Performance analysis of MIMO systems with multiuser diversity

In a real cellular system, existence of a number of multi-antenna schemes in neighboring cells means that different multi-antenna schemes will experience co-channel interference (CCI) from the same or other multi-antenna schemes. In this work, we have summarized our analysis and simulations related to cellular interference of some specific multiple input multiple output (MIMO) schemes on the same and other MIMO schemes. The goal is to study the impact of interference from MIMO schemes at a user located in the cell edge. Semi-Analytical evaluations of signal to interference and noise ratio (SINR) is done to find out the SINR statistics of different combinations of desired and interfering links. We have studied linear combining receivers for all the link combinations. Based on the current analysis, it is found that space-time block code (STBC) is a severe interferer compared to others, and specific attention is needed to counter the interference introduced by STBC interfering link.

The bit error rate (BER) performance for quadrature amplitude modulation (QAM) with different diversity combining scheme is derived for Rayleigh fading channel using Log-likelihood ratio (LLR). Three combining techniques, maximal ratio combiner (MMC), selection combining (SC), and Equal Gain Combiner (EGC) are considered for the BER analysis in this paper. The average BER performance of QAM symbol through a flat fading channel is derived from the individual bits forming the QAM symbol with MRC, SC, and EGC space diversity. The analytical and simulation of BER performance of the QAM symbol through the fading channel with MMC, SC, and EGC combiner is compared. The both analytical and simulation result shows that the probability of bit error decreases with the order of diversity for all the cases of MRC, SC, and EGC. It is also seen from the results that MRC provides better BER performance than the other two combiners (SC and EGC) for the same environment of the fading channel.

In this paper, we investigate the performance of a free space optical link using Alamouti type Space Time Block Code (STBC) over weak atmospheric turbulence-induced fading channels. An analytical approach is presented to evaluate the bit error rate (BER) performance of a direct detection on-off keying (OOK) free space optical link over a weak atmospheric turbulent condition considering Alamouti type space time block code (STBC) and maximal ratio combining (MRC) at the receiver. The results are evaluated numerically and also by simulation. Results show that there is significant improvement in BER performance at a given BER due to coding and diversity combining at the receiver. The amount of improvement for (M × L ) STBC is of the order of 18 dB, 10 dB and 5 dB for laser source, M=2 and number of photodetector, L= 1, 2 and 4 respectively.

In this paper, a new signal detection scheme for overloaded multiple-input multiple output (MIMO) systems is proposed. In MIMO signal detection with belief propagation (BP), a factor graph consists of many loops that arise high complexity and cause performance degradation due to outliers. Various schemes have been proposed to overcome these issues. In BP with maximal ratio combining (MRC) and minimum mean square error (MMSE) pre-cancellation, a conventional scheme applies MRC on received signals in advance to obtain diversity gain to improve bit error rate (BER) performance as compared with BP using only MMSE pre-cancellation. To achieve further performance improvement, BP using a combined channel matrix is proposed in this paper. In the proposed scheme, the number of observation nodes is increased by combining a part of an original channel matrix to the channel matrix with MRC and MMSE pre-cancellation to enhance diversity gain. Numerical results obtained through computer simulation show that the BER performance of the proposed scheme is superior to that of BP or BP with MRC and MMSE pre-cancellation. The proposed scheme improves BER performance by about 3.1 dB at a BER of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> as compared with the BP withMRC and MMSE pre-cancellation. The computational complexity of the proposed scheme increases as the number of rows of the additional channel submatrix. It is in the same order of magnitude as that of the original BP based MIMO detection scheme.

There has been an increasing interest in digital transmission in the field of mobile radio. In a mobile communication system, because of multipath propagation, the communication channel is modeled as a Rayleigh fading channel. One of the most efficient techniques to reduce the fading effect and improve the system performance is space diversity reception. The average bit error rate (BER) performance of TC M-ary PSK with 2 branch selection combining (SC) and maximal ratio combining (MRC) diversity systems on a correlated Rayleigh fading channel is analysed, and some numerical results are shown. Although the correlation between branch causes signal-to-noise (SNR) loss (relative to the uncorrelated fading case) for SC and MRC diversities, the diversity can lead one to achieve the diversity gain compared to a system without diversity. It is found that the diversity gain of TC 8PSK with SC and MRC diversities is decreased with increasing the fading correlation parameter /spl xi//sup 2/, the diversity gain of TC 8PSK with MRC diversity is larger than TC 8PSK with SC diversity.

