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ABSTRACT: In this work we propose novel decision feedback (DF) detection algorithms
with error propagation mitigation capabilities for multi-input multi-output
(MIMO) spatial multiplexing systems based on multiple processing branches. The
novel strategies for detection exploit different patterns, orderings and
constraints for the design of the feedforward and feedback filters. We present
constrained minimum mean-squared error (MMSE) filters designed with constraints
on the shape and magnitude of the feedback filters for the multi-branch MIMO
receivers and show that the proposed MMSE design does not require a significant
additional complexity over the single-branch MMSE design. The proposed
multi-branch MMSE DF detectors are compared with several existing detectors and
are shown to achieve a performance close to the optimal maximum likelihood
detector while requiring significantly lower complexity.
04/2013;
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ABSTRACT: This letter studies data rate fairness on the two-way relay channel. It analytically determines the optimal power values at both nodes and at the relay, that lead to a maximization of the sum rate under the fairness constraint. Amplify-and-Forward (AF) and Decode-and-Forward (DF) relaying protocols are considered. For AF, the optimization problem is turned into a single-variable convex optimization problem. For DF, rate balancing between Multiple Access and broadcast phases must be performed prior to setting nodes powers. Both optimized protocols are compared with reference AF and DF in terms of data rates through numerical simulations.
IEEE Communications Letters 10/2011; · 0.98 Impact Factor
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ABSTRACT: This paper provides a theoretical performance evaluation of the downlink of asynchronous orthogonal frequency division multiplexing (OFDM) and filter bank based multicarrier (FBMC) cellular radio communication systems. An accurate derivation, for the interference caused by the timing synchronization errors in the neighboring cells, is developed. The multipath effects on the interfering and desired signal are also considered. Based on computing the moment generating functions of the interference power, exact expressions are derived for average error rates of OFDM and FBMC systems considering the frequency correlation fading in the case of block subcarrier assignment scheme.
IEEE Transactions on Wireless Communications 09/2011; · 2.59 Impact Factor
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ABSTRACT: Interference at the radio receiver is a key source of degradation in quality of service of wireless communication systems. In this paper, we address the impact of imperfect inter-cell synchronization on the performance of orthogonal frequency division multiplexing (OFDM) and filter bank based multicarrier (FBMC) multi-cellular networks. Based on computing the moment generating functions of the asynchronous interference power, a useful analytical method for computing the average error rates is derived considering the frequency correlation fading between adjacent interfering subcarriers.
Communications (ICC), 2011 IEEE International Conference on; 07/2011
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ABSTRACT: In this paper, we propose transmit processing techniques based on novel switched interleaving, chipwise linear precoding, and limited feedback for both downlink and uplink multicarrier code-division multiple access (MC-CDMA) multiple-antenna systems. We develop transceiver structures with switched interleaving, linear precoding, and detectors for both uplink and downlink using limited-feedback techniques. In the proposed schemes, a set of possible chip interleavers is constructed and prestored at both the base station (BS) and mobile stations (MSs). For the downlink, a new hybrid transmit processing technique based on switched interleaving and chipwise precoding is proposed to suppress the multiuser interference. The BS and MSs are also equipped with another codebook of quantized downlink channel-state information (CSI). Each MS quantizes its own downlink CSI and feeds the index back to the BS through a low-rate feedback channel. Then, the selection function at the BS determines the optimum interleaver based on the CSI of all users. Moreover, a transmit processing technique for the uplink of multiple-antenna MC-CDMA systems, which requires a very low rate of feedback information, is also proposed. Codebook design methods for both interleavers and quantized CSI are also proposed. Simulation results show that the performance of the proposed techniques is significantly better than prior art.
