A survey of dynamic spectrum access

Hierarchical access model categorized under dynamic spectrum access means to open licensed spectrum to secondary users while limiting the interference perceived by primary users (licensees). Under the model, the term Opportunistic Spectrum Access (OSA) is relevant. Basic components of OSA include spectrum opportunity identification, spectrum opportunity exploitation and regulatory policy. The opportunity identification module is responsible for accurately identifying and intelligently tracking idle frequency bands that are dynamic in both time and space. The opportunity exploitation module takes input from the opportunity identification module and decides whether and how a transmission should take place. The regulatory policy defines the basic etiquette for secondary users to ensure compatibility with legacy systems. The overall design objective of OSA is to provide sufficient benefit to secondary users while protecting spectrum licensees from interference. Meanwhile, in the US, the FCC is studying ways to advance secondary markets, such as via interruptible leasing. A supporting policy could be fixed or open to dynamic negotiation and bidding; it could be centralized or decentralized. It can be expected that intramilitary system, as well as intracommercial systems, can benefit greatly from policies allowing spectrum sharing. A wide range of policies are easily envisioned, spanning non aggressive to a aggressive or restrictive to permissive.