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CDMA2000 1x EV-DO System Principles ZTE CORPORATION ZTE Plaza, Keji Road South, Hi-Tech Industrial Park, Nanshan District, Shenzhen, P. R. China 518057 Tel: (86) 755 26771900 800-9830-9830 Fax: (86) 755 26772236 URL: http://support.zte.com.cn E-mail: [email protected]

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Page 1: 02 EVDO Principle

CDMA2000 1x EV-DO System Principles

ZTE CORPORATION ZTE Plaza, Keji Road South, Hi-Tech Industrial Park, Nanshan District, Shenzhen, P. R. China 518057 Tel: (86) 755 26771900 800-9830-9830 Fax: (86) 755 26772236 URL: http://support.zte.com.cn E-mail: [email protected]

Page 2: 02 EVDO Principle

LEGAL INFORMATION Copyright © 2006 ZTE CORPORATION. The contents of this document are protected by copyright laws and international treaties. Any reproduction or distribution of this document or any portion of this document, in any form by any means, without the prior written consent of ZTE CORPORATION is prohibited. Additionally, the contents of this document are protected by contractual confidentiality obligations. All company, brand and product names are trade or service marks, or registered trade or service marks, of ZTE CORPORATION or of their respective owners. This document is provided “as is”, and all express, implied, or statutory warranties, representations or conditions are disclaimed, including without limitation any implied warranty of merchantability, fitness for a particular purpose, title or non-infringement. ZTE CORPORATION and its licensors shall not be liable for damages resulting from the use of or reliance on the information contained herein. ZTE CORPORATION or its licensors may have current or pending intellectual property rights or applications covering the subject matter of this document. Except as expressly provided in any written license between ZTE CORPORATION and its licensee, the user of this document shall not acquire any license to the subject matter herein. The contents of this document and all policies of ZTE CORPORATION, including without limitation policies related to support or training are subject to change without notice.

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Contents

Chapter 1..........................................................................1

CDMA2000 1x EV-DO System Principles.........................1

Introduction .........................................................................1 Forward Channels .................................................................5 Reverse Channels .................................................................9

Chapter 2........................................................................16

Keys Technology in 1x EV-DO .......................................16

Introduction ....................................................................... 16 Service Flow....................................................................... 24 Comparisons with 1x ........................................................... 30 Review .............................................................................. 31

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Confidential and Proprietary Information of ZTE CORPORATION 1

C h a p t e r 1

CDMA2000 1x EV-DO System Principles

Key points 1. Understand EVDO system development & network structure 2. Understand EVDO channel structure

Introduction

This chapter gives an introduction to system development & network structure and the Forward/Backward Channels of cdma 1x EV-DO system. Upon finishing this chapter you will have a deep understanding of the principles of cdma2000 1x EV-DO technology and be able to differentiate it from cdma2000 1x.

The EVDO system is upgraded version of an IS-95 CDMA mobile radio communication system that provides for high-speed data and voice communication services. Upgrading to EVDO capability allows CDMA cellular and PCS service providers to offer their customers wireless broadband (high-speed Internet) services by upgrading one or more of their IS-95 CDMA radio channels to the EVDO technology. Customers can access the high-speed Internet services through EVDO capable handsets or external modems that connect to their desktop or laptop computers. The EVDO radio channels are an “always-on” system that allows users to browse the Internet without complicated dialup connections.

EV-DO is the abbreviation for “Evolution, Data Only”. As a dedicated technology for high speed data transfer, 1x EV-DO is considered as the upgraded version of 1x. EV-DO is based on IS-856 specification which was developed by Qualcomm and Lucent.

The system structure of 1x EV-DO can be regarded as a combination of the 1x system with an extra wireless component. 1x provides voice and other low speed services while 1x EV-DO focuses on the high speed packed data services. In addition, 1x EV-DO and 1x use different carrier frequency to transfer data. This feature helps optimize both the voice services and the high speed packed data services and ensure them the best performances.

System Overview

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CDMA2000 1x EV-DO System Principles

2 Confidential and Proprietary Information of ZTE CORPORATION

1x EV-DO uses the same frequency bandwidth as narrowband CDMA. The highest data transfer rate is 2.4 Mbit/s.

Take the inheritance from 1x system into account, the 1x EV-DO is compatible with the 1x in wireless features. It can be seen as a new frequency point of 1x. This makes the RF equipments of 1x EV-DO and 1x system replaceable to each other.

The 1x EV-DO system structure is shown Figure FIGURE 1

FIGURE 1 TH E 1 X EV-DO S Y S T E M S T R U C T U R E

AT BTS BSC PCF PDSN

HAMSC

HLR

Internet

AN

AN

A12

A13

AAA

AAA

The Differences from the 1x system:

1xEV-DO is data only, so there is no interface to MSC/HLR.

Packet Data Domain equipment (PDSN、AAA、HA), same as 1X.

Independent Access Network AAA server is added.

2 A interfaces are added. A12 is added for access system authentication, and A13 for interaction between AT roaming Home AN and Foreign AN.

The 1x EV-DO protocol family is shown as FIGURE 2

System Structure

Protocol Family 

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FIGURE 2 TH E 1 X EV-DO P R O T O C O L F AM I L Y

1. Application Layer: The Application Layer provides multiple

applications. It provides the Default Signaling Application for transporting air interface protocol messages and the Default Packet Application for transporting user data.

2. Stream Layer: The Stream Layer provides multiplexing of distinct application streams. Stream 0 is dedicated to signaling and defaults to the Default Signaling Application. Stream 1, Stream 2, and Stream 3 are not used by default.

3. Session Layer: The Session Layer provides address management, protocol negotiation, protocol configuration, and state maintenance services.

4. Connection Layer: The Connection Layer provides air link connection establishment and maintenance services.

5. Security Layer: The Security Layer provides authentication and encryption services.

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6. MAC Layer: The Medium Access Control (MAC) Layer defines the procedures used to receive and transmit over the Physical Layer.

7. Physical Layer: The Physical Layer provides the channel structure, frequency, power output, modulation, and encoding specifications for the Forward and Reverse Channels.

