On the problem of unbalanced load distribution in wireless sensor networks

In multi-hop wireless sensor networks that are characterized by many-to-one traffic patterns, problems related to energy imbalance among sensors often appear. When each node has a fixed transmission range, the amount of traffic that the sensor nodes are required to forward increases dramatically as the distance to the data sink becomes smaller. Thus, sensors closest to the data sink tend to die early, leaving areas of the network completely unmonitored and causing network partitions. Alternatively, if all sensors transmit directly to the data sink, the furthest nodes from the data sink dies much more quickly than those close to the sink. While it may seem that network lifetime could be improved by use of a more intelligent transmission power control policy that balances the energy used in each node by requiring nodes further from the data sink to transmit over longer distances (although not directly to the data sink), such a policy can only have a limited effect. In fact, this energy balancing can be achieved only at the expense of gross energy inefficiencies. In this paper, we investigate the transmission range distribution optimization problem and show where these inefficiencies exist when trying to maximize the lifetime of many-to-one wireless sensor networks.