IEEE Transactions on Vehicular Technology 06/2011; · 1.92 Impact Factor
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ABSTRACT: In this paper, we analyze the performance of cooperative diversity using adaptive Decode and Forward (DF) relaying over independent non identical flat composite fading channels which include multipath fading and shadowing simultaneously. We have considered the generalized-K model which is very versatile and accurately approximates many of the commonly used channel models as Nakagami-m, log-normal distribution and the mixture of the two distributions for the composite fading. We give an analytical expression for the symbol error probability of the proposed scenario and analyze its dependence on the channel parameters. We assume in our context, that the relay decides independently whether or not to forward the signal to the destination based on the received signal quality. Simulation results are in good agreement with our theoretical analysis.
Signal Processing and Information Technology (ISSPIT), 2010 IEEE International Symposium on; 01/2011
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ABSTRACT: This paper addresses the effect of timing synchronization errors for two different multicarrier techniques CPOFDM and FBMC. Such errors degrade the performance of the reference receiver by causing multi user interference. This interference occurs when the signals from different transmitters arrive at a given receiver with arbitrary timing misalignments, leading to the destruction of orthogonality between subcarriers. In this paper, we propose a model of interference that provides a useful computational tool in order to analyze the performance of an OFDM/FBMC receiver in frequency selective fading environment. Finally, simulation results confirmed the accuracy of the proposed model.
Personal Indoor and Mobile Radio Communications (PIMRC), 2010 IEEE 21st International Symposium on; 10/2010
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ABSTRACT: Multi-carrier modulation and especially CP-OFDM is widely used nowadays in several radio communications. However, FBMC is a potential alternative to CP-OFDM since it does not require cyclic prefix, and thus, it has a higher spectral efficiency. One of the characteristics of FBMC is that the received data are accompanied by a two dimensional inter-symbol interference term (2D ISI), which complicates MIMO techniques when combined with optimum detection. In this paper we consider the association of FBMC with the multiple-input multiple-output (MIMO) technique focusing on the spatial data multiplexing (SDM), and we investigate the use of Maximum Likelihood (ML) detection. We propose modified FBMC schemes based on inserting null data among QAM symbols to reduce, in this way, the overlapping of the symbols.
Personal Indoor and Mobile Radio Communications (PIMRC), 2010 IEEE 21st International Symposium on; 10/2010
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ABSTRACT: FBMC transmission system was proposed as an alternative approach to OFDM system since it has a higher spectral efficiency. One of the characteristics of FBMC is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time and frequency domain. The presence of this interference is an issue for the Maximum Likelihood (ML) implementation when we consider a Spatial Multiplexing MIMO system. In this paper, we will propose a new FBMC scheme and transmission strategy in order to avoid this interference term. This proposed scheme (called FFT-FBMC) transforms the FBMC system into an equivalent system as simple as OFDM. First, we will develop the FFT-FBMC in the case of SISO configuration, and then, we extend its application to Spatial Multiplexing MIMO configuration with Maximum Likelihood detection.
Wireless Communication Systems (ISWCS), 2010 7th International Symposium on; 10/2010
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ABSTRACT: In this paper, we focus on the channel capacity analysis of a Cognitive Radio (CR) network using two types of multicarrier communications: conventional Orthogonal Frequency Division Multiplexing (OFDM) with Cyclic Prefix (CP) and Filter Bank based Multi-Carrier (FBMC) modulations. We use a resource allocation algorithm in which subcarrier assignment and power allocation are carried out sequentially. By taking the impact of Inter-Cell Interference (ICI) resulting from timing offset into account, the maximization of total information rates is formulated, subject to maximum power constraint as well as interference constraint from Secondary User (SU) to Primary User (PU). Since the channel gain information between SU and PU can't be precisely estimated, the amount of the interference induced by SU to PU is calculated on the basis of an estimated Channel State Information (CSI), which is determined by a prescribed outage probability of primary systems. Simulation results show that FBMC can achieve higher channel capacity than OFDM, which indicates that FBMC is a potential candidate for physical layer data communication in CR context.
