In a report  (PDF, 62 Pages, 938 KB) released by the Government Accountability Office (GAO), the organization notes that "After the investment of significant resources - including billions of dollars in federal grants and approximately 100 megahertz of radio frequency spectrum - the current land mobile radio (LMR) systems in use by public safety provide reliable 'mission critical' voice capabilities." The report went on to find, however, that with regards the implementation of a "public safety broadband network," several challenges remain unresolved, including "ensuring the network's interoperability, reliability, and security; obtaining adequate funds to build and maintain it; and creating a governance structure."