375 research outputs found
Flow Allocation for Maximum Throughput and Bounded Delay on Multiple Disjoint Paths for Random Access Wireless Multihop Networks
In this paper, we consider random access, wireless, multi-hop networks, with
multi-packet reception capabilities, where multiple flows are forwarded to the
gateways through node disjoint paths. We explore the issue of allocating flow
on multiple paths, exhibiting both intra- and inter-path interference, in order
to maximize average aggregate flow throughput (AAT) and also provide bounded
packet delay. A distributed flow allocation scheme is proposed where allocation
of flow on paths is formulated as an optimization problem. Through an
illustrative topology it is shown that the corresponding problem is non-convex.
Furthermore, a simple, but accurate model is employed for the average aggregate
throughput achieved by all flows, that captures both intra- and inter-path
interference through the SINR model. The proposed scheme is evaluated through
Ns2 simulations of several random wireless scenarios. Simulation results reveal
that, the model employed, accurately captures the AAT observed in the simulated
scenarios, even when the assumption of saturated queues is removed. Simulation
results also show that the proposed scheme achieves significantly higher AAT,
for the vast majority of the wireless scenarios explored, than the following
flow allocation schemes: one that assigns flows on paths on a round-robin
fashion, one that optimally utilizes the best path only, and another one that
assigns the maximum possible flow on each path. Finally, a variant of the
proposed scheme is explored, where interference for each link is approximated
by considering its dominant interfering nodes only.Comment: IEEE Transactions on Vehicular Technolog
Throughput Optimal Flow Allocation on Multiple Paths for Random Access Wireless Multi-hop Networks
In this paper we consider random access wireless multi-hop mesh networks with
multi-packet reception capabilities where multiple flows are forwarded to the
gateways through node disjoint paths. We address the issue of aggregate
throughput-optimal flow rate allocation with bounded delay guarantees. We
propose a distributed flow rate allocation scheme that formulates flow rate
allocation as an optimization problem and derive the conditions for
non-convexity for an illustrative topology. We also employ a simple model for
the average aggregate throughput achieved by all flows that captures both
intra- and inter-path interference. The proposed scheme is evaluated through
NS-2 simulations. Our preliminary results are derived from a grid topology and
show that the proposed flow allocation scheme slightly underestimates the
average aggregate throughput observed in two simulated scenarios with two and
three flows respectively. Moreover it achieves significantly higher average
aggregate throughput than single path utilization in two different traffic
scenarios examined.Comment: Accepted for publication at the 9th IEEE BROADBAND WIRELESS ACCESS
WORKSHOP (BWA2013), IEEE Globecom 2013 Workshop
Resource Allocation in Ad Hoc Networks
Unlike the centralized network, the ad hoc network does not have any central administrations and energy is constrained, e.g. battery, so the resource allocation plays a
very important role in efficiently managing the limited energy in ad hoc networks.
This thesis focuses on the resource allocation in ad hoc networks and aims to develop
novel techniques that will improve the network performance from different network
layers, such as the physical layer, Medium Access Control (MAC) layer and network
layer.
This thesis examines the energy utilization in High Speed Downlink Packet Access (HSDPA) systems at the physical layer. Two resource allocation techniques,
known as channel adaptive HSDPA and two-group HSDPA, are developed to improve the performance of an ad hoc radio system through reducing the residual
energy, which in turn, should improve the data rate in HSDPA systems. The channel adaptive HSDPA removes the constraint on the number of channels used for
transmissions. The two-group allocation minimizes the residual energy in HSDPA
systems and therefore enhances the physical data rates in transmissions due to adaptive modulations. These proposed approaches provide better data rate than rates
achieved with the current HSDPA type of algorithm.
By considering both physical transmission power and data rates for defining the
cost function of the routing scheme, an energy-aware routing scheme is proposed
in order to find the routing path with the least energy consumption. By focusing
on the routing paths with low energy consumption, computational complexity is
significantly reduced. The data rate enhancement achieved by two-group resource
allocation further reduces the required amount of energy per bit for each path. With
a novel load balancing technique, the information bits can be allocated to each path
in such that a way the overall amount of energy consumed is minimized.
