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PUBLIC SAFETY TECHNOLOGY HOW P25 PROMOTES INTEROPERABILITY Photos courtesy Bureau of Land Management An update on the P25 standards work and public-safety case studies By Jack Doane MMission-critical interoperability cannot be resolved by broadband alone. Project 25 (P25) and other LMR technologies will continue to provide the primary push-to-talk (PTT) voice solution for public-safety agencies for years to come. Much of the recent attention regarding mission-critical communications has been captured by the future nationwide public-safety broadband network that will hopefully provide the capabilities public-safety practitioners need to support all of their operational needs. Until that network is realized, P25 will continue to provide that capability to public-safety agencies at all levels of government in the United States and in many countries throughout the world. During the past 20 years, P25 has improved interoperability among those agencies and continues to increase operability by working with the P25 User Needs Subcommittee (UNS) to increase the features and functions available for mission-critical communications. Broadband may eventually provide the flexibility public safety needs, but that may be years to come. Broadband is ideal for data-intensive applications in infrastructure-rich areas of the country, but broadband may not provide a workable, reliable, secure mission-critical PTT solution in the near or mid-term. Public-safety practitioners who look to broadband to solve communications gaps should think in terms of the evolution of LMR as it relates to interoperability, not the revolution that broadband represents. Most agree that mission-critical PTT voice is an essential requirement that now can only be satisfied with some form of LMR technology that supports radio-to-radio direct, repeater and trunked solutions, which is why it is important to support P25 standards for the foreseeable future, to enhance interoperability and provide multiple sources with standards-compliant tech-
Nonstandard encryption recently implemented by some vendors is not secure, and more importantly, it is not interoperable with the encryption technology compliant with the P25 standard. nology. In other words, LMR will be with us for a long time, and we need to continue with a working technology that provides interoperability and cost effectiveness. Interoperability has changed considerably during the past several decades. Prior to the introduction of trunked communications and digital technologies, interoperability was as simple as sharing frequencies between neighboring jurisdictions. The introduction of digital, trunked communications technologies dramatically changed the way agencies operate. As deployments began in the 1980s, an interoperability gap was created when agencies could no longer communicate with each other depending on the technology they chose. Unfortunately, interoperability took a back seat to new features and expanded capabilities, and the new digital technologies sometimes made communications between agencies more difficult. As technologies improved and more digital systems were introduced, less thought was given to interoperability contributing to the divergence of compatible digital systems, until the introduction of P25 digital standards. Initially, P25 started with the requirement to improve interoperability as agencies moved from analog to digital communications. The P25 standard quickly evolved into more than interoperability. It stressed enhanced spectral efficiency, backward compatibility to existing systems providing an improved migration path between technologies, and enhanced competition among manufacturers. Without competition, public-safety agencies knew they would be unable to obtain effective pricing and value from system and component procurement. Although P25 radios are typically more expensive than their analog counterparts and some digital product offerings, P25 technology provides the flexibility that no other standard can duplicate. P25 offers multiple tiers of radios that range from analog operation plus the basic P25 radio to a full-featured radio with trunking, encryption, data and advanced security features, all providing full interoperability and backward compatibility. P25 radios providing basic functionality are also available at a significant savings compared with the cost of radios providing full-featured, multiband trunked options. The P25 standard has created a competitive environment that has improved cost benefits in the digital land mobile marketplace. Users now have more options for competitive procurements of standardized equipment. As of March, more than 35 companies provide P25 equipment and services, and the manufacturers continue to add standardized features and functions to serve the user needs. P25 Goals The Project 25 Steering Committee realized that interoperability would not be possible unless there was a core capability that allowed basic communications between every radio. Working with the Telecommunications Industry Association (TIA), P25 developed a Common Air Interface (CAI) and a standardized voice encoder (vocoder) that would allow direct mode communications between subscriber units and infrastructure. The CAI is the basis of the P25 standard and is the only required interface to ensure interoperability