Jarmo Kivinen

Millimeter-Wave Propagation Channel Characterization for Short-Range Wireless Communications

This paper presents and analyzes the results of millimeter-wave 60-GHz frequency range propagation channel measurements that are performed in various indoor environments for continuous-route and direction-of-arrival (DOA) measurement campaigns. The statistical parameters of the propagation channel, such as the number of paths, the RMS delay spread, the path loss, and the shadowing, are inspected. Moreover, the interdependencies of different characteristics of the multipath channel are also investigated. A linear relationship between the number of paths and the delay spread is found, negative cross correlation between the shadow fading and the delay spread can be established, and an upper bound exponential model of the delay spread and the path loss is developed to estimate the worst case of the RMS delay spread at given path loss. Based on the DOA measurements that are carried out in a room [line of sight (LOS)] and in a corridor with both LOS and nonline-of-sight (NLOS) scenarios, radio-wave propagation mechanisms are studied. It is found that considering the direct wave and the first-order reflected waves from smooth surfaces is sufficient in the LOS cases. Transmission loss is very high; however, diffraction is found to be a significant propagation mechanism in NLOS propagation environments. The results can be used for the design of 60-GHz radio systems in short-range wireless applications.

Propagation characteristics for wideband outdoor mobile communications at 5.3 GHz

In this paper, empirical channel models and parameters are derived from the wideband measured data at 5.3 GHz in outdoor mobile communications. The path loss exponents and intercepts are obtained by using the least square method. The mean excess delay and mean root-mean-square (rms) delay spread are within 29-102 ns and 22-88 ns, respectively. The correlation distances and bandwidths are within 1-11 /spl lambda/ and 1.2-11.5 MHz, respectively, when the envelope correlation coefficients equal 0.7 in line-of-sight cases. These correlation values depend strongly on the base station antenna heights. The window length for averaging out the fast fading components is about 1-2 m for microcells and picocells. The multipath number distributions follow both Poissons and Gaos distributions, but Gaos distribution is better in the high probability region. Large excess delays up to 1.2 /spl mu/s and rms delay spread about 0.42 /spl mu/s are found in the urban rotation measurements, where the receiver is close to a large open square.

Empirical characterization of wideband indoor radio channel at 5.3 GHz

Characteristics of wideband indoor radio channel at 5.3 GHz were defined based on an extensive measurement campaign using a wideband channel sounder with 19 ns delay resolution. Pathloss exponents were 1.3-1.5 in LOS and 2.9-4.8 in non-line of sight (NLOS). Large difference in NLOS exponents was due to different dominating propagation mechanisms in different types of building structures. The delay dispersion was characterized by cumulative distribution functions (CDF) of the RMS delay spreads, the values for CDF=0.9 varied from 20 to 180 ns in different setups in an office building and large hall environments. The correlation functions of the radio channel in spatial and frequency domains were extracted. Small scale models for five typical indoor scenarios were developed using tapped delay lines.

Comparison of MIMO antenna configurations in picocell and microcell environments

This paper presents the results achieved with a dual-polarized multiple-input multiple-output (MIMO) measurement system in the 2 GHz range. Results from continuous measurement routes were used in evaluating and comparing different MIMO antenna configurations. Different pattern and polarization diversity possibilities were studied using two methods: elements were selected from the antenna arrays used in measurements, and as another option, in the mobile station the incident waves were estimated and used in different dipole antenna arrays. The capacity limit seems to be higher in an indoor picocell than in an outdoor microcell environment. At the mobile station, directive elements result in 35% higher average capacities than those of the omnidirectional elements; however, the capacity of the directive elements also depends on the azimuth direction of arrival of the incident field. Dual-polarized antenna configurations have approximately 14% higher capacities than copolarized configurations. Increasing the number of mobile antenna elements increases the capacity in those environments where the angular spread of the incident field is large. Increasing the distance between elements at the fixed station increases the capacity - especially in microcells where signals arrive from specific directions.

