Introduction to Wireless Technology

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Introduction

To

Wireless CommunicationEngineering

17082011

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Content

Introduction To Wireless Communication

Evolution of Wireless Technology

Multiple Access Technologies Mobile Access Architecture & Design

Fundamentals

Mobility Management Standardization of Wireless Access

Technologies

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Multiple Access Technologies Mobile Access Architecture & Design

Fundamentals

Mobility Management Standardization of Wireless Access

Technologies



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Objective

At the end of this topic, you will:

Understand the motivation behind wireless

communication.

Know the applications of wireless technologies

in mobile communication.

know some terminologies used in wirelesscommunication.

Know the characteristics of RF

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Introduction to Wireless Communication

Motivation

Before the era of wireless communication, telephony

systems basically used cables for interconnection.

This system had the major constraints of mobility.

Hence, wireless communication was developed to

enabled mobility.



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Introduction To Wireless Technology

The application of wireless technology in

telecommunication can be classified into two

namely:

Access Level

Transmission Level



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Introduction To Wireless Technology-Contd

Access Level

Also referred to as Radio Access Network or Wireless Access

Network.

Allows mobile users gain access to a networks services.

Users need to share system resources and are awarded accessto the network based on pre-defined rules.

Multiple access technologies are adopted to permit multiple

users access the network. E.g CDMA, TDMA, FDMA, OFDMA

etc.

Adopts the use of sectorial or Omni-directional antenna

Coverage and Capacity are 2 major constraints of wireless

access technologies



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Some Wireless Access Terminologies

Cell- A cell is the geographical area

covered by a BTS signal.

Sector- A sector is a section of a cell. Itdefines the geographical area covered by

one of the BTS antenna

RF Short for radio frequency, any

frequency within the electromagneticspectrum associated with radio wave

propagation



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Some Wireless Access Terminologies When an RF current is supplied to an

antenna, an electromagnetic field is

created that then is able to propagate

through space.

Antenna- An antenna is an electrical

device which converts electric

current into radio waves, and radiowaves into electric currents



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Introduction To Wireless Technology-ContdSome Facts About RF

A radio tone has a frequency, and a radio signal carrying

information has a range of frequency content. Modulation at the transmitter, based on and coupled

with a given multiple-access mechanism, allows wireless

communication over particular frequency bands.

These bands are designated by local regulatory

authorities e.g NCC, and generally coordinated byregional and global (International Telecommunication

Union) bodies.

They may be licensed (e.g., bands

used by service providers in generations of mobile

cellular technologies), or unlicensed (e.g., bands used byWLAN and Bluetooth, among others).

Frequency is inversely proportional to wavelength.



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Transmission Level The second level of application of wireless technology in

telecommunication is at the transmission level.

Transmits mobile user data/voice between network nodes,

usually between the BTS and BSC. The transmission equipments include satellite, microwave

radios/antenna etc.

Operates in higher frequency spectrum of 4GHz to 300GHz.



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Multiple Access Technologies

Mobile Access Architecture & Design

Fundamentals

Mobility Management

Standardization of Wireless Access

Technologies


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Objective

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After this course, you will:

Understand the various stages of evolution

in mobile communication.

Know the major differences amongst the

different generations.


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Evolution of Wireless Technologies



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Evolution of Wireless Technologies-Contd

Till now, wireless communication

has undergone four stages in itsdevelopment, namely:

Analogue to digital

simple communication

high-speed downloading

high-speed downloading and

uploading

A fifth stage, seamless fixed-mobile

convergence, is about to enterservice.



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First Generation

This generation of wirelesscommunication enabled voice

services only. Voice was transmitted

in its analogue form. AMPS, TACS

and NMT fall in this generation.

