Wireless synchronization of onboard computing devices through WiFi

DOI: 10.34759/trd-2019-108-13

Аuthors

Romanov A. M.^1*, Gringoli F. ^2**, Sikora A. ^3***

1. MIREA — Russian Technological University (Lomonosov Institute of Fine Chemical Technologies), 78, Vernadsky prospect, Moscow, 119454, Russia
2. Università degli Studi di Brescia, Piazzale Spedali Civili 1, Brescia, 25123, Italy
3. Offenburg University of Applied Sciences, Badstrasse 24, Offenburg, 77652, Germany

*e-mail: romanov@mirea.ru
**e-mail: francesco.gringoli@unibs.it
***e-mail: axel.sikora@hs-offenburg.de

Abstract

This article deals with the problem of wireless synchronization between onboard computing devices of small-sized unmanned aerial vehicles (SUAV) equipped with integrated wireless chips (IWC). Accurate synchronization between several devices requires the precise timestamping of batches transmitting and receiving on each of them. The best precision is demonstrated by those solutions where timestamping is performed on the PHY level, right after modulation/demodulation of the batch. Nowadays, most of the currently produced IWC are Systems-on-a-Chip (SoC) that include both PHY and MAC, implemented with one or several processor cores application. SoC allows create more cost and energy efficient wireless devices. At the same time, it limits the developers direct access to the internal signals and significantly complicates precise timestamping for sent and received batches, required for mutual synchronization of industrial devices. Some modern IEEE 802.11 IWCs have inbuilt functions that use internal chip clock to register timestamps. However, high jitter of the interfaces between the external device and IWC degrades the comparison of the timestamps from the internal clock to those registered by external devices. To solve this problem, the article proposes a novel approach to the synchronization, based on the analysis of IWC receiver input potential. The benefit of this approach is that there is no need to demodulate and decode the received batches, thus allowing it implementation with low-cost IWCs. In this araticle, Cypress CYW43438 was taken as an example for designing hardware and software solutions for synchronization between two SUAV onboard computing devices, equipped with IWC. The results of the performed experimental studies reveal that mutual synchronization error of the proposed method does not exceed 10 μs.

Keywords:

wireless synchronization, WiFi, jitter, small-sized unmanned aerial vehicles, field-programmable gate array

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