ZF Receivers Research Articles

Исследование детектирования ZF и MMSE в системах MIMO

The proliferation of obstacles in urban environments, such as buildings, wires, and trees, can cause signal re-reflection, resulting in difficulties in detecting the original one. Multipath propagation occurs when electromagnetic waves hit natural and man-made obstacles, leading to the reflection, scattering, and diffraction of waves. This can result in multiple waves arriving at the receiving antenna with different delays, attenuations, and phases. To address this problem, the widely used in modern wireless communication systems MIMO technology (Multiple Input Multiple Output) can be utilized. It uses multiple transmitting and receiving antennas to increase communication channel throughput and reduce errors that occur during data transmission. This paper examines a receiver with decorrelation (ZF receiver) and a receiver that minimizes the minimum mean square error (MMSE). Additionally, an algorithm for a MIMO transmission system model using ZF and MMSE receivers is presented. In the final section of the article, the results of Bit Error Rate (BER) modeling are presented for different numbers of transmitting and receiving antennas. The presented algorithm can significantly reduce errors that occur during data transmission in urban environments, where multipath propagation is common because of signal re-reflection. The use of MIMO technology with decorrelation and MMSE receivers can increase the efficiency of communication channels and make wireless communication more reliable in urban environments.

Clustered Double-Scattering Channel Modeling for XL-MIMO With Uniform Arrays

Extra-large multiple-input multiple-output (XL-MIMO) systems reveal themselves as a potential candidate for the sixth generation (6G) of wireless communication systems due to their features. As XL-MIMO has a large antenna array, and, typically, the urban environment is plenty of obstacles and reflectors, the spatial non-stationarities are introduced in the signal received at the base station (BS), which means that only a portion of the antenna array is visible to users; hence, accurately modeling XL-MIMO channels is paramount. Previous works on XL-MIMO channel modeling have adopted the non-stationarities only in a spatial sense, and do not consider spatial-time evolution scenarios. Moreover, simplified models with only one set of clusters between the BS and the user equipment (UE) are usually adopted; hence, there is a lack of understanding regarding such channels modeling in the literature. This work proposes and extensively analyzes a double-scattering XL-MIMO channel model, by admitting two types of scattering clusters, one placed at the BS side, and another one located near the UEs. In addition, two distinct antenna array configurations are included in the analysis, the uniform linear and planar arrays (ULA and UPA). We propose a new double-scattering channel model under UPA arrangements, suitable for modeling spatial non-stationarities scenarios in XL-MIMO dynamic environment subject to BS-cluster and UE-cluster correlation, and birth-death channel clusters and scatterers. Numerical results for signal-to-interference-plus-noise ratio (SINR), condition number (CN), and spectral efficiency (SE) performance metrics considering different XL-MIMO channels and system configurations are analyzed via Monte-Carlo simulations, under linear combiners MRC, ZF, and MMSE. Also, we characterize the impact of the number of visible clusters per user, the birth-death rate growth effect on the channel clusters and scatterers, and the favorable propagation effect according to the size of visibility region (VR) overlap. It can be observed that the birth and death processes have a significant impact on the system performance. Under the proposed clustered double-scattering channel modeling, the analyzed XL-MIMO linear receivers presented an SINR degradation around 3 to 4 dB for the MMSE when the number of UEs substantially increased, while the ZF and MRC receivers present a decrease of 1 to 2 dB, approximately, in SINR for the considered dynamic configuration compared with static scenarios.

Uplink Performance Analysis of MU-MIMO ZF Receiver Over Correlated Rayleigh Fading Channel with Imperfect CSI

Uplink Performance Analysis of MU-MIMO ZF Receiver Over Correlated Rayleigh Fading Channel with Imperfect CSI

A Novel Diversity Receiver Design for Cooperative Transmission System

In this paper, we consider the performance of an amplify-and-forward relaying-based multiple-input multiple-output space–time-block-coded cooperative communication system. We propose an efficient two-stage receiver design for a relay-assisted transmission scenario over frequency-selective channels. It is also demonstrated that the receiver is able to achieve the full diversity order of the system by incorporating linear processing techniques. With this method, the potential spatial diversity and multipath diversity can be obtained by using the diversity-combining technique, which frequency-selective fading channels can be equivalently transformed. Simulation results show that the proposed scheme significantly outperforms the minimum mean square error and ZF receivers, while maintaining nearly linear complexity.

