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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....
A distributed optimization algorithm is presented for resource allocation in wireless relay networks. This algorithm is particularly useful in multiple-source, multiple-relay wireless networks employing fractional cooperation, in which each relay contributes only a fraction of its resources to each source; in this case, the algorithm is used to find the optimal fractions. The advantage of this distributed...
Energy consumption in wireless communication system is rapidly increasing due to the growth in wireless multimedia access. Combating the adverse effects of excessive energy consumption demands for energy-aware system design called green communication, which has become the major focus of many researchers recently. In this paper, we propose user selection and power allocation schemes for a multi-user...
In this paper, we formulate an optimization problem for resource allocation and scheduling in orthogonal frequency division multiple access (OFDMA) half-duplex decode-and-forward (DF) relay assisted networks. Our problem formulation takes into account artificial noise generation to combat a multiple antenna eavesdropper. The secrecy data rate, power, and sub-carrier allocation policies are optimized...
We address the optimal sink scheduling problem in wireless sensor networks (WSNs). The problem is inherently difficult since sink scheduling and data routing are tightly coupled. Previous approaches either have questionable performance due to no joint considerations, or are based on relaxed constraints. Our aim is to fill in this blank in the research. First, by discretizing continuous time, we develop...
MIMO, OFDMA and cooperative relaying are the key technologies in future wireless communication systems. However, under the usage of these technologies, resource allocation becomes a more crucial and challenging task. In multi-user MIMO-OFDMA relay-enhanced cellular networks, we formulate the optimal instantaneous resource allocation problem including user group selection, path selection, power allocation,...
In this work, the combination of one-way and two-way relaying is examined in a scenario where two multi-antenna nodes exchange information under an asymmetric rate constraint via a half-duplex non-regenerative multi-antenna relay. Two-way relaying overcomes the multiplexing loss of one-way relaying, but additional optimizations are required to fulfill the asymmetric rate constraint. To enable the...
In this paper, we deal with a scheduling algorithm to fulfil a qualified end-to-end video service in terms of fairness and energy efficiency over multi-hop wireless sensor networks. For this goal, we explore to optimize the routing and power allocation via cross-layer optimization by utilizing a game-theoretic approach. In order to reduce computational complexity, we also propose a distributed optimization...
In DTNs, due to the unique characteristic of frequent partitioning, multicasting is a considerably different and challenging problem. Moreover, the single data multicast is different from multiple data multicast. In this paper, The mathematics model of multiple data multicast for DTNs is established, and the ant colony optimization algorithm introduce to solve the multiple data multicast problem....
In this paper, the total transmission power of a multi-source multi-destination relay network is minimized under the constraint that the signal to interference plus noise ratio (SINR) requirement of each source-destination pair is satisfied. The optimization problem involves K power variables, where K is the number of source-destination pairs in the network, and an exhaustive search is prohibitive...
In this work, we study the MIMO Gaussian bidirectional broadcast channel (BBC) with common message and characterize the capacity region. Moreover, we show that the transmit covariance matrix optimization problem has the same structure as the corresponding optimization problem of the BBC without common message which leads to the comfortable position to transfer results from one scenario to the other...
Dynamic spectrum access (DSA) is proposed to deal with the growing shortage of available leased spectrum for wireless communication. We investigate a subset of DSA referred to as Dynamic Spectrum Leasing (DSL). At its core, DSL allows spectrum lease holders and cognitive radios to cooperate in an effort to leverage spatial diversity to improve channel utilization for both parties. In this research,...
We devise an optimization framework for generalized proportional fairness (GPF) under different time scales for amplify-and-forward (AF) relay networks. In GPF scheduling, a single input parameter is used to change the fairness from throughput optimal, to proportionally fair and asymptotically to max-min fair. We extend the GPF scheduling to include a new input parameter, which determines the time-scale...
The penetration of distributed generations (DGs) would drastically affect traditional power system fault current level and the characteristic of fault current, consequently affect on coordination of over current relays. Implementation of fault current limiters (FCLs) to locally limit the DG fault current, could somewhat overcome with this problem. Kind and value of FCLs must be chosen by considering...
This paper studies the joint design of transmit beamformers, receive combiners, and linear relaying matrix for a two-way amplify-and-forward (AF) relay system equipped with multiple-antennas at sources and relay. A single data stream is transmitted by each source. Due to the non-convexity of the optimization problem, finding a solution that maximizes the sum-rate appears to be intractable. Hence,...
In this work, we study distributed gain allocation to maximize the achievable sum-rate in non-regenerative multihop networks with multiple users and multi-antenna nodes. The source and relay nodes are constrained to forward linear transformations of their input and calculate their transformation matrices based on locally available channel state information and limited feedback from the destination...
Relaying is one of the key techniques considered by the 3GPP LTE-Advanced as part of 4G cellular technologies, aiming to increase the coverage and capacity of the network especially for the edge nodes. In this work, we have considered the uplink scheduling of an LTE network with the help of positioned relay nodes. We have projected the entire problem as a constrained optimization problem. As a solution,...
Considering the quality-of-service (QoS), power allocation is a critical importance issue in realizing multi-hop relay systems. In this paper considering the QoS Constraints in term of BER or instantaneous SNR, an optimal power allocation scheme that minimized the total power consumption in an amplify-and-forward (AF) multi-hop multi-branch transmission system is proposed. Considering an asymptotic...
In this work, we find the optimal relay location for a secondary user in a cognitive radio network subject to outage constraints. With selection decode-and-forward relay protocol, we formulate this problem as a nonlinear optimization problem, and then derive an approximation formulation that gives a close-optimal relay location, which means that we can use the approximation instead to solve the relay...
The problem of the design of p-cycles in WDM mesh networks under single link failure scenario has been extensively investigated; however, there are very fewer studies upon the design of p-cycles for protecting against a single node failure. In this paper, we develop a new scalable design approach for calculating p-cycles with node protection capability. Conventional design methods formulate the problem...
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