Transmission power control for enhancing the performance of wireless packet data networks

This thesis presents several techniques that enhance the performance of wireless mobile devices that communicate without depending on a supporting infrastructure. These networks are commonly referred to as ad hoc networks since they operate in highly dynamic environments and, therefore, must utilize available resources.; The primary focus of this thesis is on improving the performance of ad hoc networks by controlling the transmission power to maximize the spectral reuse (capacity) and minimize energy consumption. This work starts by looking at single-hop ad hoc networks, but then extends this to multihop wireless ad hoc networks to investigate additional energy savings and capacity improvements. It is shown that the capacity of multihop data flows depends heavily on the shaping of the traffic at intermediate hops. Therefore, transport layer enhancements are also defined that adapt how nodes handle the data flows based on local environmental conditions (contention, congestion, and routing overhead).; Multiple access-based collision avoidance MAC protocols have typically used fixed transmission power and have not considered power control mechanisms based on the distance of the transmitter and receiver in order to improve spatial channel reuse. This work proposes power control multiple access (PCMA) a wireless MAC protocol within the collision avoidance framework. PCMA generalizes the transmit-or-defer “on/off” collision avoidance model of current protocols to a more flexible “variable bounded power” collision suppression model. Our simulation results show that the PCMA protocol can improve the throughput performance of the non-power-controlled IEEE 802.11 protocol by a factor of 2 and provide a 50% average transmission power reduction.; The enhancements at the transport layer demonstrate that by implementing hop-by-hop control of data flows instead of end-to-end flow control the intermediate node flow rates can be adapted more quickly to changes in the local environment for optimum performance. Fast adaptation is particularly important in ad hoc networks where link states and contention can change on the order of a second or less.; The power control and hop-by-hop protocol frameworks presented in this thesis demonstrate the potential for significant improvements in the wireless ad hoc environment thereby, motivating their incorporation into future working drafts and standards.