A binaural hearing aid set-up where the left and right ear devices are connected by a rate-constrained wireless link is considered, and the performance gain resulting from beamforming is quantified. Each device is assumed to have two or more microphones. The transmitting device sends a signal at a rate R to the receiving device where it is combined with the locally available signals to obtain a minimum mean-squared error estimate of the desired signal. Different practically realizable choices for the signal to be transmitted are considered: an estimate of the desired signal, an estimate of the interfering signal (relevant for multi-microphone interference cancellation), and the unprocessed signal. It is not obvious which scheme provides the best rate-gain trade-off. In fact, it is shown that this varies depending on the configuration of the desired and interfering sources. This paper provides a framework to quantify and thus compare the performance of the above-mentioned schemes in terms of the rate R and the resulting beamforming gain.
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