BER Analysis of Massive MIMO in Heterogeneous Cellular Network

Localization beyond 5G wireless communication systems is a key technology enabler. It has attracted increasing research as the number of antennas in the wireless transmitters. Localization of user terminals is important communications technology, particularly for a better quality of service, improved security, and location awareness applications. Massive multiple-input and multiple-output (MIMO) is considered one of the key technologies in wireless communications. Therefore, it attracts a significant amount of research. In this paper, an estimate of the location of the user terminal with high precision is proposed by using only a single massive MIMO cell. The massive MIMO system has a high degree of freedom and a high number of antennas. which is utilized to estimate the angle of arrival (AoA) with high accuracy even with highly spatially correlated users then the location is estimated. The simulation finding results show high accuracy as compared to the previously published work. The estimation error in AoA is 1 % and 5 % in distance at 16dB SNR.

As for the massive MIMO (multiple-input and multiple-output) enabled HCNs, we design a QoS-aware association scheme to maximize the sum of achievable rates under long-term rate constraints. Since the various BSs have different transmit power and antennas, this scheme (unbalanced association) may result in an extremely imbalanced load distribution. To fully exploit the network resources, we design another scheme (balanced association) to maximize the network-wide utility that is a logarithmic function of long-term rates. In fact, these schemes can be well implemented in the practical scene since the users can introduce long-term rate constraints to guarantee their QoS requirements. Significantly, it is not the case for the most existing schemes. Considering that these formulated problems are in a nonlinear and mixed-integer form and hard to tackle, we try to develop centralized algorithms using Lagrange multiplier method and distributed algorithms using dual decomposition. Numerical results show that the balanced association significantly outperforms the unbalanced association on the load balancing gain, rate fairness, but the QoS guarantee. In addition, we also show the impacts of the number of massive antennas on the association performance.

A novel transmit power control (TPC) bit estimation technique for FDD-UMTS downlink is proposed. Conventional FDD-UMTS downlink TPC bit estimation algorithm is based on coherent detection, which utilizes pilot bits for channel estimation and uses this estimate to remove the wireless channel effect on TPC bits. However, joint utilization of pilot and TPC bits can improve the detection performance as well as minimize the inherent overhead caused by excessive pilot bits usage in the transmission. In the proposed algorithm, pilot and TPC bits are used collectively for non-coherent detection of the power control command. Power increase and decrease orders are represented by two orthogonal vectors which are made up of pilot and TPC bits. TPC bit error rate (BER) performance comparisons of conventional and proposed algorithms are presented for various multi-path channels and slot formats. It is shown that in all the slot formats and different channel conditions, the proposed algorithm provides superior performances in terms of TPC bit error rate. This performance gain can go up to 15 dB at practical TPC BER (10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ) with certain channel conditions and slot formats.

Non-orthogonal multiple access (NOMA) is one of the most effective techniques for meeting the spectrum efficiency (SE) requirements of 5G and beyond networks. This paper presents two novel methods for improving the SE of the downlink (DL) NOMA power domain (PD) integrated with a cooperative cognitive radio network (CCRN) in a 5G network using single-input and single-output (SISO), multiple-input and multiple-output (MIMO), and massive MIMO (M-MIMO) in the same network and in a single cell. In the first method, NOMA users compete for free channels in a competing channel (C-CH) on the CCRN. The second method provides NOMA users with a dedicated channel (D-CH) with high priority. The proposed methods are evaluated using the Matlab software program using the three scenarios with different distances, power location coefficients, and transmitting power. Four users are assumed to operate on 80 MHz bandwidths (BWs) and use the quadrature phase shift keying (QPSK) modulation technique in all three scenarios. Successive interference cancellation (SIC) and unstable channel conditions are also considered when evaluating the performance of the proposed system under the assumption of frequency selective Rayleigh fading. The best four-user SE performance obtained by user U4 was 3.9 bps/Hz/cell for SISO DL NOMA, 5.1 bps/Hz/cell for SISO DL NOMA with CCRN with C-CH, and 7.2 bps/Hz/cell for SISO DL NOMA with CCRN with D-CH at 40 dBm transmit power. While 64 × 64 MIMO DL NOMA improved SE performance of the best-use U4 by 51%, 64 × 64 MIMO DL NOMA with C-CH CCRN enhanced SE performance by 64%, and 64 × 64 MIMO DL NOMA with D-CH CCRN boosted performance by 65% SE compared to SISO DL NOMA at 40 dB transmit power. While 128 × 128 M-MIMO DL NOMA improved SE performance for the best U4 user by 79%, 128 × 128 M-MIMO DL NOMA with C-CH CCRN boosted SE performance by 85%, and 128 × 128 M-MIMO DL NOMA with D-CH CCRN enhanced SE performance by 86% when compared to SISO DL NOMA SE performance at 40 dB transmit power. We discovered that the second proposed method, when using D-CH with CCR-NOMA, produced the best SE performance for users. On the other hand, the spectral efficiency is significantly increased when applying MIMO and M-MIMO techniques.

The bit error rate (BER) performance of the asynchronous uplink channel of multicarrier code division multiple access (MC-CDMA) systems with maximal ratio combining (MRC) is analyzed. The study takes into account the effects of channel path correlations in generalized frequency-selective fading channels. Closed-form BER expressions are developed for correlated Nakagami fading channels with arbitrary fading parameters. For channels with correlated Rician fading paths, the BER formula developed is in one-dimensional integration form with finite integration limits, which is also easy to evaluate. The accuracy of the derived BER formulas are verified by computer simulations. The derived BER formulas are also useful in terms of computing other system performance measures such as error floor and user capacity.

