Lassi Hentilä

WLC06-2: Cluster-Based MIMO Channel Model Parameters Extracted from Indoor Time-Variant Measurements

This paper presents a complete solution to the problem of how to parametrise cluster-based stochastic MIMO channel models from measurement data, with minimum user intervention. The method comprises the following steps: (i) identify clusters in measurement data, (ii) identify the optimum number of clusters, (iii) track clusters over consecutive time snapshots, (iv) estimate cluster parameters. These parameters are given as estimated probability density functions of the cluster power, cluster positions, delay and angular spreads of clusters and the number of paths within a cluster. Applied to high-resolution indoor MIMO measurement data at 5.2 GHz and at 2.55 GHz, the method yields coherent results of the obtained cluster parameters.

Empirical Models and Parameters for Rural and Indoor Wideband Radio Channels At 2.45 and 5.25 GHZ

The modeling results from wideband radio channel measurements are presented for two environments: rural and indoor. The paper focuses on the average and instantaneous characteristics of received power including: path loss, shadow fading, power delay profiles, and rms delay spreads. Furthermore, the cross correlation between shadowing of the path loss and the delay spread is investigated and found to be large. Doppler measurement campaigns were conducted in both environments, at 2.45 GHz and 5.25 GHz along the same measurement routes, with 100 MHz bandwidth. In this paper it is shown that we may apply 2.45 GHz band small scale models into 5.25 GHz band. It can be also seen, as for the measured scenarios, on average, the difference in terms of path loss between 2.45 GHz and 5.25 GHz in line-of-sight indoor environment, where waveguide effect is encountered, is c.a. 8 dB, instead in rural outdoor the mentioned difference is c.a. 6 dB

Correlations of Wide-Band Channel Parameters in Street Canyon at 2.45 and 5.25 GHz

The correlation between channel parameters root mean square delay spread (DS), shadow fading, number of clusters, and Rician factors (K-factors or K) is investigated based on wide-band channel measurements. The channel measurements were performed at 2.45 and 5.25 GHz in long line-of-sight (LOS) and non-LOS (NLOS) street canyons. The relation of the channel parameters to distance is illustrated. Very high correlation between channel parameters was found in the LOS street canyon, while much lower correlation was found in the NLOS street canyon. The linear relationship between the DS and the other channel parameters is derived in the LOS case, thus allowing the use of one channel parameter (e.g., the DS) to predict the others.

Cluster-level parameters at 5.25 GHz indoor-to-outdoor and outdoor-to-indoor MIMO radio channels

This paper describes cluster-level results of indoor-to-outdoor and outdoor-to-indoor double-directional MIMO radio channel measurements carried out at 5.25 GHz. The measurements were performed using a wideband multi-antenna radio channel sounder. Using a set of several thousands of snapshots at the two reciprocal environments, we provide a useful insight into the channel for further channel modelling and channel simulations. We discuss the cluster azimuth spread, cluster delay spread, inter-cluster shadowing, number of clusters per snapshot, number of paths within the cluster, cluster birth rate and cluster lifetime. These parameters are presented for different scenarios by their statistical distributions, and also by their cross-correlation. The results show that both outdoor-to-indoor and indoor-to-outdoor scenarios behave very similar, so we suggest to merge these two cases.

Rician Channel Modeling for Multiprobe Anechoic Chamber Setups

This letter discusses over-the-air (OTA) testing for multiple-input-multiple-output (MIMO)-capable terminals, with emphasis on modeling Rician channel models in the multiprobe anechoic chamber setups. A technique to model Rician channels is proposed. The line-of-sight (LOS) component, within arbitrary polarization and an arbitrary impinging direction, and non-LOS (NLOS) component, with any impinging power angular spectrum (PAS), can be created. Simulation results show that the emulated Rician channels approximate the target models accurately in terms of field envelope distribution, K-factor, Doppler spectrum, and spatial correlation at the receiver (Rx) side.

