Optimizing Connection Establishment and Parameter Adaptation in Bluetooth Low-Energy for Intermittently-powered Devices

Abstract

The growing field of research into batteryless or intermittent systems has enabled Internet of Things applications that were previously impossible. For example, the FreeBie system recently introduced Bluetooth Low-Energy (BLE)
to intermittent devices, making medium to long range bi-directional communication a reality for the first time. However, this achievement also highlighted
that some inefficiencies considered acceptable for conventional systems are unacceptable when working in the intermittent domain. Our key insights are that
intermittent peripherals should dictate the connection parameters and not the
central, that connection setup overhead should be reduced as much as possible,
and that connection parameter updates should be applied faster. To achieve
these goals, we 1) introduce a method of sharing connection parameters before
a connection is made, 2) introduce methods of caching connection setup packets
together with a reconnect procedure called Fast Reconnect that reduces connection setup to a single packet, and 3) apply 1 and 2 in a dynamic algorithm
called FRAPPUCcInO that controls connection rate based on energy harvesting capabilities. These three solutions allow intermittent BLE to be used in
environments with less ambiently available energy than before by improving
efficiency and responsiveness.