A Channel based Fair Scheduling Scheme for Downlink Data Transmission in TD-CDMA Networks

High speed data transmission in wireless networks demands better radio resource management schemes. A fair packet scheduling is proposed for downlinks of a cellular TD-CDMA system for delay-tolerant applications. It is based on the combined consideration of channel conditions, required throughput and achieved average throughput. A system dependent parameter is introduced to control the maximum achievable date rate as well as the degree of fairness. Through analysis and simulation, we study the tradeoff between system throughout (i.e., efficiency) and individual throughput (i.e., fairness). The relative performance between the proposed scheme and the traditional schemes is evaluated through simulation to confirm the analytical observations. The sensitivity of the system tolerance factor towards efficiency and fairness is also investigated.

Mesh adaptive direct search approach for D2D resource management

Device‐to‐device (D2D) communications are being considered a way forward to achieve higher data rate targets for futuristic wireless networks. D2D introduces interference among cellular users and D2D users. A joint resource allocation (JRA) strategy in cellular network with D2D functionality can definitely enhance overall data rate. The strategy under consideration maximizes the overall data rate of cellular network besides meeting threshold of power and interference constraints. The JRA is a class of mixed integer non‐linear constraint optimization problems and is NP hard. Because of discrete nature of variables in the problem, optimal solution performs extensive search of integer variables, and problem becomes exponentially complex with the increasing number of user pairs. In this paper, mesh adaptive direct search algorithm is applied to solve the aforementioned problem. The algorithm is suitable for complex problems of combinatorial nature to solve the JRA strategy in D2D. The proposed algorithm converges to optimal solution within acceptable computational iterations. Simulation results of system capacity and interference also demonstrate the suitability of the proposed approach viz‐a‐viz other algorithms. Copyright © 2016 John Wiley & Sons, Ltd.     

On the Performance of a Constellation-rotated Time-spreaded Space-frequency Coding Scheme for 4 × 1 MISO OFDM Transceivers

In this article, we propose a time-spreaded quasi-orthogonal space-frequency coded OFDM system with constellation rotation. A constellation rotated quasi-orthogonal OFDM system could offer full rate and full diversity in a frequency selective fading channel. Time spreading can give additional time diversity gain in a fast fading channel. Assuming that complex channel gains between adjacent subcarriers are approximately equal, we develop a coding scheme for 4 × 1 MISO transceiver and its BER performance is evaluated for different Doppler frequencies in an OFDM system. The simulation results show that 2 dB gain can be achieved at BER of 10⁻³ using the proposed scheme compared to a scheme without time spreading and constellation rotation when 512 subcarriers are used at maximum Doppler frequency of 300 Hz. Also, the proposed system is analyzed for different delay spread of the channel and the results show that if adjacent subcarriers are correlated, it is better in SF-OFDM decoding.     

A unified analytical framework for distributed variable step size LMS algorithms in sensor networks

Internet of Things (IoT) is helping to create a smart world by connecting sensors in a seamless fashion. With the forthcoming fifth generation (5G) wireless communication systems, IoT is becoming increasingly important since 5G will be an important enabler for the IoT. Sensor networks for IoT are increasingly used in diverse areas, e.g., in situational and location awareness, leading to proliferation of sensors at the edge of physical world. There exist several variable step-size strategies in literature to improve the performance of diffusion-based Least Mean Square (LMS) algorithm for estimation in wireless sensor networks. However, a major drawback is the complexity in the theoretical analysis of the resultant algorithms. Researchers use several assumptions to find closed-form analytical solutions. This work presents a unified analytical framework for distributed variable step-size LMS algorithms. This analysis is then extended to the case of diffusion based wireless sensor networks for estimating a compressible system and steady state analysis is carried out. The approach is applied to several variable step-size strategies for compressible systems. Theoretical and simulation results are presented and compared with the existing algorithms to show the superiority of proposed work.     

A Survey of Distributed Relay Selection Schemes in Cooperative Wireless Ad hoc Networks

Cooperative communication aims to achieve spatial diversity gain via the cooperation of user terminals in transmission without requiring multiple transceiver antennas on the same node. It employs one or more terminals as relays in the neighbourhood of the transmitter and the receiver, which collaborate in the transmission and serve as a virtual MIMO antenna array. Allowing cooperation in wireless communication engenders new problems related to resource allocation and relay selection. Optimal relay selection is vital for reaping the performance benefit of cooperative communication. It is a challenging task to share channel information in timely and distributed manner and at the same time make optimal selection of relay in a time varying radio environment. This paper presents a comprehensive survey of distributed relay selection schemes for cooperative communication that have been proposed in the literature. We discuss various classifications of relay selection schemes and describe their characteristics and functionality. We then present a qualitative comparison of their performance against a set of representative metrics. Finally, we discuss some of their shortcomings and suggest some research directions.     

