A game-theoretic approach to power management in MIMO-OFDM ad hoc networks

With the increasing demand for wireless services, the efficient use of spectral resources is of great importance. MIMO-OFDM communication systems hold great promise in using radio spectrum efficiently while power control will improve energy efficiency. Existing approaches such as multiuser water-filling and gradient projection assign a fixed transmit power to each link and each transmitter node allocates power among different antennas in order to optimize the link capacity or sum data rate. If bad channel conditions exist in some communicating links, these methods are not energy efficient.; We propose a new technique for power management and interference reduction based upon a game theoretic approach. Utility functions are designed and power allocation in each link is built into a non-cooperative game. To avoid unnecessary power transmission under poor channel conditions, a mechanism of shutting down inefficient links is integrated into the game theoretic approach. Two kinds of link shut-down mechanism are presented in this dissertation. The first one is called hard shut-down, because once the transmit node decides to shut down, the node will not resume transmission no matter how the interfering channels change. The other mechanism is called soft shut-down, in which the transmit power is related to the pricing factor of that link and the interference it is exposed to. With this mechanism, the transmit power can change adaptively in response to the condition of interference.; We also investigate the problem of subcarrier assignment and power distribution among multiple antennas for point-to-point links in a network without base stations. A subcarrier assignment scheme is proposed which selects a set of subcarriers for each link so that high data rate can be achieved and co-channel interference can be mitigated. The power management in a MIMO-OFDM ad hoc network is also built into a non-cooperative game in which each link calculates its optimal power allocation vector in order to maximize the net utility. The designed utility function facilitates subcarrier assignment schemes by using a tunable pricing factor, which helps a link to admit or drop subcarriers in a soft and adaptive fashion.