ABI Research said LTE has emerged as a challenger to existing public safety communication protocols in recent years. Continual refinements from 3GPP Releases and commercial collaboration between TETRA and P25 vendors with LTE vendors are turning first responder and public safety LTE into a reality. Thus the research company estimates that the total number of public safety LTE user subscriptions will reach 11 million worldwide by 2020, with a market size of $5.1 billion (€4.6 billion). It also predicts that the United States, United Kingdom and South Korea will be the first three markets to have a fully functional public safety LTE network by 2017. Release