Everyone Has to Play Nice
What is noisy enough to disrupt your business and can last just a few seconds or all day long? The majority of the LMR spectrum is shared, so now you have analog voice systems sharing spectrum with new types of digital equipment. That means that, suddenly, your neighbor’s choice of radio system can become a big problem for you. Whether it is a GPS system used to track school buses or a radio being used to move irrigation wheels on a farm or the persistent on-again-off-again sound of a DMR system being keyed up, these interruptions have all become a daily part of the lives of many using Land Mobile Radios (LMR).
Digital equipment that operates at 6.25 and 12.5 kHz bandwidth along with TDMA (Time Division Multiple Access) radios, designed to operate along two paths within the 12.5 kHz bandwidth, are now being utilized by many types of organizations. While the benefits of a DMR system are obvious, both analog and digital licensees need to know how a DMR system could impact the spectrum environment they share. By knowing what type of signal their system transmits and taking time to monitor the frequency prior to transmission, users can help to alleviate any potential harm to a co-channel neighbor.
The FCC and the Land Mobile Communications Council (LMCC) —which is made up of the FCC certified Industrial/Business and Public Safety Frequency Advisory Committees (FAC) — are aware that a Digital Mobile Radio (DMR) system has the potential to cause harmful interference to an analog licensees more than the another analog licensee can. Reports of interference from co-channel licensees and FCC inspections of licensed stations show that many problems are caused by those transmitting on a digital emission while licensed as an analog operator, leading to a Notice of Violation (NOV). And this increased reporting can have additional – negative – impacts.
For example, a pipeline company in Georgia found this out when a report of interference from a co-channel user prompted a visit by the FCC. The pipeline company was operating a repeater system on a frequency that was authorized for use as a mobile only system and they were licensed for analog but using a digital emission. In another example, a rescue squad in Pennsylvania reported for interference ended up receiving three violations. The first was for transmitting a digital signal while licensed for analog, the second was for not properly transmitting their call sign and the third was for not monitoring the system for communications in progress before transmitting. Both the pipeline company and the rescue squad received Notices of Violation and will be liable to fines.
The FCC is placing increased emphasis on confirming the emission designators for the license as it was granted and investigating violations. The emission designator on the license identifies the signal that the licensee is authorized to operate on their radios. During an investigation, if the emission designator type on the equipment is not the same as authorized on the license the licensee will be found to be not in compliance with the FCC Rule 1.903(a). A breakdown of the types of emissions can be found under FCC Rule 90.201 at the FCC Rules and Regulation website.
EWA has a Memorandum of Understanding (MOU) with the FCC pertaining to the resolution of interference and compliance in the Industrial/Business pools since 1998 and, therefore, fields interference complaints including the increased DMR interference complaints on systems operating as repeaters, base and mobile and non-voice uses including surveying or GPS units.
The LMCC has created a “Best Practices” document to remind licensees that, in a shared spectrum environment, license holders have a responsibility to monitor their frequencies and ensure that they are functioning with an operational station ID. Further, licensees are reminded of their obligations and responsibilities and must understand what type of system they are authorized to operate and the difference between an analog and digital emission. The type of emission they are operating on their equipment must match the emission designator that is authorized on their license that can be found at the FCC Universal Licensing System (ULS) website.
EWA has created an e-Advisory that provides information to spectrum applicants including the following:
- System Description
- Radio Service
- Emission Designator(s)
- Station Class(es)
- Applicable FCC Rules
- Station Identification Obligation
- Shared Spectrum Awareness
- Channel Monitoring Obligation
The e-Advisory notifies recipients they can request a Channel Sharing Report, providing a co-channel listing of the current licensees authorized on the coordinated frequency. If there appears to be licensees that are not compatible with their system, a licensee can notify the appropriate EWA Spectrum Analyst, who can arrange for a replacement frequency and amended application.
Digital Mobile Radio is a reality today and it is every radio licensee’s responsibility to ensure unencumbered access to licensed spectrum in a shared environment.