Each layer may contain one or more protocols. Protocols use signaling messages or headers to convey information to their peer entity at the other side of the air-link. When protocols send messages, they use the Signaling Network Protocol (SNP).

1. Different requirements on Voice Services and Data Services, as shown in TABLE 1.

T ABLE 1 TH E 1 X EV-DO’ S R E Q U I R E M E N T S O N V O I C E S E R V I C E S AN D D AT A S E R V I C E

Items Voice Services Data Services

Delay (Processing

Time in total)

Beyond 100ms is

unacceptable

A few seconds delay is almost not detected

as it changes constantly

(Bit Error Rate) BER Not strict Strict (Using ECC to reduce the BER)

Forward/Backward

Data Rate

Adhering to the

symmetry is

required while

performing two

way voice

services

The need to Forward Link on speed is

likely to be several times greater than the

Backward Link (Forward Link: 38.4

kbit/s~2.4 Mbit/s, Backward Link: 4.8

kbit/s~153.6 kbit/s)

Throughput Low throughput

The actual throughput available to any one

user depends on the total number of users

being served and the level of interference

(C/I) present.

2.The Compatibility with IS-95/1X Networks

As shown in FIGURE 3,the 1x EV-DO system band is 1.25 MHz,it has the same spectrum as IS-95/1x.

FIGURE 3 TH E S P E C T R U M O F 1 X AN D 1 X EV-DO

No changes are required to the existing network deployment. The 1x EV-DO system and IS-95/1x can be deployed together on the basis of the existing Base Stations, towers and antennas.

Functions & Features

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Forward Channels

The Forward Channel (AN to AT) provides the connections between AN and each AT. The Forward Channel has following features:

1. The data rate is in a range of 38.4 kbit/s~2457.6 kbit/s; 2. Always at full power transmission, no power control; 3. Selecting the best service area according to the

measurement of C/I in Forward Channel and working at the highest data rate;

4. The subscribers in a certain service area will share a unique data service channel in a way of TDM.

1x EV-DO is an independent system with a new channel structure

The forward channels structure is shown in 错误!未找到引用源。.

FIGURE 4 TH E 1 X EV-DO F O R W AR D C H A N N E L S S T R U C T U R E

1. Pilot channel

The pilot channel is used for the pilot signal transmission from Access Net (AN) to Access Terminals (AT). This signal handles system acquisition, clock synchronization, demodulation, decoding and C/I assessment.

2. Forward MAC channel

The forward MAC channel is composed of Reverse Power Control (PRC) channel, Reverse Activation (RA) channel and Data Rate Control (DRC) locking channel.

PRC channel is used for power control of AT which is transferring data on the Reverse Channel.

RA is used to dynamically control the workload of Reverse Channel. When overload is detected, the bit stream in RA

Channel Types and Functions

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6 Confidential and Proprietary Information of ZTE CORPORATION

channel forces the AT which are transmitting data on RA randomly to lower their reverse data rate in order to reduce the emission power and the collisions when accessing terminals.

In case the AN can not receive the DRC signals from an AT, the DRC channel will stop the particular AT from sending data to AN.

3. Forward traffic channel

Forward traffic channel is used by AN to send data. It works at full power when sending data. Forward traffic channel power control but rate control.

4. Forward control channels

Forward control channel is used to broadcast common configuration parameters from AN to AT. Additionally, it also sends signalling messages to a particular AT in case the traffic channels are not activated. These messages are used in the way of TDM on forward channel by individual user. Moreover, forward control channel can be used by AN to send data.

In forward channel series, most of the channels work at TDM mode and transmit to AT at full power mode. However, the RPC and RA in MAC channel work at CDM mode.

The TDM mode of forward channels is presented by channel time slot structure. Time slot is the basic unit to depict a channel. 1 time slot equals to 1.67ms. There are two types of time slots – activated time slot and idle time slot. The former bears the information of traffic channel and control channel.

The time-slot structure of forward channels is shown in FIGURE 5 .The data section involves the information about the control channel and traffic channel.

FIGURE 5 TH E T I M E -S L O T S T R U C T U R E O F 1 X EV-DO F O R W AR D C H AN N E L S

Time-slot Structure of

Channel

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Frame is the data unit for forward channels. 16 time slots consist of a frame which is 26.67ms long.

1. Pilot Channel

The sector uses all the activated forward channels all along to transmit pilot signals.

2. Forward Control Channel

There are two different data transfer rates of forward control channel (76.8kbit/s and 38.4kbit/s). Its time slot structure is different from that of the forward traffic channel.

3. Forward MAC Channel

There are four identical MAC contents in one time slot.

4. Forward Traffic Channel

AN modulates data transfer rate in forward traffic channel according to DRC request from AT. The rate ranges from 38.4kbit/s to 2.4576Mbit/s. Packet was introduced into forward traffic channel as the data unit. It contains messages of 1024bits, 2048bits, 3072bits and 4096bits with the duration from 1.67ms to 26.67ms (1~16 time slots).

In comparison with 1x, the modulation mode was improved significantly in 1x EV-DO in order to reach a high data throughput. Two efficient modulation modes (8-PSK and 16QAM) were introduced into AN side.

8-PSK is an extension of QPSK. In 8-PSK, eight different carrier frequency phases are corresponding to eight different binary codes (000, 001, 010, 011, 100, 101, 110 and 111). The usage of band is improved as each modulation signal is corresponding to a 3bit-data.

16-QAM is another extension of QPSK. It uses two different amplitudes. Each signal is corresponding to a 4bit-data. In other words, 16-QAM is a combination of ASK and PSK.

1x EV-DO adopts QPSK、8-PSK and 16-QAM as its modulation modes. Its encoding technologies include interleaving, insertion, repetition and symbol-multiplexing. In addition, quadrature spread and Base Band filtering technologies were also introduced into 1x EV-DO.

1. Pilot Channel

Pilot signal is an unmodulated BIT/SK signal (Walsh code is 0).

2. Forward control channel

The forward control channel and the forward traffic channel with same data rate are using a same modulation mode.

