There’s new research by Institute of Electronics and Computer Science, Universite Grenoble Alpes, France on Bluetooth Low Energy Throughput in Densely Deployed Radio Environment (PDF). It looks into coexistence issues when Bluetooth is used in a crowded 2.4GHz frequency band where other devices such as Classic Bluetooth, WiFi, Zigbee and microwave ovens might also be operating.
The paper starts with a theoretical discussion of the throughput of Bluetooth LE.
Experiments used ten Bluetooth nodes to measure Bluetooth application throughput using various connection parameters and different interference sources. Two WiFi routers were used to evaluate the impact of WiFi on the BLE throughput.
The researchers found:
The more Bluetooth devices are working simultaneously, the more drastically Bluetooth throughput is decreasing… The Bluetooth co-interference causes throughput decrease for longer connection intervals. This behaviour could be explained by collisions in data transfer channel.
Also:
The effect of WiFi interference does not depend on the BLE connection interval. In this study, WiFi activity reduced BLE throughput approximately by 30% regardless of the connection interval.
These tests used Bluetooth GATT to form connection between devices. Some applications of Bluetooth LE, such as the use of beacons and AoA direction finding, don’t use GATT other than for initial setup. GATT implies connection between devices while beacons and the sole use of advertising and listening, rather than connection, is a different form of communication not covered by this paper. We have a post on Managing Bluetooth LE Advertising Congestion and Fixing Poor Bluetooth Beacon Radio Signals if you wish to explore this topic in more detail.
