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Suboptimal Rate Adaptive Resource Allocation for Downlink OFDMA Systems  [PDF]
Sanam Sadr,Alagan Anpalagan,Kaamran Raahemifar
International Journal of Vehicular Technology , 2009, DOI: 10.1155/2009/891367
Abstract: This paper aims to study the performance of low complexity adaptive resource allocation in the downlink of OFDMA systems with fixed or variable rate requirements (with fairness consideration). Two suboptimal resource allocation algorithms are proposed using the simplifying assumption of transmit power over the entire bandwidth. The objective of the first algorithm is to maximize the total throughput while maintaining rate proportionality among the users. The proposed suboptimal algorithm prioritizes the user with the highest sensitivity to the subcarrier allocation, and the variance over the subchannel gains is used to define the sensitivity of each user. The second algorithm concerns rate adaptive resource allocation in multiuser systems with fixed rate constraints. We propose a suboptimal joint subchannel and power allocation algorithm which prioritizes the users with the highest required data rates. The main feature of this algorithm is its low complexity while achieving the rate requirements.
Variance Based Algorithm for Grouped-Subcarrier Allocation in OFDMA Wireless Systems  [PDF]
Noureddine Hamdi
Mathematics , 2012,
Abstract: In this paper, a reduced complexity algorithm is proposed for grouped-subcarriers and power allocation in the downlink of OFDMA packet access wireless systems. The available subcarriers for data communication are grouped into partitions (groups) where each group is defined as a subchannel. The scheduler located at the base station allocates subchannels to users based on the variance of subchannel gains. The proposed algorithm for group allocation is a two-step algorithm that allocates groups to users based on the descending order of their variances to resolve the conflicting selection problem, followed by a step of fairness proportionality enhancement. To reduce the feedback burden and the complexity of the power allocation algorithm, each user feeds back the CSI on each group if the variance of gains of subcarriers inside it is less than a predefined threshold. To Show the performance of the proposed scheme, a selection of simulation results is presented.
Resource Allocation Algorithm for OFDMA-based Cooperative Communication Systems
OFDMA协同通信系统资源分配算法

WANG Dong,FENG Wen-jiang,HENG Yu-long,
王东
,冯文江,衡玉龙

计算机科学 , 2012,
Abstract: Taking users' demand for both QoS and fairness into account,a joint sub-carrier and power allocation algorithm was proposed for OFDMA-based cooperative cellular networks. Existing sub-carrier allocation algorithm considers only average power allocation, in which incomplete application of power in relaying nodes exists. As a versus, we studied the optimal residual power allocation on the completion of sub-carrier allocation. Consequently, a water-filling power allocation scheme ground on dichotomy was given. Simulation shows that our proposed joint allocation algorithm can satisfy users' need for QoS and fairness,while it boosts the networking throughput dramatically.
Joint Scheduling and Resource Allocation in the OFDMA Downlink: Utility Maximization under Imperfect Channel-State Information  [PDF]
Rohit Aggarwal,Mohamad Assaad,C. Emre Koksal,Philip Schniter
Mathematics , 2010, DOI: 10.1109/TSP.2011.2162953
Abstract: We consider the problem of simultaneous user-scheduling, power-allocation, and rate-selection in an OFDMA downlink, with the goal of maximizing expected sum-utility under a sum-power constraint. In doing so, we consider a family of generic goodput-based utilities that facilitate, e.g., throughput-based pricing, quality-of-service enforcement, and/or the treatment of practical modulation-and-coding schemes (MCS). Since perfect knowledge of channel state information (CSI) may be difficult to maintain at the base-station, especially when the number of users and/or subchannels is large, we consider scheduling and resource allocation under imperfect CSI, where the channel state is described by a generic probability distribution. First, we consider the "continuous" case where multiple users and/or code rates can time-share a single OFDMA subchannel and time slot. This yields a non-convex optimization problem that we convert into a convex optimization problem and solve exactly using a dual optimization approach. Second, we consider the "discrete" case where only a single user and code rate is allowed per OFDMA subchannel per time slot. For the mixed-integer optimization problem that arises, we discuss the connections it has with the continuous case and show that it can solved exactly in some situations. For the other situations, we present a bound on the optimality gap. For both cases, we provide algorithmic implementations of the obtained solution. Finally, we study, numerically, the performance of the proposed algorithms under various degrees of CSI uncertainty, utilities, and OFDMA system configurations. In addition, we demonstrate advantages relative to existing state-of-the-art algorithms.
