Current Issue : January - March Volume : 2016 Issue Number : 1 Articles : 4 Articles
Most of the existed works on the radio resource allocation (RRA) problem commonly assume the channel-state\ninformation (CSI) can be perfectly obtained by the transmission source. However, such assumption is not practical in\nthe realistic wireless systems. In this work, we consider the practical implementation issues of resource allocation in\northogonal frequency division multiple access (OFDMA) two-way relay networks: the inaccuracy of channel-state\ninformation (CSI) available to the source. Instead, only the estimated channel status is known by the source. In this\ncontext, a joint optimization of subcarrier pairing and allocation, relay selection, and transmit power allocation is\nformulated in OFDMA two-way amplify-and-forward relay networks. Moreover, the objective of this work is to\nminimize the energy consumption of the overall system. Further, to ensure the quality of service (QoS) or data rate\nrequirement, the energy consumption must be minimized without compromising the QoS. Therefore, by applying\nconvex optimization techniques, energy-efficient algorithms are developed with the objective to minimize the total\ntransmit power with guaranteeing the required data rates. Through simulation studies, energy consumption\nperformance of the systems under the proposed schemes is investigated. It can be observed that our proposed\nscheme can improve the energy consumption performance of the considered system....
As the wireless sensor networks (WSNs) continue to evolve, it becomes more and more important. Furthermore, no one\ncan deny that quality of services (QoS) is still one of the most important areas in this domain. In this paper, a system for\nguaranteeing WSN QoS is proposed. The idea of this system is to use the previous individual solutions such as clustering,\ndata prioritization, and data classification in addition to efficient techniques for network management. Simulation of this\nsystem is achieved using the network simulation package (NS2). Simulation results are given to demonstrate the\neffectiveness of the proposed system in terms of throughput, latency, lost packets, and sensor power consumption....
Nowadays, cognitive radio (CR) is considered the key technology to deploy wireless nodes that are able to adapt their\ntransmission parameters based on the characteristics of the environment. In our previous works, we leveraged the\nreconfigurability properties offered by the CR technology to implement Cognitive Wireless Mesh Networks (CMNs)\noperating on the 2.4-GHz industrial, scientific, and medical (ISM) band. Urban-X, a new architecture for Multi-radio\nCognitive Mesh Networks, self-configures and self-adapts to the dynamic interference conditions experienced on the\nWi-Fi channels in dense urban environments. Urban-X estimates traffic load of existing users outside the mesh in each\nchannel and utilizes less occupied channels opportunistically. In such dynamic environment, a transport layer protocol\ncan suffer from variation in delay and available bandwidth due to spectrum sensing and mobility. Several TCP solutions\nfor the CWMNs have been proposed but they could not be employed for implementation due to complexity and\ninefficiency. Instead, we adopt network function virtualization (NFV) technique which allows to instantiate virtualized\nnetwork functions (VNFs) dynamically on demands. For this, we propose overall architecture of NFV framework for the\nCMNs and apply TCP accelerators (ACC) VNFs to improve TCP throughput as a case study. Simulation results show\nTCP-ACC VNF can achieve a notable performance enhancement compared to previous TCPs for the CMNs....
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