Massive MIMO real-time channel measurements and theoretic TDD downlink throughput predictions

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Abstract-This paper is the first to evaluate the realistic performance of Massive MIMO using real-time channel measurements conducted at 3.51GHz. Our testbed consists of 64 National Instruments Universal Software Radio Peripheral Reconfigurable Input and Output (NI USRP RIO) software defined radios (SDRs) with 128 dipole antennas at the Base Station (BS) side, and 6 USRPs configured as 12 single-antenna User Equipment (UE) nodes. The system operates in a Time Division Duplex (TDD) fashion with a Long Term Evolution (LTE) like Physical Layer framework which, when fully deployed, will enable instantaneous throughput measurements on the Uplink (UL) and Downlink (DL) according to a userdefined frame schedule. In this paper we present real-time UL channel measurements at all BS antenna ports simultaneously, which allows the temporal characteristics of the Massive MIMO channel to be recorded. Eigen-beamforming precoding and a Received Bit-level Mutual Information Rate (RBIR) abstraction simulator are then used to predict the theoretic DL performance. We quantify the co-located Massive MIMO throughput for differing numbers of BS antennas (i.e. 32, 64 and 112 elements) and UE locations for an indoor environment.

User Localization Using Random Access Channel Signals in LTE Networks with Massive MIMO

“…Since the number of unknown parameters is four (x, y, z, R), the coordinates of the UE can be calculated if there are no less than 4 antenna elements, which is not a problem for BS with Massive MIMO [2], [4]. Once the BS has enough antenna elements, the above formulated localization problem transforms to the classical GNSS positioning problem that can be solved using the Bancroft's algorithm, which has a closedform solution [13].…”

“…1 compares the SWP model with the conventional Plane Wave Propagation (PWP) model. Experiments conducted at the Universities of Bristol and Lund using massive MIMO prototypes have confirmed the necessity to use spherical propagation in the massive MIMO procedures [2], [4]. In this work we propose SWP-based solutions that use the Randon Access Channel (RACH) signals in Long Term Evolution (LTE) networks to locate UEs.…”

“…Beamforming allows the creation of focused beams towards User Equipments (UEs), by which energy consumption and interference can be significantly reduced and radio resources can be reused to increase capacity [1]- [4]. In most existing beamforming schemes, beams are created based on the estimation of the Downlink (DL) channels via reference signals, which brings large overhead to DL data communications.…”

Precoding for TDD and FDD in Measured Massive MIMO Channels

“…Accurate evaluation of MMIMO systems needs to be carried out using real channels, since MMIMO may exploit channel features that are not included in current channel models. Several testbeds have been implemented such as the TDD system described in [6] operating at 2.6 GHz, or the TDD system at 3.5 GHz described in, e.g., [7]- [9]. Another example of a TDD testbed is used in these works [10], [11].…”