This article addresses basic issues regarding the design and development of wireless access and wireless LAN systems that will operate in the 60 GHz band as part of the fourth-generation (4G) system. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space (5 GHz) has been allocated worldwide for dense wireless local communications. The article gives an overview of 60 GHz channel characteristics and puts them in their true perspective. In addition, we discuss how to achieve the exploitation of the abundant bandwidth resource for all kinds of short-range communications. The main tenor is that an overall system architecture should be worked out that provides industry with plenty of scope for product differentiation. This architecture should feature affordability, scalability, modularity, extendibility, and interoperability. In addition, user convenience and easy and efficient network deployment are important prerequisites for market success. This article discusses these features and indicates a number of key research topics.

/pdf/exploiting-the-60-ghz-band-for-local-wireless-multimedia-45v66xnl1s.pdf

Exploiting the 60 GHz band for local wireless multimedia access: prospects and future directions

This article presents measurement results and models for 60-GHz channels. Multipath components were resolved in time by using a sliding correlator with 10-ns resolution and in space by sweeping a directional antenna with 7/spl deg/ half power beamwidth in the azimuthal direction. Power delay profiles (PDPs) and power angle profiles (PAPs) were measured in various indoor and short-range outdoor environments. Detailed multipath structure was retrieved from PDPs and PAPs and was related to site-specific environments. Results show an excellent correlation between the propagation environments and the multipath channel structures. The measurement results confirm that the majority of the multipath components can be determined from image based ray tracing techniques for line-of-sight (LOS) applications. For non-LOS (NLOS) propagation through walls, the metallic structure of composite walls must be considered. From the recorded PDPs and PAPs, received signal power and statistical parameters of angle-of-arrival and time-of-arrival were also calculated. These parameters accurately describe the spatial and temporal properties of millimeter-wave channels and can be used as empirical values for broadband wireless system design for 60-GHz short-range channels.

Spatial and temporal characteristics of 60-GHz indoor channels

A comprehensive review of the propagation prediction models for terrestrial wireless communication systems is presented in this paper. The classic empirical models are briefly described and the focus is placed on the application of ray-tracing techniques to the development of deterministic propagation models. Schemes to increase the computational efficiency and accuracy are discussed. Traditional statistical models are also briefly reviewed for completeness. New challenges to the propagation prediction are described and some new approaches for meeting these challenges are presented.

Propagation prediction models for wireless communication systems

The millimeter wave (mmWave) frequency band spanning from 30 to 300 GHz constitutes a substantial portion of the unused frequency spectrum, which is an important resource for future wireless communication systems in order to fulfill the escalating capacity demand. Given the improvements in integrated components and enhanced power efficiency at high frequencies, wireless systems can operate in the mmWave frequency band. In this paper, we present a survey of the mmWave propagation characteristics, channel modeling, and design guidelines, such as system and antenna design considerations for mmWave, including the link budget of the network, which are essential for mmWave communication systems. We commence by introducing the main channel propagation characteristics of mmWaves followed by channel modeling and design guidelines. Then, we report on the main measurement and modeling campaigns conducted in order to understand the mmWave band’s properties and present the associated channel models. We survey the different channel models focusing on the channel models available for the 28, 38, 60, and 73 GHz frequency bands. Finally, we present the mmWave channel model and its challenges in the context of mmWave communication systems design.

/pdf/millimeter-wave-communications-physical-channel-models-qh94bqmhc1.pdf

Millimeter-Wave Communications: Physical Channel Models, Design Considerations, Antenna Constructions, and Link-Budget

Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency patch antennas is presented, and future perspectives are outlined. Geometries are discussed in particular.

/pdf/dual-frequency-patch-antennas-105ucby5ij.pdf

Dual-frequency patch antennas

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 multilayer dielectric models. Although the positional inhomogeneity of structures 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 multilayer dielectric models thus agrees fairly 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 transmission losses of plywood-made partitions are found to be fairly low.

Measurements of reflection and transmission characteristics of interior structures of office building in the 60-GHz band

In a radio equipment of portable type, the impedance of an antenna is optimized by adjusting a matching circuit which has the adjustment function and is connected to an antenna, based on a reflection phase sent back from the antenna, outputted from a reflection phase detector, and a current supplied to a transmitter-receiver which generates a transmitting signal.

Portable type radio equipment

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 reflection and transmission characteristics of interior structures of office building in the 60 GHz band

A patch having a circular shape for instance is formed on the main surface of a substrate in the shape of, for example, an equilateral triangle. The center of the main surface of the patch is at a position different from the center of the substrate. A grounding conductor is disposed on the backside of the substrate. Power is supplied to the patch through, for example, a microstrip line, triplate line, coplanar waveguide, slot line or the like. An antenna configured as described above has the center of the patch at a position different from the center of the triangle substrate, so that beams can be tilted in a desired direction by a single patch and a single feeder circuit.

Antenna capable of tilting beams in a desired direction by a single feeder circuit, connection device therefor, coupler, and substrate laminating method

An active array antenna system comprises a plurality of element antennas and radio frequency circuits connected to the element antennas. The radio frequency circuits comprises first frequency converters provided to correspond to the element antenna and converts the frequency between a carrier-wave frequency and a first intermediate-frequency by using a carrier-wave frequency band local signal, second frequency converters provided to correspond to the element antenna and converts the frequency between the first intermediate-frequency signal and a second intermediate-frequency which is lower than the first intermediate frequency by using an intermediate-frequency band local signal, and a variable phase shifter circuit for individually controlling the phases of the intermediate-frequency local signals which are supplied to the second frequency converters. A variable phase shifter circuit for beam scan can be constituted at a low cost so that an active array antenna system which can be realized at a low cost is provided.

Yasushi Murakami

Papers

Measurements of reflection and transmission characteristics of interior structures of office building in the 60-GHz band

Portable type radio equipment

Measurements of reflection and transmission characteristics of interior structures of office building in the 60 GHz band

Antenna capable of tilting beams in a desired direction by a single feeder circuit, connection device therefor, coupler, and substrate laminating method

Active array antenna system