Adaptive subcarrier allocation and bit loading for voice/data transmission in multiuser OFDM systems

A new algorithm of adaptive subcarrier allocation and bit loading (A‐SABL) is proposed for simultaneous voice and data transmission in multiuser OFDM systems. The algorithm takes advantage of the frequency diversity and the voice/data transmission requirements to dynamically assign the number of subcarriers and bits/per symbol on each subcarrier for each user in a single cell. Due to the strict delay requirement of voice service, the subcarriers with low channel gains are assigned for voice transmission with a small number of bits per symbol to guarantee its required bit‐error‐rate (BER) and transmission rate. Based on the remaining subcarriers with high channel gains and the transmission power, the throughput of data transmission is then maximized by loading as many bits as possible on each subcarrier to achieve the required transmission bit rate and BER. Theoretical analysis and simulation on the proposed algorithm show that a better performance is obtained than previously reported schemes. Copyright © 2008 John Wiley & Sons, Ltd.     

Joint subcarrier and power allocation with fairness in uplink OFDMA systems based on ant colony optimization

One of the key problems in uplink orthogonal frequency division multiple access systems is to efficiently and fairly allocate subcarriers and powers. However, most existing work has not sufficiently taken into account fairness when allocating these resources so that subcarriers cannot be fairly allocated among users with different channel conditions. To overcome this shortcoming, we first present an optimization framework with fairness, which aims to fairly allocate subcarriers among different users and to distribute the transmission power of each user over the assigned subcarriers. Here, the fairness is guaranteed by associating each user with a utility function and placing a lower limit on the number of subcarriers assigned. In particular, different from previous work, utility functions are allowed to be nonconcave and nondifferentiable so that our framework can be suitable for resource allocation for real‐time applications. Furthermore, an iterative algorithm based on the ant colony optimization is proposed, according to which subcarriers can be efficiently and fairly allocated among different users. Simulation results verify the convergence of our algorithm. In addition, our algorithm outperforms several other algorithms in terms of the fairness of resource allocation. Copyright © 2012 John Wiley & Sons, Ltd.     

Dynamic resource allocation in adaptive wireless OFDMA systems

Modern wireless orthogonal frequency division multiple access (OFDMA) systems incorporate dynamic resource allocation (DRA), adaptive modulation and coding (AMC), and power control (PC) to exploit multiuser diversity and achieve higher system throughput. In the literature, only a few proposed algorithms deal with the contiguous DRA problem according to which a contiguous collection of resources can be allocated to each user. This paper formulates this high complexity problem, provides a suitable decision metric and a simple yet efficient solution. The proposed algorithm allocates in each step a contiguous collection of resources to the pending user that leads to the highest estimated correctly received number of bits. Simulation results show that, in this way, considerably improved performance can be achieved in terms of overall system throughput, spectral efficiency, and served traffic. Copyright © 2010 John Wiley & Sons, Ltd.     

On the use of immune clonal optimization for joint subcarrier and power allocation in OFDMA with proportional fairness rate

Resource allocation in orthogonal frequency division multiple access is a constraint optimization problem. In this paper, we concentrate on maximizing both the sum capacity and proportional fairness rate among users. The optimization model of resource allocation is formulated and then an immune clonalbased algorithm is proposed for it. The resource allocation is solved by separating the subcarrier and power allocation in two steps. Suitable immune operators are designed, such as clonal, mutation, Baldwin learning, selection and so on. Experiments show that, compared with the previous methods, the proposed algorithm obtains higher sum capacity with comparable computational complexity, and keeps the proportional rate more fairly among users. Copyright © 2012 John Wiley & Sons, Ltd.     

Adaptive radio resource allocation for multiple traffic OFDMA broadband wireless access system

1 Introduction Next-generation wireless communication systems (systems beyond 3G) will be required to provide flexible and easy deployment solution to high-speed communications and to support a variety of services utilizing advanced multiple access techni…     

Adaptive resource allocation techniques in OFDMA using cross-layer architecture

This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access （OFDMA） based on the broadband wireless access system. According to the cross-layer architecture, the information in link layer is used for adaptive resource allocation in OFMDA. A new cross-layer adaptive resource allocation algorithm is developed which can guarantee the users to be in minimum average waiting time in link-layer and get the better spectrum utilization. Numerical results show that our scheme is appealing and can get about half of average waiting time less and 0.5 bps/Hz spectrum utilization more than the scheme in 1EEE802.16a.     