Second Generation

This generation introduced digital

communication.i.e there was a

transition from analogue to digital

communication.

simple data service were introduced

alongside voice service. GSM,CDMA

IS 95, GPRS



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Third Generation

This generation improved thedata download and upload speed

by improving the spectral

efficiency. Also, voice services

were improved upon. EVDO Rel0,

WCDMA

4th Generation

By further improving the spectral

efficiency, access mechanism and

antenna technology, data rates

were improved upon. EVDO Rev

B, HSPA+



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Evolution of Wireless Technologies -Contd

Third Generation

This generation improved thedata download and upload speed

by improving the spectral

efficiency. Also, voice services

were improved upon. EVDO Rel0,

WCDMA

4th Generation

By further improving the spectral

efficiency, access mechanism and

antenna technology, data rates

were improved upon. EVDO Rev

B, HSPA+



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Fundamentals

Mobility Management


Technologies


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Objectives

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After this chapter, you will be able to:

Understand the various multiple access

technologies.

The application of the different multiple

access technologies.

The difference between the access

technologies


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Multiple Access Mechanisms is the

technology used to allow multiple users

access a wireless communication

network.

FDMA (Frequency Division Multiple Access)

A spectrum sharing/ multiple access

scheme that allows the whole frequency

band be divided into adjacent frequency

segments, while each segment is

allocated to a single user.

It is used in analog systems. It is not an efficient multiple access

mechanism.

Used in AMPS, TACS(1st generation)Powered By

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Multiple Access Technologies -Contd

TDMA (Time Division Multiple Access)

This allows multiple users to access the samefrequency channel, by dividing the channels

into timeslots and allocating them to different

users

It is used in digital systems. It is a more efficient multiple access mechanism

than FDMA.

It is limited by the number of slots that can be

allocated. Simple handoff and less stringent power control

mechanism.

Used in GSM, IS-136, EDGE, GPRS etc.

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CDMA (Code Division Multiple Access)

In this system, all users of a network access thenetwork using the same frequency, time and

space.

Unique codes are assigned to each user of the

network. These codes help in distinguishing each user on

the network.

Codes are orthogonal in nature.

Employs a form of spread spectrum

The signal-to-noise power ratio decreases as

the number of users increases.

Used in CDMA 2000.Powered By

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OFDMA (Orthogonal Frequency Division Multiple Access)

In OFDMA, the frequency bandwidth is divided intoorthogonal frequency subcarriers.

Each subcarrier is divided into channels

Each channel is allocated to each user.

It deploys CP (cyclic prefix) to prevent Inter SymbolInterference (ISI)

Users are associated channels according to channel

condition feedback information.

Greater spectral efficiency than CDMA. Used in WiMAX technology.



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Fundamentals

Mobility Management


Technologies


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Objectives

This chapter will help you:

Acquire the knowledge of a mobiles network

architecture.

Understand how each node on the network

relate.

Understand some fundamental factors

considered in wireless communication

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Mobile Access Architecture & Design Fundamentals

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MS: Mobile Station BTS: Base Transceiver StationBSC: Base Station Controller MSC: Mobile Switching Center

HLR :Home Location Register VLR: Visitor Location Register

PCF: Packet data Control Function PDSN: Packet Data Service Node

HA: Home Agent FA: Foreign Agent

SCP: Service Control Point Radius: Remote Authentication Dial-in User Service

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-Contd The user terminal/MS is wirelessly connected to a Base Transceiver

Station (BTS). The interface between BTS and MS is called Um

interface

This base station and a number of others are connected to a Base

Station Controller (BSC).

The BSC connects to an MSC for voice services using circuit

switching technologies. The BSC connects to the IP gateway for data services using packet

switching technologies.

The MSC connects to other core network equiments and other

PLMN and PSTN.

The IP gateway equipment connects to the internet.

Quality of the wireless access connectivity is measured by call drop

rate, access failure, block probability, packet loss rate and/or

network reliability. Powered ByAll rights reserved



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-ContdCapacity & Coverage

In wireless technology, coverage and capacity are 2 crucial

interelated factors.

Coverage is defined as the geographical area that can support

continuous wireless access connectivity with the minimum

guaranteed Quality of Service.

