Akinori Nakajima

Throughput of turbo coded hybrid ARQ using single-carrier MIMO multiplexing

Broadband wireless packet access will be the core technology of the next generation mobile communication systems. Very high speed and high quality packet transmissions can be achieved by the joint use of multiple-input multiple-output (MIMO) multiplexing and hybrid ARQ (HARQ). However, if single-carrier (SC) transmission is used, the throughput performance significantly degrades due to large intersymbol interference (ISI) resulting from severe frequency-selective channels. Recently, we proposed an iterative parallel interference cancellation (PIC) for MIMO multiplexing in a frequency nonselective fading channel. We now propose a frequency-domain iterative PIC for SC-MIMO multiplexing to separate signals transmitted from different antennas while achieving frequency and antenna diversity gain. We evaluate, by computer simulation, the throughput performance of turbo coded HARQ using SC-MIMO multiplexing in a frequency-selective Rayleigh fading channel.

Iterative Joint PIC and 2D MMSE-FDE for Turbo-coded HARQ with SC-MIMO Multiplexing

Broadband wireless packet access will be the core technology of the next generation mobile communication systems. For very high-speed and high-quality packet transmissions, the joint use of multiple-input multiple-output (MIMO) multiplexing and hybrid ARQ (HARQ) is very effective. However, if single-carrier (SC) transmission is used, the transmission performance significantly degrades due to a large inter-symbol interference (ISI) resulting from a severe frequency-selective fading. Recently, we proposed a frequency-domain iterative parallel interference cancellation (PIC) for SC-MIMO multiplexing. For signal separation, 2 dimensional minimum mean square error (2D MMSE)-FDE is performed at first. Then, the joint PIC and ID MMSE-FDE is repeated a sufficient number of times. However, the interference from other transmit antennas still remains at the outputs of PIC. Therefore, in this paper, we propose to use 2D MMSE-FDE instead of ID MMSE-FDE in each iteration and investigate, by computer simulation, the achievable bit error rate (BER) and throughput performance of HARQ in a frequency-selective Rayleigh fading channel

Cyclic shear force–slip behavior of studs under alternating and pulsating load condition

Abstract The objective of this study is to investigate the maximum strength and the fatigue strength of studs subjected to the alternating load as well as the pulsating load. First, in order to conduct a series of static and fatigue test of studs under both the load conditions, we devise a new specimen to which the alternating shear force can be applied easily by general fatigue testing machines. Employing the devised specimens, the shear force–slip behavior, the maximum strength and the fatigue strength of studs under the alternating load condition are investigated and are compared with those under the pulsating load condition.

Iterative FDIC Using 2D-MMSE FDE for Turbo-Coded HARQ in SC-MIMO Multiplexing

SUMMARY Multiple-input multiple-output (MIMO) multiplexing is an attractive technique to achieve very high-speed transmission with a limited bandwidth. Recently, we proposed an iterative frequency-domain interference cancellation (FDIC) for single-carrier MIMO (SC-MIMO) multiplexing. In our previous work, assuming that the interference from the other antennas can be perfectly cancelled in FDIC, one-dimensional minimum mean square error (1D-MMSE) frequency-domain equalization (FDE) was used. However, the residual interference remains after performing FDIC. In this paper, to improve the transmission performance with iterative FDIC, we replace 1D-MMSE FDE by 2D-MMSE FDE, which takes the residual interference from the other antennas after FDIC into account. We investigate, by computer simulation, the throughput performance of rate compatible punctured turbo coded hybrid ARQ (RCPT-HARQ) with MIMO multiplexing in a frequency-selective Rayleigh fading channel.

LDPC-Coded HARQ Throughput Performance of MC-CDMA Using ICI Cancellation

Broadband packet data services are demanded in the next generation mobile communications systems. Multi-carrier CDMA (MC-CDMA) is considered to be a promising wireless technique. Hybrid ARQ (HARQ) is a powerful error control technique. It is known that the HARQ throughput performance of MC-CDMA degrades due to the residual inter-code interference (ICI) after frequency-domain equalization (FDE). The use of frequency-domain soft interference cancellation FDSIQ technique can reduce the residual ICI and improve the throughput performance. An important technical problem is the generation of accurate residual ICI replica for FDSIC. In this paper, we consider low-density parity-check coded (LDPC- coded) MC-CDMA HARQ and generate the residual ICI replica from a-posteriori log-likelihood ratio (LLR) obtained by the LDPC decoder. We evaluate, by computer simulation, the throughput performance in a frequency-selective Rayleigh fading channel. We show that if the residual ICI is removed MC- CDMA can provide better throughput performance than orthogonal frequency division multiplexing (OFDM).

