Jiyun Shen

Joint fixed beamforming and eigenmode precoding for super high bit rate massive MIMO systems using higher frequency bands

In order to tackle rapidly increasing traffic, the 5th generation (5G) mobile communication system will introduce small cells using higher frequency bands with wider bandwidth to achieve super high bit rate transmission of several tens Gbps. Massive MIMO beamforming (BF) is one of promising technologies to compensate for larger path-loss in the higher frequency bands. Joint analog fixed BF and digital precoding has been proposed to reduce the cost of a Massive MIMO transceiver. However, the conventional scheme assumes the transmission of a few streams using well-known codebook-based precoding as the digital precoding, and both a selection method of the fixed BF weights and a digital precoder design, which are suitable for the super high bit rate transmission using multiple streams, have not been studied. This paper proposes a joint fixed BF and CSI-based precoding (called FBCP) scheme for the 5G Massive MIMO systems. FBCP first selects the analog fixed BF weights based on maximum total received power criterion, and then it calculates eigenmode (EM) precoding matrix exploiting CSI. This paper targets a 5G system achieving 20 Gbps in 20 GHz band as one example, and throughput performances of the proposed FBCP are evaluated by link level simulation and compared with those of the fixed BF and those of the EM precoding.

A Novel Approach for Capacity Improvement of 2x2 MIMO in LOS Channel Using Reflectarray

Multiple-input multiple-output (MIMO) transmission schemes with a high radio frequency are expected to make ultra high-rate mobile communications practical due to their high frequency utilization efficiency. On the other hand, since the high radio frequency incurs a large propagation loss that results in a contraction of the service area, there is an increase in the probability of a line-of-sight (LOS) environment. There is a significant degradation in terms of channel capacity in the MIMO transmission in a LOS channel and this is a considerable issue. This paper introduces a novel approach for improving the channel capacity of MIMO transmission in a LOS channel by employing a simple reflectarray within the LOS channel. We also perform an analysis of the eigenvalue and condition number for a 2x2 MIMO pure LOS channel matrix when using a reflectarray. The computer simulation results for the 2x2 LOS-MIMO channel show remarkable improvement in the condition number and the maximum increase of almost double the channel capacity when establishing one reflectarray within the LOS channel.

Super high bit rate radio access technologies for small cells using higher frequency bands

This paper overviews super high bit rate radio access technologies using higher frequency bands for future radio access for 5G. In small cells using higher frequency bands based on the Phantom Cell concept in which radio links for the control (C)-plane and user (U)-plane are separately connected to a macro cell and small cell, radio access technologies employing Massive Multiple-Input Multiple-Output (MIMO) are described that achieve super high bit rate transmission. Specifically, on the basis of 11 GHz band 8×16 MIMO and 24×24 MIMO preliminary investigations, we estimate the required transmission power for 20 Gbps transmission in 20 GHz band Massive MIMO. In addition, we show the basic performance of 20 GHz band Massive MIMO based on link level simulations.

Design of wide angle reflection reflectarray using multi-layer mushroom structure to improve propagation

This paper proposes a multi-layer mushroom reflectarray to achieve a wide angle of reflection (AOR) reflectarray at a super high frequency that can be used to improve the Multiple-In-Multiple-Out capacity in a line-of-sight environment. The paper also presents a detailed design chart to satisfy the desired AOR by applying LC resonant circuit theory. A 70 degree-AOR reflectarray at 11 GHz is designed and the proposed reflectarray exhibits good performance based on Finite Element Method calculations.

11 GHz Band 8×16 MIMO-OFDM outdoor transmission experiment for 10 Gbps super high bit rate mobile communications

This paper presents detailed results of 11 GHz band outdoor transmission experiments employing 8 × 16 MIMO-OFDM for 10 Gbps super high bit rate mobile communications. Super high bit rate mobile communications have been studied for future mobile communications, and to verify the feasibility, outdoor transmission experiments were performed. A mobile station (MS) with 8 transmitter antennas traveled along a measurement course while a base station (BS) with 16 receiver antennas stored the received signals, and then the throughput performance levels were evaluated by demodulating them in an off-line mode. This paper introduces specifications and a hardware configuration for the 11 GHz band 8×16 MIMO-OFDM experimental system with a signal bandwidth of 400 MHz. In addition, it presents the SNR distribution and delay spread that are calculated from the received signals in the measurement course used in the outdoor experiments. The experimental results show that for 11.8 Gbps transmission with 8 streams, 64QAM, and the coding rate of 3/4, throughput of greater than 10 Gbps is achieved in an 11 GHz band outdoor mobile environment.

