无线信元反向复用及动态容量调整技术研究

根据ATM无线链路组网需求,提出了适合无线链路反向复用的编码及动态容量调整技术。该技术适用于利用微波、散射和卫星等传输手段进行ATM/MPLS无线机动组网,编码纠错门限为2×10-3,当通信节点无线传输距离增大或信道传输质量变恶劣时,通过动态容量调整技术自动降低信号速率以提高业务传输质量,该项技术特别适合新一代宽带网络。     

Equation Chapter 1 Section 1基于中继的协作频谱感知性能分析及优化

提出了一种基于目标的中继协作频谱感知方案,证明了SU到SR链路上的信道条件对系统性能有较大的影响;鉴于此,提出了一种优化的最佳中继协作频谱感知(optimized BRCSS)方案,通过联合考虑目标SU到SR链路上的信道条件和 SR 到 FC 链路上的信道条件选择最佳认知中继;最后,从更实际的应用场景考虑,为了节约系统开销,进一步提出了一种自适应的最佳中继协作频谱感知方案（A-BRCSS）,即 SU 根据其信道条件,自适应地选择是否需要认知中继的协作传输。分析和仿真结果均表明,相比传统最佳中继协作频谱感知方案, Optimized BRCSS方案可以实现更高的感知性能;所提A-BRCSS方案可以实现几乎最佳的感知性能。     

基于几何的高速铁路协作MIMO信道建模

协作MIMO技术通过协作发射或协作接收的方式可以将干扰信号转变为有用信号,在高铁无线通信中引入该技术,能解决回波信道响应和提高系统容量。为了掌握协作MIMO技术在高铁场景中的信道特性,该文基于几何随机散射理论,提出一个高速铁路协作MIMO信道模型,简单调整该模型中的几个关键参数即可适用于高速铁路的多种场景。基于该模型计算信道冲激响应,推导多链路空间相关函数,进行数值计算、仿真分析和实测数据验证。仿真结果显示,直射分量越强,散射分量的角度扩展越小,多链路的空间相关性越强。散射次数越少,散射分量空间相关性越强。使用北京-天津高铁段LTE专网的实测数据验证理论模型的正确性。这些结论有助于认知协作MIMO信道和进行有效的测量活动。     

高铁场景多系统共建的无线覆盖方案

分析高铁覆盖特点,讨论LTE时代高铁场景多运营商无线信号覆盖的困难点,针对多系统间干扰、小区重叠区域设置、隧道内/外的链路预算模型等影响网络建设的主要问题,提出基于LTE技术的高铁无线覆盖解决方案及网络部署策略。结合合福高铁福建段三家运营商的公网建设情况,将本覆盖方案应用在工程中,通过拉网测试验证该方案的有效性,为后续其他高速铁路的无线网络覆盖提供参考方案。     

OFDM-ROF下行链路的性能研究

OFDM技术与ROF技术结合为实现低成本、高速数据传输的移动网络提供了可能,但光纤链路的非线性以及无线信道的多径衰落降低了系统性能。在建立ROF下行链路的传输函数模型基础上,分析ROF下行链路对OFDM信号性能的影响。传输模型包括激光器,光纤链路以及无线信道。分析在不同光调制指数、光纤长度及无线多径信道下接收信号的误差矢量、三阶非线性失真和互调失真。仿真结果显示：随着调制指数、光纤长度的增加,以及无线信道的多径衰落使得接收信号性能下降。此分析为OFDM-ROF下行链路的线性化以及无线信道均衡方案选择提供了理论基础。     

全双工环境反向散射通信网络的绿色物联网

基于物联网的瓶颈问题,对将作为未来物联网核心技术的反向散射技术进行分析和研究。首先研究传统的反向散射技术在射频识别系统中的应用,并进一步探讨存在的问题与不足;随后基于物联网射频识别技术的局限性及在新型反向散射技术,描叙一种全双工环境反向通信网络系统模型。该模型通过一种环境反向散射通信网络访问方式,即在接入全双工接入点的同时向其用户发送下行正交频分复用信号,并以时分多址接收从多个反向散射设备反向散射的上行链路信号。环境反向散射通信通过环境中射频载波传输信息的反向散射设备无线供电,更加环保和节能,满足未来物联网对能源、成本和复杂性的严格限制。     

