Performance analysis of an adaptive receiver structure for digital mobile communications

In this paper we investigate the performance of a combined estimation/equalization technique for the mobile radio channel, assuming a GSM-recommended transmission format (narrowband TDMA with midamble, recommendation 5.04) and MSK modulation scheme. Channel estimation is performed via correlation of the received signal with a suitably modulated replica of the transmitted midamble. Equalization is then obtained by means of a maximum likelihood sequence estimation (MLSE) scheme in the form of a so-called Viterbi equalizer. Our analysis provides theoretical results concerning the bit error rate (BER) attained by the receiver for a given stationary multipath channel model. Simulation results are also presented in order to integrate and validate the theory.     

A comparison of GSM receivers for fading multipath channels withadjacent and co-channel interference

We evaluate and compare several data detection schemes used in GSM systems. In particular, we compare the performance of decision feedback equalization (DFE) and nonlinear data directed estimation (NDDE) to that of maximum likelihood sequence estimation (MLSE). Establishing the performance of the basic NDDE detector is a first step in investigating the applicability of block transmission techniques to GSM systems. Our simulation results, obtained both for fading multipath channels and adjacent- and co-channel interference scenarios, suggest that the NDDE offers certain performance advantages over the DFE, and the performance of both detectors is comparable to that of the MLSE for the SNR region of interest in practical systems. Thus, they both represent viable alternatives to the MLSE detector     

Performance analysis of SSC diversity receiver over correlated Ricean fading channels in presence of co-channel interference

A novel infinite-series-based approach for the performance analysis of a dual-branch switched-and-stay combining (SSC) diversity receiver operating over Ricean correlated fading channels in the presence of correlated Nakagami-m distributed co-channel interference (CCI) is presented. The performance analysis is based on outage probability (P_out) and average bit error probability (ABEP) criteria.     

Performance of M-QAM modulations for indoor radio communications with combined diversity and equalization techniques

Digital indoor radio communications systems have become an attractive proposal as they could provide the user high quality voice and low rate data services with total mobility. However, indoor communications are affected by multipath propagation that restricts their application imposing an upper limit on the system data rate. To overcome this drawback diversity and channel equalization could be considered. In this paper the performances of 4, 16 and 64-QAM modulations in a radio communications indoor environment are presented. The results show that a system without protection has very limited performance. Diversity techniques are efficient when the radio channel can be assumed to be non-selective. For systems operating in selective fading channels joint equalization and diversity techniques are necessary to fight the degrading effect introduced by the channel. Moreover, if correlation between the two diversity channels is taken into account, the system performances remain almost unchanged, assuming that the correlation coefficient between the two diversity branches is lower than 0.6 to 0.7 approximately.     

存在共道干扰的多径衰落环境中手机双天线系统性能研究

将城市室外电波传播模型、手机天线本征激励方向图以及信号合并方式相结合,建立了分析在具有共道干扰的多径衰落环境中手机双天线系统的性能模型。用这一模型研究了采用最优合并方式的手机上双单极子天线系统的性能,分析了合并性能受共道干扰强度、天线互耦以及机身的影响。     

Performance analysis of an FFH/BFSK receiver with product-combining in a fading channel under multitone interference

The bit-error probability (BEP) is evaluated for a fast frequency-hopping binary frequency-shift-keying (FFH/BFSK) spread-spectrum communication system over Rician fading channels in the presence of worst-case multitone jamming (MTJ) and additive white Gaussian noise (AWGN). A diversity reception scheme of product-combining is applied at the receiver. Two types of MTJ models, namely n=1-band MTJ and independent MTJ, are considered in this letter. To obtain the final decision statistics, the closed-form or a single finite integral expressions of cumulative distribution functions (CDFs) of the ratio of two square-law detectors' outputs per hop are derived. According to the numerical results, it is shown, unlike the known knowledge for the AWGN channel, that independent MTJ is more harmful than n=1-band MTJ for the product-combining receivers (L/spl ges/2) in fading channels.     

