1. A synchronous spectrum sharing system for use in a wireless communication system having a primary user node and a secondary user node, the system comprising: a frame detector configured to: detect a frame of a broadcast waveform, the broadcast waveform being an OFDM waveform or an OFDMA waveform, extract down-link and up-link channel assignments for blocks within a dedicated network subchannel from the frame, and identify idle spectrum blocks within the dedicated network subchannel of the frame using the extracted down-link and up-link channel assignments.