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Multihop multi-channel scheduling for wireless control in WirelessHART networks

The WirelessHART standard uses TDMA and channel hopping to control access to the network and to coordinate communication between network devices, in order to enhance reliability and to improve the throughput of the network. A problem in utilizing multiple channels is that current devices are usually equipped with a single transceiver. Thus, a node can only transmit or receive on one channel at a time. Moreover, contrary to todays wired control systems, if a single access point is used the communication becomes the bottle neck of the control system. Therefore this paper presents how one may schedule the WirelessHART communication using two access points. Furthermore the paper describes a scheduling algorithm managing a multihop multi-channel networked control system based on the WirelessHART standard. A simulation example of a multihop multi-channel network is also shown, using the fixed packet lost utility of the Matlab/Simulink-based tool TrueTime.

An analytical model of the effective delay performance for Bluetooth low energy

With the uprising trend of the integration of wireless sensing systems in fields such as health care and industrial processes, where information exchange between power-limited devices is required, lower energy consumption and Quality of Service demands are becoming more stringent. Bluetooth Low Energy is a promising technology that provides, besides ultra-low energy properties, compatibility with most mobile units. However, apart from power efficiency, opportune and reliable information delivery is mandatory in time-critical applications. In this paper we propose an analytical model of the delay performance of Bluetooth Low Energy for connection-oriented applications under different bit error conditions. In addition to the physical over-the-air latency, we also analyze the effect of the occurrence time of an Application Layer event on the effective transmission delay. We highlight the impact of the devices processing speed and the timing configuration of the connection on the final measured latency. Simulation results validate the accuracy of the model for all the analyzed cases.