Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Different CSMA variants (Carrier Sense Multiple Access), such as the widely spread WLAN-standards IEEE 802.11, are often suggested as MAC-protocols in ad hoc networks. Many of the problems that a CSMA-system suffers in a one-hop network are aggravated in a multi-hop network. This makes CSMAschemes less attractive to use in ad hoc networks. Several methods of scheduling transmissions in TDMA and in its more evolved form STDMA (Spatial reuse TDMA) have proved to give a higher maximum throughput than CSMA. TSST (Traffic Sensitive Scheduled TDMA) is proposed in this work, it is a novel algorithm for scheduling transmissions.
TSST makes schedules based on the estimated queue length in every node.
It is assumed that reports of queue lengths cannot instantaneously propagate from node to node. The updates will be received with a fixed delay (lag). Using this lagged information with support of traffic estimates and the knowledge of previous send schedules, TSST is capable of estimate the current queue lengths.
The results show that TSST can achieve higher throughput than CSMA. The results also show that TSST can achieve lower end to end delay than idealised forms of prior TDMA-schemes, even if it has to estimate the queue lengths with quite old information and inaccurate traffic estimates.
It is concluded that TSST is an efficient way of scheduling for TDMA and that the accuracy of the traffic estimator is of great importance.
2005. , 46 p.