data is interleaved by the channel interleaver and the interleaved packet data is repeated eight times, increasing the modulation symbol rate to (8 X 38.4 kbps) 307.2 kbps.

The output of Turbo encoder/interleaver is spread by Walsh function quadrature, and the amplitude of resulting chip sequence is scaled, through the data channel relative gain control, by a factor relative to the amplitude of pilot chip sequence. The relative gain is specified by parameters of MAC protocol public data. For details, see Guide to CDMA EVDO BSS Network Planning Parameters Configuration. The output of data channel relative gain control provides the Q input for quadrature spreading.

Pilot Channel

Similar to the traffic pilot channel, the access pilot channels are also un-modulated symbols having a binary 0 bit value. However, unlink the traffic pilot channel that is time-multiplexed with the RRI channel, the access pilot channel is continuously transmitted using a 16-chip Walsh code function number 0.

ev-do air interface -20050106-a-1.0

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