Bell Layered Space-Time Architecture (BLAST) is a multi-antenna communication structure with high spectrum efficiency, and it has found wide applications in LANs and WANs. However, since it does not make full use of t...
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ISBN:
(纸本)0780386477
Bell Layered Space-Time Architecture (BLAST) is a multi-antenna communication structure with high spectrum efficiency, and it has found wide applications in LANs and WANs. However, since it does not make full use of the diversity provided by multiple antennas its performance is much poor than other Space-Time Coding approaches. In this paper, a new application of DS-CDMA in BLAST is proposed, The new system introduces Orthogonal Spreading Sequences (OSS) into the transmitter while retains the basic structure of BLAST. The proposed receiver suppresses interferences from other antennas by the orthogonality contained in the received signals, and extracts information from each receive antenna using RAKE receiving principle to construct efficient statistic decision. Simulation results show that the proposed system achieves good performance over flat fading channels at the cost of a little loss in spreading spectrum.
This paper proposes multiple-input multiple-output (MIMO) communication systems employing different differential mapping per transmit antenna, i.e., per transmit antenna differential mapping (PADM) and its demodulatio...
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ISBN:
(纸本)0780382552
This paper proposes multiple-input multiple-output (MIMO) communication systems employing different differential mapping per transmit antenna, i.e., per transmit antenna differential mapping (PADM) and its demodulation by means of per-survivor processing (PSP). The features of PADM are as follows: 1) it can be applied to both transmit diversity (TD) and space multiplexing (SM);2) it can be applied to multiple-input single-output (MISO) as well as MIMO;3) it can perform maximum-likelihood detection without channel state information (CSI) by means of finite-state PSP. First, this paper evaluates PSP based on the MP pseudo inverse matrix, and proposes a mapping scheme for PADM according to the evaluated results. Next, this paper shows configuration of TD and SM. Finally computer simulation confirms that the proposed PADM has excellent performance in the case of TD and SM.
The spatial correlation features of channel impulse responses for an indoor environment are presented. The wide-hand impulse responses of a rectangular enclosure are calculated using the method of images. Bandpass rep...
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ISBN:
(纸本)0780383443
The spatial correlation features of channel impulse responses for an indoor environment are presented. The wide-hand impulse responses of a rectangular enclosure are calculated using the method of images. Bandpass representations of the non line-of-sight multipath responses are obtained for 2.4 GHz ISM band and their spatial cross correlation estimated for various positions of the transmitter and receiver arrays. The receiver and transmitter correlations are shown to exhibit periodic features and a spatial dependence in the decay rate. The correlation minima decreases with transmitter-receiver (T-R) separation and peak-to-peak correlation amplitude exhibits larger values when the transmitter and receivers are positioned close to the corners of the room. The oscillatory features in the spatial correlation may he attributed to the distribution of multipath clusters in time. For certain configurations of the T-R arrays the clusters are well separated resulting in a slower rate of oscillation at the inter-cluster time scale. In the short or intra-cluster time-scale, the correlation can exhibit a slow decay rate. At the corners, these clusters appear at faster rate and individual clusters are of a shorter duration. This feature leads to a faster and more structured oscillation in the correlation features. These observations are important considerations in design and evaluation of the performance of multiple-outputmultiple-input wireless communications systems.
The impact of interference on multiple-input multiple-output (MIMO) systems has recently attracted interest. Most studies of channel estimation and data detection for MIMO systems consider spatially and temporally whi...
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The impact of interference on multiple-input multiple-output (MIMO) systems has recently attracted interest. Most studies of channel estimation and data detection for MIMO systems consider spatially and temporally white interference at the receiver. In this paper, we address channel estimation, interference correlation estimation, and data detection for MIMO systems under both spatially and temporally colored interference. We examine the case of one dominant interferer in which the data rate of the desired user could be the same as or a multiple of that of the interferer. Assuming known temporal interference correlation as a benchmark, we derive maximum likelihood (ML) estimates of the channel matrix and spatial interference correlation matrix, and apply these estimates to a generalized version of the Bell Labs Layered Space-Time (BLAST) ordered data detection algorithm. We then investigate the performance loss by not exploiting interference correlation. For a (5,5) MIMO system undergoing independent Rayleigh fading, we observe that exploiting both spatial and temporal interference correlation in channel estimation and data detection results in potential gains of 1.5 dB and 4 dB for an interferer operating at the same data rate and at half the data rate, respectively. Ignoring temporal correlation, it is found that spatial correlation accounts for about I dB of this gain.
