Hideki Toshinaga

A broadband low-noise wide dynamic range SiGe front-end receiver IC for multi-band access points

A broadband, low-noise, wide dynamic range front-end receiver IC is reported. It uses 0.25 μm SiGe BiCMOS process technology and consists of broadband variable gain low noise amplifiers (VGLNAs), down-conversion mixers, step attenuators, and buffer amplifiers. It can receive triple-band signals concurrently, and the chip size is only 3mm × 3mm. Its measured noise figure was under 3.2 dB and the measured conversion gain was around 30 dB in the broad frequency range from 300 MHz to 3 GHz. It has a wide gain control range of around 100 dB; 50 dB is controlled by the VGLNA and the step attenuator, and 50 dB by the mixer with novel relative power control method using dual LO signal. The gain control enhances the input 1dB compression point from -40 dBm to -21 dBm.

Performance measurement of broadband simple decoding in short-range MIMO

In a short-range multiple-input and multiple-output (SR-MIMO) transmission system that relies on line-of-sight (LOS) propagation, the channel matrix is determined by the antenna geometry, hence radio frequency (RF) signal processing by using an analog matrix circuit is a valid means of separating spatially-multiplexed multiple signal streams. To date several simple decoding methods utilizing this feature for SR-MIMO transmission have been proposed and demonstrated at one frequency point. This paper presents a demonstration of a simple decoding method for two-branch SR-MIMO transmission in a broadband with eight percent relative bandwidth, which corresponds to two-channel usage in the 60-GHz band. An experimental evaluation of the method was performed after prototyping the array antenna and weight matrix circuit. The evaluation results showed signal separation performance of 15 dB was obtained through the frequency range of 24.0-26.0 GHz. Bit error rate (BER) was simulated using measured transmission characteristics and we determined that 16 QAM signals at this band can be transmitted in the prototype system.

A Novel ZF-Based Fast Beamforming Method for Short-Range MIMO Transmission

Millimeter-wave short-range multiple-input multiple-output (SR-MIMO) transmission employing zero-forcing beamforming (ZF-BF) at the information kiosk side can improve transmission rate without increasing mobile terminal power consumption for MIMO signal processing. However, processing delay for ZF weight generation is large, so the effects of time-varying channels due to the users hand jiggling, which cause performance degradation, cannot be ignored. In this letter, a novel fast beamforming method is described with which ZF-based weight can be generated with low delay by utilizing the relationship of channel variation and ZF weight variation. Simulation results show that the method can achieve better performance than ZF-BF.

1-bit compressed sensing with edge detection for compressed radio wave data transfer

The “Flexible Wireless System (FWS)” has been proposed as a networked system for the “User-Centric Wireless Network (UCWN)”. The UCWN will allow users to make network connections easily at all times without being conscious of any upgrades or differences in wireless systems. The FWS is a unified wireless platform that simultaneously deals with various types of wireless signals. It consists of flexible access points and a wireless signal processing platform. Various types of wireless signals are received at a distributed flexible access point and transferred to a server in the wireless signal processing platform through the wired access line. Transferred signals are separated and demodulated at the server. To achieve highly flexible and efficient radio wave data transfer between the access point and the FWS server, we consider compression of transfer data. In this paper, we propose 1-bit compressed sensing with smoothed edge detection, which enhances compression and reconstruction performance. This paper shows the performance of the proposed method by using computer simulations to explore the methods validity for transferring compressed radio wave data.

Dependency on Beamwidth in an SD Method Utilizing Two-Ray Fading Characteristics

Using ray-tracing propagation calculation, we clarify the dependency on antenna element beamwidth of the channel capacity of a spatial division (SD) transmission method utilizing the characteristics of two-ray fading. It was clarified that the SD transmission method can be effectively applied to microstrip antennas or horn antennas with beamwidth of more than 10 °, but that it is not effective when applied to narrow-beam antennas with less than 10 ° beamwidth. In such cases, simple parallel transmission is a better way to utilize the narrow beam to increase channel capacity .

Bi-directional multimedia satellite communication system employing superposed transmission

A bi-directional multimedia satellite communication system has been proposed to support high-speed Internet access. This system utilizes a low-cost user earth station with an ultra-small antenna for easy installation. Since this system utilizes ultra-small antennas, it employs the low-power spread spectrum (SS) scheme in the access link to keep the off-axis equivalent isotropic radiation power below the limit. For efficient use of transponders and frequency, SS signals are superposed on the high-speed TDM forward link signal. To demodulate access link signals under this condition, two novel technologies are introduced. They are the adaptive interference cancellation technique, and the parallel and staggered operation SS demodulation technique. This paper describes system configuration, the new technologies and the results of a system performance evaluation in an experiment. The results of the evaluation demonstrate that superposed transmission over the forward link and low-power access link signals is feasible.

Bi-directional multimedia satellite communication system using ultrasmall user terminals

Abstract NTT started development of a multimedia satellite communication system to provide a medium for Internet access in 1995. This system, which entered commercial service in 1998, uses a hybrid network consisting of a high-speed satellite forward link and terrestrial access links. To meet the increasing demand for low-cost and ubiquitous access links, a second-generation system equipped with satellite transmitting functions is now being developed. The user terminal design calls for a DTH-sized receiver antenna and a transmission power of less than 0.1 W, which will make it suitable for use in homes and small offices. The access link signals from the user terminals are superimposed onto the high-speed TDM forward link signal for efficient use of the frequency band. The transmission power from the user terminal is significantly low compared to that of the forward link signal, a novel interference cancellation technique is introduced. A channel assignment scheme called “channel reservation with rapid release” is introduced for both efficient use of the channels and higher transmission throughput. The forward link signal is completely compatible with the first-generation system, and the data rate is about 30 Mb/s. The paper describes the systems configuration, the central earth stations configuration, and the key technologies of the radio system and access control system.