全光自由空间光通信中继协作方案的研究

提出了一种结合副载波强度调制直接探测技术和全光放大转发中继的自由空间光通信(FSO)系统的基本结构,考虑背景噪声和放大自发辐射噪声对系统性能的影响,建立了Gamma-Gamma湍流模型下的全光通信系统模型。提出了两种中继协作方案,即全活跃中继方案与选择中继方案,基于相应的方案给出功率分配方式,仿真对比了中继辅助传输链路与直传链路的中断概率,以及在不同信道参数及中继数下采用这两种方案的系统中断概率。结果表明,中继传输能够明显改善链路的性能,选择中继方案优于全活跃中继方案。     

菱形中继网络中基于叠加训练的信道估计技术研究

针对放大转发(Amplify-and-Forward, AF)模式下的菱形中继网络,为了高效获取级联和单跳链路信道状态信息(Channel State Information, CSI),本文提出基于叠加训练的信道估计方案,以消除多址接入干扰和训练间互干扰为目标,进行最优的多训练序列设计。新方案将中继训练叠加到源训练序列上,通过对中继识别符号以及中继训练组进行联合优化设计,设计了一种基于频域循环移位的正交扩展序列组生成算法。为了消除非高斯复合噪声对单跳信道估计造成的严重干扰,提出了一种中继噪声消除算法。通过两路中继链路获取的信息副本,能够在端节点实现分集合并,有效提高符号检测性能。仿真实验对比了同类型的信道估计方案,分析验证了方案的有效性。      

基于DF中继协作的车联网安全传输性能研究

5G时代的到来加快了以车路协同为核心的车联网技术的发展脚步。高效，可靠，安全的通信质量将是实现智能交通管理系统，完善智慧出行的基本要求。因此，针对存在信息窃取者的车联网中继协作传输场景，利用机会式中继选择策略与最大比合并技术设计了直接传输链路与多跳中继转发链路共存的安全传输方案，旨在提高信息传输的可靠性及安全性。同时，在获得信道概率密度函数及累积分布函数的基础上，利用全概率公式等方法推导出基于DF(Decode-Forward)中继协作传输的车联网系统安全中断概率的闭合表达式，其中涉及的信息传输信道均服从Nakagami-m分布，提高了理论推导的难度。最终的仿真实验证实了理论推导的准确性及本方案的可行性。      

面向6G高铁移动场景的R10编码传输方案

6G时代越来越多的智能应用将在高铁中部署,需要高铁移动网络提供可靠和高效的传输服务。然而,受高速移动影响,车-地通信链路呈现快时变特性,采用传统的信道估计、反馈机制难以有效跟踪链路的快速时变,因此高铁移动网络亟需高效的前向纠错无反馈传输方案。由于R10编码兼顾了喷泉码和系统码的优点,将其引入高铁移动场景,提出了一种基于R10编码的高速移动车-地编码传输方案。采用该方案,发送端编码过程加入结构化冗余信息结合特定编码规则生成并发送任意数量编码符号,而接收端只需要收集一定数量编码符号结合结构化冗余信息即可更精准地恢复原数据,因此可实现更低的误码率。仿真实验表明,所提方案与传统无需反馈编码传输方案相比误比特率大大降低。以Turbo码为例,误比特率降低了约13%。     

一种适用多种空时编码方案的MIMO自编码器通信系统

为提升现有端到端通信系统的适应性与信道估计的准确性,提出了一种适用于多种空时编码方案的多输入多输出(Multiple-Input Multiple-Output,MIMO)自编码器通信系统.该系统将基于卷积神经网络的自编码器引入到MIMO系统中,并结合信道估计网络实现信道均衡,通过端到端的学习方式实现各种空时编码方案下...     

