Publications

Björn Andersson, Eduardo Tovar and Nuno Pereira
Proceedings of the 26th IEEE International Real-Time Systems Symposium (RTSS'05), pp. 15-24
December 2005

We propose a schedulability analysis for a particular class of time division multiple access (TDMA) networks, which we label as TDMA/SS. SS stands for slot skipping, reflecting the fact that a slot is skipped whenever it is not used. Hence, the next slot can start earlier in benefit of hard real-time traffic. In the proposed schedulability analysis, we assume knowledge of all message streams in the system, and that each node schedules messages in its output queue according to a rate monotonic policy (as an example). We present the analysis in two steps. Firstly, we address the case where a node is only permitted to transmit a maximum of one message per TDMA cycle. Secondly, we generalise the analysis to the case where a node is assigned a budget of messages per TDMA cycle it may transmit. A simple algorithm to assign budgets to nodes is also presented.

Björn Andersson, Eduardo Tovar and Nuno Pereira
Technical Report; HURRAY-TR-050501
May 2005 [pdf]

Distributed real-time systems in all their forms, for example in-vehicle electronics, factory-floor controls or wireless sensor systems, need to communicate with bounded delays. TDMA (time division multiple access) protocols solve this by assigning messages to time slots such that no two nodes transmit at the same time and queuing delays of messages are bounded.
We propose a schedulability analysis for a particular class of TDMA networks, which we label as TDMA/SS. SS stands for slot skipping and reflects the fact that a slot is skipped whenever it is not used. Hence, the next slot can start earlier and this reclaims time for hard real-time traffic. In the proposed schedulability analysis, we assume that (i) the message streams on each node are known and (ii) each node schedules messages in their output queue; this is exemplified by using RM (rate-monotonic). We present the analysis in two steps. First we address the case where a node is only permitted to transmit a maximum of one message per TDMA cycle. Then, we generalize the analysis to the case where a node is assigned a budget of messages per TDMA cycle it may transmit. A simple algorithm to assign budgets to nodes is also presented.