8 research outputs found
Cache timeout strategies for on-demand routing in MANETs
Varying the route caching scheme can significantly
change network performance for on-demand routing protocols
in mobile ad hoc networks (MANETs). Initial
route caching schemes retain paths or links until they are
shown to be broken. However, stale routing information
can degrade network performance with latency and extra
routing overhead. Therefore, more recent caching schemes
delete links at some fixed time after they enter the cache.
This paper proposes using either the expected path duration
or the link residual time as the link cache timeout.
These mobility metrics are theoretically calculated for an
appropriate random mobility model. Simulation results in
NS2 show that both of the proposed link caching schemes
can improve network performance in the dynamic source
routing protocol (DSR) by reducing dropped data packets,
latency and routing overhead, with the link residual time
scheme out-performing the path duration scheme.IEEE, South Australian Sectio
Intelligent MANET optimisation system
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.In the literature, various Mobile Ad hoc NETwork (MANET) routing protocols proposed. Each performs the best under specific context conditions, for example under high mobility or less volatile topologies. In existing MANET, the degradation in the routing protocol performance is always associated with changes in the network context. To date, no MANET routing protocol is able to produce optimal performance under all possible conditions.
The core aim of this thesis is to solve the routing problem in mobile Ad hoc networks by introducing an optimum system that is in charge of the selection of the running routing protocol at all times, the system proposed in this thesis aims to address the degradation mentioned above. This optimisation system is a novel approach that can cope with the network performance’s degradation problem by switching to other routing protocol. The optimisation system proposed for MANET in this thesis adaptively selects the best routing protocol using an Artificial Intelligence mechanism according to the network context.
In this thesis, MANET modelling helps in understanding the network performance through different contexts, as well as the models’ support to the optimisation system. Therefore, one of the main contributions of this thesis is the utilisation and comparison of various modelling techniques to create representative MANET performance models. Moreover, the proposed system uses an optimisation method to select the optimal communication routing protocol for the network context. Therefore, to build the proposed system, different optimisation techniques were utilised and compared to identify the best optimisation technique for the MANET intelligent system, which is also an important contribution of this thesis.
The parameters selected to describe the network context were the network size and average mobility. The proposed system then functions by varying the routing mechanism with the time to keep the network performance at the best level. The selected protocol has been shown to produce a combination of: higher throughput, lower delay, fewer retransmission attempts, less data drop, and lower load, and was thus chosen on this basis. Validation test results indicate that the identified protocol can achieve both a better network performance quality than other routing protocols and a minimum cost function of 4.4%. The Ad hoc On Demand Distance Vector (AODV) protocol comes in second with a cost minimisation function of 27.5%, and the Optimised Link State Routing (OLSR) algorithm comes in third with a cost minimisation function of 29.8%. Finally, The Dynamic Source Routing (DSR) algorithm comes in last with a cost minimisation function of 38.3%
Resource-efficient strategies for mobile ad-hoc networking
The ubiquity and widespread availability of wireless mobile devices with ever increasing
inter-connectivity (e. g. by means of Bluetooth, WiFi or UWB) have led to new and emerging
next generation mobile communication paradigms, such as the Mobile Ad-hoc NETworks
(MANETs). MANETs are differentiated from traditional mobile systems by their unique properties,
e. g. unpredictable nodal location, unstable topology and multi-hop packet relay. The
success of on-going research in communications involving MANETs has encouraged their applications
in areas with stringent performance requirements such as the e-healthcare, e. g. to
connect them with existing systems to deliver e-healthcare services anytime anywhere. However,
given that the capacity of mobile devices is restricted by their resource constraints (e. g.
computing power, energy supply and bandwidth), a fundamental challenge in MANETs is how
to realize the crucial performance/Quality of Service (QoS) expectations of communications in
a network of high dynamism without overusing the limited resources.
