Sequential Routing Decision with Low-Complexity for Throughput Improvement in Full-duplex Cognitive Radio Networks

Routing in Cognitive Radio Networks (CRNs) has recently become more efficient, due to employing the Full-Duplex (FD) transmission technology. When the unlicensed users, also known as Secondary Users (SUs), have FD capabilities, they can transmit and receive simultaneously either over the same channel, namely in-band FD (IB-FD), or over different channels, namely Out-of-Band FD (OB-FD). In this work, we adopt the OB-FD transmission, because it is less complex than IBFD, i.e.; it does not require Self-Interference-Cancellation (SIC) technique, also the hardware cost of devices that support IB-FD capability is more expensive. Apparently, channels assignment for the discovered route is crucial, whether it satisfies the FD transmission condition or not. For the OB-FD transmission, for every segment of three-consecutive hops along the route, their selected three channels must be different in order to avoid interference between SUs. Therefore, in this work, we are motivated to propose a sequential mechanism with low-complexity that is aware about FD when assigning channels, namely Sequential FD-(SFD)-aware. According to the proposed protocol, for each candidate route, channels are assigned to route hops sequentially such that the aforementioned condition is satisfied. However, if this condition is not satisfied, the route will not be adopted. It is worth mentioning that there are some methods studied recently in literature for channels assignments, however, these methods require optimization techniques that have NP-hard complexity in terms of number of hops and channels. We compared our proposed protocol with an existing protocol which assigns for each hop the available channel with maximum rate, and then selects the route that has the maximum bottleneck rate. The simulation results show that our proposed mechanism outperforms the baseline protocol in terms of achieved end-to-end throughput.