The sound of silence: Guessing games for saving energy in a mobile environment

This paper explores efficient discrete coding techniques that are motivated by the time-energy trade-off in message transmissions between mobile hosts and mobile support stations. Three algorithms are suggested, two of which use guessing games in which the mobile support station guesses the message to be transmitted by the mobile host and receives an approving signal for a successful guess from the mobile host. The first algorithm is designed to achieve the smallest expected amount of energy while obeying a time bound for message transmissions. The second algorithm achieves the shortest expected transmission time while obeying a bound on the energy. This algorithm uses dynamic programming to construct an optimal tree for the guessing game. Our third algorithm uses a different approach based on the Lempel-Ziv compression algorithm. The time-energy trade-off is controlled by the choice of the length of the codes used to encode strings in the dictionary. The theoretical results obtained are not tied to mobile computing and are of independent interest.