New operating modes for Bluetooth networks in distributed process control systems

Communication Techniques and Architectures for Bluetooth Networks in Industrial Scenarios

“…On the contrary, the approach proposed in [8], adopted here to support some of the scenarios and architectures dealt with in this paper, allows Slaves to communicate with any member of a group of Slaves. This feature makes the proposed An issue which could arise refers to how to implement S/S communication.…”

“…No significant modifications to the standard should be required and changes should as far as possible, be confined to the software. These two goals are addressed by the approach proposed in [8], where S/S transmission takes place by means of scheduling handled by the Master, which has previously to configure a group of Slaves as belonging to a certain logical ring. The Master specifies the order of the various Slaves in the Ring via a Broadcast message and then transfers to these stations the right to transmit in sequential order, specifying the starting slot and the number of times the sequence is to be repeated.…”

“…As can be seen, it is possible to generate long S/S transmission sequences without loss of synchronization with the Master. For further details, the reader is referred to [8].When the time allocated to the logical ring expires, the last Slave realigns with the Master hopping frequency. From the next slot onwards, the original piconet, comprising all the Slaves, is thus restored and the Master can resume transmitting to all of them in the M/S mode, according to the scheduling algorithm being used.…”

“…As the broadcast message already provides in the N_SLOT field the number of times (in slots) the S/S sequence has to be repeated before slaves in the logical ring resume the M/S mode, a new broadcast message has to be sent only when either the Master has to change (or quit) the logical ring due to specific application requirements (this may seldom occur) or before M/S synchronization is lost. As we calculated in [8], it is possible to generate long S/S transmission sequences before synchronization is lost (about 800 slots). In both cases, the contribution of the second addend in formula (4.4) is negligible.…”

“…In Table 3, the parameters of the Master broadcast message are also shown. In the S/S mode, the value of 100 chosen for M B (the interrrival time of the broadcast message) is just an example of a possible one, and is well lower than the threshold beyond which M/S synchronization is lost (about 800 slots) [8]. A higher M B value would improve schedulability even further, thus allowing the addition of new periodic variables in the piconet.…”