We consider routing problems in ad hoc wireless networks modeled as unit graphs in which nodes are points in the plane and two nodes can communicate if the distance between them is less than some fixed unit. We describe the first distributed algorithms for routing that do not require duplication of packets or memory at the nodes and yet guarantee that a packet is delivered to its destination. These algorithms can be extended to yield algorithms for broadcasting and geocasting that do not require packet duplication. A byproduct of our results is a simple distributed protocol for extracting a planar subgraph of a unit graph. We also present simulation results on the performance of our algorithms.

AbstractÐIn a localized routing algorithm, each node makes forwarding decisions solely based on the position of itself, its neighbors, and its destination. In distance, progress, and direction-based approaches (reported in the literature), when node A wants to send or forward message m to destination node D, it forwards m to its neighbor C which is closest to D (has best progress toward D, whose direction is closest to the direction of D, respectively) among all neighbors of A. The same procedure is repeated until D, if possible, is eventually reached. The algorithms are referred to as GEDIR, MFR, and DIR when a common failure criterion is introduced: The algorithm stops if the best choice for the current node is the node from which the message came. We propose 2-hop GEDIR, DIR, and MFR methods in which node A selects the best candidate node C among its 1-hop and 2-hop neighbors according to the corresponding criterion and forwards m to its best 1-hop neighbor among joint neighbors of A and C. We then propose flooding GEDIR and MFR and hybrid single-path/flooding GEDIR and MFR methods which are the first localized algorithms (other than full flooding) to guarantee the message delivery (in a collision-free environment). We show that the directional routing methods are not loopfree, while the GEDIR and MFR-based methods are inherently loop free. The simulation experiments, with static random graphs, show that GEDIR and MFR have similar success rates, which is low for low degree graphs and high for high degree ones. When successful, their hop counts are near the performance of the shortest path algorithm. Hybrid single-path/flooding GEDIR and MFR methods have low communication overheads. The results are also confirmed by experiments with moving nodes and MAC layer. Index TermsÐRouting, wireless networks, distributed algorithms, shortest path, broadcasting 1

Recent availability of small inexpensive low power GPS receivers and techniques for finding relative coordinates based on signal strengths, and the need for the design of power efficient and scalable networks, provided justification for applying position based routing methods in ad hoc networks. A number of such algorithms were developed in last few years, in addition to few basic methods proposed about fifteen years ago. This article surveys known routing methods, and provides their taxonomy in terms of a number of characteristics: loop-free behavior, distributed operation (localized, global or zonal), path strategy (single path, multi-path or flooding based), metrics used (hop count, power or cost), memorization (memoryless or memorizing past traffic), guaranteed delivery, scalability, and robustness (strategies to handle the position deviation due to the dynamicity of the network). We also briefly discuss relevant issues such as physical requirements, experimental design, location updates, QoS, congestion, scheduling node activity, topology construction, broadcasting and network capacity.

In recent years, several position-based routing protocols have been developed for mobile ad hoc networks. Many of these protocols assume a location service is available that provides location information on the nodes in the network. In this chapter, we survey all the proposed location information services that exist in the literature to date. We classify these location information services into three categories: proactive location database systems, proactive location dissemination systems, and reactive location systems.

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) wire...

All previously proposed position based routing algorithms for wireless ad hoc networks were based on forwarding the actual message along multiple paths toward an area where destination is hopefully located. The significant communication overhead can be avoided if the routing strategy is changed. We propose that the source node issues several search 'tickets' (each ticket is a 'short' message containing sender's id and location, destination's best known location and time that location is reported, and constant amount of additional information) that will look for the exact position of destination node. When the first ticket arrives at the destination node D, D will report back to source with brief message containing its exact location, and possibly creating a route for the source. The source node then sends full data message ('long' message) toward exact location of destination. We then propose a quorum based location update scheme, in which nodes report their new positions to their neig...

Most previously proposed position based routing algorithms for wireless ad hoc networks were based on forwarding the actual message along multiple paths toward an area where destination is hopefully located. The significant communication overhead can be avoided if the routing strategy is changed. We first propose to apply a variant of well-known route discovery scheme. The source node issues several search 'tickets' (each ticket is a 'short' message containing sender's id and location, destination's best known location and time that location is reported, and constant amount of additional information) that will look for the exact position of destination node. When the first ticket arrives at the destination node D, D will report back to source with brief message containing its exact location, and possibly creating a route for the source. The source node then sends full data message ('long' message) toward exact location of destination. We then propose a quorum based location update scheme, in which nodes report their new positions to their neighbors whenever a link is broken or created. After certain number of such link changes, nodes forward their new position to all nodes located in its `column', that is, to the north and south of their current location with certain 'thickness' of reporting. The destination search then begins with two tickets being sent in the east and west direction, with certain 'thickness', looking for the most up to date information of destination's position. When the tickets reach each end of current 'row', the search is continued toward best reported destination position, with corrections along the path as better information becomes available closer to destination. One of tickets can be sent from the source directly toward destination, to take ad...

This chapter reviews research on routing in ad hoc and sensor wireless networks in the view of node mobility, changes in node activity, and availability of methods to determine absolute or relative coordinates of each node. Various approaches in literature are classified according to some criteria. Mobility is apparently a very difficult problem to handle in ad hoc networks, and all proposed solutions have significant drawbacks. Additional problems arise with `sleep' period operation, that is changes in node's activity status with or without mobility. While significant progress has been made on the routing with known destination location, location updates issue to enable efficient routing requires further investigation.

This thesis proposes the use of a new routing paradigm to enable communication in highly mobile, ad hoc networks, which operate wirelessly in the absence of dedicated master stations or fixed infrastructure. Due to the mobility of the nodes, the network topology changes frequently and unpredictably. We explore the new routing paradigm in the context of inter-vehicle communication. In such highly mobile ad hoc networks, the nodes commonly do not know the identity of their communication partners in advance. Rapid topology changes and scarce bandwidth prevent the nodes from exchanging updates regularly throughout the network. Therefore, we advocate a new routing paradigm that implicitly addresses message destinations based on the current situation of the network. [...]

We present an approach to multicast messages among highly mobile hosts in ad hoc networks. We suggest a new definition of a multicast that suits the special needs of inter-vehicle communication: rather than explicit identification, a multicast group is defined implicitly by location, speed, driving direction and time. As an example, we study a road accident that is reported to nearby vehicles. We focus on sparse deployment of the system which is likely to occur soon after the system is introduced to the market. In this state, the resulting ad hoc network tends to be disconnected. We tailor the proposed algorithm to overcome this problem of network fragmentation. Simulations show us the quality of the proposed protocol by measuring how many vehicles inside a multicast area are informed in time under various conditions. Index Terms: Inter-vehicle communication, mobile ad hoc network, multicast, global positioning system. I.