at the basic level. The CAI and the P25 vocoder together are required for interoperability, ensuring compatibility among all P25 manufacturers. Among the primary requirements of the P25 standard was to provide backward compatibility to help maintain interoperability and allow agencies to gracefully migrate to new technologies. Phase 1, a 12.5-kilohertz FDMA solution, requires backward compatibility to analog FM. Phase 2, a 6.25-kilohertz two-slot TDMA solution, requires backward compatibility to P25 Phase 1 with an optional requirement to be backward compatible to analog FM. Few other technologies provide this level of backward compatibility. To aid in technology migration, the P25 standard also requires backward compatibility to a manufacturer s legacy technology for P25 Phase 1. Recognizing that mission-critical requirements were becoming more complex, the P25 Steering Committee, working closely with the manufacturing community, added additional interfaces, functions and features to enhance interoperability. P25 is not a single communications technology standard; it is more of a living standard that continues to grow with technology and the needs of first responders. The P25 standards suite is defined in more than 85 standards publications that cover conventional operation, trunked operation, FDMA and TDMA technology, and security services for mission-critical applications. In addition, there are a number of P25 standards documents that provide specific test procedures and recommended compliance assessment tests. Regardless of which options and features are implemented, there is a baseline interoperability requirement for conventional FDMA Phase 1 operation. P25 Benefits P25 technology provides opportunities to public-safety agencies that were otherwise unavailable, including compatibility across technologies, multiplatform and multiband operation, and intersystem connectivity. The standard provides compatibility among analog FM, FDMA and TDMA solutions and allows communications between conventional and
trunked users at the subscriber unit level. In some cases, the Inter RF Subsystem Interface (ISSI) allows users to communicate over wide-area networks and between networks independent of system manufacturer, configuration or frequency band. In recent months, advances have been made in the standard s Console Subsystem Interface (CSSI) and Digital Fixed Station Interface (DFSI). In March, 12 P25 equipment vendors participated in a demonstration of the capabilities applicable to the CSSI and DFSI. In addition, P25 has provided a means to effectively implement a secure interoperability solution for users. While encryption may be considered by some to inhibit interoperability, standardized encryption technology and management has made secure interoperability a reality within the P25 standard. Recent discussions in the community and press have highlighted the negative aspects of encryption in P25 systems. Critics point out why they think encryption has not enhanced interoperability, but what they don t explain is how encryption can improve aspects of public-safety communications. The cost differential for P25 encryption is significantly less than the cost for encryption only several years ago. It doesn t increase the amount of spectrum used or decrease audio quality or performance, and it is standardized. A critical point to note is that the nonstandard encryption recently implemented by some manufacturers is not secure, and more importantly, it is not interoperable with the encryption technologies that are compliant with the P25 standard. Although a cost savings, or cost avoidance, may be realized, implementation of nonstandard encryption will likely adversely affect interoperability and decrease the ability to conduct a competitive procurement in the long term. Only through the use of the P25 Advanced Encryption Standard (AES), does an agency enable the greatest opportunity for achieving maximum interoperability and competition while providing a high level of protection. Lastly, few technologies in the mission-critical marketplace can claim to be user driven with active support from the manufacturing community. The P25 Steering Committee consistently looks for methods to engage the user community in the refinement of user requirements and to use their operational expertise to make meaningful contributions toward the design and development of the standards. There are currently 15 manufacturers providing infrastructure, 15 providing subscriber units, and 24 providing supplementary hardware and services. Interoperability in Practice There are many examples of P25 systems installed in the United States and abroad. It has become a primary standards-based radio system for mission-critical communications at all levels of government. The technology is the required standard for most federal LMR systems and the favored standard for state, tribal and local public-safety systems. The primary reason for this is because P25 provides public-safety agencies with four key benefits interoperability across vendor platforms, backward (and forward) compatibility to enable graceful migration (analog to Phase 1 FDMA to Phase 2 TDMA), competition among vendors, and enhanced encryption services to ensure end-to-end protection. A few notable examples follow. One of the first statewide P25 systems to be implemented was the Alaska Land Mobile Radio (ALMR) system. It s based on a partnership of federal, state, native and local publicsafety agencies across the state of Alaska and provides a standards-based platform for shared resources (infrastructure, spectrum and funding),
