QoS‐driven jointly optimal subcarrier pairing and power allocation for OFDM amplify‐and‐forward relay systems

In this paper, we investigate the quality‐of‐service (QoS) driven subcarrier pairing and power allocation for two‐hop amplify‐and‐forward OFDM relay systems. By integrating the concept of effective capacity, our goal is to maximize the system throughput subject to a given delay QoS constraint. We propose a jointly optimal subcarrier pairing and power allocation scheme, which can be implemented with two separate steps. First, pair the subcarriers over the source‐relay channel and relay‐destination channel by the descending order of the subcarriers’ channel gains. Second, by making use of the derived equivalent end‐to‐end channel gains of the subcarrier pairs, optimally allocate power over the subcarrier pairs, and then optimally partition the power of the subcarrier pairs between the source and the relay. The simulation results show that our proposed scheme can efficiently provide different levels of delay QoS guarantees, even if under stringent delay QoS constraints. The simulation results also verify that our proposed scheme shows significant superiorities over the other existing schemes. Copyright © 2013 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.     

A joint subcarrier selection and power allocation scheme using variational inequality in OFDM‐based cognitive relay networks

Introducing orthogonal frequency division multiplexing (OFDM) into cognitive radio (CR) can potentially increase the spectrum efficiency, but it also leads to further challenges for the resource allocation of CR networks. In OFDM‐based cognitive relay networks, two of the most significant research issues are subcarrier selection and power allocation. In this paper, a non‐cooperative game model is proposed to maximize the system throughput by jointly optimizing subcarrier selection and power allocation. First, taking the direct and relay links into consideration, an equivalent channel gain is presented to simplify the cooperative relay model into a non‐relay model. Then, a variational inequality method is utilized to prove the existence and uniqueness of the Nash equilibrium solution of the proposed non‐cooperative game. Moreover, to compute the solution of the game, a suboptimal algorithm based on the Lagrange function and distributed iterative water‐filling algorithm is proposed. The proposed algorithm can jointly optimize the process of subcarrier selection and power allocation. Finally, simulation results are shown to demonstrate the effectiveness of the proposed joint subcarrier selection and power allocation scheme. Copyright © 2015 John Wiley & Sons, Ltd.     

基于子载波加权的峰均比与带外辐射联合降低方法

针对OFDM系统中PAPR与OBP的降低互相矛盾的问题,提出了一种新的基于子载波加权的联合优化方法。该方法将符号数据与最优加权向量相乘达到同时降低系统PAPR与OBP的目的;为降低计算复杂度,利用改进的遗传算法求解最优加权向量。新方法频谱效率高,且无需发送额外信息,并可根据当前通信环境,通过改变折衷系数实现对PAPR与OBP降低程度的灵活控制。仿真结果表明,与采用两步优化降低PAPR与OBP的方法相比,该方法能更有效地降低OFDM系统的PAPR与OBP,且计算复杂度低,实现十分简单,具有很强的实用性。     

Discrete polynary coding immune clonal selection‐based joint subcarrier and power allocation in uplink cognitive OFDM network

Cognitive radio has been considered to be one of the main technologies to solve the problem of low spectrum utilization, while the adaptive allocation of network resource is one of the key technologies. A discrete polynary coding immune clonal selection (DPICS)‐based joint subcarrier and power allocation algorithm is proposed to solve the resource allocation problem in uplink cognitive OFDM networks. The novelties of DPICS include the following: A unique coding method is adopted to deal with multi‐value discrete variables. Compared with the traditional methods, the proposed method can acquire the shortest code. Meanwhile, the constraints of the subcarrier allocation are avoided. A heuristic mutation scheme is used to direct the mutation. Subcarriers are reallocated randomly to the secondary users with larger homotactic noise, which has a large probability to produce the optimal solution and improves the searching process. Subcarriers and power are allocated simultaneously, which is different with the traditional biphasic resource allocation algorithms. The biphasic resource allocation algorithms cannot acquire the subcarrier allocation result and power allocation result simultaneously, which makes the final result imprecise. The proposed algorithm avoids this situation and improves the accuracy of the final result. Compared with state‐of‐the‐art algorithms, the proposed algorithm is shown as effective by simulation results. Copyright © 2014 John Wiley & Sons, Ltd.     