Performance analysis of an FFH/BFSK receiver with ratio-statistic combining in a fading channel with multitone interference

The bit-error probability (BEP) is evaluated for a fast frequency-hopping/binary frequency-shift keying spread-spectrum communication system over a frequency-nonselective, slowly fading channel with worst-case band multitone jamming and additive white Gaussian noise. A diversity reception technique with ratio-statistic combining is applied at the receiver. Both square-law and envelope detectors are utilized and analyzed. Based on circularly symmetric signal theory, the paper obtains the closed-form expressions of probability density function and cumulative distribution function of the ratio-statistic output. It is shown from the analytical results, and verified by simulation, that the BEP performance of the ratio-statistic receiver is sensitive to the fading effect on the desired signal, but is insensitive to that on the jamming tones. It is also shown that the envelope detector provides better performance than the square-law detector.     

移动通信中的CMA阵列抗干扰性能分析

移动通信中的CMA阵列具有抗多径干扰和抗共信道干扰能力。本文理论分析了实际信号环境下CMA阵列的抗多径干扰和抗共道干扰能力，并进行了计算机仿真，仿真结果表明，CMA阵列的抗多径干扰性能受随机相移、信号幅度、信号空间分布等因素的影响，当所需信号与多径干扰信号空间卫离度越大，CMA阵列的抗多径干扰性能越好。CMA阵列的抗共信道干扰性能较抗多径干扰性能要好，只要所需用户信号和共信道干扰信号不在同一入射方向，CMA阵列就可以将干扰信号抑制掉。     

Baseband performance of a pilot diversity system with simulated Rayleigh fading signals and co-channel interference

Using simulated Rayleigh-fading FM signals, the baseband performance of a diversity system that uses a separate pilot is studied. The effect of various RF/audio bandwidth expansion ratios is included. These results show an approach to a constant asymptotic baseband SNR for large expansion ratios, with diversity increasing this asymptote by 5 dB in the case of moderate to large interference and/or RF noise levels (9 to 15 dB below the carrier), to over 10 dB in the case of lower impairment levels (21 to 27 dB below the signal level). Assuming the usual hex-cell radio coverage plan, and a propagation law of the form r^-n, n = 3 or 4, bandwidth expansion ratios of about three to six seem to yield the most efficient RF spectrum utilization in many practical situations. The number of required channel subsets (cells) is strongly influenced by the propagation law ranging from about 19 for n = 3, to about 7 for n = 4.     

Effect of coding in digital microcellular personal communicationsystems with co-channel interference, fading, shadowing, and noise

An analytical model is developed for the performance of a microcellular radio network in the presence of cochannel interference and additive white Gaussian noise. The modulation schemes considered are binary phase-shift keyed (BPSK), binary frequency-shift keyed (BFSK), and quadrature phase-shift keyed (QPSK). The multiple-access channel is statistically modeled by one Rician-distributed desired signal and several uncorrelated Rayleigh plus log-normally shadowed interfering signals, propagating according to dual path loss law with a turning point. The performance is determined in terms of bit error rate (BER), outage probability, block error probability, crosstalk probability, and spectrum efficiency, considering both fast and slow multipath fading. The effect of error correction codes, consisting of blocks with equal number of bits, on the performance parameters is also studied. The computational results show that the propagation loss exponents, Rician factor, turning point, and cell size all plays a major role in the design of an efficient microcellular system     

Performance of an array receiver with a Kalman channel predictorfor fast Rayleigh flat fading environments

We develop an approach for using an antenna array for tracking fast Rayleigh flat fading channels and suppressing cochannel interference. The fast flat fading process is assumed to be a general autoregressive (AR) process in order to characterize temporal variation of channels and evaluate its effect on the receiver structure and performance. The optimal array receiver structure that minimizes the probability of error for BPSK signals is derived, which includes a Kalman filter to predict the fading channels. A simple integral expression for the probability of error is also derived for the optimal receiver. In particular, we analyze the case with identical shaping filters. An irreducible probability of error is shown to exist due to the prediction error of multiple channels. Another interesting observation from the study is that the diversity gain with m antenna elements in the presence of k interferences is usually greater than (m-k), even in the presence of channel prediction error. Simulations are carried out to verify the theoretical analysis     

多项式感知器的非线性映射性能分析及其格型实现

本文详细分析了多项式感知器的非线性映射性能，证明了满足Ｓｔｏｎｅ－Ｗｅｉｅｒｓｔａｓｓ定理的多项式感知器可以逼近任一连续函数，并具有与四层神经网络相一致的非线性映射能力。导出了便于ＶＬＳＩ实现的多项式感知器的格型实现算法。进行了计算模拟，并给出了相关的数值结果。     

Design and performance evaluation of a full-duplex operating receiver for time-hopping UWB

