3G Cellular Systems: cdma 2000 David Tipper Associate Professor Graduate Telecommunications and Networking Program University of Pittsburgh 2720 Slides 13 3G Development • 1986 ITU began studies of 3G as: – Future Public Land Mobile Telecom. Systems (FPLMTS) – 1997 changed to IMT-2000 (International Mobile Telecom. in Year 2000) –ITU-Rstudying radio aspects, ITU-T studying network aspects (signaling, services, numbering, quality of service, security, operations) • IMT-2000 vision of 3G – 1 global standard in 1 global frequency band to support wireless data service – Spectrum: 1885-2025 MHz and 2110-2200 MHz worldwide – Multiple radio environments (phone should switch seamlessly among cordless, cellular, satellite) – Support for packet switching and asymmetric data rates • Target data rates for 3G – Vehicular: 144 kbps – Pedestrian: 384 kbps – Indoor office: 2.048 Mbps Æ roadmap to > 10Mbps later • Suite of four standards approved after political fight Telcom 2720 2 Third Generation Standards • ITU approved suite of four 3G standards •EDGE (Enhanced Data rates for Global Evolution) – TDMA standard with advanced modulation and combined timeslots – Provides unification of NA-TDMA and GSM – Only meets some of the 3G requirements (2.75G!) • UMTS (Universal Mobile Telephone Service) also called WCDMA (wideband CDMA) – Dominant standard outside of US and leading standard for 3G worldwide – Viewed as 3G migration path for GSM/TDMA systems • CDMA 2000 – Competes directly with UMTS/W-CDMA – Evolutionary path for IS-95 which is the dominant standard in the US • TD-SCDMA : Stand alone standard developed in China Telcom 2720 3 cdma2000 Major Characteristics – Evolves to meet IMT 2000 data rate requirements for 3G – Backward compatibility with IS-95B (cdmaone) – Support for data services • High data rate (up to 2 Mbps) • Optimized for packet and circuit data services – Support for multimedia services • Concurrent channels (support concurrent communication channels for related data streams) • QoS negotiation and control mechanisms – Reuse/adoption of existing standards • Reuse IS-95 standards (Air Interface) and IS-41 standards (networking), • Mobile IP, RADIUS, etc. Telcom 2720 4 3G Evolution: major streams 2G 2.5G 3G CDMA2000 1xEV-DO IS-95B multicarrier Multiple revs cdmaone IS95 1xRTT 1xEV-DV IS-95A Multiple revs GSM GSM GPRS UMTS HSDPA HSUPA EDGE Briefly review IS95 and cdma2000 1xRTT Telcom 2720 5 2G cdmaOne (IS-95) BTS — Base Transceiver Station BSC — Base Station Controller IS-95 • cdmaOne MS — Mobile Station MSC — Mobile Switching Center • Voice HLR — Home Location Registry 14.Kbps or SMS-SC — Short Message BTS Service — Serving Center A Ref (A1, A2, A5) variable STM — Synchronous Transfer Mode MS STM over T1/T3 rate up to BSC 9.6 Kbps Proprietary Interface HLR • Data STM over T1/T3 or Ater Ref (A3, A7) 9.6kbps or BTS AAL1 over SONET PSTN 14.4 Kbps IS-95 • 1.25 MHz A Ref (A1, A2, A5) carrier STM over T1/T3 MSC BTS • 64 Walsh MS codes per BSC carrier Proprietary Interface A1 — Signaling interface for call control and mobility A5 — Full duplex bearer interface byte stream Management between MSC and BSC A7 — Bearer interface for inter-BSC mobile handoff A2 — 64 kbps bearer interface for PCM voice A3 — Signaling interface for inter-BSC mobile handoff Telcom 2720 6 IS-95 CDMA - Radio Aspects • IS-95 is an air interface standard only • System use FDD/FDMA/CDMA • FDD => Uplink and Downlink channels separated according to Cellular band or PCS band regulatory requirements • Bandwidth after spreading is 1.23 MHz with guardband becomes 1.25 MHz • IS-95a standard designed for AMPS cellular band – Channel operates at 1.228 Mchips/sec – A 64 bit spreading code is used (Walsh Code) – Modulation is QPSK and slight variations OffsetQPSK Telcom 2720 7 Modulation and coding features Modulation Quadrature phase shift keying or variations Chip rate 1.2288 Mcps Nominal data rate 9.6 kbps (Rate Set 1) Filtered bandwidth 1.23 MHz -> 1.25 MHz with guard band Coding Convolutional coding Constraint length = 9 Viterbi decoding Interleaving With 20 ms span Telcom 2720 8 Codes used in IS-95 systems • Walsh codes – They are the “orthogonal codes” used to create “logical channels” on the up/downlink (at the same time and within the same frequency band) • PN (pseudo-noise) codes – They are used to distinguish between transmissions from different cells and are generated using “linear feedback shift registers” – Basically a pseudo-random number generator – They have excellent autocorrelation properties – Two short PN codes and a long PN code are used in IS-95 that have periods of 215 – 1 and 242 –1 • Convolutional codes for error correction • Block codes with interleaving and error correction Telcom 2720 9 IS-95 Logical Channels • CDMA systems define multiple channels per frequency channel • Pilot channel – Provides a reference to all signals (beacon) • Sync channel – Used for obtaining timing information • Paging channel – Used to “page” the mobile terminal