Jan-Erik Berg

Propagation Characteristics of Polarized Radio Waves in Cellular Communications

Narrowband and wideband measurements of the radio channel using different combinations of transmit and receive polarization have been performed. The measurements cover a range of scenarios including urban, suburban and open terrain, as well as both outdoor and indoor terminals. The vertical-to-vertical (V-V) and horizontal-to-horizontal (H-H) polarization combinations are found to provide equal received power on average, while the cross-polarized combinations (V-H) and (H-V) typically provide 5-15 dB weaker received power due to the limited amount of cross-polarization scattering in the radio channel. Fast fading variations are further found to be uncorrelated between different combinations of transmit and receive polarization.

Carrier Frequency Effects on Path Loss

To study the carrier frequency effects on path loss, measurements have been conducted at four discrete frequencies in the range 460-5100 MHz. The transmitter was placed on the roof of a 36 meters tall building and the receive antennas were placed on the roof of a van. Both urban and suburban areas were included in the measurement campaign. The results show that there is a frequency dependency, in addition to the well known free-space dependency 20 log10(f), in most of the areas included in the measurements. In non line of sight conditions, the excess path loss is clearly larger at the higher frequencies than at the lower. A model capturing these effects is presented

Non-line-of-sight small cell backhauling using microwave technology

In this article we discuss different technology alternatives for small cell backhaul, and we present high-frequency microwave technology as a very interesting alternative for wireless backhauling of small cells. In fact, we demonstrate that high-frequency microwave technology can be used for NLOS wireless backhauling of small cells, which opens up new applications for microwave technology. We discuss urban NLOS channel propagation at high frequencies, and we show both measurement and simulation results to validate the use of high-frequency microwave technology for NLOS small cell backhaul.

MIMO channel characteristics in a small macrocell measured at 5.25 GHz and 200 MHz bandwidth

The purpose of this work is to improve the radio channel characterization in macrocellular scenarios. The effort has been put on the wideband and MIMO aspects. Measurements have been performed at two outdoor and three indoor locations at 5.25 GHz with bandwidth of 200 MHz using a vector network analyzer. An optical fiber was used to achieve distances between transmitter and receiver up to 300m. The channel parameters were estimated by means of maximum likelihood estimation, modeling the channel with a set of discrete plane waves. Based on the estimates joint double directional, delay and polarimetric distributions were determined. Moreover, clustering and statistical distribution of path amplitudes were studied.

Temporal radio channel variations with stationary terminal

In wireless communications, stationary terminal scenarios are becoming increasingly important as bitrates goes up. Consequently, the need to improve the knowledge about the channel behavior and to develop realistic channel models for these scenarios is also increasing. The present work comprises both measurements and modeling of the radio channel when the terminal is stationary. The measurements were performed at 5 GHz in indoor scenarios using a vector network analyzer. The measured channel was essentially static most of the time. Only about 1% of the time did it show substantial channel variations. An important finding is that the dominant cause for temporal channel variations in the measurements was the movement of persons in the vicinity of either antenna. This is also supported by a simple model, based on a single moving scatterer, which shows good agreement with measurements.

Small-Cell Wireless Backhauling: A Non-Line-of-Sight Approach for Point-to-Point Microwave Links

In this paper we investigate the feasibility of using microwave frequencies for fixed non-line-of-sight wireless backhauling connecting small-cell radio base stations with an aggregation node in an outdoor urban environment, i.e. a typical heterogeneous network scenario. We study system level simulations for a point-to-point system where the wave propagation is based on diffraction over rooftops. We further investigate the effects of carrier frequency, interference, antenna height, rain, and tolerance to antenna alignment errors. It is found that the higher frequencies offer not only larger bandwidths but also higher antenna gains which would ideally work to their advantage. However, these advantages may be lost when taking antenna alignment errors and rain into account. Different frequencies simply have their different trade-offs.

Statistical analysis of measured radio channels for future generation mobile communication systems

Measurements of radio channels with 100 MHz bandwidth at 5.25 GHz have been performed in both indoor and outdoor environments. The statistical properties of the tap amplitudes have been analyzed together with general channel characteristics, such as path loss, delay spread and coherence bandwidth. With 100 MHz bandwidth, it was found that the average power delay profile consists of several delay time clusters. The tap amplitudes follow Rice or Nakagami statistics for some taps in the beginning of the clusters while the other taps are close to Rayleigh fading. An approach to model the average power delay profile and the frequency correlation is also presented.

Validation of 3GPP Spatial Channel Model Including WINNER Wideband Extension Using Measurements

This paper is intended to validate the 3GPP spatial channel model (SCM) and the corresponding WINNER wideband extension (SCME) by comparisons with measurement data. Basically the models are validated. The main channel characteristics in terms of angular, delay and polarimetric distributions are confirmed. Moreover, the corresponding MIMO channel capacities are also validated as the agreement with the measurements is good. However, some model deficiencies are identified such as missing important scenarios, like the outdoor-to-indoor scenario for which measured MIMO capacities are substantially lower than those of the SCM/SCME models.

60 GHz channel directional characterization using extreme size virtual antenna array

In order to provide reliable knowledge about highly resolved directional properties of the radio propagation channel, straight forward beam-forming has been used in this study. Accurate measurement data based on an extreme size virtual antenna array (25×25×25 = 15625 elements) have been provided for an indoor scenario in both line of sight and non-line if sight conditions. The results indicate that the distinct spikes observed in the power-delay profile are caused mainly by specular reflections. There is however also a significant diffuse contribution due to scattering caused by the many smaller objects of the environment. The diffuse paths are spread out in essentially all azimuth and elevation directions except for the empty parts of the floor.

Non-Line-of-Sight 2.6GHz Relay Backhaul Channel Performance: Field Test and Analysis

Relay technologies have been standardized in 3GPP long term evolution (LTE), and can be a useful tool for coverage extension in diverse deployments. The backhaul channel between the relay and its donor eNodeB is essential to the end-to-end relay performance. Recently there has been an increased interest in deployments with non-line-of-sight (NLoS) backhaul channel conditions. In this paper, the NLoS backhaul channel quality has been measured in the real field, and the results show that NLoS backhaul has obvious gain over donor-UE channel and can be good enough to support relay data forwarding. Rules of thumb for NLoS relay deployment are identified that can help to minimize the diffraction loss or to utilize the strong reflections to improve the channel quality.