Tadashi Fujino

• Doctor of Engineering. Professor Emeritus
• Professor Emeritus at University of Electro-Communications

In this paper, the exact general expression of bit error rates (BERs) for M-QAM modulation is derived for Gray mapped square M-QAM signals in the AWGN channel. The numerical calculations of not only the average BERs but also the BERs for each bit are done. And we found that the first bit for symbol of the M-QAM achieves better BER than the last bit...

This paper proposes an improved lattice-reduction aided (LRA) MMSE detection scheme, based on the Gram-Schmidt (GS) procedure. The proposed scheme reduces the column vectors of the MIMO channel matrix, by using the LLL algorithm followed by the GS procedure in order to transform the channel matrix into a new one which has mutually purely orthogonal...

The problem addressed here is how it is possible to design a coded 8PSK modem with a simple Viterbi decoder for 120 Mbit/s operation. A coded 8PSK modem with Ungerboeck codes of rate 2/3 to assess the feasibility of its application to the Intelsat TDMA system. The development effort has been concentrated mainly on the design of the Viterbi decoder...

The effects of phase jitter and cycle slipping of the recovered carrier upon unique word (UW) missed detection in QPSK systems are investigated. Schrempp et al. have already presented the relationship between the UW missed detection probability (UWMP) and the bit error probability, which is simple and useful as long as the phase reference is noisel...

This document is the revised version of the first version uploaded on Oct. 16, 2020. Sections 5 and 6 are revised. Sections 9 and 10 are added to the first version. Section 10 compares the Eb/N0 vs. BER performances in MIMO systems for the typical LR-ZF and the typical LR-MMSE detections, the LR-SIC-MMSE detection and the reciprocal LR-MMSE detecti...

SUMMARY_ Multiple-input multiple-output (MIMO) technique has been attracting attention in wireless communications, since it provides significant increases of data throughput and the high spectral efficiency. Lattice-reduction (LR) aided (LRA) detection has been adopted to improve the performance and to reduce the complexity in MIMO data detection....

This document explains the decision feedback signal sequence estimator (DFSE) in detail. The DFSE is a receiver having the function of the channel equalization and the estimation of the transmitted signal. It estimates the transmitted signal at the receiver in the fast time-varying intersymbol interference channels. The DFSE first creates the repli...

This document explains the decision feedback signal sequence estimator (DFSE) in detail. The DFSE is a receiver having the function of the channel equalization and the estimation of the transmitted signal. It estimates the transmitted signal at the receiver in the fast time-varying intersymbol interference channels. The DFSE first creates the repli...

This document explains the decision feedback sequence estimation (DFSE) technique in the fast time-varying multipath fading channels. 本稿では,高速のマルチパスフェージング環境において, 送信器から送信された信号を受信機で推定する方式について述べる．ここでは，適応等化と復調を一体化した判定帰還型信号系列推定方式（Decision Feedback Signal Sequence Estimation：DFSE）について解説する．DFSE方式は，まず，受信信号のレプリカを構成し，このレプリカを，信号がレプリカのトランスバーサルフィルタに入力するたびに，ビタビアル...

This paper presents the explanation of the adaptive equalization and signal estimation in the fast time-varying channels.

This paper presents the clock-aided multiplification of the received signals for PSK modems. This method reduces the pattern noise produced by the multiplufication of the received signals. The paper verifies the reduction of the pattern noise by the hardware experimentation.

This paper presents the OFDM transmission technology, in which the key theory and the practical design are included.

This patent is the invention of the "clock-aided frequency multiplier" for M-PSK modulated signals. This invention made by Tadashi Fujino is the basis of Tadashi Fujino et al's papers "A 120Mbit/s coded modem with soft-decision Viterbi decoder" published in ICC'86, and "A 120Mbit/s modem with soft-decision Viterbi decoder" published in Int. Conf. o...

This patent is the invention of the "pipelined convolutional code/Viterbi decoder". This invention made by Tadashi Fujino is the basis of Tadashi Fujino et al's papers "A 120Mbit/s coded modem with soft-decision Viterbi decoder" published in ICC'86, and "A 120Mbit/s modem with soft-decision Viterbi decoder" published in Int. Conf. on Digital Satell...

Lattice-reduction (LR) technique has been adopted to improve the performance and reduce the complexity in MIMO data detection. This paper presents an improved quantization scheme for LR aided MIMO detection based on Gram-Schmidt orthogonalization. For the LR aided detection, the quantization step applies the simple rounding operation, which often l...

