Multiple-input Multiple-output Code-division Multiple Access Research Articles

Performance of turbo coded triply-Polarized MIMO–CDMA system for downlink communication

In this paper, the performance of a turbo coded, triply-Polarized multiple-input multiple-output (MIMO) aided Code Division Multiple Access (CDMA) is investigated for Stanford University Interim (SUI) and Long-term Evolution (LTE) channel model specifications. The minimum mean square error algorithm based on ordered successive interference cancellation (OSIC) Multi-user detection (MUD) technique is implemented at each mobile station for diminishing the effects of multi-stream interference (MSI). We observe from the simulation results that a better bit error rate(BER) performance with less signal to noise ratio (SNR), is exhibited by our considered coded system in comparison with an un-coded system. The simulation results reveal that the MIMO–CDMA system with triply-Polarized antenna structure requires a higher SNR than a uni-Polarized antenna system for achievement of the same BER. However, it provides the advantage of replacement of three uni-polarized antennas by a single triply-Polarized antenna thereby achieves a higher data rate with reduced size of MS.

A Survey on Complementary-Coded MIMO CDMA Wireless Communications

In this paper, we present a comprehensive survey on complementary code (CC)-based multiple-input multiple-output (MIMO) code-division multiple access (CDMA) for futuristic wireless communications. This paper starts with the construction of CCs and then proceeds to describe the design of CC-based CDMA and MIMO wireless communication systems. Complementary-coded chip-level space–time coding offers a unique paradigm to implement multiuser MIMO systems, opening up a new dimension to combine multiple-access and multiple-antenna techniques in a unified platform for a possible system design optimization of a wireless communication system in the future. In this paper, we will also discuss various potential research topics and technical challenges that need to be tackled before a complementary-coded MIMO CDMA system can be implemented in practical wireless applications.

Improvement of BER performance in MIMO–CDMA systems by using initial–phase optimized gold codes

This paper describes a new approach to improve the bit error rate (BER) performance of a multiple-input multiple-output code-division multiple-access (MIMO-CDMA) system over quasi-static Rayleigh fading channels. The system considered employs robust space-time successive interference cancellation detectors and initial-phase optimized Gold codes for the improvement. The results clearly indicate that the use of initial-phase optimized Gold codes can significantly improve the BER performance of the system compared to the performance of a multiuser MIMO-CDMA system with conventional nonoptimized Gold codes. Furthermore, this performance improvement is achieved without any increase in system complexity.

Low complexity frequency domain hybrid-ARQ chase combining for broadband MIMO CDMA systems

In this paper, we consider high-speed wireless packet access using code division multiple access (CDMA) and multiple-input multiple-output (MIMO). Current wireless standards, such as high speed packet access (HSPA), have adopted multi-code transmission and hybrid-automatic repeat request (ARQ) as major technologies for delivering high data rates. The key technique in hybrid-ARQ, is that erroneous data packets are kept in the receiver to detect/decode retransmitted ones. This strategy is refereed to as packet combining. In CDMA MIMO-based wireless packet access, multi-code transmission suffers from severe performance degradation due to the loss of code orthogonality caused by both interchip interference (ICI) and co-antenna interference (CAI). This limitation results in large transmission delays when an ARQ mechanism is used in the link layer. In this paper, we investigate efficient minimum mean square error (MMSE) frequency domain equalization (FDE)-based iterative (turbo) packet combining for cyclic prefix (CP)-CDMA MIMO with Chase-type ARQ. We introduce two turbo packet combining schemes: i) In the first scheme, namely "chip-level turbo packet combining", MMSE FDE and packet combining are jointly performed at the chip-level. ii) In the second scheme, namely "symbol-level turbo packet combining", chip-level MMSE FDE and despreading are separately carried out for each transmission, then packet combining is performed at the level of the soft demapper. The computational complexity and memory requirements of both techniques are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. The throughput is evaluated for some representative antenna configurations and load factors to show the gains offered by the proposed techniques.

