Males of the Japanese tree frog have learned not to use their calls at
the same time so that the females can distinguish between them. Scientists at
the Polytechnic University of Catalonia have used this form of calling behavior
to create an algorithm that assigns colors to network nodes—an operation that
can be applied to developing efficient wireless networks.
How can network nodes be colored with the least possible
number of colors without two consecutive nodes being the same color? A team of
researchers at the Polytechnic University of Catalonia have found a solution to
this mathematical problem with the help of some rather special colleagues:
Japanese tree frogs (Hyla japonica).
These male amphibians use their calls to attract the female,
who can recognize where it comes from and then locate the suitor. The problem
arises when two males are too close to one another and they use their call at
the same time. The females become confused and are unable to determine the
location of the call. Therefore, the males have had to learn how to ‘desynchronize’
their calls or, in other words, not call at the same time in order for a
distinction to be made.
“Since there is no system of central control organizing
this “desynchronization”, the mechanism may be considered as an
example of natural self-organization,” explains Christian Blum. With the
help of his colleague Hugo Hernández, such behavior provided inspiration for
“solving the so-called ‘graph coloring problem’ in an even and distributed
A graph is a set of connected nodes. As in the case of the frog’s
‘desynchronized calls’, operating in a ‘distributed’ fashion implies that there
is no other way of central control that helps to solve the problem with a
global vision and all the information on the situation.
In the same way, the researchers have devised a new algorithm
for assigning colors to network nodes ensuring that each pair of connected
nodes is not the same color. The end goal is to generate a valid solution that
uses the least amount of colors.
Application to WiFi connections
As Blum outlines, “this type of graph coloring is the formalization of
a problem that arises in many areas of the real world, such as the optimization
of modern wireless networks with no predetermined structure using techniques
for reducing losses in information packages and energy efficiency
This study falls under the field of ‘swarm intelligence’, a
branch of artificial intelligence that aims to design intelligent systems with
multiple agents. This is inspired by the collective behavior of animal
societies such as ant colonies, flocks of birds, shoals of fish and frogs, as
in this case.