Minoru Okada

2 by 2 MIMO system using single leaky coaxial cable for linear-cells

Leaky coaxial cables (LCX) have been widely used as antennas to form linear service areas for radio communication systems. Such services of linear cells have been deployed inside tunnels, along railways, and so on. Usually, one LCX is utilized as one antenna. Therefore it requires more than one LCX to configure an multi-input multi-output (MIMO) system. In this paper, we propose a MIMO system using single LCX, which can be utilized as two antennas. When different RF transmit signals are fed to each end of the proposed cable, single LCX can work as two antennas. To confirm the feasibility of the proposed MIMO system, we conduct experiments to measure the characteristics of 2 × 2 MIMO channel using single LCX. The results confirm that our proposed 2×2 MIMO channel using single LCX can realize a good channel condition for MIMO transmission even within a highly correlated propagation condition. The proposed MIMO system using LCX will release the space requirement and reduce the cost of system for configuration of LCX MIMO system especially with large number of LCXs. It benefits the design and configuration of LCX-MIMO system for many scenarios of linear-cell.

Performance comparison for 2 by 2 MIMO system using single leaky coaxial cable over WLAN frequency band

In linear service areas such as a tunnel and along railways, leaky coaxial cable (LCX) is widely used as antenna for radio communication. Usually, one LCX is utilized as one antenna. Therefore it requires more than one LCX to configure an multi-input multi-output (MIMO) system. We have recently proposed a method that one single LCX can be utilized as two antennas by feeding different RF transmit signals to each end of the proposed cable. In this paper, we compare 2×2 MIMO system performance using the proposed LCX and using conventional monopole antennas over 2.4GHz band for WLAN appliances. The results confirm that our proposed 2×2 MIMO channel using a single LCX can realize a good channel condition and bit error ratio (BER) performance for MIMO transmission even within a highly correlated propagation condition. On the other hand, it also shows that the proposed LCX MIMO is promising technique for communications over linear-cell environments from the simulated results which considering the path loss and radiation pattern of LCX characteristics.

Realization of 4-by-4 MIMO channel using one composite leaky coaxial cable

Leaky coaxial cable (LCX) is widely used for wireless communication systems as an antenna for a linear-cell, which covers long and shallow areas. Since one LCX is usually utilized as one antenna, more than one LCX is required to configure a multi-input multi-output (MIMO) system. It means it is costly and space-consuming. To resolve these problems, we proposed a novel MIMO method for LCX. In this paper, we propose the method to utilize one composite cable, which consists of a pair of LCXs with different radiation characteristics, to configure a 4 × 4 MIMO channel. The measurement results confirmed that the proposed composite cable can realize a good channel condition for 4 × 4 MIMO transmission even if it is put in an anechoic chamber where no reflection path exists. On the other hand, the results also confirmed that it has good channel condition even if the spacing between a pair of LCX is as small as 2cm for the 5GHz band. Therefore the proposed system can reduce the space requirement for MIMO deployment for wireless application over linear-cell environments to cope with the high rapid increase of consumer electronics devices.

A proposal of data transmission in parallel line fed wireless power transfer

This paper proposes a data transmission for parallel line fed wireless power transfer system. We focus on power receiver-to-source transmission link and employ the load modulation as a modulation scheme. To transmit data back to the power source from receiver, the power receiver periodically switches its load impedance to modulate the electric current, which can be observed at the source using envelope detection. The load modulation generally has a trade-off between modulation index and power transfer efficiency. Numerical analysis showed that, the system is able to achieve sufficiently a high modulation index while maintaining a high power transfer efficiency, if appropriate switching values for load impedance are employed. This result clarifies feasibility of the proposed load modulation.

4-by-4 MIMO channel using two leaky coaxial cables (LCXs) for wireless applications over linear-cell

We have recently proposed a novel 2 × 2 multiple-input multiple-output (MIMO) system that utilizes a single leaky coaxial cable (LCX) as two antennas. In this paper, we further propose a 4 × 4 MIMO system by combining two LCXs that have different radiation characteristics into one composite cable and evaluate characteristics of the channel with different spacing between the LCXs. Since the different radiation characteristics create different propagation paths, the proposed system with small spacing between LCXs can realize an efficient channel condition for 4 × 4 MIMO transmission. As a result of measurement at 2.4 GHz band, the smaller spacing as to 1 cm between LCXs makes better 4 × 4 MIMO channel condition for transmission. This result indicates that the proposed system can reduce the space requirement for system deployment.