One of the most attractive features of time-hopping ultra-wide-band (UWB) transmission, largely ignored in the literature so far, is the possibility to operate in full-duplex mode, thanks to its very low duty-cycle. This allows a terminal to transmit and receive within the same time frame and frequency band, yielding a considerable saving of time and band resources at the radio-resource-management layer. In this paper, we propose a methodology to design channel estimation/synchronization and demodulation/decoding algorithms for a low-complexity receiver operating in full-duplex mode. The leading idea is simply to avoid, at reception, time intervals that correspond to pulse transmission. We also evaluate the performances of such a system through simulations over realistic propagation channels. Tomaso Erseghe was born in Valdagno, Italy, in 1972. He received the laurea degree and the PhD in Telecommunication Engineering from the University of Padova, Italy, respectively in 1996 and in 2002. From 1997 to 1999 he worked as an R&D Engineer at Snell & Wilcox, a British broadcast equipment manufacturer, in the areas of image restoration and motion compensation. From 2003 he is an Assistant Professor (Ricercatore) at the University of Padova. His research interests include fractional Fourier transforms, lossless encoding algorithms, and ultra-wideband transmission systems. Nicola Laurenti was born in 1970, in Adria, Italy. He graduated from the University of Padova with a laurea in Electrical Engineering in 1995, with a thesis on Image Reconstructions from Projections, and obtained a Ph.D. in Electrical and Telecommunications Engineering from the same University in February 1999, with a thesis on Implementation Issues in OFDM Systems. Since 2001 he is an Assistant Professor at the Department of Information Engineering, University of Padova. His research interests mainly focus on digital communications, especially multicarrier modulation and ultra wide band transmission, but also include signal theory, and the processing of audio and biomedical signals.     

Performance analysis of optimum combining in wirelesscommunications with Rayleigh fading and cochannel interference

Optimum combining for space diversity reception is studied in digital cellular mobile radio communication systems with Rayleigh fading and multiple cochannel interferers. This paper considers binary phase-shift keying (BPSK) modulation in a flat Rayleigh-fading environment when the number of interferences L is no less than the number of antenna elements N(L⩾N). The approach of this paper and its main contribution is to carry out the analysis in a multivariate framework. Using this approach and with the assumption of equal-power interferers, it is shown that the probability density function of the maximum signal-to-interference ratio (SIR) at the output of the optimum combiner has a Hotelling T² distribution. Closed form expressions using hypergeometric functions are derived for the outage probability and the average probability of bit error. Theoretical results are demonstrated by Monte Carlo simulations     

Performance of DSWC diversity system using suboptimum adaptive switching threshold in independent and correlated nakagami‐m fading channels

The use of dual switched combining (DSWC) diversity reception scheme, for combating the detrimental effects of fading on digital transmissions, is popular due to its simpler implementation. The performance of switched diversity strategy is dependent on the selection of the switching threshold. But, for the analysis and design of the DSWC diversity system, the closed form analytical solution for optimum adaptive switching threshold is not possible for most of the modulation schemes in correlated fading environment. This letter presents an approximate, but simple and closed form, generic expression for adaptive switching threshold, called in this case as suboptimum adaptive switching threshold, in independent and correlated Nakagami‐m fading channels for a wide range of binary and M‐ary modulation schemes. It is shown that the average symbol error rate (ASER) performance obtained using this suboptimum adaptive switching threshold is almost same as obtained using optimum adaptive switching threshold. Copyright © 2005 John Wiley & Sons, Ltd.     

Performance of two-way amplify-and-forward relaying with adaptive modulation over Nakagami-m fading channels

This paper investigates the performance of a two-way amplify-and-forward(AF)relay system with adaptive modulation over independent and non-identical Nakagami-m fading channels.The tight closed-form cumulative distribution function(CDF)expression of the instantaneous end-to-end signal-to-noise ratio(SNR)is provided.Further,approximate closed-form expression for the average spectral efficiency of the two-way AF system with adaptive modulation is obtained.Then,a tight lower bound of outage probability is deriv...     