Cognitive Radio Oriented Wireless Networks & Communications (CROWNCOM), 2010 Proceedings of the Fifth International Conference on; 07/2010
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ABSTRACT: In FBMC transmission systems, the bit rate is maximized when OQAM modulation is employed. One of the characteristics of this modulation is that the received data symbols are accompanied by interference terms, which complicates the application of ML techniques in optimal decoders. Two approaches are proposed to cope with this situation. The first one exploits the MMSE estimation of the interference terms and it introduces no additional delay. In the second one, the interference terms are calculated from past, present and future data symbols, either already decided or estimated. The gains provided by these approaches, with respect to MMSE, are assessed and illustrated by simulation.
Wireless Conference (EW), 2010 European; 05/2010
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ABSTRACT: In this work, a new hybrid transmit processing technique based on switched interleaving and chip-wise precoding is proposed to suppress the multiuser interference (MUI) for downlink multi-carrier code division multiple access (MC-CDMA) multiple antenna systems. A set of possible chip-interleavers are constructed and prestored at both the base station (BS) and mobile stations (MSs), which are also equipped with another codebook of quantized downlink channel state information (CSI). Each MS quantizes its own downlink CSI and feeds back the index to the BS by a low-rate feedback channel, then the selection function at the BS determines the optimum interleaver based on all users' quantized CSIs to transmit signals. Simulation results show that the performance of the proposed techniques is significantly better than prior art.
Acoustics Speech and Signal Processing (ICASSP), 2010 IEEE International Conference on; 04/2010 · 4.63 Impact Factor
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ABSTRACT: In this work we propose novel decision feedback (DF) detection algorithms with error propagation mitigation capabilities for multi-input multi-output (MIMO) spatial multiplexing systems based on multiple processing branches. The novel strategies for detection exploit different patterns, orderings and constraints for the design of the feedforward and feedback filters. We present constrained minimum mean-squared error (MMSE) filters designed with constraints on the shape and magnitude of the feedback filters for the multi-branch MIMO receivers and show that the proposed MMSE design does not require a significant additional complexity over the single-branch MMSE design. The proposed multi-branch MMSE DF detectors are compared with several existing detectors and are shown to achieve a performance close to the optimal maximum likelihood detector while requiring significantly lower complexity.
Acoustics Speech and Signal Processing (ICASSP), 2010 IEEE International Conference on; 04/2010 · 4.63 Impact Factor
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ABSTRACT: Cognitive radio (CR) is proposed to improve frequency efficiency while avoiding interference with licensed users. In this paper, we adopt a resource allocation (RA) algorithm to perform uplink frequency allocation and power control between noncooperative multi-cell for CR network. The proposed RA algorithm is an extension of iterative water-filling algorithm (IWFA) applied to single-cell. The maximization of total information rates of multiple users in one cell is considered for Gaussian channel with pathloss, subject to power constraint on each user. By using multiple access channel (MAC) capacity region, the optimization problem is formulated as a decentralized game, in which each base station, trying to maximize the sum-rate of its own users, is a player, and Nash equilibrium (NE) can be achieved to guarantee global convergence. Our algorithm shows higher sum-rate than the traditional FDMA by sharing one and more subcarriers for different users. Final simulation results show that our algorithm can achieve more information rate than fixed channel allocation algorithm.
Wireless Communication Systems, 2009. ISWCS 2009. 6th International Symposium on; 10/2009
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ABSTRACT: Filter bank based multi-carrier (FBMC) is a multi-carrier modulation scheme that can be considered as an alternative to conventional OFDM with cyclic prefix (CP-OFDM) for transmission over multi-path fading channels. Compared to CP-OFDM, FBMC can provide a higher information bit rate, since it operates without the addition of a CP. Furthermore, FBMC enables the use of different pulse shapes therefore; it can provide better frequency localization than CP-OFDM. Since FBMC is based on real orthogonality, the association with MIMO techniques needs specific decoding schemes. In this paper we consider the combination of FBMC with a single delay space time trellis code (STTC). We propose an iterative decoding based on interference estimation and cancellation which does not require any channel coding or decoding block. We show that if we omit the CP loss of CP-OFDM and by using this FBMC decoding scheme we outperform CP-OFDM in single delay STTC context, this with only a slight increase in complexity.
