To improve WWAN coverage, an access node broadcasts overhead messages on a first channel covering a first channel environment and a second channel covering a second channel environment within a coverage region. The overhead messages carry network overhead parameters for allowing wireless mobile devices to acquire and maintain traffic channels within the cellular system. The overhead message channels are configured so that a user perceives uninterrupted wireless services while moving through different channel environments in the coverage region. In one embodiment, the overhead message channels are separate physical channels configured with different broadcast parameters to provide coverage in different environments. In another embodiment, the overhead parameter information is segregated into base and extended components that are encoded and layer modulated onto separate logical channels. Using layered modulation, wireless mobile devices can receive base components in poor coverage regions. The base components include overhead parameters for acquiring a WWAN channel.