Bluetooth is an omnipresent technology, available on billions of devices today. While it has been traditionally limited to peer-to-peer communication and star networks, the recent Bluetooth Mesh standard extends it to multi-hop networking. In addition, the Bluetooth 5 standard introduces new modes to allow for increased reliability. In this article, we evaluate the feasibility of concurrent transmissions (CT) in Bluetooth via modeling and controlled experiments and then devise an efficient network-wide data dissemination protocol, BlueFlood, based on CT for multi-hop Bluetooth networks. First, we model and analyze how CT distorts the received waveform and characterize the Bit Error Rate of a Frequency-Shift Keying receiver to show that CT is feasible over Bluetooth. Second, we verify our analytic results with a controlled experimental study of CT over Bluetooth PHY. Third, we present BlueFlood, a fast and efficient network-wide data dissemination in multi-hop Bluetooth networks. In our experimental evaluation, in two testbeds deployed in university buildings, we show that BlueFlood achieves 99.9% end-to-end delivery ratio with a duty-cycle of 0.4% for periodic dissemination of advertising packets of 38 bytes with 200 milliseconds intervals at 2 Mbps. Moreover, we show that BlueFlood can be received by off-the-shelf devices such as smartphones, paving a seamless integration with existing technologies.

In the Industrial Internet of Things (i.e., IIoT), the standardization of open technologies and protocols has achieved seamless data exchange between machines and other physical systems from different manufacturers. At the MAC sublayer, the industry-standard protocols IEEE 802.15.4 Time Slot Channel Hopping (TSCH) and Deterministic and Synchronous Multi-channel Extension (DSME) show promising properties for high adaptability and dynamically changing traffic. However, performance comparison between these MAC protocols rarely has gone beyond a simulation phase. This work presents the results of such a comparison on physically deployed networks using the facilities of the FIT-IoTLab. The evaluation includes fully implementing an IIoT protocol stack based on MQTT in Contiki-NG. It comprises the integration of DSME as part of Contiki-NG's software stack through OpenDSME, the only publicly available implementation of DSME. Results show that both protocols suit IIoT applications, particularly for data collection. The comparison between TSCH and DSME also includes an evaluation of distributed schedulers for both MAC modes and one autonomous scheduler for TSCH within a UDP protocol stack.

Structural health monitoring and predictive maintenance promise to significantly reduce costs, increase availability, and improve safety of civil infrastructure and industrial facilities. Wireless and batteryless sensors fuel these applications with the required data. As metal structures often shield sensor nodes from electromagnetic waves, acoustic power and data transfer are promising alternatives. However, the metal channel suffers from severe multipath propagation, limiting data rates to typically less than 200 bits-1. We investigate wideband pulses as alternative to commonly used continuous wave modulation schemes to increase robustness. In a simulation study, we first compare wideband modulation with narrowband modulation schemes and assess their robustness against noise and clock deviations. We then construct a wirelessly powered tag prototype to validate the simulation results in real-world metal channels. Furthermore, we propose a reader-based synchronization scheme to mitigate clock mismatch, which is inevitable with ultra-low-power tags. The results show that wideband pulse-position modulation is the most favorable modulation scheme, increasing the median data rates in many scenarios by 132% over continuous-wave schemes. Additionally, wideband pulses are advantageous for power transfer in the highly frequency-selective channel when optimal carrier frequencies are yet unknown. However, simultaneous power transfer and communication on the same transducer are shown to interfere with each other, complicating the receiver design.