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RCR Wireless hosted a Local Speaker Series on November 9 in Dallas under the title “Mobile Broadband: Innovation and Opportunity.” I was one of three Andrew Solutions folks on a panel that fielded a variety of questions about the status of 3.5G and 4G network roll-outs, the role and requirements of in-building systems, and the need for more green, energy-efficient network solutions. But one of my main takeaways was the continued concern about PIM interference in next generation networks.
If you’re not familiar, PIM is passive intermodulation distortion, which is a type of wireless interference that can degrade signal quality at a cell site. PIM usually results from wireless signals mixing together; if they are in the same frequency as the desired wireless signal, PIM interference causes disruption. PIM is especially of concern in next generation networks because it is easier to disrupt data signals to a point where subscribers experience poor quality. That’s why PIM continues to be a main issue when it comes to quality of service and network optimization.
So how do you prevent PIM?
Well, there’s no one trick, since all sources of PIM in the entire cell site combine to yield the total PIM distortion for the system. Some keys to limiting PIM’s impact, though, include:
• Start with quality products ideally envisioned as a complete system, where connections will be clean, properly torqued, properly attached, and resistant to material degradation.
• Make sure products are installed correctly. Probably the most significant causes of PIM are due to improperly installed equipment. Putting together a clear RF Path requires definite know-how and experience. Make sure you are using qualified, well-trained installers.
• Remember that testing PIM levels is challenging because readings are sensitive to test equipment and other surroundings that can increase PIM, resulting in false failures. If you aren’t familiar with PIM testing requirements, you might want to check out the Andrew Institute’s new PIM class.
Obviously this is a pretty cursory overview of a complicated and reasonably concerning topic. PIM has been on Andrew Solutions’ radar for awhile, but there’s always more to be learned. As my experience at the recent RCR event attests, PIM is still on a lot of people’s minds.
What’s on your mind regarding PIM and the networks of today and tomorrow?