On capacity of a class of acoustic channels

We use a per-path Rician fading model to analyze the capacity of acoustic channels, and provide experimental data to confirm the practicality of simulation results. Three power allocation policies are considered: water-filling, uniform power allocation across selected, channel-favored frequencies (“on-off” carriers in an OFDM system), and uniform power allocation across all carriers irrespective of the channel (“all-on”). The impact of channel estimation errors and feedback delay is taken into account. The three policies are found to differ little in terms of the achievable rate, and to suffer similar loss from imperfect channel knowledge at the receiver (about 1 bps/Hz loss from 4 bps/Hz at 20 dB for the experimental channel). Unlike water-filling and on-off power allocation, which are additionally sensitive to outdated channel feedback, all-on uniform power allocation does not require feedback and is simple to implement, thus emerging as a justified practical solution.