On rate control of packet transmission over fading channels

In error controlled packet reception, a packet is received only if its error probability can be kept below a predetermined level. Error probability control is achieved by posing a minimum signal to noise ratio (SNR) threshold with corresponding packet internal coding scheme, which upper-bounds the packet data rate. We first consider packet transmission over a single-user wireless fading channel with additive Gaussian noise. We derive the optimal SNR threshold that maximizes the communication throughput. We show under a set of generous conditions that the optimal SNR threshold in the low-SNR regime is proportional to the transmit power; the ratio depends neither on the packet internal coding scheme nor on the pre-determined error probability level. The result is then extended to packet multicasting where common information is transmitted to a group of receivers over fading channels.