Position-Based Routing Protocols for Ad Hoc Networks - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 45

each node is then based on the destination's position contained in the packet and
the position of the forwarding node's neighbors. So the packets are delivered to the
nodes in a given geographic region in a natural way. There are different kinds of
position-based protocols that are categorized into three main groups: restricted
directional flooding, greedy, and hierarchical routing protocols [ 6 ] (to be discussed
in Section 4.2 ).
This survey, which is a continuation of our work in [ 7 ], gives an overview of a
large percentage of existing position-based routing protocols for mobile Ad Hoc
networks. We outlined the main problems that have to be solved for this class of routing
protocols and presented the solutions that are currently available. The discussed pro-
tocols are also compared with respect to the used location service, the used forwarding
strategy, tolerability to position inaccuracy, robustness, implementation complexity,
scalability, packet and processing overhead, guaranteeing loop-freedom, probability
of finding the shortest path, and the suitable network density to be implemented in.
The protocols that have been selected for analysis are MFR [ 8 ], DIR [ 9 ], GPSR
[ 10 ], ARP [ 1 ], IPBBLR [ 4 ], DREAM [ 11 ], LAR [ 12 ], LARWB [ 13 ], MLAR [ 14 ],
GRID [ 15 ], TERMINODES [ 16 ], LABAR [ 17 ], POSANT [ 18 ], PAGs [ 19 ], SPAAR
[ 5 ], AODPR [ 20 ], and SGF [ 21 ]. It worth noting that many other position-based
routing protocols exist for mobile Ad Hoc networks; however, we have selected
what we regard as representative for the existing approaches.
The rest of the chapter is organized as follows. Section 4.2 presents the basic
idea and principles of position-based addressing and routing. Section 4.3 gives an
overview of the selected position-based routing protocols. Section 4.4 contains a
qualitative comparison of the discussed protocols. Directions of future research are
discussed in Section 4.5 . Finally, we conclude the chapter in Section 4.6 .

4.2 Basic Principles of Position-Based Routing

The main prerequisite for position-based routing is that a sender can obtain the
current position of the destination. Typically, a location service is responsible for
this task. Existing location services can be classified according to how many nodes
host the service. This can be either some specific nodes or all nodes of the network.
Furthermore, each location server may maintain the position of some specific or all
nodes in the network. The four possible combinations can be abbreviated as
some-for-some, some-for-all, all-for-some, and all-for-all [ 6 ].
There are three main packet-forwarding strategies used for position-based protocols:
greedy forwarding, restricted directional flooding, and hierarchical approaches.
While their main objective is to utilize available position information in the Ad Hoc
routing, their means to achieve it are quite different. Most position-based protocols
use greedy forwarding to route packets from a source to the destination. Greedy
protocols do not establish and maintain paths from source to the destination,
instead, a source node includes the approximate position of the recipient in the data
packet and selects the next hop depending on the optimization criteria of the algorithm;