1/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica “Turbo Soft Combining Hybrid ARQ Techniques: Theory and Application to 3G Wireless Networks” Romano Fantacci Full Professor Francesco Chiti Ph.D. Department of Electronics and Telecommunications University of Florence Via di S. Marta, 3 I Florence, ITALY

2/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Outline i.Introduction 1.Soft combining principle Soft Input Combining Soft Output Combining 2.Theoretical analysis AWGN Multipath fading channel 3.Application to UMTS systems 4.Conclusions

3/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica i. Introduction Soft Combining techniques Service Classes UMTS/HSDPA Conversational Streaming Interactive Background IPvx Elastic Stream DiffServ Expedited Forward Assured Forward Best Effort Traffic class Traffic attributes Priority[integer] Bit rate (max., guar.)[bps] PDU Size[Byte] Residual Error Ratio[%] Transfer delay[s] Delivery order[integer] PHY MAC LLC

4/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Automatic Repeat reQuest (ARQ) protocols –Erroneous packets detection by means of a CRC; –Packet retransmission through dedicated signals (ACK/NACK) Stop and Wait (SW), Go Back N (GBN), Selective Repeat (SR). Forward Error Correction (FEC) techniques –Erroneous packet correction by means of a suitable channel code (convolutional codes; turbo codes). i. Introduction Soft Combining techniques Reliable packet communications

5/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica FEC techniquesARQ protocols MAC Layer dutyLLC Layer duty Heavy decodingLight Decoding Without control signalingWith onerous control signaling Throughput limited by added redundancies Throughput limited by number of needed retransmissions service outage proneStall prone Well suited for fixed wireless nwsConceived for wired nws Traditional approaches comparison Soft Combining techniques i. Introduction

6/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Hybrid ARQ (H-ARQ) approaches Type I channel coding and retransmission mechanism are merely integrated within the same scheme Type II traditional approaches are harmonized and jointly optimized by keeping trace of transmission/reception process (e.g. Chase Combining) Type III transport formats are dynamically updated to cope with the signal quality variations (e.g. Incremental Redundancy) Soft Combining techniques i. Introduction Acknowledgement Driven (PHY+MAC+LLC)Soft Combining (MAC+LLC)

7/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Functional block diagram Buffer Receiver Decoder LOGIC Soft Combining techniques 1. Soft combining principle Despreading Descrambling Rake Demodulator  DEMUX    BCJR

8/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Packet replicas are combined via a soft metric, maximizing the Euclidean distance among symbols; Combination schemes follow a diversity technique: –Maximum Ratio Combining (MRC); –Equal Gain Combining (EGC); –Weighted Gain Combining (WGC). Diversity gain is advantageously considered Soft Input Combining H-ARQ Soft Combining techniques 1. Soft combining principle

9/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Last packet replica is combined via a soft metric to the decoding process outputs, maximizing the Euclidean distance among codewords; Suitable for SISO decoder (turbo principle) Combination schemes follow a diversity technique: –Maximum Ratio Combining (MRC); –Equal Gain Combining (EGC); –Weighted Gain Combining (WGC). Diversity gain and decoding gain are considered Soft Output Combining H-ARQ Soft Combining techniques 1. Soft combining principle

10/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica OUTIN : input combining : output combining Soft Combining techniques 1. Soft combining principle Coding gain: under Gaussian output approximations (except for interdiction and saturation regions)

11/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Coder Layer II - LLC Buffer New Frame Previous Frame Logic Pack CRC adder PackCRC PackCRCRedundancy ACK/NACK Modulator Layer II - MAC Layer I -PHY Transmitter protocol stack Soft Combining techniques 1. Soft combining principle

12/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Decoder Layer II - LLC Buffer Previous OUTPUT Previous INPUT Logic Pack CRC check PackCRCPackCRCRedundancy Demodulator Layer II - MAC Layer I -PHY Receiver protocol stack ACK/NACK Soft Combining techniques 1. Soft combining principle

