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In a "Massive MIMO" context, we evaluate low-complexity iterative DF detection techniques involving interference cancellation at the output of an MF multiuser detector. These techniques can offer some performance advantage over the somewhat more complex (due to matrix inversion requirements) linear, ideal MMSE detection. Moreover, we can achieve close approximations to appropriate performance bounds - which are able to take into account channel estimation imperfections -, even for NR/NT <10, when NR/NT is also high enough to ensure iterative DF convergence.

“© © 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

© © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

“© © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

This paper deals with Single Carrier/Frequency Domain Equalization (SC/FDE) for uplink transmission within a Multi-User (MU) Multi-Input Multi-Output (MIMO) system where the number of Base Station (BS) antennas can be much larger than the number of transmitter antennas jointly using the same time/frequency resource at Mobile Terminals (MT). Selected Quadrature Amplitude Modulation (QAM) schemes are assumed for transmission, so that high bandwidth efficiencies are achievable. In this context, we consider either a linear detection or a reduced-complexity, iterative Decision Feedback (DF) detection, evaluate the achievable performances in both cases, and discuss them with the help of selected performance bounds and semi-analytically evaluated error floor levels. From our performance results, we conclude that simple linear detection techniques, designed to avoid the need of complex matrix inversions, can lead to unacceptably high error floor levels. However, by combining the use of such simple linear detectors with the appropriate interference cancellation procedure - within the iterative DF technique -, a close approximation to the Single-Input Multi-Output (SIMO) Matched-Filter Bound (MFB) can be achieved after a few iterations, even for 64-QAM schemes, when the number of BS antennas is five times higher than the number of antennas jointly used at the user terminals.

“© © 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

This paper deals with Turbo Frequency-Domain Equalization (FDE) for Single Carrier (SC)-based block transmission, under full-Cyclic Prefix (CP) conditions. As in recent papers of the authors, the Turbo FDE technique considered here involve a linear FDE scheme and a soft cancellation of residual Inter-Symbol Interference (ISI). The contribution of Soft-In SoftOut (SISO) decoding for Turbo FDE performance is evaluated in detail,forclassesofconvolutionalcodingschemeswhichinvolvea rangeofcoderates(from R = 1 2 to R = 1)andconstraintlengths (from 2 to 16 states, in the R = 1 2 case). This evaluation includes a discussion on using either the ”extrinsic” or the ”full” SISO decoder’s information as an ”a priori” input to the frequencydomain equalizer, with appropriate comparisons. It also includes the comparison of achievable performances with easily computed matched-filter bounds, namely for R = 1 (the uncoded Bit Error Rate (BER) performance case). The main conclusion is that the advantage of using the full SISO decoder’s information increases with an increased code rate, obtained by code puncturing, or a reduced number of states for a given code rate. Using the full SISO decoder’s information, for soft ISI cancellation in Turbo FDE schemes, is always an appropriate choice. Moreover, in all cases, this choice provides close approximations to the matchedfilter bound performance after a few iterations.

In this paper, we consider two reducedPMEPR (Peak to Mean Envelope Power Ratio) CPassisted (Cyclic Prefix) block transmission alternatives, having in mind an application to the uplink of future mobile broadband systems: clipped (and filtered) OFDM (Orthogonal Frequency Division Multiplexing) and SC/FDE (Single Carrier/Frequency-Domain Equalization). In both cases, we adopt advanced receivers with space diversity and a similar structure, where an iterative cancellation of unavoidable interferences is carried out: deliberate nonlinear interference, in the Clipped-OFDM case; residual linear ISI, in the SC/FDE case. Performance results are reported and discussed, with the help of selected performance bounds, thereby providing relevant ”SC vs OFDM” comparisons. A clear advantage for the SC/FDE side is shown to exist when a 4-QAM (Quadrature Amplitude Modulation) constellation is selected in both cases. When the constellation size is increased, the SC/FDE advantage decreases, namely when the clipping effort is strong enough to reduce the OFDM PMEPR to a level below that of the corresponding SC/FDE scheme.

