Distribution of outage intervals in macrodiversity cellular systems

A general model for the analysis of outage intervals in mobile radio systems with macrodiversity is proposed. In a log-normal shadowing environment, reception diversity from two base stations is considered in the general case of different fading margins. Through a level-crossing analysis, the probability density function (PDF) of the outage interval is derived. It is seen that exact expressions can be obtained for the average outage occurrence rate and the average outage duration. The exact expressions are used to also improve the accuracy of the PDF at small values of the fading margins, by forcing the PDF to meet the exact average through a proper choice of its parameters. As a particular case, explicit solutions are derived for minimum duration outages     

Theoretical Characterization and System Impact of the Hinge Model of PMD

Modeling of the polarization-mode dispersion (PMD) temporal changes in long fiber routes represents a critical aspect of system outage characterization. In this paper, an analysis of the PMD temporal statistics in links obeying the recently proposed hinge model is presented. The analytical expression of the differential group delay probability density function is derived and used to show that the outage probability is channel specific in a wavelength-division-multiplexed system. The existence of outage-free channels, which represents one of the most important implications of the hinge model, is demonstrated and quantified. The frequency dependence of the temporal statistics is also characterized, and an expression for PMD-induced pulse broadening is derived     

分布式天线系统中的系统下行中断概率分析

本文针对分布式天线系统的系统下行中断概率问题展开研究.文章首先建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型.接着,在接收端采用最大比合并的方式接收信号,并运用矩生成函数推导出输出信噪比的概率密度函数.然后,对分布式天线采用选择传输策略,并分析出给定移动台位置时的中断概率的表达式.最后,考虑小区内移动台任意分布特...     

On the difference of two chi-square variates with application tooutage probability computation

An expression for the cumulative distribution function evaluated at zero of the difference of two chi-square variates with different number of degrees of freedom is derived and applied to the outage probability computation of cellular mobile radio systems in fading channels. In particular, a generic result is developed for this probability which takes on several forms, the simplest of which, is a single integral with finite limits and an integrand composed of elementary (exponential and trigonometric) functions. The results are applicable to cellular systems that are subject to independent identically distributed (i.i.d.) interfering signals and that employ maximal-ratio combining reception over i.i.d. diversity paths. Various fading channel models are assumed for the desired signal and interferers. For each desired signal/interferer combination, the outage probability is expressed in closed form in terms of a set of parameters that characterize the particular scenario. A tabulation of these various scenarios and their associated parameters for channels of practical interest is included     

基于STBC的无线认知NOMA系统物理层安全性能研究

基于非正交多址接入（NOMA,Non-Orthogonal Multiple Access）的认知无线电（CR,Cognitive Radio）网络物理层传输面临主用户干扰和第三方窃听双重干扰威胁.本文提出利用空时编码（STBC,Space Time Block Coding）技术提高认知用户物理层安全性能,推导了任意认知用户的安全中断概率闭合表达式.通过蒙特卡洛仿真进行验证,结果表明,所提STBC-CR-NOMA相比未采用STBC编码方案的CR-NOMA可以明显提高用户的安全中断概率,且随着认知发射功率的增大,近端用户安全中断性能提高越大,而远端用户安全中断性能提升受认知基站发射功率的影响较小.仿真结果还表明,通过调整功率分配系数对远端用户和近端用户的安全中断性能影响不同.     

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.     

Analysis of random access channel in UTRA‐TDD on AWGN channel

The random access channel (RACH) in UTRA‐TDD systems is an uplink contention‐based transport channel that is mainly used to carry control information from mobile stations to base stations. In this paper, we study the performance of RACH on an additive white Gaussian noise (AWGN) channel whereby successful transmission of a burst requires the spreading code chosen to be collision‐free and the burst is error‐free after convolutional decoding. Based on this model, the code‐collision probability, the data bit error probability and the RACH channel capacity are derived. The random retransmission delay mechanism is not specified in UTRA‐TDD. We therefore choose an access mechanism with binary exponential backoff delay procedure similar to that in IEEE 802.11. Based on that mechanism, the blocking probability and the first two moments of the delay are also derived. Compared with the mean, the standard deviation is found to be very high. Copyright © 2004 John Wiley & Sons, Ltd.     

Performance analysis of cellular mobile systems with successive co-channel interference cancellation

This paper presents an analytical framework for the performance evaluation of cellular mobile radio systems equipped with smart antenna systems. In particular, the paper focuses on low-complexity systems which are able to successively suppress the strongest active interferers. The desired user fading statistics is assumed to be flat Rayleigh, Rician, or Nakagami, whereas the interfering signals are assumed to be independent and subject to slow flat Rayleigh fading. The paper starts by presenting generic closed-form expressions for the the carrier-to-interference ratio probability density function after interference cancellation. Based on that, exact closed-form expressions for the outage probability and average error rate formulas are derived. Finally, a comparison with a practical cancellation scheme and the impact of some practical considerations on the performance of successive interference cancellation are investigated. More specifically, the effect of traffic loading, the overall spectral efficiency gain, and the impact of time delay are studied.     

