Aki Karttunen

A Statistical Spatio-Temporal Radio Channel Model for Large Indoor Environments at 60 and 70 GHz

Millimeter-wave radios operating at unlicensed 60 GHz and licensed 70 GHz bands are attractive solutions to realize short-range backhaul links for flexible wireless network deployment. We present a measurement-based spatio-temporal statistical channel model for short-range millimeter-wave links in large office rooms, shopping mall, and station scenarios. Channel sounding in these scenarios at 60 and 70 GHz revealed that spatio-temporal channel characteristics of the two frequencies are similar, making it possible to use an identical channel model framework to cover the radio frequencies and scenarios. The sounding also revealed dominance of a line-of-sight and specular propagation paths over diffuse scattering because of weak reverberation of propagating energy in the scenarios. The main difference between 60 and 70 GHz channels lies in power levels of the specular propagation paths and diffuse scattering which affect their visibility over the noise level in the measurements, and the speed of power decay as the propagation delay increases. Having defined the channel model framework, a set of model parameters has been derived for each scenario at the two radio frequencies. After specifying the implementation recipe of the proposed channel model, channel model outputs are compared with the measurements to show validity of the channel model framework and implementation. Validity was demonstrated through objective parameters, i.e., pathloss and root-mean-square delay spread, which were not used as defining parameters of the channel model.

Antenna Tests With a Hologram-Based CATR at 650 GHz

A hologram-based compact antenna test range (CATR) is designed, constructed, and used to test a 1.5-m antenna at 650 GHz. The CATR is based on a 3.16-m-diameter hologram as the collimating element. So far, this is the highest frequency at which any CATR has been used for antenna tests. The quiet zone is measured and optimized before the antenna tests. The measured antenna pattern results at 650 GHz are analyzed and compared to the simulated patterns. Feed scanning antenna pattern comparison technique is used to correct the antenna pattern. These tests show the hologram CATR to be promising for antenna measurements up to 650 GHz.

2-D Beam-Steerable Integrated Lens Antenna System for 5G

The new services available through smart devices require very high cellular network capacity. The capacity requirement is expected to increase exponentially with the forthcoming 5G networks. The only available spectrum for truly wideband communication (>1 GHz) is at millimeter wavelengths. The high free space loss can be overcome by using the directive and beam-steerable antennas. This paper describes a design and the measurement results for a lens antenna system for E-band having 2-D beam-steering capability. Continuous beam-switching range of about ±4° × ±17° is demonstrated with the lens having the maximum measured directivity of 36.7 dB. Link budget calculation for backhaul application using the presented lens antenna system is presented and compared with the measurement results of the implemented demo system.

E

Mutual orthogonal user channels in multiuser (MU)-multiple-input multiple-output (MIMO) systems are desirable and can be approximately obtained under independent and identically distributed (i.i.d.) Rayleigh fading assumption with a very large number of base station antennas. However, it has been shown that at millimeter-wave (mmW) frequencies, this assumption is not valid due to the limited number of multipath components and spatial channel correlation. In this paper, we examine the mutual orthogonality of a realistic 60-GHz outdoor propagation channel with practical large antenna arrays, and determine the factors deciding it based on the channel data generated by means of deterministic field prediction. The results obtained reveal relationships between mutual orthogonality, inter-user distance, number of active users, transmit array dimensions, and downlink system capacity at 60-GHz band, which are useful for designing future mmW massive MU-MIMO systems.

-Band Access and Backhaul

In this paper, we derive parameters of the WINNER II channel model for a shopping mall environment at 60 GHz band, covering both line-of-sight and obstructed-line-of-sight scenarios. The model parameters are derived mostly based on channel measurements reported in this paper. Due to a large measurement bandwidth and the highly specular nature of the channel in the shopping mall, only weak clustering effects of propagation paths are found. Still, we demonstrate that the WINNER II model structure is applicable to 60 GHz channel modeling since the model reproduces the measured channels well.

On the Mutual Orthogonality of Millimeter-Wave Massive MIMO Channels

A compact antenna test range (CATR) based on a radio frequency hologram is a potential method for testing high-gain antennas at submillimetre wavelengths. Within a European Space Agency (ESA) project, a 1.5 m reflector antenna, ADMIRALS Representative Test Object (RTO), will be tested at 650 GHz during autumn 2006. For these antenna tests, MilliLab / Radio Laboratory at the Helsinki University of Technology (TKK) is designing and constructing a CATR based on a binary amplitude hologram having a diameter of 3.16 m. The designed quiet-zone width is about 2 m. A plane-polar scanner is designed for the quiet-zone field verification. The dynamic range is estimated to be 32 dB in the quiet-zone field tests and 78 dB in the tests of the high-gain test antenna.

Radio Propagation Measurements and WINNER II Parameterization for a Shopping Mall at 60 GHz

Site-specific millimeter-wave propagation prediction requires data of the environment under study, which is usually not available for indoor scenarios. With means of laser scanning the details of the indoor environment can be captured accurately in the form of a point cloud. The total field is estimated as a sum of paths backscattering from the point cloud, where the electromagnetic scattering for each path is calculated with a single-lobe directive model. In this paper we focus on predicting the radio wave propagation in a large office environment at 70 GHz, where the accuracy is evaluated by comparing measured and predicted mean delays and delay and azimuth spreads. We also present a method for dealing with shadowing in the indoor environment. The results show good agreement between measured and predicted delay and azimuth spreads for line-of-sight links, and also non-line-of-sight links can be predicted with reasonable accuracy.

Development of a hologram-based CATR for testing a very high gain antenna at 650 GHz

The conventional integrated lens antennas (ILAs) for beam steering sufier from internal re∞ections that deteriorate the scanning properties. The internal re∞ections are known to afiect side lobes, cross-polarisation level, input impedance of the feed, and mutual coupling. In this paper, ILAs are designed to exhibit very low re∞ection loss, i.e., to minimize the internal re∞ections. Wide ranges of realistic relative permittivities of the lens and of the feed element directivities are considered. It is shown that with any permittivity and with any feed directivity it is possible to design the lens shape in such a way that the re∞ection loss is low, for moderate beam-steering angles, without resorting to a complicated matching layer. The gain, directivity, beam-width, and the resulting distance between the feed elements are compared for all the designed lenses.

70 GHz Radio Wave Propagation Prediction in a Large Office

We have studied beam-steering radio in the E-band., e.g. for high-capacity communication links. Lens antennas provide high gain and are suitable for integration at millimeter wave frequencies, e.g., for beam-switching a planar antenna array with a switching network may be integrated to the surface of the lens; one patch is activated at a time for each beam direction. In order to improve the scanning characteristics and reduce reflection losses, we have studied optimization of the lens shape using ray tracing. A propagation channel model has been developed for point-to-point links in street canyons and from roof to street in an urban environment. The model is based on extensive measurements in the E-band. The substance of the channel model is in identification of multipath components in the environment. That is supported by separate measurements of radio wave reflection and scattering from various environmental structures such as building walls.

Reduction of internal reflections in integrated lens antennas for beam-steering

A brief review of antenna test methods at THz frequencies is presented. Two hologram-based compact antenna test ranges (CATR), one at 322 GHz and another at 650 GHz were designed, constructed, and used for testing the ADMIRALS RTO antenna of 1.5 m in diameter. These CATRs are based on 3-meter diameter computer-generated amplitude holograms.