认知双向中继网络在κ-μ衰落信道下的中断性能分析

针对认知双向中继网络在进行数据传输时面临的复杂无线信道场景问题,采用广义κ-μ分布构建认知双向中继网络中的视距和非视距无线传输信道,推导次网络在κ-μ衰落信道下的统一中断概率,并分析次网络在多种单一和混合衰落信道情况下的中断性能.仿真结果表明,无线信道的衰落程度对次网络的中断概率影响显著,依据衰落信道类型合理设置网络参...     

Nakagami-m信道协作网络编码中断性能分析

无线网络编码是一项能极大提高无线网络流量的有用技术,而协作分集可以有效地克服无线衰落的影响。研究了Nakagami-m信道下协作网络编码系统中断性能,分析了不同协作策略下的互信息表达式,推导了协作网络编码中断概率闭式表达式,并对分析的结果进行了仿真。仿真结果显示,在高SNR和谱效率R〈4条件下,协作网络编码中断概率较分布式空时编码性能SNR增益有接近2 dB的提高,并且随分布参数m值的增大,协作网络编码中断概率性能逐步改善。     

On the outage probability of large scale decode-and-forward relay wireless networks

This paper considers a wireless network consisting of large number of clusters, wherein each cluster represents a decode-and-forward (DF) relay network. Two main scenarios according to the distances among the nodes in the network are investigated. In the case of deterministic distances, the outage probability is obtained in a closed-form expression. Whereas for the case when these distances are independent random variables, the framework of Stochastic Geometry (SG) is exploited for deriving the closed-form of the outage probability in case of Rayleigh fading channel. Furthermore, a lower and upper bound for the outage probability in case of general fading channel have been also provided. Numerical simulations are carried out to validate the derived analytical expressions, and to illustrate how the obtained results can be utilized in interference management of such networks.     

基于冗余前置的机会编码协同中继策略

对于多节点的协同网络,机会编码协同总是选择最佳中继参与协同,能够取得优越的中断概率性能。为了进一步提高中断概率性能,提出了基于冗余前置的机会编码协同中继策略,并对其在瑞利平坦慢衰落信道条件下的中断概率性能进行了计算机仿真。结果表明,所提策略的中断概率性能明显优于机会编码协同中继策略,若所要求的中断概率为10-3,当潜在协同中继数目为7,协同等级为0.5,目标信息速率为1 bit/s/Hz的条件下,所提策略较机会编码协同中继策略可以获得1.9 dB的信噪比增益。     

Outage Capacity of the Fading Relay Channel in the Low-SNR Regime

In slow-fading scenarios, cooperation between nodes can increase the amount of diversity for communication. We study the performance limit in such scenarios by analyzing the outage capacity of slow fading relay channels. Our focus is on the low signal-to-noise ratio (SNR) and low outage probability regime, where the adverse impact of fading is greatest but so are the potential gains from cooperation. We showed that while the standard Amplify-Forward protocol performs very poorly in this regime, a modified version we called the Bursty Amplify-Forward protocol is optimal and achieves the outage capacity of the network. Moreover, this performance can be achieved without a priori channel knowledge at the receivers. In contrast, the Decode-Forward protocol is strictly suboptimal in this regime. Our results directly yield the outage capacity per unit energy of fading relay channels     

Performance of Dual Selection Combiners Over Correlated Nakagami-$m$Fading With Different Fading Parameters

This letter presents infinite series expressions for the outage probability, the probability density function, the average error probability for binary modulations, and the average signal-to-noise ratio of dual selection combiners over correlated fading with arbitrary fading parameters at each input of the combiner. The outage probability is calculated for both thermal noise and interference-limited scenarios. The results obtained for the outage probabilities specified for identical fading parameters at both branches of the combiner are contrasted with the results of other studies in the literature.     

基于放大重传的认知共存网络传输容量分析

采用随机几何方法对认知共存网络中认知用户对主用户造成的累加干扰进行建模,并在无衰落信道和瑞利衰落信道中分别分析了主用户采用放大重传协作通信模式下的中断概率和传输容量。仿真结果表明,放大重传模式可以有效降低共存网络中主用户的中断概率、提高主用户的传输容量,且易于实现。     

Outage probability analysis of multi-hop relayed wireless networks over η − μ fading channels

In this paper, we study the outage probability of multi-hop relayed wireless networks assuming independent but not necessarily identically distributed η − μ fading channels. In our analysis, we consider both regenerative and non-regenerative relays. To this end, we provide a novel expression for the moment generating function (MGF) of the reciprocal of the end-to-end signal-to-noise ratio (SNR) and we then use this expression to evaluate the end-to-end outage probability of the non-regenerative network via numerical inversion of the Laplace transform. Moreover, we provide a novel expression for the end-to-end outage probability of the regenerative network. It is worth mentioning here that the derived expressions can be reduced to several other expressions, such as Rayleigh, Nakagami-m, Hoyt, and One-sided Gaussian fading channels. Numerical and simulation results are provided to show the tightness of the derived expressions.     

