Outage Probability and Average Channel Capacity of Amplify-and-Forward in Conventional Cooperative Communication Networks over Rayleigh Fading Channels

Performance of conventional cooperative communication networks using amplify-and-forward relay over independent and identically distributed Rayleigh fading channels is investigated in this paper. An expression for probability density function by using moment generating function is obtained. Further closed-form expressions of the outage probability and the average channel capacity are derived. The derived analytical results are compared with Monte Carlo simulations to confirm correctness of the derived expressions.     

Capacity Analysis of Opportunistic Cooperative Networks under Adaptive Transmission over Rayleigh Fading Channels

In this paper, opportunistic cooperative amplify-and-forward networks in conjunction with three different adaptive policies, namely optimal simultaneous power and rate adaptation (OPRA), constant power with optimal rate adaptation (OPA) and truncated channel inversion with fixed rate (TIFR), are investigated and compared in terms of Rayleigh channel capacity where the source adapts its rate and/or power level according to channel conditions while the best relay simply amplifies and then forwards the received signals. Furthermore, the effect of diversity combining on the network is studied by investigating two cases of maximal ratio combining (MRC) and selection combining (SC) equipped at the destination. To this end, the mathematically tractable form of the upper and lower bound of the end-to-end effective signal-to-noise ratio (SNR) is provided and then used to derive the closed-form expression of the Shannon capacity. Our results are verified through comparison with Monte Carlo simulations in some representative scenarios where we also illustrate that, among them, for an arbitrary number of cooperative relays, OPRA slightly outperforms ORA, which, in turn, outperforms TIFR.     

Probability of SNR Gain by Dual-Hop Relaying over Single-Hop Transmission in SISO Rayleigh Fading Channels

In this letter, we address the end-to-end signal-to-noise ratio (SNR) gain achievable by dual-hop relaying over the single-hop transmission in single-input single-output (SISO) flat Rayleigh fading channels. We deal with both nonregenerative and regenerative relaying schemes. To quantify the SNR gain, a closed-form expression of the probability of SNR gain is developed. The probability of SNR gain results in an explicit function of an average power ratio of the per-hop channel in dual-hop relaying to the channel in the single-hop transmission. We investigate impacts of the average power ratio as well as the relaying location on the SNR gain.     

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.     

Nakagami-m信道下全双工解码转发中继中断概率分析

研究存在残余自干扰（residual self-interference, RSI）条件下全双工解码转发中继的中断概率性能。在Nakagami-m信道下,推导了多跳解码转发（multi-hop decode-and-forward,MH-DF）策略和选择解码转发（selected decode-and-forward,SDF）策略的端到端中断概率闭合表达式和渐近表达式,分析了两种策略的可达分集度。结果显示,MH-DF策略的可达分集度为0,SDF策略的可达分集度由信道成型因子和中继功率伸缩方案决定。相比于MH-DF策略,SDF策略具有更优的中断概率性能和抗自干扰能力。      

Outage Performance of Dual-Hop AF Relay Channels with Co-Channel Interferences over Rayleigh Fading

This paper studies the outage performance of a dual-hop amplify-and-forward (AF) relay fading channel in an interference-limited environment. The relay and destination nodes are corrupted by multiple co-channel Rayleigh interferences. New exact closed-form expressions for the outage probability for channel-state-information (CSI)—assisted relay, in which gain is dependent on previous hop CSI and interference, are derived. Monte Carlo simulations are performed to verify the obtained theoretical results. For the cases where the number of interferers at the relay and the destination node is equal, we derive novel expressions for outage probability upper and lower bounds.     

Outage Probability and Ergodic Capacity Analysis for Two-Way Relaying System with Different Relay Selection Protocols

The outage probability and ergodic capacity analysis for decode-and-forward two-way relaying system is investigated in this paper. First, the exact expressions (or bounds) of outage probability, ergodic capacity and average bidirectional ergodic capacity (ABEC) for max–min relay selection, random relay selection and direct transmission protocols are derived through theoretic analysis, and performance comparisons among different relay selection protocols are developed. Then a novel maximum average bidirectional mutual information (MABM) relay selection protocol is proposed and analyzed. Simulation results demonstrate that the derived analytical results fit well with Monte-Carlo simulations. The proposed MABM protocol can always achieve larger ABEC than other protocols while keeping low outage probability, and the MABM and max–min protocols in this paper can always achieve better performance than the max–min selection and max-sum selection in Krikidis (IEEE Trans Veh Technol 59(9):4620–4628, 2010). In addition, outage probability, ergodic capacity and ABEC performance of the proposed protocol become worse while distance becomes larger.     

