Study On Geographic Routing Protocol For Wireless Sensor Networks

In Wireless Sensor Network(WSN), a large number of low-cost, low-power, limited processing capability and energy resource constrained micro sensor nodes, which form a wireless multi-hop ad hoc network, will collaborate for sensing, gathering, processing and transmitting information of sensed object in network coverage area, and then these information are being sent to sink. Since the capability of nodes is limited and the sizes of networks are usually huge, the protocols of WSN must be well scaled rather than complicated.The simplicity and scalability of geographic routing make it become an attractive routing scheme for WSN. However, geographic routing also has some drawbacks, such as high latency and high collision. This paper respectively proposes two geographic routing protocols in order to reduce latency and probability of collision. One is Hybrid Beaconless Geographic Routing(HBGR), the other is Sector based/Spherical-cone based Forwarding Area Division and Adaptive Forwarding Area Selection(FADS).Based on different requirement of application on latency, we divide the packets of WSN into delay sensitive packets and normal packets. The goal of HBGR is to accelerate the delivery of delay sensitive packets with little impact on normal packets. HBGR achieves its goal from the following respects:1) HBGR uses hybrid RTS/CTS(Request-To-Send/Clear-To-Send) handshaking mechanism to provide different transmission services for different kinds of packets, which ensure delay sensitive packets could continue occupying the channel when they have obtained the channel, and thus guarantee the fast delivery of delay sensitive packets.2) With respect to channel contention, HBGR assigns different contention windows(CW) to two kinds of packets, which ensures delay sensitive packets are prior to normal packets.3) HBGR also introduces distance-based forwarding area division scheme in order to optimize the forwarder selection. It makes sure that candidate forwarders, which are closer to the Sink, have higher opportunity to be selected as forwarder.Compared with GF, OGF and AODV under different levels of congestion in stationary and mobility scenario, the simulation results exhibit the superior performance of HBGR in terms of packet delivery ratio, End-to-End latency, and energy consumption per packet.For the sake of reducing collision, we start with CTS collision. We firstly study the reasons of CTS collision, and then classify it into same-slot collision and distinct-slot collision. The aims of FADS are to avoid distinct-slot collision, reduce the probability of same-slot collision, and realize dynamic load balancing. FADS achieves its goals from the following respects:1) Based on the characteristic of forwarding area in 2D plane and 3D space, FADS respectively proposes Sector based forwarding area division and Spherical-cone based forwarding area division. Forwarding area division ensures that every node within the same subarea is capable of hearing one another, thus avoiding distinct-slot collision.2) Since forwarder is only searched within target-subarea which is one of sender's forwarding subarea, the number of candidate forwarders which actually participate in forwarder contention is decreased, and hence the probability of same-slot collision is reduced.3) Based on the transmitting condition of each subarea, the adaptive forwarding area selection of FADS realizes dynamic load balancing by adjusting the probability of subareas which be selected as target-subarea.Compared with related protocols(GF, IGF and OGF), no matter in the 2D scenario or in the 3D scenario, simulation results show the excellent performance of FADS in terms of packet delivery ratio, End-to-End latency, and energy consumption per packet, especially in dense networks and congested networks.