B3G and MIMO MC-CDMA

1. B3G and MIMO MC-CDMA Speaker : Pei-Yun Tsai Advisor : Tzi-Dar Chiueh 2005/04/25

2. Outline • Beyond 3G • Evolution • Main Features • Possible Techniques • MIMO MC-CDMA • From SISO to MIMO • Synchronization • Channel estimation • MIMO decoding • Conclusion

3. Beyond 3G

4. Evolution of Mobile Systems [1] 2010

5. Frequency efficiency up to 10 b/s/Hz [2] Flexible radio resource management [2] Enlarge the coverage Improve system efficiency Supporting IPv6 multimedia services with [2] Low transmission power (10dB lower than 3G) Eb/N0 less than 3dB at bit error rate of 10-6 for 100 Mb/s. Supporting vehicular speed of 250 km/hr [2] Entirely packet-switch services [3] Main Features of B3G

6. Possible Techniques – Radio Transmission • Modulation [2] – OFDM • Robustness against frequency-selective fading channels in wide bandwidth • Efficient spectrum utilization • Flexibility in subcarrier allocation • Adaptability in subcarrier modulation • In 3GPP [4], • Feasibility study of OFDM

7. Possible Techniques – Radio Transmission • Multiple access scheme [5] – CDMA • Greater coverage with fewer cell sites • Better frequency reuse • Higher capacity • In IMT-2000 family, four out of five systems use CDMA techniques.

8. > Threshold Possible Techniques – Radio Transmission • Advanced detection techniques [6] • Multiuser detection (MUD) techniques • MAI • Near-far effect • Linear receiver • MMSE • Interference canceller (Widely considered) • Parallel IC (PIC) • Successive IC (SIC) • Selective PIC (SPIC) • Turbo MUD • Adaptive detector Received Signal Combining Reliable Signal Cancellation Informative Bit Decision Combining Informative Bit Decision SPIC

9. Possible Techniques – Radio Transmission • MIMO techniques [8] • Providing spatial diversity • STBC • Achieve better QoS for average data rate • STTC • High complexity • Increase frequency efficiency • BLAST • The number of receive antennas is greater than or equal to the number of independent transmit signals. • Poor detection performance over spatially correlated channel. • Exploit knowledge of channel to provide capacity gain • SVD • MIMO may be implemented in HSDPA.

10. Possible Techniques – Radio Transmission • MIMO comparison[8]

11. Possible Techniques – Link Layer • Adaptive modulation and coding techniques (AMC) [6] • Adapt transmission parameters to take advantage of channel conditions. • Increase spectral efficiency. • Also power level, spreading factors, signal bandwidth, and etc. can be adjusted. • Considered in HSDPA and GPRS.

12. Possible Techniques – Resource Management • Radio resource management (RRM) • Admission control (AC) • Reject new connection if causing unacceptable degradation • Power control • Minimize power consumption • Scheduling • Priority-based management

13. MIMO MC-CDMA

14. Consideration • MIMO techniques • STBC • V-BLAST • MIMO decoding • Noise • Multiple access interference (MAI) • Inter antenna interference (IAI)

15. MIMO MC-CDMA Receiver • Synchronization blocks are shared. • JWLS estimation, channel estimation, and combining strategies are different from SISO version.

16. Hardware Requirement • Derotator x 2 • FFT x 2 • Channel estimation x 4 • Equalizer (FEQ) x 4 (More complicated) • Despreading x 4 • SRAM for channel Response x 4 • EQ data delay buffers x 4 • Channel estimates delay buffers x4 • Additional data buffers (N) x 2

17. JWLS Estimation (1/2) • Estimation for residual CFO and TFO • Alternative pilot data are transmitted by antenna 1. • Simple solution: using pilot data separated by 2 symbols Antenna 1 Antenna 0 Training symbol 0 Training symbol 1 Data symbol 0 Data symbol 1 Data symbol 2

18. JWLS Estimation (2/2) • Performance can be improved in the MIMO receiver due to increase of SINR.

19. Channel Estimation • Same performance as in the SISO cases at the same transmitted power. • LS channel estimation • Frequency-domain channel interpolation MIMO SISO

20. Review of SUD in SISO MC-CDMA • Single user detection [9] • MRC : maximize SNR • EGC : no optimization • ORC : reduce MAI • MMSEC (per subcarrier): reduce MAI and noise • TORC : combine EGC and ORC

21. MIMO Processing - STBC (1/2) • Consider SUD • Apply TORC to reduce MAI, inter-antenna interference (IAI), and noise

22. MIMO Processing - STBC (2/2) • Apply MRC. • Consider orthogonality restoring to reduce MAI. • Avoid noise enhancement like TORC. Gk

23. Conclusion and Future Work • The current status of B3G is introduced. • Possible features and techniques are discussed. • Our MIMO MC-CDMA is examined. • Consider the hardware requirement, the synchronization block the channel estimation block and MIMO decoding. • Future work -- • BER comparison between the SISO MC-CDMA and MIMO MC-CDMA.

24. Reference [1] B. Li and et al., ’’Recent advances on TD-SCDMA in China,’’ IEEE Communications Magazine, vol. 1, pp. 30-37, Jan. 2005. [2] P. Zhang and e. al., ’’A vision from the future: beyond 3G TDD,’’ IEEE Communications Magazine, vol. 1, pp. 38-44. Jan. 2005. [3] http://users.ece.gatech.edu/~jxie/4G/ [4] 3GPP, Technical Specification Group Radio Access Network, Feasibility study for orthogoanl frequency division multiplexing (OFDM) for UTRAN Enhancement, TR 25.892, V6.0.0 (2004-06). [5] A. Jamalipour and et al., ’’ A tutorial on multiple access technologies for beyond 3G mobile networks,’’ IEEE Communications Magazine, vol. 2, pp.110-117, Feb. 2005. [6] R. Fantacci and et al., ’’Perspectives for present and future CDMA-based communications systems,’’ IEEE Communications Magazine, vol. 2, pp. 95-100, Feb. 2005. [7] K. Zheng and et al.,’’TD-CDM-OFDM: evolution of TD-SCDMA toward 4G,’’IEEE Communications Magazine, vol. 1, pp. 40-52, Jan. 2005. [8] H. Yang,’’A road to future broadband wireless access: MIMO-OFDM-based air interface,’’IEEE Communications Magazine, vol. 1, pp. 53-60, Jan. 2005. [9] R. Le Gouable and M. Helard,’’Performance of single and multi-user detection techniques for a MC-CDMA system over channel model used for HIPERLAN2,’’ IEEE International Symposium on2000 IEEE Sixth Spread Spectrum Techniques and Applications, Parsippany,New Jersey, Sep. 2000, pp. 718-722.