After loading bits to multiple routing paths, an end-to-end delay minimization
solution along a routing path is developed through studying MAC distributed coordination function (DCF) service time. Furthermore, the overhead effect and the
related throughput reduction are studied. In order to enhance the network throughput at the MAC layer, two MAC DCF-based adaptive payload allocation approaches
are developed through introducing Lagrange optimization and studying equal data
transmission period
Mobility in wireless sensor networks : advantages, limitations and effects
The primary aim of this thesis is to study the benefits and limitations of using a mobile base station for data gathering in wireless sensor networks. The case of a single mobile base station and mobile relays are considered.
A cluster-based algorithm to determine the trajectory of a mobile base station for data gathering within a specified delay time is presented. The proposed algorithm aims for an equal number of sensors in each cluster in order to achieve load balance among the cluster heads. It is shown that there is a tradeoff between data-gathering delay and balancing energy consumption among sensor nodes. An analytical solution to the problem is provided in terms of the speed of the mobile base station. Simulation is performed to evaluate the performance of the proposed algorithm against the static case and to evaluate the distribution of energy consumption among the cluster heads. It is demonstrated that the use of clustering with a mobile base station can improve the network lifetime and that the proposed algorithm balances energy consumption among cluster heads. The effect of the base station velocity on the number of packet losses is studied and highlights the limitation of using a mobile base station for a large-scale network.
We consider a scenario where a number of mobile relays roam through the sensing field and have limited energy resources that cannot reach each other directly. A routing scheme based on the multipath protocol is proposed, and explores how the number of paths and spread of neighbour nodes used by the mobile relays to communicate affects the network overhead. We introduce the idea of allowing the source mobile relay to cache multiple routes to the destination through its neighbour nodes in order to provide redundant paths to destination. An analytical model of network overhead is developed and verified by simulation. It is shown that the desirable number of routes is dependent on the velocity of the mobile relays. In most cases the network overhead is minimized when the source mobile relay caches six paths via appropriately distributed neighbours at the destination.
A new technique for estimating routing-path hop count is also proposed. An analytical model is provided to estimate the hop count between source-destination pairs in a wireless network with an arbitrary node degree when the network nodes are uniformly distributed in the sensing field. The proposed model is a significant improvement over existing models, which do not correctly address the low-node density situation
A multipath energy-conserving routing protocol for wireless ad hoc networks lifetime improvement
Ad hoc networks are wireless mobile networks that can operate without
infrastructure and without centralized network management. Traditional
techniques of routing are not well adapted. Indeed, their lack of reactivity
with respect to the variability of network changes makes them difficult to use.
