In view of broadband technology trends and the availability of broadband spectrum, public safety agencies have expressed an interest in complementing their current narrowband wireless networks with broadband systems. To support the set of public safety data applications, Long Term Evolution (LTE) has been selected by the U.S. Federal Communications Commission for deployment in the broadband portion of the U.S. Public Safety 700 MHz band. This event, together with the mandated migration of narrowband systems to narrower channel widths, are the catalysts for current requests to carry mission critical voice services over the future LTE-based public safety broadband wireless network. Since such services have stringent requirements, this paper covers challenges with an emphasis on interoperability with legacy narrowband systems. © 2011 Alcatel-Lucent.