This paper proposes a low complexity MIMO detection using ordering SIC (OSIC) with conditional list generation. Combined with lattice-reduction (LR) technique, OSIC further gains the BER performance compared to SIC, since the more reliable signal is prior to being detected. However OSIC based on LR (LR-OSIC) has inferior performance to the maximum...

In this paper, we present an efficient quantization scheme for lattice-reduction (LR) aided (LRA) MIMO detection using Gram-Schmidt orthogonalization. For the LRA detection, the quantization step applies the simple rounding operation, which often leads to the quantization errors. Meanwhile, these errors may result in the detection errors. Hence, th...

Lattice-reduction (LR) is a promising technique to improve the performance of MIMO data detection. This paper presents an improved quantization scheme for LR aided MIMO detection based on Gram-Schmidt (GS) orthogonalization. For the LR aided detection, the quantization errors occur due to the rounding operations. These errors may result in the dete...

Lattice-reduction is an effective technique to improve the performance of MIMO data detection. This paper presents a quantiza-tion error reduction scheme for MIMO detection based on orthogonal lattices. The motivation of the proposed detection is to solve the problem of degrading the performance due to the rounding quantization error in the signal...

This paper proposes an adaptive candidate selection scheme in the QRM-MLD algorithm for MIMO detection. The QRM-MLD is a near-ML detection algorithm which can achieve a tradeoff between the BER performance and the computational complexity in the MIMO systems. In this paper, we adopt an adaptive candidate selection scheme into the QRM-MLD. First, si...

This paper proposes new adaptive tree search detection with variable path expansion based on Gram-Schmidt (GS) orthogonalization (GSO) in MIMO systems. We adopt the GSO procedure to reduce the channel matrix instead of the QR-decomposition in the conventional QRM-MLD. This detection scheme combined the GSO reduction with the M-algorithm, what we ca...

Effective detectors with low-complexity are considered for the Alamouti’s multiuser space-time block coded (STBC) systems. Viewing the noiseless received signals from Q users as a lattice with basis vectors being the columns of the total channel matrix H, we apply lattice reduction to transform the original basis into a nearly orthogonal one which...

This paper presents an effective antenna selection scheme for multiple input multiple output spatial division multiplexing (MIMO-SDM) systems. The scheme uses the mean square error (MSE) as the criterion for selecting the best subset of transmit/receive antennas to improve the system error performance. Compared with the previous channel matrix norm...

Lattice reduction aided (LRA) linear detectors have been known to achieve near optimal performance at low complexity. However, one weakness of LRA detector is that the quantization step in LRA detector is not optimal. Based on simulation results, we show that most of detection errors in LRA linear detectors are due to quantization errors. We then p...

In this paper, we proposes a low-complexity lattice-reduction aided detection (LRAD) based on the Gram-Schmidt (GS) procedure in multi-input multi-output (MIMO) communications. The conventional LRAD achieves good bit error ratios (BERs) because it reduces the column vectors of the channel matrix close to orthogonal using LLL Algorithm. The proposed...

This paper proposes an MMSE detector using forward and backward reciprocal lattice reduction (LR) in MIMO systems. In the 8×8 MIMO systems, the reciprocal LR aided detection (LRAD) achieves better BER performances about 3dB than the LRAD using the conventional LLL algorithm over BER=10-5. The proposed method furthermore achieves better BER performa...

This paper proposes a lattice-reduction aided detection (LRAD) based successive interference cancellation (SIC). The proposed detector achieves as good as or better BER performances than the conventional LR aided MMSE detector and using the SIC for QPSK, 16QAM and 64QAM in the 8×8 MIMO systems. It also achieves BER curves to be as steep as or steep...

Selected mapping (SLM) is a well-known technique to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). SLM generally requires the side information for each OFDM symbol, which leads to decrease the transmitting efficiency. In addition, false side information detection degrades the bit error rate (BER)...

This paper proposed a detection method combined the list detection with partial successive interference cancellation (SIC) based on the reciprocal lattice-reduction in MIMO system. List detection is an effective detection method for improving the performance of MIMO signal detection, but the computational expense depending on the list length is the...

This paper proposes a lattice-reduction aided detection (LRAD) based on the Gram-Schmidt (GS) procedure. In MIMO systems, LRAD achieves good bit error ratios (BERs). The proposed detection method reduces the column vectors of the channel matrix using the LLL algorithm and then the GS procedure to create mutually purely orthogonal column vectors in...

