Correction of Channel Sounding Clock Drift and Antenna Rotation Effects for mmWave Angular Profile Measurements

Abstract

Millimeter-wave (mmWave) bands will be used for the fifth generation communication systems to support high data rates. For the proper characterization of the mmWave propagation channel, it is essential to measure the power angulardelay profile (PADP) of the channel which includes angle-ofdeparture (AoD) and angle-of-arrival (AoA) of the multipath components (MPCs). In this paper, we first describe in detail our 28 GHz channel sounder where directional horn antennas are placed on rotating gimbals. Then, for this specific sounder class, we describe and address the following two problems in extracting the MPCs from the measurements: 1) For the channel measurements at large distances between the transmitter (TX) and the receiver (RX), it is not possible to generate the triggering signal for the TX and the RX using a single clock (SICL). This necessitates the use of separate clocks (SECLs) which introduces a random timing drift between the clocks. 2) As the positions of the antennas change during the scanning process, total distance traveled by the same MPC differs at each measurement. These two errors together cause missing some of the MPCs and detecting MPCs that do not exist in reality. We propose an algorithm to correct the clock drift and the errors in the MPC delays due to the rotation of the antennas. We compare the MPCs from the SICL measurement and the corrected SECL measurements using a Hungarian algorithm based MPC matching method. We show that the percentage of the matched MPCs increases from 28.36% to 74.13% after the correction process.Index Terms-28 GHz, channel sounding, clock drift, Hungarian algorithm, millimeter-wave (mmWave), multipath component (MPC).

28 GHz mmWave Channel Measurements and Modeling in a Library Environment

“…As the horn antennas are rotated during a measurement, the total distance travelled by a multipath component (MPC) changes, which may result in detecting ghost MPCs or missing some actual MPCs. These effects in the delays of the peaks detected from the PDPs are corrected using the algorithm described in [12]. Next, the MPCs are extracted using the peak search algorithm [12].…”

“…These effects in the delays of the peaks detected from the PDPs are corrected using the algorithm described in [12]. Next, the MPCs are extracted using the peak search algorithm [12]. The PADP of the channel, where the AoAs and the AoDs of the MPCs over all possible TX/RX angles are estimated as well, can be expressed as: ] T is the two-dimensional AoA of the same MPC at the RX, α n is the path gain, τ n is the delay of the nth MPC, and N is the total number of MPCs considering all possible TX/RX directions.…”

EMR: A New Metric to Assess the Resilience of Directional mmWave Channels to Blockages

“…However, since the angle of arrival/departure (AoA/AoD) information of the multipath components (MPCs) are of critical importance at high frequencies (i.e., due to beamforming), power angular-delay profiles (PADPs) of the channel should be extracted at these frequency bands. The PADP can be expressed as [5]:…”

“…where N is the number of MPCs, α n is the path gain, θ AoD are the two-dimensional AoD and AoA of the n-th MPC in the azimuth and elevation planes, respectively, and τ n is the delay of the n-th MPC. These parameters can be obtained from channel measurements using appropriate channel sounders or estimated from ray tracing simulations along with accompanying MPC extraction algorithms (e.g., peak search algorithm [5], or super-resolution techniques [6], [7]). The relationship between the received power over each path and the corresponding path gain can be written using the link budget as…”

“…Library measurements include 11 LOS and 8 NLOS scenarios for TX-RX separation distances ranging from 10 m to 50 m. Other details about the measurements and the measurement environment can be found in [16]. For the extraction of the MPCs, we used the peak searching algorithm in [5]. We start with the LOS measurements.…”