Yuichi Kakishima

5G 3GPP-Like Channel Models for Outdoor Urban Microcellular and Macrocellular Environments

For the development of new 5G systems to operate in bands up to 100 GHz, there is a need for accurate radio propagation models at these bands that currently are not addressed by existing channel models developed for bands below 6 GHz. This document presents a preliminary overview of 5G channel models for bands up to 100 GHz. These have been derived based on extensive measurement and ray tracing results across a multitude of frequencies from 6 GHz to 100 GHz, and this document describes an initial 3D channel model which includes: 1) typical deployment scenarios for urban microcells (UMi) and urban macrocells (UMa), and 2) a baseline model for incorporating path loss, shadow fading, line of sight probability, penetration and blockage models for the typical scenarios. Various processing methodologies such as clustering and antenna decoupling algorithms are also presented.

Indoor 5G 3GPP-like channel models for office and shopping mall environments

Future mobile communications systems are likely to be very different to those of today with new service innovations driven by increasing data traffic demand, increasing processing power of smart devices and new innovative applications. To meet these service demands the telecommunications industry is converging on a common set of 5G requirements which includes network speeds as high as 10 Gbps, cell edge rate greater than 100 Mbps, and latency of less than 1 msec. To reach these 5G requirements the industry is looking at new spectrum bands in the range up to 100 GHz where there is spectrum availability for wide bandwidth channels. For the development of new 5G systems to operate in bands up to 100 GHz there is a need for accurate radio propagation models which are not addressed by existing channel models developed for bands below 6 GHz. This paper presents a preliminary overview of the 5G channel models for bands up to 100 GHz in indoor offices and shopping malls, derived from extensive measurements across a multitude of bands. These studies have found some extensibility of the existing 3GPP models (e.g. 3GPP TR36.873) to the higher frequency bands up to 100 GHz. The measurements indicate that the smaller wavelengths introduce an increased sensitivity of the propagation models to the scale of the environment and show some frequency dependence of the path loss as well as increased occurrence of blockage. Further, the penetration loss is highly dependent on the material and tends to increase with frequency. The small-scale characteristics of the channel such as delay spread and angular spread and the multipath richness is somewhat similar over the frequency range, which is encouraging for extending the existing 3GPP models to the wider frequency range. Further work will be carried out to complete these models, but this paper presents the first steps for an initial basis for the model development.

3D channel model in 3GPP

Multi-antenna techniques capable of exploiting the elevation dimension are anticipated to be an important air-interface enhancement targeted to handle the expected growth in mobile traffic. In order to enable the development and evaluation of such multi-antenna techniques, the 3rd Generation Partnership Project (3GPP) has recently developed a three-dimensional (3D) channel model. The existing two-dimensional (2D) channel models do not capture the elevation channel characteristics, making them insufficient for such studies. This article describes the main components of the newly developed 3D channel model and the motivations behind introducing them. One key factor is the ability to model channels for users located on different floors of a building (at different heights). This is achieved by capturing a user height dependency in modelling some channel characteristics including pathloss, lineof- sight (LOS) probability, etc. In general, this 3D channel model follows the framework of WINNERII/WINNER+ while also extending the applicability and the accuracy of the model by introducing some height dependent and distance dependent elevation related parameters.

Experimental evaluations on carrier aggregation and multi-user MIMO associated with EVD-based CSI feedback for LTE-Advanced downlink

This paper presents laboratory experimental results on 4-by-2 multi-user (MU)-MIMO multiplexing with two mobile stations (MSs) in the LTE-Advanced downlink in combination with carrier aggregation (CA) using 5 component carriers (CCs). Extended channel state information (CSI) feedback functionality based on eigenvalue decomposition (EVD) is implemented into real-time experimental equipment based on the LTE-Advanced radio interface to support MU-MIMO operations applying minimum mean square error (MMSE)-based precoding. Laboratory experiments are conducted assuming a multi-path fading environment based on different antenna configurations. The experimental results show that 4-by-2 MU-MIMO with two data streams per MS achieves a peak throughput of greater than 950 Mbps, i.e., nearly 1 Gbps, in a correlated antenna configuration scenario when the maximum Doppler frequency is 10 Hz and the propagation channel model with the root mean squared delay spread is 0.3 μsec. The results also show that, high throughput performance such as greater than 750 Mbps for 4-by-2 MU-MIMO with two data streams per MS is acheived even in a non-correlated antenna configuration scenario although the environment is limited to low mobility and a small delay spread.

