35 research outputs found
Impact of Sparse and Dense Deployment of Nodes Under Different Propagation Models in Manets
Mobile Ad-hoc Network (MANET) is the most emerging and fast-expanding technology in the last two decades. One of the major issues and challenging areas in MANET is the process of routing due to dynamic topologies and high mobility of mobile nodes. The efficiency and accuracy of a protocol depend on many parameters in these networks. In addition to other parameters node velocity and propagation models are among them. Calculating signal strength at the receiver is the responsibility of a propagation model while the mobility of nodes is responsible for the topology of the network. A huge amount of loss in performance is occurred due to the variation of signal strength at the receiver and obstacles between transmissions. In this paper,it has been analyzed to check the impact of different propagation models on the performance of Optimized Link State Routing (OLSR) in Sparse and Dense scenarios in MANET. The simulation has been carried out in NS-2 by using performance metrics as average packet drop average latency and average Throughput. The results predicted that propagation models and mobility have a strong impact on the performance of OLSR in considered scenarios
Topology control and data handling in wireless sensor networks
Our work in this thesis have provided two distinctive contributions to WSNs in the
areas of data handling and topology control.
In the area of data handling, we have demonstrated a solution to improve the
power efficiency whilst preserving the important data features by data compression
and the use of an adaptive sampling strategy, which are applicable to the specific
application for oceanography monitoring required by the SECOAS project. Our work
on oceanographic data analysis is important for the understanding of the data we are
dealing with, such that suitable strategies can be deployed and system performance
can be analysed. The Basic Adaptive Sampling Scheduler (BASS) algorithm uses
the statistics of the data to adjust the sampling behaviour in a sensor node according
to the environment in order to conserve energy and minimise detection delay.
The motivation of topology control (TC) is to maintain the connectivity of the
network, to reduce node degree to ease congestion in a collision-based medium access
scheme; and to reduce power consumption in the sensor nodes. We have developed
an algorithm Subgraph Topology Control (STC) that is distributed and does not
require additional equipment to be implemented on the SECOAS nodes. STC uses
a metric called subgraph number, which measures the 2-hops connectivity in the
neighbourhood of a node. It is found that STC consistently forms topologies that
have lower node degrees and higher probabilities of connectivity, as compared to k-Neighbours, an alternative algorithm that does not rely on special hardware on sensor
node. Moreover, STC also gives better results in terms of the minimum degree in the
network, which implies that the network structure is more robust to a single point
of failure. As STC is an iterative algorithm, it is very scalable and adaptive and is
well suited for the SECOAS applications
Performance Analysis of Train Communication Systems
Trains are considered as a highly efficient transport mode which generate significant
challenges in terms of their communication systems. For improved safety, to cope with
the expected rapid increase in traffic, and to meet customer demands, an enhanced
and reliable communication system is required for high-speed trains (HSRs). Mobile
phone and laptop users would like to make use of the non-negligible time that they
spend commuting but current HSR communication systems have a foreseeable end
to their lifetime and a reliable, efficient, and fast communication replacement system
has become essential. Encouraged by the use of existing power line networks for
communication purposes, this research investigates the possibility of developing a train
communication system based on the use of overhead line equipment (OLE). The ABCD
transfer line model is developed to represent the transfer function of the OLE channel
and is evaluated using computer simulations. The simulations of the OLE system used
are based on orthogonal frequency division multiplexing as the chosen modulation
scheme.
Within the train, for the provision of broadband services, developing a reliable
communication system which is a combination of power line communication and
optical wireless communication services using visible light communication (VLC)
is considered. Mathematical methods were developed for these networks to assess
the overall capacities and outage probabilities of the hybrid systems. Derivation of
such analytical expressions offered opportunities to investigate the impact of several
system parameters on the performance of the system. To assess the possibility of
improving the performance of the proposed integrated systems, their performance in
the presence of different relaying protocols has been comprehensively analyzed in
terms of capacity and outage probability. This thesis studied the outage probability and
energy per bit consumption performance of different relaying protocols over the VLC
channel. Accurate analytical expressions for the overall outage probability and energyper-bit consumption of the proposed system configurations, including the single-hop
and multi-hop approaches were derived.
It was found that the transfer function of the OLE channel can be represented by the
two-port network model. It was also revealed that transmission over OLE is negatively
affected by the speed of the train, frequency, and length of the OLE link. In train, relay-based communication systems can provide reliable connectivity to the end-user.
However, choosing an optimal system configuration can enhance system performance.
It was also shown that increasing relay numbers on the network contributes to the total
power consumption of the system