Improving the efficiency of wireless networks via a passive rate-adaptation strategy

A simple receiver-oriented rate-adaptation strategy is proposed for improving the throughput of mobile ad-hoc networks (MANETs) while transmitting multimedia data. The quality of a randomly fluctuating wireless link is maintained at a desired level by multiplexing and mapping different traffic sources that require unequal error protection into a multiresolution (multicast) modulation and dropping the "less important" bits (i.e., passive rate reduction) when the channel condition deteriorates. The throughput (effective data rate) is increased by not discarding the correctly received bits within the noisy received symbols with a high probability (i.e., by adaptively selecting appropriate decision regions for each symbol demodulation based on the channel quality estimate available at the receiver). The salient feature of our rate-adaptation scheme relies on the fact that it does not require any feedback of channel quality estimates from the receiver to the sender, and our improvements are achieved without adaptively altering the signal constellation size at the transmitter according to the link quality or by using error control coding with incremental redundancy. Moreover, it can still be very effective even in fast fading channels (i.e., high Dopplerfrequency).