Ntsibane Ntlatlapa

Dynamic Power Control for Wireless Backbone Mesh Networks: a Survey

With the tremendous growth of wireless networks into the next generation to provide better services, Wireless Mesh Networks (WMNs) have emerged to offer ubiquitous communication and seamless broadband applications. WMNs are hybrid networks composed of a mixture of static Wireless Mesh Routers (WMRs) and mobile Wireless Mesh Clients (WMCs) interconnected via wireless links to form a multi-hop wireless Ad Hoc network (WANET). WMNs are self-organized, self-configured, and reliable against single points of failures, and robust against RF interference, obstacles or power outage. This is because WMRs forming wireless backbone mesh networks (WBMNs) are built on advanced physical technologies. Such nodes perform both accessing and forwarding functionality. They are expected to carry huge volumes of traffic and be “on power” at all times. While trying to increase network capacity, problems of the dynamic transmission power control (DTPC) arise in such networks. Such problems include RF Interference, Connectivity and energy-depletion. While there are numerous studies on this topic, contributions in the context of WBMNs are still challenging but interesting research areas. This paper provides an overview of the DTPC algorithms central to the WBMNs framework. The open issues are also highlighted.

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.

Interference-aware power control for Multi-Radio Multi-Channel wireless mesh networks

Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. In this paper, we present a dynamic power control for MRMC WMNs. First, WMN is represented as a set of disjoint Unified Channel Graphs (UCGs). Second, each radio assigned to a unique UCG adjusts the transmission power locally using predicted interference states among different adjacent UCGs. A new power selection MRMC unification protocol (PMMUP) is proposed that coordinates local power optimizations at the radios of a node. The throughput and energy performance of the proposed method is investigated through simulations.

Autonomous Transmission Power Adaptation for Multi-Radio Multi-Channel Wireless Mesh Networks

Multi-Radio Multi-Channel (MRMC) systems are key to power control problems in WMNs. Previous studies have emphasized throughput maximization in such systems as the main design challenge and transmission power control treated as a secondary issue. In this paper, we present an autonomous power adaptation for MRMC WMNs. The transmit power is dynamically adapted by each network interface card (NIC) in response to the locally available energy in a node, queue load, and interference states of a channel. To achieve this, WMN is first represented as a set of Unified Channel Graphs (UCGs). Second, each NIC of a node is tuned to a UCG. Third, a power selection MRMC unification protocol (PMMUP) that coordinates Interaction variables (IV) from different UCGs and Unification variables (UV) from higher layers is proposed. PMMUP coordinates autonomous power optimization by the NICs of a node. The efficacy of the proposed method is investigated through simulations.

Improved Distributed Dynamic Power Control for Wireless Mesh Networks

One of the main objectives of transmission power control (TPC) in wireless mesh networks (WMNs) for rural area applications is to guarantee successful packet transmission and reception (SPT-R) with low power consumption. However, the SPT-R depends on co-channel multiple access interferences (MAI) including the effects from hidden terminals. In this paper we investigate how MAI can be minimized through a MAC-dependent transmission scheduling probability (TSP) model. In what follows, we show how a distributed scheduling probability model improves the dynamic power control algorithm. The resulting optimal power control is derived from a network centric objective function. The analytical results show that transmit power solutions converge to a unique fixed point. The simulation results show that a high average feasibility rate, given a coexistence pattern, can be achieved. There is significant average transmission power savings compared to conventional methods.

Towards energy efficient mobile communications

The rapid growth and development of wireless communication services and applications corresponds to an increase in associated energy consumption. For broadband wireless network deployment in rural areas affected by unreliability and unavailability of national grid electricity supply, energy efficiency becomes a major design criterion to be considered. In such areas, diesel powered generators are normally used as the main power source, while batteries become the most preferred source of energy to power wireless communication devices. In order to address increasing energy requirements, we propose an energy saving technique for mobile stations (MSs) operating under the wireless broadband access systems in this paper. Our proposed scheme is limited to the power saving class (PSC) of Type I in IEEE 802.16. Our numerical results show that more energy can be saved if the listening interval is considered under non-sleep or awake mode.

Scalable power selection method for Wireless Mesh Networks

This paper addresses the problem of a scalable dynamic power control (SDPC) for Wireless Mesh Networks (WMNs) based on IEEE 802.11 standards. An SDPC model that accounts for architectural complexities witnessed in multiple radios and hops communication system is designed. The key contribution is that we have first developed a general multiple transmission activity (MTA) model for each radio link. We then present a power selection policy that depends on average cross-layer network fluctuations as opposed to instantaneous fluctuations. Through simulations, we have observed that the SDPC modelled at the link layer, with the knowledge of imperfect and often delayed information, can significantly yield much power savings.

Adaptive Priority Based Distributed Dynamic Channel Assignment for Multi-radio Wireless Mesh Networks

This paper investigates the challenges involve in designing a dynamic channel assignment (DCA) scheme for wireless mesh networks, particularly for multi-radio systems. It motivates the need for fast switching and process coordination modules to be incorporated in DCA algorithm for multi-radio systems. The design strategy is based on a reinterpretation of an adaptive priority mechanism as an iterative algorithm that recursively allocate a set of channels to radios in a fair and efficient manner in order to minimise interference and maximise throughputs. The algorithm, called Adaptive Priority Multi-Radio Channel Assignment (APMCA) is tested for overall performance to assess the effectiveness by determining its overall computational complexity. The combined advantages of fast switching time and process coordination modules make the APMCA a useful candidate towards automating the channel assignment method in multi-radio wireless mesh network planning and design.