全双工窃听者主动干扰的协作NOMA网络性能分析

研究了瑞利衰落信道下协作非正交多址系统的安全性能。通信过程由一个时隙构成,源节点向中继广播叠加信号,全双工中继使用串行干扰消除技术解码信号协助用户通信。假设存在潜在全双工主动窃听者,窃听者能够从中继处截获信息并同时向用户发送人工噪声进行干扰。基于上述假设,在高信噪比条件下,推导了安全中断概率的近似表达式,分析了各节点传输信噪比与功率分配因子对系统中断概率的影响,分析结果与蒙特卡洛仿真结果吻合。     

Secrecy Outage Performance Analysis of DF Cognitive Relay Network With Co-channel Interference

Wireless Personal Communications - In this paper, we investigate the secrecy outage performance of the decode-and-forward cognitive relay network with the existence of the co-channel interference,...     

Outage Analysis of OFDM‐Based Cognitive AF Relay Network in the Presence of Narrowband Interference

Orthogonal frequency‐division multiplexing (OFDM) is one of the most widely used technologies in current wireless communication systems and standards. Cognitive radio (CR) provides a robust solution to the problem of spectrum congestion as it offers opportunistic usage of frequency bands that are not occupied by primary users. Due to the underlying sensing, spectrum shaping, scaling, and interoperable capabilities of OFDM, it has been adapted as a best transmission technology for CR wireless systems. However, the performance of an OFDM‐based CR wireless system is affected by the existence of narrowband interference (NBI) from other users. Further, due to carrier frequency offset in NBI sources, NBI energy may spread over all subcarriers of an OFDM signal. In this paper, a fixed Amplify‐and‐Forward (AF) relay that operates at a frequency band that is different from that of direct mode is introduced to suppress the effect of NBI. Analytical expressions are derived for outage probability in direct, AF‐relay, and incremental relaying modes. The outage performance of the proposed AF relay–based CR network is proven to be better than that of direct mode.     

非理想干扰删除下全双工中继NOMA系统的物理层安全性能研究

全双工协作中继转发信号时存在的自干扰现象会降低系统性能.本文考虑存在窃听者的下行非理想自干扰全双工协作中继非正交多址接入（NFCR-E-NOMA,Non-ideal Full Duplex Cooperative Relay in Non-Orthogonal Multiple Access system with Eavesdropper）系统,分别从系统中断概率和系统截获概率的角度分析了全双工协作中继的自干扰因素对于NFCR-E-NOMA系统安全中断性能的影响;推导了系统中断概率和截获概率的闭合表达式.仿真结果表明,全双工中继转发的自干扰因素对系统性能的影响较大,在NFCR-E-NOMA系统中,存在优化的中继转发功率,且在不同的基站发射功率和中继转发功率条件下,功率分配比对系统性能的影响也不同,在实际主链路信道条件允许的情况下,可通过设置较高的数据传输速率来抑制窃听者的截获概率.     

空时Rake MMSE合并结构的窄带干扰抑制性能分析

对多径衰落信道条件下空时rakeMMSE合并结构的窄带干扰抑制性能进行了分析,结果表明相比其它空时rake合并结构,MMSE合并结构具有最优的抑制窄带干扰和对抗信道多径衰落的性能,它受干扰功率的影响较小,而且该种合并结构仅需较少的接收天线即能获得较好的性能。     

Analysis of the Narrowband Interference Effect on OFDM Timing Synchronization

In OFDM systems, the symbol timing synchronization is needed to find an estimate of where the symbol starts. The most popular of the pilot-aided timing estimators is the one proposed by Schmidl and Cox (S&C) ["Robust Frequency and Timing Synchronization for OFDM," IEEE Transactions on Communications, vol. 45, no. 12, pp. 1613-1621, Dec. 1997]. Generally, the proper action of the timing estimator may be strongly affected by the presence of disturbances, like narrowband interference (NBI) signals. This paper investigates the effect of NBI signals, which may arise in the OFDM band as the spectrum becomes more crowded, on the timing synchronization for OFDM systems. The performance of the S&C symbol timing synchronizer is evaluated in an analytical way in the presence of narrowband interferers. Also, the probabilities of both missing and false detection of a training sequence are addressed. Further, simulations have been carried out to verify the validity of the approximations in the analysis.     

