Ibrahim A. Shah
University of Kassel
Dept. of Electrical Engineering / Computer Science, Room 2324 C
Wilhelmshöher Allee 73, D-34121 Kassel
+49 (0)561 804 6556 (Secretary)
+49 (0)561 804 6008
The last decade has seen considerable research interest in cooperative wireless communication techniques which exploit cooperative diversity without the need of having multiple antennas at each node. One such technique is distributed beamforming (DB) having the potential to improve communication reliability. One form of distributed beamforming, the so-called distributed transmit beamforming (DTB), is a form of cooperative communications in which a network of multiple transceivers cooperate to transmit a common message coherently to a destination. DTB can provide energy efficiency and reasonable directional gain for adhoc sensor networks. Another form of DB is the distributed relay beamforming (DRB), in which a set of cooperating nodes act as a virtual antenna array and adjust their transmission weights to form a coherent beam to the destination. This can result in diversity gains similar to those of multiple-antenna systems.
We are currently investigating the following aspects in DB:
1) The adjustment of transmission weights to form coherent beams requires the knowledge of channel state information (CSI). A feedback channel is usually used to send the CSI estimates from the destination to the cooperating nodes. Since the capacity of this feedback channel is limited, there would be an effect on the overall performance.
2) It would be desirable to use only those relays that contribute to a high SNR at the receiver. Policies for selective relaying have to be designed.
3) Since any wireless system would inevitably suffer from interference, DB procedures have to be designed to mitigate the interference.