ABSTRACT:
In distributed embedded real-time system, Time Division Multiple
Access (TDMA) is a widely used protocol in which each node involved in
network accesses the medium in a time-triggered way. Therefore, a
reliable clock synchronization is necessary in the communication
layer. Maintenance of global time needs extra overhead, on the other
hand, and wastes bandwidth due to preserving precise time window in
TDMA. To relieve this issue in TDMA, we propose a new protocol-Node
Order Protocol (NOP), which make nodes access shared medium by
specified ordering to resolve contention. At the same time,
communication protocol changes to event-driven way and not
time-triggered, which will eliminate need for global time at protocol
layer and further saturate the network bandwidth. In this paper, we
first introduce design priciple of NOP protocol, including semantic of
NOP protocol, error dectection and fault handling mechanism. Moreover
to improve the availability of the NOP protocol, we also provide
simple error recovery mechanism. Especially, we reconsider solution to
alarm shower phenomenon in coupled network and make an attempt to use
a more reliable method. The implementation of NOP protocol is
described in detail. At last, we will do several experiments to
evaluate the performance and the Qos of NOP protocol.