An enhanced transmission is presented in a multiple‐input‐multiple‐output (MIMO) dense‐wavelength division multiplexed (DWDM) free‐space‐optical (FSO) communication link using diversity coding techniques under the effect of turbulent weather phenomenon. The findings show good performance with an (8 channels × 2.5 Gbps data rate/channel) 20 Gbps 1500 m transmission distance. The bit‐error‐rate (BER), outage probability (OP), and signal‐to‐noise ratio (SNR) of the diversity combining techniques using maximum‐ratio combining (MRC), selection combining (SC), and equal‐gain combining (EGC) technique are evaluated in this work. The obtained results illustrate that Alamouti, space‐time coding (STC), space‐time block coding (STBC), space‐time trellis code (STTC), orthogonal STBC (O‐STBC), and quasi‐orthogonal STBC ( QO‐STBC ) on the minimum mean‐square‐error, and MRC are worth implementing on the DWDM‐FSO wireless communication systems. The mitigation of atmospheric turbulence is achieved using MIMO diversity combining techniques coding. The simulation results for diversity coding techniques using QO‐STBC/STTC and SC/MRC in the MIMO‐DWDM FSO communication system can improve BER performance, OP, and SNR. The MRC exhibits the lowest OP and BER when compared with the SC and EGC. The numerical results demonstrate that the FSO communication link using DWDM QO‐STBC/STTC improves the power penalty at both BER values under varying atmospheric turbulence conditions for ST, MT, and WT, in comparison to FSO systems without DWDM QO‐STBC/STTC diversity coding techniques.

In this paper, the bit error rate (BER) performance of multiuser multiple-input multiple-output (MIMO) systems over Rayleigh fading channels is studied, and corresponding asymptotic performance is analyzed. Based on the asymptotic analysis at high signal to noise ratio (SNR), using the probability density functions (PDF) of the instantaneous channel power gain, the diversity gain and coding gain of the system with transmit antenna selection (TAS) scheme and space-time block coding (STBC) scheme are derived, respectively. As a result, the same full diversity gain is achieved for two transmission schemes, but their coding gains are different. With the obtained diversity gain and coding gain, the asymptotic BER expressions for two transmission schemes are respectively derived, which are in good agreement with the corresponding simulation results. The results show that the multiuser MIMO system with TAS scheme has better BER performance than that with STBC scheme due to higher coding gain.

Space-time block code (STBC) based on orthogonal design is one of the space-time coding methods to achieve multi-input multi-output (MIMO) diversity gain. STBC can provide sufficient space diversity gain, but it can not provide coding gain. Polar codes based on channel polarization are the first class of provably capacity-achieving codes with low encoding and decoding complexity. In order to improve the bit error rate (BER) performance of STBC, a concatenated scheme with Polar codes and STBC, named Polar-STBC scheme, is proposed in this paper. The BER performance of Polar-STBC system is discussed by numerical simulation under different polar code length, different polar code rates, and different coding methods of STBC. The results show that the performance of Polar-STBC has a big improvement in comparison with that using STBC only. The coding gain of Polar-STBC system is about 5dB when the BER is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Meanwhile, the longer code length and the lower code rate Polar codes have, the better BER performance the Polar-STBC system has. In addition, the different STBC coding methods have influence on the Polar-STBC system. The Polar-STBC system with more receiving antennas has a better BER performance in comparison with those with the same sending antennas and less receiving antennas. The coding gain of Polar-STBC system with 2 receiving antenna is 6.5dB improvement to the system with 1 receiving antenna when BER is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and the code length is 1024.

In order to improve the bit error rate (BER) of multiple-input multiple-output orthogonal frequency diversity multiplexing (MIMO-OFDM) system in Nakagami-m channels, the model used rate-compatible punctured convolution (RCPC) and space-time block code (STBC) at the transmitter, maximum ratio combining (MRC) at the receiver was put forward. The signal-to-noise ratio (SNR) of the MIMO-OFDM system in Nakagami-m channels was studied, the expression of BER was given and the average BER upper limit after RCPC encode was further presented. Simulation result shows that the BER performance and the diversity gain of MIMO-OFDM with RCPC encoding achieve much improvement than the system with no RCPC. Owing to the free distance becomes shorter with the increase of code rate, the BER performance and the diversity gain of RCPC encoded MIMO-OFDM decreases a little

Antenna diversity techniques are used in wireless systems to combat the effects of fading. Signals from multiple receiver antennas are combined to achieve an improved average SNR. maximal ratio combining (MRC) technique is known to give a better SNR gain than Selection Combining (SC) technique. This improved performance of MRC comes at the cost of multiple receiver chains which implies increased receiver complexity and cost. In this paper we compare SC with MRC for three antennas in terms of receiver area and power cost. We show that for the same bit-error rate (BER) performance, SC requires roughly 60% lesser area and 40% lesser power consumption.