Characterization of Doppler spectra for mobile communications at 5.3 GHz

Tapped-delay-line (TDL) channel models are developed from a measured database for outdoor and indoor mobile communications at 5.3 GHz. Meanwhile, several types of Doppler spectra are found at the different taps of the TDL models. For simulation purposes, a general three-dimensional autocorrelation function of the scattered waves is derived and connected to the distributions of angles of arrival of the waves and antenna radiation patterns. Furthermore, the propagation mechanisms of the different types of Doppler spectra observed in the TDL models are explained based on the comparisons between measured and simulated results where the Fourier transformations are performed on the autocorrelation functions to obtain the Doppler power spectra.

Wideband radio channel measurement system at 2 GHz

This paper describes the wideband radio channel sounding techniques for mobile radio channel measurements. Implementation of the cross-correlation method using both a sliding correlator and a matched filter detector is presented. Limitations and accuracy of radio channel measurements are discussed. Typically, delay resolution of about 20 ns is achieved with 100 MHz bandwidth. With a sliding correlator, a dynamic range of 25 dB was obtained with maximum Doppler bandwidth of 25 Hz and maximum excess delay of 19 /spl mu/s. Digital matched filtering with a maximum sampling rate of 125 MHz can be used in real-time measurements with Doppler shifts of several kilohertz and 30 dB dynamic range. Using matched filter deconvolution as a resolution enhancement technique is discussed. Examples of the time-variant complex impulse response measurements are given.

5.3 GHz MIMO radio channel sounder

A radiowave propagation measurement system for wideband multichannel multiple-input-multiple-output (MIMO) measurements at 5.3 GHz is presented. The MIMO channel matrix of size 32/spl middot/32 can be measured using microwave switches at the transmitter (TX) and the receiver (RX). The system is capable of measuring direction of departure and direction of arrival with a dual polarization in both TX and RX. The antenna configuration can be selected to include a planar array or semispherical groups at each end of the link. A high-power switch is used at TX to enable large measurement distances. Results from a calibration in an anechoic chamber and from the measurement campaigns are shown.

Comparison of MIMO Antenna Configurations: Methods and Experimental Results

In this paper, the methods for comparing multipleinput-multiple-output (MIMO) antenna configurations using measured radio channels are considered. The expression of mutual information (MI) is factorized to give better understanding of the ability of MIMO antenna systems to transfer signal power, as well as to utilize parallel channels. An appropriate power normalization of channel matrices is shown to have a profound impact on the ranking of particularly directive MIMO antennas. It was found that the ability to transfer signal power from the transmitter to the receiver, instead of the rank properties, dominates in outage MI over a wide range of signal-to-noise ratios. The largest differences in outage MI between the antennas were found at low outage-probability levels, particularly in the line of sight. It was also verified that dual-polarized antenna systems are more robust for environmental variations but more sensitive for antenna orientation in comparison with single-polarized antenna systems both in eigenvalue dispersion and transferred signal power. At low outage-probability levels, the highest MI was achieved with vertically polarized dipole antennas.

Millimeter-Wave MIMO Radio Channel Sounder

Nowadays, the need for high-data-rate-communication channels is increasing and will ineluctably continue to increase in the future. From a theoretical point of view, the multiple input multiple output (MIMO) approach seems to be one of the best solutions to provide such a high capacity. This paper presents a millimeter-wave MIMO channel measurement system developed in the Radio Laboratory of Helsinki University of Technology. The system is based on a sounder and virtual antenna arrays: The antenna arrays are obtained by two 2-D scanners which shift a single transmit antenna and a single receive antenna. Measurements in line of sight (LOS) and non-LOS are reported from what the MIMO channel capacity is calculated for various antenna array sizes. Furthermore, from the same measurements, the direction of departure and direction of arrival are estimated

Polarization Behaviours at 2, 5 and 60 GHz for Indoor Mobile Communications

The behaviours of linear polarizations at 2.15, 5.3 and 61.7 GHz in corridors are studied in this paper. It shows that there is no significant difference between the received powers for vertical and horizontal polarizations. Depolarization is obvious at 2.15 GHz due to different antenna type is applied at the receiver, and it is more serious in non-line-of-sight (NLOS) cases.