Utility‐driven construction of balanced data routing trees in wireless sensor networks

In wireless sensor networks, achieving load balancing in an energy‐efficient manner to improve the network lifetime as much as possible is still a challenging problem because in such networks, the only energy resource for sensor nodes is their battery supplies. This paper proposes a game theoretical‐based solution in the form of a distributed algorithm for constructing load‐balanced routing trees in wireless sensor networks. In our algorithm, load balancing is realized by adjusting the number of children among parents as much as possible, where child adjustment is considered as a game between the parents and child nodes; parents are considered as cooperative players, and children are considered as selfish players. The gained utility by each node is determined by means of some utility functions defined per role, which themselves determine the behavior of nodes in each role. When the game is over, each node gains the maximum benefit on the basis of its utility function, and the balanced tree is constructed. The proposed method provides additional benefits when in‐network aggregation is applied. Analytical and simulation results are provided, demonstrating that our proposed algorithm outperform two recently proposed benchmarking algorithms [1, 2], in terms of time complexity and communication overhead required for constructing the load‐balanced routing trees. Copyright © 2012 John Wiley & Sons, Ltd.     

An analytical study of resource division and its impact on power and performance of multi-core processors

The study and development of chip multi-processors (CMPs) are of utmost importance for the creation of future technologies. Devising a theoretical analysis of the micro-architecture model for the power/performance on CMPs is still a challenge. This paper addresses this problem by (1) introducing an analytical model for measuring the power and performance of a processor quantitatively, (2) analyzing the effects of resource division on power consumption and performance when executing a given benchmark, and (3) predicting the optimum number of cores to run the benchmark on. Our proposed analytically derived results show that in order to achieve power/performance gains, the optimum number of cores must be between 8 and 16.     

Sensitivity of SWAN QoS model in MANETs with proactive and reactive routing: a simulation study

In this article, one of the QoS models for MANETs—SWAN is studied under varying conditions to provide both quantitative and qualitative assessments of the applicability of the model in different scenarios. Results and analysis from NS-2 based simulation indicate that (i) real-time (RT) applications in SWAN-enabled mobile ad hoc networks experience low and stable delays under various traffic and mobility environment at the expense of best-effort (BE) traffic, (ii) SWAN model works compatibly with proactive as well as reactive routing protocols, and (iii) a careful choice of SWAN AIMD parameters is important to balance the throughput of the BE traffic and RT traffic and QoS provisions in MANETs.     

An ant-swarm inspired dynamic multiresolution data dissemination protocol for wireless sensor networks

One of the main concerns of wireless sensor networks (WSNs) is to deliver useful information from data sources to users at a minimum power consumption due to constraints that sensor nodes must operate on limited power sources for extended time. In particular, achieving power-efficiency and multihop communication in WSN applications is a major issue. This paper continues on the investigation of a recently proposed Minimum-power Multiresolution Data Dissemination (MMDD) problem for WSNs (whose solution is considered here as a benchmark). We propose an ant-inspired solution to this problem. To the best of our knowledge, no attempts have been made so far in this direction. We have evaluated the performance of our proposed solution by conducting a variety of experiments and have found our solution to be promising in terms of total energy consumption in data dissemination.     

A schedule‐based medium access control protocol for mobile wireless sensor networks

Recent advances in body area network technologies such as radio frequency identification and ham radio, to name a few, have introduced a huge gap between the use of current wireless sensor network technologies and specific needs of some important wireless sensor network applications such as medical care, disaster relief, or emergency preparedness and response. In these types of applications, the mobility of nodes can occur, leading to the challenge of mobility handling. In this paper, we address this challenge by prioritizing transmissions of mobile nodes over static nodes. This is achieved by using shorter contention windows in reservation slots for mobile nodes (the so‐called backoff technique) combined with a novel hybrid medium access control (MAC) protocol (the so‐called versatile MAC). The proposed protocol advocates channel reuse for bandwidth efficiency and management purpose. Through extensive simulations, our protocol is compared with other MAC alternatives such as time division multiple access and IEEE 802.11 with request to send/clear to send exchange, chosen as benchmarks. The performance metrics used are bandwidth utilization, fairness of medium access, and energy consumption. The superiority of versatile MAC against the studied benchmark protocols is established with respect to these metrics. Copyright © 2012 John Wiley & Sons, Ltd.