Abraham O. Fapojuwo

A centralized energy-efficient routing protocol for wireless sensor networks

Wireless sensor networks consist of small battery powered devices with limited energy resources. Once deployed, the small sensor nodes are usually inaccessible to the user, and thus replacement of the energy source is not feasible. Hence, energy efficiency is a key design issue that needs to be enhanced in order to improve the life span of the network. Several network layer protocols have been proposed to improve the effective lifetime of a network with a limited energy supply. In this article we propose a centralized routing protocol called base-station controlled dynamic clustering protocol (BCDCP), which distributes the energy dissipation evenly among all sensor nodes to improve network lifetime and average energy savings. The performance of BCDCP is then compared to clustering-based schemes such as low-energy adaptive clustering hierarchy (LEACH), LEACH-centralized (LEACH-C), and power-efficient gathering in sensor information systems (PEGASIS). Simulation results show that BCDCP reduces overall energy consumption and improves network lifetime over its comparatives.

TDMA Scheduling with Optimized Energy Efficiency and Minimum Delay in Clustered Wireless Sensor Networks

In this paper, we propose a solution to the scheduling problem in clustered wireless sensor networks (WSNs). The objective is to provide network-wide optimized time division multiple access (TDMA) schedules that can achieve high power efficiency, zero conflict, and reduced end-to-end delay. To achieve this objective, we first build a nonlinear cross-layer optimization model involving the network, medium access control (MAC), and physical layers, which aims at reducing the overall energy consumption. We solve this problem by transforming the model into two simpler subproblems. Based on the network-wide flow distribution calculated from the optimization model and transmission power on every link, we then propose an algorithm for deriving the TDMA schedules, utilizing the slot reuse concept to achieve minimum TDMA frame length. Numerical results reveal that our proposed solution reduces the energy consumption and delay significantly, while simultaneously satisfying a specified reliability objective.

A Survey of Energy Efficient Resource Management Techniques for Multicell Cellular Networks

This paper surveys the recent findings in the area of energy efficient radio resource management in cellular networks. The primary objective is to identify and evaluate the key techniques that have the highest energy saving potential to be developed in the context of Green Networks while serving as a guideline for future research endeavours. The focus of the paper is targeted towards multicell networks which are composed of multiple BSs co-existing in the same area sharing the available radio resources. Due to this, greater emphasis is given towards the techniques that take inter-cell interference (ICI) into account while allocating the resources and, in the process, maximize the energy efficiency (EE). The resource management solutions presented in the paper are classified under three network domains namely homogeneous, heterogeneous, and cooperative networks. Furthermore, the analytical techniques for characterizing the EE of multicell networks are discussed in terms of the stochastic geometry framework. Finally, the paper outlines the current challenges and open issues in the area of energy efficient resource management for multicell cellular networks.

A Survey of System Architecture Requirements for Health Care-Based Wireless Sensor Networks

Wireless Sensor Networks (WSNs) have emerged as a viable technology for a vast number of applications, including health care applications. To best support these health care applications, WSN technology can be adopted for the design of practical Health Care WSNs (HCWSNs) that support the key system architecture requirements of reliable communication, node mobility support, multicast technology, energy efficiency, and the timely delivery of data. Work in the literature mostly focuses on the physical design of the HCWSNs (e.g., wearable sensors, in vivo embedded sensors, et cetera). However, work towards enhancing the communication layers (i.e., routing, medium access control, et cetera) to improve HCWSN performance is largely lacking. In this paper, the information gleaned from an extensive literature survey is shared in an effort to fortify the knowledge base for the communication aspect of HCWSNs. We highlight the major currently existing prototype HCWSNs and also provide the details of their routing protocol characteristics. We also explore the current state of the art in medium access control (MAC) protocols for WSNs, for the purpose of seeking an energy efficient solution that is robust to mobility and delivers data in a timely fashion. Furthermore, we review a number of reliable transport layer protocols, including a network coding based protocol from the literature, that are potentially suitable for delivering end-to-end reliability of data transmitted in HCWSNs. We identify the advantages and disadvantages of the reviewed MAC, routing, and transport layer protocols as they pertain to the design and implementation of a HCWSN. The findings from this literature survey will serve as a useful foundation for designing a reliable HCWSN and also contribute to the development and evaluation of protocols for improving the performance of future HCWSNs. Open issues that required further investigations are highlighted.

