MIMO Communication Measurements in Small Cell Scenarios at 28 GHz

Abstract

<p>Massive multiple-input multiple-output (MIMO) systems operating in the centimeter-wave (cmWave) and millimeter-wave (mmWave) region offer huge spectral efficiencies, which enable to satisfy the urgent need for higher data rates in mobile communication networks. However, the proper design of those massive MIMO systems first requires a deep understanding of the underlying wireless propagation channel. Therefore, we present a fully-digital MIMO measurement system operating around 28 GHz. The system enables to take fast subsequent snapshots of the complex MIMO channel matrix. Based on this method we statistically analyze the time-dependent channel behavior, the achievable signal quality and spectral efficiency, as well as the channel eigenvalue profile. Furthermore, the presented calibration approach for the receiver enables an estimation of the dominant absolute angle of arrival (AoA) and allows us to draw conclusions about the line-of-sight (LOS) dominance of the scenario. In total, 159 uplink communication measurements over 20 seconds are conducted in three different small cell site scenarios to investigate the wireless propagation behavior. The measurements reveal the existence of several spatial propagation paths between the mobile transmitter and the base station. Furthermore, an insight into their likelihood in different propagation scenarios is also given.</p>

Hybrid Beamforming Analysis Based on MIMO Channel Measurements at 28 GHz

“…The outdoor measurements used are conducted in three small cell site scenarios with in total 159 different Tx locations emulating an uplink communication scenario between a mobile entity as Tx and a radio base station as Rx [11]. The measurements are performed between 4 Tx and 16 Rx antennas at a center frequency of 27.8 GHz.…”

“…For each location a recording of around 20 s is made. A more detailed description of the measurement principle, setup and scenarios can be found in [11].…”

“…This work focuses on analyzing the subarray-based hybrid beamforming architecture (also denominated in literature as sub-connected or partially-connected hybrid beamforming architecture) using outdoor measurements presented by the authors in [11]. Three algorithms for calculating the complex weighting factors of the analog beamforming network are compared, among them a simple algorithm based on the angular information of the spatial propagation paths.…”

Beam Pattern Optimization Method for Subarray-based Hybrid Beamforming Systems

“…The antenna board, designed in a previous study [28], consists of an uniform linear array with N ant = 16 antennas arranged in the horizontal plane. The element spacing is λ 0 /2 ≈ 5.35 mm, where λ 0 represents the wavelengths at 27.8 GHz.…”

Analog 28 GHz LoS MIMO Relay System Using a 90° Hybrid Coupler

“…At the first transmitter and last receiver end software defined radio (SDR) from Ettus Research Inc. of type USRP X310 are utilized, which perform analog-todigital and digital-to-analog conversion as well as baseband to IF up-and down-conversion, amplification and filtering. The radio frequency (RF) front-and backends perform IF to RF conversion as well as amplification and bandpass filtering as presented by the authors in [27]. To avoid frequency offsets between the transmitter and receiver, the local oscillators (LO) for the RF front-and backends and the SDRs are synchronized using a 10 MHz reference signal.…”