Metrics obtained from a set of channel measurement data are used to predict performance of different MIMO techniques, such as spatial multiplexing and space-time block coding. For a given channel realisation, metries ...
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ISBN:
(纸本)9781424400379
Metrics obtained from a set of channel measurement data are used to predict performance of different MIMO techniques, such as spatial multiplexing and space-time block coding. For a given channel realisation, metries such as mutual information, eigenvalues, etc. can be extracted and the BER performance simulated for different MIMO techniques. By correlating the simulated BER performances to the metrics, it can be determined which metrics are useful BER performance predictors for a given MIMO technique. It is shown that mutual information and the eigenvalues of the spatial correlation matrix are useful BER predictors for V-BLAST and STBC techniques.
This paper presents a family of rate-one quasi-orthogonal space-time block codes (QO-STBCs) for any number of transmit antennas. Full diversity of the proposed QO-STBCs is achieved via the use of constellation rotatio...
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This paper presents a family of rate-one quasi-orthogonal space-time block codes (QO-STBCs) for any number of transmit antennas. Full diversity of the proposed QO-STBCs is achieved via the use of constellation rotation. When the number of transmit antennas is even, these codes are delay "optimal." this property along with the quasi-orthogonality one allows the codes to have low decoding complexity. Besides, by applying lookup tables into the detection methods presented in [1] and generalizing them, two low-complexity maximum-likelihood (ML) decoders for the proposed QO-STBCs and for other existing QO-STBCs, called PMLD and QMLD, are obtained. Simulation results are provided to verify the bit error rate (BER) performances and complexities of both the proposed QOSTBCs and the proposed decoders.
A theory for jointly optimizing transmitter and receiver finite impulse response (FIR) multiple-input multiple-output (MIMO) filters is developed in the presence of near-end crosstalk and additive channel noise indepe...
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A theory for jointly optimizing transmitter and receiver finite impulse response (FIR) multiple-input multiple-output (MIMO) filters is developed in the presence of near-end crosstalk and additive channel noise independent of the original signal. The transfer function of the channel is a known MIMO transfer function with finite memory. Near-end crosstalk is included through another MIMO transfer function. The channel input signal is assumed to be power constrained. For a given channel with a maximum allowable average input power, the transmitter and receiver FIR MIMO filters are jointly optimized such that the mean square error (MSE) between the desired and reconstructed signal is minimized. An iterative numerical optimization algorithm is proposed. When compared to the methods available in the literature, the proposed method yields better results due to the joint optimization of the transmitter-receiver pair and is applicable to a more general scenario that may include correlated sources and near-end crosstalk.
We present a general framework to quantify the data throughput capabilities of a wireless communication system when it combines: 1) multiple transmit signals;2) adaptive modulation for each signal;and 3) adaptive arra...
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We present a general framework to quantify the data throughput capabilities of a wireless communication system when it combines: 1) multiple transmit signals;2) adaptive modulation for each signal;and 3) adaptive array processing at the receiver. We assume a noise-limited environment, corresponding to either an isolated cell or a multicell system whose out-of-cell interference is small compared with the thermal noise. We focus on the user data throughput, in bits per second/Hertz (bps/Hz), and its average over multipath fading, which we call the user spectral efficiency. First, an analysis method is developed to find the probability distribution and mean value of the spectral efficiency over the user positions and shadow fadings, both as. a function of user distance from its serving base station and averaged over the cell coverage area. We assume fading conditions and receiver processing that lend themselves to closed-form analysis. The resulting formulas are simple and straightforward to compute, and they provide a number of valuable insights. Next, we run Monte Carlo simulations, both to confirm the analysis and to treat cases less amenable to simple analysis. A key contribution of this paper is a simple formula for the mean spectral efficiency in terms of the propagation exponent, mean signal-to-noise ratio at the cell boundary, number of antennas, and type of coding. Under typical propagation conditions, the mean spectral efficiency using three transmit and three receive antennas ranges from 19.2 bps/Hz (uncoded) to 26.8 bps/Hz (ideally coded), highlighting the potential benefits of multiple transmissions combined with adaptive techniques. This is much higher than the spectral efficiencies for a link using a single transmitter and a threefold receive diversity under the same conditions, where the range is from 8.77 bps/Hz to 11.4 bps/Hz. Moreover, the latter results are not nearly as practical to achieve, as they call for large signal constellations that would b
Orthogonal space-time block codes (STBCs) [1], [2] appear to be a very fascinating means of enhancing reception quality in quasistatic MIMO channels due to their full diversity, and especially their simple maximum-lik...
