There are obvious reasons for putting the radio head at the top of the tower. Number one is performance. Cut out the long run of feeder cable, and signal loss is reduced and overall gain is improved. So why would anyone hesitate to deploy remote radio heads atop a tower in an LTE buildout?
“It is the most expensive place to make an error, and it is also the most likely place to make an error,” Sorrells said. “You can imagine what tower technicians must feel at the top of a tower in the wind. If you can’t even hear your co-workers, there is a high probability that you will get it wrong.” One typical error is when a technician introduces passive intermodulation into the radio while performing the connections, he added.
To reduce mistakes made on the tower, CommScope is standardizing and simplifying remote radio unit (RRU) installation through its SiteRise line of fiber to the antenna (FTTA) turnkey solutions. The Andrew SiteRise was launched last year offering pre-assembly and pre-testing of all RF equipment prior to hoisting up the tower. The product took all the connection work from the top of the tower and placed it at ground level. But simplifying initial deployment isn’t enough, Sorrell said.
Initial deployment is not the only time technicians will be on the tower making connections during the course of a carrier’s deployment, Sorrells said. Because of the typical radio failure rate, technology upgrades and frequency additions, technicians will climb the tower and do maintenance on a regular basis.
“Even with the Andrew SiteRise, the radio is attached to the antenna with an RF jumper assembly and RF connectors, which works great the first time, but in the case of maintenance, a climber must go up the tower, undo the jumpers, put in a new radio, redo the jumpers and re-certify the site,” Sorrells said. “We know from our experience that, most times, passive intermod or a noise issue is inserted into the system through the connections.”
In order to simplify the interface between the base station antenna and the RRU, CommScope will announce development of the Andrew SiteRise Standard Interface at the Mobile World Congress in Barcelona, Spain, later this month.
The OEM is replacing the jumper cables and standard connectors with a blind mate connector, which minimizes the opportunity for a passive intermodulation product to be produced by that connection. A kit was developed that will fit around any radio and attach the radio to a guide or rail system behind the antenna. The kit/railing system and standard interface connector make the radio a plug-and-play component, Sorrells said.
“We think that will change the idea about how remote radio heads get implemented at the top of towers, making it simpler to do, more flexible, and easier to maintain and update,” Sorrells said.
Sorrells hopes the industry will accept the interface as an open standard and is willing to share it with other antenna suppliers and radio OEMs.