13/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica BER AWGN channel Soft Input Combining Soft Output Combining SOC outperforms SIC Soft Combining techniques 2. Theoretical analysis

14/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica FER AWGN channel Average needed retransmissions Throughput frame length Soft Combining techniques 2. Theoretical analysis

15/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica BER  k Multipath fading channel Soft Input Combining Soft Output Combining joint pdf of kL fading coefficients (  1   kL ) Soft Combining techniques 2. Theoretical analysis

16/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica BER Multipath fading channel FER Soft Combining techniques 2. Theoretical analysis

17/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Goodput multiplicative increase/multiplicative decrease SLW congestion control Multipath fading channel Soft Combining techniques 2. Theoretical analysis Prob that current block has been transmitted K times at time n Timeout value is equal to K  (RTT) Initial SLW size

18/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica UMTS uplink (3GPP complain); Bit rate: 30 kb/s – 120 kb/s; Turbo coder/decoder: –(1,15/13) 8 ; –R=1/2; –MAP-BCJR. Interleaver (3GPP complain); ETSI urban channel (6 paths). Operative assumptions Soft Combining techniques 3. Application to UMTS systems

19/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Frame Error Rate Better FER (QoS) or reduced power wasting (lesser electromagnetic pollution) Soft Combining techniques 3. Application to UMTS systems

20/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Throughput Better FER (QoS) or better throughput or reduced delay Soft Combining techniques 3. Application to UMTS systems

21/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Cell capacity (64 nominal users) Capacity increasing up to 20 oversaturated users (    ) Soft Combining techniques 3. Application to UMTS systems

22/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Goodput Reduced power or higher effective bandwidth Soft Combining techniques 3. Application to UMTS systems

23/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica Conclusions QoS oriented services within wireless networks Cross-layer adaptive protocols design for reliable applications Soft Combining techniques (H-ARQ type II) Analytical performance evaluation Application to 3G public systems (UMTS)

24/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica 1.F. Chiti, R. Fantacci, F. Versaci: “Turbo Soft Combining Hybrid ARQ Techniques: Theory and Application to 3G Wireless Networks”, Annals of Telecommunications: Special Issue on Turbo Codes, January F. Chiti, R. Fantacci, F. Versaci: “An Efficient Turbo Soft Combining Hybrid ARQ Techniques for Application in Wireless Communication Systems”, IEEE Trans. on Comm., submitted for publication. 3.F. Chiti, R. Fantacci: “A Soft Combining Hybrid ARQ Technique applied to Throughput Maximization within 3G Satellite IP Networks”, IEEE Trans. on Vehic. Tech., submitted for publication. Publications Journal papers Conference papers 1. 1.F. Chiti, R. Fantacci, T. Pecorella, F. Versaci: “Soft Combining Hybrid ARQ Techniques Application to Packet Communications within 3G Wireless Networks”, in Proc. of IEEE WCNC F. Chiti, R. Fantacci, T. Pecorella, F. Versaci: “Soft Combining Hybrid ARQ Techniques Application to 3G Wireless Networks”, in Proc. of IEEE ICC F. Chiti, R. Fantacci, G. Mennuti, D. Tarchi: “Dynamic SIR based Admission Control Algorithm for 3G Wireless Networks”, in Proc. of IEEE ICC F. Chiti, R. Fantacci, F. Versaci: “Turbo Soft Combining Hybrid ARQ Techniques: Theory and Application to 3G Wireless Networks”, in Proc. of IEEE ISTC 2003.

25/25 COST th MCM, Barcelona October Laboratorio di Elaborazione Numerica dei Segnali e Telematica “Turbo Soft Combining Hybrid ARQ Techniques: Theory and Application to 3G Wireless Networks” Romano Fantacci Full Professor Francesco Chiti Ph.D. Department of Electronics and Telecommunications University of Florence Via di S. Marta, 3 I Florence, ITALY