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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. IS-95. - PowerPoint PPT Presentation
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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
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Logical Channels in IS-95
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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
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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
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Pilot and Sync Channels in IS-95
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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
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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
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Paging Channel Generation in IS-95
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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
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Access Channel Generation in IS-95
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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
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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)
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Rate Set 1 Forward Traffic Channel Generation in IS-95
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Rate Set 2 Forward Traffic Channel Generation in IS-95
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The Forward and Reverse Channel Frame Structure is given
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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
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Rate Set 1 Reverse Traffic Generation
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Rate Set 2 Reverse Traffic Generation
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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
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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
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Cont.
Most of the North American countries are following the FCC frequency allocation
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Spectrum Allocation
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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
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Schedules serviceService started in Oct. 2001 (Japan’s W-CDMA)
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Approved Radio Interfaces
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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
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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
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Modular IMT-2000 Harmonization
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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
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UMTS Network Architecture
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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
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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
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Cont.
The circuit-switched interface will utilize ATMThe packet switched interface will be based on IP.
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UTRAN Architecture
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General Protocol Model for UTRAN Interface
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Logical Channels in UTRAN