Depth First Search and Location Based Localized Routing and QoS Routing in Wireless Networks

In a localized routing algorithm, node A currently holding the message forwards it to one or few neighbors based on the location of itself, its neighboring nodes and destination. Several localized routing algorithms for wireless networks were described recently, based on location information of nodes available via Global Positioning System (GPS). The quality-of-service (QoS) routing (routing with delay and bandwidth constraints) in wireless networks is difficult because the network topology may change constantly, and all existing solutions are non-localized. We propose to use depth first search (DFS) method for routing decisions. Each node A, upon receiving the message for the first time, sorts all its neighbors according to a criteria, such as their distance to destination, and uses that order in DFS algorithm. The algorithm requires to memorize some of the past traffic at each node (as enforced by DFS). It is the first localized algorithm that guarantees delivery for (connected) wireless networks modeled by arbitrary graphs (e.g. minpower graphs). Moreover, it guarantees delivery regardless of the amount of error in recorded position of destination (including different information at different nodes). We then propose the first localized QoS routing algorithm for wireless networks. It performs DFS routing algorithm after edges with insufficient bandwidth or insufficient connection time are deleted from the graph, and attempts to minimize hop count (which approximates propagation delay requirement). This is also the first paper to apply GPS in QoS routing decisions, and to consider the connection time (estimated lifetime of a link between two moving nodes) as a QoS criterion. The performance of DFS based routing algorithm, with distance as criteria for selecting neighbors, is compared with performance of shortest path (SP) algorithm. QoS routing algorithm based on DFS is shown to produce paths whose hop counts are very close to hop counts of SP algorithm, with reasonable setup overhead (when destination information is accurate). The average length of measured QoS path in our experiments, obtained by DFS method, was between 1 and 1.34 times longer than the length of QoS path obtained by SP algorithm. The overhead of DFS routing (which comes from returned or rejected messages) is considerably reduced by applying the concept of intermediate, inter-gateway, and gateway nodes, and their enhancement using a shortest path requirement. The distance of neighboring nodes may be replaced by progress, direction, estimated transmission power, or quality of service (delay, bandwidth) criteria in routing decisions, as further applications of DFS based localized routing algorithm with guaranteed success.