  Wireless Sensor Networks (WSNs) are being deployed for different
applications, each having its own structure, goals and requirements. Medium
access control (MAC) protocols play a significant role in WSNs and hence should
be tuned to the applications. However, there is no for selecting MAC protocols
for different situations. Therefore, it is hard to decide which MAC protocol is
good for a given situation. Having a precise model for each MAC protocol, on
the other hand, is almost impossible. Using the intuition that the protocols in
the same behavioral category perform similarly, our goal in this paper is to
introduce a general model that selects the protocol(s) that satisfy the given
requirements from the category that performs better for a given context. We
define the Combined Performance Function (CPF) to demonstrate the performance
of different categories protocols for different contexts. Having the general
model, we then discuss the model scalability for adding new protocols,
categories, requirements, and performance criteria. Considering energy
consumption and delay as the initial performance criteria of the model, we
focus on deriving mathematical models for them. The results extracted from CPF
are the same as the well-known rule of thumb for the MAC protocols that
verifies our model. We validate our models with the help of simulation study.
We also implemented the current CPF model in a web page to make the model
online and useful.