This paper deals with an Orthogonal Frequency Division Multiplexing (OFDM)-based uplink within a Multi User (MU)-Multi-Input Multi-Output (MIMO) system where a ”massive MIMO” approach” is adopted. In this context, either an optimum Minimum Mean-Squared Error (MMSE) linear detection or a reduced-complexity Matched Filter (MF) linear detection are considered. Regarding performance evaluation by simulation, several semi-analytical methods are proposed: one performance evaluation method in the optimum (MMSE) case; two performance evaluation methods in the MF case. This paper includes performance results for uncoded 4-Quadrature Amplitude Modulation (QAM)/OFDM transmission and a MUMIMO channel with uncorrelated Rayleigh fading, under the assumptions of perfect power control and perfect channel estimation. The accuracy of performance results obtained through the semi-analytical simulation methods is assessed by means of parallel conventional Monte Carlo simulations [10]. The performance resultsare discussed indetail andwe also emphasize the achievable ”massive MIMO” effects, even for the reducedcomplexity detection techniques, provided that the number of BS antennas is much higher than the number of antennas which are jointly employed in the terminals of the multiple autonomous users.

© © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

This paper deals with Single Carrier (SC)/Frequency Domain Equalization (FDE) as an uplink alternative to Orthogonal Frequency Division Multiplexing (OFDM) for a Multi User (MU)-Multi-Input Multi-Output (MIMO) system where a ”massive MIMO” approach is adopted. In this context, either an optimum Minimum Mean-Squared Error (MMSE) linear detector or appropriate reduced-complexity linear detection techniques are considered. Regarding performance evaluation by simulation, two semi-analytical methods are proposed - one method in the optimum (MMSE) case and the other one in the reduced-complexity cases. This paper includes performance results for uncoded 4 Quadrature Amplitude Modulation (QAM) SC/FDE transmission and a MU-MIMO channel with uncorrelated Rayleigh fading, under the assumptions of perfect power control and perfect channel estimation.The accuracy of performance results obtained through the semi-analytical simulation methods is assessed by means of parallel conventional Monte Carlo simulations. The performance results are discussed in detail and we also emphasize the achievable ”massive MIMO” effects, even for the reduced complexity detection techniques, provided that the number of BS antennas is much higher than the number of antennas which are jointly employed in the terminals of the multiple autonomous users. Appropriate ”SC/FDE vs OFDM” comparisons are also included in this discussion of performance results.

“© © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

Users are increasingly demanding about the quality and consumer batteries of their mobile terminals to gain access to services imposed by operators. In order to satisfy the customers, operators must provide a good quality, high transmission rates to allow videoconferencing communications and low power consumption in mobile terminals, so that battery last longer. In mobile communications, data are transmitted over a channel that is affected by noise, thus affecting the quality of data received, and thus can degrade the received information. In traditional communications, SISO (Single-Input Single-Output systems) with one transmitting and one receiving antenna, are not efficient to minimize noise caused by the channel. Solutions such as increased bandwidth and increased power transmission would solve the problem, however, are not reliable. Although these solutions are valid in theory, none of them is put into practice, because increasing the transmission of mobile terminals, there would cause an increase in battery size, price and increasing the size of mobile terminals and the fact that it could be detrimental to our health. Increasing the bandwidth would be an easy way out and solve the problems of errors and low transmission rates, however there is a price to pay, the spectrum allocation is expensive, so this technique is not feasible. This paper aims to provide efficient solutions to improve the efficiency of power, namely to achieve a good quality with a low power consumption on the handset. The spectral efficiency is improved through the implementation of MIMO (Multi-Input Multi-Output) systems, i.e., multiple transmit antennas and multiple receiving antennas, using error correction codes. Through the union of these two techniques is possible to obtain a low error probability with low power consumption. This paper presents how MIMO solution the STBC (Space Time Block Codes) encoding. The Alamouti code [1] is used in this coding, which consists of data transmission with two transmit antennas and one or more receiving antennas. Other STBC codes for multiple antennas and multiple receiving antennas are presented in the paper, these codes developed by Tarokh et al [2]. The novelty of this study, presented here, is the use of MIMO systems using error correction codes (Turbo-codes[3]). In the turbo code decoding algorithms are used with soft outputs, as the MAP (Maximum a Posteriori) algorithm, Log-MAP and max-log-MAP. The error probability performance results, presented in this paper were obtained by Matlab Simulations with 4-QAM modulation in Rayleigh channel. The SISO systems are compared with MIMO systems with and without error correction. The simulation results show that there is a significant improvement when the MIMO systems are used compared to the SISO systems, and that with error correction lower error probability is achieved with lower energy consumption.

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“© © 2005 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

This paper aims to provide efficient solutions to improve the power efficiency, like implementation of schemes using MIMO (Multiple-Input Multiple-Output), with error correction codes. Thanks to the union of these two techniques is possible to obtain a low error probability with low power consumption. This paper shows STBC (Space Time Block Codes) with codes and diversity in the reception using a MRC (Maximum Ratio Combining). In this solution are studied Alamouti codes [1] and those proposed by Tarokh et al [2], with four and eight transmit antennas. Turbo Codes are used in the decoding algorithm with soft output, the log-MAP. The simulation results of the performance of error probability (BER) are performed in MATLAB with 4-QAM modulation in a Rayleigh channel.