Experimental Evaluation on Throughput Performance of Asymmetric Carrier Aggregation in LTE-Advanced

This paper presents laboratory experimental results on the throughput performance of asymmetric carrier aggregation between the uplink and downlink using an LTE-Advanced testbed. The implemented base station (BS) and mobile station (MS) transceivers have transmission bandwidth capability of up to 100 MHz (5 component carriers (CCs)) and 40 MHz (2 CCs) in the downlink and uplink, respectively. The testbed also features CC-specific adaptive modulation and channel coding (AMC) and hybrid automatic repeat request (HARQ) functionalities based on the actually transmitted control signaling. The experimental results show that, in the uplink, CC-based AMC using up to 64QAM high-order modulation is effective in increasing the user throughput in multipath fading channels and achieves a throughput greater than 100 Mbps using carrier aggregation with 2 CCs and 1-by-2 SIMO. The results also show that when the uplink control information (UCI) corresponding to 5 downlink CCs is multiplexed onto the uplink shared channel (PUSCH), the required block error rate (BLER) of the UCI below 10-2 is almost satisfied by appropriately setting the offset value, , for adjusting the channel coding rate of UCI although AMC with high-order modulation is applied to the UCI as well. Furthermore, we show that when carrier aggregation with 5 CCs and 2-by-2 MIMO multiplexing are applied in the downlink, high throughput greater than 500 Mbps (thus, half of the 1 Gbps that can be achieved using 4-by-4 MIMO multiplexing) is achieved at the average received signal-to-noise power ratio (SNR) of approximately 25 dB when CC-specific AMC considering UCI error is applied

Investigation on Beamforming Control Methods in Base Station Cooperative Multiuser MIMO Using Block-Diagonalized Beamforming Matrix

This paper investigates a beamforming control method in base station (BS) cooperative multiuser multiple-input multiple-output (MIMO) transmission assuming a block-diagonalized unitary beamforming matrix. More specifically, we comprehensively compare open-loop type random (opportunistic) beamforming control to codebook-based closed-loop type beamforming control. The proportional fair (PF)-based scheduling is assumed, and the number of users, codebook size, and delay time of the feedback signal from the user terminals are taken into account in the comparison. Based on numerical results, codebook-based beamforming control with a large codebook size achieves higher system throughput than random beamforming when the number of users is small and the feedback delay time is short. However, we show that when the number of users is large and the feedback delay time is long, random beamforming achieves higher system-level throughput than codebook-based beamforming. This implies that the transmission-rate control with random beamforming is more robust against channel variation than that with codebook-based beamforming. These results suggest that random beamforming, which requires a lower feedback overhead than the codebook-based beamforming, is a promising beamforming strategy in future radio access.

Indoor Experiments on 4-by-2 Multi-User MIMO Employing Various Transmitter Antenna Arrangements in LTE-Advanced Downlink

This paper presents indoor experimental results on the achievable throughput for 4-by-2 multi-user (MU)-MIMO using 2 mobile stations (MSs) and carrier aggregation with 5 component carriers (90-MHz bandwidth) considering various transmitter antenna arrangements in the LTE-Advanced downlink. Under two centralized and two distributed antenna arrangement (CAAs and DAAs) conditions, the throughput performance is evaluated using the implemented LTE-Advanced transceiver, where extended channel state information (CSI) feedback based on eigenvalue decomposition (EVD) is implemented for MU-MIMO operation. The experimental results show that the peak throughput of greater than 1 Gbps is achieved for the CAAs in an indoor environment. The results also showed that although the MS moving speed strongly influences the throughput for Rank-4 MU-MIMO, MU-MIMO is robust against the antenna separation, i.e., fading correlation. Furthermore, we confirm that, in the DAAs, although the peak throughput of 1 Gbps is not observed, the throughput of approximately 700 to 950 Mbps is achieved.

