Wintersemester 03/04

Impact of Cooperative Relays on Low-Rank 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 at 17GHz) the scattering will be low and the resulting channel matrix rank deficient. In a recent work [2] we have shown that wireless relay networks [3] 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.

In this project you will study different channel models (log-normal shadowing, ray-tracing, spatial scatterer models) and investigate their impact on the outage and average channel capacity of the relay assisted MIMO link. A further goal is to find appropriate gain allocation schemes for the amplify-and-forward relays.

[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] M. Gastpar and M. Vetterli, "On the Capacity of Wireless Networks: The Relay Case", IEEE Infocom 2002.

Subject area Capacity of wireless relay networks, MIMO communication systems
Type of work 50% Theory, 50% Software (Matlab)
Student Phillip Schaller, Konstantin Zurbriggen
Supervisor Dr. Boris Rankov, Dr. Ingmar Hammerström
Professor Prof. Dr. Armin Wittneben