Space-Time Receivers for Relay-Assisted Wireless MIMO Channels


Multiple-input multiple-output (MIMO) communication systems are able to substantially increase the data rate (bit/sec) or to improve the transmission quality (bit error rate) in a wireless link [1]. However, a necessary condition to achieve potentially higher data rates is a channel matrix with high rank which is provided by rich-scattering radio channels. In line-of-sight propagation environments (for example in a future wireless LAN which operates in the ISM band 24GHz) the scattering will be low and the resulting channel matrix rank deficient. Recent research has shown [2], [3] that wireless relay networks can help to solve this problem: Instead of transmitting the data packets directly to the destination, the packets are sent first to some amplify-and-forward relays (could be idle mobiles) which then forward the packets to the destination. Relaying the packets introduces an artificial scattering environment which leads to a high-rank channel matrix. Further information to relay networks are found in [4] and the references therein.

Space-time signal processing is the appropriate technology in MIMO communication systems in order to enhance the system performance (e.g., transmission quality and/or data rate). Space-time coding in particular is a technique which introduces spatial and temporal correlation into signals transmitted from different antennas in order to provide diversity at the receiver. Spatial multiplexing is a technique which exploits the spatial-temporal structure of the transmitted signals in order to increase the data rate.

In this project you will have the opportunity to learn more about the exciting fields of MIMO communications, space-time signal processing and the use of these techniques in wireless relay networks. The goal is to apply and modify existing space-time receivers to relay-assisted wireless MIMO channels.

[1] D. Gesbert and J. Akhtar, "Breaking the barriers of Shannon's capacity: An overview of MIMO wireless systems", Telektronikk Telenor Journal, Jan. 2002.
[2] A. Wittneben and B. Rankov, "Impact of Cooperative Relays on the Capacity of Rank-Deficient MIMO Channels", IST Mobile & Wireless Communications Summit 2003
[3] B. Rankov and A. Wittneben, "On the Capacity of Relay-Assisted Wireless MIMO Channels", SPAWC 2004
[4] M. Gastpar and M. Vetterli, "On the Capacity of Wireless Networks: The Relay Case", IEEE Infocom 2002.

Subject area Wireless relay networks, Space-time codes and MIMO communication systems
Type of work 50% Theory, 50% Software (MATLAB)
Supervisor Dr. Boris Rankov
Professor Prof. Dr. Armin Wittneben