雷达通信一体化子载波和功率联合分配方法

雷达通信一体化系统是缓解无线电频谱拥塞和频谱资源短缺的高效解决方案。在雷达的最小信号噪声比和最小通信传输速率的约束条件下,通过构建混合整数非线性优化模型,提出了子载波和功率联合分配方法,实现系统总发射功率的最小化。首先将优化模型转化为线性模型并添加罚因子,然后选择用于雷达或通信目的的子载波。考虑到雷达性能和通信性能评价标准的差异,对用于雷达或通信目的子载波设置不同的发射功率约束,最终通过循环优化实现子载波和功率的联合分配。数值仿真结果表明,所提方法显著节约了功率资源。     

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 power,subcarrier and subframe allocation in Multihop relay networks

In this paper we study the problem of subframe, subchannel and power allocation in OFDMA‐based multihop relay networks. The system consists of a base station (BS), a number of relay stations (RS) and mobile stations (MS). We consider frame by frame scheduling, where the frame is divided into two subframes such as BS‐RS and RS‐MS subframes. We study two different problems, satisfying link rate requirements with minimum‐weighted total power and maximizing proportional fairness. For the first problem, we find the optimal solution and also propose a less complex subframe and bandwidth allocation scheme with good performance. For the second problem, we propose an algorithm that outperforms an existing scheme with less feedback. Copyright © 2009 John Wiley & Sons, Ltd.     

Optimal resource allocation for multiple network‐coded two‐way relay in orthogonal frequency division multiplexing systems

This paper studies optimal resource allocation for multiple network‐coded two‐way relay in orthogonal frequency division multiplexing systems. All the two‐way relay nodes adopt amplify‐and‐forward and operate with analog network coding protocol. A joint optimization problem considering power allocation, relay selection, and subcarrier pairing to maximize the sum capacity under individual power constraints at each transmitter or total network power constraint is first formulated. By applying dual method, we provide a unified optimization framework to solve this problem. With this framework, we further propose three low‐complexity suboptimal algorithms. The complexity of the proposed optimal resource allocation (ORA) algorithm and three suboptimal algorithms are analyzed, and it is shown that the complexity of ORA is only a polynomial function of the number of subcarriers and relay nodes under both individual and total power constraints. Simulation results demonstrate that the proposed ORA scheme yields substantial performance improvement over a baseline scheme, and suboptimal algorithms can achieve a trade‐off between performance and complexity. The results also indicate that with the same total network transmit power, the performance of ORA under total power constraint can outperform that under individual power constraints. Copyright © 2012 John Wiley & Sons, Ltd.     

Joint subcarrier and power allocation in uplink OFDMA systems

In this letter, we focus on joint subcarrier and power allocation in the uplink of an OFDMA system. Our goal is to maximize the rate-sum capacity in the uplink. For the purpose, we formulate an optimization problem subject to subcarrier and power constraints and draw necessary conditions for optimality, from which we derive joint subcarrier and power allocation algorithms. Simulation results show that our proposed scheme enhances the system capacity, providing almost near optimal solutions with low computational burden.     

Energy efficiency based multi-relay selection and power allocation in OFDM cooperation networks

Getting along with the improvement of green communications, the energy efficiency （EE） of wireless network becomes more and more important. However, in nmlti-relay-assisted systems, the related work obviously depends on the end-to-end performance, whereas EE of relays has not attracted enough attention. The authors propose an orthogonal frequency division multiplexing （OFDM） multi-relay system based on amplify and forward （AF） mode. Taking incorporating EE and remaining energy as factor, decision criteria of attending cooperation is designed. The EE based asynchronous power iteration method is presented, and the existence and convergence of nash equilibrium （NE） is proven. Furthermore, a joint algorithm in subcarrier pairing, relay selection and power allocation is given. Genetic algorithm （GA） and iteration method are integrated to improve the convergence speed additionally. Simulation demonstrates the obvious improvement of EE, decrease of power consumption and increase of lifetime in relays of this algorithm with the constraint of minimum data transmission rate.     

OFDM系统中动态子信道和功率的分配

在分析一种多用户OFDM系统中自适应子信道和比特功率分配算法的基础上,根据多径频率选择性衰落信道的瞬时特性,动态地为多用户分配子信道和传输比特数,并服从MA优化准则.并且进一步考虑了系统中有固定速率用户和可变速率用户同时存在的情况:在子信道分配时,先给固定速率的用户分配子信道,再给可变速率用户按照子信道链路增益最大化分配剩余的子信道;在信号发射功率分配上,按照"注水"法则分配,链路增益大的子信道分配的功率大,链路增益小的子信道分配的功率小,则系统的目标函数,总传输速率可以达到最大.仿真证明了此方案优于一般的方案.     

Power distribution methods for MIMO‐OFDM systems and field experimentations

In this paper, we propose several power allocation schemes for multi‐input multi‐output (MIMO) orthogonal frequency division multiplexing (OFDM) transmission based on the minimization of an approximated bit error rate (BER) expression, and we evaluate the different solutions via field trial experimentations. The methods illustrated in this paper, serve to allocate power among the different transmit antennas and the different subcarriers which compose the MIMO OFDM transmitted signal. Several solutions are available to perform power allocation. Frequency domain power allocation, spatial domain power allocation and combined spatial and frequency power allocation are evaluated. We first review and describe the analytical solution for each power allocation scheme and then evaluate the complexity in terms of both computational operations and BER performances. Simulation results show the performance in term of BER and link the advantage of each possibility of power distribution with the associated complexity. Copyright © 2009 John Wiley & Sons, Ltd.     

