5 research outputs found
CROMA: An Enhanced Slotted MAC Protocol for MANETs
International audienceTDMA based MAC protocols can provide a very good utilization of the shared radio resources, especially at high input loads, in synchronized mobile ad hoc networks (MANETs). Global positioning systems like GPS or GALLILEO should provide a very good timing accuracy for synchronization of nodes. This paper presents a new medium access protocol for mobile ad hoc networks, called CROMA. CROMA is collision-free and receiver-oriented. It operates in a slotted environment, in a dynamic and distributed way. In this protocol, receivers act as local base stations and can manage one or several communications on a single slot. Thus, sophisticated functions are allowed at higher layers. Moreover, the hidden terminal as well as the exposed terminal problems are handled by CROMA. A theoretical analysis and extensive simulations show that CROMA can reach very high throughputs
Energy efficient medium access protocol for DS-CDMA based wireless sesor networks.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.Wireless Sensor Networks (WSN), a new class of devices, has the potential to revolutionize
the capturing, processing, and communication of critical data at low cost. Sensor networks
consist of small, low-power, and low-cost devices with limited computational and wireless
communication capabilities. These sensor nodes can only transmit a finite number of
messages before they run out of energy. Thus, reducing the energy consumption per node for
end-to-end data transmission is an important design consideration for WSNs.
The Medium Access Control (MAC) protocols aim at providing collision-free access to the
wireless medium. MAC protocols also provide the most direct control over the utilization of
the transceiver, which consumes most of the energy of the sensor nodes.
The major part of this thesis is based on a proposed MAC protocol called Distributed
Receiver-oriented MAC (DRMACSN) protocol for code division multiple access (CDMA)
based WSNs. The proposed MAC protocol employs the channel load blocking scheme to
reduce energy consumption in the network. The performance of the proposed MAC protocol is verified through simulations for average
packet throughput, average delay and energy consumption. The performance of the proposed
MAC protocol is also compared to the IEEE 802.15.4 MAC and the MAC without the channel load sensing scheme via simulations.
An analytical model is derived to analyse the average packet throughput and average energy consumption performance for the DRMACSN MAC protocol. The packet success probability, the message success and blocking probabilities are derived for the DRMACSN
MAC protocol. The discrete-time multiple vacation queuing models are used to model the delay behaviour of
the DRMACSN MAC protocol. The Probability Generating Functions (PGF) of the arrivals
of new messages in sleep, back-off and transmit states are derived. The PGF of arrivals of
retransmitted packets of a new message are also derived. The queue length and delay expressions for both the Bernoulli and Poisson message arrival models are derived. Comparison between the analytical and simulation results shows that the analytical model is accurate. The proposed MAC protocol is aimed at having an improved average packet throughput, a reduced packet delay, reduced energy consumption performance for WSN
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Integrated Scheduling and Beam Steering for Spatial Reuse
This document describes an approach to integrating antenna selection and control into a time-division MAC scheduling process. I argue that through such integration it is possible to achieve greater spatial reuse and interference mitigation than by solving the two problems separately. Without coupling between the MAC scheduling and physical antenna configuration processes, a \u22chicken-and-egg\u22 problem exists: If antenna decisions are made before scheduling, they cannot be optimized for the communication that will actually occur. If, on the other hand, the scheduling decisions are made first, the scheduler cannot know what the actual interference and communications properties of the network will be.
This dissertation presents algorithms for optimal spatial reuse TDMA scheduling with reconfigurable antennas. I present and solve the joint beam steering and scheduling problem for spatial reuse TDMA and describe an implemented system based on the algorithms developed. The algorithms described achieve up to a 600% speedup over TDMA in the experiments performed. This is based on using an optimization decomposition approach to arrive at a working distributed protocol which is equivalent to the original problem statement while also producing optimal solutions in an amount of time that is at worst linear in the size of the input. This is, to the best of my knowledge, the first actually implemented STDMA scheduling system based on dual decomposition. This dissertation identifies and briefly address some of the challenges that arise in taking such a system from theory to reality