Fair Adaptive Bandwidth and Subchannel Allocation in the WiMAX Uplink  [cached]
Morell Antoni,Seco-Granados Gonzalo,Vicario JoséLópez
EURASIP Journal on Wireless Communications and Networking , 2009,
Abstract: In some modern communication systems, as it is the case of WiMAX, it has been decided to implement Demand Assignment Multiple Access (DAMA) solutions. End-users request transmission opportunities before accessing the system, which provides an efficient way to share system resources. In this paper, we briefly review the PHY and MAC layers of an OFDMA-based WiMAX system, and we propose to use a Network Utility Maximization (NUM) framework to formulate the DAMA strategy foreseen in the uplink of IEEE 802.16. Utility functions are chosen to achieve fair solutions attaining different degrees of fairness and to further support the QoS requirements of the services in the system. Moreover, since the standard allocates resources in a terminal basis but each terminal may support several services, we develop a new decomposition technique, the coupled-decompositions method, that obtains the optimal service flow allocation with a small number of iterations (the improvement is significant when compared to other known solutions). Furthermore, since the PHY layer in mobile WiMAX has the means to adapt the transport capacities of the links between the Base Station (BS) and the Subscriber Stations (SSs), the proposed PHY-MAC cross-layer design uses this extra degree of freedom in order to enhance the network utility.
Fair Adaptive Bandwidth and Subchannel Allocation in the WiMAX Uplink  [cached]
Antoni Morell,Gonzalo Seco-Granados,José López Vicario
EURASIP Journal on Wireless Communications and Networking , 2009, DOI: 10.1155/2009/918261
Abstract: In some modern communication systems, as it is the case of WiMAX, it has been decided to implement Demand Assignment Multiple Access (DAMA) solutions. End-users request transmission opportunities before accessing the system, which provides an efficient way to share system resources. In this paper, we briefly review the PHY and MAC layers of an OFDMA-based WiMAX system, and we propose to use a Network Utility Maximization (NUM) framework to formulate the DAMA strategy foreseen in the uplink of IEEE 802.16. Utility functions are chosen to achieve fair solutions attaining different degrees of fairness and to further support the QoS requirements of the services in the system. Moreover, since the standard allocates resources in a terminal basis but each terminal may support several services, we develop a new decomposition technique, the coupled-decompositions method, that obtains the optimal service flow allocation with a small number of iterations (the improvement is significant when compared to other known solutions). Furthermore, since the PHY layer in mobile WiMAX has the means to adapt the transport capacities of the links between the Base Station (BS) and the Subscriber Stations (SSs), the proposed PHY-MAC cross-layer design uses this extra degree of freedom in order to enhance the network utility.
A cross-layer resource allocation scheme for spatial multiplexing-based MIMO-OFDMA systems  [cached]
Akbudak Tarik,Al-Shatri Hussein,Czylwik Andreas
EURASIP Journal on Wireless Communications and Networking , 2011,
Abstract: We investigate the resource allocation problem for the downlink of a multiple-input multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) system. The sum rate maximization itself cannot cope with fairness among users. Hence, we address this problem in the context of the utility-based resource allocation presented in earlier papers. This resource allocation method allows to enhance the efficiency and guarantee fairness among users by exploiting multiuser diversity, frequency diversity, as well as time diversity. In this paper, we treat the overall utility as the quality of service indicator and design utility functions with respect to the average transmission rate in order to simultaneously provide two services, real-time and best-effort. Since the optimal solutions are extremely computationally complex to obtain, we propose a suboptimal joint subchannel and power control algorithm that converges very fast and simplifies the MIMO resource allocation problem into a single-input single-output resource allocation problem. Simulation results indicate that using the proposed method achieves near-optimum solutions, and the available resources are distributed more fairly among users.
