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In Wi-Fi networks, Device-to-Device (D2D) communications aim to improve the efficiency of the network by supporting direct communication between users in close proximity. However, in a congested Wi-Fi network, establishing D2D connections through a locally managed self-organising approach will intensify the congestion and reduce the scalability of the solution. Therefore, a centralised management...
In recent decades, due to limitation of radio spectrum and increasing users in wireless networks, spectral efficiency has been a considerable issue in literatures. In addition, energy consumption is rapidly increasing in wireless communications due to growing demand for wireless technologies especially cellular networks. Therefore, energy efficiency has become an important issue in such networks....
The knowledge of the propagation behavior of radio waves is a fundamental prerequisite for planning and optimizing mobile radio networks. Propagation effects are usually simulated numerically, since real-world measurement campaigns are time-consuming and expensive. Automatic planning algorithms can explore a vast amount of network configurations to find good deployment schemes. However, complex urban...
We present our initial work on the design and implementation of an efficient channel assignment and routing architecture for multi-radio and multichannel wireless mesh networks (WMNs). Our proposed scheme is derived from the principle of Ant Colony Optimization (ACO) in which smart ants (agents) perform the routing and channel assignment to stochastically solve a dynamic network optimization problem...
Current communication schemes rely on instantaneous adaptation, which increases the system complexity and is memoryless. We propose a scheme for adapting system parameters based on a priori knowledge of the channel statistics to reduce feedback requirements. As a vital parameter in OFDM system, cyclic prefix (CP) length depends mainly on two channel characteristics: the channel gains and the root...
Cognitive Radio (CR) improves spectral efficiency by allowing unlicensed (secondary) users to concurrently operate with licensed (primary) users. The side-lobe interference from an OFDM-based secondary user (SU) causes unwanted interference to the primary user (PU) of the spectrum. While interference mitigation to the PU spectral band has received a lot of attention in recent literature, the novelty...
Optimization of hard fusion spectrum sensing using the k-out-of-N rule is considered. Two different setups are used to derive the optimal k. A throughput optimization setup is defined by minimizing the probability of false alarm subject to a probability of detection constraint representing the interference of a cognitive radio with the primary user, and an interference management setup is considered...
In Cognitive Radio Networks (CRNs), when the Primary Users (PUs) appear, the SUs have to evacuate the licensed spectrum in use or reduce the transmit power so that no harmful interference is introduced to the PUs. In this paper, we explore the multiple Secondary Users (SUs) coexistence system in CRNs based on power control mechanism and interference temperature model. We propose an optimal solution...
In practice, the imperfect channel state information can degrade the optimization performance of a cognitive system, especially yielding the detrimental violation of the interference constraint perceived by the primary users. This paper investigates the linear transceiver design in cognitive downlink systems with the imperfect channel knowledge, aiming at minimizing the mean square error of the secondary...
We consider a cognitive relay network (CRN) where the secondary users (SUs) are involved as cooperative relays in a primary user's (PU) communication. To avoid generating interference to PU transmissions, it is assumed that SUs can transmit only when the PU's channel is idle. On one hand, SUs use some relay powers to speed up the PU's transmissions. Consequently, PU's buffer will be depleted faster,...
We consider the Noisy MIMO Interference Channel (IFC) with linear transmitters and receivers and full CSI. The maximization of the Weighted Sum Rate (WSR) or transceiver design for Interference Alignment (IA) lead to cost functions with many local optima. Deterministic annealing is an approach that allows to track the variation of the known solution of one version of the problem into the unknown solution...
The minimization of the overall power consumption of wireless networks while satisfying a certain throughput and error rate constraint is investigated. The total power dissipation includes the radiated power as well as the circuit power consumption. In the context of battery operated short range communication, where low power, low cost and small size are key requirements (e.g. standard IEEE 802.15...
In future B3G/4G communication systems, the special application of femtocell in the enterprise offices and public places has broad prospect. However, as the femtocell operation under such multi-femtocell environment is significantly different from that of usual residential femtocells, the femtocell configuration and optimization might be much more complex. One key issue is to find how will the femtocell...
White space means spatially (or temporally) unused spectrum and this can be used on a unlicense basis. Since protecting primary users from harmful interference is the most important issue in unlicensed spectrum access on a secondary basis, regulatory authorities mandate the use of geolocation and DB (database) access capability as interference avoid scheme. The main role of this white space DB is...
Motivated by the need for fast computations demanded by wireless sensor networks, the new F-Lipschitz optimization theory is introduced for a novel class of optimization problems. These problems are defined by simple qualifying properties specified in terms of increasing objective function and contractive constraints. It is shown that feasible F-Lipschitz problems have always a unique optimal solution...
Wireless spectrum is a regulated resource, whose control and usage is regulated by government agencies. The allocation of spectrum to interested parties is usually conducted through auctions, and are an important source of income for these regulatory agencies. However, previous spectrum auction design fail to take into consideration the effect of interference, which can adversely affect the truthfulness...
Inter-cell interference (ICI) is responsible for user throughput degradation and especially for users found near cell border which additionally experience serious path-losses. Efficient methods for ICI mitigation are ICI coordination (ICIC) schemes which allocate certain resources among users in different cells. In this paper we propose a decentralized ICIC scheme in order to mitigate the ICI and...
In this paper, we deal with a cross-layer optimization problem in Ad Hoc networks. Based on network utility maximization framework, we formulate the joint congestion and power control problem providing SINR guarantee and energy saving. We adopt dual decomposition technique to deduce two maximization sub problem, and then design the optimal distributed congestion control algorithm at the transport...
We study in this paper the resource allocation matter for unlicensed multiband ultra-wideband (UWB) users in the context of high-rate wireless personal area network (WPAN). The problem is viewed as a coexistence problem with existing licensed systems. The QoS support and the interference mitigation are jointly considered in this study to derive a novel interference power control mechanism that differentiates...
This paper investigates the performance effects of packet depletion on multihop wireless networks. The resulting capacity usage inefficiencies of link assigned schedules are shown even at the maximum supportable uniform network load. Hybrid node-link assignment is employed to extend transmission rights, allowing nodes to transmit on sets of reserve links when the primary scheduled link experiences...
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