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2.14 Scheduling and Cycle Multiplexing
The scheduling is defined during the network design. By defining static and dynamic slots, a
fixed time frame is provided. This enables the unique assignment of frames to the
corresponding slots in each channel.
The number of slots is constant and cannot be changed after the network design. The
flexibility and the usage of the bandwidth is defined during development.
Table 2.4 Scheduling example [VeSc11]
In Table 2.4, a scheduling for nodes K, L, M, N and O is provided. It is allowed to send
different frames in different cycles for the same slot. This is called Cycle Multiplexing.
For Cycle Multiplexing, the following information is needed:
• Slot-ID in the cycle 0...2047
• Base or Start Cycle 0...63
• Repetition Factor {rep = 2 x with 0 ≤ x ≤ 7}
• Channel {A, B, A&B}
• Name of the node
If we take a look on node M in Table 2.4, we can see that it is assigned slots 2 and 7. In the
static segment, node M uses channel A only. Here, it sends three different frames, e.g. frame
y, which has a base cycle of 2 and a repetition factor of 4. That means, that frame y is sent in
cycle 2 for the first time, and after that every 2+4n (with n = 1..15) cycle.
In the dynamic segment, it is acceptable for different nodes to use the same slot. Further, the
nodes are allowed to send different frames, and different nodes may use the different channels
of a slot. Again, all frames have to provide the information needed for Cycle Multiplexing.
If we take a look at slot 7, we can see that node M shares this slot with nodes L and O. In a
cycle, it is possible to send different frames from different nodes. It is also possible for
Channels A and B to be asynchronous, i.e. for a given point of time, A has a different slot id
than B.
Bäurle 12.10.2012