Second‐Order Statistics of System with Microdiversity and Macrodiversity Reception in Gamma‐Shadowed Rician Fading Channels

In this letter, a wireless communication system with microdiversity and macrodiversity reception in gamma‐shadowed Rician fading channels is considered. Exact and rapidly converging infinite‐series expressions for the average level crossing rate and average fade duration at the output of the system are provided. Numerical results are presented graphically to illustrate the proposed mathematical analysis and to examine the effects of the system's parameters on the quantities considered.     

Wideband Propagation Measurements and Channel Implications for Indoor Broadband Wireless Local Area Networks at the 60 GHz Band

This paper addresses some wideband propagation characteristics for Indoor Broadband Wireless LANs at the 60 GHz band. Important system design characteristics from measured results obtained from two wideband 60 GHz LOS radio links are presented. Measurements had been undertaken using the swept frequency channel sounding method. Analysis from the complex frequency responses in a worst-case scenario have yielded to a lower coherence bandwidth value of 5 MHz. Minimum and maximum B_0.9coherence bandwidths obtained with a directional horn transmit and an omnidirectional receive antenna is 1.10 MHz and 105.33 MHz respectively. It has been observed that the coherence bandwidth fluctuates significantly with the location of the receiver with respect to the base station. These results can be used for modelling and design of future Indoor BWLANs.     

多用户单中继协作无线上行链路平均电平通过率和衰落持续时间

We investigate the average Level Crossing Rate (LCR) and Average Fading Duration (AFD) of multiuser single relay cooperation wireless uplinks over independent and non-identically distributed (i.ni.d) Rayleigh fading channels. We first present the statistical analyses of the first-hop equivalent envelope. Then, we investigate the LCR and AFD of an equivalent end-to-end envelope, and present the closed-form solutions to LCR and AFD, which are given with integral forms. Finally, we derive the Laplace approximations of LCR and AFD as well as the upper and lower bounds. The numerical results of LCR show that the upper bound is tight. For multiuser systems with different number of mobile users, the analyses indicate that the LCRs are approximately the same at the low level of the envelope. However, at the high level of the envelope there are reasonable differences among the curves of LCRs. Due to that fact that AFD is the inverse function of LCR, the results for AFD are the opposite.     

移动通信不规则传播环境多普勒频谱仿真与分析

对移动通信不同数目散射体分布下的接收信号多普勒频谱进行了仿真与分析,并从多普勒频谱得到了相应信号包络及其性能参数电平通过率、平均衰落时延（LCR、AFD）,并在此基础上指出散射体数目在一定程度上影响移动通信信号的多普勒频谱,从而影响信号性能。     

Second‐order statistics of system with N‐branch microdiversity and L‐branch macrodiversity operating over gamma shadowed Nakagami‐m fading channels

The problem concerning short‐term fading and long‐term fading (shadowing) and their deleterious effects on wireless systems performance has been in focus for a long time. In this paper, motivated by the results of propagation measurements in land‐mobile and indoor‐mobile systems, and by the fact that gamma distribution can describe shadowing reliably, Nakagami‐m distribution is used to model the signal envelope and gamma distribution is used to model the average signal power. Receive diversity with maximal‐ratio combining and selection combining is implemented at the microlevel and macrolevel, respectively. The general case is explored, which assumes that microdiversity and macrodiversity are provided through arbitrary number of channels. Because shadowing has larger correlation distance than short‐term fading, correlated macrodiversity channels are studied. This paper investigates the dynamics of the received signal. A novel rapidly converging infinite‐series expression for average level crossing rate and average fade duration are obtained. Numerical results are graphically presented to examine the impact of fading severity, shadowing severity, number of diversity branches at the microlevel, number of base stations and correlation between base stations to the system's performance. Computer simulations are also performed to verify the validity and the accuracy of proposed theoretical analysis. Copyright © 2012 John Wiley & Sons, Ltd.