Hardware Assisted Compression in Wireless Sensor Networks

A wireless sensor network (WSN) is comprised of resource constrained devices called motes. Motes are battery operated and must conserve as much power as possible. Power usage for each mote is made up of processing data, sensing the surroundings, and sending and receiving packets. The bulk of power usage for standard WSN applications lies in the radio where receiving and sending packets are necessary to communicate to a base station (as much as 80%) [5]. This communication is generally greater than the range of any single mote, and thus multi-hop routing must take place. The multi-hop routing furthers the need for reduction of packets because each additional hop adds to the amount of traffic generated. By compressing sense data, which each mote collects, the number of packets can be reduced. Only lossless compression is taken into consideration. This paper proposes a solution to reduce the consumption of power using reconfigurable hardware specially programmed to do low power compression. A mote would offload bulk data to a hardware attachment and receive the compressed version of the data. The compressed data can be stored in flash or sent over the network to the sink node. Additional work will go into the trade-off factor between compression to non-compression. Compression should only occur if the amount of power taken to compress X amount of bytes and transfer Y amount of bytes is less than just transferring X amount of bytes. Moreover, seeing the gains from doing offloading of compression versus doing it onchip must be taken into consideration as well. Additional hardware is not free, so cost for the power savings plays a factor in deciding how compression takes place. Moreover, there are also limitations based on the kind of reconfigurable hardware. This paper addresses these issues.