Optimal precoder designs for sum rate maximization in MIMO multiuser multicells

This paper is concerned with the joint linear precoder design problem for the multiuser multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) in which multiple femto base stations (FBSs) coexist with a macro base station (MBS). To tackle the inter-user interference in the macrocell, we exploit the blockdiagonalization scheme and then use the convex optimization to maximize the sum rate of the macrocell. The FBS transmission strategy is to maximize the sum-rate of femtocells subject to the transmitted power constraints per FBS and restrictions on the cross-tier interference to macro-users (MUs). Such a design problem is typically nonconvex, and, thus, challenging to find the FBS precoders. We reformulate the design problem of the FBS precoders as a d.c. (difference of convex functions) programming, and develop an efficient iterative algorithm to obtain the optimal precoders. Numerical simulation results show that the proposed algorithm outperforms the other methods in terms of the total sum-rate of the HetNet.

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Gyre Precoding and T-Transformation-Based GFDM System for UAV-Aided mMTC Network

Electronics ◽

10.3390/electronics10232915 ◽

2021 ◽

Vol 10 (23) ◽

pp. 2915

Author(s):

Joarder Jafor Sadique ◽

Shaikh Enayet Ullah ◽

Raad Raad ◽

Md. Rabiul Islam ◽

Md. Mahbubar Rahman ◽

...

Keyword(s):

Channel Coding ◽

Signal To Noise Ratio ◽

Multiple Input Multiple Output ◽

Mobility Model ◽

Base Station ◽

Multiple Input ◽

Input Multiple Output ◽

Aerial Vehicle ◽

Noise Ratio ◽

User Interference

In this paper, an unmanned aerial vehicle (UAV)-aided multi-antenna configured downlink mmWave cooperative generalized frequency division multiplexing (GFDM) system is proposed. To provide physical layer security (PLS), a 3D controlled Lorenz mapping system is introduced. Furthermore, the combination of T-transformation spreading codes, walsh Hadamard transform, and discrete Fourier transform (DFT) techniques are integrated with a novel linear multi-user multiple-input multiple-output (MU-MIMO) gyre precoding (GP) for multi-user interference reduction. Furthermore, concatenated channel-coding with multi-user beamforming weighting-aided maximum-likelihood and zero forcing (ZF) signal detection schemes for an improved bit error rate (BER) are also used. The system is then simulated with a single base station (BS), eight massive machine-type communications (mMTC) users, and two UAV relay stations (RSs). Numerical results reveal the robustness of the proposed system in terms of PLS and an achievable ergodic rate with signal-to-interference-plus-noise ratio (SINR) under the implementation of T-transformation scheme. By incorporating the 3D mobility model, brownian perturbations of the UAVs are also analyzed. An out-of-band (OOB) reduction of 320 dB with an improved BER of 1×10−4 in 16-QAM for a signal-to-noise ratio, Eb/N0, of 20 dB is achieved.

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Mitigating the Interference Caused by Pilot Contamination in Multi-cell Massive Multiple Input Multiple Output Systems Using Low Density Parity Check Codes in Uplink Scenario

Traitement du signal ◽

10.18280/ts.370619 ◽

2020 ◽

Vol 37 (6) ◽

pp. 1061-1074

Author(s):

Lokesh Bhardwaj ◽

Ritesh Kumar Mishra

Keyword(s):

Mimo System ◽

Multiple Input Multiple Output ◽

Base Station ◽

Low Density ◽

Pilot Contamination ◽

Parity Check ◽

Low Density Parity Check ◽

Multiple Input ◽

Input Multiple Output ◽

Sum Rate

The effects of pilot contamination (PC) on the performance of multi-cell multi-user massive multiple input multiple output (MC-MU-m-MIMO) system in uplink has been analyzed in this article. In a multi-cell scenario, the channel estimation (CE) at the desired cell using pilot reuse to avoid significant overhead results in poor CE due to PC. The improvement in degraded performance due to the effect of PC has been shown using low Density Parity Check (LDPC) codes. The comparative analysis of performance in terms of variation in bit error rate (BER) with the signal to noise ratio (SNR) for LDPC coded and uncoded information blocks of users has been shown when the number of cells sharing the same frequency band is varied. Further, the expression for sum-rate has been derived and its variation with the number of base station (BS) antennas has also been shown. The simulated results have shown that the LDPC coded scheme performs better than the uncoded counterpart and the sum-rate capacity increases when the strength of channel coefficients between the BS antennas of the desired cell and the users of remaining cells is less.

