Showing papers by "Mehran Abolhasan published in 2009"

Real-world performance of current proactive multi-hop mesh protocols

Abstract: The proliferation of mesh or ad hoc network protocols has lead to a push for protocol standardisation. While there are a number of both open-source and proprietary mesh routing protocols being developed, there is only a small amount of literature available that shows relative strengths and weaknesses of different protocols. This paper investigates the performance of a number of available routing protocols using a real-world testbed. Three routing protocols — Optimised Link State Routing (OLSR), Better Approach To Mobile Ad hoc Network (B.A.T.M.A.N.) and BABEL — were chosen for this study. Our investigations focus on the multi-hopping performance and the ability of each routing protocol to recover from link failures. Our results show that B.A.T.M.A.N. and BABEL outperform OLSR both in terms of multi-hopping performance and in route re-discovery latency.

On Optimising Route Discovery in Absence of Previous Route Information in MANETs

Abstract: This paper present a new routing protocol for Ad hoc networks, called On-demand Tree-based Routing Protocol (OTRP). This protocol combines the idea of hop-by-hop routing such as AODV with an efficient route discovery algorithm called Tree-based Optimized Flooding (TOF) to improve scalability of Ad hoc networks when there is no previous knowledge about the destination. To achieve this in OTRP, route discovery overheads are minimized by selectively flooding the network through a limited set of nodes, referred to as branching-nodes. The theoretical analysis and simulation results showed that OTRP outperforms AODV, DYMO, and OLSR and it reduces overheads as number of nodes and traffic increase.

Characterising the Behaviour of IEEE 802.11 Broadcast Transmissions in Ad Hoc Wireless LANs

Abstract: This paper evaluates the performance of the IEEE 802.11 broadcast traffic under both saturation and nonsaturation conditions. The evaluation highlights some important characteristics of IEEE 802.11 broadcast traffic as compared to corresponding unicast traffic. Moreover, it underlines the inaccuracy of the broadcast saturation model proposed by Ma and Chen due to the absence of backoff counter freeze process when channel is busy. Computer simulations are used to validate the accuracy of the new model and demonstrate the importance of capturing the freezing of backoff counter in the analytical study of IEEE 802.11 broadcast.

Distributed energy efficient unequal clustering algorithm for wireless sensor networks

Abstract: A distributed energy-efficient unequal clustering (DEEUC) algorithm was proposed for wireless sensor net-works by research current routing algorithms. The core of DEEUC has three parts. Firstly, when tentative clusterheads are selected, an average energy factor was introduced to balance the residual energy of the whole network nodes so that it may improve the network energy efficiency. Secondly, an energy consumption ratio function was proposed to balance energy-efficient of each node. Finally, an unequal clustering algorithm was proposed for single-hop homogeneous networks. Through both theoretical analysis and numerical results, it is shown that DEEUC prolongs the network lifetime significantly against the other clustering protocols such as LEACH-C and EECS. Under general instance, DEEUC may prolong the lifetime up to 30% against EECS.

An energy-efficient adaptive clustering algorithm for wireless sensor networks

Abstract: In this paper, we consider a network of energy constrained sensors deployed over a region. Each sensor node in such a network is systematically gathering and transmitting sensed data to a base station (via clusterheads). This paper focuses on reducing the power consumption of wireless sensor networks. We first extend LEACH's stochastic clusterhead selection algorithm by an average energy-based (LEACH-AE) deterministic component to reduce energy consumption. And then an unequal clustering idea is introduced to further reduce energy consumption of clusterheads. Simulation results show that our modified scheme can extend the network life by up to 38% before the first node dies in the network. Through both theoretical analysis and numerical results, it is shown that the proposed algorithm achieves better performance than the existing clustering algorithms such as LEACH, DCHS, LEACH-C.

OLSR-R 3 : Optimised link state routing with reactive route recovery

Abstract: The Optimised Link State Routing (OLSR) is a proactive routing protocol which relies on periodical broadcast of routing packets. However, due to the one-to-many relationship of broadcast traffic, the delivery of these packets can not be guaranteed by underlying MAC protocol, particularly in a congested condition. In this paper, the possible routing pathologies and failures of OLSR in a congested network are explored. In addition, a hybrid routing protocol which integrates OLSR with Reactive Route Recovery (OLSR-R3) is proposed to rectify the erratic routing behaviour described in this paper. Simulation studies are presented which show that the proposed solution is effective in addressing the underlining problems.

Serially Concatenated Turbo Codes

Abstract: The paper presents a new scheme of concatenated codes, referred to as Serially Concatenated Turbo (SCT) codes. The code is constructed as the serial combinations of two turbo codes, i.e. turbo Recursive Systematic Convolutional (RSC) codes and turbo Bose Ray Chaudhuri Hocquenghem (BCH) codes, linked by a pseudo-random interleaver. In comparison with the conventional turbo RSC codes, SCT codes have higher minimum distance values. Based on conducted simulations, it is found that SCT codes outperform turbo RSC codes at the waterfall and error floor regions, while they require reasonable number of iterations at their iterative decoding structure to achieve good performance.

End-to-End path stability of reactive routing protocols in IEEE 802.11 ad hoc networks

Abstract: Over the years, a considerable research effort has been applied to the design of ad hoc network routing protocols. However, there is still a lack of understanding of the subtle interactions between routing protocols and lower layers in the protocol stack. In this paper, the instability which may arise when reactive routing protocols interact with the IEEE 802.11 MAC protocol is investigated. In particular, several erratic behaviours of the Ad hod On-demand Distance Vector (AODV) routing protocol in a congested IEEE 802.11 ad hoc network are demonstrated. A cross-layer solution is proposed based on an Adaptive Bulk Trigger policy and a Dynamic Window Selection scheme. Simulation studies are presented which show that the proposed solution is effective in alleviating erratic behaviour of AODV and improving the end-to-end path stability.

Routing metric for multi-interface and power-aware nodes in heterogeneous MANETs

Abstract: This paper presents Heterogeneity Ratio (HR) as a new routing metric for heterogeneous MANETs. This metric is the ratio of number of powerful nodes to hop count that is used to select the best path to destination. Node heterogeneity is modeled in terms of: types and number of different interfaces, power, and transmission ranges. Our proposed routing metric is based on developing route discovery algorithm that is implemented on the top of On-demand Tree-based Routing Protocol (OTRP)[2] to accommodate nodes heterogeneity. Simulation results show that using HR with OTRP Heterogeneity Aware outperforms other metrics like minimal hop count and maximal number of powerful nodes.