Miami ERRCS Requirements – A Unique Approach
By Will Washburn
As the requirement for Public Safety systems increases, much attention has been focused on the AHJ’s ability to navigate the efficacy of the system’s integrity. Delivering an effective ERRCS solution requires careful attention in the design and RF engineering of the DAS solution as well as the protection of the municipal system.
Important detriments are noise floor creep and interference and oscillation. Class A markets have a better chance of maintaining low noise floor levels than Class B markets. Class A repeaters are channelized and amplify only the channels required in a jurisdiction. Class B are wideband repeaters and transmit all of the frequencies between a certain range, and can also amplify noise floor. This can be problematic if careful attention to isolation is not maintained. A perfect example is Denver where the noise floor was elevated too high by the cities’ vendors deploying too many Class B systems without attention to this proclivity.
I must applaud the Miami radio shop folks as they have been able to successfully supervise the City’s vendors and only have raised the noise floor by 1 dB in this Class B market, according to the former head. This is mostly because they take a hands-on approach in the selection of coverage and antenna placement for projects in their jurisdiction. In this jurisdiction, the primary focus is covering the core and elevators of the buildings which reduces the exposure to oscillation or interference by reducing antenna density in the perimeter of the buildings. By completing a comprehensive signal survey and benchmarking, and a site visit testing, uplink, and downlink, the AHJ and Vendor can consider coverage in only the required areas, reducing the potential for interference.
Another proclivity to note, in this jurisdiction, is the allowance of antennas in the elevator shafts. Most jurisdictions do not allow anything in the elevator pits or shafts. Antennas inside the elevator shafts increase the coverage capability of penetrating a steel enclosure that resembles a moving faraday cage. Elevators are considered a “sensitive area” and 99% coverage is required in sensitive areas in most jurisdictions. Enforcement has been relaxed due to the difficulty of attaining 99% coverage, however, more AHJ’s have stepped up code compliance in this area.
Vendors and AHJ’s alike must work together to deliver code-compliant systems that not only serve the enterprise client but protect the municipal systems from interference and the vagaries of poorly engineered solutions.
Will Washburn, is the CEO of Combined Operations for Digitechx Wireless Inc., a national provider of wireless services to the enterprise markets.