This document discusses IBOC (In-Band On-Channel) technology, which allows digital audio broadcasting without requiring new spectrum allocations. IBOC inserts a digital sideband signal within the existing AM and FM bands, allowing digital and analog signals to be transmitted simultaneously on the same frequency. The document outlines IBOC's hybrid, extended hybrid, and all digital modes of operation, as well as techniques for implementing IBOC such as low-level and high-level combining. Benefits of digital audio broadcasting include high quality digital audio and added value features, while adoption has been delayed due to issues like interference and costs.