LTE-U based Train to Train Communication System in CBTC: System Desin and Reliability Analysis

Table 1

Graphic elements and their meanings of DSPN.

Element	Symbol	Meaning
Store		The store in the hierarchical model
		The store associated with the previous or next level
Token		Resources in the store and their quantity
Transition		Exponential transition
		Fixed time transition
		Immediate transition
Normal arc		Directed arcs, input and output functions between locations and transitions
Suppression arc		Restrictions on transition, when there are a number of tokens corresponding to the arc weight in the store onnected to the transition use prohibition arc, the transition prohibition triggers
Test arc		Restrictions on the transition, when there are a number of tokens corresponding to the arc weight in the store connected to the transition test arc, the transition is allowed to trigger