In order to realize very high throughput wireless local area network (WLAN) systems, which demand multi Gbps capacities/bitrates, the IEEE802.11.TGad (Next generation WLAN standard at 60GHz band) is in the standardization process. To evaluate and select the proposed physical layer modulation and coding schemes in the standardization process, channel models for each specified usage model are required. In this paper, suitable impulse channel models for that purpose are proposed. Propagation measurements are carried out in a living room environment in the 60GHz band. To cover various usage cases, line-of-sight (LOS) and non-line-of-site (NLOS) scenarios and three different signal transmission polarization types are examined, and each channel model's parameters are extracted by statistical analysis. These channel models are useful in designing systems for millimeter-wave wireless communications.

In order to clarify the dual antenna offset channel model needed to transmit multi gigabit/sec streams with directional Tx and Rx antennas at 60 GHz, the paper describes the measurement results of vertical, horizontal and circular polarized signal transmission using co-polarized and cross-polarized directional antennas. Measurement results show that the number of strong reflection waves depends on the polarization type and that the power of cross-polarized wave transmission is very small. These results are useful for developing the novel indoor millimeter-wave channel model that considers AoD, AoA and polarization type.

In order to realize intra-car multimedia communications systems composed of entertainment which requires several hundred Mbps to 1 Gbps capacity and monitoring signal transmission between many parts of the car which requires high reliability and low latency, this paper proposes a millimeter wave system which has high capacity and low latency transmission capability. To clarify the feasibility of millimeter wave systems applications to intra-car multimedia communications, propagation characteristics inside a car have been extensively measured and analyzed. The proposed system sets a car navigator as the center of Intra-car multimedia communications with an Omni antenna and receivers are assumed at front seats, back seats and the luggage space behind the back seats in a typical SUV (Sports Utility Vehicle). The measured results show i. Front seat communications are no worry with simple single carrier (SC) modems without any equalizer, ii. Back seats communications may need beam forming capability for better receive signal power (an Omni antenna system still works with a simple SC modem with a simple rake receiver but without any equalizer, iii. "Luggage space communications may require a directive / beam forming antenna for better receive signal power. The maximum delay spread observed is 6 to 7 ns and no equalizer necessity has been found for Omni antenna receivers inside a car. Further advancement to beam forming antenna will have only 1 - 2 ns maximum delay spread inside a car. Thus, this paper has proved the feasibility of millimeter wave intra-car multimedia communications system by employing a simple single carrier modem without any equalizers but with simple rake receivers.

In order to realize a vehicle area network for multimedia entertainment systems, which demand capacities of up to 1 Gbps, and vehicle control links between many parts of the car, which demand high reliability and low latency, this paper proposes a millimeter-wave system that offers high capacity and low latency transmission. Propagation measurement results show the maximum delay spread of 6 - 7 ns can be achieved with omni antennas without complicated equalizers. Feasible advances in beam forming antenna performance will reduce the maximum delay spread inside the car to only 1 - 2 ns. This paper proves that millimeter-wave vehicle area networks can support multimedia communications as well as control links by employing a basic single carrier modem with simple rake receivers; no equalization is needed.

Proposed PHY layer schemes are evaluated using the channel model that corresponds to each usage model in IEEE802.15.3c standardization process. NICT has contributed TSV model to the IEEE802.15.3c channel model subgroup. The model developed by NICT has been selected as the model for the evaluation of mandatory simulations. This paper describes the channel model for millimeter-wave band developed for the TG3c.

This paper proposes a radio-on-fiber (ROF) based road-vehicle communication system. In the proposed system, several radio base stations (RBSs) are connected with one control station (CS) by an ROF technology. All RBSs use the same frequency band of millimeter-waves to communicate with mobile stations (MSs). Consequently, one virtual large cellular zone based on the millimeter wave band can be constructed using several RBSs controlled by one CS. Based on the virtual large cellular zone, handover is performed. However, in one virtual cellular zone, interference occurs at the boundaries between adjacent cellular zones by RBSs. To overcome the interference, we use code division multiplexing as a modulation scheme to communicate between MSs and RBSs. The feasibility is confirmed by developing an experimental testbed and performing field trials for the downlink, and we discuss the effect of RBS cell size.

A radio-on-fiber (ROF) based road-vehicle communication system is described in which several radio base stations (RBSs) communicate with a control station (CS) over ROF connections. The RBSs use the same millimeter-wave frequency band to communicate with mobile stations (MSs). The result is one large virtual cellular zone encompassing several RBSs controlled by one CS. However, in one virtual cellular zone, interference arises at the bound between adjacent cellular zones because the RBSs in each zone transmit their signals using the same frequency band. To minimize this interference, code division multiplexing is used to modulate the signals sent between the MSs and RBSs. Testing using an experimental course demonstrated that by using this system, we can achieve an error-free continuous communication system with a maximum transmission rate of 4.608 Mbps.

Investigates the effects of antenna radiation patterns at the base station or the remote terminal on the multipath propagation characteristics for the design of millimeter-wave indoor communication systems. These effects were investigated by indoor multipath propagation and BPSK transmission measurements at 60 GHz conducted in a modern office room. Multipath channel characteristics were estimated from impulse responses measured for three types of base-station antennas and for two types of directive terminal antennas with different beam widths. The effects of multipath propagation characteristics on high-speed digital transmission channels were also investigated for almost simultaneously measured bit-error performances at transmission rates of 64, 128, and 256 Mbps. From the results of measurements, the use of directive antennas at the remote terminal and also the use of base station antennas with appropriate radiation patterns were found to be effective for reducing the effect of multipath. It is also found that the reduction of multipath is achieved by the use of circular polarization instead of linear polarization. We also examined the effectiveness of several propagation parameters obtained from multipath propagation measurements for the estimation of the indoor digital transmission characteristics such as bit-error performance.

We have measured, at 57.5 GHz, the reflection and transmission coefficients of typical walls, floor, ceiling, window, and partitions and have compared the measured reflection characteristics with the reflection characteristics estimated by multi-layer dielectric models. Although the positional inhomogeneity of structure types gives rise to some variation from one measured position to another, these positional variabilities are not large, The overall trend of reflection coefficients calculated by multi-layer dielectric models thus mainly agrees well with the trend of the measurements. We have shown that the use of circular polarization can reduce the reflection even if the interior parts of the structure have complicated structures. In addition, the shadowing effects of several types of partitions were measured. The transmission coefficients of partitions depend on the materials. The losses due to plywood partitions are very low, but a metallic partition shields millimeter waves.

Measurements of multipath-propagation characteristics were conducted at 60 GHz in a room within in a modern office building. Delay profiles were measured by a swept frequency method with a high time-delay resolution of 2 ns. Direction-of-arrivals of the multipath components reflected from walls analyzed by rotating a narrow-beam receiving antenna with an angular resolution of 5 degrees. As a result of this experiment, it was found that multipath delayed waves due to wall reflections can be effectively suppressed by employing circular polarization instead of linear polarization. Based on this experimental result, a computer simulation was made to make clear the polarization dependence of the high-speed transmission characteristics of a indoor communications system operating at 60 GHz.>