Bit Error Rate Performance of a MIMO-CDMA System Employing Parity-Bit-Selected Spreading in Frequency Nonselective Rayleigh Fading

We analytically derive the upper bound for the bit error rate (BER) performance of a single user multiple input multiple output code division multiple access (MIMO-CDMA) system employing parity-bit-selected spreading in slowly varying, flat Rayleigh fading. The analysis is done for spatially uncorrelated links. The analysis presented demonstrates that parity-bit-selected spreading provides an asymptotic gain of10log(Nt)dB over conventional MIMO-CDMA when the receiver has perfect channel estimates. This analytical result concurs with previous works where the (BER) is determined by simulation methods and provides insight into why the different techniques provide improvement over conventional MIMO-CDMA systems.

MIMO-CDMA systems: signature and beamformer design with various levels of feedback

We investigate the signature and beamformer design problem for the uplink of multiple-input multiple-output code-division multiple-access (MIMO-CDMA) systems with the sum capacity and the systemwide mean-square error (MSE) as performance metrics. We first construct iterative algorithms to find the jointly optimum temporal signatures and transmit beamformers under the assumption of perfect temporal signature and transmit beamforming feedback. Next, motivated by the need to reduce the amount of feedback, we present a low-complexity sequential orthogonal temporal signature assignment algorithm for given transmit beamformers. Our approach is based on minimizing the difference between the performance of the MIMO-CDMA system and the described upper bounds at each signature assignment step. We next note that the transmit beamformers can be shaped depending on the channel state information (CSI) available at the transmitter. We investigate the cases of various levels of available feedback resulting in different beamformer structures and present a joint orthogonal temporal signature assignment and beamforming algorithm. We observe that as the available feedback level is increased, the performance of the joint signature and beamformer assignment algorithm approaches the performance upper bounds. In particular, we observe that a substantial performance gain is obtained when the individual channel state information is available at the transmitter side

Multi-user MIMO CDMA systems using complete complementary sequences

The authors propose a novel use of complete complementary (CC) sequences for increased spectral efficiency in a multiple-input–multiple-output (MIMO) code division multiple access (CDMA) system. The new method overcomes many of the problems and limitations persistent in single-input–single-output (SISO) and proves that under the proposed MIMO CC-CDMA system, the capacity for the number of supported users increases linearly by the number of transmitters. The paper also shows that the MIMO CC-CDMA system demonstrates a superior performance over those using traditional Walsh spreading sequences (Walsh-CDMA). Results include the bit error rate comparison for CC-CDMA frequency selective fading channels and that of the Walsh-CDMA under flat fading channels.

Spectral efficiency of distributed MIMO code division multiple access systems over multipath fading channels

AbstractDistributed multiple‐input multiple‐output (MIMO) system is a new architecture for next generation wireless communication systems with distributed multiple antennas. In this paper, an uplink model for multiuser distributed MIMO systems with wideband code‐division multiple‐access (CDMA) technology is presented. We focus on the case where there is no channel state information at the transmitter, but channel state information is assumed at the receiver. The spectral efficiency of the uplink system with single‐user detectors at the base stations under multipath fading channels is investigated carefully. Two cases with different assumptions of interference knowledge are studied in detail. The spreading sequences of the CDMA systems are assumed to employ loosely synchronized (LS) spreading sequences and random spreading sequences respectively. LS spreading sequences exhibit a so‐called interference free window (IFW), where both the auto‐correlation and cross‐correlation of the codes become zero. Therefore LS sequences have the promise of mitigating the effects of inter symbol interference (ISI) and multiple access interference (MAI) in multipath fading channels. It is shown by numerical results that the uplink spectral efficiency of the distributed MIMO‐CDMA system using LS sequences can significantly outperform that of the system using random spreading sequences. Copyright © 2005 John Wiley & Sons, Ltd.