Development of a novel marking system for laparoscopic gastrectomy using endoclips with radio frequency identification tags: feasibility study in a canine model

BackgroundIntraoperative identification of early gastric cancer is difficult to conduct during laparoscopic procedures. In this study, we investigated the feasibility and accuracy of a newly developed marking system using endoclips with radio frequency identification (RFID) tags in a canine model.MethodsRFID is a wireless near field communication technology. Among the open frequency bands available for medical use, 13.56xa0MHz is suitable for a surgical marking system because of the similar and linear signal decay both in air and in biological tissues. The proposed system consists of four parts: (a) endoclips with RFID tags, (b) endoclip applier equipment, (c) laparoscopic locating probe, and (d) signal processing units with audio interface. In the experimental setting using canine models, RFID-tagged endoclips were applied to the mucosa of each dog’s stomach. During the subsequent operation, the clips with RFID tags placed in five dogs were located by the detection of the RFID signal from the tag (RFID group), and the conventional clips in the other six dogs were located by finger palpation (FP group). The detected sites were marked by ablation on the serosal surface. Distance between the clips and the metal pin needles indicating ablated sites were measured with X-ray radiographs of the resected specimen.ResultsAll clips were successfully detected by the marking system in the RFID group (10/10) and by finger palpation in the FP group (17/17). The medians of detection times were 31.5 and 25.0xa0s, respectively; the distances were 5.63 and 7.62xa0mm, respectively. The differences were not statistically significant. No adverse event related to the procedures was observed.ConclusionsEndoclips with RFID tags were located by our novel marking system in an experimental laparoscopic setting using canine stomachs with substantial accuracy comparable to conventional endoclips located by finger palpation through an open approach.

Modified orthogonal matching pursuit based ISDB-T channel estimation over fractional delay channel

Integrated Service Digital Broadcasting for Terrestrial (ISDB-T) is a Japanese standard for digital television that uses a multi-subcarrier systems called Orthogonal Frequency Division Multiplexing (OFDM). A solution for compressed sensing called Modified Orthogonal Matching Pursuit (MOMP) is capable of reducing the computational cost for channel estimation. This paper extends the capability of MOMP in fractional multipath delay channel. The simulation results shows that the proposed method is robust against fractional delay by obtaining a good Bit-Error-Rate Performance in rayleigh fading channel.

Interference suppression schemes for Radio over Fiber simultaneously transmitted with 10 Gbps On-Off Keying

Radio over Fiber (RoF) and 10 Gbps optical On-Off Keying (OOK) signal can be simultaneously transmitted by using the stochastic process of optical OOK as a carrier for the radio frequency (RF) signal. The theoretical analysis of the power spectrum and error vector magnitude (EVM) agree with experimental results. The experimental and theoretical results show that the OOK modulation interferes with the RF signal. In this paper, interference suppression schemes are proposed. The improvement in terms of EVM and dynamic range is discussed from theoretical analysis and computer simulation.

A proposal of electromagnetic coupling for parallel line fed wireless power transfer

This paper proposes electromagnetic coupling for stabilizing the power transfer efficiency (PTE) of parallel line fed wireless power transfer (WPT). The conventional WPT system using magnetic coupled parallel line feeder suffers from PTE fluctuation due to magnetic field standing wave along the feeder line. Focusing on the fact that electric and magnetic fields are out of phase by 90 degrees, we propose a combination of electric and magnetic coupling to stabilize the PTE. In addition, load impedance is also optimized to Z-parameters of the system for further PTE enhancement. Numerical analysis confirmed effectiveness of the proposed electromagnetic coupling in stabilizing PTE for the WPT system.

Effective VLSI architecture for Compressed Sensing based channel estimation in ISDB-T system

Compressed Sensing (CS) based channel estimation has been proven to give a better reconstruction results compared to conventional method. Despite promising a better result, CS based channel estimation still suffers from high complexity computations due to huge matrix multiplication and matrix inversion operations. This paper will propose an effective CS based channel estimation VLSI architecture for ISDB-T system. Since ISDB-T system is using orthogonal frequency division multiplexing (OFDM) technique for its transmission, its CS channel estimation will utilize a measurement matrix which is formed by parts of Discrete Fourier Transform (DFT) matrix. By exploiting the fact that the measurement matrix will inherit some symmetrical properties from DFT matrix, we can achieve a low complexity CS based channel estimation for practical implementation.