Position-Based Routing Protocols for Ad Hoc Networks - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 68

• Forwarding strategy implementation complexity: describes how complex it is to

implement and test a given forwarding strategy. This measure is highly subjec-
tive and we will explain our opinion while discussing each protocol.
Forwarding strategy scalability: describes the performance of the protocol with

•

increasing number of nodes in the network. It can be classified as follows: high
scalability is used when a network grows as much as it needs and the approach
is still able to maintain a good performance. Medium scalability means that an
approach can handle networks with a reasonable size, but may have problems if
it grows. Low scalability describes protocols which restrict to small networks.
Since all the position-based routing protocols are scalable, all the discussed proto-
cols have at least medium scalability.
Forwarding strategy packet overhead: refers to bandwidth consumption due to •

larger packets and/or higher number of signaling packets. The protocols can be
classified as follows: Low overhead is used to describe protocols which have
small packets and reduce the number of packets sent using unicast for example.
Medium overhead is used to classify the protocols that have small packets but
require large number of signaling packets, or if they require larger packets but
use unicast to send the data. High overhead means that an approach requires
larger packets as well as an increased number of signaling packets. Note that all
the position-based routing protocols have lower packet overhead compared to
other types, but this criterion is defined to compare the position-based routing
protocols together.
Forwarding strategy processing overhead: is used to associate each protocol with •

processing requirements. Low processing refers to approaches that require a low
CPU processing, such as unsecure protocols. Medium processing will be used to
classify the secured protocols. High processing is used to describe protocols that
use multiple security techniques together.
Loop-freedom: any routing protocol should be inherently loop-free to preserve the

•

network resources and guarantee the correct operation of the protocol. Therefore,
the discussed protocols are classified as having or not having loop-freedom
property.
Optimal path: is used to indicate the protocol probability of finding and using •

the shortest path for data packet relay.
Density: indicates whether the protocol is more suitable to be implemented in a •

dense network, sparse network, or both.

As other greedy forwarding protocols, all nodes in MFR maintain a one-hop neigh-
bor table, i.e., MFR uses all-for-some location service. Hence, a given node will be
inaccessible upon the failure of a subset of the nodes, i.e., its location service has a
medium robustness. However, the technique that is used to enable the source to
know the position of the destination is not discussed. Greedy forwarding is both
efficient and very well suited for use in Ad Hoc networks with a highly dynamic
topology [ 6 ]. However, one important drawback of the current greedy approaches
is that the position of the destination needs to be known with an accuracy of a one-
hop transmission range, otherwise the packets cannot be delivered [ 6 ].