High Performance Detection Using Three Different weight Blind Algorithms in ZF Receiver for Uplink Multi-User Massive MIMO in 5G Wireless Communications

High Performance Detection Using Three Different weight Blind Algorithms in ZF Receiver for Uplink Multi-User Massive MIMO in 5G Wireless Communications

Massive MIMO-Enabled Full-Duplex Cellular Networks

In this paper, we provide a theoretical framework for the study of massive multiple-input multiple-output (MIMO)-enabled full-duplex (FD) cellular networks in which the self-interference (SI) channels follow the Rician distribution and other channels are Rayleigh distributed. To facilitate bi-directional wireless functionality, we adopt (i) a downlink (DL) linear zero-forcing with self-interference-nulling (ZF-SIN) precoding scheme at the FD base stations (BSs), and (ii) an uplink (UL) self-interference-aware (SIA) fractional power control mechanism at the FD user equipments (UEs). Linear ZF receivers are further utilized for signal detection in the UL. The results indicate that the UL rate bottleneck in the baseline FD single-antenna system can be overcome via exploiting massive MIMO. On the other hand, the findings may be viewed as a reality-check, since we show that, under state-of-the-art system parameters, the spectral efficiency (SE) gain of FD massive MIMO over its half-duplex (HD) counterpart largely depends on the SI cancellation capability of the UEs. In addition, the anticipated two-fold increase in SE is shown to be only achievable with an infinitely large number of antennas.

Upper Bound on Uplink Sum Rate for Multi-Cell Massive MU-MIMO Systems With ZF Receivers

In this letter, uplink sum rate for multi-cell massive multi-user multiple-input multiple-output (MU-MIMO) systems with zero-forcing receivers is analyzed. To be practical, imperfect channel state information obtained through uplink training is assumed, and both large scale path loss and small scale fading effects are considered. A tight upper bound on sum rate is derived in closed form, which is applicable to MU-MIMO systems with any number of receiving antennas. The tightness of the upper bound is theoretically proved for massive MU-MIMO systems and is further demonstrated by computer simulations. The result thus enables a better understanding of multi-cell massive MU-MIMO systems and facilitates system design in practice.

Energy efficiency analysis of linear receivers for large antenna system in fading channels

ABSTRACTEnergy efficiency (EE) is a prominent research issue in massive Multiple Input Multiple Output (MIMO) wireless systems. In this paper, the energy efficiency of a large multiuser antenna system, using maximum ratio combining (MRC) and zero forcing receivers (ZF) has been analyzed in Rayleigh and Ricean fading channels. For Rayleigh fading both MRC and ZF receivers and for Ricean fading only MRC receiver is considered. The analysis is done assuming imperfect channel state information (CSI) and ignoring the effect of large scale fading. The effect of power consumption of all devices used in the channel, loss factors of antenna feeder, Direct current (DC)-DC and main power supplies and active coolant system are also considered. The results are derived for scaled down and un-scaled transmitted power. For Ricean fading channel when power is scaled down by the number of antennas at Base Station (BS), the energy efficiency increases with increase in spectral efficiency. For Rayleigh fading channel, with increase in transmitted power the spectral efficiency first increases, and after a certain level of transmitted power the energy efficiency decreases with increase in spectral efficiency. It has been observed here that MRC and ZF receivers give high spectral efficiency in Ricean and Rayleigh fading respectively.

