Adaptive blind spatial processing for frequency diversity spread spectrum communications
Miguel Angel Lagunas, Ana I. Pérez-Neira, Moeness G. Amin · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1999
Frequency Diversity Spread Spectrum (FDSS) systems have been evolved as a valuable alternative to traditional direct sequence and frequency hopping systems to combat partial band jamming. In FDSS system, the communication frequency band is partitioned into N disjoint subbands on which N replicas of the signal are simultaneously transmitted. The objective is not to erase the signal replicas hit by the jammer, but rather erase the jammer from the replicas. This work describes the use of beamforming to process the spatial diversity for optimum symbol by symbol detection. The procedure is adaptive and suitable for time varying environments. The beamformer corresponding to each frequency diversity component is updated using a gradient algorithm. This algorithm incorporates automatic gain control and is derived based on the fact that the desired signal is present in every frequency component. The optimum detector for FDSS is described and shown to be fully compatible with spatial processing techniques.