It is heavily impacted by terrain, RF environment, and

interference.

It is determined by the operating frequency, cell planning,

radio receiver sensitivity, and required signal-to-noise ratio

that an access technology can support.




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-ContdCapacity & Coverage

Capacity is defined as the maximum number of users or the

total data throughput a network can support reliably.

It relies on traffic loading, traffic patterns, cell site equipment

capability, and hardware dimensioning. There is a great deal of relationship between coverage and

capacity.



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Spectrum Consideration

The frequency spectrum is used for a variety of services,

determined by propagation characteristics, and allocated to

users according to the rules of the local spectrum regulatory

authority. E.g NCC in Nigeria.

The allocation/licensing of frequency spectrum helps in

reducing interference amongst telecoms operators, amongst

other purpose.

When considering spectrum usage and allocation, certain facts

are important. They are

Frequency less than 4Ghz are best for non-line of sight

applications e.g mobile communication, radio stations whilefrequencies above have proven suitable for LOS applications

e.g microwave radio, VSAT etc.



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Spectrum Consideration Contd

Use higher frequencies where propagation is limited and large

bandwidth needed. And use lower frequencies where

coverage is more important than capacity.

Lower frequencies e.g, below 450 MHz have high penetration

properties, providing better indoor coverage.

To meet growing capacity requirements (e.g., for mobile

applications) sufficient frequency spectrum is needed.

Uplink and downlink communication paths need to be divided

(duplexed), either in frequency (FDD) or in time (TDD).



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Fundamentals

Mobility Management


Technologies


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Objective

After this chapter, you will be equiped with the

knowledge of: The motivation behind mobility management

Various states of a mobile phone.

The various mechanisms that enable wireless

communication

The role of each mechanism.


bili


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Mobility Management

Motivation

The major difference betweenPSTN and Mobile communication

is the ability

of the user to move around.

In the event of locomotion, a mobileuser may leave his serving BTS for

another.

Mobility management helps the

system to know the exact location of

a mobile user.

The HLR and VLR (core network

equipments) are used to track the

location of a mobile phone.

Such technologies as registration,paging,admission control, power

control, handoff help in mobility

management.



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States of A mobile Phone



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Registration

Registration is the process used by an MS to

inform the network of its current location,

status, identification and capabilities.

There are 2 types of registration:

Autonomous

Non-autonomous



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Registration -Contd

Autonomous

Registration is triggered by an event or occurence. E.g

Mobile power up and power down.

Timer-based- triggered by the expiration of a system timer. Distance-based- When the distance between the BTS where

the mobile last registered and its current location exceeds a

threshold.

Zone-based- when the mobile enters a zone predefined by thenetwork. e.g home zone



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Registration -Contd

Non-autonomous

Registration is requested by the BTS based on other messages

sent to the mobile. E.g

Parameter change-when a specific parameter changes e.gfrequency

Implicit registration-MS and base station exchange messages

that convey sufficient information to identify the MS and its

location.

Ordered registration-Base station orders a MS to register (e.g.,

while on a traffic channel).



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Paging

This is the system used by the network to alert a MS of an

incoming call or message.

When an MS is in the idle state, it listens to the network for

overhead messages containing network information or pages

indicating that it is being called.

What the MS listens to for this network information is called

paging channel.

The more often a MS registers, the more knowledgible the

network is of its location, and therefore, paging is moretargeted to a smaller group of cells.



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Slotted Mode

In order to maximize battery life, a mobile phone is mostly in

idle state. And to further conserve battery life, slotted mode

or sleep mode is was invented.

In sleep mode, a mobile phone powers down some of its

components and periodically checks for page messagesindicating an incoming call.

The more a mobile phone is in the sleep mode, the better the

battery life. But with this, it will take longer before an MS can

be paged for an incoming call. A sleep period of 2 to 5 seconds is usually assigned.



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Admission Control

The air interface in a wireless system is a shared resource limited by the

number of users that can access it.

