School of Electronic, Electrical and Systems Engineering

This project has been set in the context of the ever increasing demand for high data rate transmission over wireless access, underpinned by the growth of increasingly sophisticated multimedia services. This is very challenging due to the quality of service requirements and tight constraints on available radio spectrum in practical systems. We believe it is possible to support very high speed data transmission with high quality of services through the exploitation spatial diversity, i.e. exploiting the plurality of paths provided by having multiple antennas at the transmitter and most probably at the receiver too. The diversity techniques will be based on channel state information feedback. Since such channel state information requires considerable bandwidth in the reverse link for its transmission, we are investigating various novel feedback quantization techniques based on Grassmannian plane (subspace) packing to reduce feedback overhead significantly. The work is also focussed on possible applications to cognitive radio networks.

1) R. Krishna, K. Cumanan, Z. Xiong and S. Lambotharan, “A Novel Cooperative Relaying Strategy For Wireless Networks With Signal Quantization,” accepted for publication in IEEE Trans. Vehicular Technology, 2009.

2) R. Krishna, Z. Xiong and S. Lambotharan, “A Cooperative MMSE Relay Strategy for Wireless Sensor Networks,”  in IEEE Signal processing Letters, vol. 15, 2008.

3) Z. Xiong, K. Cumanan and S. Lambotharan, “On the Benefits of Subspace Dimension Reduction for Grassmannian Multiuser Beamformers,” IEEE Statistical Signal Processing Workshop, Cardiff, Sept. 2009.

4) M. Irfan, R. Krishna, Z. Xiong and S. Lambotharan, “Interference Mitigation Based Signal Forwarding Strategy for Wireless Relay Networks.,” EUSICO, Glasgow, UK, Aug. 2009

5) Z. Xiong, R. Krishna, S. Lambotharan and J.A. Chambers “Multiuser Orthogonal Space-Division Multiplexing with Iterative Water-Filling Algorithm,” IEEE VTC Spring, Barcelona, April 2009.

6) K. Cumanan, R. Krishna, Z. Xiong and S. Lambotharan, “SINR Balancing Techniques and its Comparison to Semidefinite Programming Based QoS Provision for Cognitive Radios,” IEEE VTC Spring, Barcelona, April 2009.

7) R. Krishna, K. Cumanan, Z. Xiong and S. Lambotharan, “A Semideifinite Programming Based Cooperative Relaying Strategy for Wireless Mesh Networks with Relay Signal Quantization,” IEEE VTC Spring, Barcelona, April 2009.

8) Z. Xiong, S. Lambotharan and J.A. Chambers, “A GMD-Based Precoding Scheme for Downlink Multiuser Multistream MIMO Channels,” Asilomar conf. on Sig., Sys., and Comp., Pacific Grove, USA, Nov. 2008.