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Broad Coverage and Disparate Access with Mission Critical Availability for First Responders

Mon, 12/17/2012 - 3:25pm
Keith Mallinson

Today’s public safety wireless networks reflect much of what is wrong with historic airwave allocations. Different user groups are served in fragmentation by numerous incompatible systems. This feudal system using relatively old technologies makes for inefficient use of prime spectrum resources.  It is all overdue for a major overhaul. A new LTE-based broadband public safety network with shared use of 20 MHz in the 700 MHz band including the D Block and Public Safety Spectrum Trust frequencies is full of promise, but with limitations and risks.

Starting over

In February 2012, the Middle Class Tax Relief and Job Creation Act of 2012 was enacted to create the “First Responder Network Authority,” (FRNA) referred to as FirstNet, as an independent authority established within the National Technology Information Administration (NTIA).  FirstNet’s mission is to establish a nationwide, interoperable public safety broadband network. This is a second attempt to do this in the D Block, following the failed auction of this spectrum in 2008 when the reserve price of $1.3 billion was missed by a mile due to the onerous conditions on commercial partners with the proposed shared-usage license. The new legislation includes a network construction trust fund of $7 billion with an initial $2 billion which will at least ensure something gets built this time. However, additional funding will need to be raised in auction from commercial partners. 

Numerous individuals, companies, trade associations, government agencies and public-safety organizations have recently submitted comments to the NTIA in a consultation on plans to build this proposed network. Wireless carriers Verizon Wireless and Sprint Nextel are in favor of commercial players building and operating the network, while expressing concerns about how networks will be managed.  On the other hand, public safety agencies are most interested in how first responders can preempt commercial users. This conflict may not easily be resolved with the FirstNet’s large and complex organization and governance. Hopefully, lessons learned from the previous attempt to create a national public safety network will make all parties more amenable to finding a workable solution.

Single national network architecture

FirstNet will develop and operate the new broadband network, which is to be based on a single, nationwide network architecture using large and efficient frequency blocks. This will provide first responders and public safety officials with broadband communications within and across jurisdictions. This secure and interoperable network will support the kinds of multimedia applications that are becoming available on mobile devices elsewhere in industry and with consumers – for example, enabling firefighters to download blueprints of burning buildings in order to plan their entry route, allowing emergency medical technicians to remotely access a victim’s medical records from an ambulance, or helping police to identify criminal suspects through facial recognition or iris scanning technologies.

Not only will this network provide hardened capabilities with interoperability among different emergency services, it could also provide superlative geographic reach and additional capacity for commercial and consumer access. Engineering design will enhance “carrier grade” capabilities to “mission critical” resilience with continuity of service when commercial cellular networks fail. While visiting cell towers in coastal areas affected by Hurricane Sandy recently, I noticed that typically only one of five or six commercial cellular carriers even had the on-site backup generator required to maintain service during the storm-induced power outages. The new network should be designed with resilience to maintain service through various disasters including wind, flood and earthquakes.

The use of 3GPP-standardized technologies, including LTE, pays enormous benefits with the enormous R&D support that has delivered the highest performance and most spectrum- and power-efficient capabilities. It also helps enable and maximize multimedia applications, with network roaming possibilities and with large economies of scale in devices. There will, however, be some wrinkles.  Spectrum band support in devices is already fraught with immense complexity and fragmentation.  Introducing an additional band class for a relatively small base of users will not be a motivator for all device manufacturers.  For example, Apple might never include the band in its iPhones.

What about voice?

It will be many years, if ever, before the new network can be the primary or only network for first-responder voice communications. Integration of data and voice-over-IP is the Holy Grail on mobile networks, as it has been on fixed networks for many years, but use of 4G LTE (that does not offer circuit-switched voice) means that the only possibility for voice on this new network will be VoLTE. The voice application is most exacting on wireless networks and requires superlative QoS while sharing the data pipe to the cell edge with various high-demand applications; but VoLTE is still immature. There is no more mission-critical an application for first responders than voice.  With push-to-talk, for example, the difference between “shoot” and “don’t shoot” is only a couple of hundred milliseconds’ packet loss or delay. Following various false starts in mobile VoIP over the last decade, commercial carriers AT&T and Verizon are only starting their baby steps with VoLTE on their networks over the next year or two, while set to remain highly dependent on their 2G and 3G circuit-switched voice networks for many years. Similarly, existing or new private land mobile radio will be even more essential for voice communications for many years. Public safety narrowband (i.e., P25 voice) spectrum is being maintained for that purpose.

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