This post examines the performance comparisons of multipath routing protocols (i.e. AOMDV and OLSR) with different background changes (i.e. node mobility and TCP congestion window size) in mobile ad hoc networks.
The most popular on-demand routing protocol, Ad-hoc On-demand Multipath Distance Vector (AOMDV) routing protocol is an enhancement of Ad-hoc On-demand Routing Protocol (AODV). AOMDV allows multiple paths between a source and a destination to provide efficient fault tolerance by providing faster and more efficient recovery from route failures in a dynamic network. By computing multiple paths in a single route discovery attempt, new route discovery is needed only when all paths fail. This reduces not only the route discovery latency but also the routing overheads.
Among proactive routing protocols, Optimized Link State Routing (OLSR) is an optimization of pure link state routing protocol and inherits the stability of a link state algorithm and takes over the advantage of proactive routing nature to provide the routes immediately when needed. OLSR minimizes the flooding of the control messages by allowing only selected nodes to relay.
In TCP-Reno, when the packet loss occurs, a TCP receiver sends a duplicate ACK immediately while a TCP sender utilizes a fast retransmit mechanism, where the arrival of 3 duplicate ACKs indicates that a packet has been lost and recovers the missing packet without waiting for a retransmission timer to expire. A fast recovery algorithm, in turn, governs the transmission of new data packets until a non-duplicate ACK arrives.
TCP-Vegas introduces a proactive congestion avoidance technique which does not violate the congestion avoidance paradigm of TCP. It is able to utilize extra bandwidth without the network congestion and oscillation in window size, whereas TCP Reno always updates its window size to guarantee full bandwidth utilization, which leads to packet losses constantly.
There are numerous applications of sensor networks. Here it is used for monitoring at an enterprise data center to reduce energy consumption and monitor various aspects of a data center.
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Posted by Mazliza -
September 26, 2011 at 11:05 am
The following are factors that must be considered to achieve efficient communications between nodes in a wireless sensor networks.
Node deployment may be manual/deterministic or random. In the former, nodes are manually placed and data is routed via pre-determined paths. In the latter case, nodes are scattered randomly, forming an ad hoc infrastructure. If the nodes are not uniformly distributed, it may be necessary to cluster the nodes to support connectivity and enable energy-efficient operations.
Sensor nodes are very dependent on battery lifetime because they are often left unattended for long periods of time, thus, it is imperative that communications and computations take an energy-conserving approach.
Data reporting method is either time-driven, even-driven, query-driven or a hybrid of these methods, depending on the criticality of the data. The time-driven method allows sensor nodes to periodically turn off their transmitters to conserve power. The event- and query-driven methods require sensors to react immediately to sudden and drastic changes in the environment, and are therefore, suitable for time-critical applications. The routing protocol is very influenced by the data reporting method in terms of energy consumption and route calculations.
