Beamspace Multiple-input Multiple-output Systems Research Articles

Joint RF Precoding and Beam Selection Design for Uplink mmWave Beamspace MIMO Systems

Phase-only radio frequency (RF) precoding and lens antenna array-based beam selection are two promising low-hardware-cost technologies for millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems. This letter aims to jointly design users’ RF precoders and base station’s beam selection network to maximize the uplink sum rate (SR) of mmWave MIMO systems. For the sake of tackling the formulated mixed-integer optimization problem, a fractional programming-based iterative algorithm is developed via capitalizing on the Riemannian gradient (RG)-based and penalty-based methods. In addition, a low-complexity algorithm is proposed at the expense of a slight SR performance loss, which combines the stepwise refinement-based beam selection scheme with the RG approach. The convergence of the proposed algorithms are discussed and their effectiveness is illustrated by numerical results.

Wireless Power Transfer by Beamspace Large-Scale MIMO With Lens Antenna Array

In this paper, we study wireless power transfer (WPT) using the discrete lens array-based beamspace large-scale multiple-input multiple-output (MIMO) system. The channel matrix of beamspace MIMO exhibits sparse property, which enables the transmitter to employ only a small number of active antennas while maintaining the full MIMO performance. Hence, the number of radio frequency (RF) chains can be significantly reduced, cutting the cost of hardware implementation and circuit power consumption. We consider two WPT design problems in the beamspace MIMO system with constraints on the number of RF chains: the sum power transfer and the max–min power transfer problems; and for each problem, we consider both multi-stream and uni-stream transmissions. For the sum power transfer problem, we show that the uni-stream power transfer achieves the same performance as the multi-stream case, and we propose two algorithms for the uni-stream transmission, namely, an eigendecomposition-based greedy algorithm and a truncated power iteration algorithm. For the max–min power transfer problem, we propose a semidefinite relaxation-based greedy algorithm for the multi-stream power transfer and a Riemannian conjugate gradient algorithm for the uni-stream case. The simulation results show that with a small number of RF chains, the beamspace MIMO system significantly outperforms the conventional MIMO system in terms of WPT efficiency.

Spectrum and Energy-Efficient Beamspace MIMO-NOMA for Millimeter-Wave Communications Using Lens Antenna Array

The recent concept of beamspace multiple input multiple output (MIMO) can significantly reduce the number of required radio frequency (RF) chains in millimeter-wave (mmWave) massive MIMO systems without obvious performance loss. However, the fundamental limit of existing beamspace MIMO is that the number of supported users cannot be larger than the number of RF chains at the same time-frequency resources. To break this fundamental limit, in this paper, we propose a new spectrum and energy-efficient mmWave transmission scheme that integrates the concept of non-orthogonal multiple access (NOMA) with beamspace MIMO, i.e., beamspace MIMO-NOMA. By using NOMA in beamspace MIMO systems, the number of supported users can be larger than the number of RF chains at the same time-frequency resources. In particular, the achievable sum rate of the proposed beamspace MIMO-NOMA in a typical mmWave channel model is analyzed, which shows an obvious performance gain compared with the existing beamspace MIMO. Then, a precoding scheme based on the principle of zero forcing is designed to reduce the inter-beam interferences in the beamspace MIMO-NOMA system. Furthermore, to maximize the achievable sum rate, a dynamic power allocation is proposed by solving the joint power optimization problem, which not only includes the intra-beam power optimization, but also considers the inter-beam power optimization. Finally, an iterative optimization algorithm with low complexity is developed to realize the dynamic power allocation. Simulation results show that the proposed beamspace MIMO-NOMA can achieve higher spectrum and energy efficiency compared with the existing beamspace MIMO.

Channel estimation for interference mitigation in millimeter-wave multi-cell beamspace MIMO systems

This paper deals with the inter-cell interference (ICI) mitigation in the channel estimation process of millimeter-wave multi-cell beamspace multiple-input multiple-output systems. The known channel estimation approaches cannot distinguish the ICI channels and the in-cell channels. In contrast, the in-cell channels and the ICI channels are estimated together and distinguished with the beam information in this paper. In addition, the beamspace channels are estimated with small error by utilizing the asymptotic property of the beamspace channels. As a result, the ICI can be efficiently suppressed. Performance analysis and numerical results show that the proposed approach outperforms the existing channel estimation approaches.

Antenna Tilt Design for Millimeter-Wave Beamspace MIMO Systems

A joint design of the mechanical and the electrical tilts is proposed for millimeter-wave beamspace multiple-input multiple-output systems. Based on the correlation property of the array steering vector, the asymptotic sum rate is derived. In order to maximize the sum rate, the mechanical tilt is designed to maximize the expectations of the antenna gains. Moreover, the electrical tilt is dynamically adjusted to optimize the instantaneous antenna gains. As a result, the proposed joint design of two tilts can achieve higher sum rate than the designs of one tilt, which is confirmed by the simulation results.

Design and Beamforming Performance of the Compact ESPAR Antenna for the Beam Space MIMO System

Multiple-input multiple-output (MIMO) system is essential to wireless and mobile communication for the higher channel capacity. However, this MIMO system requires many active RF (radio frequency) stages, and is very difficult to be used in mobile devices. It produces the high energy consumption at RF stage as well as the high hardware complexity. Especially, it will be more serious in the massive MIMO system that is strongly considered as an enabling technology for the 5G mobile communication system. In order to solve this problem, beam-space MIMO (BS-MIMO) systems were proposed using the electronically steerable parasitic array radiator (ESPAR) antenna, which work as the MIMO system using single RF stage with many passive parasitic elements. However, there are some limits in this ESPAR based BS-MIMO system because of this many passive parasitic elements. The conventional BS-MIMO system basically uses two parasitic elements for one dimension of MIMO. So, in this paper we like to propose a design method for reducing the passive elements number in this BS-MIMO system. In the proposed system, we cut down the number of the parasitic elements into half. So, the proposed BS-MIMO system uses one parasitic element for one dimension of MIMO. To design 8 ? 8 MIMO system, only eight elements of parasitic elements are needed instead of 16 elements in conventional design. Since this proposed ESPAR based BS-MIMO system requires only the half number of parasitic elements, we can design more compact ESPAR antenna design. Also, we can easily increase the MIMO dimension with compact size by this proposed ESPAR antenna. Simulation results can confirm that the proposed ESPAR BS-MIMO system with half number of elements keeps the very similar performance of the conventional system and acceptable beamforming performance as well. This proposed system could be very useful for the massive MIMO system design for the 5G mobile communication.

