Naoki Kita

Study of dual-polarized omni-directional antennas for 5.2 GHz-band 2/spl times/2 MIMO-OFDM systems

WLAN systems that use the MIMO-OFDM scheme, which enables high-speed transmission of over 100 Mbps, have been developed and are attracting much attention. The paper proposes novel dual-polarized omni-directional antennas as both the base station and personal station antennas for 5.2 GHz-band 2/spl times/2 MIMO-OFDM systems. The structure of the proposed antennas and their fundamental characteristics, such as input impedance and radiation pattern, are shown. The proposed antennas have overall dimensions of about 10 mm (diameter) and 50 mm (height) and so are very suitable for commercial use. It has been clarified that the shapes of their radiation patterns in the horizontal plane depend on their position relative to the notebook PC: the changes in radiation pattern depend mainly on the main-polarization component. Propagation measurements have been carried out in a typical office using an OFDM-MIMO channel measurement system and the channel capacities of a 2/spl times/2 OFDM-MIMO channel with the different antenna arrangements were elucidated.

Measurement of Demmel condition number for 2/spl times/2 MIMO-OFDM broadband channels

The suitability of a complex multiple-input multiple-output (MIMO) channel matrix for spatial multiplexing (SM) is verified experimentally in terms of the Demmel condition number of the instantaneous MIMO channel matrix. Instantaneous 2/spl times/2 MIMO-orthogonal frequency division multiplexing (OFDM) channel measurements in several indoor environments indicate a location dependency of the Demmel condition number. Wideband frequency characteristics of the Demmel condition number in terms of OFDM sub-carriers are also analyzed to evaluate the applicability of SM in a wideband situation.

A path loss model with height variation in residential area based on experimental and theoretical studies using a 5G/2G dual band antenna

An efficient approach to revealing the propagation characteristics for broadband mobile services in the 5-GHz microwave band is to utilize the existing 2-GHz band propagation data accumulated by many researchers. This paper presents the height variation characteristics at 5.2-GHz compared with that at 2.2-GHz in a residential area based on experiments and theoretical analysis. Propagation measurements were carried out using the dual band antenna at 5.2-GHz and 2.2-GHz, and the measured results were compared. Furthermore, this paper compares the measured results with the calculated results using a two-dimensional (2D) ray-tracing approach based on geometric optics (GO) and the uniform geometrical theory of diffraction (UTD).

Novel wide-band antennas for 2.4/5 GHz dual-band MIMO-OFDM WLAN systems

There have been many studies on the design and development of multi-band antennas for WLAN systems, both in the 2.4 GHz band of IEEE 802.11b/g and in the 5 GHz band of IEEE 802.11a. Many of these studies adopt the approach of using multi-band antennas that support these dual bands, but the bandwidths provided appear to be insufficient. The wide-band antenna is another approach to achieve the desired dual-band, but few reports have studied it. Wide-band antennas that can achieve the bandwidth required are extremely advantageous since they can be manufactured without fine adjustments, such as impedance matching. The paper proposes a novel wide-band antenna, a variant of the conventional discone antenna, for both the base station and the personal station in 2.4/5 GHz-band MIMO-OFDM WLAN systems. The structure of the antennas and their fundamental characteristics, such as the measured S-parameters and radiation patterns of isolated and mounted antennas, are shown for 2/spl times/2 MlMO-OFDM systems.

Experimental study of path loss characteristics in high-speed train cars

The experimental results of the path loss characteristics for intra-car communications in the 2-GHz band and that for inter-car communications for the 5-GHz band in actual high-speed train cars using the THSR were presented. The measured results for intra-car communications indicated that the path loss in train cars is less than that in free space, and indicated a waveguide effect in a confined space environment. In addition, the measured results for inter-car communications indicated that the path loss is largely affected by waves re-entering the car, and level variation such as the Nakagami-Rician fading of K = 8 dB is observed while the train is moving.

New Method for Evaluating Height Gain at Subscriber Station for Wireless Access Systems in Microwave Band

This paper presents a model for the variation in height of the subscriber station (SS) antenna with respect to the path loss for microwave-band wireless access systems. The propagation mechanism that causes the dependency of the height variation characteristics of the received level at an SS on the SS location and operating frequency is clarified in terms of geometrical optics (GO) using the uniform geometrical theory of diffraction (UTD). The height variation characteristics strongly depend on whether or not regular reflected waves that have a higher level than that of the diffracted wave arrive at the SS. A representation of the model is shown. The model is validated using measured data at 2.2, 5.2, and 25.15 GHz and the validity of the model is shown. This model is useful in the radio zone design of microwave-band broadband wireless access (BWA) systems operating in a non-line-of-sight environment, and in estimating the height gain at a mobile station antenna for mobile communications.

2.4/5-GHz dual-band vertically/horizontally dual-polar ized omnidirectional antennas for WLAN base station

This paper proposed a novel antenna configuration to achieve 2.4/5 GHz-dual-band WLAN base station antennas with vertically/horizontally dual-polarized omnidirectional radiation pattern in the horizontal plane. The proposed antenna provides a VSWR of 2 in the 2.4-2.5 and 4.9-6-GHz bands and satisfies all the bands required for the IEEE 802.11n standard. Good omnidirectional radiation patterns are achieved such that the averages of the deviation levels, gain, and XPDs for the radiation patterns in the horizontal plane over both bands for the vertically and horizontally polarized antennas are approximately 2.7 dB, -0.8 dBi, and 14 dB, and 5.5 dB, 0.3 dBi, and 10 dB, respectively.

2.4/5-GHz dual-band horizontally-polarized omni-directional antennas for IEEE 802.11n WLAN base station

This paper proposes a novel circular dipole antenna to achieve 2.4/5-GHz dual-band base station antennas with a horizontally-polarized omni-directional radiation pattern in the horizontal plane that satisfies the wide-band requirement for the IEEE 802.11n standard. The structure of the antennas and their fundamental characteristics such as the measured return loss and radiation patterns of the antennas are shown.

2.4/5 GHz Dual-Band Planar Antennas Mounted on WLAN Card for 3-MIMO-OFDM Systems

This paper proposes a 2.4/5-GHz dual-band horizontally-polarized planar antenna for use in a 3-MIMO antenna configuration OFDM wireless LAN (WLAN) system. The proposed antenna provides a voltage standing wave ratio of 2 in the 2.4-2.5 and 4.9-6 GHz bands when printed on a printed circuit board for commercial PCMCIA or WLAN cards and inserted into a notebook PC. The capacities and correlation coefficients of 3times3 MIMO channels in an indoor multipath LOS/NLOS environment were measured. The results show that the proposed planar antenna is superior to the conventional monopole antenna with respect to channel capacity when polarization matching between the base station and personal station antennas is obtained.

Method for Applying Interlink Correlation to Multilink MIMO Propagation Channel Estimation

This paper proposes a method for applying interlink correlation to evaluate a multiuser-multiple input multiple output (MU-MIMO) system and describes measurement of a multi-link MIMO propagation channel. The proposed method is validated through comparison of measurement results to those of the conventional MIMO propagation channel model. The results show that the proposed method employing the Weichselberger model can handle the interlink correlation property, and accurately reconstructs a MIMO propagation channel.