不同频率位置的窄带干扰对DSSS通信性能的影响分析

衡量窄带干扰抑制算法性能高低的一个主要标准是评估干扰处于最恶劣频率位置时的干扰输出平均功率的大小。在扩频序列周期很长且严格平衡的理想条件下,最恶劣干扰的频率位置为DSSS信号载波频率。基于典型的m序列DSSS系统,分析了处在不同频率位置的窄带干扰对DSSS系统的影响,所得结果与理想条件有所不同,这对于扩频系统的设计与应用具有指导意义。     

多用户调度在中继网路中的安全性能分析

无线通信系统中,多用户调度能够有效提高系统频谱的利用效率和吞吐量,从无线通信的物理层安全角度出发,分析了多用户调度在无线通信网络中安全性能,考虑了一种最坏通信场景,即窃听者不但从普通用户而且也从中继节点来窃听被传送的信息,在此基础上提出了一种有效的用户调度算法并得到理论表达式,最后通过仿真实验来分析安全中断概率和信息传输速度以及传输能量的关系,仿真结果表明:该理论表达式的正确性即理论表达式与蒙特卡罗仿真一致;改进的调度方法相对传统的多用户轮询调度方式有显著的优点,降低了通信系统的安全中断概率,有效提高了系统的通信安全。     

Performance Analysis on Two-Way Relay System with Co-Channel Interference

In this paper, we investigate the performance of two-way relay system with co-channel interference in a Rayleigh fading environment. Due to the mathematical intractability of original expression of signal-to-interference and noise ratio (SINR) induced by the bi-directional forwarding, a couple of effective bounds are derived for important performance metrics such as outage probability and average bit error rate of modulation, with application of diverse physical layer network coding (PNC) schemes of two time slot (2TS) and three time slot (3TS). Some asymptotic solutions are also proposed to intuitively exhibit the trends of performance in high SINR regime. We demonstrate that the performance bounds have practical meaning corresponding to different forwarding capability of the relay. Numeric simulations validate our analysis by showing that the theoretic bounds match well with simulation results. Additionally, the effect of distance between relay and sources is discussed in our interference scenario, as well as the impact of relay’s power allocation factor in 3TS PNC scheme.     

基于自能量回收的全双工用户协作NOMA系统性能分析

自干扰的存在是全双工(Full Duplex,FD)用户协作中继系统中的不利因素,本文研究了基于自能量回收(Self-Energy Recycling,SER)的FD用户协作非正交多址(Non-Orthogonal Multiple Access,NOMA)中继系统,在FD用户中继处考虑了不同的转发协议以及同时的信息和...     

Performance of an Ultra-Wideband Communication System in the Presence of Narrowband BPSK- and QPSK-Modulated OFDM Interference

An analysis is derived for calculating the bit-error probability of an ultra-wideband (UWB) communication system operating with binary phase-shift keying and quaternary phase-shift keying narrowband interference in additive white Gaussian noise. The analytical expressions are valid when phase transitions of the interfering symbols can be ignored. The accuracy of the Gaussian approximation is assessed, and several modulation schemes proposed for UWB communication are evaluated in terms of capability of interference suppression.     

Transmit Antenna Selection with Optimum Combining for Aggregate Interference in Cognitive Underlay Radio Network

Transmit antenna selection (TAS) is most popular technique in underlay cognitive radio (CR) networks as they increase the capacity of secondary users with less hardware requirements. In this paper, a new scenario of CR ad-hoc network topology is proposed in which apart from primary users, there are multiple number of secondary users which are assumed to be distributed as homogeneous spatial Poisson point process (PPP) and are trying to use the primary spectrum in underlay mode. These multiple secondary transmitters generate the aggregate interference and can degrade the performance of secondary receiver. Here this aggregate interference is estimated and its impact on performance of secondary receiver under unconstrained mode of operation is presented. Further, to enhance the performance of secondary receivers in this scenario, single TAS technique based on maximizing the received signal to interference noise ratio by using optimum combining (OC) method is proposed. Furthermore, in this work the design of end to end Simulink based environment for secondary trans–receiver system with advancements in channel design and estimation is proposed. The bit error rate (BER) analysis is presented and verified for image data for single TAS-OC technique for unconstrained mode in underlay CR network in Rician fading channel. The BER performance is also presented for different number of secondary interference sources which are located at fixed distance in one case and they are assumed to be distributed as PPP in another case.     

