OFDM系统中的一种新的比特功率分配算法

针对自适应OFDM系统中满足用户QoS(这里主要指用户带宽及误码率这两个指标)要求的比特功率分配这一问题,提出了一种新的算法,该算法以每次比特分配时,使得每比特(一次可分配多比特信息)的功率代价最小为原则,获得了良好的性能,仿真结果表明,该算法在满足用户QoS要求的情况下,其发射总功率比现有的同类算法小,性能更佳。摘要     

OFDM系统的功率和比特分配算法

OFDM(正交频分复用)是高速无线数据通信系统最有力的候选技术之一。在OFDM系统中,能够根据各个信道的衰减对各载波的发送功率和传输的比特数进行动态分配,从而使系统性能达到最佳。首先介绍了功率和比特分配的最优算法、贪婪算法,并针对贪婪算法迭代次数多的不足,提出了一种改进的贪婪算法。该算法通过修改迭代过程的初始条件,大大简化了贪婪算法的计算复杂度。仿真结果表明,改进的贪婪算法能够在保持发送比特总数不变的同时有效减少迭代的次数。     

一种无线OFDM系统中的高效功率和比特分配算法

在限定无线OFDM通信系统的传输速率和最大误码率的情况下,该文提出了一种最小化发射功率的高效功率和比特分配算法。该算法首先利用注水水平和系统传输速率之间的关系求出无需预设步长和初始值的注水水平迭代公式,然后在部分子载波上使用简化的Greedy算法进行强制收敛。由于充分地利用了注水算法和Greedy算法的优点,该文算法不仅有效地避免了传统自适应算法的收敛性、初始值和步长选择等问题,而且计算效率更高。仿真结果验证了该算法的有效性。     

自适应比特功率分配的MIMO OFDM系统性能

该文首先分析了多天线发射和接收(MIMO)的OFDM系统模型。然后针对在多径衰落信道下,OFDM中一些深度衰落的子载波降低了系统性能。该文把一般多载波系统中的自适应比特功率分配算法推广应用到多天线OFDM系统中。同时研究了自适应MIMO OFDM系统的频谱效率。仿真结果表明,自适应比特功率分配提高了MIMO OFDM的误比特率性能和频谱效率。     

OFDM系统功率和比特分配算法研究

该文研究OFDM系统在总功率和误比特率限定下最大化传输速率的问题,并且考虑实际系统中整数比特的限制,提出基于灌水法则的两种比特分配算法--改进的贪婪算法和对分灌水线搜索法,两种算法在计算复杂度上分别比贪婪算法和迭代灌水线搜索法小。仿真结果表明,改进的贪婪算法在性能上十分接近于贪婪算法,但是计算复杂度仅是贪婪算法的10%-30%,而对分灌水线搜索法在信噪比大于10dB的时候只要5-7次迭代便可以达到与贪婪算法只相差0.5%的性能。     

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。     

基于注水原理的快速功率和比特分配算法

提出了一种新的基于注水原理的低计算复杂度的快速功率和比特分配算法.在功率最小化问题上,通过对公式的变形和求解,使得问题的求解形式与注水算法一致.利用注水性质快速调整注水线从而移除了复杂的搜索注水线计算,实现了功率最小化快速功率和比特分配算法.仿真结果表明,与已有的算法相比,提出的算法节省了大量的计算时间.     

一种快速的OFDM系统比特与功率分配算法

针对OFDM系统提出一种基于裕度自适应(Margin Adaptive)的快速比特与功率分配算法,改进了Greedy(贪婪)算法。新算法利用不同子载波之间信道信噪比的对数关系,将子载波进行分组;在分配比特时,降低了原Greedy算法的循环迭代次数。仿真结果表明,在满足相同的通信服务质量(QoS)前提下,提出的分配算法,显著降低了算法的复杂度,发射功率增量很小,具有实用意义。     

MC-CDMA系统中的自适应比特和功率分配算法

在研究MC-CDMA系统和自适应比特分配技术的基础上,提出了一种适合MC-CDMA系统的自适应比特和功率分配算法。本算法以扩频支路为单位,根据系统中各子载波的不同信道增益,动态地分配数据比特和发射功率。仿真结果表明,使用该算法可以大大减小发射功率,提高系统性能。     

