Multichannel time slot assignment in Cognitive Radio Sensor Networks

Participants : Ons Mabrouk, Pascale Minet, Ridha Soua, Ichrak Amdouni.

This is a joint work with Hanen Idoudi and Leila Saidane from ENSI, Tunisia.

The unlicensed spectrum bands become overcrowded causing an increased level of interference for current wireless sensor nodes. Cognitive Radio Sensor Networks (CRSNs) overcome this problem by allowing sensor nodes to access opportunistically the underutilized licensed spectrum bands. The sink assigns the spectrum holes to the secondary users (SUs). Therefore, it must rely on reliable information about the spectrum holes to protect the primary users (PUs). In 2013 we focused on the MultiChannel Time Slot Assignment problem (MC-TSA) in CRSN and proposed an Opportunistic centralized TIme slot assignment in COgnitive Radio sensor networks (OTICOR). This latter differs from the existing schemes in its ability to allow non-interfering cognitive sensors to access the same channel and time slot pair. OTICOR takes advantages of spatial reuse, multichannel communication and multiple radio interfaces of the sink. We proved through simulations that a smaller schedule length improves the throughput. Applying OTICOR, we show that, even in the presence of several $PUs$, the average throughput granted to $SUs$ remains important. We also show how to get the best performances of OTICOR when the channel occupancy by $PUs$ is known.

In 2014, we proposed two ways for the sink to determine the available channels and alert the SUs if an unexpected activity of PU occurs. Our objective is to design an algorithm able to detect the unexpected presence of PUs in the multi-hop network while maximizing the throughput. To achieve our goal, we propose an optimized version of our previous scheduling algorithm Opportunistic centralized TIme slot assignment in COgnitive Radio sensor networks (OTICOR). This algorithm takes advantage of the slots dedicated to the control period by allowing noninterfering cognitive sensors to access the control/data channel and time slot pair. We shown through simulations that using the control period for data transmission minimizes the schedule length and maximizes the throughput.