Thomas Olwal

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.

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.

Beam steering for circular switched parasitic arrays using a combinational approach

In this paper we present a method of electronic beam steering for circular switched parasitic array (SPA) antennas. In circular SPA antennas, one achieves azimuth beam steering by open-circuiting and short-circuiting different parasitic elements, usually with only one parasitic element open-circuited at a time. For the SPA antenna with few parasitic elements, this results in low azimuth beam steering resolution. In the proposed method, we iterate through different combinations of parasitic elements and the possible switch states of the lumped impedance loads connected to the parasitic elements. Our method aims to increase the azimuth beam steering resolution of the circular SPA antennas. The method is verified using a combination of simulation (using both MATLAB and WIPL-D) and a SPA antenna prototype implementation. The MATLAB code uses the induced EMF method, while the WIPL-D uses the Methods of Moment (MoM) for solving the antenna impedances. The three sets of results (simulations and measurement) match very well at 2.4 GHz. The results indicate the availability of more options (different loading configurations) for electronic beam switching that can be adopted to improve the beam steering resolution of circular SPA antennas.

Optimal Control of Transmission Power Management in Wireless Backbone Mesh Networks

Wireless Mesh Networks, Book edited by: Nobuo Funabiki, ISBN: 978-953-307-519-8, Publisher: InTech, Publishing date: January 2011

Available bandwidth-aware cell selection for expanded regions of small cells adopting ABS

Cell selection in current LTE-Advanced depend on reference signal received power or reference signal received quality which results to low user association probability. Therefore, we propose an aggregate objective cell selection technique based on enhanced inter-cell interference coordination technique developed by 3GPP in Rel-10 known as almost blank subframe. We also adopt the use of cell range expansion technique as means to encourage offloading. Cell range expansion was introduced in LTE-advanced, it encourages user equipment to select a small cell with a weakest signal as thier serving cell by adding a positive bias in cell selection process. Simulation shows that the proposed scheme results to high user association probability, while giving superior performance in average throughput compared to conventional single objective base cell selection for cell range expansion.

Coupled interference based rate adaptation in ad hoc networks

Link adaptation provides an efficient and flexible strategy to adapt transmission rates based on channel conditions. To attain distributed optimal local and global utility, network interference need to be mitigated therein allowing the users to transmit at the minimum transmission power enough to sustain connectivity. This paper proposes coupled interference network utility maximization (NUM) strategy (i.e., CIN) for rate adaptation in WLANs that is solved using “reverse-engineering” based on Karush-Kuhn-Tucker (KKT) conditions. In that way, users determine data rates based on their local link observations (i.e., coupled interference). Both pricing and limited message passing mechanisms are employed in the NUM so that pricing restrict users from self-interest behaviours while limited message passing assists users to announce their prices and transmit powers. It is demonstrated theoretically that CIN satisfies the conditions of the super-modular games, thereby resulting in an optimal solution. Simulation results have shown that adapting data rates based on the link conditions can improve the performance of ad hoc networks for both stationary and mobile users.

Achievable capacity limit of high performance nodes for wireless mesh networks

Copyright: 2012 Olwal et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Enhanced SWEET protocol for energy efficient wireless sensor networks

SWEET routing protocol is one of the many protocols developed for cluster formation and routing in wireless sensor networks. The SWEET protocol is a decentralized clustering protocol, it uses timers and interim updated cluster head estimation probability. This paper focus on the details of the initialization waiting time, sleeping mode and base station in order to increase the life cycle of the network. The initial waiting times resizing procedure is carried by a weighting factor which is computed from the delay slot time and delay frame time. Other improvements are the introduction of sleeping mode energy saving technique. The last contribution is through the enabled base stations ability to become a cluster head. A simulation based performance evaluation of our proposed EN-SWEET protocol shows superiority in energy efficiency.

The FIREMAN: Foraging-Inspired energy management in multi-radio Wi-Fi networks

The tremendously rapid evolution of wireless networks into the next generation heterogeneous broadband and mobile networks has necessitated the emergence of the multiradio, wireless infrastructure. These wireless infrastructural technologies have been designed in such a manner so as to enable them be self-organized, self-configured, reliable and robust, with a capacity that sustains high traffic volumes and long “online” time. However, the desired networking and complex features have resulted in unnecessary network energy consumption, impacting negatively on the economy, environment and the ICT markets. In order to reduce the potential energy consumption in these networks, this paper proposes a novel energy management scheme based on behavioral ecology. Inspired by the applied foraging theory, whereby a solitary forager in a random ecosystem makes optimal decisions that maximizes its energy (nutrients) consumption, survival probability and lifetime; a Foraging-Inspired Radio-Communication Energy Management (FIREMAN) method has been developed. The FIREMAN method achieves both optimal energy consumption and lifetime in multi-radio Wi-Fi networks. The efficacy of the new method has been extensively validated through computer simulations of the energy and throughput performance.