JultikaUniversity of Oulu repository

Congestion in wireless sensor networks (WSNs) has always been a serious problem for all kinds of communication networks. It causes severe information loss and shortens the life time of the sensor nodes. Congestion also leads to excessive energy consumption due to large number of retransmission and packet loss which lowers throughput. In WSNs congestion need to be controlled in order to have high energy-efficiency, to prolong system life time, improve fairness and improve quality-of-service in terms of packet loss ratio with the packet delay and link utilization. Most of the designs of WSN depend on the applications and the environment in which the sensor nodes are deployed. It has important applications such as remote environment monitoring, target tracking, military and surveillance, etc. The placement of the nodes is often done randomly or in a pre-planned manner. These sensors are equipped with wireless interfaces with which they can communicate with one another to form a network. WSNs can be an event driven which can be routed to detect or monitor data at the base station depending on their degree of priority since the data in the sensor networks has different importance. WSNs face challenges in dealing with the issues of congestion due to their constraint nature and complex algorithms. During the last decade, the tremendous congestion control algorithms and schemes have been proposed to solve the issue of congestion by ensuring fair delivery of packets to the base station. This thesis explores the different congestion detection algorithms and schemes, which are especially targeted for the WSNs and presents a survey of congestion control mechanisms used in WSNs. In addition, the study in this thesis would find out the common features which may help in the future research.