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...nt part of the available bandwidth if the topology of the network changes frequently [5]. In response to this observation, reactive routing protocols were developed (e.g., DSR [6], TORA [7], and AODV =-=[8]-=-). Reactive routing protocols maintain only the routes that are currently in use, thereby reducing the burden on the network when only a small subset of all available routes is in use at any time. How...

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...s proposed not to forward packets that have reached a local maximum at all [26]. The face-2 algorithm [29] and the perimeter routing strategy of the Greedy Perimeter Stateless Routing Protocol (GPSR) =-=[30, 31]-=- are two very similar recovery approaches based on planar graph traversal. Both are performed on a per-packet basis and do not require nodes to store any additional information. A packet enters the re...

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...k paths that are currently in use, limiting the amount of topological changes that can be tolerated within a given amount of time. A survey and comparison of topology-based approaches can be found in =-=[10, 11]-=-. In the following we will focus exclusively on position-based routing. Position-based routing algorithms eliminate some of the limitations of topology-based routing by using additional information. T...

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...py a significant part of the available bandwidth if the topology of the network changes frequently [5]. In response to this observation, reactive routing protocols were developed (e.g., DSR [6], TORA =-=[7]-=-, and AODV [8]). Reactive routing protocols maintain only the routes that are currently in use, thereby reducing the burden on the network when only a small subset of all available routes is in use at...

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...p neighbor in the required direction, a recovery procedure has to be started. This procedure is not part of the DREAM specification. Location Aided Routing (LAR) — The Location Aided Routing proposal =-=[33]-=- does not define a location-based routing protocol but instead proposes the use of position information to enhance the route discovery phase of reactive ad hoc routing approaches. Reactive ad hoc rout...

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...uitive strategy is to forward the packet to the node that makes the most progress towards (is closest to) D. In the example this would be node C. This strategy is known as most forward within r (MFR) =-=[25]-=-; it tries to minimize the number of hops a packet has to traverse in order to reach D. MFR is a good strategy in scenarios where the sender of a packet cannot adapt the signal strength of the transmi...

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...rm packet forwarding. They can be further divided into proactive, reactive, and hybrid approaches. Proactive algorithms employ classical routing strategies such as distance-vector routing (e.g., DSDV =-=[2]-=-) or link-state routing (e.g., OLSR [3] and TBRPF [4]). They maintain routing information about the available paths in the network even if these paths are not currently used. The main drawback of thes...

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...rwarded from a to b, is higher for NFP than for MFR. Another strategy for forwarding packets is compass routing, which selects the neighbor closest to the straight line between sender and destination =-=[27]-=-. In the example this would be node B. Compass routing tries to minimize the spatial distance a packet travels. Finally, it is possible to let the sender randomly choose one of the nodes closer to the...

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...the topology of the network changes frequently. Finally, packets en route to the destination are likely to be lost if the route to the destination changes. Hybrid ad hoc routing protocols such as ZRP =-=[9]-=- combine local proactive routing and global reactive routing in order to achieve a higher level of efficiency and scalability. However, even a combination of both strategies still needs to maintain at...

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...7, where the transmission range of each node contains all other nodes). In order to construct a connected planar subgraph of the graph formed by the nodes in the ad hoc network, a wellknown mechanism =-=[32]-=- is employed: an edge between two nodes A and B is included in the graph only if the intersection of the two circles with radii equal to the distance between A and B around those two nodes does not co...

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...rse in order to reach D. MFR is a good strategy in scenarios where the sender of a packet cannot adapt the signal strength of the transmission to the distance between sender and receiver. However, in =-=[26]-=- it is shown that a different strategy performs better than MFR in situations where the sender can adapt its signal strength. In nearest with forward progress (NFP), the packet is transmitted to the n...

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...ables up to date. As a further advantage, position-based routing supports the delivery of packets to all nodes in a given geographic region in a natural way. This type of service is called geocasting =-=[15]-=-. 30 0890-8044/01/$10.00 © 2001 IEEE IEEE Network • November/December 2001Location service Some-for-some Some-for-all All-for-some All-for-all In this article we present a survey of position-based ro...

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...otentially different subset. When these subsets are designed such that their intersection is nonempty, it is ensured that an up-to-date version of the sought-after information can always be found. In =-=[18]-=-, this scheme is used to develop a location service for ad hoc networks. We will discuss it by means of the simple sample network shown in Fig. 3. A subset of all mobile nodes is chosen to host positi...

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...k paths that are currently in use, limiting the amount of topological changes that can be tolerated within a given amount of time. A survey and comparison of topology-based approaches can be found in =-=[10, 11]-=-. In the following we will focus exclusively on position-based routing. Position-based routing algorithms eliminate some of the limitations of topology-based routing by using additional information. T...

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...s proposed not to forward packets that have reached a local maximum at all [26]. The face-2 algorithm [29] and the perimeter routing strategy of the Greedy Perimeter Stateless Routing Protocol (GPSR) =-=[30, 31]-=- are two very similar recovery approaches based on planar graph traversal. Both are performed on a per-packet basis and do not require nodes to store any additional information. A packet enters the re...

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...to minimize the spatial distance a packet travels. Finally, it is possible to let the sender randomly choose one of the nodes closer to the destination than itself and forward the packet to that node =-=[28]-=-. This strategy minimizes the accuracy of information needed about the position of the neighbors and reduces the number of operations required to forward a packet. Unfortunately, greedy routing may fa...

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... participating nodes be available. Commonly, each node determines its own position through the use of GPS or some other type of positioning service [12, 13], a survey of these methods can be found in =-=[14]-=-. A location service is used by the sender of a packet to determine the position of the destination and to include it in the packet’s destination address. The routing decision at each node is then bas...

