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We propose an efficient algorithm for estimating the code timing of direct-sequence code-division multiple-access (DS-CDMA) systems that consist of an arbitrary antenna array at the receiver and work in a flat-fading and near-far environment. The algorithm is an asymptotic (for large number of data samples) maximum-likelihood (ML) estimator that is derived by modeling the known training sequence as the desired signal and all other signals including the interfering signals and the additive noise as unknown colored Gaussian noise. The algorithm does not require the search over a parameter space and the code timing is obtained by rooting a second-order polynomial, which is computationally very efficient. Simulation results show that the algorithm is quite robust against the near-far problem and channel fading. It requires a shorter training sequence than the single-antenna-based estimators 相似文献
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Joint linear transmitter and receiver design for the downlink of multiuser MIMO systems 总被引:3,自引:0,他引:3
Jinfan Zhang Yongle Wu Shidong Zhou Jing Wang 《Communications Letters, IEEE》2005,9(11):991-993
In this letter, we address the problem of designing jointly the linear transmitter and receiver for the downlink of Multiuser MIMO system, using minimum total mean square error criterion (T-MMSE), subject to a total transmit power constraint. We show that transmitter and receiver under such criterion could be realized through a joint iterative algorithm. The convergence of the proposed algorithm is proved. Simulation results have also been provided to demonstrate the feasibility of this new method. 相似文献
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The development of new hybrid diversity methods has been demanded by the continuous growth of information rates. These schemes achieve improved balance between hardware complexity and performance, in relation to conventional ones. In this paper, a new hybrid switched diversity system is proposed. It is called generalized multi‐branch switch and examine combining. The new scheme is a generalization of the classic one known as switch and examine combining with considerably improved performance. The performance of this scheme is analyzed over independent and identically distributed Nakagami‐m fading channels using well‐known performance and complexity measures. More specifically, important performance metrics, such as the outage probability, the average bit error rate, and the capacity under different adaptive transmission policies, have been analytically studied. It is shown that the proposed approach offers an important improvement on the performance, without considerably affecting the complexity. 相似文献
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Optimization of the capacity of a single-cell code-division multiple-access (CDMA) system, both from the perspective of the maximum number of users that can be served at a required quality of service level and from the information theoretic perspective, has been recently shown to be achieved by the same joint transmit and receive strategies. We propose an alternating minimization based iterative algorithm that updates the transmitters and the corresponding receivers of the users. The algorithm is suitable for online implementation, and the objective function is suitable for extension to multicell networks, both of which are in contrast with the previously proposed algorithms. We show that the algorithm is provably convergent to the optimum signature sequences and the corresponding receivers. 相似文献
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In code division multiple access (CDMA) mobile radio systems, both intersymbol interference and multiple access interference arise which can be combated by using either elaborate optimum or favorable suboptimum joint detection (JD) techniques. Furthermore, the time variation of the radio channels leads to degradations of the receiver performance. These degradations can be reduced by applying diversity techniques. Using coherent receiver antenna diversity (CRAD) is especially attractive because only the signal processing at the receiver must be modified. In the present paper, the application of CRAD to the more critical uplink of CDMA mobile radio systems with suboptimum JD techniques is investigated for maximal-ratio combining. The authors study six different suboptimum JD techniques based on decorrelating matched filtering, Gauss-Markov estimation, and minimum mean square error estimation with and without decision feedback. These six suboptimum JD techniques which are well-known for single antenna receivers are extended for the application to CRAD. A main concern of the paper is the determining of the SNR performance of the presented JD techniques for CRAD and the achievable average uncoded bit error probabilities for the transmission over rural area, typical urban and bad urban mobile radio channels are determined 相似文献
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》1976,22(2):200-210
Joint optimization of transmitter and receiver filters in a pulse-amplitude modulation (PALM) system with an arbitrary but fixed Viterbi detector is considered. Optimization is performed under an average transmitted power constraint with respect to a new criterion called the effective mean-square error (EMSE). It is shown that the optimization problem is convex. A necessary and sufficient condition for optimality is derived, and a method for optimization is proposed. Numerical results are obtained for a channel with coaxial cable characteristics. 相似文献
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Unifying and generalizing the works of Cai and Giannakis and Oien et al., the performance of an adaptive trellis-coded modulation system where receive antenna diversity is implemented by means of maximum ratio combining is analyzed and optimized. As in the work of Cai and Giannakis, the analysis is done in the presence of both estimation and prediction errors. Rayleigh fading on each subchannel is considered, with the estimation and prediction being performed independently on each subchannel. The system optimization process is done in such a way that the throughput is maximized under a bit-error-rate (BER) constraint. The numerical example employs a Jakes-fading spectrum and shows how the power should be distributed between pilot and data symbols and how often pilot symbols should be transmitted for maximum throughput under an instantaneous (with respect to the predicted channel) BER constraint. 相似文献
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从对计算机光互连的实用要求出发,实现了用集成化的发送器和接收器经光纤连接器组成收发对后,能很好地在4×4多处理机系统内用光互连代替电互连。着重探讨了发送器和接收器的结构、设计,以及工艺改进途径,对互连器件的配套选择、性能测试作了一定工作,使之能方便使用。 相似文献
