A scalable code dissemination protocol in heterogeneous wireless sensor networks

Code dissemination is currently a major research issue in wireless sensor networks (WSNs).Many studies focus on code dissemination in homogeneous WSNs,mainly using a broadcast approach to solve this problem;few studies on code dissemination in heterogeneous WSNs.Furthermore,broadcasting cannot readily be used to solve the heterogenous WSN code dissemination problem directly,which is where we have focused our attention.We transformed this problem into a minimum non-leaf nodes (MNN) Steiner tree problem.We designed a scalable multicast protocol,named Heterogeneous Sensor Networks Scalable Reprogramming Protocol (HSR) to solve the MNN problem.HSR can build different multicast trees according to different nodes or code modules to disseminate different codes to them.HSR is able to approximate the MNN tree problem to a ratio of ln|R| (R is the set of all destinations) best known lowest bound.Therefore,the communication cost is significantly decreased and the total energy required by WSNs is reduced.We further designed two scalable schemes,special routing log and hops-restricted local broadcast,which compress the multicast tree information and deliver the multicast messages without loss.We also designed a 3-stage pipeline to speed up the transmission of packets,which alleviated interference and hidden terminal issues.We evaluated our design through comprehensive simulations and prototype implementations on Mica2 motes.Experimental results demonstrate that HSR outperforms previous protocols including the most recent studies on Sprinkler and uCast.