Pragasen Mudali

Design and implementation of a topology control scheme for Wireless Mesh Networks

The Wireless Mesh Network (WMN) backbone is usually comprised of stationary nodes but the transient nature of wireless links results in changing network topologies. Topology Control (TC) aims to preserve network connectivity in ad hoc and mesh networks and an abundance of theoretical results on the effectiveness of TC exist. Practical evaluations of TC schemes that provide gradual transceiver power adjustments for the WMN backbone are however in their infancy. In this paper we investigate the feasibility of power control in a popular WMN backbone device and design and evaluate an autonomous, light-weight TC scheme called PlainTC. An indoor test-bed evaluation shows that PlainTC is able to maintain network connectivity, achieve significant transceiver power savings and reduce MAC-level contention but that no significant reductions in physical layer interference were realised. The evaluation has also highlighted the danger of associating power savings with network lifetime. Further larger-scale experiments are required to confirm these results.

Performance evaluation of routing protocols in uniform and normal node distributions using inter-mesh wireless networks

Wireless Mesh Networks (WMNs) is a promising technology which has a potential of providing inexpensive solutions to a wide range of applications. These networks have been applied in the context of home, community, and enterprise scenarios. The nodes in these application scenarios can be distributed either in a uniform or normal fashion. The key issue is for the network to continuously manage and share the resources regardless of the node location within the network. However, it is not clear how individual node position relative to the Internet gateway and networks center affect the wireless mesh networks performance. Hence, this research paper evaluates AODV, OLSR, and HWMP routing protocols in normal and uniform node distribution in inter-mesh wireless networks. Three performance metrics were considered; throughput, packet delivery ratio, and end to end delay.

A testbed evaluation of energy-efficiency of routing protocols in battery-powered wireless mesh networks

Wireless mesh networks have been shown to be an appropriate technology for rural areas. However, in most African countries, electricity is scarce in rural areas. A candidate solution to the power-constraint problem in these areas is the use of solar/battery-powered nodes. Different protocols at different layers have varying effects on the energy consumption of the nodes. However, it is not clear how these protocols affect the energy consumption of a battery-powered node in a testbed environment. This paper evaluates the influence of AODV and OLSR on the lifetime of battery-powered nodes when subjected to different transmission power levels and payload sizes. An indoor testbed evaluation indicates that OLSR at maximum transmission power with maximum payload outperform others with regards to packet delivery ratio, average throughput and average energy cost per bit. Whilst AODV at minimum transmission power with maximum payload performs best with regards to the node lifetime.

Evaluating the energy-efficiency of transport layer protocols in a battery-powered wireless mesh networks

Wireless mesh networks have been shown to be an appropriate technology for rural areas. However, in most African countries, electricity is scarce in rural areas. A candidate solution to the power-constraint problem in these areas is the use of solar/battery-powered nodes. Different protocols at different layers have varying effects on the energy consumption of the nodes. However, it is not clear how these protocols affect the energy consumption of a battery-powered node in a testbed environment. This paper evaluates the influence of TCP and UDP on the lifetime of battery-powered nodes when subjected to different transmission power levels and payload sizes. An indoor testbed evaluation shows that UDP at maximum transmission power with minimum payload performs best with regards to the node lifetime, TCP at maximum payload with maximum transmission power performs best with regards to packet delivery ratio and throughput and TCP at maximum transmission power with minimum payload consumes the least transmission energy. (6 pages)

Performance analysis of Mesh Access Points placement schemes using rural settlement patterns

Internet connectivity in most rural African areas has been viewed as a major challenge due to lack of reliable power, scarcity of network expertise and expensive installation of network equipment. With the rapid development of wireless technologies, Wireless Mesh Network (WMN) has emerged as a promising networking infrastructure, bridging the digital divide between the urban and rural areas. However, during the deployment of a WMN, the placement of Mesh Access Points (MAPs) is an important design issue which drastically influences the network performance. The MAPs placement problem has been investigated and various placement methods have been proposed. However, the effectiveness of the existing MAPs placement schemes have not been evaluated and compared in Rural Settlement Patterns. Hence, this paper analyses the performance of different MAPs placement schemes in four rural settlement patterns: dispersed, nucleated, isolated and linear settlement pattern. The simulation result shows that the Hill Climbing placement scheme in the dispersed and nucleated settlement patterns outperformed other schemes in the achieved throughput, packet delivery ratio and end-to-end delay. While Virtual force placement scheme in the linear settlement pattern outperformed others and Time-efficient Local Search outperforms other schemes in the isolated settlement pattern.

