Analysis of Capacity for Spatial TDMA in Wireless Ad Hoc Networks with Variable Power and Rate Control

Ad hoc wireless is a promising technology for realizing the vision of ubiquitous communications. A major design issue in such networks is the formulation of the medium access control (MAC) protocols. Spatial TDMA (STDMA) is a "conflict-free" MAC protocol, thus enabling high spectral utilization, however scheduling is required. In link-oriented STDMA, the schedule specifies when particular radio links will be activated. In most wireless networks simultaneous link activation or "reuse" is possible. An efficient schedule is critical to network performance. This paper investigates how to use variable transmitter power and variable data rates in ad hoc STDMA networks and the possible gain in throughput. The use of transmitter power control and multiple-rate selection enables the network to adapt to changes in the environment, which is crucial for the ability to guarantee quality of service (QoS) in a wireless network. We study the impact of the routing metric and traffic adaptability (bottleneck links in the network are assigned more slot than other nodes in the schedule) on the network's ability to utilize multirate power control. The results show that it is of paramount importance to take both transmitter power and a variable data rate into the STDMA protocol design