Power control for wireless streaming with HOL packet deadlines

We consider the problem of streaming media packets from a transmitter buffer to a receiver over a wireless channel, controlling the transmitter power. When each packet comes to the head-of-line (HOL) in the buffer, it is a given a deadline D, which is the maximum number of times it can attempt retransmission in order to get successfully transmitted to the receiver. If that fails to happen, the packet is dropped and the next in line packet becomes the HOL one. Cost is incurred in each time slot for keeping packets in the transmitter buffer, transmitting power, and dropping HOL packets exceeding their deadlines. We investigate how transmission power should be chosen efficiently given the remaining backlog and residual transmission attempts of the HOL packet, so as to minimize the overall cost to transmit the buffer content. We formulate the optimal power control problem and study properties of the optimal control, proving that it is monotone under certain conditions. We then develop an approximate power control, which increases logarithmically in the transmitter backlog, and is demonstrated to perform quite closely to the optimal one.