Selected mapping (SLM) is a well-known technique to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). SLM generally requires the side information for each OFDM symbol, which leads to decrease the transmitting efficiency. In addition, false side information detection degrades the bit error rate perfo...

Lattice reduction is an effective technique for improving the performance of MIMO data detection. In this paper, we analyze lattice reduction processing on the basis lattice and the dual lattice for MIMO detection and investigate the parameters which affect the complexity of the LLL algorithm. Through use of the dual lattice in the LLL algorithm, t...

This paper proposes an MMSE detector applying the reciprocal lattice reduction (LR) in MIMO systems. The proposed detector achieves as good as or better BER performances than the LR aided detector using the conventional LLL algorithm and using the Seysen's algorithm in the 4×4 and the 8×8 MIMO systems. It also achieves BER curves to be as steep as...

This paper proposes an improved lattice-reduction aided (LRA) MMSE detection based on the Gram-Schmidt (GS) procedure. The proposed detection reduces the column vectors of the MIMO channel matrix using the LLL algorithm and the GS procedure to create mutually purely orthogonal column vectors of the reduced channel matrix. Then the decision boundary...

Antenna selection is a promising technique which provides performance improvement for multiple input multiple output (MIMO) systems at low cost of additionally employed antennas and signal processing. Various antenna selection algorithms based on different criteria have been proposed in the literature. This paper presents a new antenna selection al...

This paper proposes an improved lattice-reduction aided (LRA) MMSE detection by combining the LLL algorithm and the Gram-Schmidt (GS) procedure. The proposed detection reduces the column vectors of the MIMO channel matrix using the LLL algorithm and the GS procedure to create mutually purely orthogonal column vectors of the reduced channel matrix....

In helicopter satellite communications, the periodic blockage of received signal and the carrier frequency fluctuation are the most important problems. In this paper, we propose a novel automatic frequency controller (AFC) scheme with time diversity combining. The proposed AFC generates the frequency error signal based on the time diversity combine...

This paper proposes a combined forward and backward lattice-reduction aided detection scheme to improve estimation of transmitted signals in lattice-reduction aided (LRA) MMSE MIMO systems. The cross-correlation between the forward and the backward reduced channel matrices is also analyzed to make sure that the proposed detector achieves more relia...

This paper proposes an improved lattice-reduction aided (LRA) MMSE detection with successive interference cancellation (SIC) using both the forward and the backward (F&B) reduction LLL algorithms. We also apply a simple list detection to the F&B-LRA MMSE with SIC. The proposed detector provides good BER performance relatively close to that with the...

This paper proposes a novel lattice-reduction aided (LRA) detection in MIMO systems by improving the LRA-MMSE detection. The proposed detection scheme makes five transform matrices by iteratively reducing the columns of the channel matrix. Using the five transform matrices, five estimates of the transmitted signal are created, among which the most...

In helicopter satellite communications, the periodic blockage of the received signal and the carrier frequency fluctuation are the most important problems. In this paper, we propose a novel pre-detection time diversity combining scheme with accurate automatic frequency controller (AFC) for helicopter satellite communications. In the proposed scheme...

This paper proposes a combined forward and backward lattice reduction scheme to improve estimation of transmitted signals in lattice-reduction aided (LRA) MMSE MIMO systems. The cross-correlation between the forward and the backward transform matrices is also analyzed to make sure that the proposed detector achieves more reliable estimates. The pro...

Lattice reduction aided (LRA) detection with the LLL algorithm has been investigated to achieve the MIMO channel capacity with low computational complexity. This paper proposes an improved LRA-MMSE detection using the forward and the backward reduction LLL algorithms for the 8times8 MIMO to obtain more reliable estimates of the transmitted signals....

This paper proposes an improved lattice-reduction aided (LRA) MMSE detection based on the Gram-Schmidt orthogonalization. With the proposed detection, much reliable estimate can be achieved, compared to the conventional LRA detection. The BERs are much closer to those with the ML detection in the 4 times 4 MIMO and the 8 times 8 MIMO systems.

This paper considers detection schemes for the combined space-time block coding and spatial multiplexing (STBC-SM) transmission systems. We propose a symbol detection scheme which allows to extend the limit on the number of transmit antennas imposed by the previous group detection scheme. The proposed scheme allows to double multiplexing gain as we...

This paper aims at improving bit error rate (BER) performance of lattice reduction aided (LRA) linear detectors for multiple input multiple output (MIMO) wireless systems. Specifically, we present an improved quantization scheme for LRA detectors which can generate a set of candidate symbols from the original LRA estimated symbol. From these symbol...