Performance analysis of ZF receivers with imperfect CSI for uplink massive MIMO systems

We consider the uplink of massive multipleinput multiple-output systems in a multicell environment. Since the base station (BS) estimates the channel state information (CSI) using the pilot signals transmitted from the users, each BS will have imperfect CSI in practice. Assuming zero-forcing method to eliminate the multi-user interference, we derive the exact analytical expressions for the probability density function (PDF) of the signal-to-interference-plus-noise ratio (SINR), the corresponding achievable rate, the outage probability, and the symbol error rate (SER) when the BS has imperfect CSI. An upper bound of the SER is also derived for an arbitrary number of antennas at the BS. Moreover, we derive the upper bound of the achievable rate for the case where the number of antennas at the BS goes to infinity, and the analysis is verified by presenting numerical results.

Optimal number of users in zero-forcing based multiuser MIMO systems with large number of antennas

The optimal number of users achieving the maximum sum throughput is analyzed in zero-forcing (ZF) based multiuser multiple-input multiple-output (MIMO) systems with a large number of base station (BS) antennas. By utilizing deterministic ergodic sum rates for the ZF-beamforming (ZF-BF) and ZF-receiver (ZF-R) with a large number of BS antennas [1], [2], we can obtain the ergodic sum throughputs for the ZF-BF and ZF-R for the uplink and downlink frame structures, respectively. Then, we can also formulate and solve the optimization problems maximizing the ergodic sum throughputs with respect to the number of users. This paper shows that the approximate downlink sum throughput for the ZF-BF is a concave function and the approximate uplink sum throughput for the ZF-R is also a concave function in a feasible range with respect to the number of users. The simulation results verify the analyses and show that the derived numbersof users provide the maximum sum throughputs for the ZF-BF as well as ZF-R in multiuser MIMO systems with a large number of BS antennas.

Sum Rate Analysis of ZF Receivers in Distributed MIMO Systems

The performance of single-cell distributed multiple-input multiple-output (D-MIMO) systems is not only affected by small-scale Rayleigh fading but also from large-scale fading and path-loss. In this paper, we elaborate on the sum rate of D-MIMO systems employing linear zero-forcing receivers, accounting for both large and small-scale fading effects, as well as spatial correlation at the transmit side. In particular, we consider the classical lognormal model and propose closed-form upper and lower bounds on the achievable sum rate. Using these bounds as a starting point, we pursue a "large-system" analysis and provide asymptotic expressions when the number of antennas at the base station (BS) grow large, and when the number of antennas at both ends grow large with a fixed and finite ratio. A detailed characterization in the asymptotically high and low signal to noise ratio regimes is also provided. An interesting observation from our results is that in order to maximize the sum rate, the RPs should be placed at unequal distances to the BS when they experience the same level of shadowing. The resulting closed-form expressions are compared with the corresponding results on MIMO optimal receivers.

Performance Analysis and High-SNR Power Allocation for MIMO ZF Receivers with a Precoder in Transmit-Correlated Rayleigh Channels

In this letter, the multiple-input multiple-output (MIMO) system with a precoder is considered in the transmit-correlated Rayleigh channels. We especially target the MIMO system employing zero forcing receivers. Based on random matrix theory, we first derive the exact probability density function (PDF) of the signal-to-interference-plus-noise ratio (SINR). Using the derived SINR PDF and a close approximation of the Gaussian Q-function, we derive a tight closed-form approximation of the symbol error rate (SER). In the high signal-to-noise ratio (SNR) regime, we also propose a high-SNR power allocation (HPA) by minimizing the global SER approximation under the total power constraint. Our SER analysis suggests that the SER approximation can be used to estimate the error probability. At high SNRs, the computationally efficient HPA converging to the optimal PA achieves noticeable performance gain over the equal PA, particularly in the high transmit correlation scenario. Furthermore, the performance gain of the proposed HPA increases with the diversity order.

Reliability Analysis of Combing Opportunistic Scheduling and Transmit Antenna Selection with Zero-Forcing Receivers in SM-MIMO Systems

In this paper, we propose a novel scheme combing opportunistic schedule (OS) and transmit antenna selection (Tx-AnSS) with ZF receivers under imperfect channel estimation in SM-MIMO systems, where the user set and the transmit antenna subset are adaptively selected according to channel state information (CSI), which is feedback from the receive side. First, we derive the average effective SNR and both analytical forms and approximation expressions for outage probability and BER expression, showing that combining multiuser diversity (MUD) and Tx-AnSS in SM-MIMO systems provides much larger diversity and better performance than the scheme without MUD or Tx-AnSS. Further, the diversity gains for both outage probability and BER expression are also quantified through asymptotic analysis.

