MIMO Nullforming with RVQ Limited Feedback and Channel Estimation Errors

This paper explores limited feedback nullforming techniques based on random vector quantization (RVQ) with and without receiver coordination. The availability of receiver coordination affects the type and amount of feedback required to select an appropriate precoding vector. Approximate upper and lower bounds are developed for the mean received power at primary receivers with and without receiver coordination. Numerical results confirm the analysis and show that the channel estimation errors effectively establish a floor on the achievable performance of RVQ nullforming. The size of the RVQ codebook can be selected to approach this floor without excessive overhead.