The application of various space-time block coding (STBC) schemes in DS-CDMA systems is considered. In particular, the bit-error-rate (BER) performance of orthogonal, quasiorthogonal, and linear dispersion codes in nu...
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ISBN:
(纸本)7505350668
The application of various space-time block coding (STBC) schemes in DS-CDMA systems is considered. In particular, the bit-error-rate (BER) performance of orthogonal, quasiorthogonal, and linear dispersion codes in number of system configurations is compared. Simulation results show that significant improvements in the BER performance can be achieved by integrating STBC into DS-CDMA systems. These performance improvements are found to be related to the diversity order offered by a given STBC scheme, the order of a modulation scheme, and type of the receiver.
We measure the capacity of multiple-input multiple-output radio systems in microcellular environments. We use a new data evaluation method that allows to evaluate the cumulative distribution function of the capacity f...
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We measure the capacity of multiple-input multiple-output radio systems in microcellular environments. We use a new data evaluation method that allows to evaluate the cumulative distribution function of the capacity from a single measurement. This method is based on an extraction of the parameters of the multipath components and, thereafter, a synthetic variation of their phases. In the analyzed environments, we find capacities to be about 30% smaller than would be anticipated from an idealized model. In addition, the frequency selectivity of the channel makes the cdf of the capacity steeper and, thus, increases the outage capacity, compared with the frequency-flat case, but the influence on the mean capacity is small.
Multielement system capacities are usually thought of as limited only by correlations between elements. It is shown here that degenerate channel phenomena called "keyholes" may arise under realistic assumpti...
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Multielement system capacities are usually thought of as limited only by correlations between elements. It is shown here that degenerate channel phenomena called "keyholes" may arise under realistic assumptions which have zero correlation between the entries of the channel matrix H and yet only a single degree of freedom. Canonical physical examples of keyholes are presented. For outdoor environments, it is shown that roof edge diffraction is perceived as a "keyhole" by a vertical base array that may be avoided by employing instead a horizontal base array.
In this paper we present a deterministic approach of modeling wideband MIMO (multiple-input multiple-output) radio fading channel for wireless multicarrier systems. Implementation problem of downlink MIMO model for mo...
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ISBN:
(纸本)0819447005
In this paper we present a deterministic approach of modeling wideband MIMO (multiple-input multiple-output) radio fading channel for wireless multicarrier systems. Implementation problem of downlink MIMO model for mobile station (MS) was first investigated, while space-time coding or downlink beam-forming is taken into count at base station (BS). The MIMO channel are determined by both power azimuth profile (PAP) at MS and various configuration of multiple antennas at BS. Based on tap-delay-line structure and deterministic fading channel modeling method, SIMO fading model, corresponding to any one transmitter antenna, is formed by generating doppler phase difference between two receiver antenna aided by PAP at MS. The von Mises probability density function was adopted to characterize phenomenon of nonisotropic scattering components around MS. The ultimate MIMO channel simulation model is sum of all SIMO channel with all transmitter antennas. Finally, we predicted MIMO channel capacity based on proposed simulation model with parameters of wireless multicarrier systems under specified "Vehicular A channel" of ITU-R M.1225.
Control system synthesis consists of two major subtasks: selection of measurements and manipulated variables, and deciding on the structure interconnecting the measured and manipulated variables along with the control...
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Control system synthesis consists of two major subtasks: selection of measurements and manipulated variables, and deciding on the structure interconnecting the measured and manipulated variables along with the control law governing the interconnections. For multiple-input-mutiple-output systems, a decentralized control structure is generally preferred to a fully centralized structure. A major step in this controller design process is therefore the pairing problem: which manipulated variables to connect to which measurements? The answer to this question has undoubtedly to account for loop interactions that arise within the system. Work has been carried out using Relative Gain Array (RGA) and Block Relative Gain (BRG) interaction measures to develop automated pairing procedures and implement them as a portable software. A methodology involving the use of this software in conjuction with dynamic simulation and Internal Model Control design techniques for controllers was used on a particular case study to generate a satisfactory control structure.
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