AwareCon, the customized network protocol for the Particles provides an ad hoc and synchronized data transmission up to 48kBit. Particles find their communication partner very quick and stay synchronized to them as long they are in range. The protocol consists of 3 Layers:
The protocol is a strict time synchronizes TDMA system with a frame duration of 13 ms. The data traffic is organized in packets of a maximum of 64 Bytes payload. Every slot contains only one packet. As the processor is single task, the time frame of the protocol guarantees some time left in each slot for applications on the processor. That time is showed black in the figure. The channel access control avoids collisions and therefore the full throughput can be achieved even with hundreds of particles running.
The payload data is organized in units which we call tuples. Those tuples consist of 2 byte data type, one byte length and n byte data. The two byte data type descriptor can be interpreted to 3 characters. A software tool (3_2coding.exe) under windows can do this.
These tuples are concatenated and placed in the payload buffer of the ACL in a packet. The first type in a packet has a special meaning. It declares the subject of the packet. Every packet has to carry a subject. It explains the originator of the packet. A packet would look e.g. like this:
AMC, STE, 37: “Artefact Mediacup, Sensor Temperature, 37 degree centigrade”
The transmission in the Particle network is based on a broadcast/subscribe mechanism. Every packet that is sent out is broadcasted in the radio cell and has no target address. All active receivers in range are receiving all packets and sort those out, in which they are not interested. The declaration of interest is managed through a local subscription list that is held in every network instance (in every particle computer device). The subscription list is a list of subjects in which the mobile device is interested. The subscriptions are only local and not transmitted to remote communication partners. The list is limited to 7 subjects (Particle AwareCon version 5)The incoming broadcast messages are then filtered. The packets containing subjects of the subscription list are processed and received. All others are discarded and no reception is indicated to program level. See function reference “subscriptions” for the necessary functions.
THE AWARECON FUNCTIONS REFERENCE
THE AWARECON ACKKNOWLEDGED TRAFFIC