A variety of networking technologies (e. g. routing, mobility estimation and connectivity
prediction) have been developed to overcome the topological instability and unpredictability
and to enable communications in MANETs with satisfactory performance or QoS. However,
these technologies often feature a high consumption of power and/or bandwidth, which makes
them unsuitable for resource constrained handheld or embedded mobile devices. In particular,
existing strategies of routing and mobility characterization are shown to achieve fairly
good performance but at the expense of excessive traffic overhead or energy consumption. For
instance, existing hybrid routing protocols in dense MANETs are based in two-dimensional organizations
that produce heavy proactive traffic. In sparse MANETs, existing packet delivery
strategy often replicates too many copies of a packet for a QoS target. In addition, existing
tools for measuring nodal mobility are based on either the GPS or GPS-free positioning systems,
which incur intensive communications/computations that are costly for battery-powered
terminals. There is a need to develop economical networking strategies (in terms of resource
utilization) in delivering the desired performance/soft QoS targets.
The main goal of this project is to develop new networking strategies (in particular, for
routing and mobility characterization) that are efficient in terms of resource consumptions while
being effective in realizing performance expectations for communication services (e. g. in the
scenario of e-healthcare emergency) with critical QoS requirements in resource-constrained
MANETs.
The main contributions of the thesis are threefold:
(1) In order to tackle the inefficient bandwidth utilization of hybrid service/routing discovery
in dense MANETs, a novel "track-based" scheme is developed. The scheme deploys
a one-dimensional track-like structure for hybrid routing and service discovery. In comparison
with existing hybrid routing/service discovery protocols that are based on two-dimensional
structures, the track-based scheme is more efficient in terms of traffic overhead (e. g. about 60%
less in low mobility scenarios as shown in Fig. 3.4). Due to the way "provocative tracks" are
established, the scheme has also the capability to adapt to the network traffic and mobility for
a better performance.
(2) To minimize the resource utilization of packet delivery in sparse MANETs where wireless
links are intermittently connected, a store-and-forward based scheme, "adaptive multicopy
routing", was developed for packet delivery in sparse mobile ad-hoc networks. Instead
of relying on the source to control the delivery overhead as in the conventional multi-copy
protocols, the scheme allows each intermediate node to independently decide whether to forward
a packet according to the soft QoS target and local network conditions. Therefore, the
scheme can adapt to varying networking situations that cannot be anticipated in conventional
source-defined strategies and deliver packets for a specific QoS targets using minimum traffic
overhead.
ii
(3) The important issue of mobility measurement that imposes heavy communication/computation
burdens on a mobile is addressed with a set of resource-efficient "GPS-free" soluti ons,
which provide mobility characterization with minimal resource utilization for ranging and signalling
by making use of the information of the time-varying ranges between neighbouring
mobile nodes (or groups of mobile nodes). The range-based solutions for mobility characterization
consist of a new mobility metric for network-wide performance measurement, two
velocity estimators for approximating the inter-node relative speeds, and a new scheme for
characterizing the nodal mobility. The new metric and its variants are capable of capturing the
mobility of a network as well as predicting the performance. The velocity estimators are used to
measure the speed and orientation of a mobile relative to its neighbours, given the presence of a
departing node. Based on the velocity estimators, the new scheme for mobility characterization
is capable of characterizing the mobility of a node that are associated with topological stability,
i. e. the node's speeds, orientations relative to its neighbouring nodes and its past epoch time.
iiiBIOPATTERN EU Network of Excellence (EU Contract 508803
Mobility Metrics for Routing in MANETs
A Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without the need for base stations or any other pre–existing network infrastructure. In a peer-to-peer fashion, mobile nodes can communicate with each other by using wireless multihop communication. Due to its low cost, high flexibility, fast network establishment and self-reconfiguration, ad hoc networking has received much interest during the last ten years. However, without a fixed infrastructure, frequent path changes cause significant numbers of routing packets to discover new paths, leading to increased network congestion and transmission latency over fixed networks. Many on-demand routing protocols have been developed by using various routing mobility metrics to choose the most reliable routes, while dealing with the primary obstacle caused by node mobility. ¶ In the first part, we have developed an analysis framework for mobility metrics in random mobility model. ... ¶ In the second part, we investigate the mobility metric applications on caching strategies and hierarchy routing algorithm. ..