10,047 research outputs found
Throughput Optimization in Multi-hop Wireless Networks with Random Access
This research investigates cross-layer design in multi-hop wireless networks with
random access. Due to the complexity of the problem, we study cross-layer design
with a simple slotted ALOHA medium access control (MAC) protocol without considering any network dynamics. Firstly, we study the optimal joint configuration of routing and MAC parameters in slotted ALOHA based wireless networks under a signal to interference plus noise ratio based physical interference model. We formulate a
joint routing and MAC (JRM) optimization problem under a saturation assumption
to determine the optimal max-min throughput of the flows and the optimal configuration of routing and MAC parameters. The JRM optimization problem is a complex
non-convex problem. We solve it by an iterated optimal search (IOS) technique and
validate our model via simulation. Via numerical and simulation results, we show
that JRM design provides a significant throughput gain over a default configuration
in a slotted ALOHA based wireless network.
Next, we study the optimal joint configuration of routing, MAC, and network
coding in wireless mesh networks using an XOR-like network coding without opportunistic listening. We reformulate the JRM optimization problem to include the
simple network coding and obtain a more complex non-convex problem. Similar to
the JRM problem, we solve it by the IOS technique and validate our model via simulation. Numerical and simulation results for different networks illustrate that (i) the jointly optimized configuration provides a remarkable throughput gain with respect
to a default configuration in a slotted ALOHA system with network coding and (ii)
the throughput gain obtained by the simple network coding is significant, especially
at low transmission power, i.e., the gain obtained by jointly optimizing routing, MAC,
and network coding is significant even when compared to an optimized network without network coding. We then show that, in a mesh network, a significant fraction of
the throughput gain for network coding can be obtained by limiting network coding
to nodes directly adjacent to the gateway.
Next, we propose simple heuristics to configure slotted ALOHA based wireless
networks without and with network coding. These heuristics are extensively evaluated
via simulation and found to be very efficient. We also formulate problems to jointly
configure not only the routing and MAC parameters but also the transmission rate
parameters in multi-rate slotted ALOHA systems without and with network coding.
We compare the performance of multi-rate and single rate systems via numerical
results.
We model the energy consumption in terms of slotted ALOHA system parameters.
We found out that the energy consumption for various cross-layer systems, i.e., single
rate and multi-rate slotted ALOHA systems without and with network coding, are
very close
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
Medium Access Control and Network Coding for Wireless Information Flows
This dissertation addresses the intertwined problems of medium access control (MAC) and network coding in ad hoc wireless networks. The emerging wireless network applications introduce new challenges that go beyond the classical understanding of wireline networks based on layered architecture and cooperation. Wireless networks involve strong interactions between MAC and network layers that need to be jointly specified in a cross-layer design framework with cooperative and non-cooperative users.
For multi-hop wireless networks, we first rediscover the value of scheduled access at MAC layer through a detailed foray into the questions of throughput and energy consumption. We propose a distributed time-division mechanism to activate dynamic transmitter-receiver assignments and eliminate interference at non-intended receivers for throughput and energy-efficient resource allocation based on stable operation with arbitrary single-receiver MAC protocols.
In addition to full cooperation, we consider competitive operation of selfish users with individual performance objectives of throughput, energy and delay. We follow a game-theoretic approach to evaluate the non-cooperative equilibrium strategies at MAC layer and discuss the coupling with physical layer through power and rate control. As a cross-layer extension to multi-hop operation, we analyze the non-cooperative operation of joint MAC and routing, and introduce cooperation stimulation mechanisms for packet forwarding. We also study the impact of malicious transmitters through a game formulation of denial of service attacks in random access and power-controlled MAC.
As a new networking paradigm, network coding extends routing by allowing intermediate transmitters to code over the received packets. We introduce the adaptation of network coding to wireless environment in conjunction with MAC. We address new research problems that arise when network coding is cast in a cross-layer optimization framework with stable operation. We specify the maximum throughput and stability regions, and show the necessity of joint design of MAC and network coding for throughput and energy-efficient operation of cooperative or competitive users. Finally, we discuss the benefits of network coding for throughput stability in single-hop multicast communication over erasure channels. Deterministic and random coding schemes are introduced to optimize the stable throughput properties. The results extend our understanding of fundamental communication limits and trade-offs in wireless networks
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
Dynamic Queue Utilization Based MAC for multi-hop Ad Hoc networks
The end-to-end throughput in single flow multi-hop Ad Hoc networks decays rapidly with path length. Along the path, the success rate of delivering packets towards the destination decreases due to higher contention, interference, limited buffer size and limited shared bandwidth constraints. In such environments the queues fill up faster in nodes closer to the source than in the nodes nearer the destination. In order to reduce buffer overflow and improve throughput for a saturated network, this paper introduces a new MAC protocol named Dynamic Queue Utilization Based Medium Access Control (DQUB-MAC). The protocol aims to prioritise access to the channel for queues with higher utilization and helps in achieving higher throughput by rapidly draining packets towards the destination. The proposed MAC enhances the performance of an end-to-end data flow by up to 30% for a six hop transmission in a chain topology and is demonstrated to remain competitive for other network topologies and for a variety of packet sizes
Queue utilization with hop based enhanced arbitrary inter frame spacing MAC for saturated ad HOC networks
© 2015 IEEE. Path length of a multi hop Ad Hoc networks has an adverse impact on the end-to-end throughput especially during network saturation. The success rate of forwarding packets towards destination is limited due to interference, contention, limited buffer space, and bandwidth. Real time applications streaming data fill the buffer space at a faster rate at the source and its nearby forwarding nodes since the channel is shared. The aim of this paper is to increase the success rate of forwarding the packets to yield a higher end-to-end throughput. In order to reduce loss of packets due to buffer overflow and enhance the performance of the network for a saturated network, a novel MAC protocol named Queue Utilization with Hop Based Enhanced Arbitrary Inter Frame Spacing based (QU-EAIFS) MAC is proposed for alleviating the problems in saturated Ad Hoc networks. The protocol prioritises the nodes based on its queue utilization and hops travelled by the packet and it helps achieving higher end-toend performance by forwarding the packets with higher rate towards the destination during network saturation. The proposed MAC enhances the end-to-end performance by approximately 40% and 34% for a 5hop and 6hop communication respectively in a chain topology as compared to the standard IEEE802.11b. The performance of the new MAC also outperforms the performance of IEEE 802.11e MAC. In order to validate the protocol, it is also tested with short hops and varying packet sizes and more realistic random topologies
Decentralized Dynamic Hop Selection and Power Control in Cognitive Multi-hop Relay Systems
In this paper, we consider a cognitive multi-hop relay secondary user (SU)
system sharing the spectrum with some primary users (PU). The transmit power as
well as the hop selection of the cognitive relays can be dynamically adapted
according to the local (and causal) knowledge of the instantaneous channel
state information (CSI) in the multi-hop SU system. We shall determine a low
complexity, decentralized algorithm to maximize the average end-to-end
throughput of the SU system with dynamic spatial reuse. The problem is
challenging due to the decentralized requirement as well as the causality
constraint on the knowledge of CSI. Furthermore, the problem belongs to the
class of stochastic Network Utility Maximization (NUM) problems which is quite
challenging. We exploit the time-scale difference between the PU activity and
the CSI fluctuations and decompose the problem into a master problem and
subproblems. We derive an asymptotically optimal low complexity solution using
divide-and-conquer and illustrate that significant performance gain can be
obtained through dynamic hop selection and power control. The worst case
complexity and memory requirement of the proposed algorithm is O(M^2) and
O(M^3) respectively, where is the number of SUs
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