基于功率控制CDMA容量优化的应用

为了克服CDMA系统的远近效应和边缘效应,解决CDMA网络容量受限的问题,采用了功率控制技术,对前向链路减小基站发射功率,对反向链路调整移动台发射功率,降低系统内的干扰水平,满足用户QoS要求,有效提高CDMA系统容量。理论阐述了功率控制技术与CDMA系统容量的关系,从系统载扰比分析入手验证了功率控制对CDMA系统容量的影响,得到了基于功率控制技术两种容量优化方法即远近控制和C/I控制。实际案例仿真结果表明,通过优化功率控制参数的方法能够有效地提升CDMA系统的容量,促使CDMA网络软容量达到最佳,为CDMA网络优化人员提供可以借鉴的思路和方法。     

异构网络中基于用户划分的资源分配与功率控制方案

部署异构网络是提高移动通信系统容量至关重要的举措。然而宏基站的高发射功率会使得微蜂窝边缘用户受到严重的干扰;同时,微蜂窝周围的宏蜂窝用户由于靠近微基站将同样受到其所造成的干扰,因此这些用户应该受到保护。通过研究异构网络下行传输中的资源分配与功率控制策略,提出了一种基于用户划分的资源分配与功率控制方案。首先根据用户的信干噪比对用户进行分类,同时为受干扰严重的边缘用户划分保护频带。此外,通过动态地调整每个基站在保护频带上的传输功率,在不过度牺牲系统性能情况下减轻边缘用户的干扰。仿真结果表明,与传统方案相比,该方案能够有效抑制宏蜂窝和微蜂窝边缘用户的干扰并提高整个系统的吞吐量。     

超密集网络中基于Stackelberg博弈的非统一定价功率控制

针对超密集网小区同频部署中产生的区间干扰问题,提出基于Stackelberg博弈的非统一定价功率控制方案。首先,建立基于Stackelberg博弈的非统一定价功率控制模型,并通过该模型求解出基于价格的最优发射功率,此发射功率是关于干扰价格的函数;接着通过引入拉格朗日函数求解出相应基站的最优干扰价格,由控制器把干扰价格发送给相应的基站,并由基站调整自己的发射功率值去减弱对当前用户的干扰。仿真结果表明,与基于Stackelberg博弈的统一定价功率控制方案相比,所提方案在系统平均中断概率上平均下降了3个百分点。与基于基站权重的功率控制方案相比,在基站数量低于105时,所提方案在平均中断概率平均上上升了1.4个百分点;而当基站数超过105时,所提方案在平均中断概率上平均下降了1.6个百分点。此外,与这两个方案相比,所提方案在系统平均吞吐量上分别提升了12个百分点和10.5个百分点;在系统平均频谱效率上分别提升了9个百分点和8.5个百分点;在系统平均功率效率上分别提升了13个百分点和12个百分点。实验结果表明所提方案能够在部署更多基站情况下更好地提高蜂窝系统的性能。     

CDMA移动通信中外环功率控制研究

CDMA是一个干扰受限系统,反向链路功率控制对于克服“远近效应”和增加系统容量是非常重要的。本文从减小用户发射功率及误帧率FER波动的目标出发,提出了一种外环功率控制的算法。仿真结果表明,采用该算法的系统具有可行性,有着良好的抗干扰能力。     

LTE家庭基站部署中的下行功率控制

家庭基站在LTE中的密集部署,重叠覆盖会在家庭基站间造成较强的干扰。针对家庭基站的下行干扰,提出了一种基于路损的功率控制算法。该算法以下属用户的路损和相邻基站的非下属用户最小路损作为设定基站初始发射功率的依据,用户计算各自的信干噪比（SINR）,并将信干噪比映射成信道质量指示（CQI）发送给家庭基站,各基站根据反馈信息调整自身发射功率,充分考虑到了自身发射功率不足和外界干扰两种情况。仿真结果表明,该算法很好地控制了用户的SINR,同时有效提高了家庭基站用户的吞吐量。     

大规模MIMO系统中基于用户位置的导频分配

大规模多输入多输出（multiple input multiple output,MIMO）系统中因导频复用而存在的导频污染问题,成为其性能提高的瓶颈。针对此问题,提出一种基于用户位置的导频分配方案。该方案通过上行功率控制方法保证不同用户到各自小区基站的信号功率相同,并在功率控制情况下,根据干扰用户到本小区基站距离与到目标小区基站距离的比值来定义干扰用户对目标用户的导频污染强度,并给用户间导频污染强度较小的两个不同小区用户分配相同的导频。仿真结果表明,所提方案能够有效提高系统容量,减小用户间性能差距,较好地降低了用户间的导频污染。     