If all users get access to the network whenever they needed, without

any control, then it would get to a point when the entry of a new user

would have an adverse effect on the call experience of an existing caller.

E.g In CDMA systems, the more callers on a network, the greater theload in forward and reverse links. Which causes each mobile to increase

power. A mobile user at the edge of the cell, despite increasing power

to maximum, may experience poor call quality.

Admission control adds network intelligence to the call-establishment

process, by ensuring the system has enough resource (both on the

reverse and forward link) to cater for the new caller, such that the call

quality of existing callers is not compromised.



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Admission Control-Contd

Certain factors are checked by the admission control

mechanism. They are:

- Noise rise (in reverse-link systems)

- BTS power (in forward-link CDMA systems)

- Available frequencies or time slots (FDMA or TDMAsystems)

- Codes (for CDMA systems)

- Call-processing resources



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Power Control

Power control is used to achieve high capacity and quality in

wireless systems.

In maximizing call quality, transmission power must be

reduced to the barest minimum so as to maximize system

resources and reduce interference as much as possible. In CDMA system where all caller use the same frequency, it

is important that transmission power is properly managed.

E.g Assuming there is no power control, then all mobile

phones in the network would probably transmit at the samepower, thereby causing call quality issues for mobiles at the

edge of a cell.



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Power Control-Contd

There are 2 types of power control Mechanisms:

Reverse Link

Reverse link open loop

Reverse link fast closed loop

Reverse link outer loop Forward Link

Message transmission mode:

threshold transmission

periodic transmission

Closed loop power control


P C t l C td


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Power Control-Contd

Reverse link open loop

In this system, the MS adjusts its transmit power.

The mobile station adjusts it transmit power based on the

received power level of signals from the BTS.

A strong signal will cause the MS to reduce its transmit power

and vice versa


P C t l C td


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Power Control-Contd

Reverse link Closed loop


The mobile station adjusts it transmit power based on the

instructions received from the BTS.

The BTS measures the transmit power of all mobiles in its

coverage, compares the result with an adjustable threshold and

instructs mobiles to increase or decrease power.

Used to correct the reverse open loop mechanism.


P C t l C td


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Power Control-Contd

Reverse link Outer loop


It is used to set the threshold used by the reverse link closed

loop.

The threshold is set based on the Framer Error Rate (FER)


P C t l C td


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Power Control-Contd

Forward link Power Control

In this system, the BTS adjusts its transmit

power.


Handoff


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Handoff

This is one of the major features that allows for mobility in

wireless systems. It allows communication to be maintained as a caller moves

from one coverage area to another.

Usually, a mobile station listens to signals from minimum of

2 BTS, based on its location and proximity to the BTSs. The BTS with the greater signal strength is the serving BTS,

while the others are standby.


Handoff Contd


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Handoff -Contd

When a mobile is in its idle state, it periodically measure the

signals received from each BTS as it moves around. If asignal becomes stronger than that of the serving BTS, then

the mobile station will change its serving BTS to the new

one.

If a mobile is in its connected state(on a call), it continuallymeasure the signal strength of each BTS. If the signal of a

BTS is stronger than the serving BTS, then the serving BTS

will handover call resources to the new BTS.


Handoff Contd


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Handoff- Cont d

There are three types of handoff:

Soft handoff

Also called Make-Before-Break.

Occurs when a mobile user moves from one BTS coverage to another.

Used in CDMA systems.

Softer handoff Occurs when a mobile user moves from one sector of a BTS to

another.

Used in CDMA systems.

Hard Handoff

Also called hard handover or break-before-make.

Occurs when a mobile user moves from one frequency to another.

Used in GSM systems.Powered By

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Fundamentals

Mobility Management


Technologies


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Objectives

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At the end of this chaper you will:

Understand what standardization is.

Understand the reason for standardization.

Know the various standard bodies.

Have a knowledge of the technologies

supported by each standard bodies.