Throughput Performance of Iterative Frequency-Domain SIC with 2D MMSE-FDE for SC-MIMO Multiplexing

Broadband wireless packet access will be the core technology of the next generation mobile communication systems. For very high-speed and high-quality packet transmissions in a limited bandwidth, the joint use of multiple-input multiple-output (MIMO) multiplexing and hybrid ARQ (HARQ) is an effective method. However, if single-carrier (SC) transmission is used, the transmission performance significantly degrades due to a large inter-symbol interference (ISI) resulting from a severe frequency-selective fading. In this paper, we propose an iterative frequency-domain successive interference cancellation (SIC) with two dimensional (2D) MMSE-FDE. At each iteration stage, the successive signal detection/cancellation is performed according to the descending order of the signal reliability. However, since the interference from the other transmit antennas can be only partially cancelled by performing SIC, the residual interference is present at the output of SIC. In this paper, we propose to update the 2D MMSE-FDE weights at each signal detection in order to suppress simultaneously the ISI and the interference from other antennas while obtaining antenna and frequency diversity gain. However, since a single use of SIC with 2D MMSE-FDE is insufficient, it is repeated a sufficient number of times. The bit error rate (BER) and HARQ throughput performance in a frequency-selective Rayleigh fading channel are evaluated by computer simulation.

Channel Estimation Using Cyclic Delay Pilot for SC-MIMO Multiplexing

In the next generation mobile communication systems, multiple-input multiple-output (MIMO) multiplexing is an indispensable technique to achieve very high-speed data transmission with a limited bandwidth. In MIMO multiplexing, it is necessary to estimate the channels between transmit and receive antennas for signal detection. In this paper, we propose a minimum mean square error (MMSE) channel estimation using cyclic delay pilot for single-carrier (SC)-MIMO multiplexing. In the proposed channel estimation, the same pilot block is altered through the addition of different cyclic delays and transmitted from different antennas at the same time for simultaneous estimation of all channels between transmit and receive antennas. We evaluate by computer simulation the bit error rate (BER) performance of MIMO multiplexing using the proposed channel estimation and compare it to those using time-multiplexed pilot based channel estimation (TMP-CE) and code-multiplexed pilot based channel estimation (CMP-CE).

Frequency-Domain Eigenbeam-SDM and Equalization for Single-Carrier Transmissions

In mobile communications, the channel consists of many resolvable paths with different time delays, resulting in a severely frequency-selective fading channel. The frequency-domain equalization (FDE) can take advantage of the channel selectivity and improve the bit error rate (BER) performance of the single-carrier (SC) transmission. Recently, multi-input multi-output (MIMO) multiplexing is gaining much attention for achieving very high speed data transmissions with the limited bandwidth. Eigenbeam space division multiplexing (E-SDM) is known as one of MIMO multiplexing techniques. In this paper, we propose frequency-domain SC E-SDM for SC transmission. In frequency-domain SC E-SDM, the orthogonal transmission channels to transmit different data in parallel are constructed at each orthogonal frequency. At a receiver, FDE is used to suppress the inter-symbol interference (ISI). In this paper, the transmit power allocation and adaptive modulation based on the equivalent channel gains after performing FDE are applied. The BER performance of the frequency-domain SC E-SDM in a severe frequency-selective Rayleigh fading channel is evaluated by computer simulation.

Turbo coded MIMO multiplexing with iterative adaptive soft parallel interference cancellation

An iterative adaptive soft parallel interference canceller (ASPIC) is proposed for turbo coded multiple-input multiple-output (MIMO) multiplexing. ASPIC is applied to transform a MIMO channel into single-input multiple-output (SIMO) channels for maximum ratio diversity combining (MRC). In the iterative ASPIC, replicas of the interference from different transmit antennas are generated and subtracted from the received signals. The log-likelihood ratio (LLR) sequence, obtained as the turbo decoder output, is fed back for iterative interference cancellation. At the transmitter, the information bit sequences and parity bit sequences are transmitted from different antennas. The achievable bit error rate (BER) performance of turbo coded MIMO multiplexing with the proposed iterative ASPIC in a Rayleigh fading channel is evaluated by computer simulation.

Frequency-domain equalisation for block CDMA transmission†

Frequency-domain equalization (FDE) technique may play an important role for broadband packet transmission using MC- and DS-CDMA. The downlink performance is significantly improved with FDE; however, the uplink performance is limited by the multi-access interference (MAI). To remove the MAI while gaining the frequency diversity effect through the use of FDE, frequency-domain block spread CDMA can be used. The performance can be further improved by the use of multi-input/multi-output (MIMO) antenna technique. Recently, particular attention has been paid to MIMO space division multiplexing (SDM) to significantly increase the throughput without expanding the signal bandwidth. In this paper, we present a comprehensive performance comparison of MC- and DS-CDMA using FDE.