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Fairly decent discussion on various binary encoding formats, with or without schemata, and with or without zero-copy
(tags: flatbuffers flexbuffers json encoding data formats file-formats avro protobuf zerocopy sbe schemas)
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Douglas J. Leith, Stephen Farrell School of Computer Science & Statistics, Trinity College Dublin, Ireland 15th June 2020: ‘We report on the results of a measurement study carried out on a commuter bus in Dublin, Ireland using the Google/Apple Exposure Notification (GAEN) API. Measurements were collected between 60 pairs of handset locations and are publicly available. We find that the attenuation level reported by the GAEN API need not increase with distance between handsets, consistent with there being a complex radio environment inside a bus caused by the metal-rich environment. Changing the people holding a pair of handsets, with the location of the handsets otherwise remaining unchanged, can cause variations of ±10dB in the attenuation level reported by the GAEN API. Applying the rule used by the Swiss Covid-19 contact tracing app to trigger an exposure notification to our bus measurements we find that no exposure notifications would have been triggered despite the fact that all pairs of handsets were within 2m of one another for at least 15 minutes. Applying an alternative threshold-based exposure notification rule can somewhat improve performance to a detection rate of 5% when an exposure duration threshold of 15 minutes is used, increasing to 8% when the exposure duration threshold is reduced to 10 minutes. Stratifying the data by distance between pairs of handsets indicates that there is only a weak dependence of detection rate on distance.’
(tags: papers bluetooth contact-tracing exposure-notification covid-19 accuracy testing buses radio gaen mobile)