Physical-layer security metric for user association in ultra-dense networks

Network densification in future fifth generation wireless networks is considered a key technology to fulfill the challenging requirements in terms of requested capacity. In addition, the ultra dense network (UDN) can be a useful mean to increase the security in the wireless link, where a huge amount of sensitive and confidential data will be transmitted. In particular, the dense network deployment offers new opportunities for achieving security at physical layer because wireless channels are more random and the inter-cell interference can be beneficial. In this context, where each user equipment is under the coverage of several cells, the user association policy can be suitably designed to increase the physical-layer security. This paper investigates a new metric for the security-based user association in UDNs. In particular, since the position of the eavesdropper is typically not known, a measure of the secure area is introduced, and then a new association policy based on this metric is proposed and its performance is compared with that of the classical best qualitychannel association. Numerical results show that this approach significantly outperforms the traditional one.