How to bridge the gap between LMR and wireless broadband
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As the project moves to the buildout phase, attention turns to on-site requirements. Professional engineering studies for the tower and rooftops can include future expansion for future services. Again, when crews are installing antennas and lines, they can clean old antennas and lines to make room for future considerations. Zoning and construction permits, civil engineering for roads, site grounding, and power facilities for towers and rooftops — as well as cable runs and wall penetrations for rooftops — all can be prepared for current and future needs.
Meanwhile, network connectivity, data transmission and backhaul are elements of the LMR design that can be optimized for current and future requirements. Routers can be dimensioned with extra ports for future expansion. Data transmission in the form of Ethernet, coaxial cable or fiber optics — along with site-to-network backhaul connectivity in the form of microwave radio, fiber optics or satellite links — can be prepared to meet the needs of today and tomorrow.
Once the system has been turned on for normal use, there will be a need to monitor operation, with alarms and reports generated for abnormal operation. It also is important to track equipment that may need to be replaced, because of failures or operations outside of the design specifications.
The project manager is responsible for the system documentation. System diagrams should be detailed enough to show where equipment is located and where addtional equipment can be placed, if broadband is layered into the system. This should be shared with engineers.
A project manager must ensure that even non-radio components are maintained, so that the site remains operational.
The tower or rooftop must be kept in good shape, so that it does not fall or collapse. This includes monitoring and addressing issues such as rust, maximum weight load, maximum wind load, and pieces that could become projectiles, if loosened. Any old or abandoned antennas or transmission lines should be removed from the tower to reduce weight and wind loading. On a guyed tower, the guy wires must be torqued and tension tested periodically.
Rooftop sites are similar to towers, but there is usually more horizontal space and less vertical space.
Grounds and grounding are very important to any site installation. Typically, properly installed grounding requires little maintenance, so project managers must ensure that proper grounding is part of the initial installation phase.
The building or buildings, fences, gates, generators, transfer switches, alarm systems, air conditioning, heating, plumbing, lighting, and other systems and subsystems play key roles in keeping the site operational. Radios and antennas at the site must meet specifications, and all equipment should work as specified during acceptance testing.
The capacity to add equipment should be part of the documentation, and any equipment placed into service after the initial construction phase should be kept current. As equipment is added to a site, the power consumption, heat load, weight, and other items must be updated in system diagrams.
Program- and project-management tasks are very difficult, given the internal and external influences that can change a project's timing and budget. Good planning techniques — for example, risk awareness and mitigation planning, as well as "what if" situational awareness — let managers identify and plan for change. Future planning for new technologies gives managers extra capacity that mitigates risks in the present and helps plan for the future.
Ira Wiesenfeld, P.E., has been involved with commercial radio systems since 1966, and has experience with land-mobile-radio, broadcast, paging and military communications systems. He holds an FCC general radiotelephone operator's license, Extra Class amateur license, and is the author of Wiring for Wireless Sites, as well as many articles in various magazines. Wiesenfeld can be reached at [email protected].
Robert C. Shapiro, P.E., is a consulting engineer who has been in land mobile radio engineering — including public-safety and transportation communications — since 1984. He serves on the TIA TR8 committee (TSB-88) as vice chair and is a senior member of the IEEE. He can be reached at [email protected].