一种改进的认知无线电博弈功控算法

认知无线电(CR:Cognitive Radio)技术是一种能实现频谱有效使用的新技术.本文介绍了认知无线电的工作原理,对认知循环中发送端的功率控制作了重点研究.基于David Goodman的非合作功率控制博弈方法,本文提出了一种只和用户的信干比相关的S型有效函数,它的优点是不考虑用户的无线接入技术的调制方式,因而非常适合认知无线电系统.另外,我们在传统的定价函数中也引入了路径增益的部分.本文论证了在博弈过程中,该带有S型有效函数的效用函数存在纳什均衡且均衡点唯一.最后,通过MATLAB仿真表明了新的效用函数和传统的CDMA系统中的NPG和NPGP的效用函数相比,将带来明显的性能改善,比较并分析了不同参数情况下它的性能表现.     

认知无线网络中一种非合作博弈功率控制算法

针对现有的功率控制算法中存在的干扰问题和功率消耗过大问题,设计出一种新的效用函数,并根据此效用函数提出了一个基于非合作博弈的新的功率控制算法。首先,在效用函数中分别为信干噪比和功率设定了不同的代价因子,并将信道状态概念引入到代价因子里面,使其能够更加合理地控制用户,避免用户过度增加发射功率,同时减小了用户间的干扰;其次,证明了该算法纳什均衡的存在性和唯一性;最后,给出了所提算法的流程图。仿真结果表明,与Nash算法相比,在保证非授权用户服务质量( QoS)前提下,该算法功率消耗明显降低,并且具有较好的抗背景噪声性能;与K-G( Koskie-Gajic)算法相比,该算法保证了所有的用户的信干噪比满足上下限阈值要求,并且提高了系统容量。     

快速Lagrange算法在双速率多用户检测器的功率控制中的应用研究

本文提出了一种快速Lagrange算法,并将它应用于宽带码分多址扩频通信双速率多用户检测器的功率控制中,从而使系统在达到不同的信扰比的条件下,各个用户的发送功率之和最小。本文分析了用该算法对双速率多用户检测器进行最小发送功率控制的基本理论和实际性能,探讨了该算法中相关参数的确定方法。该算法利用平均和反馈技术加快了Lagrange算法的收敛速度,因此有较好的实时性。仿真结果表明与快速随机功率控制算法相比,快速Lagrange功率控制算法可以提高双速率多用户检测器输出信号的平均信扰比,降低信扰比的平均偏差,提高达到信扰比要求的用户数量。     

CDMA系统中基于效用函数的功率控制策略的研究

本文介绍了一种基于效用函数的功率控制的方法,首先介绍了频分多址技术的优势及其固有的缺点。说明了由于多址干扰,使功率控制成为CDMA系统中关键的技术。本文介绍了基于效用函数的功率控制策略和分布式控制算法。最后用Matlab仿真对比。     

神经网络在CDMA移动通信上行链路功率控制中的应用研究

提出了一种神经网络功率控制方案，研究了该方案在码分多址(CDMA)移动通信中实现最小发送功率控制问题。首先导出了最小发送功率控制模型。而后，利用最陡下降方法得到了求解该模型的神经网络的原理框图，并分析了用该网络进行最小发送功率控制的基本理论和实际性能，探讨了该网络相关参数的确定方法。最后用计算机仿真法模拟出该方案的运行性能。仿真结果表明与最小功率分配算法相比，神经网络功率控制方案可以提高基站接收信号的平均信扰比，降低信扰比的平均偏差，提高信扰比达到目标信扰比90％以上的用户数量，从而可以降低用户信号的中断概率、提高信道容量。     

基于认知无线电的WiMAX系统多用户资源分配算法

基于认知无线电(CR)和OFDM的传输特性,提出了一种WiMAX系统多用户资源分配算法.感知用户根据认知到的频谱资源信息,在不对授权用户造成干扰的前提下使用空闲频谱资源.利用注水算法对多个用户请求使用同一子载波进行裁决,在满足传输速率以及QoS要求下,完成子载波、比特和功率分配,使整个系统传输功率最小.仿真结果表明,基于认知无线电的WiMAX系统多用户资源分配算法的传输功率和性能明显优于使用静态算法方案的系统.     

下行时间反转非正交多址接入系统的设计与优化

针对时间反转多址接入系统在用户相关性较大时，用户间干扰严重，导致系统和速率下降问题，提出一种将时间反转多址接入技术与功率域非正交多址接入技术相结合的下行多址系统方案.将相关性较高的用户分为一组，组内用户符号采用非正交叠加传输的方式，不同用户组的符号采用时间反转滤波器进行预处理，实现多用户符号的同时同频传输.给出了一种用户分组算法，进一步在用户最小速率和基站的总发送功率约束下，采用迭代信干噪比注水算法优化用户的发送功率以最大化系统和速率.仿真结果表明，本文方案在配备单根发送天线、预滤波器采用迫零准则设计时高发送功率下的系统和速率比常规的时间反转多址接入方案约高30%；天线数目越多，性能优势越明显.     

