RF101 - The Antenna Path - More than the Antenna
The point where the rubber meets the road in wireless networks is the antenna. The only thing is the before we hit the antenna, we have the entire antenna path which consists of various opportunities for error and issues. From external interference, to Passive Intermod (PIM), to actual faults in the path. Once the issue has been identified in the antenna path itself and not the external RF environment, there is the potential for a large variety of antenna path component combinations including fiber, coax cables, duplexers, diplexers, connectors, antennas, RETs, TMA. The ability for RF and operations teams to identify and resolve these issues is critical to network success.
RAN engineers typically look at two things when there is a field RF problem. The radio and the antenna. The radio is typically simple enough to look at and test through the OSS verifying certain measurements and alarms. The antenna actually refers to the antenna path. All that can be done remotely is determine there is something wrong with the entire antenna path or in MIMO environments, one of the branches of the antenna path. These coming from VSWR measurements/alarms, UL/DL path balances, and branch Tx loss measurements. This leaves for a typical communications gap between operations and engineering on where the issue is and how to fix it. The key to success is dedicated operations teams with the flexibility to troubleshoot (not just close tickets) and engineering teams that can communicate the proper symptoms and best ways to troubleshoot.
However, even once an potential issue is identified, the other part of the operational equation enters. That being the $$. If the KPIs on a cell site by normal standards look good (Drops, Traffic, Accessibility), then issue could be said is there the value to fixing the site. With MIMO being the key to high speed data, having all antenna path branches at optimal performance is critical, but how does this show up in today's current network KPIs? Another way to see the issues is that a cell performing well, could it be performing even better? In the past, many large scale antenna swap-out and upgrade projects in networks typically show improvement. It is estimated that a minimum of 25% of the improvement comes just from resolving long standing issues in the jumpers, connectors, and cables being cleaned up rather than just the antenna pattern changes.
Engineers should build the fundamental understanding of the antenna path and how each part may affect performance. It is with this understand, network teams will quickly identify and resolve issues keeping customers satisfied with the network quality.
CommScope has created a free E-Book on all types of variations in the RF Path that builds a solid foundation for most of today's RAN antenna path scenarios. It can be found at:
http://www.commscoperfpath-ebook.com/rfpath/understanding#pg1 (Required to provide an email, but nothing more)
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