빔공간 MIMO 시스템에 기반한 OFDM 전송방법

Beamspace Multiple-Input Multiple Output(MIMO) system can transmit multiple data by using Electronically Steerable Parasitic Array Radiator(ESPAR) antenna which has single Radio Frequency(RF)-chain. Beamspace MIMO system can reduce complexity of the system and size of antenna in comparison with the conventional MIMO system because of characteristic of ESPAR antenna using the single antenna and the RF-chain. Heretofore, only the research of transmitting single-carrier has been conducted by the use of beamspace MIMO system. Therefore, in this paper, we propose beamspace MIMO system based on Orthogonal Frequency Division Multiplexing(OFDM) for transmitting the multi-carrier and analysis the performance of this system. We find a proper reactance value which has good performance because proposed system changes the performance by the reactance values of parasitic elements. and we confirm that performance of the proposed system is similar to conventional MIMO system based on OFDM. 논문 15-40-03-02 The Journal of Korean Institute of Communications and Information Sciences '15-03 Vol.40 No.03 http://dx.doi.org/10.7840/kics.2015.40.3.425 425 ※ 이 논문은 2012년도 정부(교육과학기술부)의 재원으로 한국연구재단의 지원을 받아 수행된 기초연구사업임(No. 2012017339) 그리 고 이 논문은 2013년도 정부(교육과학기술부)의 재원으로 한국연구재단의 지원을 받아 수행된 기초연구사업임(No.2013R1A2A2A01 005849) 그리고 본 연구는 미래창조과학부 및 정보통신기술진흥센터의 정보통신·방송 연구개발 사업의 일환으로 수행하였음(14-000 -04-001, 고집적 Compact MIMO 안테나 개발). First Author : Smart Radio Research Team, Electronics and Telecommunications Research Institute, jkchoi@etri.re.kr, 정회원 ° Corresponding Author : Department of electronics engineering, Chungbuk National University, ecomm@cbu.ac.kr, 정회원 * Department of electronics engineering, Chungbuk National University, acy890217@naver.com, 학생회원 논문번호:KICS2014-10-438, Received October 30, 2014; Revised March 2, 2015; Accepted March 2, 2015 The Journal of Korean Institute of Communications and Information Sciences '15-03 Vol.40 No.03

ESPAR 안테나에서 M×M MIMO 송신방식의 설계와 성능 평가

본 논문에서는 ESPAR(Electronically Steerable Parasitic Array Radiator) 안테나를 이용한 <TEX>$M{\times}M$</TEX> BS-MIMO(beam space multiple input multiple output) 시스템을 제안한다. 기존 MIMO 시스템은 전송 데이터 신호를 다수의 안테나에 맵핑시켜 전송하기 때문에 다수의 RF 체인이 필요한 문제점이 있다. 다수의 RF 체인은 하드웨어의 비용을 및 RF 회로의 전력 소모를 증가 시킨다. 또한, 휴대폰과 같이 공간적인 제약이 큰 모바일 장비에서 MIMO 시스템을 사용하기 어렵다. 이러한 문제를 해결하기 위해서 단일 RF 체인을 가지는 ESPAR 안테나를 사용하여 빔 공간에서 신호를 맵핑시키는 BS-MIMO 시스템이 제안되었다. 본 논문에서는 BS-MIMO 시스템 기법에 대해서 설명하고 이를 확장한 <TEX>$M{\times}M$</TEX> BS-MIMO 전송 기법의 설계 및 성능을 분석한다. 컴퓨터 모의실험을 통한 성능 확인 결과 제안된 BS-MIMO 전송기법은 기존 MIMO 기법과 비교하여 거의 동일한 수신 BER 성능을 얻는다. 따라서 다수의 RF 체인을 가지는 기존 MIMO 시스템과 비교하여 BS-MIMO 시스템은 단일 RF 체인을 가지고 MIMO 전송이 가능하며, 이로 인해서 하드웨어 비용 및 RF 회로의 전력 소모를 획기적으로 줄일 것으로 예상된다. In this paper, we propose a <TEX>$M{\times}M$</TEX> beam-space multiple input multiple output (BS-MIMO) system using electronically steerable parasitic array radiator (ESPAR) antenna. Conventional MIMO method required multiple RF chains because it map the transmission signals onto multiple antennas. So, conventional MIMO system has high cost for design and high energy consumption at RF circuit. Also, It is difficult to use MIMO system in battery based mobile terminals with limited physical area. In order to solve these problems, BS-MIMO technique which map the data signal onto bases in beam space domain was proposed using ESPAR antenna with single RF chain. This paper, we design and analyze the performance of extended <TEX>$M{\times}M$</TEX> BS-MIMO technique. Simulation results show that the proposed BS-MIMO system has similar BER performance compare to conventional MIMO scheme. Therefore, BS-MIMO system with single RF chain will has a low RF power consumption and low cost for RF hardware design as compared with conventional MIMO technique with multiple RF chains.