Position-Based Routing Protocols for Ad Hoc Networks - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 57

This routing scheme is a combination of two protocols called Terminode Local
Routing (TLR) and Terminode Remote Routing (TRR). TLR is a mechanism that
allows to reaching destinations in the vicinity of a terminode and does not use loca-
tion information for making packet forwarding decisions. TRR is used to send data
to remote destinations and uses geographic information; it is the key element for
achieving scalability and reduced dependence on intermediate systems. The major
novelty is the Anchored Geodesic Packet Forwarding (AGPF) component of TRR.
This is a source-path-based method designed to be robust for mobile networks:
Instead of using traditional source paths, that is lists of nodes, it uses anchored
paths. An anchored path is a list of fixed geographical points, called anchor. The
packet loosely follows anchored path. At any point, the packet is sent in the direc-
tion of the next anchor in the anchored path by applying geodesic packet forwarding.
When a terminode finds that the next anchor geographically falls within its trans-
mission range, it deletes it from the anchored path and sends in the direction of the
new next anchor. This is repeated until the packet is sent in the direction of
the final destination [ 24 ].
Authors of [ 16 ] showed by means of simulations for mobile Ad Hoc networks
composed of several hundreds of terminodes, that the introduction of a hierarchy
can significantly improve the ratio of successfully delivered packets and the routing
overhead compared to reactive Ad Hoc routing algorithms. They also demon-
strated benefits of the combination of TLR and TRR over an existing protocol that
uses geographical information for packet forwarding [ 6, 15 ]. However, using
greedy routing in long-distance routing makes TERMINODES inherits the prob-
lems associated with it.

4.3.11 LABAR

Location Area Based Ad Hoc Routing for GPS-Scarce Wide-Area Ad Hoc Networks
(LABAR) [ 17 ] is a hybrid virtual backbone and geographical location area-based Ad
Hoc routing. Authors outlined that using GPS can increase the cost and power con-
sumption of small mobile nodes. Thus, LABAR requires only a subset of nodes
(called G-nodes) to know their exact location forming location areas around them.
G-nodes are interconnected into a virtual backbone structure to enable efficient
exchange of information for the mapping of IP addresses to locations. Nodes that are
not enabled with GPS equipment are called S-nodes.
Routing in LABAR consists mainly of three steps: zone formation, virtual
backbone formation, and directional routing. The first step of LABAR deals with
forming the zones, i.e., making the decision on which S-nodes should belong to
which G-nodes. It was assumed that all G-nodes start the zone formation algorithm
at the same time to acquire S-nodes. If an S-node has already been attached to a
G-node then the request message is ignored by the S-node. Upon including an S-node
in a zone, it initiates the zone formation algorithm on its own to draw more S-nodes
from its neighborhood into its zone. By the end of this step, all S-nodes will belong