车联网中V2R通信功率分配策略

针对车载应用对车辆与路侧单元(V2R)的通信质量及系统吞吐量要求越来越高,提出V2R通信功率分配策略,以提高通信链路质量及系统的吞吐量。该策略利用博弈论对功率分配过程进行分析并找出最优分配方案。当效用函数经过多次迭代而达到纳什均衡时,表明系统已经获得最优的功率分配方案。仿真结果表明,本文提出的车联网功率分配策略有利于减小各通信链路之间的干扰,且达到了提升系统吞吐量的目的。     

具有时延QoS保证的OFDM中继系统子载波配对与功率分配算法

 本文研究具有直接通信链路的OFDM解码转发(Decode-and-Forward,DF)中继系统的子载波配对与功率分配算法,目标是在满足业务时延QoS要求的前提下最大化系统容量.利用有效容量模型,首先把OFDM DF中继系统的子载波配对与功率分配问题形成为混合整数规划问题,然后把其转化为连续松弛凸规划问题,利用凸优化方法得到原问题的最优解,从而提出了一种联合最优的子载波配对与功率分配迭代算法.理论推导结果和仿真结果表明,最优子载波配对与功率分配不仅取决于子载波的信道增益,还取决于业务的时延QoS要求.与已有算法相比,本文算法获得的有效容量最大.     

多用户多速率OFDM中的子载波分配和功率控制

该文基于对多用户多速率正交频分复用(OFDM)系统性能的分析,提出了子载波分配和功率控制方案。在采用P-QAM调制的下行链路中,如已知所有子信道的信息状态(CSI),在满足每一个用户的服务质量的前提下,先给固定速率的用户分配最优子信道,再给变速率的用户按照子信道链路增益最大化分配剩余的子信道;每一个用户分配的子信道数目,由链路增益的取值区间决定。信号发射功率则按照注水法则分配: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,则系统的总传输速率可达最大。仿真结果证明了该文提出的分配方案优于Jang的分配方案。     

多业务CDMA系统的速率控制与功率分配

移动通信中速率控制和功率分配是无线资源管理的基础，对于保证业务的质量有重要的作用。本文研究了多码CDMA系统多业务情况下的速率控制和功率分配问题。通过对业务分优先级，速率控制可保证不同业务质量要求，同时总的吞吐量最大。建立了多码CDMA系统的归一化链路增益矩阵，功率分配归结为求解该矩阵在有约束条件下的最大实特征值。本文算法通过业务分级给不同用户的分配传输速率，并通过基于信噪比的功率分配，可充分利用了系统资源，仿真验证了该算法的性能。     

基于速率约束的OFDM中继链路能效最优资源分配策略

该文研究解码转发(DF)模式的OFDM中继链路的能效最大化资源分配问题。与现有典型的固定速率最小化发射功率或无约束最大化能效算法不同,该文考虑电路功率消耗的前提下,将问题建模为以最大化系统能效为目标,同时考虑用户最小速率需求、源节点S和中继节点R各自总发射功率约束下的联合子载波配对和最优功率分配问题。证明了速率和功率联合约束条件下中继链路全局能效最优解的唯一性,在此基础上提出一种低复杂度联合最优资源分配策略。仿真结果表明,该文所提方案能够在最小速率和S/R节点最大发射功率约束下自适应分配功率资源,实现系统能效最优,并能够降低链路的中断概率。     

最优功率分配的发送分集

第三代移动通信系统中,为了更好地支持高速率数据的传输,在下行链路使用了发送分集技术犤1犦犤2犦。考虑MISO(Multiple-InputSingle-Output)信道,对开环发送分集方案,提出了使用最优功率分配的新方案,并推导出最优功率权值。理论分析表明,与开环发送分集相比,最优功率分配的发送分集的平均信噪比增益为1.25dB。     

NOMA系统中利用共轭梯度法的功率分配方案

通过功率分配,5G通信的关键技术——非正交多址（NOMA）实现发射功率域的多用户复用,有效提高了频谱效率。不同的功率分配方案直接影响系统的吞吐量,针对NOMA下行链路现有功率分配算法存在的局部最优问题,提出了一种利用共轭梯度法的最优功率分配方案,采用共轭梯度法求解用户的加权和速率最大化的优化问题。现有理论证明,该方法可以收敛到全局最优解。仿真结果表明,该方法性能优于已有的固定功率分配（FPA）算法和分数阶发射功率分配（FTPA）算法,且此非正交多址（NOMA）系统性能明显优于正交多址（OMA）系统。      