Evaluating Downlink MU-MIMO: Laboratory Experimentation and Results

The Third Generation Partnership Project (3GPP) finalized the radio interface specifications for the next generation mobile communication system, Long Term Evolution (LTE), as Release 8 [1], [2]. LTE provides full IP packet-based radio access with low latency and adopts orthogonal frequency division multiple access (OFDMA) and single-carrier frequency division multiple access (SC-FDMA) as multiple access schemes in the downlink and uplink, respectively. In Japan, the NTT DOCOMO launched a commercial LTE service in December 2010 under the new service brand Xi (crossy) [3]. Meanwhile, in 3GPP standardization, there have been efforts toward establishing an enhanced LTE radio interface, LTEAdvanced (LTE Release 10 and beyond), and specifications for LTE Release 10 were finalized [4], [5]. In LTE-Advanced, it is necessary to support a wider bandwidth than that in LTE Release 8, i.e., 20 MHz, to satisfy the high level requirements corresponding to the target peak data rate of greater than 1 Gb/s. To this end, LTEAdvanced supports carrier aggregation (CA) up to 100 MHz by aggregating multiple component carriers (CCs) with backward compatibility to LTE Release 8. In addition, to satisfy the requirements for further improvement in terms of spectrum efficiency, enhanced multiple-input multiple-output (MIMO) techniques such as higher-order MIMO multiplexing and multiuser (MU)-MIMO are supported.

Investigation of Degradation Factors for Adaptive Modulation and Coding in OFDM-MIMO Multiplexing

This paper investigates the throughput performance using adaptive modulation and coding (AMC) focusing on the causes of impairment to Orthogonal Frequency Division Multiplexing (OFDM) - Multiple-Input Multiple-Output (MIMO) multiplexing. We first investigate the influence of a limited number of modulation and coding schemes (MCSs) and channel estimation error for MCS selection based on mutual information (MI). Second, we clarify the effect of MCS selection error on an increasing maximum Doppler frequency due to the round trip delay time (RTT) in comparison to the throughput upper bound that is computed from the MCS combination providing the maximum throughput considering the block error. Third, we clarify the effect of channel estimation error of maximum likelihood detection (MLD) when using reference signal (RS) based channel estimation in comparison to ideal channel estimation. Through the evaluations, we clarify the impairment factors that degrade the achievable throughput for OFDM-MIMO multiplexing using AMC in an actual multipath fading channel.

TDM based reference signal multiplexing for Faster-than-Nyquist signaling using OFDM/OQAM

This paper proposes time division multiplexing (TDM) based reference signal (RS) multiplexing for non-orthogonal multiplexing employing Faster-than-Nyquist (FTN) signaling for orthogonal frequency division multiplexing (OFDM)/offset quadrature amplitude modulation (OQAM). Accurate channel estimation is essential for FTN signaling when using a turbo soft interference canceller (SIC). We propose dividing resource elements (REs) within a physical resource block (PRB) pair into orthogonal and non-orthogonal RE multiplexing regions based on TDM to decrease inter-symbol interference and inter-subcarrier interference to a substantially low level. The RSs for channel estimation are multiplexed in the REs in the orthogonal RE region. Based on link-level simulations, we show that TDM based RS multiplexing achieves accurate channel estimation such that the loss in the required average received signal-to-noise power ratio for satisfying the average block error rate of 10-2 compared to the case with ideal channel estimation is suppressed to within approximately 2 dB.