Outage Probability Analysis of Dual-Hop Decode-and-Forward Relaying Over Mixed Rayleigh and Generalized Gamma Fading Channels

In this letter, outage probability of dual-hop decode-and-forward (DF) relaying scheme is analyzed over mixed Rayleigh and generalized Gamma fading channels. Cooperation model considered in this work consists of a source, a relay and a destination. It is assumed that source-relay and relay-destination channels experience Rayleigh fading and generalized Gamma fading, respectively. Exact outage probability expression is derived and outage performance is illustrated for both direct transmission and DF relaying scheme.     

Outage probability of opportunistic decode-and-forward relaying over Nakagami-m fading channels

In this article, the outage probability behavior of a relay network over Nakagami-m fading channels is analyzed. Both reactive and proactive opportunistic decode-and-forward (DAF) strategies are considered. The closed-form solutions to the outage probabilities on both opportunistic DAF strategies are derived. Simulation results conf'Lrrn the presented mathematical analysis.     

Performance analysis of cooperative multi‐carrier relay‐based UAV networks over generalized fading channels

The outage probability in a network of cooperative unmanned airborne vehicles (UAVs) over generalized fading channels is studied analytically using finite mixture with expectation maximization technique. A relay‐based topology with one ground control unit (GCU) is considered, where the cooperative UAVs can communicate with the GCU directly or through relay. The application the UAV is assigned for specifies the minimum required transmission rate the UAV should achieve. The outage probability of the system is defined as the probability that either the transmission rate over any of the links drops below a predefined minimum threshold for that link or the Relay‐GCU link is not able to transmit the aggregate data from all relayed UAVs and the minimum rate required by the relay UAV itself. Throughout the paper, expressions for the outage probability and the average achievable bit rate of a cooperative multi‐carrier system are derived over generalized fading channels. Finite mixture with expectation maximization algorithm is utilized to derive a simple approximate expression for the probability density function (pdf) of the achievable bit rate assuming adaptive M‐ary quadrature amplitude modulation (M‐QAM). This pdf is used to derive closed‐form expressions for the outage probability and the average bit rate. Copyright © 2011 John Wiley & Sons, Ltd.     

Capacity and optimal resource allocation for fading broadcastchannels .II. Outage capacity

For pt.I see ibid., vol.47, no.3, p.1083-1102 (2002). We study three capacity regions for fading broadcast channels and obtain their corresponding optimal resource allocation strategies: the ergodic (Shannon) capacity region, the zero-outage capacity region, and the capacity region with outage. In this paper, we derive the outage capacity regions of fading broadcast channels, assuming that both the transmitter and the receivers have perfect channel side information. These capacity regions and the associate optimal resource allocation policies are obtained for code division (CD) with and without successive decoding, for time division (TD), and for frequency division (FD). We show that in an M-user broadcast system, the outage capacity region is implicitly obtained by deriving the outage probability region for a given rate vector. Given the required rate of each user, we find a strategy which bounds the outage probability region for different spectrum-sharing techniques. The corresponding optimal power allocation scheme is a multiuser generalization of the threshold-decision rule for a single-user fading channel. Also discussed is a simpler minimum common outage probability problem under the assumption that the broadcast channel is either not used at all when fading is severe or used simultaneously for all users. Numerical results for the different outage capacity regions are obtained for the Nakagami-m (1960) fading model     

Outage Probability Analysis of Cooperative Diversity Networks Over Weibull and Weibull-Lognormal Channels

This paper presents the analysis of outage probability for a cooperative diversity wireless network using amplify-and-forward relays over independent non-identical distributed Weibull and Weibull-lognormal fading channels for single as well as multiple relays. To reach that end, a closed-from expression for the moment-generating function of the total signal-to-noise-ratio (SNR) at the destination is derived in terms of the tabulated Meijer’s G-function. Since it is hard to determine the exact probability distribution function of the SNR, a tight lower bound approximation is proposed. Simulation results are presented that show that the outage probability lower bound tends to be tight at high SNR values thus verifying the analytical results. The results also show the potential gain of relaying on the outage probability.     

On the energy utilization for WSN based on BPSK over the Generalized-K shadowed fading channel

Energy is a scarce resource in the battery-powered nodes of wireless sensor networks (WSNs). In this paper the energy utilization for WSN based on BPSK communications has been investigated over the Generalized-K shadowed fading channel. A comprehensive analysis is reported based on the various important performance metrics like: amount of fading, average bit error probability, outage probability and energy utilized per bit (EUB). Simulation results reveal that composite use of shadowing and fading degrade energy levels to a considerable extent and hence contribute in downsizing the network life-span. We have derived the EUB metric and performed its evaluation with respect to optimal transmit energy levels by varying fading and shadowing severity parameters. We also considered the impact of varying transmit energy levels on the outage probability and hence on transmit and EUB levels. Although, embedding of training sequences and re-transmissions do help in enhancing effective synchronization and improved reliability, but this is done at a cost of higher energy utilization. Under the given set of assumptions, it is observed that an decrease in fading by about 11 %, improves the EUB by about 7 %. With increase in outage probability by about 10 %, EUB improves by about 3 %. An increase in SNR by 6 % improves the EUB levels by about 7 %. The investigations reported in this paper may enable designers to optionally choose suitable parameters to make WSN communications energy-efficient.     