混合蜂窝对称干扰拓扑下功率域动态干扰中和技术研究

为有效应对异构蜂窝网络因区域重叠所造成的干扰,在兼顾通信路径损耗和基站发射功率差异的基础上,提出一种用于实现动态干扰中和的对称干扰拓扑模型。在相互干扰的通信信道中,基站通过发射中和信号的方式来消除用户所受到的部分干扰。在此基础上,对用户所在位置的干扰中和比例进行自适应调整,控制并利用由中和信号所造成的负面影响,为基站设定最佳功率分配方案,平衡期望数据传输发射功率和中和功率开销之间的关系,进而实现最大化的系统频谱效率。     

基于ABS的干扰协调方案研究

异构网通过运用不同功率的基站同频部署,扩大了网络覆盖率及系统容量。但同时这种多层结构也带来了小区间干扰问题。ABS是一种时域上的小区间干扰协调技术,解决了下行传输中高功率宏基站和低功率小基站共享频域资源时的干扰问题,但该技术的缺点是降低了宏基站的用户容量。文中研究了一种从频域、时域、功率三个维度联合进行干扰协调的新型ABS解决方案。仿真结果证明该方案可以显著增加宏基站用户的吞吐量,同时不对小基站产生过多干扰。     

认知网络中基于博弈论的联合功率控制与速率分配算法

针对认知无线网络上行链路中的资源分配问题,提出了一种适应于多小区认知无线网络的基于功率控制与速率分配的博弈算法。为了更加合理地控制用户的功率和速率,减小各次用户间的干扰,首先,在效用函数中分别给功率和速率设置了不同的代价因子,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。其次,从理论上证明了该算法纳什均衡的存在性、唯一性以及算法的收敛性。最后,为了解决发射功率和传输速率的最优化问题,给出了联合功率控制和速率分配的迭代更新算法流程图。理论分析及仿真结果表明,与同类博弈算法相比,在保证通信质量的前提下,所提算法可以使得用户以较小的发射功率获得较大的传输速率和较高的信干噪比（SINR）,并且减小了用户间的干扰,提高了次用户系统容量。     

CDMA系统中自动功率控制对系统容量的影响

CDMA系统的容量主要受限于系统内移动台的相互干扰,所以如果每个移动台的信号到达基站时都达到最小所需的信干比,系统容量将会达到最大值。在CDMA蜂窝系统中,为了解决远近效应的问题,同时避免对其他用户过大的干扰,必须采用严格的自动功率控制。功率控制的目的就是既维持高质量通信。又不对同一频率的其它用户产生不应有的多址干扰。功率控制的目的是控制每个用户的发射功率,而使得基站接收收到的每个用户的功率接近,从而克服远近效应。     

Device-to-device resource allocation in LTE-advanced networks by hybrid particle swarm optimization and genetic algorithm

D2D (Device-to-Device) communication is one of the promising technologies in the LTE (Long Term Evolution)-Advanced communication network. From system perspective, this technology can increase frequency efficiency of the whole macro cell. From user perspective, however, a D2D pair which shares the same frequency resource of CUE (Cellular User Equipment) can cause interference with the CUE in the downlink. Thus, reducing interference for the cellular users and allocating frequency resource for the D2D pairs are important in D2D communication. In this paper, two resource allocation schemes which are based on PSO (Particle Swarm Optimization) and hybrid PSO-GA (Genetic Algorithm) are proposed to maximize the system throughput by allowing up to two D2D pairs to share the same frequency resource with one CUE. Moreover, a scheme has been considered to mitigate the interference caused to CUEs. The simulation results show that service of CUEs and system performance can be effectively guaranteed by using the proposed schemes.     

TD-SCDMA下行链路对WCDMA上行链路干扰分析

针对TD-SCDMA下行链路对WCDMA上行链路间干扰产生原理进行研究,建立基于Monte Carlo仿真方法的仿真模型,并将自适应变步长功率算法应用于仿真中。仿真比较自适应变步长算法和传统的固定步长算法,并将改进后的功率控制算法应用于1920MHz语音业务的TD-SCDMA下行链路对WCDMA上行链路干扰仿真中。实验结果表明,系统总发射功率一定时,自适应变步长功率控制算法取得较高的信干比,可减小系统干扰;并得出不同参数设置对TD-SCDMA与WCDMA系统共站时的影响,给出两系统共站时ACIR建议值。为异系统混合组网及网络优化提供一定的参考。     

WCDMA系统功率控制研究

文章首先从干扰因素上得出WCDMA通信技术进行功率控制的必要性,然后介绍了WCDMA上行功率控制和下行功率控制原理,为实际应用中改善系统功率控制,提高系统的容量提供了参考依据。     

多速率CDMA系统下行波束成形的联合多变量优化

下行波束成形能用来限制由于高速率数据用户引起的干扰，也能改善系统性能。另一方面，功率控制、数据速度分配也是改善无线多媒体通信频谱利用率的两种基本技术。在文章里，阐述了DS—CDMA系统中给定系统吞吐量和软的目标SIR门限值条件下，下行波束成形权值和数据速率的优化问题。基于上面的内容，给出了一种改进的IVPW算法，可以将其应用于未来的无线通信系统，为所有用户提供稳定的最大吞吐量。     