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...S requires that all nodes store the information on some other nodes, it can be classified as an all-for-some approach. Homezone Two almost identical location services have been proposed independently =-=[23, 24]-=-. Both use the concept of a virtual Homezone where position information for a node is stored. The position C of the Homezone for a node can be derived by applying a well-known hash function to the nod...

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...S requires that all nodes store the information on some other nodes, it can be classified as an all-for-some approach. Homezone Two almost identical location services have been proposed independently =-=[23, 24]-=-. Both use the concept of a virtual Homezone where position information for a node is stored. The position C of the Homezone for a node can be derived by applying a well-known hash function to the nod...

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...ically work as a somefor-some scheme with the backbone being a small subset of all available nodes and a quorum being a small subset of the backbone nodes. Other work based on quorums is presented in =-=[19]-=-. Here, position information for the nodes is propagated in a northsouth direction. Whenever a node whose position is unknown has to be contacted, position information is searched in eastwest directio...

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...er divided into proactive, reactive, and hybrid approaches. Proactive algorithms employ classical routing strategies such as distance-vector routing (e.g., DSDV [2]) or link-state routing (e.g., OLSR =-=[3]-=- and TBRPF [4]). They maintain routing information about the available paths in the network even if these paths are not currently used. The main drawback of these approaches is that the maintenance of...

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...urrently used. The main drawback of these approaches is that the maintenance of unused paths may occupy a significant part of the available bandwidth if the topology of the network changes frequently =-=[5]-=-. In response to this observation, reactive routing protocols were developed (e.g., DSR [6], TORA [7], and AODV [8]). Reactive routing protocols maintain only the routes that are currently in use, the...

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.... Therefore, the area covered by the ad hoc network increases as the number of nodes increases. Since the expected distance of two uniformly sampled points within a square of size a × a scales with a =-=[37]-=-, it is expected that the number of hops between two uniformly sampled participants increases proportional to the square root of the increase in nodes. Location Services Table 1 shows the location ser...

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...ed location services. Grid Routing — A second method for position-based ad hoc routing containing hierarchical elements is proposed in the Grid [22] project. The location proxy technique described in =-=[36]-=- is similar to Terminodes routing: a proactive distance vector routing protocol is used at the local level, while position based routing is employed for long-distance packet forwarding. In Grid routin...

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...irection until the information is found. While the algorithm described is still at an early stage, it is an interesting idea worth further study. Grid Location Service The Grid Location Service (GLS) =-=[20, 21]-=- is part of the Grid project [22]. It divides the area that contains the ad hoc network into a hierarchy of squares. In this hierarchy, n-order squares contain exactly four (n – 1)-order squares, form...

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... that information about the physical position of the participating nodes be available. Commonly, each node determines its own position through the use of GPS or some other type of positioning service =-=[12, 13]-=-, a survey of these methods can be found in [14]. A location service is used by the sender of a packet to determine the position of the destination and to include it in the packet’s destination addres...

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...ry remote nodes can be reduced since, as the authors argue, “the greater the distance separating two nodes, the slower they appear to be moving with respect to each other” (termed the distance effect =-=[17]-=-). An example of this “distance effect” is given in Fig. 2. Assume that in this example node A is not moving, while nodes B and C are moving in the same direction at the same speed. From node A’s pers...

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...o proactive, reactive, and hybrid approaches. Proactive algorithms employ classical routing strategies such as distance-vector routing (e.g., DSDV [2]) or link-state routing (e.g., OLSR [3] and TBRPF =-=[4]-=-). They maintain routing information about the available paths in the network even if these paths are not currently used. The main drawback of these approaches is that the maintenance of unused paths ...

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...rate on decentralized location services that are part of the ad hoc network. Distance Routing Effect Algorithm for Mobility Within the Distance Routing Effect Algorithm for Mobility (DREAM) framework =-=[16]-=-, each node maintains a position database that stores position information about each other node that is part of the network. It can therefore be classified as an all-for-all approach. An entry in the...

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...ure 6. Greedy routing failure. D S toward the destination with positive progress. Other researchers proposed not to forward packets that have reached a local maximum at all [26]. The face-2 algorithm =-=[29]-=- and the perimeter routing strategy of the Greedy Perimeter Stateless Routing Protocol (GPSR) [30, 31] are two very similar recovery approaches based on planar graph traversal. Both are performed on a...

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...for mobile ad hoc networks can also benefit from introduction of a hierarchy. Terminodes Routing — One approach that combines hierarchical and position-based routing is part of the Terminodes project =-=[34]-=-. In Terminodes routing a two-level hierarchy is proposed [35]. Packets are routed according to a proactive distance vector scheme if the destination is close (in terms of hops) to the sending node. F...

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...ks can be subdivided into two classes: static and mobile. In static ad hoc networks the position of a node may not change once it has become part of the network. Typical examples are rooftop networks =-=[1]-=-. For the remainder of this work we will solely focus on mobile ad hoc networks. In mobile ad hoc networks, systems may move arbitrarily. Examples where mobile ad hoc networks may be employed are the ...

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... that information about the physical position of the participating nodes be available. Commonly, each node determines its own position through the use of GPS or some other type of positioning service =-=[12, 13]-=-, a survey of these methods can be found in [14]. A location service is used by the sender of a packet to determine the position of the destination and to include it in the packet’s destination addres...

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...irection until the information is found. While the algorithm described is still at an early stage, it is an interesting idea worth further study. Grid Location Service The Grid Location Service (GLS) =-=[20, 21]-=- is part of the Grid project [22]. It divides the area that contains the ad hoc network into a hierarchy of squares. In this hierarchy, n-order squares contain exactly four (n – 1)-order squares, form...