With the mad rush to deploy 4G LTE networks, carriers might not have thought of the repercussions this technology could have on the existing equipment. While co-locating has often been a relief for tower companies looking to enhance service in the market without constructing a brand new tower, it might be causing problems. Michael LeClair of Radio World explained that 4G equipment and FM radio equipment aren’t working well together, and the cellular companies are complaining that their signals are experiencing interference. For the past few years, cellular and radio equipment have existed on the same towers in harmony. “That’s why it’s a bit disconcerting to hear about cell companies suddenly telling FM stations they were causing destructive interference to the latest 4G technology, and even requesting these stations be issued a Notice of Violation and fines. Often the cell company directly informs the pre-existing FM station of the interference using official language, while implying the entire fault lies with improper operation by the FM owner. But it’s not entirely clear that it’s a case that could stand up legally under the current rules,” LeClair explains. David Horn of the LBA Group wrote in the company’s blog about how carriers using the 700 MHz LTE uplinks are being impacted with unexpected radio frequency interference. FM equipment isn’t the only technology interfering with LTE though. In Los Angeles, California, the FCC cited a company whose fluorescent lighting fixtures were interfering with a nearby tower.
“When it comes to interference, FCC regulations shift the burden of responsibility to the end users of ISM equipment. Few building managers, electricians and maintenance people are even aware of RF interference, much less the potential for seemingly benign devices to cause it. Faced with a cost of thousands of dollars, in some cases, to exchange ballasts it is understandable that some interfering outfits would choose to do nothing, seeing no apparent harm. Imagine their consternation at receiving a federal fine of $16,000 just for having the lights on,” Horn explains. “ISM interference can wreak havoc on not only voice communications in a wireless network, but more importantly the massive amounts of data flowing through new LTE networks. The lower 700 MHz, and soon to come 600 MHz frequencies are particularly vulnerable to harmonic-related device radiations. However, carriers operating LTE networks at 700 MHz are licensed to do so by the FCC and are widely protected from both intentional and unintentional interference. Of course, ballast interference is only one type to which 4G LTE systems are susceptible. FM station harmonic emissions, stray LED RF radiation, CATV signals, and even rusty bolts can generate enough interference on 4G LTE uplinks to kill data throughput. As the data load on these systems increases, many more cases of unintentional, and sometimes bizarre, RF interference are sure to arise.”