Anders Karstensen

A Step Toward 5G in 2020: Low-cost OTA performance evaluation of massive MIMO base stations.

Massive multiple-input, multiple-output (MIMO) is seen as an enabling technology to fulfill dramatic improvements in spectral efficiency for fifth-generation (5G) deployment in 2020. For massive MIMO systems, the learning loop from early-stage prototype design to final-stage performance validation is expected to be slow and ineffective. There is a strong need to evaluate massive MIMO base station (BS) performance with over-the-air (OTA) methods. Until now, such OTA solutions have not been discussed for massive MIMO BS systems.

A 5G hybrid channel model considering rays and geometric stochastic propagation graph

We consider a ray-tracing tool, in particular the METIS map based model for deterministic simulation of the channel impulse response. The ray-tracing tool is extended by adding a geometric stochastic propagation graph to model additional stochastic paths and the dense multipath components observed in measurements. The computational complexity of ray-tracing typically prohibits the inclusion of the dense multipath component or limits it to the early part of the impulse response. Due to computational reasons and for lack of detailed information is the description of the environment for ray-tracing often very simplistic, e.g. plain walls and thus neglecting the structures on the building facades, window frames, window sills, etc. Thus in measurements there are often additional components observed that are not captured by these simplistic ray-tracing implementations. In this contribution we introduce a flexible concept of a hybrid model that allows to simulate computationally efficient deterministic paths and the dense multipath components in a spatially consistent way.

Analysis of Simulated and Measured Indoor Channels for mm-Wave Beamforming Applications

Ray tracing- (RT-) assisted beamforming, where beams are directly steered to dominant paths tracked by ray tracing simulations, is a promising beamforming strategy, since it avoids the time-consuming exhaustive beam searching adopted in conventional beam steering strategies. The performance of RT-assisted beamforming depends directly on how accurate the spatial profiles of the radio environment can be predicted by the RT simulation. In this paper, we investigate how ray tracing-assisted beamforming performs in both poorly furnished and richly furnished indoor environments. Single-user beamforming performance was investigated using both single beam and multiple beams, with two different power allocation schemes applied to multibeamforming. Channel measurements were performed at 28–30 GHz using a vector network analyzer equipped with a biconical antenna as the transmit antenna and a rotated horn antenna as the receive antenna. 3D ray tracing simulations were carried out in the same replicated propagation environments. Based on measurement and ray tracing simulation data, it is shown that RT-assisted beamforming performs well both for single and multibeamforming in these two representative indoor propagation environments.

Over the Air Evaluation of Mobile Phone Antenna Performance for Voice over LTE

This article compares the over-the-air (OTA) performance of tradit ional voice service and voice-over LTE (VoLTE). We present the results of the OTA measurements of the antenna performance of 22 mobile phones commonly used over the last two years. VoLTE is a feature included in LTE that allows voice service to be delivered as data flows. Traditional studies on LTE include only data service and, therefore, OTA for data service, which is measured with the phone held in the browsing position only by the hand, whereas VoLTE uses the same data channel but with the device held next to the head by a hand. Traditional studies on voice service include only OTA in voice service. The figures of merit (FoMs) taken into account for ranking the devices were the total radiated power (TRP) and the total isotropic sensitivity (TIS), which are related to the transmitter and receiver antenna performance, respectively. Our investigation includes results for talk mode using left- and right-hand phantoms next to the head to calculate the maximum power radiated by the transmitter. To evaluate the sensitivity of the receiver, we considered the performance in talk mode using a right-hand phantom next to the head as well as in data mode using only the hand phantom.