On the Performance of Cellular Two-Way Relay Systems with Analog Network Coding and Multiuser Diversity

We consider a cellular two-way relaying system in which a multi-antenna base station (BS) communicates bidirectionally with one of several single-antenna mobile stations (MSs) via a single-antenna relay using analog network coding. We employ MS selection coupled with beamforming at the BS so as to maximize the end-to-end signal-to-noise ratios. In the considered system, the target rates at the sources can generally be different owing to the asymmetric traffic flow in opposite directions. With such a general setup, we perform an overall system outage probability analysis over Rayleigh fading channels. For more insights, we derive a closed-form asymptotic expression for overall outage probability and an upper bound expression for ergodic sum-rate of the system. Based on these expressions, we show that the system achieves a performance gain, and a diversity order of minimum of the number of BS antennas and the number of MSs. Moreover, we address the problem of optimization of relay location in order to minimize the overall system outage under asymmetric traffic conditions. Finally, we provide numerical and simulation results to corroborate the theoretical analysis and the advantages offered by the proposed scheme.     

Power Allocation and Control in Multimedia CDMA Wireless Systems

This paper proposes an analysis of outage performance of a Direct Sequence-Code Division Multiple Access (DS-CDMA) wireless system with heterogeneous traffic. Imperfections in closed-loop power control and the activity characteristics of any traffic source in the system are taken into account. For given requirements of signal-to-(noise + interference) ratio and outage probability of every user in the system, the system capacity is derived in terms of the maximum number of users of each class that can be accomodated. The optimization problem is explicitly solved for a system consisting of a single cell and an approach is outlined for solving the optimization problem in a multi-cell system. The analysis is carried out by resorting to various approximations of Multiple Access Interference (MAI), that require different methods for solving the optimization problem and yield different degrees of accuracy. From numerical results it is seen that optimal power allocation is essential to limit the effects of power control imperfections, mainly in the case of non uniform amplitudes of residual power fluctuations. In the second part of the paper, a performance study of fixed step closed-loop power control algorithms is presented. A detailed simulation of the power control loop evidences that fast fading phenomena can not be easily tracked, even at moderate Doppler spread. Statistics of residual power fluctuations are estimated and can be used to support the assumptions in the first part of the paper. Furthermore, second order statistics of the controlled channel are estimated, and second order outage statistics (average rate and duration of outage events) are derived as a quantitative measure of residual channel burstiness.     

两级中继选择的协作CR-NOMA网络性能分析

本文研究了中继选择方案对协作下认知非正交多址（CR-NOMA）网络中断性能的影响,提出了一种两级中继选择方案。第一时隙在保证主用户服务质量的基础上,次级网络源节点向认知中继集群广播叠加信号。第二时隙认知中继提供解码转发服务,协助源节点传输信息。基于上述假设,推导了次级用户中断概率的闭合表达式并给出了分析结果。证明相比于部分中继选择策略,两级中继选择策略可以达到更好的中断性能和更大的分集增益。同时本文的分析结果验证了备选中继节点数目和功率分配因子对系统中断性能的影响,蒙特卡罗仿真验证了理论结果。      

Outage probability in cellular mobile radio due to Nakagami signaland interferers with arbitrary parameters

Outage probability provides a fundamental performance measure of the grade of service for cellular mobile radio systems. Determination of the outage probability in a Nakagami (1960) mobile environment is particularly important since Nakagami fading is, as shown by various empirical measurements, the most appropriate model in many practical applications. Effective techniques have been developed recently to determine outage probability in the presence of multiple Nakagami interferers by assuming that the fading parameters of both signal and co-channel interferences are integer-valued. However, the general problem with arbitrary Nakagami signal and interferers remains unsolved. A new technique is presented, which allows the Nakagami distributions for both signal and interferers to be arbitrary. Exact formulas for probability of outage with and without a constraint on minimum signal power are derived, and computer results are also presented to illustrate the theory     

Analysis of outage probability for in‐band device‐to‐device communications underlaying cellular network