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Sum-Rate of Multi-User MIMO Systems with Multi-Cell Pilot Contamination in Correlated Rayleigh Fading Channel

Entropy ◽

10.3390/e21060573 ◽

2019 ◽

Vol 21 (6) ◽

pp. 573 ◽

Cited By ~ 3

Author(s):

Menghan Wang ◽

Dongming Wang

Keyword(s):

Rayleigh Fading ◽

Gaussian Approximation ◽

Mimo Systems ◽

Mimo System ◽

Multiple Input Multiple Output ◽

Moment Generating Function ◽

Base Station ◽

Pilot Contamination ◽

Input Multiple Output ◽

Sum Rate

This paper presents some exact results on the sum-rate of multi-user multiple-input multiple-output (MU-MIMO) systems subject to multi-cell pilot contamination under correlated Rayleigh fading. With multi-cell multi-user channel estimator, we give the lower bound of the sum-rate. We derive the moment generating function (MGF) of the sum-rate and then obtain the closed-form approximations of the mean and variance of the sum-rate. Then, with Gaussian approximation, we study the outage performance of the sum-rate. Furthermore, considering the number of antennas at base station becomes infinite, we investigate the asymptotic performance of the sum-rate. Theoretical results show that compared to MU-MIMO system with perfect channel estimation and no pilot contamination, the variance of the sum-rate of the considered system decreases very quickly as the number of antennas increases.

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Sum Rate Analysis of MU-MIMO with a 3D MIMO Base Station Exploiting Elevation Features

International Journal of Antennas and Propagation ◽

10.1155/2015/318123 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9 ◽

Cited By ~ 10

Author(s):

Xingwang Li ◽

Lihua Li ◽

Fupeng Wen ◽

Junfeng Wang ◽

Chao Deng

Keyword(s):

Channel Model ◽

Mimo Systems ◽

Multiple Input Multiple Output ◽

Three Dimensional ◽

Base Station ◽

Rate Performance ◽

High Rise ◽

Rate Analysis ◽

Input Multiple Output ◽

Sum Rate

Although the three-dimensional (3D) channel model considering the elevation factor has been used to analyze the performance of multiuser multiple-input multiple-output (MU-MIMO) systems, less attention is paid to the effect of the elevation variation. In this paper, we elaborate the sum rate of MU-MIMO systems with a 3D base station (BS) exploiting different elevations. To illustrate clearly, we consider a high-rise building scenario. Due to the floor height, each floor corresponds to an elevation. Therefore, we can analyze the sum rate performance for each floor and discuss its effect on the performance of the whole building. This work can be seen as the first attempt to analyze the sum rate performance for high-rise buildings in modern city and used as a reference for infrastructure.

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Multiple input multiple output (MIMO) and fifth generation (5G): an indispensable technology for sub-6 GHz and millimeter wave future generation mobile terminal applications

International Journal of Microwave and Wireless Technologies ◽

10.1017/s1759078721001100 ◽

2021 ◽

pp. 1-17

Author(s):

Insha Ishteyaq ◽

Khalid Muzaffar

Keyword(s):

Mutual Coupling ◽

Multiple Input Multiple Output ◽

Future Generation ◽

Mobile Terminal ◽

Base Station ◽

Base Stations ◽

Mimo Antenna ◽

Reduction Techniques ◽

Input Multiple Output ◽

Almost All

Abstract The in-depth exploration in the future 5G technology symbolizes a revolution in technology for antenna designers to encounter the all time increasing need as well as demand for higher data rate wireless communications. The paper gives out an exhaustive review of the evolution and characteristics of the 5G spectrum allocations, the MIMO antenna design with regard to mutual coupling reduction techniques and safer user applications. It precisely covers almost all the aspects of 5G which mainly include the types of antenna designs and their performance parameters related to MIMO design. The paper also presents a brief description of massive MIMO technology for base station applications. The main aim of the paper is: (1) to emphasize the frequencies allocated for the 5G including sub-6 Ghz and mm-wave bands; (2) to underline the suitable antenna designs for MIMO applications for mobile devices and base stations; (3) to highlight the mutual coupling effects in MIMO designs and its reduction techniques; (4) to consider the gaps in the literature and the challenges for reducing SAR effects for the safety of the users. This review paper has been an attempt to explore the evolution of 5G bands and antenna designs for 5G applications, comparison based on the literature, and the techniques implemented for enhancing the MIMO antenna performances.

