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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....
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...
In this paper, resource allocation and scheduling in an orthogonal frequency division multiple access (OFDMA) downlink network is studied. The considered problem is modeled as an optimization problem which takes into account a multiple antenna eavesdropper and artificial noise generation for secure communications. Power, secrecy data rate, and subcarrier allocation are optimized for maximization of...
In cognitive radio settings with highly dynamic primary activities and with small opportunities for secondary access, the requirement to fairly distribute the temporarily available spectral ranges among the unlicensed users turns out to be of particular relevance. The current paper addresses this issue by presenting a new design formulation that aims to optimize the performance of an orthogonal-frequency-division-multiple-access...
We consider subcarrier assignment and power allocation in OFDMA wireless mesh networks. Traditional full spatial reuse increases bandwidth efficiency but ignores multiuser diversity in the multi-hop network. Our method enables fractional spatial reuse with which multiuser diversity can also be exploited. The original optimization problem is decomposed into three tractable subproblems. First, subcarrier...
In this paper, we proposed a heuristic algorithm to investigate the performance of resource allocation combined with coordinated multipoint(CoMP) in multi-cell OFDMA systems. We first develop an analytical model of resource allocation for an arbitrary number of users in the different cells, and formulate it into an optimization problem that is proved to be NP-complete. To reduce the computational...
In this paper, the downlink of a cell is considered in an OFDMA-based relay network. In the cell, a base station (BS) and fixed relay stations (RSs) are deployed. Multiple subscriber stations (SS) are located in the cell. A SS is served either by a direct or a two hop connection. In a direct connection, a link between BS and SS exists. In a two hop connection, a link exists between BS and RS and between...
Consider the problem of base-station and sub-carrier assignment on the downlink of a two-cell OFDMA system with adaptive modulation. The aim is to maximize a common data rate that can be offered to each user with a guaranteed maximum rate-outage probability. A target bit-error rate is also guaranteed with a maximum outage probability. The channel model takes into account the propagation path-loss...
This paper provides analysis of the inter cell interference coordination problem in multicell OFDMA systems. In order to reduce the interference without losing much frequency resources in each cell, cell users are partitioned into two classes, namely interior and exterior users. Frequency resources are universally used in all interior cells' areas whereas users of exterior zones have a frequency reuse...
The paper presents a new approach of optimal spectrum and power allocation for orthogonal frequency-division multiplexing (OFDM) modulation schemes. The algorithm is implemented using a parallel processing method, where each transmitted bit will minimize its cost functions, by choosing the spectrum and powers that suit better the interference pattern. The optimization problem is treated as a constrained...
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