Supporting Real-Time Asynchronous Communication within Bluetooth Ad Hoc Networks

The Bluetooth protocols have been developed to support wireless transmission within personal area networks; primarily serving as a cable replacement technology for mobile devices. The standard protocol provides support for synchronous transmission of audio and asynchronous transmission of data. In general, the standard was developed to use synchronous connection-oriented (SCO) channels to transmit real-time audio communication and asynchronous connectionless (ACL) channels to transmit non-real-time data communication. No preexisting support exists for the transmission of real-time, asynchronous data communication. Real-time systems that require asynchronous communication are characterized by the need to share data, alarm and event information between various sensors and processing units with the expectation that information is communicated within well-defined temporal constraints. In such an environment, both measurement and control can be achieved. Unfortunately, the current Bluetooth specification provides no guarantees for timely delivery of asynchronous data transfers. However, the Bluetooth communication protocols are based on time-division multiplexing with all communication coordinated through a master radio. As such, the Bluetooth protocols are somewhat characteristic of token bus networks. Token bus networks have been well suited for many real-time distributed systems. Thus, there is the implication that Bluetooth should be capable of supporting asynchronous real-time communication. This paper introduces research to model and adapt the Bluetooth technology so that it can provide for the deterministic transmission of real-time, asynchronous data within a Bluetooth piconet; hence supporting the transmission of real-time data within low-power, limited-range distributed systems. This approach is well suited to the transmission of real-time sensor data within various mobile and portable control systems. The paper documents the motivation, preliminary analysis, and initial results of an on-going research project supporting the viability of the use of Bluetooth within “hard” real-time and “soft” real-time control systems.