Master Thesis - 2008

In recent years, wireless multihop network is attracting attention as a fundamental technology to realize ubiquitous communication environment. It is expected to make life more convenient widely and is attracting attention as alternative means when wired infrastructure is disrupted. Thus, it is desired to increase.

The primary channel access method in wireless network is IEEE 802.11 DCF (Distributed Coordination Function). In DCF, wireless nodes need to wait for backoff interval to acquire the right to access the wireless channel. Therefore, throughput decreases.

As a solution of this problem, IEEE 802.11e defines burst transfer. In burst transfer, nodes can send multiple packets without waiting for backoff interval once nodes get the right to access wireless channel. However, burst duration, for which nodes can send packets per one channel access right, has no mechanisms to adapt to the condition of adjacent nodes. As a result, load concentration on a particular node causes buffer overflow, and throughput decreases. Moreover, when a particular node occupies channel resources for a long time, the throughput fairness between nodes decreases.

In this paper, we propose burst transfer scheduling method that improves throughput and its fairness. In this method, nodes take hold on the load condition of adjacent nodes by exchanging control information. And time limit is set in a certain period and numerical targets of transferring packets until the limit is set. The target is decided to adapt condition of load which receiver nodes have. Moreover, communication executes to realize the target efficiently with change of burst duration adapting condition. This scheduling is expected to improve the fairness between each nodes and network throughput. Moreover, we show the effectiveness of our proposal by computer simulation.