OFDM系统中自适应比特分配算法分析

对单用户OFDM系统的3种自适应比特加载算法:Hugehes-Hartogs比特功率梯度分配算法、Chow算法和简单分块加载(SBLA)算法进行了仿真,分析比较了3种算法的复杂度和抗噪声性能。仿真结果表明:每种算法各有其优缺点和适用情况,可以根据不同的工程需求选择不同的算法。Hugehes-Hartogs算法能使系统发射总功率达到最低;Chow算法具有较好的抗噪声性能;SBLA算法的性能介于上述2种算法之间,并且具有较低的复杂度。     

Optimal power allocation for two-way relaying over OFDM using physical-layer network coding

In this paper,a network scenario of two-way relaying over orthogonal frequency division multiplexing(OFDM) is considered,in which two nodes intend to exchange the information via a relay using physical-layer network coding(PLNC).Assuming that the full channel knowledge is available,an optimization problem,which maximizes the achievable sum rate under a sum-power constraint,is investigated.It is shown that the optimization problem is non-convex,which is difficult to find the global optimum solution in terms of the computational complexity.In consequence,a low-complexity optimal power allocation scheme is proposed for practice implementation.A link capacity diagram is first employed for power allocation on each subcarrier.Subsequently,an equivalent relaxed optimization problem and Karush-Kuhn-Tucker(KKT) conditions are developed for power allocation among each subcarrier.Simulation results demonstrate that the substantial capacity gains are achieved by implementing the proposed schemes efficiently with a low-complexity computational effort.     

Low complexity bit allocation algorithm for OFDM systems

A bit allocation algorithm is presented for orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic–geometric means inequality. Consequently, this algorithm has a simple procedure and low computational complexity. Copyright © 2008 John Wiley & Sons, Ltd.     

能量收集双向中继网络的中继选择和功率分配

结合能量收集技术,研究了放大转发双向中继网络的系统性能。基于双向中继系统中的两个端到端信噪比平衡准则,推导出了单中继选择情况下信源最优的功率分配方案和中继最优的能量收集比例。仿真结果证明所提方法能够实现最好的系统性能。通过比较发现,能量收集双向中继网络比传统双向中继网络能够实现更高的传输速率。     

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.     

分布式双向中继选择算法及用户功率分配

针对放大转发的瑞利双向中继信道的节点选择问题,提出了基于部分信道信息的分布式双向中继选择算法。算法通过计算双向链路的接收信噪比,推导出满足目标接收信噪比的转发阈值,各中继节点根据该阈值决定是否参与转发,从而实现分布式选择。此外,考虑用户总功率受限的情况,在分布式中继选择基础上提出了优化功率分配策略,使双向信道的接收信噪比更加接近。仿真结果表明,分布式中继选择算法与最优多中继算法的系统传输速率相似,计算复杂度大大降低,尤其是在中继数目增大的情况下更加明显。优化功率分配策略能进一步提高系统能量效率,在相同性能下可节省7%左右的功率。     

Residual energy based multi-relay selection and power allocation scheme in two-way relay network

In this paper, we have proposed a multi-relay selection and power allocation scheme for two-way relay network which aims to maximize the sum-rate of two-way relay system. First, to prolong network lifetime, a multi-relay selection strategy is proposed in which both channel state information （CSI） and remaining energy （RE） are considered. Next, a multi-relay power allocation algorithm based on convex optimization （MRPA-CO） is presented. To reduce the computational complexity, it can be divided into two steps： terminal nodes power allocation （TNPA） and relay nodes power allocation （RNPA）. Simulation results indicate that the proposed relay selection strategy can significantly prolong network lifetime compared to other relay selection strategies which consider CSI only, and the MRPA-CO algorithm has great advantage over equal power allocation （EPA） on sum-rate in two-way relay network.     

Joint relay selection and power allocation algorithm in two-way relay networks with proportional fair constraint

In this paper,we consider the joint relay selection and power allocation problem for two-way relay systems with multiple relay nodes.Traditionally,relay selection schemes are primarily focused on selecting one relay node to maximize the transmission sum rate or minimize the outage probability.If so,it is possible to cause certain relay nodes overloaded.In addition,the joint relay selection and power allocation problem is a mixed integer program problem and prohibitive in terms of complexity.Therefore,we pro...     

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.     

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).