Showing papers by "Mehran Abolhasan published in 2007"

A survey on control separation techniques in multi-radio multi-channel MAC protocols

Abstract: The rapid diminishing in the cost of commodity wireless hardware in recent years has prompted the use of multiple radios to improve the capacity of wireless networks. However, the research has shown that the improvement obtained from using multiple radios does not solely depend on the number of radios, but primarily on how these radios can be integrated in a constructive manner. A common way of integration multiple radios is to use a dedicated radio for control. To date, a number of multi-radio MAC protocol are employing a dedicated radio to control and coordinate the other radios, though the approaches are varied from one to another. In this paper, the control separation techniques in the multi-radio multi-channel MAC have been surveyed, and a classification of control separation techniques is provided. Moreover, this study points out the open research issues and intends to spark new interests and developments in this field.

Dynamic zone topology routing protocol for MANETs

Abstract: The limited scalability of the proactive and reactive routing protocols have resulted in the introduction of new generation of routing in mobile ad hoc networks, called hybrid routing. These protocols aim to extend the scalability of such networks beyond several hundred to thousand of nodes by defining a virtual infrastructure in the network. However, many of the hybrid routing protocols proposed to date are designed to function using a common pre-programmed static zone map. Other hybrid protocols reduce flooding by grouping nodes into clusters, governed by a cluster-head, which may create performance bottlenecks or a single point of failures at each cluster-head node. We propose a new routing strategy in which zones are created dynamically, using a dynamic zone creation algorithm. Therefore, nodes are not restricted to a specific region. Additionally, nodes perform routing and data forwarding in a cooperative manner, which means that in the case failure, route recalculation is minimised. Routing overheads are also further reduced by introducing a number of GPS-based location tracking mechanisms, which reduces the route discovery area and the number of nodes queried to find the required destination. Copyright © 2006 AEIT

On Indoor Multi-hopping capacity of Wireless Ad-Hoc Mesh Networks

Abstract: The capacity and multi-hopping performance of ad hoc mesh networks in dynamic environment still remains an open research issue. Previous theoretical studies suggest that they do not scale in densely distributed networks. However, a study has shown that scalability and hence the multi- hopping capacity of mesh network is not only bound by the number of nodes in the network but also the number of hops [3]. In this paper we investigate the performance of multi- hop ad hoc mesh networks, using both simulation studies and an experimental test-bed, and monitor the performance of the network as the number of hops in the network increases. Our results show that the drop in performance in multi-hopping is much more significant when the traffic levels are high. Furthermore our test-bed study shows that ad hoc mesh networks can maintain high levels of packet delivery and throughput when traffic levels are low, however, the delay experienced continues to increase after each hop.

On Separating Route Control and Data Flows in Multi-radio Multi-hop Ad Hoc Network

Abstract: Ad hoc networks typically require a significant amount of routing and control information to be distributed in a timely and reliable manner throughout the network, particularly in dynamic environments. As traffic levels increase and the network becomes more heavily congested, there is an increased probability that these critical packets are lost, resulting in obsolete control information being used to make important decisions. This would further compound the problem of network congestion and lead to a very rapid loss of connectivity and throughput. Given this, we argue the solutions to these problems should not rely on putting extra bandwidth on a radio interface. Instead, we should exploit the use of multiple radios to ensure the route can be firmly established. In this paper, we propose a multi-radio solution which reserves one radio channel exclusively for routing. Our simulation results have demonstrated that using a separate radio for routing protocol would dramatically improve reliability in heavily loaded ad hoc wireless networks, thereby effectively alleviating the impact of network congestion.

Distributed MIMO systems using Asterism decoding

Abstract: Multiple Input Multiple Output (MIMO) systems have received enormous attention by researchers as they can provide a roughly linear increase in capacity of wireless communications systems by using multiple transmit and receive antennas. Even with the larger raw data rates provided by MIMO, the throughput of these systems can be limited by the number of users (or networks) sharing the medium. This paper shows how multiple users (or networks) transmitting simultaneously can be represented as a MIMO system with a larger number of transmit than receive antennas. After reviewing existing decoders for such a MIMO system, this paper then proposes applying an Asterism based decoder to distinguish between multiple users transmitting simultaneously. This produces a new multi-user access scheme that can be applied in addition to a primary access method, such as CSMA-CA.