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. 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. Disciplines Physical Sciences and Mathematics
This paper investigates the relative performance of unicast and broadcast traffic traversing a one-hop ad hoc network utilising the 802.11 DCF. An extended Markov model has been developed and validated through computer simulation, which successfully predicts the respective performance of unicast and broadcast in a variety of mixed traffic scenarios. Under heavy network traffic conditions, a significant divergence is seen to develop between the performance of the two traffic classes -in particular, when network becomes saturated, unicast traffic is effectively given higher precedence over broadcast. As a result, the network becomes dominated by unicast frames, leading to poor rates of broadcast frame delivery.
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 multiradio 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. 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 multiradio 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. Disciplines Physical Sciences and Mathematics
This conference paper was originally published as Abolhasan, M., Wang, J. C.-P., Franklin, D. R., On indoor multi-hopping capacity of wireless ad-hoc mesh networks, IEEE International Conference on Mobile Adhoc and Sensor Systems MASS 2007, 8-11 Oct, 1-6. On indoor multi-hopping capacity of wireless ad-hoc mesh networks AbstractThe 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 multihopping 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 multihop 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. Disciplines Physical Sciences and Mathematics Publication DetailsThis conference paper was originally published as Abolhasan, M., Wang, J. C.
Abstract-Performance evaluations of multi-hop ad hoc network routing protocols have been primarily conducted through analytic and simulation-based studies, which frequently fail to accurately predict real-world performance and behaviour. One reason for this is the challenge in developing low cost, representative test beds with the degree of flexibility and mobility required. We have developed a Portable Wireless Ad hoc Node (PWAN) device which establishes multi-hop routes using the OLSR routing protocol. The PWAN's performance has been investigated using two test bed configurations to evaluate its capacity under conditions of high node density in a short-range, multi-hop environment. Our results illustrate that such networks are capable of providing high quality connections when traffic density is low. However, the network link quality deteriorates dramatically as the traffic level increases, and the network topology becomes unstable until the traffic level is reduced.
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