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Tarng J.H. Ruey-Shan Chang Jiunn-Ming Huang Yih-Min Tu 《Vehicular Technology, IEEE Transactions on》2000,49(2):457-466
This study presents a novel hybrid model based on a two-dimensional (2-D) site-specific model and a statistical model to investigate space diversity in indoor environments. The statistical model describes the field scattered by rough surface boundaries and randomly positioned scatterers, which may be important when one or both of the receiving and transmitting antennas are close to the boundaries of the scatterers. Comparing the computed spatial correlation with the measured one with the transmitting frequency at 2.44 GHz at many different sites demonstrates the effectiveness of the hybrid model. In addition to accurately predicting field strength, the hybrid model can quantify the relative mean contribution of diffused scattering in an indoor environment with a factor r. The factor is equal to the ratio of ensemble average of a randomly scattered envelope to the spatially averaged envelope. Its optimum value is in a narrow range from 0.3 to 0.5 when the intensity fluctuation at the measurement sites is in or close to saturation regions, where a large number of micromultipaths are generated. This finding confirms the relative ease in applying the hybrid model. Experimental results suggest that choosing r=0.4 in a saturation allows the hybrid model to yield a satisfactory performance, as confirmed by a blind test. Moreover, good diversity gains can be obtained with an antenna spacing greater than or equal to one wavelength. Our results further demonstrate that the diversity gain of horizontally spaced antennas exceeds that of vertically spaced antennas 相似文献
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A signal transmitted through a wireless channel may be severely distorted by intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on frequency domain equalization (FDE) with a regularized zero forcing (RZF) equalizer and parallel interference cancellation with a unit clipper decision function (CPIC) to combat both the ISI and the MAI. We call this receiver the FDE-RZF-CPIC receiver. This receiver is suitable for downlink zero padding CDMA cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) of the data received by the proposed receiver is evaluated by computer simulations. The experimental results show that the proposed receiver provides a good performance, even with a large number of interfering users. At a BER of 10?3, the performance gain of the proposed receiver is about 2 dB over the RAKE receiver with a clipper decision function and PIC in the half-loaded case (eight users) and is much larger in the full-loaded case (16 users). 相似文献
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This paper proposes and demonstrates a new architecture for the transmission, heterodyne reception, and correlation of direct-sequence (DS) signals encoded onto an optical carrier. The approach is practical for pseudo-noise in-modulated laser radar and free-space optical-code-division multiple-access communications. Although the local oscillator is free running, we show that the received signal is free from laser phase noise. Furthermore, by applying DS coding to both the transmitted signal and the local oscillator, the delay required for correlation can be realized via a combination of electrical and optical means. 相似文献
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《Vehicular Technology, IEEE Transactions on》1987,36(2):63-70
A new receiver diversity scheme for differential detection of minimum shift keying (MSK) is proposed. The signal from each receiving branch is translated to a different IF frequency. The IF signals are summed and then detected by a common differential detector. The diversity scheme does not need phase adjusters, signal quality measurement circuits or a switching controller; moreover the error rate performance is equivalent to that of postdetection equal gain combining diversity, which needs plural complete receiving systems. Theoretical analysis and computer simulation results show that the diversity gain of the proposed scheme is about 13 dB at a 10-3error rate under Rayleigh fading and 5 dB under Rician fading when the signal-to-interference power ratio is 10 dB. The static error rate performance improvement was confirmed by experimental test results. Simulation results with data from mobile propagation studies are also shown. Even in heavily shadowed cases, the probability that fading attenuation is less than 17 dB is improved from 80 to 99 percent, and a 7 to 13 dB improvement in margin requirement for 99 percent of time operation is achieved. 相似文献
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Horimatsu T. Iwama T. Oikawa Y. Touge T. Makiuchi M. Wada O. Nakagami T. 《Lightwave Technology, Journal of》1986,4(6):680-688
Compact transmitter and receiver modules with monolithic optoelectronic-integrated circuits, i.e., OEIC's, are demonstrated, and 400- and 800-Mbit/s transmission experiments are successfully carried out over up to 4 and 2 km, respectively, with these modules, for the first time. The design of the monolithic-integrated circuits and the compact module structure are presented. The soldering technique based on the use of YAG laser simplifies the packaging procedures, and an efficient and simple scheme for coupling between OEIC's and fibers make the OEIC modules compact. Both modules are attractive for applications in high data-rate communication systems, particularly in local area networks, CATV systems, and intra-office links. 相似文献
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Full-CMOS 2-GHz WCDMA direct conversion transmitter and receiver 总被引:1,自引:0,他引:1
Kang-Yoon Lee Seung-Wook Lee Yido Koo Hyoung-Ki Huh Hee-Young Nam Jeong-Woo Lee Joonbae Park Kyeongho Lee Deog-Kyoon Jeong Wonchan Kim 《Solid-State Circuits, IEEE Journal of》2003,38(1):43-53
This paper presents a full-CMOS transmitter and receiver for 2.0-GHz wide-band code division multiple access with direct conversion mixers and a DC-offset cancellation scheme. The direct conversion scheme combined with a multiphase sampling fractional-N prescaler alleviates the problems of the direct conversion transmitter and receiver. Digital gain control is merged into the baseband filters and variable-gain amplifiers to optimize the linearity of the system, reduce the noise, and improve the sensitivity. Variable-gain amplifiers with DC-offset cancellation loop eliminate the DC-offset in each stage. The chip implemented in 0.35-/spl mu/m CMOS technology shows the experimental results of 6 dBm maximum output power with 38-dB adjacent channel power rejection ratio at 1.92 MHz, 50-dB dynamic range, and 363-mW power consumption in the transmitter. The receiver shows -115.4 dBm sensitivity, a 4.0-dB noise figure, and a dynamic range of 80-dB with 396-mW power consumption. 相似文献