This paper aims at improving bit error rate (BER) performance of lattice reduction aided (LRA) linear detectors for multiple input multiple output (MIMO) wireless systems. Specifically, we present an improved quantization scheme for LRA detectors which ran generate a set of candidate symbols from the original LRA estimated symbol. From these symbol...

Lattice reduction aided (LRA) has been introduced recently by Yao and Wornell as a new type of MIMO detector. However, the quantization step of LRA detector is only suboptimal. In this paper, we propose a list quantization scheme to reduce the effect of quantization error. The method is to generate a list of candidate symbols from the original LRA...

Recently, lattice reduction aided (LRA) detector has been introduced into conventional detectors for MIMO systems, to improve the performance. In LRA detectors, the first quantization step is simply a rounding operation, regardless to the original constellation. Sometimes, it causes quantization error that makes the obtained point to lie outside of...

Recently, lattice reduction aided (ERA) detectors have been introduced into Vertical Bell-Labs Layered Space-Time (V-BEAST) systems to obtain nearly optimal bit error rate (BER) performance for only small additional complexity. In this paper, the layer error characteristics of LRA-V-BLAST detectors are analyzed and compared with those of convention...

Recently, lattice reduction aided (LRA) detectors have been introduced into Vertical Bell-Labs Layered Space-Time (V-BLAST) systems to obtain nearly optimal bit error rate (BER) performance for only small additional complexity. In this paper, the layer error characteristics of LRA-V-BLAST detectors are investigated and compared with those of conven...

In this letter, we propose a combined scheme of minimum mean square error (MMSE) detection and successive interference cancellation (SIC) for multiuser space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems. With the same complexity order, the proposed scheme provides significant bit error rate (BER) performance impro...

Orthogonal frequency division multiplexing (OFDM) is known as a promising technique for data transmission over broadband wireless communication channels. However, bit error rate (BER) performance of OFDM deteriorates significantly in time-varying channels due to presence of inter-channel interference (ICI). Previous works proposed time or frequency...

In this letter, we propose a combined scheme of minimum mean square error (MMSE) detection and successive interference cancellation (SIC) for multiuser space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems. With the same complexity order, the proposed scheme provides significant bit error rate (BER) performance impro...

A combined minimum mean square error (MMSE) and maximum likelihood (ML) multiuser detector with reduced-complexity is proposed for uplink space-time block coded (STBC) orthogonal frequency division multiplexing (OFDM) systems. In this combined detector, received signals from cochannels are first detected by an MMSE multiuser detector. Then an ML-ba...

We propose a scheme for mobile communications to combat the channel blocking. The scheme is of the MIMO-STBC for the downlink MC-CDMA, which enables receivers to extract all the signals even when they encounter the blocking.

In this paper, we propose two minimum mean square error (MMSE)-based multiuser detectors, called the combined MMSE and maximum likelihood (MMSE-ML) multiuser detector and the combined MMSE and successive interference cancellation (MMSE-SIC) multiuser detector, for an uplink space-time block coded orthogonal frequency division multiplexing (STBC-OFD...

Performance of the minimum mean square error (MMSE) detection is far below that of the maximum likelihood (ML) detection in a multiuser environment and decreases significantly as the number of co-channel users increases. In this paper, we propose a combined MMSE and ML multiuser detection scheme for space-time block coded (STBC) orthogonal frequenc...

Performance of the minimum mean square error (MMSE) detection is far below that of the maximum likelihood (ML) detection in a multiuser environment and decreases significantly as the number of co-channel users increases. In this paper, we propose a combined MMSE and ML multiuser detection scheme for space-time block coded (STBC) orthogonal frequenc...

This paper considers the downlink of the multicarrier (MC)-CDMA for mobile communications, in which mobile equipments like portable phone handsets usually have two antennas equipped closely. If moving through places having weak RF power from the transmitter, the handsets sometimes experience the situation that all the channels are blocked. In such...

In this paper, we propose a multiuser detection (MUD) scheme for space-time block coded orthogonal frequency division mul-tiplexing (STBC-OFDM) systems. We derive the optimum weight matrix used to decouple simultaneously signals from active multiple access users using the minimum mean square error (MMSE) multiuser detection method. The proposed sch...

Performance of multiuser orthogonal frequency division multiplexing (OFDM) systems with transmit diversity over the frequency selective fading channel is explored. We develop a signal model for the multiuser OFDM system using Alamouti's transmit diversity scheme and apply the minimum mean square error (MMSE) method to detect the transmitted symbols...