5G移动网络中终端直连方式下用户发送功率自适应优化方法

作为对传统移动通信网络的有力补充,终端直连(device to device,D2D)的概念被引入未来5G移动通信网络中.为了解决D2D方式中无基站中转的通信问题及非基站控制用户无序发送所带来的复杂干扰环境及覆盖盲区情况下发送资源的自适应优化分配问题,提出了一种基于博弈理论与模糊逻辑理论的发送功率自适应分配算法,用以充分利用系统的功率与频谱资源,同时降低功率分配对其他用户产生的干扰影响.通过对计算机仿真结果的分析,提出的算法相对于传统的平均功率分配算法及分布式注水算法有一定的性能提高.     

CR系统中基于微分博弈的功率控制算法

该文针对认知无线电系统动态性的特点,将微分博弈理论应用在认知无线电系统的功率控制中,建立了功率控制的非合作微分博弈模型,提出了一种基于微分博弈的分布式非合作功率控制算法。该算法在满足认知用户平均功率门限和QoS需求的基础上,实现了分布式动态功率控制,获得了反馈纳什均衡解析解。仿真结果表明,该算法可有效控制各认知用户的发射功率,增加系统吞吐量,提高系统性能。     

基于归一化效用函数的功率控制算法研究

功率控制技术是认知无线电的关键技术之一,分布式功率控制问题可以转化为非合作博弈问题来解决,结合认知无线电特点,提出一个新的S型效用函数,应用归一化的形式表示,并证明了其纳什均衡解的存在和唯一性.仿真结果表明,该算法不受系统调制方式的限制,且具有较快的收敛速度,在一定程度上兼顾了用户之间的公平性,使用户能公平地共享信道资源.     

Adaptive Modulation and Power Control for throughput enhancement in cognitive radios

To regulate the transmit-power and enhance the total throughput, a novel Transmit Power Control Game （TPCG） algorithm and an adaptive Modulation TPCG （M-TPCG） algorithm which combine bandwidth allocation, adaptive modulation and transmit-power control based on Space Time Block Coding （STBC） OFDM-CDMA system are designed and a cross-layer framework of database sharing is proposed. Simulation results show that the TPCG algorithm can regulate their transmitter powers and enhance the total throughput effectively, M-TPCG algorithm can achieve maximal system throughput. The performance of the cognitive radio system is improved obviously.     

A power-efficient injection-locked class-E power amplifier for wireless sensor network

In this letter, we present an injection-locked Class-E power amplifier (Class-E ILPA) suitable for 2.4-GHz wireless sensor network applications where the maximum transmit-power is typically about 10dBm. In such a low transmit-power application, it is a great challenge to achieve a high transmit efficiency because the driving power and dc power consumption in the previous stage are no more negligible compared with the transmitted signal power. The proposed Class-E ILPA, which is fully integrated in 0.18-/spl mu/m CMOS technology, achieves the power added efficiency of 44.5% while delivering the output power of 11dBm with drain efficiency of 49.3% at 1.2-V supply voltage. The measured locking range reaches 300MHz with the input driving power of -6dBm.     

Video coding for OFDM systems with imperfect CSI: A hybrid digital–analog approach

Performance of an orthogonal frequency division multiplexing (OFDM) system is greatest when the exact channel state information (CSI) is used for transmitter rate control and power allocation. However, in real systems CSI can only be approximately known. Moreover, in video communication, it can be difficult to use any CSI for rate control of a video codec if the channel changes significantly during a group of pictures coded jointly, such as when the receiver is moving. We address this issue through a hybrid digital–analog (HDA) coding system where a standard video codec is used to generate a fixed-rate base layer upon which the analog quantization error is superimposed as a refinement layer. The system adapts to channel variations by proper transmit-power allocation between digital and analog components and across OFDM subcarriers, based on CSI. We present a power allocation scheme for this system which explicitly takes into account the imprecise nature of the available CSI. Experimental results obtained with simulated OFDM channel traces show that proposed scheme is able to achieve a much better quality-vs-reliability trade-off in video transmission, compared to the best known digital-only and analog-only alternatives.     