Analysis of Common Radio Resource Management Scheme for End-to-End QoS Support in Multiservice Heterogeneous Wireless Networks

Future-generation wireless networks will consist of heterogeneous radio access technologies (RATs) with Internet Protocol-based infrastructure and support multiple bearer services having different quality-of-service (QoS) requirements. However, a major issue is how to jointly utilize the resources in the different RATs in an efficient manner while simultaneously achieving the desired QoS and minimizing the service cost from both the user and service provider perspectives. To resolve this issue, this paper proposes an adaptive common radio resource management (CRRM) scheme in the context of CDMA2000 and IEEE 802.11 wireless technologies, which are examples of todays wireless wide-area network (WWAN) and wireless local area network (WLAN) RATs, respectively. The key parameters of the scheme, i.e., service type, user mobility and location information, and service cost, are described. The effectiveness of the proposed CRRM scheme is analytically assessed using the theory of Markov chains. Numerical results show that the proposed CRRM scheme minimizes the rate of unnecessary vertical handoffs, thereby providing stable communication without degrading call-blocking probabilities in all mobility and loading scenarios considered. The proposed CRRM scheme also minimizes service cost, which makes it attractive for implementation in heterogeneous wireless networks.

A new call admission control method for providing desired throughput and delay performance in IEEE802.11e wireless LANs

The draft IEEE 802.11e standard aims at providing quality of service (QoS) support in 802.11 wireless local area networks (WLANs). Enhanced distributed coordination function (EDCF), being the fundamental medium access control mechanism in IEEE 802.11e, can only provide service differentiation but offers no QoS guarantees. While service differentiation does not perform well under high traffic load conditions, call admission control (CAC) becomes necessary in order to provide and support the QoS of existing calls. In this paper, we first analyze the saturation throughput and mean access delay performance of differentiated service provided by EDCF. Specifically, we investigate the impact of transmission opportunity (TXOP) and wireless channel errors on the performance of the EDCF. Based on the results from this analysis, we propose a new CAC algorithm that provides the desired throughput and access delay performance. Simulated performance results demonstrate the effectiveness of the proposed CAC algorithm

Stochastic processes for computer network traffic modeling

Computer networks such as local area and wide area networks possess complex characteristics due to the heterogeneous nature of the supported traffic. The network traffic exhibits highly irregular fractal-like structure and long term correlations. Various stochastic processes such as fractional Gaussian noise, multiplicative cascades, linear fractional stable motion have been proposed to model network traffic. These stochastic processes are relatively unheard of in the networking community, until recently. This paper provides a thorough review of these stochastic processes and their application to wireless traffic modeling.

Performance Analysis and Parameter Optimization of Random Access Backoff Algorithm in LTE

This paper studies the performance of random access backoff algorithm in Long Term Evolution (LTE) system, taking the physical loss into account. Analytical results are developed for system performance metrics including throughout, drop probability and medium access delay. All these analytical results are verified with simulation. Performance of the backoff algorithm under different parameter settings is compared in a typical scenario of LTE. The performance results provide useful insights on optimal backoff parameter settings. For example, under a physical loss probability of 1%, the optimal backoff window size should be set to 1 and the attempt limit set to 2 or 3.

Energy consumption and message delay analysis of QoS enhanced base station controlled dynamic clustering protocol for wireless sensor networks

This paper proposes and analyzes a Quality of service enhanced Base station Controlled Dynamic Clustering Protocol (QBCDCP), suitable for the support of video and imaging traffic over resource constrained wireless sensor nodes. The protocol achieves energy efficiency through a rotating head clustering approach and delegation of energy-intensive tasks to a high-power base station, while providing quality of service (QoS) support by including delay and bandwidth parameters in the route selection process. A Time Division Multiple Access (TDMA) scheme is used for intra- and intercluster communication, providing bandwidth reservation. Performance of QBCDCP is evaluated in terms of energy consumption and end-to-end image delay via analytical and discrete-event simulation techniques. Numerical results provide insights on the selection of network parameters such as number of clusters that improve the sensing node lifetime while maintaining high quality of service. The results also demonstrate the trade-off between end-to-end image delay and sensor node lifetime.

Modeling and characterization of frame loss process in IEEE 802.11 wireless local area networks

The popularity of 802.11-based WLANs is greatly increasing and to keep up with new throughput demands the interaction of some of the protocols (MAC and TCP) is being scrutinized. In order to properly simulate protocol behavior, accurate frame loss models are needed for 802.11 networks. This paper discusses measurements taken to help characterize the frame loss process and compares Markov models with different numbers of states whose parameters have been estimated using the Baum-Welch algorithm. It is shown that higher-order state hidden Markov models provide a better fit to measured data than the traditional 2-state Gilbert models.