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

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

19. 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

20. Rate Set 1 Reverse Traffic Generation

21. Rate Set 2 Reverse Traffic Generation

22. 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

23. 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

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

25. Spectrum Allocation

26. 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

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

28. Approved Radio Interfaces

29. 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

30. 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

31. Modular IMT-2000 Harmonization

32. 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

33. UMTS Network Architecture

34. 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

35. 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

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

37. UTRAN Architecture

38. General Protocol Model for UTRAN Interface

39. Logical Channels in UTRAN