Capacity Analysis of the VBLAST MIMO System in Fading Condition with MQAM Modulation

input multiple output (MIMO) system using multiple transmit and receive antennas are widely recognized as the vital breakthrough that will allow future wireless systems to achieve higher data rates and also to increase diversity to combat channel fading. Therefore, a MIMO system can provide capacity gain and diversity gain. In this paper, we investigate the channel capacity issue of the Vertical$Bell Laboratories Layered Spa ce$Time (V$ BLAST) multiple$input multiple$output (MIMO) system with minimum min square error (MMSE) receiver and zero$f orcing (ZF) receivers in fading channel condition. In this paper, the difference in capacity of MIMO system with the MMSE receiver and ZF receiver is validated by comparing the mathematical relation and the simulated results. KeywordsMMSE, ZF, Capacity, Rician factor.

MIMO Systems with Intentional Timing Offset

The performance of MIMO systems with intentional timing offset between the transmitters has recently been the focus of study of different researchers. In these schemes, a nonzero (but known) symbol timing offset is introduced between the signals transmitted from the different transmitters to improve the performance of MIMO systems. This leads to a reduction in Interantenna Interference (IAI), and it is shown that an advanced receiver can utilize this information to extract significant performance gains. In this paper, we show that this transmission scheme may be used in conjunction with different kinds of receivers including ZF, MMSE, and sequence detection-based receivers. We also consider the design of novel pulse shapes that reduce the IAI at the expense of slightly higher intersymbol interference (ISI) and show that additional gains may be achieved.

Delay-tolerant distributed linear convolutional space-time code with minimum memory length under frequency-selective channels

In cooperative communication networks, the performance of distributed space-time code will be severely degraded if the timing synchronization among relay nodes is not perfect. In this letter, we propose a systematic construction of the so called distributed linear convolutional space-time code (DLCSTC) for multipath fading channels that does not require the synchronization assumption. We derive sufficient conditions on the code design such that the full cooperative and multipath diversities can be achieved under the minimum memory length constraint. Then we design DLCSTCs that both have the traceorthonormality property and achieve the full diversity. We show that the proposed codes can also achieve the full diversity for asynchronous cooperative communications with ZF, MMSE and MMSE-DFE receivers under frequency-selective channels. Finally, various numerical examples are provided to corroborate the analytical studies.

Distributed linear convolutive space-time codes for asynchronous cooperative communication networks

In user cooperative communications, time offsets among the relay nodes may distort the structure of a distributed space-time code, and therefore impair the diversity gain. In this paper, a distributed linear convolutive space-time coding scheme is proposed for asynchronous cooperative communication networks. We propose systematic construction methods of linear convolutive space-time codes (DLC-STC) that are .insensitive to the timing errors, i.e., they achieve the full spatial diversity under any delay profile. We then study the diversity property of the delay-tolerant DLC-STC with suboptimal receivers that have low decoding complexity. We show that with the ZF, MMSE and MMSE-DFE receivers, our proposed codes also achieve the full spatial diversity in the asynchronous scenario.

An antenna selection algorithm for spatial multiplexing systems in BLAST receiver

In this paper, the antenna selection problem for spatial multiplexing systems in a BLAST receiver is investigated. In order to search the optimal antenna subset, a selection criterion is proposed, which is able to obtain the largest minimum post-detection SNR. The number of required antennas is deduced, which is determined by the system performance requirement for the existing RF chains. Simulation result shows that the optimal subset in a BLAST receiver has higher minimum sub-channel SNR than that in a ZF receiver. Computation of system performance can be fitted to a simple function, and it is simpler for the proposed algorithm to compute the required antenna number.