Biologically-Inspired Foraging Decision Making in Distributed Cognitive Radio Networks

The dynamic spectrum management techniques have been introduced to address the current Radio Frequency bands inefficiency challenges. Cognitive Radio (CR) technology has been regarded as the most promising technology in the dynamic spectrum management area. One of the major aspects of the spectrum management is the decision making ability of CR users. The dynamic reconfiguration of both the operating frequency and channel bandwidth in a distributed CR network has not received sufficient attention despite their importance in spectrum decision making. Few research works have attempted to address the dynamic reconfiguration of frequency and channel bandwidth problems using various approaches. However, due to certain challenges such as high computational complexity, ambiguity, repeatability and the lack of optimality with the existing approaches, researchers are still trying to explore newer methods that can achieve optimal spectrum management. Hence, this paper presents a biologically-inspired optimal foraging model for dynamic reconfiguration of frequency and channel bandwidth in a distributed cognitive mobile adhoc network. One of the main advantages of biologically-inspired foraging model is its analytical simplicity and optimum solution. The mean efficiency and Distance travelled by SUs before finding available frequency were measured. The two metrics were measured when subjected to different SUs positions and Giving-Up Time. It was generally observed that the SUs perform better when 0 < Xo ≤ 0.2 and GUT ≤ 50 in the achieved mean efficiency and distance travelled to find available frequency.

Design considerations of a topology control prototype for Wireless Mesh Networks

Topology Control has been shown to produce beneficial outcomes when applied to wireless ad-hoc networks. Wireless Mesh Networks (WMNs) may also benefit from the use of TC in its backbone network but the actual extent of the benefit remains unknown as prototype studies are rare. In this paper we distill our experiences developing two TC prototypes into a set of design criteria for TC prototypes intended for the WMN backbone. A case study of the PlainTC+ prototype is also provided. The case study explores the design decisions taken in order for the prototype to satisfy the various design criteria provided. It is hoped that the case study will provide a practical starting point for future prototypes.

Performance analysis of mesh portal points placement schemes for Rural Settlement Patterns

Internet connectivity in most rural African areas has been viewed as a major challenge due to lack of reliable power, scarcity of network expertise and expensive installation of network equipment. With the rapid development of wireless technologies, Wireless Mesh Networks (WMN) has emerged as a promising networking infrastructure, bridging the digital divide between the urban and rural areas. However, during the deployment of a WMN, the placement of Mesh Access Points and Mesh Portal Points (MPPs) is an important design issue which drastically influences the network performance. The Mesh Points (MPs) placement problem has been investigated and various placement methods have been proposed. However, the effectiveness of the existing MPPs placement schemes have not been evaluated and compared in Rural Settlement Patterns. Our previous study addressed the MAPs placement problem in rural settlement patterns, and the result was used as the basis for MPPs placement. Hence, this paper analyses the performance of different MPPs placement schemes in the dispersed, nucleated, isolated and linear settlement patterns. The simulation result shows that the Multi-hop Traffic-flow Weight placement scheme performed best in the linear and nucleated settlement patterns, the Grid-based placement scheme performed best in the dispersed settlement pattern and the Incremental clustering scheme performed best in the isolated settlement pattern.

Context-Based Topology Control for Wireless Mesh Networks

Topology Control has been shown to provide several benefits to wireless ad hoc and mesh networks. However these benefits have largely been demonstrated using simulation-based evaluations. In this paper, we demonstrate the negative impact that the PlainTC Topology Control prototype has on topology stability. This instability is found to be caused by the large number of transceiver power adjustments undertaken by the prototype. A context-based solution is offered to reduce the number of transceiver power adjustments undertaken without sacrificing the cumulative transceiver power savings and spatial reuse advantages gained from employing Topology Control in an infrastructure wireless mesh network. We propose the context-based PlainTC

Using node position to improve the robustness of the IEEE 802.11s authentication mechanism for wireless mesh networks

Wireless Mesh networks (WMNs) are gaining popularity as a scalable replacement for Wired Network infrastructure. The increasing popularity of WMNs has prompted the development of security mechanisms. The newly-ratified IEEE 802.11s mesh networking standard specifies a security mechanism that builds upon the IEEE 802.11i security standard meant for wireless local area networks. The IEEE 802.11s security mechanism specifies the existence of a single Mesh key Distributor (MKD) which helps to authenticate new nodes that join the network However, there is no mechanism for selecting a new MKD if the current MKD is unreachable or has failed. This scenario can arise due to the dynamic nature of WMN backbone topologies, wireless link variability in deployed networks and battery depletion in battery-powered WMNs. MKD selection in a disperse settlement where WMN infrastructure could be deployed can be performed by adapting the position-based Leader Selection Algorithms from Wireless Sensor Networks. This paper evaluates the influence of distance and event position-based leader selection algorithms on MKD selection when subjected to different rounds and network sizes. The evaluation showed that the event-based algorithms (EDC & EECED) outperform the distance-based algorithms (EDBCP & EDBC) in the achieved performance for communication overhead cost, leader selection delay and the energy consumption rate.