Atsuya Ando

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.

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.

Propagation loss, XPR, and height pattern characteristics on road from antennas set in manhole

Telecommunication carrier corporations have many underground manholes that accommodate communication facilities such as metal cables and so-called “optical cable closures” that are equipped with optical fibers. Much time and energy must be devoted to the maintenance of these underground facilities. It is expected that inspecting and supervising underground facilities would be facilitated by establishing radio wireless links between the manhole chamber and above ground using some wireless device, e.g., RF-ID tag. There have been some studies that tried to establish a wireless link by modifying the manhole covers [1] or tried detecting the manhole locations [2]-[3]. The radiation from an antenna in a manhole was investigated mainly using the Finite Integral Time Domain (FITD) simulation in [4], but the propagation characteristics we re not thoroughly studied. This paper reports the measurement results of propagation characteristics on a road from an antenna set in a manhole. The structure of the manhole and measured results of fundamental propagation characteristics such as the propagation loss, cross-polarization power ratio (XPR), shielding effect of the manhole cover on the propagation loss behavior, and height pattern of the received signal levels above ground are presented.

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.

Empirical formula of effect on channel estimation error for adaptive MIMO-OFDM based WLAN system

The IEEE802.11a standard for indoor wireless LAN systems was released commercially and is wide spread in the marketplace. To achieve higher throughput, IEEE802.11n was proposed and is now undergoing standardization. The MIMO-OFDM technique, which employs multiple antennas for transmission and reception, is the core technology for IEEE802.11n (Foshini and Gans, 1998). This technique requires estimation of channel state information (CSI) on the receiving side. Using the technique called adaptive MIMO-OFDM (Telatar, 1999) in which CSI is applied to both the transmitting and receiving sides, an even higher throughput is achieved. To achieve the maximum performance from adaptive MIMO-OFDM, we must accurately estimate the CSI for all the subcarriers; however, numerous calculations are needed to obtain this estimation. So, to actualize the adaptive MIMO-OFDM system, the calculation load must be decreased. This can be accomplished by applying one CSI to other subcarriers. However, channel error exists between the actual channel and the applied CSI. The channel error also plays a role in decreasing the communications quality (Medard, 2000). The communications quality when using the adaptive MIMO-OFDM technique that has CSI error was evaluated by simulation (Narula et al., 1998). However, there are few measurement evaluation reports on CSI error. This paper focuses on the ratio between the power of the eigenvalue and the interference power that suppresses the communication quality based on the measurement results. We propose an empirical formula for predicting the signal to interference ratio (SIR), which is the ratio between the power of the eigenvalue and the interference power. This SIR empirical formula helps to predict the communication quality and simplify the simulation.