The transmission of forward control channel is different from that of the forward traffic channel. It has a leading code which contains a MAC Index 2 (76.8kbits/s) or a MAC index 3 (38.4kbit/s) biorthogonal sequence.

Channel Modulation

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8 Confidential and Proprietary Information of ZTE CORPORATION

It transmits every 400ms with duration of 13.33ms (76.8kbit/s) or 26.66ms (38.4kbit/s). A circle period of the forward control channel is defined as 240 time slots which is synchronized with 1x EV-DO.

3. Forward MAC Channel

The forward MAC channel is comprised of quandrature Walsh channels. It is modulated (Inphase or Quandrature Phase) by BIT/SK at particular carrier frequency.

Each Walsh is identified by a MAC Index value (0~63). This value determines a unique 64bit Walsh cover and a unique modulation phase. If the value is an even number, MAC channel is assigned to the in-phases, otherwise, assigned to quadrature phases.

The relationship between MAC channel and MACIndex is shown in TABLE 2

T ABLE 2 TH E MAC C H AN N E L AN D M ACI N D E X

MACIndex The usage of MAC channel\ The usage of leading code

0 and 1 Not use Not use

2 Not use 76.8 kbit/s control channel

3 Not use 38.4 kbit/s control channel

4 RA channel Not use

5~63 Available to the RPC channel

and DRCLock channel for

transfer

Available to the forward

traffic channel for transfer

RA channel adopts Walsh464 band spread technology and

performs modulation in BIT/SK mode at I channel. PRC channel and DRC locking channel take up MAC channel in a time-sharing manner. Messages come from different terminals are identified by 64-level Walsh codes. These codes are used in modulation by means of BIT/SK in I channels or Q channels. One AN is able to provide 60 Walsh codes. In other words, one AN can serve up to 60 users simultaneously.

4. Forward traffic channel

The forward traffic channel (and control channels) needs some encoding procedures such as Turbo encoding and interleaving. According to different data transfer rate, the forward traffic channels firstly carry out QPSK, 8-PSK or 16-QAM modulations. The modulated code elements are divided into 16 concurrent data flows and each flow is identified by different 16-level Walsh code. These 16 concurrent data flows are modulated again after integration.

A symbol which is corresponding to a data packet will take up 1~16 time slots when the modulated symbols are being mapped to channels. It depends on the data rate and the number of bits a data packet contains. The leading codes (all

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Confidential and Proprietary Information of ZTE CORPORATION 9

zeros) section must be added before mapping. The length of this section depends on the data rate and the number of time slots of a data packet. The leading sections of different user data and control data with different rates are identified by 64-level Walsh codes.

The modulation parameters of forward traffic channels at different data rate are indicated in TABLE 3. In this table, the number of bits, modulation symbols, as well as leading codes are sharing a c data unit – data packet.

T ABLE 3 TH E M O D U L AT I O N P AR AM E T E R S O F 1 X EV-DO F O R W AR D T R AF F I C C H AN N E L

Rate(kbit/s)

Number

of time-

slot

Numb

er of

bit

Turbo

code

Modulation

mode

Modulation

symbol

Leading code

38.4 16 1024 1:5 QPSK 2560 1024

76.8 8 1024 1:5 QPSK 2560 512

153.6 4 1024 1:5 QPSK 2560 256

307.2 2 1024 1:5 QPSK 2560 128

614.4 1 1024 1:3 QPSK 1536 64

307.2 4 2048 1:3 QPSK 3072 128

614.4 2 2048 1:3 QPSK 3072 64

1228.8 1 2048 1:3 QPSK 3072 64

921.6 2 3072 1:3 8-QPSK 3072 64

1843.2 1 3072 1:3 8-QPSK 3072 64

1228.8 2 4096 1:3 16-QAM 3072 64

2457.6 1 4096 1:3 16-QAM 3072 64

Reverse Channels

The reverse channels provide connections between AT and AN. They have the following features:

Data rates is up to 153.6kbit/s;

Soft switch;

Dynamic power control;

Workload of reverse channels is adjusted by rate control.

The structure of 1x EV-DO reverse links is shown in 错误!未找到

引用源。. Channel

Functions and Features

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CDMA2000 1x EV-DO System Principles

10 Confidential and Proprietary Information of ZTE CORPORATION

FIGURE 6 ST R U C T U R E O F 1X EV-DO R E V E R S E L I N K S

1. Reverse Access Channels (Reverse Pilot Channels and Data

Channels)

Reverse Access Channels are used by AT to initiate calls or respond to AN paging messages

2. Reverse Traffic Channels (Pilot Channels, MAC Channels, Data Channels and ACK, MAC Channels is comprised of DRC and PRI)

Pilot channel

Coherent demodulation

DRC sub-channel

DRC channels are used by AT to give instructions to AN. These instructions include the requested data rate of forward traffic channels and the service areas selected by forward channels. DRC Value and DRC are two types of information in DRC channels.

RRI channel RRI channels are used to indicate the data rate of in operation reverse data channels.

Data channel

Data channels are used to transfer reverse data packets.

ACK sub-channel

ACK channels are used by AT and AN to confirm the delivery of data packets in forward traffic channels. NAK bits will be sent if demodulation failed.

The forward channels and reverse channels have the same time slot structure

The data packing duration of reverse links is 26.67ms;

Each packet takes up a 26.67ms frame;

Time-slot structure of

Channels

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Each frame contains 16 1.67ms time slots;

Each time slot contains 2,048 PN code snippets;

Transfer starts from any time-slot in the 16 time-slots to randomize the transfer in reverse links.

1. Reverse access channel

The reverse access channel encoding is shown in FIGURE 7.

FIGURE 7 1 X EV-DO R E V E R S E AC C E S S C H AN N E L E N C O D I N G P R O C E S S E S

(I) Pilot channel

The data in pilot channels are all zero. Encoding is not required as the spread spectrum is performed straightforward by W0

16.

