2.2.2.2. Transceiver logical block¶
The transceiver is responsible to broadcast data packets handled by the transcoder to the neighbourhood in the most convenient way. It relies on a datalink protocol which is used to take into account the properties of the underlying plugin interface.
2.2.2.2.1. Winenet datalink protocol¶
Winenet is the datalink protocol used with WLan (Wifi) transmission. Its main purpose is to allow smart objects to send their MEs without interfering with each other. In this perspective, Winenet gives the hand to each smart object one after the other after transmitting a certain number of packets contained in a frame. Each frame is sent to each smart object giving the impression that packets are broadcast. We called this approach Unibroad (combining Unicast and broadcast).
Compared to another datalink protocol based on routing mechanisms, Winenet is much simpler since it is based on the neighbourhood. Each smart object (SOO) is periodically broadcasting a Discovery beacon and can be recognized by all SOOs which are in the light of sight.
Each SOO has various information related to its state and the neighbourhood:
randnris a random number which is determined during the PING procedure and will be used in case of simultaneous actions with a same beacon. The greater value has the advantage and the SOO with the lower value will abort the transaction.paired speakeris the agencyUID of the SOO which is designated as speaker. The SOO is listening at this specific speaker which transmits MEs.validis set to true during the PING procedure.
2.2.2.2.1.1. Beacons¶
The following beacons are used in Winenet. The beacon has a cause field which may contain some details related to the beacon.
Name |
Definition |
Cause |
|---|---|---|
PING |
Used to consider a neighbour as valid |
REQUEST / RESPONSE |
QUERY |
Used to exchange the SOO internal state |
REQUEST / RESPONSE |
ACKNOWLEDGMENT |
When a beacon or send of frames require an acknowledgment |
OK / TIMEOUT / ABORT |
GO SPEAKER |
When a speaker wants another neighbour to get speaker |
(empty) |
BROADCAST SPEAKER |
Ask the neighbours to get paired with us (before sending frames) If the cause is abort, the SOO gets unpaired. |
(empty) / abort |
Only GO SPEAKER and BROADCAST SPEAKER beacons require an acknowledgment.
There are four main states: INIT, IDLE, SPEAKER and LISTENER.
State INIT is used at the beginning until the Discovery protocol insert the smart object in the neighbourhood.
Note
Each smart object is also considered as neighbour, however it remains with the valid attribute to false.
2.2.2.2.1.2. INIT state¶
Then, the state IDLE is a temporary state until a first neighbour is discovered.
When a neighbour appears, a PING procedure is automatically triggered as follows: the SOO with the lower agencyUID sends
a PING REQUEST to the other. Then, the other SOO will answer with a PING RESPONSE.
Note
Everytime a beacon is sent out to another SOO, its internal state is sent with the beacon. The internal state is made of
the paired speaker and a randnr random number.
2.2.2.2.1.3. LISTENER state¶
The SOO with at least one neighbour is put to the LISTENER state after triggering a QUERY procedure.
A QUERY REQUEST beacon is sent to the first neighbour. The SOO will be able to determine if it has to
switch to the SPEAKER state at the receival of QUERY RESPONSE beacon.
The QUERY procedure is also used as a consolidation mechanism to make sure the speaker is still a true speaker, and if it is not the case to re-activate a speaker in any case.
Depending on the value of paired speaker, the SOO can answer to GO SPEAKER or BROADCAST SPEAKER beacon.
2.2.2.2.1.4. SPEAKER state¶
This state enables the transmission of a pending buffer (typically a ME).
The buffer comes from the transcoder layer which actually splits the buffer in packets. Winenet is buffering
a certain number of packets to have a frame. The frame (with multiple packets) is sent out to each SOO and requires
to be acknowledged.
2.2.2.2.2. Parameters¶
The following constants/values are defined and used by the datalink protocol.