Optimized Distributed Space-Time Filtering

Distributed space-time filtering (DSTF) facilitates node cooperation and achieves a diversity gain while not requiring node coordination, i.e., cooperating nodes do not have to be aware of their partners. This makes DSTF attractive for application in future sensor, ad hoc, and wireless networks. In this paper, we derive a novel cost function and related practical algorithms for optimization of the signature filter vectors (SFVs) used in DSTF. We extend DSTF to frequency-selective fading channels and compare its performance with that of delay diversity transmission with co-located antennas. For the special case of frequency-nonselective channels we show that SFV optimization is closely related to the signature sequence design for code-division multiple access (CDMA) systems and the design of Grassmannian frames. Numerical and simulation results show that the novel SFV designs perform significantly better than previously proposed designs even if non-ideal effects such as suboptimum equalization, imperfect channel estimation, and imperfect timing synchronization are taken into account