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.     

Packet Radio Performance Over Slow Rayleigh Fading Channels

Expressions for the throughput and average packet delay for a Pure-ALOHA single-hop packet radio system operating in slow Rayleigh fading are derived. For noncoherent frequency-shift-keying (NCFSK), an exact closed form expression is presented. For coherent phase-shift-keying (CPSK) an excellent approximation for large packet sizes is derived. This approximation technique is valid in general for other modulation schemes and for other fading channel statistical characterizations. The packet length which maximizes the useful data throughput in slow Rayleigh fading is found. The results of this investigation indicate that a packet radio system can be designed with a modest link margin for fading and achieve identical throughput performance over a nonfading channel and a fading channel with only a small increase in average packet delay for the fading channel.     

Performance Analysis Over Unified Generalized Composite Fading Model

With the deep study of the Hamming distances of orthogonal arrays (OAs), the application of OAs has penetrated into many fields, one of which is to construct the key predistribution schemes (KPSs) for distributed sensor networks.In this paper, we define the Hamming distance distribution (HDD) of an OA and its uniqueness. Furthermore, we present some OAs with unique HDD. In KPSs based on these OAs, the calculations of metrics for evaluating connectivity and resilience can be simplified. We also illustrate that KPSs based on them have a wider application and better connectivity and resilience than the existing ones.

     

Performance Analysis of Generalized Selection Combining in Generalized Correlated Nakagami- m Fading

The exact performance of selection combining, hybrid selection/maximal-ratio combining (H-S/MRC), and threshold-based H-S/MRC in correlated Nakagami-m fading for positive integer values of fading parameter m, is analyzed for a particular correlation structure. This correlation model, though not general, is much more general than the equal-correlation case, and includes equal correlation as a special case. The symbol-error rate and outage probability of the three combining schemes are obtained by transforming the correlated branch gains into a set of conditionally independent branch gains. Numerical and simulation results show excellent agreement with theoretical results     

Performance of Non-coherent MFSK with Selection and Switched Diversity Over Hoyt Fading Channel

A closed-form expression of cumulative distribution function (CDF) of the instantaneous signal to noise ratio (SNR) in Hoyt fading channel is derived. This CDF and associated formulas are then used to find out the error probability of non-coherent M-ary frequency shift keying with multichannel reception. Simple finite-range integral expression for the symbol error probability (SEP) with selection diversity is found through CDF method. Next, closed-form expressions of moment generating functions (MGF) are presented for the switched diversity case and SEP values are calculated using the derived MGFs. Some other performance parameters like, outage probability and average SNR with switched diversity, are provided. In addition, analytic frameworks are presented for calculation of optimum switching thresholds that ensure minimum outage probability or minimum SEP. The analysis is quite general in the sense that it covers switch and stay combining and Rayleigh fading as special cases.     

Spectral Efficiency Evaluation for MRC Diversity Schemes Over Generalized Rician Fading Channels

In this paper, closed-form expressions for the capacities per unit bandwidth for generalized Rician fading channels are derived for power and rate adaptation, constant transmit power, channel inversion with fixed rate, and truncated channel inversion adaptation policies. The closed-form solutions are derived for the single antenna reception (without diversity combining) and maximal-ratio combining (MRC) diversity cases. Truncated channel inversion adaptation policy is the best policy for the single antenna reception case, while the channel inversion with fixed rate policy is the best policy for the MRC diversity case. Constant transmit power policy provides the lowest spectral efficiency as compared to the other policies with and without diversity.     

Adaptive Diversity Reception Over a Slow Nonselective Fading Channel

We extend some previous results on adaptive receivers with memory for slow nonselective Rayleigh fading channels to the case of diversity reception. The Bayes receiver in this case is shown to be a generalized maximal ratio combiner. Error probability performance is obtained for antipodal signals such as BPSK. A simple performance upper bound is also derived. Numerical performance results are presented for the particular case of a Markov channel model.     

Performance Evaluation of Underlay Cognitive Multi-hop Networks Over Nakagami-m Fading Channels

We derive a closed-form bit error rate (BER) formula for underlay cognitive N-hop networks operated over Nakagami-m fading channels where N is the arbitrary integer. This formula is corroborated by Monte Carlo simulations and useful for evaluating the network performance under different parameters such as modulation level, path-loss, maximum transmit power, tolerable interference power level, fading model, and the number of hops. Numerical results illustrate that underlay cognitive multi-hop networks suffer a high error floor and the BER performance not only depends on the number of hops but also the network topology. For the linear network model, the higher the number of hops, the better the network performance.     

Hybrid Digital-Analog Relaying for Cooperative Transmission Over Slow Fading Channels

Hybrid digital-analog coding schemes have been proposed in source-channel coding to increase the robustness toward channel mismatch, in the absence of transmitter channel state information (CSIT). Recognizing that the same kind of robustness is needed at the relay in a three-node relay network, we propose several novel relaying protocols based on hybrid digital-analog transmission. We compare the performance of the new schemes with traditional digital-only (decode-and-forward or compress-and-forward) or analog-only (amplify-and-forward) relaying, as well as to performance bounds corresponding to genie-aided compress-and-forward relaying. Our new protocols achieve significant gains in terms of achievable expected rates, and they are able to close in on the performance bounds. In particular, we conclude that the best overall performance is obtained by an adaptive combination of decode-and-forward and hybrid digital-analog relaying.      

