Enhanced protection of hidden primary users through filtering based on suspect channels classification

Abstract

Cognitive radio (CR) users (i.e., secondary users) are wireless nodes which are allowed to select and access licensed frequency bands, provided that they do not cause any harmful interference to the respective incumbent users (i.e., primary users). One of the possible approaches consists in having the secondary users locating and accessing vacant frequencies dynamically. However, in scenarios with hidden primary users (i.e., a secondary user cannot sense a primary user on its respective channel, but the two coverage areas overlap each other), it is unfeasible to address the protection of primary users with solutions which are exclusively based on local and non-cooperative sensing schemes. In this work, we propose a cooperative approach which enables an effective protection of primary users in fully distributed CR scenarios, even when the hidden node problem is a concern. Our proposal is based on a key concept we designate as “filtering based on suspect channels” and takes full advantage of any underlying learning scheme based on observation and past experience. It was also successfully integrated with an existing CR medium access control (MAC) protocol. Simulation results show the proposal is effectively capable of delivering high levels of protection concerning the primary users, while preserving the secondary users' communication performance.