Joint power allocation and subcarrier pairing in OFDM-based cooperative relaying system

This paper proposes rate-maximized (MR) joint subcarrier pairing (SP) and power allocation (PA) (MR-SP&PA),a novel scheme for maximizing the weighted sum rate of the orthogonal-frequency-division multiplexing (OFDM) relaying system with a decode-and-forward (DF) relay.MR-SP&PA is based on the joint optimization of both SP and power allocation with total power constraint,and formulated as a mixed integer programming problem in the paper.The programming problem is then transformed to a convex optimization problem by using continuous relaxation,and solved in the Lagrangian dual domain.Simulation results show that MR-SP&PA can maximize the weighted sum rate under total power constraint and outperform equal power allocation (EPA) and proportion power allocation (PCG).     

Joint downlink and uplink resource allocation for multi-carrier SWIPT system

A multi-carrier simultaneous wireless information and power transfer (SWIPT) communication system including one base station (BS) and one user was investigated,where both uplink and downlink adopt orthogonal frequency division multiplexing (OFDM).In the downlink,the BS transmited information and power to the user simultaneously.In the uplink,the user transmited information to the BS by using the power harvested from the BS in the downlink.The weighted sum of the downlink and uplink achievable rates by jointly optimizing subcarrier allocation and power allocation of the uplink and downlink were aimed to maximized.An optimal algorithm to solve the joint resource allocation problem was proposed,which was based on the Lagrange duality method and the ellipsoid method.Finally,the result shows the performances of the proposed algorithm by computer simulations.     

Resource allocation scheme in two-way multi-relay OFDM system

A joint optimization scheme for power allocation and subcarrier pairing under high SNR in two-way multi-relay OFDM system was proposed.Unlike those schemes in which relays use subcarriers separately,all the relays were allowed to forward signal on each subcarrier pair for providing much space diversity.With the constraint of total system power,the proposed scheme firstly allocated each relay power with Cauchy inequality with the assuming that the total relay power was fixed.Then the dichotomy was used to calculate the power allocation between the source node and the relay node by maximizing the equivalent channel gain for different subcarrier pairs.Lastly,the power of different subcarrier pairs was allocated by convex programming,and the subcarriers were paired by Hungarian algorithm to obtain the maximum system capacity.There was no optimal power allocation method with low complexity because of the complexity of the power allocation algorithm in two-way multi-relay networks.This algorithm greatly reduces the complexity of power allocation and simulation results show that the proposed scheme outperforms the relay selection scheme and the relays use subcarriers separately scheme.     

非线性条件下多用户OFDM系统的自适应资源分配

为了提高多用户正交频分复用(OFDM)系统的容量和功率效率，可以根据用户的服务质量(QoS)采用一种自适应的子载波、比特和功率的分配策略。然而这样使得OFDM信号更易于受非线性的影响，使用户的信噪比下降，导致QoS得不到满足。本文将研究非线性对用户最终信噪比的影响，并提出一种在这样的系统中保证用户QoS的资源分配算法，使总发射功率最小。文章最后使用该算法进行仿真，分析非线性对系统性能的影响。     

Joint subchannel and power allocation in multiuser OFDM systems with minimal rate constraints

In this paper, we study the adaptive resource allocation in multiuser orthogonal frequency division multiplexing (OFDM) systems. We try to maximize the sum capacity of an OFDM system with given transmission power budget, while meeting users' minimal rate requirements. Unlike other resource allocation schemes, which generally separate subchannel allocation and power distribution into independent procedures, our proposed algorithm implements joint subchannel and power allocation. Given a set of subchannels, the required power to satisfy a user's minimal rate constraint is calculated by water‐filling policy. Then, the user who requires the maximum power to meet the rate requirement has a priority to obtain an additional subchannel. The procedure continues until all subchannels are consumed, by which time the consumed power to meet all users' rate requirements is also worked out. Finally, the margin power is allocated among all subchannels in an optimal manner to maximize the sum capacity of the OFDM system. Simulation results show that our proposed algorithm performs better than other existing ones. The solution produced by our proposed algorithm is close to the upper bound, while its complexity is relatively lower compared with other methods, which makes it attractive for applications. Copyright © 2012 John Wiley & Sons, Ltd.     

多用户OFDM系统子载波分配算法研究

采用改进的贪婪算法分配时隙的无线资源,根据用户业务的QoS和数据队列信息确定用户的优先权,并在获知信道状态信息条件下,按照传输比特消耗功率最小原则搜索所有子载波信道,为用户动态分配子载波和比特。仿真结果表明,在两种传输速率要求下,当接入用户数相同时,改进算法比传统贪婪算法减少功率消耗3.9622W;改进算法多消耗1.9858W功率却增加了2个接入用户,用户消耗平均功率比前者少2.2456W/用户。     

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。