Moreover, conserving energy is a critical concern in the design of routing
protocols for ad hoc networks, because most mobile nodes operate with limited
battery capacity, and the energy depletion of a node affects not only the node
itself but also the overall network lifetime. In all proposed single-path
routing schemes a new path-discovery process is required once a path failure is
detected, and this process causes delay and wastage of node resources. A
multipath routing scheme is an alternative to maximize the network lifetime. In
this paper, we propose an energy-efficient multipath routing protocol, called
AOMR-LM (Ad hoc On-demand Multipath Routing with Lifetime Maximization), which
preserves the residual energy of nodes and balances the consumed energy to
increase the network lifetime. To achieve this goal, we used the residual
energy of nodes for calculating the node energy level. The multipath selection
mechanism uses this energy level to classify the paths. Two parameters are
analyzed: the energy threshold beta and the coefficient alpha. These parameters
are required to classify the nodes and to ensure the preservation of node
energy. Our protocol improves the performance of mobile ad hoc networks by
prolonging the lifetime of the network. This novel protocol has been compared
with other protocols: AOMDV and ZD-AOMDV. The protocol performance has been
evaluated in terms of network lifetime, energy consumption, and end-to-end
delay
Improving network reliability by exploiting path diversity in ad hoc networks with bursty losses
In wireless mobile ad hoc networks, end-to-end connections are often subject to failures which do not make the connection non-operational indefinitely but interrupt the communication for intermittent short periods of time. These intermittent failures usually arise from the mobility of hosts, dynamics of the wireless medium or energy-saving mechanisms, and cause bursty packet losses. Reliable communication in this kind of an environment is becoming more important with the emerging use of ad hoc networks for carrying diverse multimedia applications such as voice, video and data. In this thesis, we present a new path reliability model that captures intermittent availability of the paths, and we devise a routing strategy based on our path reliability model in order to improve the network reliability. Our routing strategy takes the advantage of path diversity in the network and uses a diversity coding scheme in order not to compromise efficiency. In diversity coding scheme, if the original information is encoded by using a (N,K) code, then it is enough for the destination to receive any K bits correctly out of N bits to successfully decode the original information. In our scheme, the original information is divided into N subpackets and subpackets are distributed among the available disjoint paths in the network. The distribution of subpackets among the diverse paths is a crucial decision. The subpackets should be distributed 'intelligently' so that the probability of successful reconstruction of the original information is maximized. Given the failure statistics of the paths, and the code rate (N, K), our strategy determines the allocation of subpackets to each path in such a manner that the probability of reconstruction of the original information at the destination is maximized. Simulation results justify the accuracy and efficiency of our approach. Additionally, simulation results show that our multipath routing strategy improves the network reliability substantially compared to the single path routing. In wireless networks, a widely used strategy is to place the nodes into a low energy consuming sleep mode in order to prolong the battery life. In this study, we also consider the cases where the intermittent availability of the nodes is due to the sleep/awake cycles of wireless nodes. A sleep/awake scheduling strategy is proposed which minimizes the packet latency while satisfying the energy saving ratio specified by the energy saving mechanism
Energy-aware Dual-path Geographic Routing to Bypass Routing Holes in Wireless Sensor Networks
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.Geographic routing has been considered as an attractive approach for resource-constrained wireless sensor networks
(WSNs) since it exploits local location information instead of global topology information to route data. However, this routing approach
often suffers from the routing hole (i.e., an area free of nodes in the direction closer to destination) in various environments such as
buildings and obstacles during data delivery, resulting in route failure. Currently, existing geographic routing protocols tend to walk
along only one side of the routing holes to recover the route, thus achieving suboptimal network performance such as longer delivery
delay and lower delivery ratio. Furthermore, these protocols cannot guarantee that all packets are delivered in an energy-efficient
manner once encountering routing holes. In this paper, we focus on addressing these issues and propose an energy-aware dual-path
geographic routing (EDGR) protocol for better route recovery from routing holes. EDGR adaptively utilizes the location information,
residual energy, and the characteristics of energy consumption to make routing decisions, and dynamically exploits two node-disjoint
anchor lists, passing through two sides of the routing holes, to shift routing path for load balance. Moreover, we extend EDGR into
three-dimensional (3D) sensor networks to provide energy-aware routing for routing hole detour. Simulation results demonstrate that
EDGR exhibits higher energy efficiency, and has moderate performance improvements on network lifetime, packet delivery ratio, and
delivery delay, compared to other geographic routing protocols in WSNs over a variety of communication scenarios passing through
routing holes. The proposed EDGR is much applicable to resource-constrained WSNs with routing holes.This work has been partially supported by the National
Natural Science Foundation of China (No. 61402343,
No. 61672318, No. U1504614, No. 61631013, and No.
61303241), the National Key Research and Development
Program (No. 2016YFB1000102), the Natural Science
Foundation of Suzhou/Jiangsu Province (No.
BK20160385), the EU FP7 QUICK Project (No. PIRSESGA-
2013-612652), and the projects of Tsinghua National
Laboratory for Information Science and Technology
(TNList)
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