Heightened awareness of the integral role of the nation's wireless communications infrastructure in homeland security is bringing to the fore technical issues about public safety spectrum that have lain fallow for a number of years. This book covers issues concerning technology, the connection between technology standards and spectrum allocation, and the competition for spectrum among many users with diverse needs. The report in particular addresses two key issues that have attracted significant attention and controversy: interoperability and interference. Interoperability questions focus mainly on spectrum needs and compatible technology. Interference problems stem primarily from spectrum allocation decisions and radio-communications engineering that have combined to disrupt some public safety radio transmissions. Originally viewed by most industry stakeholders as separate topics, the two issues have, over time, coalesced into a single concern that questions different aspects of spectrum policy and technology planning.