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Abstract-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 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 will die much more quickly than those close to the s ink. 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.

No abstract

In multi-hop wireless sensor networks that are characterized by many-to-one (converge-cast)

Abstract-As wireless sensor networks continue to attract more attention, new ideas for applications are continually being developed, many of which involve consistent coverage of a given surveillance area. Recently, several protocols and architectures have been proposed to maintain network connectivity and adequate coverage quality while minimizing the drain on the scarce energy resources of the sensor nodes. In this paper, we propose DAPR, an integrated protocol for routing and coverage preservation that is distinctly different from the previously proposed solutions. Guided by the intuition that certain sensors are more important to the sensing application than others because of limited neighborhood redundancy, we introduce a new routing metric -an "application cost" -that aims to avoid the use of sensors in areas of critically sparse sensor deployment as routers. We have implemented DAPR in the ns-2 simulator and present simulation results showing the effectiveness of the protocol in extending network lifetime.