基于能效的解码转发中继OFDM链路自适应功率分配方案研究

在能效问题中,设备本身的电路功耗已成为不可忽略的一部分,故将中继引入无线网络之后势必会带来更严重的电路功耗.该文基于解码转发(DF)中继OFDM频率选择性链路,结合电路所耗功率,提出一种最优能效功率分配方法,求得DF中继链路能效上界,同时分析了速率和功率限制对能效的影响.仿真结果表明,该文所提基于能效的功率分配算法可求出最大化能效的最优功率解,并能在保证较高速率的同时获得最好的系统能效.     

非对称信道下协作通信系统中断概率的研究

首先建立了非对称信道下协作系统的数学模型,考虑了源节点到目的节点的直通链路,利用特征函数法推导出协作系统的平均中断概率公式,通过仿真验证了该中断概率公式的精确性,理论和仿真都表明协作系统的中断概率和中继节点的个数、位置分布以及协作系统的功率分配因子有着密切关系,并且考虑源到目的节点的直通链路相对于不考虑直通链路的情况具有更高的性能增益;然后又在此公式基础卜就协作系统中继节点的位置分布对最优功率分配因子的影响进行了仿真分析,并指出协作系统的最优功率分配因子受制于中继节点的位置分布情况.     

双向协作系统的中继选择和功率分配策略

针对瑞利衰落信道下双向多中继协作通信系统,为了降低中断概率,提出了一种基于最小化中断概率的中继选择策略和功率分配方案。首先联合考虑两条链路的中继节点处信噪比和信道增益实现双链路中继选择,然后推导出一种新的最优中继下双向放大转发协作中断概率的近似表达式上界,并利用凸优化求解得到使中断概率最小的最优功率分配解。仿真结果表明,与现有策略相比,提出的策略能够明显降低系统中断概率和误码率,显著提高系统性能。     

一种CDMA网络多业务的呼叫允许控制算法

现今无线网络中的多媒体业务具有很大需求。该文对多业务CDMA通信系统容量进行分析,引入有效带宽概念,提出一种呼叫允许控制资源分配优化算法(CAC-RA)。此算法将多媒体业务分为实时业务和非实时业务,通过对自适应实时业务采用马尔科夫模型,对非实时业务采用排队模型,将两模型合并生成的的利益函数采用非线性规划,使呼叫允许控制、切换策略和资源分配问题同时得到解决。实验数据显示CAC-RA算法实现了合理的资源利用和最大的利益值,能较好地适应多业务CDMA网络。     

多业务蜂窝CDMA系统中的呼叫接纳控制策略

基于码分多址(CDMA)技术的第三代(3G)移动通信系统将支持多种业务传输,有效的呼叫接纳控制策略将使系统在满足各类业务不同QoS要求的同时,能够为更多的用户提供服务,该文首先分析了多业务蜂窝CDMA系统的剩余容量与QoS约束间的关系,接着提出了适用于任意多类业务环境、基于信号干扰比(SIR)测量的两种呼叫接纳控制策略,局部策略与全局策略,并通过大量计算机仿真研究了两种策略在业务均匀分布和非均匀分布环境下的性能,仿真结果表明,在两种业务分布情况下,全局策略的性能部优于局部策略。     

Open-loop power control error in cellular CDMA overlay systems

Adaptive power control has widely been used in DS/CDMA systems to overcome the so-called “near-far” problem. This paper studies the adaptive open-loop power control of a cellular CDMA system, which is overlaid in the downlink by a narrowband signal. The effects of downlink power allocation schemes to power control error in the presence of narrowband interference are analyzed. In order to get a minimum power control error in the CDMA overlay situations, an optimum downlink power allocation scheme is used, which works well for a wide range of signal to narrowband interference ratio     

A novel dynamic cell configuration scheme in next-generation situation-aware CDMA networks

To balance the time-varying traffic load between cells, caused by user mobility and diverse applications, it is crucial for next-generation code-division multiple-access (CDMA) cellular networks to configure cell coverage and capacity dynamically. In this paper, we show that pilot power allocation is highly coupled to other facets of radio resource management. We propose a novel dynamic cell configuration scheme for multimedia CDMA cellular networks, based on reinforcement-learning, which takes into account pilot, soft handoff, and maximum link power allocations, as well as call admission control mechanisms. Simulation results demonstrate the effectiveness of the proposed scheme in situation-aware CDMA networks.     

