Modeling RF-based sensor networks by using dual-source retrial queueing systems

Here, we would like to study the efficiency and utilization of radio frequency (RF) transmission in wireless sensor networks. A new dual source queueing model (with finite and infinite numbers of sensors) is introduced in order to obtain the most frequently studied system performance characteristics (e.g. mean response time, average number of jobs waiting for transmission, and the utilization of the RF unit). The different types of sensors form the “sources” and the RF unit forms the “central servicing node” of this model. The elements of the sensor fields are classified according to their working purposes: The first class is the “Emergency” or “Special” class which is responsible to notify special rare events (e.g. fire alarms). The other class is the “Standard” class where sensors measure data from standard conventional events or occurrences (eg. motion detection, wind speed, level of darkness etc). For energy efficiency reasons the Central Unit (or Radio Frequency Unit - RFU) might switch into a reduced functioning mode. This reduced communication mode is for saving energy. The transmissions are closed in this mode. Returning from the reduced mode two cases are considered and two models are created to compare their steady-state system performance characteristics: In the first model, the RF transmission is available randomly to the sensor nodes (“Non-Controlled” case). In the other case, the Central Unit jobs which come from the Special class, can use the wireless service immediately (“Controlled” case).