Communications

Members:

Bariş Özgül

Ultra Wideband (UWB) Communications

Researchers:

Nazlı Güney, Mutlu Koca, Hakan Deliç

Description:

UWB transmission, where information is sent over impulse-like radio (IR) waveforms, has emerged as an exciting technology for commercial wireless communication systems and local area networking. Despite their advantages especially in short range, such as low power consumption, carrier-free transmission, utilization of low-complexity transceivers, capability to co-exist with existing broadband systems, ultra wideband systems can only be realized after major design issues have been solved.

Our research in this area involves the design low-power UWB multiple access schemes with low complexity multi-user receivers. Our investigation involves code optimization for multiple access protocols, transceiver design for UWB systems employing time-hopping and multi-band orthogonal pulses, design of low complexity demodulation and decoding structures and interference cancellation algorithms, space-time signal processing to enable the use of multiple transmit/receive antennas in UWB systems.

Turbo Processing

We investigate the application of the turbo principle in equalization of MIMO broadband wireless systems, in demodulation of spectrally efficient modulation schemes and in decoding packet video transmission over IP.

Turbo Processing for video over IP

Researcher: Mutlu Koca

Description: We investigate the joint use of multiple description coding and channel coding for systems transmitting data over heterogeneous networks so as to achieve resilience against packet losses and protection against channel errors. Observing that the two coding blocks form a serial concatenated code, we consider a turbo decoding scheme passing soft messages between a SISO channel decoder and a source reconstructor. We also investigate the problem of optimal redundancy allocation between the blocks of such heterogeneous coding structures. Another objective of this research is to apply iterative processing on advanced quantization methods such as trellis coded quantization.

Turbo Equalization

Researcher: Barış Özgül, Mutlu Koca

Description: Conventional turbo equalizers relying on trellis-search algorithms are not applicable to broadband wireless systems which are usually characterized by severe channel dispersion. That is why we investigate the design of low complexity turbo equalizers for MIMO broadband wireless systems. Specific applications include turbo equalizer and demodulator design for spectrally efficient coded modulation schemes, such as trellis coded modulation (TCM), multilevel coded modulation (MCM), bit-interleaved coded modulation (BICM) and continuous phase modulations. One particular objective of this research is to perform transceiver optimization using iterative receiver convergence analysis.

Publications:

M. Koca, E. Fabre and A. Roumy, “Turbo decoding of multiple descriptions with quantized frame expansions,” in 2nd International Symposium on Image/Video Communications over Fixed and Mobile Networks, Brest, France, July 7-9, 2004.

M. Koca and B.C. Levy, “Broadband beamforming for joint interference cancellation and turbo equalization,” submitted to IEEE Transactions on Wireless Communications, 2003. Revised in July 2004.

M. Koca and B.C. Levy, “Doubly-iterative turbo equalization of space-time bit-interleaved coded modulation,” in Proc. IEEE GLOBECOM 2004, Dallas, TX, USA, Nov. 29-Dec. 3, 2004.

M. Koca and B.C. Levy, “Turbo space-time equalization of TCM for broadband wireless channels,” IEEE Transactions on Wireless Communications, vol. 3, pp. 50-59, Jan. 2004.

M. Koca and B.C. Levy, “Broadband beamforming for joint interference cancellation and low complexity turbo equalization,” in Proc. IEEE Globecom 2003, San Francisco, CAUSA, Dec. 1-5, 2003.

M. Koca and B.C. Levy, “Low-complexity turbo space-time equalization for MIMO wireless systems,” in Proc. 3^rd International Symposium on Turbo Codes and Related Taopics, Brest, France, Sept. 1-5, 2003.

M. Koca and B.C. Levy, “Space-time interference cancellation and turbo equalization of TCM for broadband wireless channels,” in Proc. 35^th IEEE Asilomar Conference on Signals Systems & Computers, Pacific Grove, CA, USA, Nov. 4-7, 2001.

Theses