A measurement-based random-cluster MIMO channel model

We present a novel geometry-based stochastic MIMO channel model based on the concept of multipath clusters. The so-called random-cluster model (RCM) represents the channel in a propagation-based stochastic way, in which the geometry enters solely by statistical means. The starting point is the recently published parametric COST 273 MIMO Channel Model. However, instead of using physical parameters (e.g. rooftop height or scatterer distance), our model requires only cluster parameters. As another major feature beyond COST 273, the model can now be parametrized directly from measurements. The model presently supports multi-user packet access, i.e. the channel changes completely from one time instant to another. Simple future extensions will incorporate smoothly time-variant channels as well.

The interdependence of cluster parameters in MIMO channel modeling

Novel geometry-based stochastic MIMO channel models like the COST 273 model are using multipath clusters to model the propagation paths of the channel. Recently, we introduced a novel framework to identify and track clusters automatically. MIMO measurements from various scenarios are currently evaluated in several laboratories to parametrize the models. From processing indoor measurements at 2.55 GHz and 5.25 GHz, we found that cluster parameters show significant correlations which have to be considered in the channel models in order to be physically relevant. In detail we observed strong positive correlation between cluster power and the number of paths within a cluster, and between all the cluster spread parameters, while we observe negative correlation between the number of clusters and the cluster spreads.

Comparisons of Channel Parameters and Models for Urban Microcells at 2 GHz and 5 GHz [Wireless Corner]

The goal of this paper was to find the differences of the channel models and parameters as well as the correlations of the channel parameters between 2 GHz and 5 GHz with 100 MHz bandwidth when measurements were performed in exactly the same routes for urban microcells. The path-loss models and shadow fading were studied by using single-input single-output (SISO) measurements. The channel characteristics were investigated by the rms delay spread, rms angular spread, shadow fading, Ricean factor, number of clusters, cross-polar discrimination, and channel capacities using both SISO and MIMO (multiple-input multiple-output) measurements. Static measurements at 5 GHz were also performed in both micro- and macro-cells to investigate clustering effects. Moreover, the channel models and parameters were compared with WINNER work to test their validity in urban microcells. The main conclusion was that the 2 GHz and 5 GHz frequencies can have different propagation behaviors causing the independent channel parameters. However, it was found that their coherence bandwidths were highly correlated. The WINNER path-loss models over-estimate the path losses, both in the line-of-sight (LOS) and non-line-of-sight (NLOS) street canyons where strong guided waves exist. Irrespective of carrier frequencies, the channel parameters offered by WINNER may roughly estimate the channel by implementing its generic model.

Evaluation of beam forming and multi antenna techniques in non-stationary propagation scenarios with HW emulator

This paper discusses a three-dimensional (3D) non-stationary channel modelling for the evaluation of multi antenna techniques with a hardware (HW) fading emulator or a software (SW) simulator. The proposed geometric stochastic channel modelling (GSCM) principle supports single or multi link emulations with both measured or simulated antenna patterns and dynamically evolving propagation environments. The modelling principle considers, e.g., 3GPP SCM(E), WINNER II, IMT-Advanced and WINNER+ channel models. The novelty of the paper is in the creation of smoothly evolving propagation and antenna orientation parameters with a linear interpolation of the specified location snapshots. We measured a throughput in four different non-stationary channels but also did a throughput comparison in 2D and 3D urban micro channel models.

Emulating Realistic Bidirectional Spatial Channels for MIMO OTA Testing

This paper discusses over the air (OTA) testing for multiple input multiple output (MIMO) capable terminals with emphasis on modeling bidirectional spatial channel models in multiprobe anechoic chamber (MPAC) setups. In the literature, work on this topic has been mainly focused on how to emulate downlink channel models, whereas uplink channel is often modeled as free space line-of-sight channel without fading. Modeling realistic bidirectional (i.e., both uplink and downlink) propagation environments is essential to evaluate any bidirectional communication systems. There have been works stressing the importance of emulating full bidirectional channel and proposing possible directions to implement uplink channels in the literature. Nevertheless, there is no currently published work reporting an experimental validation of such concepts. In this paper, a general framework to emulate bidirectional channels for time division duplexing (TDD) and frequency division duplexing (FDD) communication systems is proposed. The proposed technique works for MPAC setups with arbitrary uplink and downlink probe configurations, that is, possibly different probe configurations (e.g., number of probes or their configurations) in the uplink and downlink. The simulation results are further supported by measurements in a practical MPAC setup. The proposed algorithm is shown to be a valid method to emulate bidirectional spatial channel models.