Outage Capacity of MIMO Poisson Fading Channels

The information outage probability of a shot-noise limited direct detection multiple-input–multiple-output (MIMO) optical channel subject to block fading is considered. Information is transmitted over this channel by modulating the intensity of a number of optical signals, one corresponding to each transmit aperture, and individual photon arrivals are observed at multiple receive photodetector apertures. The transmitted signals undergo multiplicative fading. The fading occurs in coherence intervals of fixed duration in each of which the channel fade matrix remains constant, and changes across successive such intervals in an independent and identically distributed fashion. The transmitter and the receiver are assumed to be provided with perfect channel state information (CSI). An optimization formulation for the outage probability problem is outlined and an exact characterization of the optimal average conditional duty cycles is provided.      

Outage Capacity of Spatially Correlated Multipath Fading Channels

In this paper, we study the effect of the scattering environment on the capacity of a single carrier linear modulation used in a multipath, multiple antenna channel. The work incorporates detailed 3D geometric channel models to assess the effect of spatial correlation. The analysis techniques, based on the pioneering work of Hirt and Massey (1988), provide a method to evaluate outage capacity. Channels that are derivatives of the ETSI standard hilly terrain and typical urban are considered in detail. The results quantify the loss of capacity produced by higher spatial correlation. When comparing signals of different bandwidth, wideband systems produce more diversity due to better temporal resolution. Surprisingly, narrowband systems gain some diversity back by being less susceptible to loss of diversity from spatial correlation     

On the Capacity of Secondary Networks Over Opportunistic Spectrum Access in Rayleigh Fading Channels

In this paper the effect of the opportunistic spectrum access on the spectrum utilization is studied in terms of the secondary network capacity measured at the secondary receiver. A mathematical model is developed to represent the secondary network capacity in Rayleigh fading channel. An exact analytical solution for the capacity is derived for both sensing and accessing fading channels. A numerical evaluation of the channel capacity is presented for different channel sensing and accessing schemes. The effects of detection and accessing channel parameters on the capacity are investigated. The analytical results that are validated by substantial simulations showed how the utilization of the network can be increased significantly by the suggested opportunistic spectrum accessing technique. It was found that when having a good sensing system with a high secondary user signal to noise ratio, accessing the licensed band increases and drives the spectrum utilization to its maximum. In addition, this work shows how the capacity can be positively affected by three factors: the secondary accessing channel, the primary user interference and the desired quality of service (QoS) of primary user. The awareness of a proper sensing scheme can maximize the spectrum utilization without degrading the QoS of primary users.     

Outage Probability of Opportunistic Amplify‐and‐Forward Relaying in Nakagami‐m Fading Channels

We address the outage performance for the opportunistic amplify‐and‐forward relaying strategies under Nakagami‐m fading channels. A closed‐form expression for the outage probability is derived. Simulation results verify our theoretical solutions.     

Scaled Selection Combining for Adaptive Decode-and-Forward Relaying in Dissimilar Rayleigh Fading Channels

This paper enhances the conventional scaled selection combiner (SSC) for decode-and-forward (DF) relay networks using adaptive M-ary quadrature amplitude modulation (M-QAM) to improve the spectral efficiency. Compared with the conventional SSC designed for the combining of identically distributed diversity branches using the same modulation level, the improved SSC allows all diversity branches to choose different modulation levels according to the dissimilar channel conditions. Different scale factors are used for all diversity branches to reflect not only the performance degradation caused by possible erroneous relaying but also different error-resistance abilities of different levels QAM. We derive the bit-error-rate (BER) expressions for DF relay networks using SSC in a recursive way, with all channels conforming to independently and non-identically distributed (i.ni.d.) Rayleigh fading. Newton’s method is employed to obtain the numerical solutions of the optimal scale factors minimizing the BER, and the approximations of the optimal scale factors are derived in closed form for high SNRs. Theoretical analysis and simulation results show that the improved SSC can effectively combine diversity branches with different modulation levels, and for a DF cooperative network with N relay nodes, SSC achieves the full diversity gain of N+1 if for each branch its source-to-relay SNR is proportional to the (N+1)th power of its relay-to-destination SNR.     

