March 23, 2021
As cellular and public safety networks continue to further crowd the available spectrum, network planning and optimization takes on greater significance. Whether mobile operators use their own teams or hire prime contractors – aka Turf Vendors – to install base stations, close out reports are necessary before the site goes live. Using app-based processes can save time and money when conducting this necessary and important step that helps ensure new base stations are installed within compliance of the Method of Procedure (MoP).
Many new base stations utilize fiber optics from the tower base to the remote radio head (RRH) atop the tower. Short RF cables connect the RRH to the antennas. Installation teams arrive on site and conduct line sweeps on the RF cable feeds and properly align the antennas based upon MoP specifications. This is done to ensure key performance indicators (KPIs) will be met. In today’s post, we will focus on conducting line sweeps and including them in a close out report.
Importance of Close Out Reports
Before we delve into conducting and documenting line sweeps, let’s detail the importance of close out reports. Base station installation crews must create and submit documentation before the site goes live, so improper reporting will delay the site becoming operational. A Turf Vendor contracted to do the installation is not compensated until the reports are submitted and approved.
Why are they so important? Because they verify that the base station has been installed correctly and is operating according to specification. Measurement results for the RF cables and antennas, as well as correct alignment of the antenna are contained in the report.
Creating close out reports has typically been wrought with frustration and issues. For one, they are time-consuming. Secondly, they are traditionally generated only after the crew has left the site.
App-based Reporting On-site
Fortunately, a new application that runs on Android devices provides a highly automated report generator. With the app, technicians send results data and traces directly to the network operator for approval while at the site. Measurement errors can be quickly identified by the operator, so the technician can repeat the measurement(s) and resend the report for approval. Truck rolls and other associated expenses of site installation and maintenance are reduced, as a result.
The application interfaces with a wide range of Anritsu Site Master™ cable and antenna analyzers and the Multiwave antenna alignment tools (figure 1). A single consolidated report for both sets of measurements is created, shortening the time to produce the report and expediting the site approval.
RF Cable and Antenna Line Sweep Basics
One critical element of the close out report is line sweep measurements. Towers typically have at least six, and perhaps 30 or more antenna systems. Each needs to be checked for RF faults. A MoP outlines the verification process and often requires six or seven sweeps per cable. That means each tower can have 36 to 180+ line sweep measurements. Simplifying report generation can save tremendous time for this reason alone.
Technicians need to sweep antenna systems during installation to verify performance of the RF cable and antenna system, and to locate any potential faults within the signal path. Line feed and antenna system faults have a variety of causes. Damaged or pinched cables, corroded connectors, or antennas are common issues. Acts of nature, such as lightning strikes and water penetration into cables, can also impact performance. Bullet holes and other acts of vandalism can damage cable systems. In all these cases, the result is poor overall system coverage and eventually dropped calls.
Another reason to conduct line sweeps is to ensure the proper components are used. For all these reasons, sweeping the cables and antennas and preparing the line sweep reports are essential parts of the overall installation process. Most technicians rely on the Site Master series for these measurements, as they are the de facto industry standard.
Antenna System Measurements
The handheld field analyzers support the measurements technicians typically are required to conduct at the base station site. Each antenna system mounted during construction is verified via the following measurements:
- Antenna Return Loss – This will easily identify an incorrect or defective antenna. It is typically measured before installing on the tower, as well as after installation.
- Cable Insertion Loss – This can identify incorrect cable(s) and/or excessive loss usually caused by water absorption or loose/bad connectors.
- Cable Distance-to-Fault (DTF) with a 50 Ohm load on the far end – A troubleshooting measurement, it locates faults within the coaxial transmission line and various connectors/components.
- Cable DTF with a “Short” on the far end – A test to ensure proper cable length.
- Antenna and Cable System Return Loss – Typically a Pass/Fail test with the limit specified by mobile operator.
- Antenna and Cable system DTF – Often considered the “birth certificate” of the site, it is used as a reference when troubleshooting faults once the site is live.
If the antenna points in the wrong direction, the network will degrade. The three parameters of antenna alignment are:
- Azimuth is a geographic direction defined from 0° to 360° with respect to true North
- Tilt is an angular measurement of the antenna in the up and down direction, sometimes referred as uptilt or downtilt
- Roll is an angular measurement of the antenna in the side-to-side direction, sometimes referred to as plumb
Close Out Report Creation
All line sweep and antenna alignment measurements are transferred into the smart phone memory. With the app, all the results can be consolidated into a single report by easily transferring the data files (.dat, .vna, .pim) to the app, where they are saved to the site directory. Technicians simply choose those files to include and create a report. Figure 2 shows a sample report page based on a VSWR measurement.
All selected files can be previewed and consolidated into a single PDF and emailed directly from the mobile device. The report generated is suitable for submission to site management and can be easily emailed from the site to the head office.
For field technicians who need to create close out reports quickly and reliably after installing new antenna systems in the field, the Smart Aligner smartphone application offers a fast and reliable solution from the market leaders. To learn more, download this free app note.