Channel Encoding and

Modulation

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12 Confidential and Proprietary Information of ZTE CORPORATION

(II) Data channel

The data rate in data channels is 9.6kbit/s. Each frame contains 256 bits. It is called an access channel packet. This packet is converted into a 38400bit/s signal by performing 1/4 Turbo encoding and then interleaved. The data unit is 1024bit when interleaving. After completing 8 times code element repetitions on the interleaved data, the W2

4 band spread is carried out.

2. Reverse traffic channel

The reverse traffic channel encoding processes is shown in FIGURE 8,FIGURE 9 and FIGURE 10.

FIGURE 8 R E V E R S E T R AF F I C C H AN N E L E N C O D I N G P R O C E S S E S (F I R S T H AL F )

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FIGURE 9 RE V E R S E T R AF F I C C H AN N E L E N C O D I N G P R O C E S S E S (S E C O N D H AL F )

Pilot channels, DRC channels and ACK channels all use Walsh functions (4, 8 or 16 in length) to implement quantrature band spread.

Aiming at different reverse channels, further explanation to the encoding processes is given as follows:

I) Pilot channel

FIGURE 10 TH E TDM AS S I G N M E N T O F P I L O T C H AN N E L AN D RRI C H AN N E L

AT transmits unmodulated symbols. The values in the pilot

channels are 0 (binary).

The transmissions of pilot channel and RRI channels is multiplexed (TDM) on the Walsh W0

16 channel.

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14 Confidential and Proprietary Information of ZTE CORPORATION

The emission power of pilot channel and PRI channel is the same.

II) DRC channel

The forward traffic channel data transfer rate in DRC channel is in line with a 4-bit value which is defined by forward traffic channel MAC protocol.

DRC channel uses 8-level Walsh function to perform band spread.

The data rate of transferring DRC value is 600/DRCLength per second. The DRCLength is the public data in forward traffic channel MAC protocol.

III) RRI channel

The signal transmitted by AT is presented by a 3-bit RRI symbol (Physical Layer pack a 3-bit symbol every 16 time-slots)

Each RRI symbol is converted into a 7-bit code word by a single encoder. After this conversion, each code word repeat 37 times and the last 3 symbols will be omitted. The acquired 256 binary symbols of each Physical Layer packet and the pilot channels symbols are multiplexed (TDM). This is the same as the period of the corresponding Physical Layer packet.

T ABLE 4 RRI S Y M B O L AN D S I N G L E E N C O D E R AS S I G N M E N T

Data rate(kbit/s) RRI symbol RRI code word

0 000 0000000

9.6 001 1010101

19.2 010 0110011

38.4 011 1100110

76.8 100 0001111

153.6 101 1011010

Reserved 110 0111100

Reserved 111 1101001

The TDM pilot and RRI channel sequence use W016 to fulfill

band spread. It generates 256 RRI code snippets every time-slot.

AT will transfer RRI code words on RRI channels at 0 data rate when Physical Layer packets are not transferred on reverse channels.

The pilot channels and RRI channels perform transfer on I channels.

IV) ACK channel

Each forward traffic channels time-slot is relative to the detected leading codes sent to AT. AT will generate an ACK

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channel bit as the acknowledgement to each forward traffic channels time-slot. Otherwise, the ACK channels are closed.

ACK channels will generate a “0” bit if a forward traffic channels physical layer packet is received successfully. Otherwise a “1” bit (NAK) will be generated.

The time-slots in the head half of W48 channel are used when

transferring ACK channels bits.

BIT/SK is used to the ACK channels modulation.

V) Data channel

AT is able to transfer data at 9.6kbit/s, 19.2k/bits, 38.4kbit/s. 76.8kbit/s and 153.6kbit/s on the data channels of reverse traffic channels. The data transfer rates comply with the MAC protocol in reverse traffic channels.

The packed length is fixed 26.67ms in order to achieve better time diversity.

Turbo decoding uses concurrent connections codes (code rate = 1/2 or 1/4). The performance is closed to the capacity.

Reverse channels interleaving and repetition are implemented to take the advantages of time diversity.

Data transfer only starts from a particular time-slot to randomize user signals.

Frame Offset is the common data in reverse traffic channels. All the data transferred on reverse traffic channels are encoded, code-block interleaved, sequences repeated and as well as to use W2

4 function to realize quandrature band spread.

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C h a p t e r 2

Keys Technology in 1x EV-DO

Key points Adaptive Modulation 1xEV-DO Coding Rate Reverse Rate Control Fast Cell Site Selection

Introduction

In this section, some key technologies in 1x EV-DO are introduced.

Power control is essential to the system maximization. The forward power control is not required in 1x EV-DO because of its constant power. Therefore, power control is mainly adopted by reverse channels.

The purpose of power control in reverse channels is to minimize the interference as well as control the AT’s output power in order to ensure the best performance of reverse data links. When the average reverse links SNR of each user reaches the minimum value that is acceptable for maintaining the operation, the maximum capacity is obtained.

1. Opened-loop power control

The assessments of 1x EV-DO opened-loop power include the assessment of access channels (pilot channels and data channels) and reverse traffic channels.

AT sends a random heuristic accessing sequence to AN before the establishment of reverse traffic channels. The original emission power of pilot channels is defined by the following formulas:

mean pilot channel output power (dBm)=

-Mean Received Power (dBm)

+OpenLoopAdjust

Reverse link power control

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+ProbeInitialAdjust

OpenLoopAdjust and ProbeInitialAdjust are public variables of access channels. They are defined in Access Parameter Message. For Band Classes 0, 2, 3, 5 and 7, OpenLoopAdjust+ProbeInitialAdjust is in a range of -81~-66dB; For Band Classes 1, 4, and 6, its range is from -100dB to -69dB.

Each heuristic accessing emission power is increasing in the first accessing heuristic sequence. During the number i heuristic accessing, the emission power of pilot channels in the access channels can be formulated as follows:

mean pilot channel output power (dBm)=

-Mean Received Power (dBm)

+OpenLoopAdjust

+ProbeInitialAdjust

+(i-1)×PowerStep

In access channels, the power of data channels is relative to the power of pilot channels. It can be formulated as follows:

mean data channel output power(dBm)=

- Mean Received Power (dBm)

+ OpenLoopAdjust

+ ProbeInitialAdjust

+(i-1)×PowerStep

+ DataOffsetNom

+ DataOffset9k6

+3.76

PowerStep, DataOffsetNom and DataOffset9k6 are common variables in access channel MAC protocol. They are defined in the power parameters of access channel MAC protocol configuration messages.

