演講公告

1. 演講公告 Adaptive Modulation, Coding, Transmit Diversity And Networking For Next- Generation Wireless Systems Prof. Lajos Hanzo, Univ. of Southampton, UK. Abstract : 1. A FUTURE-PROOF MC-CDMA STANDARD FRAMEWORK Multi-standard operation is an important requirement for the future generations of wireless systems. This overview commences with the portrayal of a versatile broadband multiple access scheme, combining frequency-hopping (FH) with multicarrier DS-CDMA (FH/MC DS-CDMA). The proposed FH/MC DS-CDMA scheme is capable of meeting the requirements of future generations of wireless systems, by supporting backwards compatibility with the existing 2nd- and 3rd- generation systems, while also introducing more advanced techniques facilitated by the employment of Software Defined Radios (SDR) and efficient adaptive base-band algorithms [1]-[8]. 2. ADAPTIVE VERSUS SPACE-TIME CODED OFDM/MC-CDMA The presentation continues by demonstrating that Symbol-by-symbol adaptive Orthogonal Frequency Division Multiplex (OFDM) modems have the potential of counteracting the near instantaneous channel quality variations of wireless channels and hence attain an increased throughput in comparison to their .fixed-mode counterparts. By contrast, various diversity techniques, such as Rake receivers and space-time coding, mitigate the channel quality variations in their effort to obtain a reduced BER. This overview investigates a combined system constituted by a constant-power adaptive modem employing space-time coded diversity techniques in the context of both OFDM and MCCDMA. The combined system can be configured to produce a constant uncoded BER and exhibits virtually error free performance, when a turbo convolutional code is concatenated with a space-time block code. It was found that the advantage of the adaptive modem erodes, as the overall diversity-order increases [7]. 3. ADAPTIVE NETWORKING The results of [1]-[8] suggest that the joint benefits of employing both adaptive physical and adaptive network-layer performance enhancement techniques are substantial. More specifically, conventional systems would drop a call in progress, if the communications quality falls below the target quality of service and it cannot be improved by handing over to another physical channel. By contrast, the adaptive transceivers of the near future are expected to simply ’instantaneously drop the throughput, rather than dropping the call’ by reconfiguring themselves in a more robust mode of operation. Our results demonstrated that the proposed beam-forming and adaptive transmission aided techniques may double the expected teletraffic capacity of the system, whilst maintaining the same performance as their conventional .fixed-mode counterparts [6]. The overview concludes by highlighting a range of open problems. 4. REFERENCES [1] L. Hanzo, W.T. Webb, T. Keller: Single- and Multi-carrier Quadrature Amplitude Modulation: Principles and Applications for Personal Communications, WATM and Broadcasting; IEEE Press-John Wiley, 2nd edition, June 2000, ISBN 0-471-49239-6, p 762 [2] L. Hanzo, P. Cherriman, J. Streit: Wireless Video Communications: Second to Third Generation and Beyond, IEEE Press, February 2001 1, ISBN 0-7803-6032-x, p 1092 [3] L. Hanzo, F.C.A. Somerville, J.P. Woodard: Voice Compression and Communications: Principles and Applications for Fixed and Wireless Channels; IEEE Press-John Wiley, August 2001, ISBN 0-471-15039-8, p 672 [4] L. Hanzo, T.H. Liew, B.L. Yeap: Turbo Coding, Turbo Equalisation and Space-Time Coding, John Wiley, August 2002, ISBN 0-470-84726-3, p 766 [5] L. Hanzo, C.H. Wong, M.S. Yee: Adaptive wireless transceivers: Turbo-Coded, Turbo-Equalised and Space-Time Coded TDMA, CDMA and OFDM systems, John Wiley, March 2002, ISBN 0-470-84689-5 p 752 [6] J.S. Blogh, L. Hanzo: Third-Generation Systems and Intelligent Wireless Networking - Smart Antennas and Adaptive Modulation, John Wiley, April 2002, ISBN 0-470-84519-8 p430 [7] L. Hanzo, M. M¨unster, B.J. Choi and T. Keller: OFDM and MC-CDMA for Broadband Multi-user Communications, WLANs and Broadcasting, John Wiley - IEEE Press, May 2003, 1010 pages [8] L. Hanzo, L-L. Yang, E-L. Kuan and K. Yen: Single-and Multi-Carrier CDMA: Multi-User Detection, Space-Time Spreading, Synchronisation, Standards and Networking, IEEE Press - John Wiley, June 2003, 1060 pages Biography : During his 27-year carreer Lajos Hanzo has held various academic and research positions in Hungary, Germany and the UK. Since 1986 he has been with the University of Southampton, where he holds the Chair of Telecommunications. Over the years he has co-authored 10 books on mobile radio communications, published about 450 research papers. Lajos has also been awarded a number of distinctions and he is an IEEE Distinguished Lecturer. For further information on research in progress and for associated papers and book chapters please refer to http://www-mobile.ecs.soton.ac.uk 時間 : 92年9月16日(星期二)下午5:00~7:00 地點 : 電機二館 105 視聽教室 台大電信所 92.09.05