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

Explore the characteristics and capabilities of 3G, IS-95, and IMT-2000 wireless systems, including frequency reuse, channel rates, logical channels, and spectrum allocation. Learn about the different channels used for pilot, sync, paging, and traffic, as well as the generation of forward and reverse traffic channels.

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

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  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

  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 1 • The channel rate is 1.228 Mbps • RAKE receivers are used to combine the output of several received signals • Sixty-four-bit orthogonal Walsh codes (W0 to W64) are used to provide 64 channels in each frequency band

  3. Logical Channels in IS-95

  4. Cont. • Four different rates are used • The 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 W0is always required • There can be one sync channel and seven paging channels; • The remaining fifty-six (56 = 64 - 1 - 7) channels are called traffic channels

  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 addition • This 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

  6. Pilot and Sync Channels in IS-95

  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 synchronization • It is assigned the W32

  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

  9. Paging Channel Generation in IS-95

  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 bps • All MSs accessing a system share the same frequency • When any MS places a call, it uses the access channel to inform the BS • This channel is also used to respond to a page

  11. Access Channel Generation in IS-95

  12. Forward Traffic Channels • Forward traffic channel are grouped into rate sets • Rate set 1 has four elements • 9600, 4800, 2400, and 1200 bps • Rate set 2 has four elements • 14400, 7200, 3600, and 1800 bps • Walsh codes that can be assigned to forward traffic channels are available at a cell or sector • W2 through W31 • W33through W63 • Only 55 Walsh codes are available for forward traffic channels

  13. 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)

  14. Rate Set 1 Forward Traffic Channel Generation in IS-95

  15. Rate Set 2 Forward Traffic Channel Generation in IS-95

  16. The Forward and Reverse Channel Frame Structure is given

  17. 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

  18. Rate Set 1 Reverse Traffic Generation

  19. Rate Set 2 Reverse Traffic Generation

  20. International Mobile Telecommunications (IMT-2000) • The key futures • High degree of commonality of design worldwide • Compatibility of service within IMT-2000 and with fixed networks • High quality • Small terminal for worldwide use, including pico, micro, macro, and global satellite cells • Worldwide roaming capability • Capability for multimedia applications and a wide range of services and terminals

  21. International Spectrum Allocation • In 1992, the World Administration Radio Conference (WARC) specified the spectrum for the 3G mobile radio system • Europe and Japan followed the FDD specification • The 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

  22. Cont. • Most of the North American countries are following the FCC frequency allocation

  23. Spectrum Allocation

  24. Service Provided by Third-Generation Cellular Systems • High bearer rate capabilities • 2 Mbps for fixed environment • 384 kbps for indoor/outdoor and pedestrian environment • 144 kbps for vehicular environment • Standardization work • Europe (ETSI: European Telecommunication Standardization Institute) => UMTS (W-CDMA) • Japan (ARIB: Association of Radio Industries and Business) => W-CDMA • USA (TIA: Telecommunication Industry Assoication) => cdma2000

  25. Schedules service • Service started in Oct. 2001 (Japan’s W-CDMA)

  26. Approved Radio Interfaces

  27. Harmonized 3G Systems • A harmonized 3G Systems based on the Operators Harmonization Group (OHG) supports • High-Speed data service, including Internet and Intranet applications • Voice and nonvoice applications • Global roaming • Evolution from the embedded base of 2G systems • ANSI-41 (American National Standards Institute – 41) and GSM – MAP core networks

  28. Cont. • Regional spectrum needs • Minimization of mobile equipment and infrastructure cost • Minimization of the impact of intellectual property rights (IPRs) • The free flow of IPRs • Customer requirements on time • A diagram representing the terrestrial component of the harmonization efforts for IMT-2000 is given in Fig. 10.36

  29. Modular IMT-2000 Harmonization

  30. Universal Mobile Telecommunication System (UMTS) • Network reference architecture • It is partly based on 3G specification, while some 2G elements have been kept • UMTS 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

  31. UMTS Network Architecture

  32. 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

  33. 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

  34. Cont. • The circuit-switched interface will utilize ATM • The packet switched interface will be based on IP.

  35. UTRAN Architecture

  36. General Protocol Model for UTRAN Interface

  37. Logical Channels in UTRAN

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