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We consider distributed uplink open-loop power control for orthogonal frequency division multiple access (OFDMA) cellular systems. To touch simultaneously on two main performance metrics in cellular systems, average throughput and cell-edge throughput, we focus on a metric of tradeoff performance. First we investigate two extreme cases to show that the wellknown SNR-based scheme and the INR-based...
A multi-user MIMO/OFDMA system for the next generation broadband wireless access (BWA) networks is studied, in which the base station (BS) has only knowledge of the statistics of the channel. A combination of MIMO, OFDMA and FDD could be suitable to increase spectral efficiency in a high speed network. We investigate methods with scalable channel feedback and we analyze the trade off between the amount...
In the heterogeneous networks, radio resource management (RRM) plays an important role to utilize the potential network diversity. In this paper, we study the RRM strategy in the heterogeneous networks involved with an orthogonal frequency division multiple access (OFDMA) network, with the aim of maximizing the minimum user throughput. An analytical model which reflects the feature of heterogeneous...
In multi-cell OFDMA systems, inter-cell interference can severely degrade the system throughput, particularly for cell-edge users. To mitigate the inter-cell interference problem, interference coordination is a promising approach that effectively restricts and allocates certain resources among users in different cells to minimize the effect of inter-cell interference. However, most approaches are...
Soft frequency reuse (SFR) has been proposed for enhancing cell-edge performance in OFDMA networks. Previous studies of SFR have used simulations over rather small networks having hexagon-shaped cells. In this paper, we examine the expected performance gain of SFR for networks in realistic radio environments and with irregular cell patterns. We define a performance metric that allows for fast assessment...
We propose a penalized iterative waterfilling to improve the performance of a distributed resource allocation method in terms of quality of service (QoS) requirements in multi-cell and multi-user OFDMA systems. In the distributed resource allocation method, since each selfish user tries to maximize its own throughput (i.e., sum rate) without any information on other users, it is less likely to satisfy...
In this paper, we consider cross-layer scheduling for the downlink of amplify-and-forward (AF) relay assisted orthogonal frequency division multiple access (OFDMA) networks. The proposed cross-layer design takes into account the effects of imperfect channel state information at transmitter (CSIT) in slow fading. The rate adaptation, power adaptation, and subcarrier allocation policies are optimized...
We consider the multi-user discrete bit loading problem in OFDMA systems with objective and constraints in terms of ergodic rates and powers. This differs from most existing techniques, which allocate rate and power according to instantaneous constraints and channel conditions. The maximum weighted ergodic sum-rate optimization problem is non-convex in general, but a dual decomposition results in...
In this paper, we investigate efficient scheduling algorithms in OFDMA multihop relaying networks. The scheduling scheme is modeled as a multiple objective programming problem to maximize the overall capacity and the number of satisfied users under the minimum rate constraint per user. An improved priority (IPRI) algorithm is exploited with novel opportunistic function, which relies on capacity gain,...
This paper investigates the allocation of subcarriers and power in the downlink channels of multiuser OFDM systems. The goal is to minimize the total transmit power under the constraints of user data rates and bit error rate (BER). We propose a sub-optimal algorithm to achieve the goal in this paper. We introduce a new factor which is the gain difference between the maximum and the next maximum userspsila...
Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMA/LTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally...
Orthogonal frequency division multiple access (OFDMA) systems have recently drawn considerable attention as potential candidates for future generation cellular systems. To achieve proportional fairness among users while improving user's satisfaction in the upper layer, e.g. application and transmission control protocol (TCP) layers, we propose a novel multi-layer optimization approach for packet scheduling...
It is well known that cross-layer scheduling can boost the spectral efficiency of multi-user OFDMA systems through multi-user selection diversity but existing designs usually have two important assumptions - users are delay-insensitive and channel state information at the transmitter (CSIT) is perfect. In practice, users have heterogeneous delay requirements and CSIT usually becomes outdated in time...
This paper investigates the effect of using different optimization criteria for dynamic subcarrier allocation in a single carrier - frequency division multiple access (SC-FDMA) system. Simulation results show that using the minimum bit error rate (BER) as the optimization criterion has the best BER performance and an almost optimal capacity performance. The other criteria referred to as maximum spectral...
In this paper, a novel resource allocation algorithm is proposed for multi-service OFDMA systems. The multi-objective optimization model is established for resource allocation, according to the different QoS requirements of different services. In order to achieve the suboptimal solution for the multi-objective optimization problem, this paper proposes a novel hierarchical algorithm, and adopting some...
This paper proposes a cooperative game theoretic resource allocation scheme for downlink OFDMA wireless networks. We define a user??s payoff as a function of his data throughput. Then the source allocation can be modeled as a cooperative game to maximize the aggregate payoff of the users. To achieve the Nash bargaining solution (NBS) of the game, a suboptimal subcarrier allocation is first performed...
This paper reformulates the multi-user OFDMA resource allocation problems in broadcast and multiple-access channels by defining an equivalent interference channel. The resulting problems are then solved by employing low-complexity algorithms for spectrum optimization in the interference channel. The re-formulation averts the high-complexity integer programming problem that otherwise results from an...
In this paper, we focus on resource allocation in OFDMA based cooperative cellular networks with multiple sources, multiple relays and a single destination. Four typical relay schemes are discussed, namely, Amplify-and-Forward (AF) and Decode-and-Forward (DF) both with or without diversity. We formulate two general optimization problems incorporating single-carrier allocation and multi-carrier allocation...
This paper considers the subchannel-allocation problem to maximize the sum-rate in orthogonal frequency- division multiple-access (OFDMA) regenerative relaying downlink systems with a total power constraint. Based on the Lagrange dual decomposition and the optimal condition of the problem, this paper proposes three heuristic algorithms: an extended modified inverse subchannel signal-to-noise ratio...
This paper targets the problem of optimum power allocation and link scheduling in cellular systems. In particular, the uplink performance of OFDMA (orthogonal frequency division multiple access) is investigated. By means of heuristic relaxation, the NP-hard problem of joint power control and scheduling is transformed into one of power controlled random access (PCRA), which is formulated as a convex...
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