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Utility-Based Wireless Routing Algorithm for Massive MIMO Heterogeneous Networks

Applied Sciences ◽

10.3390/app10207261 ◽

2020 ◽

Vol 10 (20) ◽

pp. 7261

Author(s):

Wei Zhao ◽

Wen-Hsing Kuo

Keyword(s):

Heterogeneous Networks ◽

Massive Mimo ◽

Routing Algorithm ◽

Multiple Input Multiple Output ◽

Base Station ◽

Base Stations ◽

Small Cells ◽

Multihop Wireless ◽

Wireless Backhaul ◽

Input Multiple Output

With the development of 5G communication, massive multiple input multiple output (MIMO) technology is getting more and more attention. Massive MIMO uses a large amount of simultaneous transmitting and receiving antennas to reduce power consumption and raise the level of transmission quality. Meanwhile, the diversification of user equipment (UE) in the 5G environment also makes heterogeneous networks (HetNets) more prevalent. HetNets allow UE of different network standards to access small cells, while the base stations of small cells access a macro base station (BS) to form a multihop wireless heterogeneous backhaul network. However, how to effectively combine these two technologies by efficiently allocating the antennas of each BS during the route construction process of heterogeneous wireless backhaul networks is still an important issue that is yet to be solved. In this paper, we propose an algorithm called preallocated sequential routing (PSR). Based on the links’ channel conditions and the available antennas and location of BSs, it builds a wireless heterogeneous network backhaul topology and adjusts each link’s transmitting and receiving antennas to maximize total utility. Simulation results showed that the proposed algorithm significantly improved the overall utility and the utility of the outer area of heterogeneous networks.

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Multi-User Linear Equalizer and Precoder Scheme for Hybrid Sub-Connected Wideband Systems

Electronics ◽

10.3390/electronics8040436 ◽

2019 ◽

Vol 8 (4) ◽

pp. 436 ◽

Cited By ~ 2

Author(s):

Daniel Castanheira ◽

Sara Teodoro ◽

Ricardo Simões ◽

Adão Silva ◽

Atilio Gameiro

Keyword(s):

Millimeter Waves ◽

Multiple Input Multiple Output ◽

Low Complexity ◽

Merit Function ◽

Base Station ◽

Linear Equalizer ◽

Input Multiple Output ◽

Narrowband Channels ◽

Fully Connected ◽

User Interference

Millimeter waves and massive multiple-input multiple output (MIMO) are two promising key technologies to achieve the high demands of data rate for the future mobile communication generation. Due to hardware limitations, these systems employ hybrid analog–digital architectures. Nonetheless, most of the works developed for hybrid architectures focus on narrowband channels, and it is expected that millimeter waves be wideband. Moreover, it is more feasible to have a sub-connected architecture than a fully connected one, due to the hardware constraints. Therefore, the aim of this paper is to design a sub-connected hybrid analog–digital multi-user linear equalizer combined with an analog precoder to efficiently remove the multi-user interference. We consider low complexity user terminals employing pure analog precoders, computed with the knowledge of a quantized version of the average angles of departure of each cluster. At the base station, the hybrid multi-user linear equalizer is optimized by using the bit-error-rate (BER) as a metric over all the subcarriers. The analog domain hardware constraints, together with the assumption of a flat analog equalizer over the subcarriers, considerably increase the complexity of the corresponding optimization problem. To simplify the problem at hand, the merit function is first upper bounded, and by leveraging the specific properties of the resulting problem, we show that the analog equalizer may be computed iteratively over the radio frequency (RF) chains by assigning the users in an interleaved fashion to the RF chains. The proposed hybrid sub-connected scheme is compared with a fully connected counterpart.

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In Situ Assessment of 5G NR Massive MIMO Base Station Exposure in a Commercial Network in Bern, Switzerland

Applied Sciences ◽

10.3390/app11083592 ◽

2021 ◽

Vol 11 (8) ◽

pp. 3592

Author(s):

Sam Aerts ◽

Kenneth Deprez ◽

Davide Colombi ◽

Matthias Van den Bossche ◽

Leen Verloock ◽

...

