PU primary user

In the context of wireless communication and spectrum management, a Primary User (PU) refers to a licensed entity or system that has the exclusive rights to access a particular frequency band or channel. The term "primary" implies that the PU has priority access to the spectrum resources over other users.

The concept of primary users is primarily associated with cognitive radio systems, which are designed to dynamically utilize underutilized or temporarily vacant frequency bands, known as white spaces. These white spaces exist between the frequency bands allocated to primary users. Cognitive radio systems aim to improve spectrum efficiency by allowing secondary users (SUs) to opportunistically access and utilize these white spaces while ensuring that the primary users' communication needs are not compromised.

The role of primary users is crucial in cognitive radio networks because they operate in licensed frequency bands and have the highest priority access rights. Primary users are typically authorized by regulatory bodies, such as government agencies or spectrum management authorities, and they can be various entities, including wireless service providers, public safety organizations, broadcasters, military systems, or other critical infrastructure operators.

Primary users are responsible for ensuring interference-free communication within their allocated frequency bands. They have the authority to initiate, maintain, and terminate communications without interference from secondary users. Additionally, primary users may deploy spectrum sensing techniques to detect the presence of secondary users in their frequency bands and take appropriate actions to mitigate interference if necessary.

The presence of primary users in cognitive radio networks requires secondary users to perform spectrum sensing and dynamic spectrum access. Secondary users, also known as unlicensed users or opportunistic users, are typically lower-priority users who can access and utilize white spaces when they are not occupied by primary users. Secondary users must employ spectrum sensing mechanisms to detect primary user activity and vacate the frequency bands promptly when primary users need to access them.

To summarize, primary users are licensed entities that have exclusive rights to access specific frequency bands or channels. Their presence in cognitive radio systems ensures that they maintain priority access to the spectrum resources while secondary users opportunistically utilize white spaces without causing interference. The primary user concept is vital for efficient spectrum management and ensuring the reliable operation of licensed wireless communication systems.