采用广义正交序列的多载波DS-CDMA系统在瑞利衰落信道中的性能分析

在CDMA系统中，采用正交序列可以有效地减小多址干扰的影响。然后，当由于多径衰落的影响使码片间的相对移位增加时，系统中用户扩频序列间的相互正交性减弱，导致性能大大恶化。本文基于新近提出的广义正交序列，分析了采用该序列的多载波直接序列码多分址系统在瑞利衰落信道中的误比特性能。数值结果表明，当扩频序列间相互移位在零相关区之内时，扩频序列仍可保持正交，因而大大提高了系统误比特性能。     

Robust Transmit Antenna Selection with Phase Feedback Over Correlated Fading Channels

A new transmit antenna selection (TAS) scheme with phase feedback for multiple-input multiple-output systems is proposed in this paper. This scheme allows two or more transmit antennas to simultaneously use one radio frequency chain. By grouping the transmit antennas according to their similarities in instantaneous channel coefficients into two subsets and treating each subset as a single antenna, both hardware complexity reduction and antenna array gain can be achieved. Compared with the transmit antenna selection combined with space-time block code (TAS/STBC) scheme, the proposed TAS scheme provides excellent robustness, in terms of symbol error rate performance, against spatially correlated fading channels. Moreover, the proposed TAS scheme need not use STBC encoder and decoder which used in the TAS/STBC schemes. Therefore, the proposed TAS scheme is simpler than the TAS/STBC schemes in practical hardware implementation.     

Outage Analysis of Mixed Dual-Hop RF-FSO Communication System Over Fading Channels with Pointing Errors

Wireless Personal Communications - In this paper, we consider a mixed dual-hop RF-FSO communication system, where RF link is subjected to Rice fading, while FSO link experience double generalized...     

Spectrum Efficiency Evaluation for MRC Diversity Schemes Under Different Adaptation Policies Over Generalized Rayleigh Fading Channels

In this paper, closed-form expressions for the capacities per unit bandwidth for Generalized Rayleigh fading channels are derived for optimal power adaptation, constant transmit power, channel inversion with fixed rate, and truncated channel inversion adaptation policies. The closed-form solutions are derived for the single antenna reception (without diversity combining) and MRC diversity reception cases. Optimal power adaptation policy provides the highest capacity over the other adaptation policies both with and without diversity combining. Truncated channel inversion policy suffers a large capacity penalty relative to the optimal power adaptation policy as the number of degrees of freedom is increased. However, with increase in diversity, the capacity penalty for the truncated channel inversion policy decreases. Capacity gains are more prominent for channel inversion with fixed rate policy as compared to the other adaptation policies.

Performance Analysis of Wireless Networks Over Rayleigh Fading Channel

Employing a cross-layer approach, the explicit relationships between the fading channel characteristics and the significant teletraffic variables as well as the performance metrics in wireless network evaluation are formulated. In particular, the channel holding time, handoff probability, handoff call arrival rate, call blocking probability, call completion probability, and forced termination probability are developed, taking into account the carrier frequency (or equivalently wavelength), maximum Doppler frequency, and fade margin. In addition, the set of formulas are derived with the generalized assumptions for the call holding time and cell residence time. The analytical model has been validated by the simulation with the conventional exponential model and, additionally, the relaxed models for call holding time and cell residence time, e.g., Erlang and hyper-Erlang. The comparison demonstrates that the traditional result without considering the fading channel characteristics leads to substantially overestimated call blocking probability and call completion probability. The methodology presented in this paper provides a feasible manner for the wireless network cross-layer design and optimization.     

空时编码在瑞利衰落信道下的性能分析

以正交空时分组码为例讨论了空时编码技术的性能特征。给出了各种STC-OFDM系统的BER性能。理论分析和仿真结果表明,STBC-OFDM系统在频率选择性的瑞利衰落信道下,性能优于其它STC-OFDM系统。     

Performance Analysis of Dual-Branch Selection Combining Over Correlated Rician Fading Channels for Desired Signal and Cochannel Interference

System performances of dual selection combining over fading channels are analyzed. Fading between the diversity branches and between interferences is correlated and Rician distributed. Infinite series expressions for the probability density function, and the cumulative distribution function of the output signal-to-interference ratio are derived, which is the main contribution of this paper. Outage probability and the average bit error probability for noncoherent modulation schemes are also presented. Numerical results, presented in this paper, point out the effects of fading severity and correlation on the system performances.     

Reception of PSK Signals Over Fading Channels Via Quadrature Amplitude Estimation

We consider here a new approach to PSK signal detection over a slow nonselective Rayleigh fading channel which does not require a carrier recovery loop. The receiver achieves coherent demodulation by making use of estimates of the quadrature amplitudes of the received PSK signals in its likelihood ratio test. The receiver is assumed to have a memory containing information on the past received signals which enables it to generate the estimates. The error rate of the receiver can be evaluated analytically and computer simulation results are presented to verify the predicted performance.     

Performance of Transmit and Receive Antenna Selection in the Presence of Channel Estimation Errors

This letter considers the effect of channel estimation errors on the performance of space-time coded (STC) systems with transmit and receive antenna selection over quasi-static flat fading channels. By performing pairwise error probability analysis and presenting numerical examples, we show that the diversity order achieved with perfect channel state information (CSI) is still achievable with imperfect CSI used both at the antenna selection and the space-time decoding processes. We note that our results apply to general STC systems with both transmit and/or receive antenna selection based on largest received powers which can be estimated by any channel estimator.