High speed integrated RF–VLC data communication system: Performance constraints and capacity considerations

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.

Iterative multiuser receivers constitute an effective solution for transmission over Multiple Access Interference (MAI) infested channels, when invoking a combined multiuser detector and channel decoder. Most reduced-complexity methods in this area use the Complex-valued Minimum Mean Squared Error (CMMSE) Multiuser Detector (MUD). Since the desired output of BPSK systems is real-valued, minimizing the Mean Square Error (MSE) between the beamformer's desired output and the real part of the beamformer output has the potential of significantly improving the attainable Bit Error Rate (BER) performance. We refer to this MMSE design as the Real-valued MMSE (RMMSE) receiver. In this paper, we explore a new Soft-Input Soft-Output (SISO) interference cancellation multiuser detection algorithm based on the novel Minimum BER (MBER) criterion. We demonstrate that the MBER turbo receiver outperforms both the CMMSE and the RMMSE algorithms, particularly in so-called `overloaded' beamforming systems, where the number of receiver antennas is lower than the number of users supported.

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

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.

This paper analyzes the bit error rate (BER) for quadrature amplitude modulation (QAM) with L-fold maximal ratio combining (MRC) space diversity in Rayleigh fading channel. The formula is obtained by averaging the bit error probability of M-ary QAM in an additive white Gaussian noise channel over a chi-square distribution with 2L degrees of freedom. This formula overcomes the limitations of the earlier work, which has been limited only to deriving a BER for QAM with two branch MRC space diversity. The BER performance of quadrature phase shift keying with MRC diversity is obtained from the derived formula by setting M=4.

The application of the relay networks enlarges the communication area and improves the transmission. However, the price is the increasing system complexity, which makes the performance analysis of the corresponding channel a more challenging task. To this end, we develop the probability density function (PDF) of the composite cascade channel, and later analyze the outage probability (OP), the bit error rate (BER), and the ergodic capacity over this channel. Firstly, the exact PDF of the small-scale cascade channel, which is combined by several independent and identically distributed (i.i.d.) Rayleigh/Nakagami-m channels, is derived. Then, considering the large-scale and the lognormal distributed shadow, the PDF of the composite cascade channel, following the OP, the BER, and the ergodic capacity performance under the optimal selection combining (OSC) and the maximal ratio combining (MRC) schemes are also deduced. Furthermore, in order to obtain the asymptotic lines of the BER and the ergodic capacity performance, the mixture gamma distribution is exploited. The closed-form expressions for these two kinds of asymptotic lines, both under the OSC and the MRC schemes, are proposed. The numerical simulations confirm that the proposed expressions fit well with the Monte-Carlo results.

An exact and closed-form expression for the average bit error rate (BER) of coherent binary phase-shift keying (BPSK) using maximal ratio combining (MRC) in the presence of multiple cochannel interfering users is derived for correlated Rayleigh fading. Under the assumption that the branch gains of the desired user signal and interfering signals experience correlated Rayleigh fading with the same correlation eigenvector matrix, as is the case for receiver diversity in an omnidirectional scattering environment, this BER expression is valid for arbitrary correlation structure such as 2-D and 3-D channel correlation models, and applys for an arbitrary number of interfering users and an arbitrary number of receiver antennas.

One of the most relevant themes of wireless communication is to achieve better spectral efficiency and provide high reliability while providing rich-content data services despite the existence of several serious challenges. A few of them are multipath fading, multi-user interference, co-channel interference (CCI), inter symbol interference (ISI) etc to name a few. Several techniques have already been developed and deployed to eliminate the fading effects. One of the less explored techniques which have been adopted and discussed in this chapter is based on the structure of the transmitting antenna. The physical dimension of the antenna is varied as per the fading condition by adopting a dynamic process which adjusts the structure to provide the best quality of service (QoS). Two types of antenna set-ups are considered - Single Input-Single Output (SISO) and Multiple Input-Multiple Output (MIMO). The transmitting antenna in this system adaptively updates its aperture to improve the system performance and at the same time optimizes the driving power of the antenna as per requirement. The system changes the effective aperture of the transmitting antenna in high data rate, time varying Rayleigh channels to adapt to a previously set Bit error Rate (BER). However, in a real time environment the BER keeps on changing based on the channel condition. It is difficult to attain a fixed value of BER and hence even more difficult to model the antenna structure for a single time instant. As a result there exist a number of effective aperture dimensions for various BER in a single time instant. Out of the various values, two specific limits of the effective aperture of the transmitting antenna needs to be decided. Fuzzy C-Mean (FCM) Clustering method being one of the most popular and efficient clustering technique is used to set two limits of the aperture within which a particular threshold of the BER is obtained at one particular instant of time. The results derived show the effectiveness of the entire system.

The effects of multipath fading and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of direct-sequence code-division multiple-access (DS-CDMA) systems is studied in this paper. The expression for the conditional BER, conditioned on a given level of fading is derived and then the unconditional BER is evaluated. The BER performance results of the system are evaluated in a fading channel for different magnitude of fading. The proposed approach is also extended to estimate the BER performance of the CDMA system having multiple receiving antennas. The effectiveness of the selection method and maximal ratio combining (MRC) method as diversity combining schemes are investigated and compared. To enhance the system performance channel coding is also applied to the system.