A heuristic accessing includes a prefix and one or more Physical Layer packets. It only contains a pilot channel while the data segment contains a pilot channel and a data channel. In order to reach equalization, the pilot channel power of the prefix segment must be higher than the pilot channel power of the data segment. Their difference equals to the output power of data channel.

According to this, in access channels, the opened-loop output power in pilot channel is mean pilot channel output power; the opened-loop output power in data channel is mean pilot channel output power + mean data channel output power,

See FIGURE 11.

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FIGURE 11 TH E H E U R I S T I C AC C E S S

Fig.错误!文档中没有指定样式的文字。-1

Once the indication of reverse traffic channel MAC protocol is received, AT will initialize the transmission of reverse traffic channels. In reverse traffic channels, the reverse rate indication channel and the pilot channel are multiplexed (TDM). They are still called pilot channel and Transmit at the same power.

AT transfers pilot channel, DRC channel, ACK channel and data channel when the reverse traffic channels are transferred. These channels must be transferred at a particular power level. The level depends on the opened-loop power control and closed-loop control.

In the reverse traffic channels, the pilot channel original output power can be formulated as follows:

Mean pilot channel output power (reverse traffic channel) =

Mean pilot channel output power (access channel)

- Mean Received Power 1

+ Mean Received Power 2

The “Mean pilot channel output power” on the left is the original emission power of pilot channel while the one on the right is the last heuristic accessing pilot channel emission power in access channels. Mean Received Power 1 is the forward link receiving power at the last heuristic access; Mean Received Power 2 is the forward link receiving power when the transfer of reverse traffic channel begins.

Refer to the cdma2000 protocol, the pilot channel original output power can be formulated as follows:

mean pilot channel output power(dBm)=

-Mean Received Power(dBm)

+OpenLoopAdjust

+ProbeInitialAdjust

+(N-1)×PowerStep

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Here the Mean Received Power is the current forward links receiving power. N is the number of heuristic accessing times that before successful access.

The emission power of DRC channels, ACK channels and data channels are determined by relative pilot channel power gain.

Mean DRC channel output power(dBm)=

+mean pilot channel output power(dBm)

+DRCChannelGain

Mean ACK channel output power(dBm)=

+mean pilot channel output power(dBm)

+ACKChannelGain

The DRCChannelGain and ACKChannelGain are defined in the Traffic Channel Assignment Message.

mean Data channel output power(dBm)=

+mean pilot channel output power(dBm)

+Data channel gain

Data channel gain

The data channel gain varies according to the variation of data rates.

T ABLE 5 TH E D AT A C H AN N E L G AI N V AR I E S AC C O R D I N G T O T H E V AR I AT I O N O F D AT A R AT E S

Data rate(kbps)

Data rates

Corresponding to the Pilot channel,data channel gain(dB)

Data channel gain (corresponding to the pilot channel)

0 -∞ (data channel not transferred)

9.6 DataOffsetNom + DataOffset9k6 + 3.75

19.2 DataOffsetNom + DataOffset19k2 + 6.75

38.4 DataOffsetNom + DataOffset38k4 + 9.75

76.8 DataOffsetNom + DataOffset76k8 + 13.25

153.6 DataOffsetNom + DataOffset153k6 + 18.5

The parameters listed in the table are configured in the reverse traffic channel MAC protocol.

2. Closed-loop power control

Once the connection established, according to the measured signal quality of reverse links, AN continuously sends “0” (ascending power) or “1” (descending power) PRC bits to AT. If the signal quality is greater than the SetPoint, a “1” bit will be sent. On the contrary, a “0” bit will be sent.

Based on the successful receiving of the reverse power controlling bits, AT will adjust its output power according to the direction indicated by power controlling bits and the step length indicated by RCStep. If AT doesn’t transfer the

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reverse traffic channel at time-slot n, the power controlling bits will be neglected at time-slot n+1.

The data rate in reverse power control channel is 600bit/s. That means the PRC symbols are transferred four times every time-slot and every PRC symbol is corresponding to 64 code snippets. Based upon the receiving of the 64 code snippets of MAC channel after the second pilot of the first time-slot, the power controlling bits are received.

AT provides different PRC channels with diversity combination when it is at a soft-switch status. What’s more, AT must acquire at most 1 power controlling bit from each PRC channel. The output power will be raised by AT if all the PRC bits are ‘0’. However, AT will reduce the output power according to the PRCStep length.

AT modifies pilot channel emission power in terms of power controlling bits. This enables AT figure out the emission power of DRC, ACK and data channels in accordance with the relative pilot channel power gain.

Similar to the IS95/1x, reverse closed-loop power control is comprised of inner-loop control and outer-loop control. Inner-loop control keeps the received pilot signal-noise ratio at the Power Control Threshold (PCT) level. Outer-loop control dynamically adjusts the PCT in order to keep PER at a particular level (1% in most cases) under any channel condition.

PCT is used to the outer-loop power control. It is figured out by the outer-loop power control algorism. Each PCT frame and reverse links’ frames change at the same rate. The change of PCT is the function of the reverse links frame qualities and the status of the reverse opened-loop power control algorism. If a reverse traffic frame passes the CRC, it is considered a good frame, or it is a bad one.

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FIGURE 12 P O W E R C O N T R O L T H R E S H O L D C H AN G E S W I T H T I M E

The letters on the Time axis stand for the status of the reverse traffic

channels at a particular time. (G stands for ‘Good Frame’, B stands for ‘Bad

Frame’, N stands for ‘No frame received”

错误!未找到引用源。 demonstrates a typical PCT change. The PCL status depends on the existence or nonexistence of reverse traffic channel data.