when there is an incoming call • Traffic channel – Carries actual voice or data traffic : fundamental code channel • Up to seven supplemental code channels Pilot Forward Sync Variable-Bit-Rate Paging User Info. Power Control Traffic Signaling Messages Reverse Access Variable-Bit-Rate User Info. Traffic Signaling Telcom 2720 Messages 11 IS-95 Forward (Downlink) Channel One Forward CDMA Link, 1.25 MHz in the 824 – 849 MHz bands PCH PCH TCH TCH TCH TCH Pilot Synch 1 7 1 8 25 55 W W W 16 W63 W0 W32 W1 7 8 Fundamental Mobile Power Fundamental Mobile Power Code Channel Control Code Channel Control Data Subchannel Data Subchannel Telcom 2720 14 Reverse CDMA Channel One Reverse CDMA Link, 1.25 MHz in the 824 – 849 MHz Access Access Access Traffic Traffic Access Channel Channel Channel Channel Channel Channel 0, PCH1 N, PCH1 0,PCH 7 1 T Fundamental Supplementary Supplementary Supplementary Supplementary Code Channel Code Channel Code Channel Code Channel Code Channel Data Data Data Data Data Telcom 2720 15 IS-95 evolution to 3G IS-95B CDMA2000 1xEV-DO: Evolved Data Optimized Uses multiple code channels Classified as a “3G” system Data rates up to 64kbps 2.4Mbps Down 153kbps Up Many operators went direct to 1xRTT Use new or existing spectrum IS-95B CDMA2000 CDMA 1xEV-DO Multi-carrier EV-DO IS-95A IS-95A 1xRTT 1xEV-DV 14.4 kbps data rate CDMA2000 1xRTT: CDMA2000 1x Evolved Data/Voice First phase in CDMA2000 evolution (EV-DV) Easy co-existence with IS-95A air interface Integrate voice and data on a single Release 0: max 153 kbps Up/Down channel . 3.1Mbps Downlink Release A: max 307 kbps Down/153 1.2 Mbps Uplink kbps Up Future development on hold as EV-DV not widely adopted Telcom 2720 16 IS-95/cdma2000 Protocol Revisions IS95 (cdmaone standard) TIA standards http://www.tia.org 1. IS-95/J-STD-008 (cdmaone) 2. IS-95A 3. IS-95A+TSB-74 4. TIA/EIA-95B minimum required features 5. TIA/EIA-95B all required features cdma2000 standards 3GPP2 http://www.3gpp2.org 1. CDMA2000 Release 0 (cdma2000 1x-RTT) 2. CDMA2000 Release A CDMA 2000 EVDO 1) Release 0 2) Revision A, B, C Source: Qualcomm CDMA University Student Guide. Telcom 2720 17 cdma2000 • cdma2000 1xRTT (Radio Transmission Technology) • 2.5G service over IS-95a, b, cdmaone systems • overlay like GPRS • Uses same 1.25MHz channels as IS-95 – cdma2000 slight changes to IS-95 radio link • Extend number of Walsh codes on DownLink from 64 to 128 • Reverse Link Pilot for coherent demodulation – Mobile broadcasts pilot (Walsh code 0) as well as traffic channels • Forward link Fast Power Control based on reverse link pilot – reduces interference to users on same frequency in cell and between cells Telcom 2720 18 cdma2000 • cdma2000 1xRTT (Radio Transmission Technology) • One user can have Multiple Walsh codes (Supplemental Channels) to get greater data rate • Data rates 153Kbps Up/Down • Release A: provides higher downlink rate (307Kbps) adds – Turbo codes –SMV: Selectable Mode codebook excited LPC Vocoder » Defined by 3GPP2 for CDMA2000 » SMV 4 rates: 8.5, 4, 2 & 0.8kbps » Lower bit rates allow more error correction » Dynamically adjust to radio interference conditions – Substantial additions in the backhaul • In fashion similar to GPRS separates voice (circuit switched) and packet data at BSC • Based on IP protocols Telcom 2720 19 CDMA2000 1x Network HLR STM over T1/T3 or IS-2000 AAL1 over SONET PSTN A Ref (A1, A2, A5) STM over T1/T3 MSC BTS MS AQuarter Ref (A10, A11) BSC SMS- Proprietary Interface IP over Ethernet/AAL5 SC Internet BTS IP IP IP Router Firewall Router BTS - Base Transceiver Station RADIUS over UDP/IP BSC - Base Station Controller MS - Mobile Station MSC - Mobile Switching Center HLR - Home Location Registry Privata SMS-SC - Short Message Data Service - Serving Center Network STM – Synchronous Transfer Mode AAA Home Agent PDSN – Packet Data Serving Node AAA – Authentication, Authorization, and Accounting PDSN Home Agent – Mobile IP Home Agent A10 – Bearer interface between BSC (PCF) and PDSN for packet data A11 – Signaling interface between BSC (PCF) and PDSN for packet data Telcom 2720 20 Packet Data Serving Node (PDSN) • PDSN – similar to SGSN in GPRS – Establish, maintain, and terminate PPP sessions with mobile station – Support simple and mobile IP services – Route packets between mobile stations and external packet data networks – Collect usage data and forward to AAA server • AAA (authentication, authorization, and accounting) server – Authentication: PPP and mobile IP connections – Authorization: service profile and security key distribution and management – Accounting: usage data for billing – uses RADIUS (Remote Authentication Dial in User Service) protocol Telcom 2720 21 Simple IP Service (CDMA2000) Simple IP: the user is assigned a dynamic IP address from the local PDSN and is provided IP routing service by a service provider network. The user retains its IP address as long as it is served by a radio network which has connectivity to it’s address assigned by the PDSN.