一种基于全双工的无线网络MAC协议设计与性能分析

半双工无线电台使用两个独立频段实现信息同时发送和接收,而全双工无线电台则使用一个频段实现信息同时收发。为了进一步提升全双工网络性能,提出一种应用于全双工网络的简单高效的MAC协议——全双工MAC（full duplex MAC,FD-MAC）协议,该协议能够兼容IEEE 802.11 MAC协议。在综合考虑物理层和MAC层的基础上,分析了使用FD-MAC协议的全双工无线网络的性能。数值和仿真结果证明,和已有的全双工网络MAC协议相比,FD-MAC协议具有更优的网络吞吐性能和更低的能量消耗。     

Optimum Combining in Digital Mobile Radio with Cochannel Interference

This paper studies optimum signal combining for space diversity reception in cellular mobile radio systems. With optimum combining, the signals received by the antennas are weighted and combined to maximize the output signal-to-interference-plus-noise ratio. Thus, with cochannel interference, space diversity is used not only to combat Rayleigh fading of the desired signal (as with maximal ratio combining) but also to reduce the power of interfering signals at the receiver. We use analytical and computer simulation techniques to determine the performance of optimum combining when the received desired and interfering signals are subject to Rayleigh fading. Results show that optimum combining is significantly better than maximal ratio combining even when the number of interferers is greater than the number of antennas. Results for typical cellular mobile radio systems show that optimum combining increases the output signalto-interference ratio at the receiver by several decibels. Thus, systems can require fewer base station antennas and/or achieve increased channel capacity through greater frequency reuse. We also describe techniques for implementing optimum combining with least mean square (LMS) adaptive arrays.     

Improving Efficiency of Resource Usage in Two-Hop Full Duplex Relay Systems based on Resource Sharing and Interference Cancellation

This letter presents a new full duplex relay (FDR) system that features more efficient use of time resource and antennas. The proposed FDR system is constructed based on timeand antenna-sharing and elimination of underlying interference. The underlying interference caused by time- and antenna-sharing is eliminated using precoding. We propose a design for the precoder and decoder, and investigate the achievable rate of the proposed FDR system when the precoder and decoder are applied. Simulation results show improved achievable rate and BER performances with the proposed FDR system compared to half duplex and conventional full duplex relay systems.     

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。     

利用小波包分析抑制窄带干扰

为了能够有效抑制窄带干扰，根据小波包具有任意多尺度分解的特性，以及在时、频域具有表征信号局部信息和捕捉干扰信号特征的能力，利用小波包分析技术提取和滤除干扰分量，从间断窄带干扰和持续窄带干扰两种情况着手，进行除噪并重构信号，改善信号性能，提高了信噪比。利用仿真结果，说明了小波包抑制窄带干扰的有效性。     

基于NOMA的协作中继网络安全性能分析

由于非正交多址接入(Non-orthogonal Multiple Access,NOMA)能够显著提升系统的频谱资源利用率,在下一代移动通信中得到广泛应用。对NOMA环境下多中继协作网络的最优中继选择方案和系统安全性能进行了分析和讨论,其中包含窃听者仅窃听中继和窃听者同时窃听中继及源节点这2种情况下的系统安全性能表现,并与相同场景下正交多址接入(Orthogonal Multiple Access,OMA)网络进行了对比。最终的理论分析和仿真结果表明,在所提出系统模型中,当信道条件相同时,NOMA网络总能取得相较于OMA网络更好的安全性能,同时随着系统中继节点数目的增多,NOMA网络在物理层安全性能上获得更大的优势。     

Performance Analysis of Narrowband Interference Suppression in Orthogonal Code ModulationSpread Spectrum System

1IntroductionInaspreadspectrumsystem,theuser'ssignalisspreadtoawidebandsignalfortransmission,thenthereceivedsignalswillbedecorrelatedbacktotheoriginalone.Theprocessinggainresultedfromthisprocessprovidestheadvantagesofperformanceimprovementtocombatint...     

Amplify-and-Forward Cooperative OFDM with Multiple-Relays: Performance Analysis and Relay Selection Methods

In this paper, we investigate a cooperative system with multiple relays and amplify-and-forward relaying over frequency-selective channels. To extract the available multipath diversity, we employ orthogonal frequency division multiplexing (OFDM) with precoding. Through the derivation of pairwise error probability (PEP), we demonstrate that PEP is not a simple exponential function of the signal-to-noise ratio (SNR), but it includes a term that involves some power of logarithm of the SNR. If that term is ignored, the diversity order is given by the summation of the channel length in the direct link and the minimum of channel lengths in each relaying link confirmed by simulation results. Based on the PEP expression, we also propose two relay selection strategies; one is on a per-subcarrier basis and the other is on an all-subcarrier basis. Our simulation results indicate that both strategies result in performance improvements although the per-subcarrier method performs better.