In 1x EV-DO specifications, AT’s reverse rate can be freely adjusted by AT from 9.6kbit/s to 153.6kbits. In order to avoid all the AT become unavailable, the workload of reverse links must be constrained to prevent too many users in the same sector from transferring data to AN at a high rate.

AN uses two mechanisms to constrain the AT emission power:

1. Reverse Rate Limit. AN can constrain AT’s rate at a particular level which has the highest reverse rate at 153.6kbit/s.

2. RAB and Transition probability. RAB is set ‘0’ when the sector detects that the reverse links are underloaded. The AT in this sector can raise their reverse rate according to a set of predefined probability values (Transition009k6_019k2 ,

Transition019k2_038k4 , Transition038k4_076k8 ,

Transition076k8_153k6). RAB is set ‘1’ when the sector detects that the reverse links are overloaded. In this situation, all the AT must reduce their transfer rates according to a set of predefined probability values. If the AT is at soft switch status and the RAB in any sector is ‘1’, the AT’s rate will be going down.

The key issue in reverse links rate control is how to measure the busy-idle status of reverse links. Measuring the Rise Over Thermal (ROT) at each sector antenna is a relative precise method.

Reverse link rate control

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The forward link of 1x EV-DO is different form 1x. It uses TDM to serve all AT. In a sector, only one user is served at a particular time-slot.

Like IS-95/1x, the forward pilot channel helps AT fulfill system acquisition and channel assessment of modulation and demodulation.

In 1x EV-DO, AT chooses the service sector and determines the highest rate it can support. All of these are done by the measurement of forward pilot quality and the wireless channels quality assessment of the environment where AT is in. All the BTS transfers pilot simultaneously at full power. Therefore, AT can figure out precise pilot intensity to promptly respond to each BTS signal and interference.

In order to provide users with the highest transfer rate, AT requests the most suitable data rate according to the C/I value of AN.AN uses the scheduling algorism to assign different users with corresponding services according to the requests from AT.

The purpose of the scheduling strategy is to maximize the system throughput as well as ensure the fairness among the users. Due to the complexity of radio environment, AT informs AN of the highest data rate that it can accept through the DRC channel. The system informs the maximum DRC value in order to reach the maximum throughput. In this case, other users are not served by the system. Therefore, the purpose of the scheduling algorism is to balance the throughput and the fairness.

1x EV-DO uses ratio-fair algorism. It not only ensures the fairness to the users buy also as many as possible expand the system capacity.

The following section gives some details of this algorism.

For each user k, scheduler has a corresponding variable Tk. This variable updates every time-slot. The variable index is the time-slot n. therefore Tk[n] represents the scheduler value of user k at time-slot n. there are two steps with this algorism:

1. Scheduling——at each time-slot n, DRC1[n], DRC2[n], …are known,among the DRC users who need to transfer data, choose those who has the maximum DRCk[n]/Tk[n].

2. Renewal——at each time-slot, the scheduler variable Tk of each user is renewed by the following formula. Tk is related to the actual data acquisition at a particular period.

Here, tc stands for time. If at time-slot n, the part of the first time-slot of a packet (length = Ik[n] time-slots, rate = Nk[n], early termination of multi-slot packet is not considered here)

Forward link TDM

Scheduling strategy in

forward link

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is sent to user k, then the Sk[n]=Ik[n]*Nk[n]; for any other user or time-slot, the Sk[n]=0.

Based on the two steps above, the system is able to maintain the Tk and ensure the fairness among the users.

For example, the system will raise Tk to show more fairness. It can be observed that the system transfers data by choosing the maximum DRCk[n]/Tk[n] at the first step. Even the user k now has the maximum DRCk[n], it doesn’t mean it can subscribe to the data service without Tk[n].

If was served before, Tk[n] will be greater. The DRCk[n]/Tk[n] won’t be the maximum in the system when Tk[n] is great enough. Under this circumstance, the user k won’t be served at the next time-slot.

Due to the bad radio environment, some users are not served all along. They report the less DRCValue. Tx[n] is much less. Therefore, the DRCx[n]/Tx[n] is greater than the user k. The user k will be served at the next time-slot. This mechanism ensures the fairness.

Same as 1x, the 1x EV-DO handoff control supports various soft/hard handoff. In addition, a new mode called forward Virtual Handoff is introduced into 1x EV-DO.

In The forward Virtual Handoff, there’s only one sector sends data to the terminals at a particular time in the AT active set. According to the quality of each received pilot, AT can use the DRC Cover to specify the sectors which are expected to transfer data. In AN, all the sectors within the active set are listening to the reverse channels of the AT. AN decides which sector is the Serving Sector of the AT according to the DRC channel received.

There’s no signaling messages exchange between AN and AT in the forward Virtual Handoff, as it is very quick. It only takes up one sector’s forward air resource at anytime. The usability of forward channels is improved significantly.

AT can request 9 different data rates according to the transfer quality of forward RF links. The lowest rate is 38.4 kbit/s and the highest rate is 2457.6 kbit/s. The combination of higher order modulation/demodulation and error correction enables such high data transfer rate on the 1.25MHz carrier wave.

In 1x EV-DO, the IMSI/MIN is not required to be allocated in advance when routing. For R-P session, the switch between BSC and PDSN needs other solutions. AT and IMSI should be identical to ensure the successful sessions between BSCs within a PDSN.

An IMSI is allocated to AT when a session is initiated by BSC between AT and PDSN. A new interface called A12 was introduced into the 1x EV-DO specification. It is the interface between BSC and AN-AAA server.

AN-AAA has two functions:

1. AT authentication

Virtual soft handoff in

forward link

Adaptive Modulation

and Encoding

R-P Session Establishment

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2. An IMSI is returned to BSC from its authentication message center. The IMSI is used to the establishment of BSC and PDSN.

If the AN-AAA server is not deployed in 1x EV-DO, BSC has to allocate IMSI to AT by using other dedicated methods. The IMSI must be unique in the network. The R-P session between 1x EV-DO BSC and 1x BSC can not be completed without AN-AAA server. Depends on mobile IP, AT can remain its IP address unchanged when crossing the network borders. The deployment of AN-AAA facilitates the prompt switch and improve the AT performance when crossing the network borders.