改进的多用户OFDM系统子载波和比特分配算法

针对多用户正交频分复用（OFDM）系统资源分配问题,提出了一种改进的基于边缘自适应（MA）准则的子载波和比特分配算法。在采用比例公平准则为每个用户分配子载波集合基础上,以用户速率最大者-最小者（Max-Min）子载波交换为原则进行子载波调整,使用户功率递减同时兼顾用户的公平性;通过对信道状态信息进行判断,利用贪婪算法将用户子载波分配的比特取整,以实现系统功率最小化。实验结果表明,本文提出的改进次优算法的计算复杂度较传统分步算法稍高,但仍远低于最优算法,其系统性能得以提升,且接近最优算法。     

Multiuser subcarriers and bit allocation combining adaptive mapping for SC-FDMA system

In this article, a multiuser single carrier frequency division multiple access （SC-FDMA） system is considered, based on which an adaptive subcarrier and bit allocation algorithm is investigated. The algorithm has been used to achieve a subcarrier mapping mode in this system, which combines the advantages of single- and multi-carrier transmissions, such as, low peak to average power ratio, orthogonality of signals of different users, and low complexity. Simulation results show that it has a similar performance as that of the adaptive allocation algorithm in the orthogonal frequency division multiple （OFDM） system and the proposed mapping mode has a performance gain over the two existing mapping modes at the link level.     

New adaptive bit allocation algorithms for multiuser OFDM/CDMA systems

An adaptive bit allocation algorithm is proposed for multiuser transmission in OFDM/CDMA systems. The proposed scheme takes advantage of frequency diversity to dynamically allocate a suitable number of bits/per symbol on subcarriers of each user based on the transmitting objectives such as the required transmission rate and BER. A suboptimal solution to the problem of the bit allocation on subcarriers for each user is derived by minimizing the interference power from each user. Then an algorithm for adjusting the number of allocated bits is used to further reduce the interference without changing the total transmitted data rate. The performance obtained by minimizing the interference resulting from each user is studied in terms of BER, transmission data rate and the system capacity supporting multiple users. The theoretical analysis and simulation results show that the proposed algorithm substantially outperforms those reported previously.     

自适应OFDMA系统无线资源分配和分组数据调度算法的研究

在对无线资源分配和下行链路分组数据调度算法研究的基础上，提出了一种适应于自适应OFDMA系统的联合算法，即K＆H／MPF算法。理论分析和仿真结果表明：该算法在满足不同用户QoS要求的前提下，不但能够提供比多载波正比公平调度器更高的容量增益，而且以极大的灵活性实现了用户数据的公平发送。     

Fairness based resource allocation for uplink OFDMA systems

This article investigates two fairness criteria with regard to adaptive resource allocation for uplink orthogonal frequency division multiple access （OFDMA） systems. Nash bargaining solution （NBS） fairness and proportional fairness （PF） are two suitable candidates for fairness consideration, and both can provide attractive trade-offs between total throughput and each user＇s capacity. Utilizing Karush-Kuhn- Tucker （KKT） condition and iterative method, two effective algorithms are designed, to achieve NBS fairness and proportional fairness, respectively. Simulation results show that the proposed resource allocation algorithms achieve good tradeoff between the overall rate and fairness, with little performance loss from the total capacity.     

Discrete bit loading and power allocation for OFDMA downlink with minimum rate guarantee for users

Performance optimization of the communication networks with quality of service (QoS) considerations for all active users is of great practical importance in highly delay-sensitive applications like multipoint videoconferences and interactive video games. Using minimum data rate as the primary criterion for the QoS and the BER as a second one, in this paper, we provide the optimum discrete bit loading for an OFDMA downlink in which the QoS of all users are satisfied. We formulate the problem and solve the dual problem efficiently and without any suboptimality. Albeit the problem is non-convex, it has been shown that the duality gap tends zero in practical scenarios. We propose a novel approach to solve the dual problem by decomposing dual function and finding discrete rate allocation solution for practical applications. Also, we present a novel fast converging iterative algorithm to find the solution with much less complexity compared to that of well-known ellipsoid optimization algorithm. We analyze the complexity of these solutions, and using simulation results, show the superiority of our novel approach.     