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Orthogonal space-time block codes (STBCs) [1], [2] appear to be a very fascinating means of enhancing reception quality in quasistatic MIMO channels due to their full diversity, and especially their simple maximum-likelihood (ML) decoders. However, full-rate full-diversity orthogonal STBCs do not exist for more than two transmit antennas. Vertical layered space-time architecture (so-called the V-BLAST) [3] with a nulling- and cancelling-based detection algorithm, in contrast, has an ability of achieving high transmission rates at the cost of having very low diversity gain, an undesirable consequence caused by the interference nulling and cancelling processes. The uncoded V-BLAST system is able to reach its ML performance with the aid of the sphere decoder algorithm [4] at the expense of higher detection complexity. Undoubtedly, the tradeoff between transmission rates, diversity, and complexity is inherent in designing space-time codes. This paper investigates a method to increase the "nulling diversity gains" for a general high-rate space-time code and introduces a new design strategy for high-rate space-time codes detected based on interference nulling and cancelling processes, thanks to which high-rate quasi-orthogonal space-time codes for MIMO applications are proposed. We show that when n(T) transmit and n(R) = n(T) receive antennas are deployed, the first code offers a transmission rate of (n(T) - 1) with a minimum nulling diversity order of 3, whereas the second one offers a transmission rate of (n(T) - 2) with a minimum nulling diversity order of 5. Therefore, the proposed codes significantly outperform the V-BLAST as n(R) = n(T). Simulation results and discussions on the performance of the proposed codes are provided.
A broadband multiple-input multiple-output (MIMO) OFDM system has been designed and evaluated for a fixed wireless link between tall buildings in an urban area. Channel measurements for a typical installation location...
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A broadband multiple-input multiple-output (MIMO) OFDM system has been designed and evaluated for a fixed wireless link between tall buildings in an urban area. Channel measurements for a typical installation location are analysed to determine the relevant spatial, temporal and frequency characteristics. The small number of multipath components leads to a high spatial correlation and limited potential for spatial diversity to provide spectral efficiency gains. However, the slowly-varying characteristics support the use of a closed-loop diversity scheme, such as spatial multiplexing along the eigenmodes of the channel matrix, to maximise the achievable throughput. This scheme is evaluated using the measured channel data, and it is shown that the self-interference caused by channel estimation errors is the limiting factor on the system performance. Taking into account the estimation errors and feedback delay, it is demonstrated that a three-fold increase in spectral efficiency relative to a single-element antenna system is achievable using eight-element antennas, even in this highly correlated environment.
This letter proposes two very-low-complexity maximum-likelihood (ML) detection algorithms based on QR decomposition for the quasi-orthogonal space-time code (QSTBC) with four transmit antennas [3]-[5], called VLCMLDec...
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This letter proposes two very-low-complexity maximum-likelihood (ML) detection algorithms based on QR decomposition for the quasi-orthogonal space-time code (QSTBC) with four transmit antennas [3]-[5], called VLCMLDec1 and VLCMLDec2 decoders. The first decoder, VLCMLDec1, can be used to detect transmitted symbols being extracted from finite-size constellations such as phase-shift keying (PSK) or quadrature amplitude modulation (QAM). The second decoder, VLCMLDec2, is an enhanced version of the VLCMLDec1, developed mainly for QAM constellations. Simulation results show that both of the proposed decoders enable the QSTBC to achieve ML performance with significant reduction in computational load.
This paper deals with several aspects relative to the multiple-input multiple-output (MIMO) propagation channel. Different approaches used to model the MIMO channel are first presented. Then, the different measurement...
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ISBN:
(纸本)296005511X
This paper deals with several aspects relative to the multiple-input multiple-output (MIMO) propagation channel. Different approaches used to model the MIMO channel are first presented. Then, the different measurement techniques used in order to characterize the propagation channel are described. Measurement campaigns made in urban environments have been analyzed to obtain the relevant statistical parameters of the channel. These results make it possible to discuss the integration of MIMO techniques in practical wireless communication systems.
In this paper, a transmit diversity scheme based on space-time spreading for code-division multiple-access (CDMA) systems in fast-fading channels is introduced. The proposed transmit diversity scheme employs orthogona...
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ISBN:
(纸本)0780393058
In this paper, a transmit diversity scheme based on space-time spreading for code-division multiple-access (CDMA) systems in fast-fading channels is introduced. The proposed transmit diversity scheme employs orthogonal Walsh spreading codes to exploit the time diversity introduced by the channel, and hence achieves two-fold of the diversity order obtained using conventional space-time spreading schemes. A generalization of the proposed coding scheme to systems with different antenna configurations is also discussed. For slowly-fading channels, we show that the proposed transmit diversity scheme reduces to that of conventional transmit diversity schemes with no performance degradation. For nonorthogonal spreading codes, we propose a receiver structure that employs an interference cancellation scheme to compensate for signal interference. Our results show a large performance improvement when using such an interference cancellation scheme relative to the conventional matched filter receiver.
Space-Time Block Codes(STBCs) are designed to obtain the full diversity gain. However, STBCs are not designed to achieve an additional coding gain. Therefore, STBCs need to be concatenated with an outer code which pro...
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ISBN:
(纸本)078039335X
Space-Time Block Codes(STBCs) are designed to obtain the full diversity gain. However, STBCs are not designed to achieve an additional coding gain. Therefore, STBCs need to be concatenated with an outer code which provides a significant coding gain. Turbo Product Codes (TPCs) are a kind of high-efficient coding scheme with low latency decoding, which do not suffer from an error floor associated with turbo codes. This article considers the concatenation of TPCs with STBCs and sets up coded MIMO-OFDM syatem to improve the reliability of the wireless communication systems. Finally, the paper presents simulating environment of experiment testing.
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