Adaptation Techniques in Wireless Packet Data Services Speaker: Chih-Wei Wang Advisor: Li-Chun Wang

Abstract Cellular systems are designed to achieve percent coverage for voice users — SINR is over design target over percent of the cell area For packet data service, larger SINR can be used to provide higher data rates — reducing coding or spreading and/or increasing constellation density Cellular spectral efficiency can be increased

Motivation — Explosive growth of internet and dramatic increase in demand for increasing capacity Basic and enhanced voice services (audio conferencing, voice mail) Low-data-rate services (messaging, , fax) Medium-data-rate services (file transfer, internet access, kb/s) High-data-rate services (high speed packet and circuit-based network access) Multimedia services

A summary of rate adaptation for packet data services in second- and third-generation cellular standards

(cont’d)

Rate adaptation in CDMA achieved through a combination of variable spreading, coding, and code aggregation. How to achieve higher data rates? IS-95B CDMA — Walsh code aggregation WCDMA and cdma2000 — Combination of variable spreading and coding

Rate adaptation in TDMA slot-by-slot data rate adaptation—adaptive coding and modulation symbol rate and block size—unchanged How to achieve higher data rates? Time slot aggregation: GPRS-136 —(1-3 time slots/20 ms) EGPRS —(1-8 time slots/GSM frame) higher throughput —incremental redundancy transmission

Channel quality estimation CDMA— Pilot strength measurements are used to estimate the SINR at the receiver IS-95B and cdma2000 — Pilot strength measurement message (PSMM) Supplemental channel request message (SCRM) WCDMA — additionally include block error rate, BER, received power, path loss, downlink SINR measurements

Channel quality estimation (cont’d) TDMA— Frame error rate Mean and standard deviation of symbol error rate (SER) or BER Average SINR GPRS and EGPRS — Measurement reports are included in supervisory ARQ status messages

Packet Data over CDMA IS-95 Revision B Higher data rate is provided through code aggregation — up to 8 codes maybe assigned for the duration of a burst Fundamental code channel (FCH): 9.6 kb/s Supplemental code channels (SCHs): 9.6 kb/s each Data rate controlled by base station, assigned to mobile station through supplemental channel assignment message (SCAM)

Packet Data over CDMA IS-95 Revision B (cont’d) Channel quality feedback is indicated to the transmitter through pilot strength measurements provided by the mobile in pilot strength measurement messages and in the supplemental channel request message (SCRM) on the uplink

Packet Data over CDMA cdma2000 — Providing several medium access control (MAC) layer enhancements To minimize access and setup delays, for fast access and setups with efficient air interference Physical layer provides a single SCH with variable spreading gain

Packet Data over CDMA cdma2000 (cont’d) Other physical layer enhancements — turbo coding, a reverse link pilot for coherent detection, fast forward link power control, forward link dedicated pilots for operation with narrow-band antennas

Packet Data over CDMA Wideband CDMA (WCDMA) Similar set of physical layer enhancements as cdma2000 Supports data rates up to Mb/s in 5 MHz BW through variable spreading and code puncturing from a rate 1/3 base channel code A continuum of data rates is achieved by using rate matching

Packet Data over CDMA Wideband CDMA (WCDMA) (cont’d)

Burst Allocation and Management in CDMA Data rate adaptation for packet data service in CDMA cellular systems requires dynamic bandwidth management and burst allocation

Higher Data Rates through Code Aggregation Code aggregation may be used to provide even higher data rates to users with favorable SINRs, or to the same user requiring services with multiple QoS requirements

Packet Data over TDMA GSM — General Packet Radio Service (GPRS) IS-136 TDMA — GPRS-136 GPRS-136 — TDMA packet data standard Based on GPRS 30 kHz for the physical layer allows for connection to the ANSI-41 network Enhanced Data Rates for GSM Evolution (EDGE)

Packet Data over TDMA (cont’d) EDGE — enhanced circuit-switched data (ECSD) EGPRS ECSD — enhancement for circuit-mode data EGPRS — enhancement for packet-mode data How to achieve variable data rates? Adaptive coding, adaptive modulation, incremental redundancy

Packet Data over TDMA GPRS-136 To achieve higher throughput — adaptive modulation and incremental redundancy Incremental redundancy — each RLP segment is coded into D data blocks and D parity blocks

Packet Data over TDMA GPRS-136 (cont’d) Adaptive modulation — modulation is switched between 4-, 8-, and 16-level modulation as a function of the SINR

Packet Data over TDMA GPRS Using adaptive coding with Gaussian minimum shift keying (GMSK) modulation but no incremental redundancy As in GPRS-136, operation on multiple time slots is used to achieve higher data rates

Packet Data over TDMA EGPRS 9 modulation schemes, MCS-1to 9, are defined — 4 code rate with GMSK and 5 code rates with 8-PSK modulation 3 RLC block sizes are defined for the nine modulation and coding formats — providing plenty of flexibility for block-by-block rate adaptation

Summary Channel quality feedback mechanisms have been defined to carry out rate adaptation. Further work is needed to obtain fast and accurate channel quality measurements Resource management that permits ideal exploitation of these adaptation schemes as a function of SINR is still an open area of research

Summary (cont’d) CDMA has features that permit efficient sharing of the available resource Use of pilot strength measurements for efficient power and interference management Low overhead dedicated or common control channels with discontinuous transmission

Summary (cont’d) TDMA has features that permit achieving high data rates Incremental redundancy with separately protected headers Dynamic adaptation between different coding and modulation schemes Proposed channel quality metric based on Euclidean distance Aggressive reuse schemes for achieving the highest spectral efficiency