Wireless Communication Systems, 2009. ISWCS 2009. 6th International Symposium on; 10/2009
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ABSTRACT: Multicarrier communication technologies are promising candidates for 4G wireless access systems. In this paper, we focus on the downlink of multicellular networks and we investigate the influence of the inter-cell interference in an unsynchronized frequency division duplex (FDD) context with a frequency resuse of 1. We compare the conventional orthogonal frequency division multiplexing with cyclic prefix modulation (CP-OFDM) and the filter bank based multi-carrier modulation (FBMC). Two tables modeling the mean interference power are given and show that, in FBMC case, the interference is more localized than in OFDM case. Finally, these tables are used to evaluate performance in terms of average capacity in FBMC multi-cell networks compared to CP-OFDM ones.
Signal Processing Advances in Wireless Communications, 2009. SPAWC '09. IEEE 10th Workshop on; 07/2009
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ABSTRACT: In this paper we propose a novel decision feedback (DF) detection strategy for multi-input multi-output (MIMO) spatial multiplexing systems based on multiple processing branches. The proposed detection structure employs multiple cancellation branches with appropriate transformations that modify the initial design. The novel structures for detection exploit different patterns and orderings for the modification of the original feedforward and feedback filters design. We present minimum mean-squared error (MMSE) estimators for the multi-branch structure and the design of MIMO receivers and show that the proposed MMSE design does not require a significant additional complexity. The proposed multi-branch MMSE DF detectors are compared with several existing detectors in the literature via computer simulations and are shown to close the gap between MMSE detectors and the optimal maximum likelihood detector.
Vehicular Technology Conference, 2009. VTC Spring 2009. IEEE 69th; 05/2009
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ABSTRACT: The future wireless communication is expected to be able to improve the efficiency of spectrum usage. To solve the challenge of spectrum shortage, an innovative opportunistic spectrum access strategy, called cognitive radio (CR) has been proposed. Conventional orthogonal frequency division multiplexing (OFDM) has already been suggested as a physical layer candidate for CR system. Herein another potential candidate for CR, OFDM offset quadrature amplitude modulation (OFDM/OQAM) is introduced, and its spectral efficiency for coded multicarrier transmission is compared with cyclic prefix based OFDM (CP-OFDM) and raised cosine windowed OFDM (RC-OFDM) in CR context. Simulated results of spectral efficiency comparison (SEC) for different multicarrier systems are interpreted by theoretically analyzing the out-of-band radiation of their prototype pulses shaping. Both theoretic analysis and experimental results can show that OFDM/OQAM is a more natural candidate than CP-OFDM and RC-OFDM for CR networks application.
Vehicular Technology Conference, 2009. VTC Spring 2009. IEEE 69th; 05/2009
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ABSTRACT: The purpose of this paper is to analyze orthogonal frequency division multiplexing carrying offset QAM (OFDM/OQAM) signal detection using cyclostationary signatures, which are artificially embedded into digital modulated signals. The spectral correlation characterization of OFDM/OQAM signal can be described by a special linear periodic time-variant (LPTV) system. Using this description we have derived the explicit theoretical formulas of cyclic autocorrelation function (CAF) and spectral correlation function (SCF) for OQAM signal. A low-complexity cyclostationary signature detector can be utilized for OQAM signal detection, and experimental results show the advantages of this signature detector.
Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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ABSTRACT: The paper deals with the realization on FPGA of a filter bank based multicarrier modem core. The main blocks of the modem core are for the transmitter: OQAM modulation for transmitter, synthesis filter bank composed from IFFT and polyphase network; and for the receiver: OQAM modulation for receiver, analysis filter bank composed from polyphase network and FFT. The modem core is implemented on FPGA with 10<sup>6 </sup> gates and its frequency is 7.34 kHz per frame with 512 real data
Electrotechnical Conference, 2006. MELECON 2006. IEEE Mediterranean; 06/2006
