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.

Current Wireless Sensor Networks (WSNs) are deployed over unlicensed frequency bands that face an increased level of interference from various wireless systems. Cognitive Radio Sensor Networks (CRSNs) overcome this problem by allowing sensor nodes to access new spectrum bands to minimize interferences. In this paper, we focus on the MultiChannel Time Slot Assignment problem (MC-TSA) in CRSN. Each sensor node is assigned the number of time slots it needs to transfer its own data as well as the data received from its children in the rooting tree rooted at the sink without interfering with other secondary users. Besides, sensor nodes cannot transmit on a channel occupied by a primary user. Our objective is to increase the network throughput offered to sensor nodes. We start by formulating the MC-TSA problem as an Integer Linear Program where the goal is to minimize the number of slots in the schedule.We then propose an Opportunistic centralized TIme slot assignment in COgnitive Radio sensor networks (OTICOR). We evaluate its performance in terms of number of slots and throughput.

Leader election in Cognitive Radio Networks

Participants : Paul Muhlethaler, Dimitrios Milioris.

This is a joint work with Philippe Jacquet from Alcatel-Lucent Bell Labs.

In this sudy we have introduced a new algorithm (green election) to achieve a dis- tributed leader election in a broadcast channel that is more efficient than the classic Part-and-Try algorithm. The algorithm has the adavantage of having a reduced overhead $log\left(log\right(N\left)\right)$ rather than $log\left(N\right)$. More importantly the algorithm has the a greatly reduced energy consumption since it requires $O\left(N^{1/k}\right)$ burst transmissions instead of $O(N/k)$, per election, $k$ being a parameter depending on the physical properties of the medium of communication.

One of the applications of green election is for wireless col- lision algorithms in particular in cognitive wireless networks where the secondary network is WiFi IEEE 802.11. Since the green election is low energy consuming, it can be used as a systematic and repetitive medium access control that will naturally prevail over the WiFi CSMA scheme.