Chapter 10: Existing Wireless Systems: 3G, IS-95 and IMT-2000

Yschen, CSIE, CCU 1

Chapter 10:Existing Wireless Systems:

3G, IS-95 and IMT-2000

Associate Prof. Yuh-Shyan Chen

Dept. of Computer Science and Information Engineering

National Chung-Cheng University

Yschen, CSIE, CCU 2

IS-95

IS-95 uses the existing 12.5-MHz cellular bands to derive 10 different CDMA bands (1.25 MHz per band)

The frequency reuse is 1The channel rate is 1.228 MbpsRAKE receivers are used to combine the output of

several received signalsSixty-four-bit orthogonal Walsh codes (W0 to W64)

are used to provide 64 channels in each frequency band

Yschen, CSIE, CCU 3

Logical Channels in IS-95

Yschen, CSIE, CCU 4

Cont.

Four different rates are usedThe downlink or forward link has a power control

subchannel that allows the mobile to adjust its transmitted power by +/- 1 dB every 1.25 ms

The pilot channel W0 is always requiredThere can be one sync channel and seven paging

channels;• The remaining fifty-six (56 = 64 - 1 - 7) channels are

called traffic channels

Yschen, CSIE, CCU 5

The Pilot Channel

The pilot channel is used by the base station as a reference for all MSs

It does not carry any information and is used for strength comparisons and to lock onto other channels on the same RF carrier

The signals (pilot, sync, paging, and traffic) are spread using high frequency spread signal I and Q using modulo 2 additionThis spread signal is then modulated over a high

frequency carrier and sent to the receiver, where the entire process is inverted to get back the original signal

Yschen, CSIE, CCU 6

Pilot and Sync Channels in IS-95

Yschen, CSIE, CCU 7

Sync channel

The sync channel is an encoded, interleaved, and modulated spread-spectrum signal that is used with the pilot channel to acquire initial time synchronizationIt is assigned the W32

Yschen, CSIE, CCU 8

Paging channel

The paging channels is used transmit control information to the MS

When the MS is to receive a call, it will receive a page from the BS on an assigned paging channel

There is no power control for the paging channel on a per-frame basis

The paging channel provides the MSs system information and instructions

Yschen, CSIE, CCU 9

Paging Channel Generation in IS-95

Yschen, CSIE, CCU 10

Access Channel

The access channel is used by the MS to transmit control information to the BS

The access rate is fixed at 4800 bpsAll MSs accessing a system share the same

frequency When any MS places a call, it uses the access

channel to inform the BSThis channel is also used to respond to a page


Access Channel Generation in IS-95


Forward Traffic Channels

Forward traffic channel are grouped into rate setsRate set 1 has four elements

• 9600, 4800, 2400, and 1200 bpsRate set 2 has four elements

• 14400, 7200, 3600, and 1800 bpsWalsh codes that can be assigned to forward traffic

channels are available at a cell or sector• W2 through W31 • W33 through W63

Only 55 Walsh codes are available for forward traffic channels


The speed is encoded using a variable rate encoder to generate forward traffic data depending on voice activity

The power control subchannel is continuously transmitted on the forward traffic channel (Fig. 10.28 and Fig. 10.29)


Rate Set 1 Forward Traffic Channel Generation in IS-95


Rate Set 2 Forward Traffic Channel Generation in IS-95


The Forward and Reverse Channel Frame Structure is given


Reverse Traffic Channel

For rate set 1, the reverse traffic channel uses 9600, 4800, 2400 and 1200 data rate for transmission

The duty cycle for transmission varies proportionally, with the data rate being 100% at 9600 bps to 12.5 % at 1200 bps


Rate Set 1 Reverse Traffic Generation


Rate Set 2 Reverse Traffic Generation


International Mobile Telecommunications (IMT-2000)

The key futuresHigh degree of commonality of design worldwide Compatibility of service within IMT-2000 and with

fixed networksHigh qualitySmall terminal for worldwide use, including pico,

micro, macro, and global satellite cellsWorldwide roaming capabilityCapability for multimedia applications and a wide

range of services and terminals


International Spectrum Allocation

In 1992, the World Administration Radio Conference (WARC) specified the spectrum for the 3G mobile radio systemEurope and Japan followed the FDD specificationThe lower-band parts of the spectrum are currently

used for DECT and PHS (Personal Handyphone System)

The FCC in the United States has allocated a significant part of the spectrum in the lower band to 2G PCS systems


Cont.

Most of the North American countries are following the FCC frequency allocation


Spectrum Allocation


Service Provided by Third-Generation Cellular Systems

High bearer rate capabilities2 Mbps for fixed environment384 kbps for indoor/outdoor and pedestrian

environment144 kbps for vehicular environment

Standardization workEurope (ETSI: European Telecommunication

Standardization Institute) => UMTS (W-CDMA)Japan (ARIB: Association of Radio Industries and

Business) => W-CDMAUSA (TIA: Telecommunication Industry Assoication)

=> cdma2000


Schedules serviceService started in Oct. 2001 (Japan’s W-CDMA)


Approved Radio Interfaces


Harmonized 3G Systems

A harmonized 3G Systems based on the Operators Harmonization Group (OHG) supportsHigh-Speed data service, including Internet and

Intranet applicationsVoice and nonvoice applicationsGlobal roamingEvolution from the embedded base of 2G systemsANSI-41 (American National Standards Institute –

41) and GSM – MAP core networks


Cont.

Regional spectrum needsMinimization of mobile equipment and infrastructure

costMinimization of the impact of intellectual property

rights (IPRs)The free flow of IPRsCustomer requirements on time

A diagram representing the terrestrial component of the harmonization efforts for IMT-2000 is given in Fig. 10.36


Modular IMT-2000 Harmonization


Universal Mobile Telecommunication System (UMTS)

Network reference architectureIt is partly based on 3G specification, while some 2G

elements have been keptUMTS Release’99 architecture inherits a lots from

the global system for mobile (GSM) model on the core network (CN) side

The MSC basically has very similar functions both in GSM and UMTS

Instead of circuit-switched services for packet data, a new packet node, packet data access node (PDAN), or 3G serving general packet radio service (GPRS) support node (SGSN) is introduced


UMTS Network Architecture


Cont.

This new element is capable of supporting data rates up to 2 Mbit/s

CN elements are connected to the radio network via the Iu interface, which is very similar to the A-interface used in GSM

The main changes in the new architecture are in the radio access network (RAN), which is also called UMTS terrestrial RAN (UTRAN)

There is a totally new interface called Iur, which connects two neighboring radio network controllers (RNC)

• This interface is used for combining macrodiversity, which is a new WCDMA-based function implemented in the RNC


Cont.

BSs (NBs) are connected to the RNC via the Iub interface

Throughout the standardization process, extra effort has been made so that most of the 2G core elements can smoothly support both generations, and any potential changes are kept to a minimum

In 2G, the RAN is separated from the CN by an open interface, called A in circuit-switched (CS) and Gb in packet-switched (PS) networks.

• The former uses time division multiplex (TDM) transport, while packet data are carried over frame reply

In 3G, the corresponding interfaces are called IuCs and IuPs


Cont.

The circuit-switched interface will utilize ATMThe packet switched interface will be based on IP.


UTRAN Architecture


General Protocol Model for UTRAN Interface


Logical Channels in UTRAN

Chapter 10: Existing Wireless Systems: 3G, IS-95 and IMT-2000

Documents

Transcript of Chapter 10: Existing Wireless Systems: 3G, IS-95 and IMT-2000