An Iterative Approach to the Power Control Problem in Multi-Service CDMA Systems: Distributed Algorithms and their Convergence

In this paper we present two decentralized Iterative Power Control Algorithms (IPCAs) for the uplink and downlink communication in multi-service CDMA wireless environments in order to expand the system capacity while at the same time satisfy the various QoS requirements. The proposed dynamic IPCAs are decentralised in the sense that they can be implemented in a distributed mode at the individual cell sites and mobile stations based on local measurements and information, and without the need of co-ordination between the different cells. The main feature of these two power control algorithms is that they combine the allocation as well as the correction of power in a multi-service wireless system. For the algorithms presented here whenever power settings exist for which all users meet the QoS requirements we prove and demonstrate exponentially fast convergence to the optimal power values. Finally we present some numerical results to assess the performance of our algorithms by applying them in some test cases.     

Multiuser Distortion Management of Layered Video over Resource Limited Downlink Multicode-CDMA

Transmitting multiple real-time encoded videos to multiple users over wireless cellular networks is a key driving force for developing broadband technology. We propose a new framework to transmit multiple users' video programs encoded by MPEG-4 FGS codec over downlink multicode CDMA networks in real time. The proposed framework jointly manages the rate adaptation of source and channel coding, CDMA code allocation, and power control. Subject to the limited system resources, such as the number of pseudo-random codes and the maximal power for CDMA transmission, we develop an adaptive scheme of distortion management to ensure baseline video quality for each user and further reduce the overall distortion received by all users. To efficiently utilize system resources, the proposed scheme maintains a balanced ratio between the power and code usages. We also investigate three special scenarios where demand, power, or code is limited, respectively. Compared with existing methods in the literature, the proposed algorithm can reduce the overall system's distortion by 14% to 26%. In the demand-limited case and the code-limited but power-unlimited case, the proposed scheme achieves the optimal solutions. In the power-limited but code-unlimited case, the proposed scheme has a performance very close to a performance upper bound     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.     

支持多业务QoS的多小区资源分配算法

提出了一种基于半静态干扰协调的支持多业务QoS的OFDMA资源分配算法PQSIC。算法按信道质量将用户分为中心和边缘用户,综合考虑业务的QoS要求和边缘用户的信道质量,在特定的频率资源规划方案基础上确定小区中心、边缘用户的可用频率资源,然后将其可用频率资源分别在小区中心和边缘用户中进行分配。仿真结果表明:PQSIC算法能合理分配频率资源,较好地保证多业务系统中用户的QoS。     

CDMA蜂窝网中的无线资源管理

本文对CDMA蜂窝网络中的无线资源管理研究作综述。内容包括功率控制、接纳控制、越区切换和无线分调度等方面，并考虑了多种业务下的服务质量。     

Uplink capacity optimization by power allocation for multimedia CDMA networks with imperfect power control

A closed-form capacity quasi-optimal power allocation scheme is presented for the uplink of multimedia code-division multiple-access (CDMA) systems with randomized received signal-to-interference ratio (SIR) resulted from the errors of power control. The optimality in capacity comes from that this scheme provides class-dependent SIR margins subject to the constraint of differentiated outage requirements. The statistics of signal under imperfect power control is modeled as lognormal random variable. The objective of capacity maximization is formulated as the minimization of total average received powers since the capacity of a CDMA system is interference limited. Under this model, we first derive the necessary conditions that a capacity-optimal power allocation should satisfy. By using conservative bounds, we provide a closed-form approximate solution to this optimization problem. This approximate solution provides nearly the same admissible region for multimedia traffic under imperfect power control as the accurate solution (the optimal one) does. The closed-form quasi-optimal power allocation scheme proposed in this paper is just based on this approximate solution. By numerical example we verify our analysis and show that great capacity gain (e.g., 92% as a maximum in the example) can be achieved by our scheme over its counterpart.