Improving power efficiency of CSMA wireless networks using multi-user diversity - [transaction letters]

This paper proposes a method that reduces transmit-power consumption of carrier-sense multiple-access (CSMA) networks by utilizing multi-user diversity and power control. Using this method, a terminal sends a packet at a slot if the terminal?s signal-to-noise ratio (SNR) is above the threshold associated with the slot. Since the threshold value decreases as time advances, this method will make the user with the largest SNR access the shared channel; thus, a packet can be transmitted with less transmit power. The analysis under the infinite-user model shows that, as traffic load grows, the expected sum-power of the conventional CSMA network increases whereas that of the proposed method decreases.     

A Novel Low-Complexity Precoding Algorithm for MIMO Cognitive Radio Systems

This paper proposes a novel efficient precoding algorithm to maximize the rate of the cognitive link, where a pair of multiple-input multiple-output cognitive radio users shares the spectrum allocated to multiple primary users as long as the interference power is acceptable. In our method, the precoding vectors are firstly obtained by solving an unconstrained convex problem which is formulated by using the penalty function idea and has a closed-form solution. Then, power is allocated to different precoding vectors to satisfy both the transmit-power constraint and interference-power constraints through interior method. Moreover, an effective set of the penalty weights is presented. Our method has much lower complexity than the optimal solution and similar complexity to other low-complexity methods. Simulation results show that our method significantly outperforms the existing low-complexity methods and has almost the same performance as the optimal solution.     

Power Consumption Analysis of User-Identity Feedback

User-identity feedback was proposed to achieve multi-user diversity while minimizing feedback load. This letter mathematically shows that the transmit-power consumption of the user-identity feedback converges to zero as the number of users increases. Numerical results in a Rayleigh fading channel show that the transmit-power saving is substantial even with small number of users.     

Power Adaptation for Energy Efficient Bi-directional Relaying with Quality-of-Service Requirement and Individual Peak-Power Limit

This paper addresses an optimal power adaptation (PA) problem of a two-time-slot bi-directional relaying network with a half-duplex amplify-and-forward relay. Unlike the existing studies, our goal is to develop effective PA strategies that can dynamically adjust the transmit-power levels of all the terminals to achieve energy efficiency, while satisfying the individual peak-power limit on each terminal and the quality-of-service (QoS) requirement of the network. By using the instantaneous channel state information (ICSI) and the statistical CSI (SCSI) knowledge, respectively, and with the aid of traffic information, the PA problem is analytically solved, leading to the so-called ICSI and SCSI based PA strategies with closed-form PA solutions for individual transmit-powers at the relay and the two end-terminals. Simulation results have verified the correctness of the derived expressions and confirmed the efficiency of our proposed strategies. It is shown that the proposed PA strategies can significantly reduce the total transmit-power of the network with guaranteed network QoS.

     

Channel-adaptive sectored multicarrier packet based systems

Multicarrier packet based multiuser systems with adaptive subcarrier-user allocation and per-user adaptive transmit-power and modulation are considered. The impact of interleaved-multicarrier cell sectoring and channel estimation errors on the performance of such a system is evaluated using computer simulation.     

Joint resource optimization for nonorthogonal multiple access-enhanced scalable video coding multicast in unmanned aerial vehicle-assisted radio-access networks

A joint resource-optimization scheme is investigated for nonorthogonal multiple access (NOMA)-enhanced scalable video coding (SVC) multicast in unmanned aerial vehicle (UAV)-assisted radio-access networks (RANs). This scheme allows a ground base station and UAVs to simultaneously multicast successive video layers in SVC with successive interference cancellation in NOMA. A video quality-maximization problem is formulated as a mixed-integer nonlinear programming problem to determine the UAV deployment and association, RAN spectrum allocation for multicast groups, and UAV transmit power. The optimization problem is decoupled into the UAV deployment–association, spectrum-partition, and UAV transmit-power–control subproblems. A heuristic strategy is designed to determine the UAV deployment and association patterns. An upgraded knapsack algorithm is developed to solve spectrum partition, followed by fast UAV power fine-tuning to further boost the performance. The simulation results confirm that the proposed scheme improves the average peak signal-to-noise ratio, aggregate video-reception rate, and spectrum utilization over various baselines.     

Robust Transmit Power Control for Cognitive Radio

A cognitive radio network is a multiuser system, in which different users compete for limited resources in an opportunistic manner, interacting with each other for access to the available resources. The fact that both users and spectrum holes (i.e., unused spectrum subbands) can come and go makes a cognitive radio network a highly dynamic and challenging wireless environment. Therefore, finding robust resource-allocation algorithms, which are capable of achieving reasonably good solutions fast enough in order to guarantee an acceptable level of performance under worst case interference conditions, is crucial in such environment. The focus of this paper is the transmit-power control in cognitive radio networks, considering a noncooperative framework. Moreover, tools from control theory are used to study both the equilibrium and transient behaviors of the network under dynamically varying conditions.