This letter presents the safety confirmation system based on Near Field Communication (NFC) and Ultra High Frequency (UHF) band Radio Frequency IDentification (RFID) tags. Because these RFID tags can operate without the need for internal batteries, the proposed safety confirmation system is effective during large-scale disasters that cause loss of electricity and communication infrastructures. Sharing safety confirmation data between the NFC and UHF band RFID tags was studied to confirm the feasibility of the data sharing. The prototype of the proposed system was fabricated, confirming the feasibility of the proposed safety confirmation system.

Among many diversity schemes, space and radiation pattern diversity techniques are commonly used in mobile communication systems to overcome deep fading. A novel diagram is presented that clarifies the simultaneous effect of antenna spacing and radiation pattern on the correlation coefficient (ρe). It is shown that space diversity is more effective than radiation pattern diversity. Next, typical examples of practical diversity antenna configurations are shown. A novel configuration for an omnidirectional base station antenna for radiation pattern diversity is explained. Some configurations of space and radiation pattern diversity schemes are shown for mobile stations. A very compact diversity antenna configuration for portable phones is also shown. Finally, for the ease of designing diversity antenna, simple formulas for determining antenna spacing are developed. In the case of base station antennas, the ρe value is expressed by a simple SINC function with variables of spacing and the spread angle of multipath waves. Moreover, typical spread angles are clarified experimentally for Japanese urban areas. The appropriate antenna spacing for small ρe values is obtained. In the case of mobile station antennas, another simple formula is derived by taking into account the mutual coupling between diversity antennas.

The Multi-Point Relay (MPR) of the Optimized Link State Routing protocol reduces the flooding overhead compared with classic flooding. To select MPR nodes, HELLO messages are used. In dense population environments, the overhead of HELLO messages is critical because the HELLO messages carry all adjacent node IDs in the classical manner. Consequently, wireless bandwidth is consumed for data communications. One solution for this problem is to compress HELLO messages using a differential technique. However, few, if any, studies have applied a differential technique to HELLO messages. We introduce the novel Differential HELLO technique to reduce the overhead of the HELLO messages. The Differential HELLO technique consists of two kinds of compression methods: Chronological Compression and Topological Compression. In addition, the inconsistency problems of the 1-hop node information in adjacent nodes caused by packet loss are discussed. As solutions to the inconsistency problems, No Compression Acknowledgement (NC-ACK) and HELLO Information Forecast (HIF) have been examined. Our simulation has taken the efficiency of the Differential HELLO technique into consideration. The HELLO message overhead was reduced to 29.1 IDs from 75.8 IDs using the Differential HELLO technique at a packet loss rate of 10-4 under random node arrangement. This result reveals that the Differential HELLO technique reduces the classic HELLO overhead by 38%. In environments with lower packet-loss rates, the Differential HELLO technique promises to offer even better performance.

For quasi millimeter-wave and millimeter-wave high-speed wireless communications over wireless LANs and wireless ATMs, narrow beam antennas have been shown to provide high transmission quality by suppressing the troublesome multipath effect. However, the diameter of sector antennas needed to create the narrow beams rapidly increases with the sector number. In addition, the cylindrical shape of typical sector antennas does not suit portable terminals. This paper shows a methodology for designing planar sector antennas that overcomes these problems. The proposed antenna uses two kinds of beams and the antenna gains are equalized in all sectors. The antenna is developed as a 4-beam subarray fed by a planar Butler matrix circuit. The design method of the subarray and an evaluation of its characteristics in the 20 GHz band are discussed.

The present study introduces the adaptive BPF to the BPSK coherent detection system and the characteristic of the resulting system is investigated.

We analyze the mutual coupling between two microstrip antennas (MSAs) with the finite-difference time-domain (FDTD) method. It is suitable for substrates which have a complex configuration or include feed line structures. The mutual coupling between two MSAs on discontinuous orthogonal substrates is successfully calculated.

When we use an adaptive array antenna (AAA) with the minimum mean square error (MMSE) criterion under the multipath environment, where the receiving signal level varies, it is difficult for the AAA to converge because of the distortion of the desired wave. Then, we need the equalization both in space and time domains. A tapped-delay-line adaptive array antenna (TDL-AAA) and the AAA with linear equalizer (AAA-LE) have been proposed as simple space-temporal equalization. The AAA-LE has not utilized the recursive least square (RLS) algorithm. In this paper, we propose a space-temporal simultaneous processing equalizer (ST-SPE) that is an AAA-LE with the RLS algorithm. We proposed that the first tap weight of the LE should be fixed and the necessity of that is derived from a normal equation in the MMSE criterion. We achieved the space-temporal simultaneous equalization with the RLS algorithm by this configuration. The ST-SPE can reduce the computational complexity of the space-temporal joint equalization in comparison to the TDL-AAA, when the ST-SPE has almost the same performance as the TDL-AAA in multipath environment with minimum phase condition such as appeared at line-of-sight (LOS).

A 2.45-GHz-band small passive radio-frequency identification (RFID) tag consists of a small loop antenna and chip, and its size is several millimeters. Because of the tag's poor impedance-matching characteristic and radiation efficiency, an ordinary reader has difficulty reading it. We propose a new technique for reading the tag that involves installing a square half-wavelength meander-line conductor on the reader as an adapter and placing the adapter in the vicinity of the tag, and verify the effectiveness of the technique by simulation and experiment. Moreover, characteristics of simultaneous read of the small RFID tags by the proposed reading technique are revealed by simulation and experimental results.

This paper proposes a novel bi-directional rod antenna comprising a narrow patch and parasitic elements for base station antennas of street microcell systems. It is shown that the parasitic elements improve the antenna efficiency of an ordinary bi-directional printed antenna and make it possible to form the antennas using conventional substrates. This paper also proposes a suitable configuration for the array and investigates radiation characteristics of the configuration. Finally, a prototype of the bi-directional rod antenna is presented and the effectiveness of the bi-directional antenna is evaluated.

We propose a novel feeding circuit for a 30 GHz planar multibeam antenna applied to high-speed wireless communication systems. The feeding circuit is a bi-layer 8-port Butler matrix constructed with phase adjusted slot-coupled hybrids and branch-line hybrids. The new circuit configuration eliminates troublesome vias and line crossings, so it can be manufactured by traditional photolithograph. The feeding circuit is designed by using the spectral domain moment method considering bonding film effects. A prototype of a multibeam antenna which has seven pencil-beams with 10 beamwidths is manufactured and tested; the beam scan angle error is less than 3 at 30 GHz.

This paper proposes the use of two transmit and two receive antennas spaced at roughly the width of a human body to improve communication quality in the presence of shadowing by a human body in the 60GHz band. In the proposed method, the transmit power is divided between the two transmit antennas, and the receive antenna that provides the maximum receive level is then chosen. Although the receive level is reduced by 3dB, the maximum attenuation caused by human body shadowing is totally suppressed. The relationship between the antenna element spacing and the theoretical spacing based on the 1st. Fresnel zone theory is clarified. Experiments confirm that antenna spacing several centimeters wider than that given by the 1st. Fresnel zone theory is enough to attain a significant performance improvement.