For conventional cyclic prefix (CP)-assisted single-carrier/frequency-domain equalization (SC/FDE) implementations, as well as for orthogonal frequency-division multiplexing (OFDM) implementations, the CP length is known to be selected on the basis of the expected maximum delay spread. Next, the data block size can be chosen to be large enough to minimize the CP overhead, yet small enough to make the channel variation over the block negligible. This paper considers the possibility of reducing the overall CP assistance, when transmitting sequences of SC blocks, while avoiding an excessively long fast Fourier transform window for FDE purposes and keeping good FDE performances through low-complexity, noniterative receiver techniques. These techniques, which take advantage of specially designed frame structures, rely on a basic algorithm for decision-directed correction (DDC) of the FDE inputs when the CP is not long enough to cope with the time-dispersive channel effects. More specifically, we present and evaluate a novel class of reduced-CP SC/FDE schemes, which takes advantage of a special frame structure for replacing "useless" CP redundancy by fully useful channel coding redundancy, with the help of the DDC algorithm. When using the DDC-FDE technique with these especially designed frame structures, the impact of previous decisions, which are not error-free, is shown to be rather small, thereby allowing a power-efficiency advantage (in addition to the obvious bandwidth-efficiency advantage) over conventional block transmission implementations under full-length CP. Additionally, the DDC algorithm is also shown to be useful to improve the power efficiency of these conventional implementations.

For conventional cyclic-prefix (CP)-assisted block transmission systems, the CP length is selected on the basis of the expected maximum delay spread. With regard to single-carrier (SC)-based block transmission implementations, a full-length CP is recommendable, since it allows good performances through the use of simple frequency-domain equalization (FDE) techniques. In this letter, a soft-decision-directed correction (SDDC)-aided turbo FDE technique is presented for reduced-CP SC-based block transmission systems using conventional frame structures. The relations with some already known iterative FDE techniques are established, and a set of performance results is reported and discussed. The advantages of the proposed approach are emphasized, namely, the possibility of approximately achieving (besides the obvious bandwidth efficiency gain) the maximum power efficiency gain that a strong CP reduction allows.

info:eu-repo/semantics/publishedVersion

“© © 2006 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

For conventional CP-assisted (Cyclic Prefix) SC/FDE implementations (Single- Carrier/Frequency Domain Equalisation), as well as for OFDM implementations (Orthogonal Frequency Division Multiplexing), the CP length is known to be selected on the basis of the expected maximum delay spread. Next, the data block size can be chosen to be large enough to minimise the CP overhead, yet small enough to make the channel variation over the block negligible. This paper considers the possibility of reducing the overall CP assistance, when transmitting sequences of SC blocks, while avoiding an excessively long FFT block for FDE purposes and keeping good performances through a moderate increase of the FDE receiver complexity. Firstly, we present an algorithm for a Decision-Directed Correction (DDC) of the FDE inputs when the CP is not long enough to cope with the time-dispersive channel effects. Next, we present and evaluate a novel class of reduced CP SC/FDE schemes, which takes advantage of the DDC algorithm for replacing ”useless” CP redundancy by fully useful channel coding redundancy. A very efficient block transmission, especially for both strongly time-dispersive and time-varying channel conditions, is then achieved.

“© © 2006 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”

This paper deals with CP-assisted block transmissionsolutionsforfuturemobilebroadbandsystems,inthecontext of a Single Carrier (SC)-Frequency Division Multiple Access (FDMA)uplink.Twoalternativechoicesareconsideredregarding the subcarrier mapping rule: a ”localized” subcarrier mapping where user’s data occupy a set of consecutive sub carriers (Rule 1); a ”distributed” subcarrier mapping where user’s data occupy a set of uniformly spaced subcarriers (Rule 2). Detailed performance evaluations, in this paper, involve the consideration of two iterative receiver techniques which can be regarded as extensions of iterative receiver techniques proposed previously within a single user context. A selected class of multipath radio channels, providing a range of channel time dispersion levels, is assumed for performance evaluation purposes,andasetofmatchedfilterboundsonreceiverperformance plays a relevant role in ”achievable performance” comparisons. Both the impact of the mapping rules and that of the iterative receiver techniques considered here are evaluated in detail. The performance advantages under ”Rule 2” are emphasized, for practically the entire range of the channel time dispersion levels assumed in the paper and both specific iterative receiver techniques.