Pilot-aided chip-interleaved DS-CDMA transmission over time-varying channels

Time-varying multipath fading associated with the wireless link limits the capacity of a wireless system. In order to adapt to this adverse radio environment efficiently, we investigate the use of a pilot-aided fade-resistant transmission scheme for the uplink of a chip-interleaved code-division multiple-access (CDMA) system. We analyze the tradeoff between the number of diversity branches and the channel estimation error. We derive the optimum ratio of pilot signal energy to information signal energy. Our numerical study indicates that the proposed system is capable of outperforming the conventional CDMA system depending on the transmitter energy and channel condition.     

Sub‐Nyquist rate ADC sampling‐based compressive channel estimation

To realize high‐speed communication, broadband transmission has become an indispensable technique in the next‐generation wireless communication systems. Broadband channel is often characterized by the sparse multipath channel model, and significant taps are widely separated in time, and thereby, a large delay spread exists. Accurate channel state information is required for coherent detection. Traditionally, accurate channel estimation can be achieved by sampling the received signal with large delay spread by analog‐to‐digital converter (ADC) at Nyquist rate and then estimate all of channel taps. However, as the transmission bandwidth increases, the demands of the Nyquist sampling rate already exceed the capabilities of current ADC. In addition, the high‐speed ADC is very expensive for ordinary wireless communication. In this paper, we present a novel receiver, which utilizes a sub‐Nyquist ADC that samples at much lower rate than the Nyquist one. On the basis of the sampling scheme, we propose a compressive channel estimation method using Dantzig selector algorithm. By comparing with the traditional least square channel estimation, our proposed method not only achieves robust channel estimation but also reduces the cost because low‐speed ADC is much cheaper than high‐speed one. Computer simulations confirm the effectiveness of our proposed method. Copyright © 2013 John Wiley & Sons, Ltd.     

基于MP-WFRFT的物理层保密增强安全方案

针对战场无线网络全域开放性、广播特性以及实时移动性等特征带来的通信系统安全隐患,为保障战场网络内消息的安全有效传输,本文通过对物理层信号的安全分析研究,结合变换域通信手段与经典加密方法,在信道共享密钥的基础上提出了一种基于MP-WFRFT的保密增强安全方案。通过建立物理层安全加密模型,给出了信道探测与共享密钥生成方法,在扰乱星座方案加持下利用MP-WFRFT多加密参数的混合载波调制对传输信号星座进行扰乱处理。仿真分析表明,本方案能够提升战场无线网络内信号的星座熵,并且在系统误码率性能上相较以往方案存在大幅度提升,为战场无线网络整体性能提升提供了一种新型方案。      

310 GHz太赫兹通信系统设计

太赫兹波具有传输速率高、容量大、方向性好、抗干扰能力强等特点,由于大气损耗大和大功率源的缺乏,较适用于短距离无线通信。基于300 GHz频段的优良特性,设计了一种310 GHz太赫兹无线通信系统。通信链路基于美国亚毫米波与太赫兹产品制造公司(VDI)的谐波混频和超外差收发,系统主要由倍频器、功率放大器、滤波器和VDI次谐波混频器构成。根据链路预算搭建实际通信系统,仿真和实验结果证明：随着通信速率的升高,解调信号的失真逐渐增加。通信距离1 m条件下,系统能实现10 Gbps无误码传输,当速率达到11 Gbps时,误码率为5×10-6。     

Performance Evaluation of Short Range Underwater Optical Wireless Communications for Different Ocean Water Types