Most of the analyses of multiple-input multiple-output (MIMO) systems so far have been based on the ideal Gaussian noise model. In this paper, performance analysis of MIMO systems is performed in a mixture of Gaussian noise and impulsive noise modeled as a symmetric alpha stable process. Three typical MIMO systems are considered: 1) zero-forcing (ZF) system, 2) maximum likelihood (ML) system and 3) space time block coding (STBC) system. The symbol-error-rates (SER) or the upper bound of SER of each system is derived. Simulations are performed in the mixed noise with different impulsive intensity and impulsive level and the results show that the performances of all the systems are degraded greatly in the mixed noise and STBC has no performance gain over ZF and ML when high impulsive noise appears.

An underwater acoustic multimedia communication (UWAMC) system is proposed with 2400 transmission modes according to time-varying multipath underwater acoustic (UWA) channel conditions. The orthogonal variable spreading factor (OVSF) scheme and Gold sequence (GS) scramble code are integrated into multi-input multi-output UWAMC system based on orthogonal frequency-division multiplexing to achieve the quality of service of multimedia transmission in the UWA channel. Binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) adaptive modulation, direct mapping (DM) or space–time block code (STBC) transmission strategies, convolution channel code with rate 1/2 and 1/3, and a power assignment mechanism were adopted in the proposed system. Simulation results show that the bit error rate (BER) and power saving ratio (PSR) performance of the STBC strategy with transmission diversity is superior to that of the DM strategy without transmission diversity, and the performance of the BERs and PSRs of the transmission scheme with the GS scramble code surpasses that of the scheme without the code. The performance of the BERs and PSRs of BPSK modulation with a channel code rate of 1/3 is better than that of BPSK modulation with a channel code rate of 1/2, and the performances of BERs and PSRs of BPSK modulation with a channel code rate of 1/3 are better than that of QPSK modulation with a channel code rate of 1/3. As the length of the OVSF codes increases, the UWAMC system’s BERs decrease, and its PSRs increase. The UWAMC system can achieve either maximum transmission speed or maximum transmission power efficiency.

Spatial correlation is a crucial impairment for practical Multiple Input Multiple Output (MIMO) wireless communication systems. It is important to consider spatial correlation between antennas in actual communication scenario at both sides, i.e. transmit and receive side. Furthermore, we have considered nonorthogonal full rate STBC in MIMO systems equipped with four transmit antennas and four receive antennas in a quasi-static Rayleigh fading channel. In this paper, Bit Error Rate (BER) performance of full rate non-orthogonal Space Time Block code (STBC) is obtained using simulations in MIMO wireless communication systems. Spatial correlation is assumed between antennas at both the transmitter and the receiver sides. For this analysis, we have considered various transmit antenna spacing values of d t = 0.1π, 0.2π, and 0.4π keeping fixed d r = 0.1π and various receive antenna spacing values of d r = 0.1π, 0.2π, and 0.4π keeping fixed d t = 0.1π. The obtained results show that the transmitting diversity is more serious than the receiving diversity in the spatially correlated antenna environment for the specified signal-to-noise ratio. This study will be useful for actual wireless communication implementation where spatial correlation antennas are present in the practical environment of the MIMO wireless communication system.

In this paper, space-time block codes (STBCs) are applied in a distributed fashion in a scenario with multiple cooperating relay stations (RSs) having multiple antennas. By applying the Chernoff bound to the theoretical bit error rate (BER) in Rayleigh fading channels, it turns out that the BER performance has a higher sensitivity to spatial correlation in multiple input multiple output channels than to different receive powers at the receiver from different cooperating RSs. If the number of overall available antennas exceeds the number of required antennas for the considered STBC, based on the theoretical analysis a criterion for the selection of the antennas which should cooperate in order to achieve the best BER performance is given

The performance of MMSE single‐user detection (SD) and multi‐user detection (MD) STBC multi‐carrier code division multiple access (MC‐CDMA) systems are analysed and compared in the case of two transmit antennas and one or two receive antennas over Rayleigh fading channels and then over the stochastic multiple input multiple output (MIMO) METRA channel model. With two transmit and one receive antennas, MD achieves a gain of roughly 1 dB for non‐full load systems while the same performance is obtained with MD and SD for full load systems. Besides, with two receive antennas, we present a sub‐optimal and an optimal MMSE SD MIMO MC‐CDMA schemes, this last one offering a very good performance. Finally, the very good behaviour of MMSE space‐time block coding (STBC) MC‐CDMA systems is confirmed over the realistic multi element transmit receive antennas (METRA) MIMO channel. Copyright © 2004 AEI