Keyword(s):

Multiple Input Multiple Output ◽

Input Power ◽

Base Station ◽

Base Stations ◽

Traffic Load ◽

Reference Level ◽

Exposure Level ◽

Input Multiple Output ◽

The Impact ◽

Antenna Input

This paper describes the assessment of radiofrequency (RF) electromagnetic field (EMF) exposure from fifth generation (5G) new radio (NR) base stations in a commercial NR network in Bern, Switzerland. During the measurement campaign, four base station sites were investigated and the exposure induced by the NR massive multiple-input-multiple-output (MaMIMO) antennas was assessed at 22 positions, at distances from the base station between 30 m and 410 m. The NR base stations operated at 3.6 GHz and used codebook-based beamforming. While the actual field levels without inducing downlink traffic were very low (<0.05 V/m) due to a low traffic load and low antenna input powers of up to 8 W, setting up a maximum downlink traffic stream towards user equipment resulted in a time-averaged exposure level of up to 0.4 V/m, whereas the maximum extrapolated exposure level reached 0.6 V/m. Extrapolated to an antenna input power of 200 W, values of 4.3 V/m and 4.9 V/m, respectively, were obtained, which amount to 0.5–0.6% of the reference level recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). In Bern, it was found that the impact of the NR network on the total environmental RF exposure was very limited; with maximum downlink, it contributed 2% on average. Finally, it was also concluded that extrapolation to the maximum exposure level can be done without prior knowledge of the radiation patterns, directly based on the measurement of the Physical Downlink Shared Channel (PDSCH) resource elements.

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Implementation of a Zero-Forcing Precoding Algorithm Combined with Adaptive Beamforming Based on WiMAX System

International Journal of Antennas and Propagation ◽

10.1155/2013/976301 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Hyunwook Yang ◽

Seungwon Choi

Keyword(s):

Mimo System ◽

Multiple Input Multiple Output ◽

Experimental System ◽

Multiple Access Interference ◽

Adaptive Beamforming ◽

Base Station ◽

Zero Forcing ◽

Single Antenna ◽

Input Multiple Output ◽

Wimax System

We propose a novel precoding algorithm that is a zero-forcing (ZF) method combined with adaptive beamforming in the Worldwide Interoperability for Microwave Access (WiMAX) system. In a Multiuser Multiple-Input Multiple-Output (MU-MIMO) system, ZF is used to eliminate the Multiple Access Interference (MAI) in order to allow several users to share a common resource. The adaptive beamforming algorithm is used to achieve the desired SNR gain. The experimental system consists of a WiMAX base station that has 2 MIMO elements, each of which is composed of three-array antennas and two mobile terminals, each of which has a single antenna. Through computer simulations, we verified that the proposed method outperforms the conventional ZF method by at least 2.4 dB when the BER is 0.1%, or 1.7 dB when the FER is 1%, in terms of the SNR. Through a hardware implementation of the proposed method, we verified the feasibility of the proposed method for realizing a practical WiMAX base station to utilize the channel resources as efficiently as possible.

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Study of 5G-NR-MIMO Links in the Presence of an Interferer

Electronics ◽

10.3390/electronics10060732 ◽

2021 ◽

Vol 10 (6) ◽

pp. 732

Author(s):

Avner Elgam ◽

Yael Balal ◽

Yosef Pinhasi

Keyword(s):

Mobile Networks ◽

Communication Systems ◽

Multiple Input Multiple Output ◽

Local Area ◽

Maximum Energy ◽

Base Station ◽

Small Cells ◽

Diversity Coding ◽

Shift Keying ◽

Input Multiple Output

Many communication systems are based on the Multiple Input, Multiple Output (MIMO) scheme, and Orthogonal Space–time Block Transmit diversity Coding (OSTBC), combined with Maximal Ratio Receive Combining (MRRC), to create an optimal diversity system. A system with optimal diversity fixes and optimizes the channel’s effects under multi-path and Rayleigh fading with maximum energy efficiency; however, the challenge does not end with dealing with the channel destruction of the multi-path impacts. Susceptibility to interference is a significant vulnerability in future wireless mobile networks. The 5th Generation New Radio (5G-NR) technologies bring hundreds of small cells and pieces of User Equipment (UE) per indoor or outdoor local area scenario under a specific Long Term Evolution (LTE)-based station (e-NodeB), or under 5G-NR base-station (g-NodeB). It is necessary to study issues that deal with many interference signals, and smart jammers from advanced communication equipment cause deterioration in the links between the UE, the small cells, and the NodeB. In this paper, we study and present the significant impact and performances of 2×2 Alamouti Phase-Shift Keying (PSK) modulation techniques in the presence of an interferer and a smart jammer. The destructive effects affecting the MIMO array and the advanced diversity technique without closed-loop MIMO are analyzed. The performance is evaluated in terms of Bit Error Rate (BER) vs. Signal to Interference Ratio (SIR). In addition, we proved the impairment of the orthogonal spectrum assumption mathematically.

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