interoperable communications for day-to-day as well as disaster operations, and common system maintenance and management. One of the reasons the P25 standard was chosen by the ALMR partnership was the provision of choices for users in the acquisition of subscriber units, says Del Smith, ALMR operations manager. We currently have approved seven manufacturers radios for use on the system and continue to contact other manufacturers to encourage them to test on the ALMR system to broaden the choices for our users even more. Another example of how the standard has enhanced interoperability is the state of Wyoming. WyoLink, a P25 statewide mission-critical communications system similar to ALMR, is used at all levels of government for day-to-day as well as task force and disaster communications. WyoLink also uses the shared resource approach, which means the spectrum is shared among federal, state and local agencies, as well as the shared use of communications sites and facilities. The WyoLink system has further enabled municipalities to become interoperable with other agencies throughout the state and share in the cost savings of a common architecture approach. The P25 standard provides for multiple vendor equipment to operate on WyoLink, which helps provide competition between vendors and reduces the purchase prices of the end user equipment, says Bob Symons, the Wyoming statewide interoperability coordinator (SWIC). Wyoming has allowed vendors to use WyoLink to test their P25 VHF equipment and user options. In 2010, Wyoming and Colorado participated in a test of a P25 ISSI between the Colorado Digital Trunked Radio system and WyoLink. Colorado The Bureau of Land Management (BLM) firefighters use P25 technology. operates an 800 MHz digital trunked radio system, and WyoLink is a VHF digital trunked radio system. The vendor-hosted test was successful in combining talk groups on each system, and users in both states were able to use their home systems to communicate with the other state s users through the ISSI. Colorado and Wyoming officials are reviewing potential funding to acquire the ISSI for their systems. Communications interoperability is a must for the citizens of Wyoming, said the Wyoming Association of Municipalities. A statewide radio system will involve many different kinds of entities having a voice in the ongoing operation of the system. It is critical we form a governance structure that will endure. Many cities, counties and other jurisdictions have also implemented P25 standards-based systems to enhance interoperability, increase competition and save public funds. It is estimated that more than 10,000 P25 systems have been implemented in the United States alone. One example of a small-scale installation is the Dallas-Fort Worth International Airport, which operates a P25 system for internal purposes and to enable interoperability with neighboring jurisdictions. The DFW P25 system supports regional emergency preparedness, increased security and reliability, and supports cost effectiveness through resource sharing, says Bill Bowen, the former ITS project manager of the DFW International Airport Board. The standard provides a common forum for manufacturers to develop interoperable and compliant products and for users to outline their requirements prior to the development of the product. P25 allows manufacturers to offer additional features but requires a base level of interoperability to ensure users will always be able to communicate. In a time when technology is advancing at a rapid pace with the promise of high-speed data, streaming video and Internet access at the subscriber unit, mission-critical voice remains the predominant requirement of public-safety agencies at all levels of government. Access to reliable PTT voice communications is essential to the safety of life and property. Jack Doane is vice chair of the Project 25 (P25) Steering Committee and a National Association of State Technology Directors (NASTD) representative. Email comments to editor@rrmediagroup.com. RadioResource MissionCritical Communications delivers wireless voice and data solutions for mobile and remote mission-critical operations. Editorial content targets organizations in the United States and Canada with mobile and remote communications needs, including public safety, government, transportation, manufacturing, utility/energy, business, and industrial entities. The magazine covers industry news; case studies; innovative applications; product information; emerging technologies; industry reports and trends; and technical tips. In addition, each issue contains Public Safety Technology, a special section devoted solely to the needs of the public-safety community. RadioResource MissionCritical Communications is published by RadioResource Media Group. Pandata Corp., 7108 S. Alton Way, Building H, Centennial, CO 80112, Tel: 303-792-2390, Fax: 303-792-2391, www.rrmediagroup.com. Copyright 2013 Pandata Corp. All rights reserved. Reprinted from the October 2013 issue of RadioResource MissionCritical Communications. For subscription or advertising information please call 303-792-2390 or visit www.rrmediagroup.com.