The presence of the spots makes the difference in EDCA from “ordinary” cellular automata. They are thought to introduce a kind of inverse feedback on the cellular automaton in order to stabilize its performance. The spot is a dynamical entity, as it spreads its influence on the cellular space at every step.

Spots act independently, as they don´t have any interaction each with other when they are expanding. A spot deals with other spots, only when they compete for “catching” a cell. Resulting conflict is solved by the Energy Incidence Criterion.

Spot expansion is dictated by its own function, called Expansion Rule, which also can be expressed using a cellular automaton rule. This peculiarity gives the possibility of regarding EDCA as a CA composition, conformed by a “ground” CA and a set of K energy spots automata.

The expansion of spots and their interaction with cells is exposed on the given animation of a running EDCA model.  The 2d binary special case of the CA is used, where cells can have values 1-“alive”,0-“dead”, and the cell space is a bi-dimensional matrix.

Rule used corresponds to the Conway´s “Game of Life” , that is, at every step a living cell remains alive only when surrounded by 2 or 3 living neighbors, otherwise it dies of solitude or overpopulation. A dead cell comes to life when it has exactly 3 living neighbors

Spots are presented as growing rectangles, with origin at changing cells. Green rectangles are positive spots, while red ones correspond to negative spots. Red line at the beginning means a negative spot coming from a far location. Animation shows how the rule acts only when the spot reaches the cell. Otherwise, the cell remains unchanged, in spite of being enabled by the rule.  It is also appreciated how the spot changes its sign and restarts from a new origin after the cell´s transition.

Why energy?

A fixed number of K spots is established at CA initial configuration. This number remains constant at every EDCA step, although spots can change the sign due to interactions with cells. As a conserved quantity, K can be regarded as the total energy of the EDCA system, and each spot as a unit of energy. More formal explanation of EDCA conserved quantities can be found here: Conservation laws