Standardization of Wireless Access Technology


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Standardization of Wireless Access Technology

Standardization involves the

definition of protocols andessential functions needed for

access, connectivity, throughput

etc in a wireless access system.

It aims to provideinteroperability, inter-working,

and, potentially, a rich set of

attributes and a graceful

evolution path.

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3G system

CDMA2000

3GPP2

FDD mode

WCDMA

3GPPFDD mode

TD-SCDMA

CWTSTDD mode

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3GPP Wireless Access Technology


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3GPP Wireless Access Technology

3GPP means 3rd Generation Partnership Project

Responsible for setting the standards for such technologies asGSM, GPRS, EDGE and WCDMA.

GSM

Global System for Mobile Communication

GSM is a 2G technology

1st phase of GSM was strictly circuit switched, providing voice

and SMS services only.

Uses TDMA for radio transmission, dividing each radio carrier

into 8 timeslots on both uplinks and downlinks.

Each carrier requires 200KHz on the downlink and uplink each.

Operates in the 900MHz and 1800MHz.Powered By

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3GPP Wireless Access Technology Contd


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3GPP Wireless Access Technology-Cont d

GPRS

General Packet Radio Service. Although, data services were already intoduced in the first

phase of GSM, they were circuit switched and therefore very

slow at 9.6kbps

GPRS introduced the use of more than 1 timeslot to send datatraffic.

It also introduced some SGSN and GGSN in the core network

for passing data traffic to the internet.

A throughput of up to 85.6 kbps can be achieved on the

downlink.


3GPP Wireless Access Technology-Contd


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EDGE

Enhanced Data Rate For GSM Evolution Uses advanced modulation to increase data rate at the air

interface.

Can achieve throughput up to 172.8kbps




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UMTS Phase 1

Universal Mobile Telecommunication System It is a 3G technology

The radio interface is based on WCDMA.

Each radio carrier requires 5MHz DL and UL

Achieves speed up to 384kb/s DL and 128kb/s UL

It operates in the 1900MHz and 2100MHz band.

The BTS is called nodeB and the BSC called RNC




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GSM/UTRAN Interworking




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3GPP Wireless Access Technology Cont d

HSPA (UMTS Evolution)

UMTS release 5 defines the HSDPA, while release 6 define

HSUPA

HSDPA

Better spectral efficiency by better allocation of radio

resources

Throughput up to 14.4Mbps

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3GPP Wireless Access Technology Cont d

HSUPA (Enhanhanced-DCH)

Used in the uplink.

Introduction of an Enhanced-DCH for sending traffic.

Use of power control systems to adapt the E-DCH to changing

environment.

Supports data throughput up to 5.8Mbps

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3GPP2 Wireless Access Technology


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gy

3GPP means 3rd Generation Partnership Project2

Responsible for setting the standards for such technologies

as CDMA, EVDO

CDMAOne

CDMA One was the first commercial network based onANSI-95 standards.

CDMAone deploys the PiCH, PCH,SYNC on the forward link

and ACH on the reverse link. TCH on both FL and RL.

Each user data is identified by means of a 42-bit PN code,called long codes.

Low data throughput of 9.6kbps

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CDMA2000-1X

Use convolution codes

CDMA 2000-1x doubled the spectral efficiency.

Expanded the TCH on FL and RL to FCH

Introduced R-SCH and F-SCH

The control channels are improved to R-EACH,F-CCCH,R-CCCH, F-QPCH

Support up to 153.6kbps in FL and RL

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CDMA2000-1X&Evdo

Cdma2000- 1 xEV-DO is designed for high-data-rate, flexible-

latency, and high- quality applications.

Operates in the 800MHz and 1900MHz frequency

It takes advantage of the burst and delay-tolerant nature of

data to increase throughput efficiency.

High spectral efficiency in 1xEV-DO is achieved through AMC,

fast scheduling and H-ARQ

Achievable throughput of up to 3.072Mbps FL and 1.843Mbps

RL in Rev A


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Introduction to Wireless Technology

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