时间空间联合频谱检测认知协作分集系统的中断概率分析

无线网络中利用协作分集技术可显著提高传输性能。认知无线网络中采用时间空间联合频谱检测能更充分地利用主用户的空闲频谱空洞。本文对采用时间空间联合频谱检测的认知协作分集系统的中断概率性能进行分析,给出采用选择解码转发中继协议时在瑞利衰落信道下的准确中断概率闭合式。分析和仿真结果表明:采用时间空间联合频谱检测的系统的中断概率性能优于单独时间频谱检测和单独空间频谱检测的系统,而协作分集技术的引入也明显改善了认知用户的传输性能。中断概率的理论结果对于衡量和评估认知网络的频谱检测方案、协作传输方案的性能有重要的理论和实用价值。      

Exploiting cooperative diversity with non-orthogonal multiple access over slow fading channel

Non-orthogonal multiple access (NOMA) has attracted a significant attention to the research community as a potential candidate for 5G or future radio access. This article presents a NOMA-based cooperative network where a transmitter considered as a base station communicates simultaneously with two users treating as a far user and a near user via the help of a half-duplex decode-and-forward relay. We investigate the outage probability and the outage capacity of the proposed network over independent Rayleigh slow fading channels. Closed-form expressions of the outage probabilities are derived for both users. Approximate outage capacity of the users are also investigated at high signal to noise ratio regime. It has been shown that the proposed cooperative NOMA can achieve superior performance compared to the non-cooperative NOMA in terms of outage probability. The tightness between the simulation and theoretical results confirms the efficiency of the proposed protocol.     

Outage Probability of Cognitive Selective DF Relay Networks with Multiple Primary Nodes and Heterogenous Non-Identical Constraints

Outage probability analysis of cognitive selective DF relay networks with selection combining technique taking into account all the following issues is important: multiple SU relays, multiple PUs, non-identical independent Rayleigh fading channels, non-identical interference power limits of PUs, non-identical maximum transmission power limits of SUs, and non-identical noise powers in signals. However, no existing works solve this task exactly. In this paper, to overcome the complexity in analyzing such non-identical-parameter networks directly, we conduct the analysis in two steps indirectly. In the first step, we obtain outage probability expressions of identical-parameter networks. Then in the second step, we propose a method for transforming a non-identical-parameter network into a new identical-parameter network, meanwhile guaranteeing that the distributions of end-to-end signal to noise ratio of the two networks before and after the transformation are identical. Thus the outage probability of the identical-parameter network can be regarded as outage probability of the corresponding non-identical-parameter network. Numerical simulations validate our analysis results and confirm the feasibility of the two-step indirect analysis approach.     

Outage Probability in Full Spectrum Reuse Cellular Systems with Discontinuous Transmission

Co-channel interference has a very strong impact on the performance of cellular mobile radio systems; a performance measure to evaluate its effect is the outage probability. This work presents an analytical general formula for the outage probability evaluation in full spectrum reuse cellular systems with discontinuous transmission. In particular, both Nakagami and Rician fading along with log-normal shadowing have been considered in the signal propagation model. In addition, the discontinuous transmission strategy is considered. The results are applied to the throughput evaluation of a packet cellular radio network based on the slotted Aloha protocol.     

An Analytical Model for Evaluating Outage and Handover Probability of Cellular Wireless Networks

We consider stochastic cellular networks where base stations locations form a homogeneous Poisson point process and each mobile is attached to the base station that provides the best mean signal power. The mobile is in outage if the signal-to-noise-plus-interference ratio falls below some threshold. The handover decision has to be made if the mobile is in outage during several time slots. The outage probability and the handover probabilities are evaluated taking into account the effect of path loss, shadowing, Rayleigh fast fading, frequency factor reuse and conventional beamforming. The main assumption is that the Rayleigh fast fading changes at each time slot while other network components remain static during the period of study.     

Information outage probability of distributed STBCs over Nakagami fading channels

Space-time block codes (STBCs) allow utilising the diversity provided by multiple-input-multiple-output (MIMO) communication channels, thereby decreasing the outage probability for a given communication rate. The contribution of this letter is the derivation of a closed-form expression of the outage probability of distributed STBCs deployed over Nakagami flat fading channels with different channel gains and fading parameters.