OFDMA系统下行链路自适应带宽与子载波分配方案

该文分析了OFDMA系统下行链路自适应资源分配问题,在系统总功率约束下提出了最小化系统中断概率的次最佳两步子载波分配算法。首先分析用户带宽分配与子载波功率分配特点,在此基础上提出了根据系统可用资源、用户QoS要求及信道状态为用户分配带宽和子载波的两步分配算法。仿真结果表明,该文提出的算法能在极小化系统中断概率的同时满足总功率约束。     

考虑整数比特率及公平性的认知无线电OFDMA功率分配算法

在基于正交频分多址(OFDMA)的认知无线电系统中,每个认知用户在实际中都是以整数比特进行传输,而以往的速率取整算法只考虑了单认知用户。针对这种情况,提出了一种新的速率取整算法,该算法在原有算法的基础上进行了改进,让每个子载波最多参与一次速率的调整,从而使其在应用于多认知用户时保证了速率取整时的公平性,同时总的传输比特率比原算法有了一定的提高。仿真结果表明,所提算法有效提高了各认知用户在速率取整时的公平性。     

Joint subcarrier and power allocation for uplink relay‐enhanced OFDM systems

There has been a lot of research works considering the resource allocation of the downlink multihop orthogonal frequency division multiplexing systems. However, due to the distributed nature of the uplink power constraints, the resource allocation in the uplink multihop systems, where multiple mobile stations transmit to one base station with the aid of one or many relay stations, has much difference and has not been well investigated so far. In this paper, we originally study the joint subcarrier and power allocation problem for the uplink dual‐hop transmission with the aim to maximize the system transmit rate. The resource allocation problem is approximated to be a concave maximization problem. By using mathematical decomposition techniques, the problem is first decoupled and solved by the proposed near‐optimal method, which has low‐computation complexity. Then, our algorithm is extended to the case with subcarrier matching on the dual hops. Numerical results show that our proposed algorithm improves the system transmission rate. Compared with the equal power allocation schemes, our algorithm can achieve significant gain in system transmit rate. Copyright © 2010 John Wiley & Sons, Ltd.     

基于ESPRIT算法的子载波交织型OFDMA上行链路频偏估计

频率同步问题对于OFDMA系统来说至关重要。本文针对子载波交织分配的OFDMA系统上行链路，利用其接收信号周期性的结构特征，提出一种基于ESPRIT算法的多用户频偏估计算法，通过子空间旋转不变的特点估计各用户的载波频偏。仿真表明，利用该算法进行频偏估计具有良好的准确性。     

Optimal power and subcarrier allocation with partial side information for downlink OFDMA system

In this paper,we investigate the power and subcarrier allocation issue in the case of partial side information for downlink orthogonal frequency division multiple access(OFDMA)system.Relaxation method is utilized to characterize the necessary conditions of the optimal solution and the uniqueness of the optimal solution is proved.The game theoretical concept,surplus function is also introduced to analyze the optimal solution.Based on the theoretical analysis,we propose iterative surplus balancing algorithm(ISBA)that can jointly assign the power and subcarriers in multiple rounds,and then the optimality of ISBA is proved.Simulation results are presented to show the characteristics of the theoretical analysis and ISBA.     

Dynamic subcarrier and power allocation based on cooperative game theory in symmetric cooperative OFDMA networks

In order to improve the efficiency and fairness of radio resource utilization,a scheme of dynamic cooperative subcarrier and power allocation based on Nash bargaining solution(NBS-DCSPA) is proposed in the uplink of a three-node symmetric cooperative orthogonal frequency division multiple access(OFDMA) system.In the proposed NBS-DCSPA scheme,resource allocation problem is formulated as a two-person subcarrier and power allocation bargaining game(SPABG) to maximize the system utility,under the constraints of each user’s maximal power and minimal rate,while considering the fairness between the two users.Firstly,the equivalent direct channel gain of the relay link is introduced to decide the transmission mode of each subcarrier.Then,all subcarriers can be dynamically allocated to the two users in terms of their selected transmission mode.After that,the adaptive power allocation scheme combined with dynamic subcarrier allocation is optimized according to NBS.Finally,computer simulation is conducted to show the efficiency and fairness performance of the proposed NBS-DCSPA scheme.     

Joint Downlink Scheduling and Radio Resource Allocation for User-Individual QoS in Adaptive OFDMA Wireless Communication Systems

1Introduction Futurewirelessandmobilecommunicationsystems areexpectedtoofferhigherdatarates,tosupporta largenumberofsubscribersandtoensurethefulfillment ofQualityofService(QoS)requirements,giventhe limitedavailabilityoffrequencyspectrumandtimevary ingchan…     

OFDM系统中的自适应比特功率分配算法

正交频分复用(OFDM)系统各子信道具有不同的衰落特性,如果采用相同的调制方式,则不能更好地利用系统资源。在系统容量受限和误比特率一定的条件下,文章提出了一种高效的OFDM自适应比特功率分配算法。在要求误比特率BER<10-3时,该算法与Chow算法相比,发射总功率减小了2.5 dB;与Hughes-Hartogs算法相比,系统消耗的总时间也明显缩短。仿真结果验证了算法的有效性。