Issue link: https://www.e-digitaleditions.com/i/1255991
July/August/September 2020 I 53 For detailed information about the design and installation of passive and active DAS, including hybrid solutions, consult the ANSI/BICSI 006-2020 Distributed Antenna System (DAS) Design and Implementation Best Prac- tices standard. ANSI/BICSI 006-2020 thoroughly addresses public safety and contains a special section about the par- ticular needs of schools in section 10.7. Common deployment delays, such as DAS alarming, battery backup alarming, and insufficient RF coverage at critical areas (e.g., elevators, stairwells, battery backup) can occur, but with proper planning upfront and engag- ing the right partners, school districts can save time and money. Many districts throughout Florida are issuing requests for proposals (RFPs) to develop two-way radio communi- cation systems for entire campuses. These public safety projects are designed to cover elementary, middle, high schools and administration buildings. In coordination with AHJs, OEMs are currently working with the counties to deploy a state-of-the-art public safety system in all the schools that fail the mandated grid testing required throughout the state. 5G PUBLIC SAFETY DEPLOYMENTS While 5G is promising for many commercial use cases and massive IoT applications supporting public safety needs, portions of the LTE spectrum still remain sufficient for in-building wireless communication systems meant for first responders now and in the near future. It is what all mobile carriers continue to use for their public safety networks, including FirstNet. This is largely because of the new deployment challenges that arise as a result of the frequency bands used for 5G. The 4G/LTE frequency bands are characterized as traversing long distances and can more easily penetrate building materials without severe attenuation of RF signals. Conversely, 5G frequency bands that deliver faster speeds and ultra-reliable low- latency communication (URLLC), such as mmWave, travel much shorter distances and are more easily dis- rupted by walls and environmental interference. These issues for both outdoor and indoor connectivity makes 5G akin to a "hotspot" for better connectivity supporting specific applications over the blanket coverage people typically associate with LTE. Due to these limitations, in-building deployments may require additional wireless infrastructure to provide ubiquitous coverage to the same area, such as additional repeaters, DAS or the inclusion of cloud radio access net- works (C-RAN) small cells. Using small cells as a stand- alone solution is not cost-effective because of the many devices it would take to fill a school with complete cov- erage. When and if LTE is completely phased out, carrier aggregation will likely occur, delivering 5G with a lower frequency band, which provides equivalent speeds but also reduces the infrastructure needed. In preparation for 5G, schools should consider developing a commer- cial network parallel to the public safety network by run- ning structured cabling and implementing a DAS that supports the 5G frequency bands. Currently, Verizon uses 28 GHz and 39 GHz, AT&T uses 39 GHz, and T-Mo- bile/Sprint uses 600 MHz, 28 GHz, 39 GHz, and 2.5 GHz. According to ANSI/BICSI 006-2020, "To provide ade- quate bandwidth and coverage, a DAS may need to be supplemented by either small cell antenna or cloud radio access networks (C-RAN) solutions to distribute 5G sig- nals in buildings with large number of users that wish to use 5G mobile phones within the building." As described earlier, the mobile phones used by peo- ple in schools and other first responders are part of the overall public safety system, so the in-building wireless infrastructure should be able to support 5G as users migrate to 5G devices (e.g., smartphones and tablets). To prepare for this transition and an evolving DAS infra- structure solution, such as a C-RAN based small cell system, at minimum the telecommunications cabling In public safety systems, the propagation characteristics of the low frequencies dictate the use of an active or passive DAS based on the size of the building and its required coverage needs.