Cooperative Dual-Hop Relaying Systems with Beamforming over Nakagami-m Fading Channels

In this paper, we investigate the end-to-end performance of dual-hop relaying systems with beamforming over Nakagami-m fading channels. Our analysis considers semiblind (fixed-gain) relays with single antennas, and source and destination nodes equipped with multiple antennas. Closed-form expressions for the outage probability (OP), moment generating function (MGF), and generalized moments of the end-to-end signal-to-noise ratio (SNR) are derived. The proposed expressions apply to general operating scenarios with distinct Nakagamim fading parameters and average SNRs between the hops. The influence of the power imbalance, fading parameters, and antenna configurations on the overall system performance are analyzed and discussed through representative numerical examples. Furthermore, the exactness of our formulations is validated by means of Monte Carlo simulations.     

Opportunistic Beamforming over Rayleigh Channels with Partial Side Information

In recent years, diversity techniques have evolved into highly attractive technology for wireless communications in different forms. For instance, the channel fluctuations of the users in a network are exploited as multiuser diversity by scheduling the user with the best signal-to-noise ratio (SNR). When fading is slow, beamforming at a multiple antenna transmitter is used to induce artificial channel fluctuations to ensure multiuser diversity in the network. Such a beamforming scheme is called opportunistic beamforming since the transmitter uses random beamforming to artificially induce opportunism in the network [1]. Opportunism requires a large number of users in the system in order to reach the performance of the true beamforming that uses perfect channel state information (CSI). In this paper we investigate the benefit of having partial CSI at an opportunistic transmitter. In the investigation, we focus on the maximum normalized SNR scheduling where user?s feedback consists of SNR relative to its channel gain. We show that opportunism can be beneficially used to increase the average throughput of the system. Simulations support the analytical average throughput results obtained as the amount of CSI and the number of users vary.     

相关瑞利分集系统容量的研究

一般来说,充分利用无线信道的特性能够极大地提高通信系统的容量,但是对于相关瑞利信道的平均容量讨论的不多。文章借助于一种线性变换的方法,得出了一种相关瑞利分集情况下容量的近似表达式,简化了在通常情况下的复杂的表达式。数值计算的结果也形象地说明了相关系数对分集容量的影响,以及分集能够有效的提高系统的容量。     

瑞利快衰落信道下STBC的译码器设计

Alamouti提出的空时分组码(STBC)发射分集技术,其优良性能及低复杂性的译码方案是限制在准静态衰落信道的情况下的,通过研究发现此系统在时变快衰落信道时性能会有严重的损失。为了改善系统在快衰落信道下的性能,提出一种最小均方误差(MMSE)线性译码器,该译码器能够同时抑制噪声和干扰。理论及计算机仿真证明,MMSE译码器用于空时分组码发射分集系统中可以有效地改善无线信道的时变快衰落对系统性能的影响。     

A Simple Capacity Formula for Correlated Diversity Rayleigh Fading Channels

1　Introduction　Itiswellknownthatthesystemcapacitycanbeincreasedifweexploittherandomnessofmultipathpropagationappropriately .ThecapacityofMultiple InputMultiple Output (MIMO )isdiscussedinRef.[1 ].Ingeneral,theaveragechannelcapacitydependsonthecharacteristicsoffadingchannelsmostly .Andmostpaperonlyconsiderstheindepen dentandidenticallydistributedGaussianchannelvariable ,underthisassumption[2～3] ,havederived ,respectively ,theaverageandlimitingchannelcapac ity .　Theaimofthispaperistodet…     

On SNR Estimation Techniques for Turbo Decoding Over Uncorrelated Rayleigh Fading Channels With Unknown Fading Parameters

Three non-data-aided signal-to-noise ratio (SNR) estimator techniques are derived and compared for turbo decoding, in conjunction with block-coded binary-phase-shift-keying (BPSK) signals received over fully interleaved (i.e., uncorrelated) Rayleigh fading channels. These estimators, which do not require knowledge at the receiver of the channel SNR nor the power of fading amplitude, are optimized in terms of minimizing the estimation error by choosing an appropriate curve fit model and comparing their estimation errors, as well as their turbo decoding bit-error-rate (BER) performance. Turbo decoding performance evaluation results have demonstrated that the two SNR estimators, which use the ratios of the second moment to the square of the mean absolute value and the fourth moment to the fourth power of the mean absolute value of the received signals, respectively, result in comparable BER performance to the case of perfect SNR knowledge at the receiver. Furthermore, they outperform the third SNR estimator, which makes use of the ratio of the square of the second moment to the fourth moment, particularly in applications with relatively short code blocks.