White spaces (radio)

White spaces, in the context of radio, refer to the unused portions of the radio frequency spectrum. These spaces are frequencies that are licensed to a broadcaster, but are not actively being used at a particular time or in a specific geographic location. They can arise due to a number of factors, including variations in broadcast coverage areas, different channel allocations in different regions, and the use of licensed frequencies only during certain hours of the day.

The term is particularly relevant in the context of television broadcasting. Historically, analogue television signals required a significant bandwidth, and the allocation of channels often resulted in gaps between active channels to avoid interference. With the transition to digital television (DTV), the bandwidth required for each channel decreased, freeing up more spectrum for other uses.

This unused spectrum, the "white spaces," represents a valuable resource. There has been considerable interest in utilizing these spaces for other wireless communication technologies, such as wireless broadband internet. The potential to repurpose white spaces offers the opportunity to expand wireless connectivity, especially in rural areas or areas with limited infrastructure.

However, the use of white spaces requires careful regulation to prevent interference with existing licensed users. Technologies that operate in white spaces must typically incorporate features to detect and avoid occupied channels. Regulatory bodies, such as the Federal Communications Commission (FCC) in the United States, have established rules and guidelines for accessing and using white spaces, including requirements for geolocation and database access to determine available frequencies. The utilization of white spaces is often referred to as TV white space (TVWS) technology when it involves spectrum originally allocated to television broadcasting.