This paper has presented our interesting in wireless underwater communications for different ocean water types. Recent interest in ocean exploration has brought about a desire for developing wireless communication techniques in this challenging environment. Due to its high attenuation in water, a radio frequency (RF) carrier is not the optimum choice. Acoustic techniques have made tremendous progress in establishing wireless underwater links, but they are ultimately limited in bandwidth. In traditional communication systems, constructing a link budget is often relatively straight forward. In the case of underwater optical systems the variations in the optical properties of ocean water lead to interesting problems when considering the feasibility and reliability of underwater optical links. The main focus of this paper is to construct an underwater link budget which includes the effects of scattering and absorption of realistic ocean water. As well as we have developed the underwater optical wireless communication systems to have shorter ranges, that can provide higher bandwidth (up to several hundred Mbit/s) communications by the assistant of exciting high brightness blue LED sources, and laser diodes suggest that high speed optical links can be viable for short range application. The received signal power, signal to noise ratio, bit error rate, transmitted signal bandwidth, and transmission bit rates are the major interesting parameters for different ocean water mediums as a criteria of the best signal transmission characteristics of short wireless optical communications over wide range of the affecting parameters.     

A novel self-pilot-based transmit-receive architecture for multipath-impaired UWB systems

In the last few years, ultra-wideband (UWB) systems became an appealing technology for wireless communication applications. Unfortunately, when the transmission channel is affected by intersymbol interference (ISI), system performance of UWB systems equipped with receivers based on conventional matched filters presents error-floor phenomena. Aimed by these considerations, in this letter, we present a novel transmit-receive scheme allowing blind channel estimation and minimum mean-square error linear channel equalization. Essentially, the proposed scheme exploits a very short duration of the UWB pulse for achieving reliable blind deconvolution of the received signal. A nice feature of the resulting system is that blind deconvolution of the received signal is achieved without power and throughput losses. Simulation results support the effectiveness of the proposed scheme, and show that it is able to gain about 8 dB over current UWB receivers based on matched filtering on several test channels impaired by ISI.     

Overview on Technical Issues for Future Mobile Network and a Proposal of DLC Scheme in Wireless Link

This paper gives an overview on technical issues for future mobile networks. the QoS control for multimedia services, security function, expansion of network capacity, expansion of address space, multicast function, radio link quality and mobility control of terminals are taken up as technical issues.Then, a novel DLC scheme in wireless link named EREP-ARQ (Estimation and Report of Error Pattern ARQ) which can reduce the retransmission ratio is proposed. In this scheme, error pattern generated in the radio link is estimated at the receiver side and the estimated error pattern is returned to the transmission side. If the estimation is correct, no retransmission is needed. Compared to conventional SR-ARQ, throughput can be improved by17% and Cell Loss Ratio (or Packet Loss Rate) can be reduced to less than 1/10 by the proposed EREP-ARQ.     

非对称协作通信中的时变功率分配算法

针对反射、散射影响下的非对称无线协作通信网络,提出了一种时变功率分配(Time Variant Power Allocation, TVPA)算法。根据无线协作网络中,各节点之间信道条件实时变化且不对称的特点,在信号传输过程中对信源节点和中继节点的发送信号功率进行优化分配。借助信道编码定理,将系统错误概率最小的非凸优化问题转化为最大化系统容量的凸优化问题来解。与固定功率分配(Fixed Power Allocation, FXPA)算法和平均功率分配(Average Power Allocation, AVPA)算法相比,该算法能充分利用无线信道的时变特性,重新分配功率以降低系统错误概率。在多种网络模型中的仿真结果表明,准静态瑞利衰落信道下,相比于FXPA算法,TVPA算法可获得多达5.5dB的比特错误概率性能增益。随着网络质量的进一步改善,该性能优势也逐步增大。      

无线光通信差错控制系统的时间参数特性

在无线光通信系统中,光强闪烁和大气衰减等因素将使通信系统产生长突发误码,结合Turbo码,建议并分析了两种差错控制方案中时间参数的特性.对于Turbo码 信道交织的差错控制方案,仿真分析了不同信道交织深度下的无线光通信系统性能,给出了特性曲线.对于Turbo码 反馈重发(ARQ)的方案,仿真结果表明反馈环路延迟时间的变化不影响系统的平均吞吐量,但是将影响平均数据传输延迟和重发次数的概率分布.