Evaluation of 30 Gbps super high bit rate mobile communications using channel data in 11 GHz band 24×24 MIMO experiment

The performance of 30 Gbps super high bit rate mobile communications is evaluated by computer simulation using channel data collected in 11 GHz band 24×24 MIMO outdoor propagation experiments, and the feasibility of 11 GHz band 30 Gbps transmission is verified. To achieve the super high bit rate mobile communications, 10 Gbps transmission using 11 GHz band 8×16 MIMO has been verified in outdoor transmission experiments. In addition, channel measurement and analysis have been conducted in 11 GHz band 24×24 MIMO radio propagation experiments. Although 24×24 MIMO transmission is expected to achieve a bit rate exceeding 30 Gbps, transmission experiments have not yet been performed due to the hardware limitations. In this paper, computer simulations based on 24×24 MIMO-OFDM eigenmode transmission are conducted by utilizing channel data measured using an 11 GHz band 24×24 MIMO channel sounder. This paper shows that throughput exceeding 30 Gbps is achieved in 11 GHz band mobile environments, and clarifies the requirements for the average signal-to-noise ratio, channel conditions, and accuracy of channel state information to achieve 30 Gbps throughput over a real 11 GHz band 24×24 MIMO channel.

Direction estimation for cellular enhanced cell-ID positioning using multiple sector observations

In this paper, we propose a method that estimates the direction of a set of User Equipment (UE) more accurately for Enhanced Cell-ID (ECID) positioning of a cellular system than the conventional sector based positioning method. The proposed method estimates the direction of the UE using the number of observations in reception sectors. The average received power ratio of the reception sectors is calculated using the observation results of the sector reception situation and antenna patterns of the reception sector are used to estimate the UE direction. This enables estimation of the direction from simply obtained information. The evaluation results of the proposed method are presented based on computer simulations of the direction accuracy and positioning accuracy. The improvement in the direction accuracy compared to the conventional method is approximately 65% (11°) in a Rayleigh fading environment when the number of observations is 10 and the width of sector is 60°. Round Trip Time (RTT) positioning accuracy is improved by approximately 50% (150 m) using the proposed method when the error in the RTT measurement is 156 m and the cell spacing is 4 km.

Analysis and design of metamaterial reflectarray using combination of multilayer mushroom-structure

We have previously proposed to use reflectarrays to eliminate blind zones in a propagation area of very high-speed wireless communication systems [1 – 4] and have shown that one candidate of such reflectarrays is metamaterial reflectarray which has mushroom structure [3 – 4]. The reflection phase of mushroom structure can be calculated applying a parallel resonant circuit model with inductance L and capacitance C [5]. The value of reflection phase is equal to zero at LC resonant frequency and the value of reflection phase at given frequency is changed using inductance L and capacitance C because the resonant frequency is changed by these. There are typically three control methods [5–8] for L and C changing. The first method employs varactor diodes and changing the voltage [5], the second method changes the resonant frequency depending on the position of the mushroom structure [8], and the third involves changing the patch length of the mushroom structure to achieve a difference in capacitance [6, 7]. Although, it is necessary to achieve a reflection phase range from + π to - π at the desired frequency for the strict design of a reflectarray, it is difficult to achieve this because of manufacturing limitation. On the other hand, a multi-layered mushroom structure is used to increase the capacitance in order to achieve low frequency resonance [10]. To address this issue, this paper proposes novel metamaterial reflectarray which has combination of multi-layer mushroom structures and can achieve arbitrary desired inductance L and capacitance C. Since the value of Inductance L is determined by patch height from ground plane, we adopt several kind of thicknesses for substrate and combine them. To eliminate manufacturing difficulty when we make patches closer to each other for achieving large capacitance value, we slightly change adjacent patches height using multi-layer structure. By using proposed method, we design 45 degree beam control reflectarray. Theoretical result using LC resonant circuit model agrees with simulation result using finite element method.

Capacitance value control for metamaterial reflectarray using multi layer mushroom-structure with parasitic element

This paper proposes novel reflectarray design using multi layer mushroom structure with parasitic element based on capacitance value control of LC resonant circuit model. From the study of LC resonant circuit model, this paper shows the parallel setting capacitance value can be theoretically controled by that the parasitic layer number. Next, this paper shows novel reflectarray design method for −70 degree vertical beam control mushroom reflectarray for vertical polarization by focusing on capacitance value. Finally, this paper shows proposed design has good performance and both simulated and experiment results shows good agreement.

Multi-band reflectarray using mushroom structure

This paper shows a study of the multiband mushroom reflectarray design. We have achieved multi-band reflectarray to satisfy desired reflection phase, using TE incidence for low frequency and TM incidence for high frequency and changing two directional gap sizes corresponding to each polarization. We show the reflectarray that can reflects same direction for same incidence direction at dual frequencies.