A Novel OSSMIC Receiver for Downlink MIMO MC-CDMA Systems (original) (raw)
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IET Communications, 2011
Multi-carrier code division multiple access (MC-CDMA) allows multiuser communication with frequency diversity. To increase the system data rates, spatial multiplexing for multiple-input multiple-output (MIMO) MC-CDMA has been investigated. This study proposes a chip level layered space-time (LST) receiver architecture for coded downlink MIMO MC-CDMA systems. As the conventional chip level ordered successive interference cancellation (OSIC) receiver is unable to overcome multiple access interference and performs poorly in multiuser scenarios, the proposed receiver cancels both spatial and multiuser interference in an ordered LST detection process by requiring only the knowledge of the desired user's spreading sequence. Simulation results show that the proposed receiver not only performs better than the existing linear detectors but also outperforms both the chip and symbol level OSIC receivers. In this study the authors also compare the error rate performance between the proposed system and MIMO orthogonal frequency division multiple access (MIMO OFDMA) system and they justify the comparisons by deriving and analysing the pairwise error probability (PEP) for both systems. MIMO MC-CDMA demonstrates a better performance over MIMO OFDMA under low system load. If all users' spreading sequences are known, multiuser interference can be reduced and MIMO MC-CDMA performs better than MIMO OFDMA at all system loads.
Reduced complexity and improved performance receiver for downlink MIMO MC-CDMA systems
2008 3rd International Symposium on Communications, Control and Signal Processing, 2008
In this paper a low complexity MIMO MC-CDMA receiver is proposed. We investigate the receiver performance and complexity in the case of despreading Multicarrier Code Division Multiple Access signals (MC-CDMA) prior to V-BLAST detection in Multiple Input Multiple Output systems (MIMO). The proposed structure shows that for iterative detection, despreading before detection (DBD) reduces the effect of multiple access interference (MAI), and the reported results demonstrate improved bit error rate (BER) performance and user capacity of the system over despreading after detection (DAD). Furthermore, DBD results in reduced system complexity. The performance of both detectors is evaluated using computer simulations for a frequency selective slow Rayleigh fading channel.
SIC-VBLAST Receiver for Coded Uplink Mimo MC-CDMA Systems
2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, 2005
In this paper, a convolutionally-coded uplink multicarrier code-division multiple-access (MC-CDMA) system with multiple transmit and receive antennas is considered, over multipath Rayleigh fading channels. In this framework, a new iterative hybrid scheme based on the combination of a successive interference cancellation (SIC) and a vertical-BLAST detector is presented, to cope, respectively, with multiple-access interference and multiple-substream interference. Based on simulation results, the performance of the uplink MC-CDMA system, decoded by hard or soft-input decoding methods, is found to improve significantly by the use of antenna arrays in conjunction with the proposed multiuser receiver.
In this paper, we propose two receiving schemes for multiple antenna multi-carrier code division multiple access (MC-CDMA) systems. Our proposed schemes are based on vertical Bell labs layered space-time (V-BLAST) architecture. The interference cancellation is performed serially on different sub-carriers. The channel matrices related to different sub-carriers are used in the successive interference cancellation (SIC) block. In addition some permutation matrices are used for ordering of transmitted signals in the transmitter. Two schemes, hard and soft, are proposed for signal detection in the receiver. We will show by computer simulations that the proposed schemes have better performance than the other methods like V-BLAST OFDM systems .
4MORE: An advanced MIMO downlink MC-CDMA system
2006
The IST 4MORE project defines a multicarrier code division multiple access (MC-CDMA) radio system with multiple mobile users and advances this one step towards implementation through the design of a System on Chip (SoC) for a 4G terminal employing multiple antennas, based on MC-CDMA. In this contribution we present results of the simulated downlink scenario, which is the base for the designed demonstrator. We cover different channels, various modulation schemes, coarse time synchronization, carrier frequency offset tracking and finally the effect and countermeasures which are needed for RF impairments. The implemented air interface offers transmitting 5.5 bits/s/Hz over two spatial parallel multiplexed data streams.