Optimization of Subcarrier and Power Allocation in Uplink OFDMA Systems
M.Vadivel,H.Ranganathan
Indian Journal of Computer Science and Engineering , 2012,
Abstract: The allocation of subcarriers and power to users is an important issue for exploiting the advantages of OFDMA systems. The main objective of the traditional OFDMA uplink resource allocation focuses on two aspects: one is to maximize the transmission rate of each user, the other is to minimize power. In this paper, we proposed the joint subcarrier and power allocation in the uplink of an OFDMA system thereby increasing the rate sum capacity of the system with low computational burden. The simulation results shows that the powerefficiency of the proposed algorithm increases greatly over that of the Maximum marginal Rate subcarrier and WaterFilling power allocation, which is the optimal algorithm to derive the maximum transmission rate and the power utilization can be minimized.
Priority-Based Resource Allocation for Downlink OFDMA Systems Supporting RT and NRT Traffics  [PDF]
Hua WANG, Lars DITTMANN
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2008, DOI: 10.4236/ijcns.2008.13034
Abstract: Efficient radio resource management is essential in Quality-of-Service (QoS) provisioning for wireless communication networks. In this paper, we propose a novel priority-based packet scheduling algorithm for downlink OFDMA systems. The proposed algorithm is designed to support heterogeneous applications consisting of both real-time (RT) and non-real-time (NRT) traffics with the objective to increase the spectrum efficiency while satisfying diverse QoS requirements. It tightly couples the subchannel allocation and packet scheduling together through an integrated cross-layer approach in which each packet is assigned a priority value based on both the instantaneous channel conditions as well as the QoS constraints. An efficient suboptimal heuristic algorithm is proposed to reduce the computational complexity with marginal performance degradation compared to the optimal solution. Simulation results show that the proposed algorithm can significantly improve the system performance in terms of high spectral efficiency and low outage probability compared to conventional packet scheduling algorithms, thus is very suitable for the downlink of current OFDMA systems.
Efficient and fair resource allocation in downlink OFDMA systems
Efficient and fair resource allocation in downlink OFDMA systems
 [PDF]

宋政育,侯舒娟,吴嗣亮
- , 2015, DOI: 10.15918/j.jbit1004-0579.201524.0213
Abstract: A resource allocation problem considering both efficiency and fairness in orthogonal frequency division multiple access (OFDMA) systems is studied. According to the optimality conditions, a downlink resource allocation algorithm consisting of subcarrier assignment and power allocation is proposed. By adjusting the tradeoff coefficient, the proposed algorithm can achieve different levels of compromise between efficiency and fairness. The well-known classic resource allocation policies such as sum-rate maximization algorithm, proportional fairness algorithm and max-min algorithm are all special cases of the proposed algorithm. Simulation results show that the compromise between efficiency and fairness can be continuously adjusted according to system requirements.
A resource allocation problem considering both efficiency and fairness in orthogonal frequency division multiple access (OFDMA) systems is studied. According to the optimality conditions, a downlink resource allocation algorithm consisting of subcarrier assignment and power allocation is proposed. By adjusting the tradeoff coefficient, the proposed algorithm can achieve different levels of compromise between efficiency and fairness. The well-known classic resource allocation policies such as sum-rate maximization algorithm, proportional fairness algorithm and max-min algorithm are all special cases of the proposed algorithm. Simulation results show that the compromise between efficiency and fairness can be continuously adjusted according to system requirements.
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