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GCN : May 2013
TECH ANALYSIS INTER-NETWORKS GCN MAY 2013 • GCN.COM 25 the program, and participating states will build out their own systems and interconnections with the backbone, possibly with federal help. Because of its mission-critical na- ture, "You have to have a system built to higher standards than commercial cellular networks," said Raymond Lehr, Maryland's interoperability di- rector. It also must be dedicated to public safety use so that officers are not competing with the public for bandwidth. Many law enforcement and other first responder agencies now use com- mercial cellular and IP data services, and they are useful in supplementing traditional land mobile radios that most departments rely on. But during emergencies commercial infrastruc- tures are vulnerable to damage, and first responders have to compete with the general public for limited band- width and air time. COST REQUIREMENTS Despite the challenges of building out such an ambitious network, the tech- nical hurdles could be dwarfed by political, organizational and financial challenges. The new network will have to meet the needs of more than 60,000 feder- al, state, local and tribal agencies and do it for no more cost to the end us- ers than what agencies are paying now for commercial services. The national network also will have to accom- modate emerging state and regional public safety networks that are being built out to provide intercommunica- tions for state and local agencies. And few people believe that a network on this scale can be built for the $7 bil- lion FirstNet has been authorized to spend --- if the money ever becomes available. Some, but not all, state public safety WHY LTE IS THE NEXT GENERATION IN WIRELESS There is a lot yet to be decided about the new nationwide public safety network whose birth is being overseen by the First Responder Network Authority. But one thing is known. "We are going to implement an LTE system," said FirstNet chairman Samuel Ginn. WHAT IT IS The Long Term Evolution standard for advanced cellular communications is an emerging standard being embraced by commercial carriers. It holds the promise of an interoperable network based on non-proprietary, commercially available technology. LTE is being developed by the 3rd Generation Partnership Project, made up of six telecom standards organizations. It has begun appearing in commercial o erings as 4G --- or fourth generation --- wireless service, although only the LTE Advanced standard finalized in 2011 is recognized by the International Telecommunications Union as true 4G wireless. HOW IT WORKS LTE operates in a range of frequencies, including the 700 MHz band in which the Federal Communications Commission has set aside a block of spectrum for the public safety network. It is built on TCP/IP and provides a packet-based alternative to earlier circuit-switched wireless networks, o ering the ability to support a variety of devices using multiple services, including voice, video and data. PERFORMANCE Current implementations provide peak downlink rates of about 300 megabits/ sec and 75 megabits/sec for uplinks. It incorporates quality-of-service provisions to minimize latency, enabling e ective hando s for fast-moving mobile devices. One LTE cell operating with a 5 MHz slice of spectrum can support up to 200 data clients. Voice tra c can be carried either as a packet-switched data stream or as circuit-switched tra c over a legacy voice network. LTE s support of Half-Duplex FDD (with only a one- direction channel in operation at a time) enables the use of push-to-talk features that can be used by police to access traditional land mobile radio systems. LONG RANGE LTE has been gaining momentum since 2008 as an alternative to the more widespread WiMax. Use of both technologies is expected to continue to grow.