A Chip-Level BSOR-Based Linear GSIC Multiuser Detector for Long-Code CDMA Systems
Eurasip Journal on Wireless Communications and Networking, 2008
We introduce a chip-level linear group-wise successive interference cancellation (GSIC) multiuser structure that is asymptotically equivalent to block successive over-relaxation (BSOR) iteration, which is known to outperform the conventional block Gauss-Seidel iteration by an order of magnitude in terms of convergence speed. The main advantage of the proposed scheme is that it uses directly the spreading codes instead of the cross-correlation matrix and thus does not require the calculation of the crosscorrelation matrix (requires 2NK 2 floating point operations (flops), where N is the processing gain and K is the number of users) which reduces significantly the overall computational complexity. Thus it is suitable for long-code CDMA systems such as IS-95 and UMTS where the cross-correlation matrix is changing every symbol. We study the convergence behavior of the proposed scheme using two approaches and prove that it converges to the decorrelator detector if the over-relaxation factor is in the interval ]0, 2[. Simulation results are in excellent agreement with theory.
A low complexity MMSE multiuser detector for DS-CDMA
Conference Record of Thirty-Fifth Asilomar Conference on Signals, Systems and Computers (Cat.No.01CH37256), 2001
The optimal receiver for detecting direct sequence code division multiple access (DS-CDMA) signals suffers from computational complexity that increases exponentially with the number of users. Several suboptimal multiuser detectors (MUDs) have been proposed to overcome this problem. Due to the nonlinear nature of the decision boundary of the optimal receiver, it is known that nonlinear receivers outperform linear receivers. Radial basis function (RBF) MUD is a nonlinear suboptimal receiver that can perfectly approximate this decision boundary and it needs no training since it is fully determined when the spreading codes of all users and the channel impulse response (CIR) are known. However, the RBF MUD suffers from structural complexity since the number of hidden nodes (center functions) in its structure increases exponentially with the number of users. In this study, we propose a new method to minimize the number of center functions of the RBF MUD using a genetic algorithm (GA) and the least mean squares (LMS) algorithm. With simulations performed in AWGN and multipath channels it is shown that the proposed method immensely reduces the complexity of the RBF MUD with a negligible performance degradation.
Asynchronous multi-stage SIC detector for DS-CDMA systems over multipath fading channels
2001
A new interference cancellation (IC) scheme is proposed for the uplink of direct-sequence code division multiple access (DS-CDMA) systems communicating over mobile radio channels. The IC detector presented belongs to the subclass of multiuser detectors that employs a multi-stage successive interference cancellation (SIC), and the aim is to show that a low complexity detector can perform well in a mobile radio environment. The new multi-stage SIC scheme includes non-decision directed IC with a modified RAKE combiner to use the diversity in frequency-selective channels, and it works with a finite processing window sliding each iteration to process a new data symbol. The performance is evaluated with known asynchronous delays and channel parameters, in a multipath environment. The results show that the proposed detector is near-far resistant and the loss in performance compared to the single-user bound is small
A Multicarrier-CDMA Space–Time Receiver With Full-Interference-Suppression Capabilities
IEEE Transactions on Vehicular Technology, 2008
This paper proposes a low-complexity multicarriercode-division-multiple-access (MC-CDMA) space-time receiver with full-interference-suppression capabilities. First, we derive a complete model of the interference which takes into account multiple-access, intersymbol, and intercarrier interferences. Based on this model, we introduce a new multicarrier-interferencesubspace-rejection (MC-ISR) receiver and analyze its performance in an unknown time-varying Rayleigh channel with multipath, carrier offset, and cross correlation between subcarrier channels. We also propose a realistic implementation of this receiver, which includes an efficient strategy for carrier-offset recovery in a multicarrier-and multiuser-detection scheme. In addition, based on the Gaussian assumption, we derive a link-/system-level performance analysis of the MC-ISR over the two MC-CDMA air-interface configurations, which are the multitone CDMA and the multicarrier direct-sequence CDMA, and validate it by simulations. The gains in the throughput, which are attainable by the MC-ISR, are significant and evaluated in this paper as functions of the air-interface configuration, the number of subcarriers, and the modulation order.
SIC and PIC Multiuser Detection for Prefix-Assisted DS-CDMA Systems
Csa, 2005
In this paper we present iterative frequency-domain multiuser detection (MUD) receivers for the uplink transmission of direct sequence code division multiple access systems (DS-CDMA) that combine iterative block decision feedback equalization (IB-DFE) principles with interference cancelation techniques. Both successive interference cancelation (SIC) and parallel interference cancelation (PIC) structures are considered. Our performance results show that the proposed receiver structures have excellent bit error rate (BER) performances, that can be close to the single-user matched filter bound (MFB), even for fully loaded systems and severely time-dispersive channels 1 .