基于可见光色分双工的井下定位系统收发机

现有的井下无线定位系统收发机通信主要采用无线电波,由于井下巷道狭小、岩石成分复杂等因素,无线电波的通信距离、通信质量都会受到影响。针对以上问题,设计了基于可见光色分双工的井下定位系统收发机。该收发机采用LED的高速闪烁携带信息,并用光电二极管接收光信号,实现了无线可见光通信。收发机通信的上下行信道采用色分双工的方式,将2个方向上的信号分别调制在2个相互分离的不同颜色的可见光信道上,以实现数据的接收和发送。试验结果表明,该收发机功耗小,抗电磁干扰性能好,接收稳定,并兼有照明作用。     

DS-CDMA downlink systems with fading channel employing the generalized receiver

In this paper, we investigate a generalized receiver (GR) constructed on the basis of the generalized approach to signal processing (GASP) in noise employing by direct-sequence code-division multiple access (DS-CDMA) downlink wireless communication system with multipath fading. Transmitted signaling technique is based on using the orthogonal unified complex Hadamard transform spreading sequences. The use of GR allows us to maintain the orthogonality between users and reduce the multipath fading effect and interference from other users. A general multipath-fading model is assumed. Bit-error rate (BER) performance of system is evaluated by means of the signal-to-interference-plus-noise ratio (SINR) at the output of GR employed by DS-CDMA downlink wireless communication system. Using the orthogonal unified complex Hadamard transform spreading sequences as the transmitted signaling technique, we obtain that SINR at the GR output is independent of the phase offsets between different paths. If the Walsh–Hadamard (WH) spreading sequences are used as the transmitted signaling technique, the SINR at the output of GR employed by the same system is a function of squared cosine of path phase offsets. As a result, the BER performance of the last DS-CDMA downlink wireless communication system is worse in comparison with that of the first system. Comparative analysis between the BER performance of DS-CDMA downlink wireless communication systems employing both the GR and the Rake receiver, which consists of a bank of correlation receivers, with each individual receiver correlating with a different arriving multipath component, shows us a superiority of the first system over the second one both at high and low SINRs.     

基于聚合等级的5G通信下行信道传输控制系统设计

为提高5G通信下行信道的传输稳定性,提升传输控制系统存在的控制效果,设计并开发了基于聚合等级的5G通信下行信道传输控制系统。改装DSP协处理器、通信数据采集器以及信道传输控制器,完成硬件系统的优化。根据信道的空间结构和工作原理,构建通信下行信道模型,判定通信下行信道实时状态。在该模型下,采集通信下行信道的实时传输数据,根据信道的聚合等级,分配信道传输资源。最终从信道增强、发送/接收端、传输干扰、传输速度等方面,实现系统的传输控制功能。通过系统测试实验得出结论,设计系统的传输速率控制误差、信道传输丢包量和信道拥塞概率均有所降低,即设计系统在传输控制功能方面更具优势。     

Joint optimization of communication rates and linear systems

We consider a linear control system in which several signals are transmitted over communication channels with bit rate limitations. With the coding and medium access schemes of the communication system fixed, the achievable bit rates are determined by the allocation of communications resources such as transmit powers and bandwidths, to different communication channels. We model the effect of bit rate limited communication channels by uniform quantization and the quantization errors are modeled by additive white noises whose variances depend on the achievable bit rates. We optimize the stationary performance of the linear system by jointly allocating resources in the communication system and tuning parameters of the controller.     

Enhanced uplink non-orthogonal multiple access for 5G and beyond systems

Uplink non-orthogonal multiple access (NOMA) is a promising technique to meet the requirements of the fifth generation (5G) and beyond systems. Various NOMA schemes have been proposed in both academia and industry. However, most existing schemes assume equal average received power, which limits the performance. We propose three enhancements of uplink NOMA to achieve the requirements of massive connectivity and high reliability in 5G, where unequal average received power is exploited as part of the multiple access signature. First, the optimal sequences targeting to generalized Welch-bound equality (GWBE) are obtained for unequal average received power. Then user grouping with multi-level received powers is proposed for better successive interference cancellation (SIC) at the receiver. Finally, sequence grouping based on the cross-correlation properties of sequences is proposed to reduce inter- and intra-group interference. Simulation results show that by incorporating multi-level received powers and sequence grouping into existing NOMA schemes, for an NOMA system with 400% overloading and fixed signature allocation, 3 dB and 10 dB signal-to-noise ratio (SNR) gains at 0.1 block error rate (BLER) target can be achieved compared with existing NOMA schemes and orthogonal multiple access (OMA), respectively. Besides, 0.01 BLER target can be achieved while an error floor exists in existing NOMA schemes. Under random sequence selection, collision probability is reduced by multi-level powers. In addition, GWBE sequences achieve lower BLER than existing sequences and the gain is large especially for low BLER requirements. This shows that the proposed scheme can support larger connectivity and higher reliability.