Performance analysis of square arranged antenna array with SC and MRC receiver over Nakagami fading channel

In this paper, the performance of using a square array of four antennas for selection combining (SC) and maximal-ratio combining (MRC) of Nakagami correlated signals is investigated. The closed form of average output signal-to-noise ratio and bit error rate (BER) for SC with arbitrary four correlated branches is derived; the expression of BER with MRC is also derived by utilizing the characteristic function method. Two models for the angle of arrival (AOA), i.e., uniform and truncated Gaussian, are considered in the system performance evaluation. The effects of correlation coefficients and fading factor on the system performance are investigated through numerical examples, which show that the uniformly distributed AOA system outperforms the truncated Gaussian-distributed counterpart with small angular spread. The degradation of system performance in the presence of one-antenna failure is also investigated.     

Performance of an in-band adjacent-channel DAB system forfrequency-selective Rayleigh and Ricean slow fading channels underanalog FM interference

In support of the 1995-1997 DAB (digital audio broadcasting) testing conducted by the NRSC (National Radio Systems Committee), an IBAC (in-band adjacent-channel) scheme was developed by AT&T. Although not for use in the United States, bit error rate (BER) system performance under both fading environments and the existing analog FM broadcasting is important to quantify. This is because there may still exist other countries and environments where an IBAC approach to DAB is feasible and economical. Given this situation, an IBAC simulation model has been developed to allow for a performance analysis study within the mobile reception environment, which is dominated by Rayleigh and Ricean fading statistics. This paper presents the simulation results for coherent quadrature phase-shift-keying (QPSK) with nonlinear equalization for both frequency-selective Rayleigh and Ricean slow fading channel environments, along with co-channel, 1st-adjacent and 2nd-adjacent analog FM interference. The results indicate that for a country where spectrum availability dictates an IBAC solution, this approach may perform well under various fading and interference environments     

Performance evaluation of Passive Optical CDMA Networks using a linear parallel interference receiver in imperfect power cases

In this paper, we propose a transmission and reception block diagram to cancel interference in the case of multiuser Optical Code Division Multiple Access. We evaluate the performances of Passive Optical Networks using different transmitted powers. To highlight the problem and analyze imperfect power, we propose a new approach based on technical issues of two transmitter groups. These groups correspond to high and low multiple access interference issued from different power classes. A compensation factor is added to the linear parallel interference cancelation structure to improve channel propagation errors. Transmission errors are evaluated analytically and by simulation, considering synchronous and asynchronous cases. The error probabilities of the proposed optical code division multiple access system are estimated using Gaussian approximation. We show that the optimization of the compensation factor gives better performances in terms of bit error rate than other classical receivers. It also shows that this approach on the one hand, overcomes the problem of multiple services in a network source optical code division multiple access and on the other hand, it avoids the imperfect power effects for different users.     

Study on cognitive DF relaying cooperation with the mutual interference between primary and secondary users over Nakagami‐m fading channels

In this paper, the cognitive relay cooperation (CRC) wireless communication systems are investigated over Nakagami‐m fading channels. The decode‐and‐forward (DF) relay is employed to assist the communications between cognitive source and destination. Especially, to achieve full diversity order, we consider the case in which there is a direct path between cognitive source and destination. Besides the interference at primary users (PUs) created by secondary users (SUs), the interference at SUs created by PUs is also considered. For the interested CRC systems, we first achieve the exact expression for the CDF of the equivalent end‐to‐end signal‐to‐interference ratio (SIR) of CRC systems. Then, with the exact CDF, the exact average symbol error ratio (SER) and outage performance of CRC systems are achieved. The derivation is of significance, by which we can obtain a detailed knowledge about CRC systems. Though a single integral included in the derivation, it can be calculated numerically by employing some mathematical tools such as Matlab. At the same time, to obtain the insight and highlight the effect of system parameters on the considered CRC systems, by using the high SIR approximation, we obtain the asymptotic closed‐form expression of CDF as well as the ones of average SER and outage probability. From the asymptotic results, we can find the main factors that dominate the performance of CRC systems. The presented simulation results for outage probability and average SER show the derivations and simulations are in agreement. Moreover, in high SIR the achieved asymptotic results match well the exact ones. As a result, in high SIR we can employ the asymptotic closed‐form solutions to evaluate the exact performance of CRC systems. This can reduce greatly the implementation complexity. Besides this, the simulations also show that the diversity order is dominated by the fading severities of the secondary systems, i.e. the diversity order be proportional to the summation of the minimum fading severity between the two hops and that of the direct link. In contrast, the parameters of the primary systems only affect the coding gain, not the diversity gain. Copyright © 2014 John Wiley & Sons, Ltd.