One of the key strategies for jointly increasing throughput and optimum resource allocation in 5G is device‐to‐device (D2D) communications, which can be obtained by minimizing the outage probability considered as an objective function of optimization problem. To minimize this objective function, we found that outage probability should be modeled by jointly considering the effect of interference, noise, and multipath phenomena. In this paper, the exact formulas for outage probability of in‐band D2D communications underlying cellular network are proposed. In the proposed model, additive white Gaussian noise and Rayleigh multipath fading are considered into 2 radio resource reuse scenarios. In the first scenario, each D2D pair is allowed to reuse radio resource block of one cellular user, whereas in the second scenario, 2 resources of 2 cellular users can be reused. The proposed formulas are compared to the approximate (nonexact) ones, which models additive white Gaussian noise by a constant variance. The numerical analysis for the first and second scenarios show that the approximate formulas and respected exact ones are in accordance with simulation results in MATLAB. Moreover, based on nonorthogonal multiple access approach, 2 approximations for the nonexact and the proposed formulas are extracted, which are acceptable for multiple resource reuse scenario. As a remarkable result, simulation results show that when the distance of the D2D pair from the respected cellular user is more than 71 m (2 times greater than average distance between the D2D nodes), multiple‐reuse scenarios offer higher throughput compared to 1‐reuse scenario in an acceptable outage probability.     

Simulation of digital transmission over mobile channels at 300 kb/s

Studies of digital transmission over typical urban and suburban mobile channels using simulations that employ a local area model for the time varying mobile channel impulse response are discussed. The digital transmission techniques of coherently detected and differentially coherent detected versions of quadrature phase-shift keying (QPSK), Gaussian minimum shift keying (GMSK), and coherently detected binary phase-shift keying (BPSK) over example mobile channels are presented. Two measures of performance are considered; the mean bit error ratio (and irreducible bit error ratio), which is used to compare the robustness of the various modulation methods to delay spread, and the outage probability, which provides a measure of the overall transmission quality as would be perceived by a user. Emphasis is placed on results obtained for GMSK, which is the modulation scheme to be employed in the Pan-European digital cellular mobile system. The effects of RMS delay spread on the mean bit error ratio, mean irreducible bit error ratio, and probability of outage are considered for different channel types     

Shadowing fade margin and coverage probability analysis for HAP mobile communication systems

An existing elevation dependent shadowing model for high‐altitude platform (HAP) mobile communication in built‐up areas is employed to perform the area coverage probability analysis and fading margin computation for HAP mobile communication systems. A generalized expression for the PDF of the received signal power in the HAP coverage is derived. The shadowing fade margin model that can characterize different types of built‐up area is developed. Theoretical relations between shadowing fade margin and outage probability and cell coverage probability are given. Numerical simulation for isoflux coverage HAP‐based system shows that there is great difference in the value of shadowing fade margin under line‐of‐sight and non‐line‐of‐sight conditions for the same outage probability. It is also found that the cell coverage probability is insensitive to the variance of the shadowing fade margin in suburban environment whatever the size of the cell and for small cells in urban high‐rise environments.Copyright © 2012 John Wiley & Sons, Ltd.     

Performance analysis of microcellular mobile radio systems with shadowed cochannel interferers

A study is presented of microcellular mobile radio systems where the desired signal has Rician statistics and cochannel interferers experience lognormal shadowing as well as Rayleigh fading. This implies a Rician/Rayleigh-plus-lognormal microcell interference model. The probability density function of the signal-to-interference ratio is derived and used to evaluate the performance of microcellular systems in terms of the outage probability.<>     

Performance analysis of dual selection diversity in correlated Weibull fading channels

Ascertaining the importance of the dual selection combining (SC) receivers and the suitability of the Weibull model to describe mobile fading channels, we study the performance of a dual SC receiver over correlated Weibull fading channels with arbitrary parameters. Exact closed-form expressions are derived for the probability density function, the cumulative distribution function, and the moments of the output signal-to-noise ratio (SNR). Important performance criteria, such as average output SNR, amount of fading, outage probability, and average bit-error probability for several modulation schemes are studied. Furthermore, for these performance criteria, novel closed-form analytical expressions are derived. The proposed analysis is complemented by various performance evaluation results, including the effects of the input SNR's unbalancing, fading severity, and fading correlation on the overall system's performance. Computer simulation results have verified the validity and accuracy of the proposed analysis.     

Outage Performance for IDF Relaying Mobile Cooperative Networks

Cooperative communication is a key technique in fifth generation (5G) mobile wireless networks. In this paper, we study the transmit antenna selection (TAS) in mobile cooperative networks. We derive the exact closed-form outage probability (OP) expressions for two TAS schemes. Based on the derived OP expressions, the impact of power allocation on OP performance is evaluated. Then we obtain that the Monte-Carlo simulation results and the analysis results match very well. The OP performance is affected by the power-allocation parameter.     

Outage probability for lognormal-shadowed Rician channels

A new general outage probability expression for a Rician signal received among L Rician interferers is derived. This result is shown to cover previous published expressions involving Rayleigh signal/interferers as special cases. A new method is then applied to further extend the result to include the effect of lognormal shadowing on the outage probability (for microcellular mobile radio systems in Rician/Rician fading environments). New Rician/Rician outage probability curves against the normalized reuse distance and cluster size with and without lognormal shadowing effect are presented and discussed     

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.