Service Flow

The 1x EV-DO service involves session management service and connection management service. This section describes their service flows.

A session between AT and AN must be established before the AT be served in 1x EV-DO system. The session management includes UATI allocation and maintenance, session negotiation and session release.

1. UATI Assignment and Maintenance

The Unicast Access Terminal Identifier (UATI) is the unique identifier allocated by AN. Its length is 128bit. The UATI allocation is the first step of a session establishment. It means a session which uses the default configuration is initiated. The UATI assignment flow can be demonstrated FIGURE 13.

FIGURE 13 U ATI AS S I G N M E N T

AT

A

B

C

D

AN

E

UATIRequest

ACAck

UATIAssignment

UATIComplete

ACAck

The UATI allocation flow is descript in detail as follows:

A. AT sends a UATIRequest message to AN via access channels;

B. AN responds an ACAck message;

Session Management

Flow

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C. AN assigns and sends the UATI to AT by UATIAssignment message;

D. AT responds AN by UATICompetele message. UATI assignment completes;

E. AN responds a ACAck message. AT and AN can initiate UATI update during the session.

2. Session Negotiation

During the session establishment between AT and AN, there will be some negotiations about the system configurations (protocols and the parameters in the protocols) between both sides. A session can be established successfully once the negotiation reaches an agreement. The negotiated configurations will take effect at the reconnection. The negotiation procedures are shown in the FIGURE 14 :

FIGURE 14 S E S S I O N N E G O T I AT I O N F L O W

AT

A

B

C

D

AN

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

Connection Establishment

Key exchange

ConfigurationRequest

ConfigurationResponse

ConfigurationRequest

ConfigurationResponse

ConfigurationRequest

ConfigurationResponse

Type X ConfigurationRequeste

Type X ConfigurationResponse

Type Y ConfigurationRequeste

Type Y ConfigurationResponse

ConfigurationComplete

ConfigurationRequest

ConfigurationResponse

Type X ConfigurationRequest

Type X ConfigurationResponse

ConfigurationComplete

The UATI session negotiation flow is described are as follows:

A. AT and AN open a connection in default configuration to prepare for the session negotiation.

B-G. AT initiates the protocol negotiation.

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H-K.AT initiates protocol configuration (Type X and Type Y represents the protocols that the negotiation parameters belong to).

L. The negotiation initiated by AT completes.

M. Key exchange is used by the system to authenticate the AT during the session.

N-Q.AN side initiates negotiation.

R. The negotiation completes.

3. Session Release.

AT is not likely to establish or release sessions frequently in the 1x EV-DO system. After the session establishment, AT can open and close the connections many times during the session. Some reasons such as KeepAlive timeout or subscriber’s request will cause the session release.

The session release is a simple process. Both sides exchange a SessionClose message and release the corresponding resources and end the process. It must be noticed that the PPP Session established by AT and PDSN needs to be released as well when releasing the 1x EV-DO session.

In the 1x EV-DO, a connection is opened between AT and AN. It means AT is assigned reverse power control channel and reverse traffic channel; the Forward Traffic Channel (FTC is TDM shared by all the users who has opened the connection) is available to AT. AT can use the high speed packet service provided by 1x EV-DO as long as the connection established.

1. AT originates Calls and Establishes Connection

During a session, AT and AN can open and close the connection many times. The connection establishment can be initiated by either AT or AN.

The connection initiated by AN supports common mode and fast mode. In common mode, AN sends a paging message out, once it is received, AT responds as a ConnectRequest message to enter the connect establishment procedures; In fast mode, AN sends a channel assignment message out (the Page/ConnectRequest interaction is neglected) to speedup the connection establishment.

AN AAA will fulfill an access authentication on every AT before the first trying to connect to the PDSN. Only those AT who passes the authentication can continue initializing the connections to the PDSN. Based on the successful authentication, AN AAA returns an IMSI number to AT. AT uses this number as the identifier on the A10/A11 links to communicate with PDSN.

If a session between AT and AN has been established before the connection establishment, the connection establishment procedures initiated by AT is demonstrated in FIGURE 15.

Connection Management

Flow

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FIGURE 15 C O N N E C T I O N E S T AB L I S H M E N T F L O W I N I T I AT E D B Y AT

AT PDSN

AB

CD

AN PCFAN_AAA

EF

G

H

I

JKL

MNO

P

Q

R

S

ConnectionRequest +RouteUpdate

ACAckTrafficChannelAssignment

Pilot + DRCRTCAck

TrafficChannelComplete

AT or AN indicatesready to exchange data

on access stream

PPP and LCPnegotiation

CHAP challenge andresponse

CHAP Authenticationsuccess

AT ready to exchangedata on service stream

A12AccessRequestA12AccessAccept

A9SetupA8

A9ConnectA8

A11RegistrationRequestA11RegistrationReply

Establishing PPP connections

Transmitting packet Data

The connection establishment flow initiated by AT is introduced in detail as follows:

A. In access channel, AT sends out a ConnectRequest and a RouteUpdate message to request the connection establishment;

B. In control channel, AN receives the messages sends back an ACAck message;

C. AN sends out the TrafficChannelAssignment message which includes the MAC_ID assigned to AT and other related information;

D. AT sends out the Pilot and DRC message based upon the receiving of TrafficChannelAssignment message from AN;

E. AN acquires the Pilot and DRC from AT and then send a RTCAck message to AT in FTC channel;

F. In RTC channel, AT sends back a TrafficChannelComplete message to indicate that the air-connection is established;

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G. AT informs AN that the data exchange in access flow is available;

H. AT and AN initiate the PPP connection and the LCP negotiation which will be used in access authentication;

I. AN sends a CHAP message to AT to initiate a random query. AT sends back a CHAP response message as the response;

J. AN collects the authentication messages (Username, CHAP-ID, CHAP-Challenge, CHAP-Response) about the AT and send them to the AN AAA through A12 interface;

K. AN AAA sends back an AccessAccept message once authentication is done successfully;

L. AN sends back the information about successful authentication to AT;

M. AT initiates the connection to the PDSN;

N-Q. The connection towards PDSN initiated by AN via PCF is established;

R. AT tries to connect to the PDSN with PPP connection;

S. The data packet exchange between AT and PDSN becomes available after the establishment of PPP connection.

2. AT Originates Calls and Closes Connections

There are many reasons that will cause the connection release such as the timeout of idle timer or AN overload control. The connection release processes initiated by AN is shown in 错误!未找到引用源。.

FIGURE 16 TH E C O N N E C T I O N R E L E AS E P R O C E S S E S I N I T I AT E D B Y AN

AT PDSN

A

B

C

AN PCFAN_AAA

D

E

ConnectionClose

A9-Release-A8

A9-Release-A8 Complete

A11-Registration-Request

A11-Registration-Reply

The connection release processes initiated by AN is introduced in detail as below:

A. AT sends out a ConnectClose message in the access channel to request the connection close;

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B. AN sends an A9-Release-A8 (value cause is ‘the packet service begins to hibernate’) to PCF and request the A8 connection release;

C. PCF sends an activated stop accounting record to PDSN through an A11-Registration-Request message;

D. PDSN returns an A11-Registration-Reply;

E. PCF uses an A9-Release-A8 Complete message to confirm the release of A8 connection. The release completes.

In the above figure, only the air-link and A8 link is released; the connection between AT and PDSN as well as the 1x EV-DO session between AT and AN are still activate.

3. Switchover Control

In the commercial environment, generally, 1x EV-DO and cdma2000 1x coexist in one network to provide users with voice and high speed data service. The dual mode (1x and 1x EV-DO) handsets can easily switchover between two AN. In this switchover, the PPP connection between AT and PDSN won’t be interrupted. Furthermore, in order to ensure the priority of voice service, when an AT is transferring data on the 1x EV-DO network, it must be timely switched to 1x network listening paging channel. When the voice paging from AN is received, the dual mode AT immediately stops the data transfer on the 1x EV-DO network and begin to establish a voice connection on the 1x network.

The following situations may occur when the dual mode AT switches cross network.

Switch from 1x to 1x EV-DO when dormant;

Switch from 1x EV-DO to 1x when dormant;

Switch from 1x to 1x EV-DO when active;

Switch from 1x EV-DO to 1x when active;

Receive the 1x voice calls when the 1x EV-DO data are active.

If AT has already established the 1x EV-DO session on the 1x EV-DO network and the 1x EV-DO and 1x are sharing one PDSN, 1x can provide concurrent service.

At a dormant status, the switching procedures of AT from 1x to 1x EV-DO are briefly introduced:

A. When AT accesses 1x EV-DO from 1x, it launches a position renewal procedure to enable 1x EV-DO acquire the PANID of AT;

B. The destination AN initiates a request of establishing a connection towards PDSN;

C. PDSN stops the connection with source AN when the request is received and then connect to the destination AN.

In this processes, the PPP connection between the dual mode AT and PDSN doest not interrupt.

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The 1x voice paging receiving processes during the 1x EV-DO data activation period is briefly introduced as follows:

A. At the source AN, AT turns to dormant from active;

B. At dormant status, AT performs the cross network switch;

C. At the destination AN, AT turns to active from dormant.

When the dual mode AT transfers data on the 1x EV-DO, in order not to neglect any voice call from 1x, it must switch to the 1x timely to listen to the time-slots that are assigned to the handset. Once the voice paging message is received, the dual mode will switch to the 1x according to the voice priorities to answer the voice calls. The data sessions on 1x EV-DO can be switched to 1x if the concurrent service is supported on the target 1x. This makes the concurrency of voice calls and data packet transfer available.

Comparisons with 1x

The core differences between 1x EV-DO and 1x are shown in TABLE 6.

T ABLE 6 C O R E D I F F E R E N C E S B E T W E E N 1X EV-DO AN D 1 X

Feature 1x 1x EV-DO

Service Voice/Data Data

Highest rate Forward: 153.6 kbit/s (RC3)

Reverse: 9.6 kbit/s (RC3)

Forward: 2.4 Mbit/s

Reverse: 153.6 kbit/s

Core network ANSI-41 based Real IP

Channel multiplexing CDM (Forward/Reverse) Forward: CDM+TDM

Reverse: CDM

Switch Hard handoff and soft

handoff (Forward/Reverse)

Forward: VHO Reverse:Soft handoff

Power control and rate

control

Fast power control

(Forward/Reverse);

Rate control is not available

Reverse: Rate control +

Power control

Forward: rate control

Access procedures Access channel procedures

Enhanced access channel

procedures

Same as access channel

procedures

RF and encoding Convolution code and Turbo

code

48-level FIR filterer

Turbo code only

48-level FIR filterer

Compared with 1x, 1x EV-DO has the following advantages in high speed data packet services:

1. Air interface: 1x EV-DO eliminates the transfer bottleneck of data service at air interfaces.

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2. RF parameters: 1x EV-DO fully takes the downward compatibilities into account.

3. Technologies: 1x EV-DO and 1x have the same power control, soft handoff, access procedures and Turbo encoding technologies. The developers can easily develop the 1x EV-DO products by taking the advantages of existing 1x technologies.

4. Networking:1x EV-DO is very flexible. For the users needing only data packet services, an independent 1x EV-DO network with minimum configuration can provide high speed data packet services. In this case, the sophisticated ANSI-41 structure is not required for the core network configuration because it is IP network based. For those users who need both voice and data services, the combination of 1x and 1x EV-DO is also available. What’s more, for the dual mode (1x/1x EV-DO) AT, 1x EV-DO provides a mechanism to make the switchover between the two systems available.

Review

1. Briefly state the functions of 1x EV-DO forward channels.

2. Briefly state the principles of rate control in 1x EV-DO reverse links.

3. Briefly state the principles of power control in 1x EV-DO reverse links.

4. Briefly state the principles of scheduling strategy in 1x EV-DO forward links.

5. Briefly state the principles of the call originating procedures in 1x EV-DO AT.

6. Compare 1x EV-DO and 1x.