Base Station Transmits

Innovative Software Recognized by Microsoft Corp. Improves Tower and DAS Testing

November 17, 2015

Innovation is a term often thrown into conversations about wireless technology. Its definition can vary from person to person but most of the time it relates to how standards and technologies are implemented by operators and used by consumers. Innovation also pertains to test solutions that ensure the proper implementation of new technologies by operators so consumers enjoy high-bandwidth services that a few years ago seemed unattainable.

A good example of how innovation is used to push test solutions ahead is software such as SkyBridge Tools™, a cloud-based trace management tool designed to simplify the lives of everyone involved in tower or DAS testing by improving the way results are communicated, validated, and delivered. In fact, it is so pioneering that Anritsu has received a 2015 CXO NEXT Innovation Award from Microsoft Corp. for SkyBridge Tools.

Anritsu received the award during the CXO NEXT Summit in Redmond, Washington. SkyBridge Tools was placed in the Reinventing Productivity and Business Processes category. The awards were created to recognize visionary leaders who led transformational innovation using Microsoft solutions to realize the benefits — reinventing productivity and business processes, building an intelligent cloud platform, creating more personal computing, and empowering finance and marketing.

“In this ever-shifting, mobile-first, cloud-first world, organizations must constantly evaluate how they operate, empowering employees to innovate and move the business forward,” said Ron Markezich, Corporate Vice President, U.S. Enterprise & Partner Group, Microsoft Corp. “The winners of this year’s CXO NEXT Innovation Awards met this challenge with enthusiasm, using technology to improve operations and better connect with their customers.”

Anritsu’s SkyBridge Tools is a Microsoft Azure cloud-based data manager for 4G fiber, cable, and antenna installations focused on C-RAN and DAS systems that addresses three key issues. It has unprecedented cloud-based data mobility that eliminates the need to move large amounts of data over ad-hoc data transfer systems. Secondly, it provides processing and pass/fail/present/absent judgements of deliverables, such as measurements, photos, and documents, so field personnel know at upload time which measurements pass and how many documents are missing. This allows any needed corrective action to be taken before they leave the site. Finally, SkyBridge Tools is user-configurable from a web- or CSV-based interface, providing the flexibility a job judgement tool needs in today’s fast-paced environment.

Gerald Ostheimer, CEO Network and Infrastructure Business Enablement Business Unit, Anritsu Company, commented on earning the distinction. “By delivering global network monitoring systems that collate data from all network nodes to a common cloud location, global data analysis becomes possible. This reveals unparalleled amounts of information on network performance and efficiently guides the user to potential optimization paths. Microsoft Azure is the trusted platform that allows SkyBridge Tools to make our customers, and Anritsu, more successful,” he said.

To learn more about the awards, visit the Microsoft Marketing blog. You can also learn more about SkyBridge Tools and its benefits by downloading a free In-building Wireless/DAS application note.

Methods to Maintain Cable and Antenna Systems for Healthy Network Performance

June 29, 2015

Cable and antenna systems are the backbone of base stations, and field technicians spend a good part of their day ensuring they are healthy. Keeping these systems in shape means the network as a whole runs better. Uptime is increased, call drops go down, data rates go up, and operators are happier. In this post, we will outline some standard tests that you can make with a handheld base station analyzer for the well-being of wireless networks.

Sweeps

Maintenance sweeps can catch faults early, which will increase network uptime, reduce dropped calls, and allow consistently higher data rates. Since every cable has a different sweep signature, it can be difficult to notice changes. That is why it is important to use a reference trace acquired during the commissioning sweeps, so you can see slight changes before they weaken network performance. Once a problem is spotted, it’s time to troubleshoot it.

Troubleshooting sweeps are inherently different from maintenance or commissioning sweeps, since they require a flexible use of the instrument, calibrations, and settings to accurately locate the fault. Using a handheld solution such as the BTS Master™, which has FlexCal™, allows you to change frequency range without re-calibrating.

When looking for faults, one thing to realize is that most are caused by loose, corroded, or poorly installed connectors. The next most common causes of problems are associated with the cable, either water in the cable, loose weather wrap, pinched cables, or poorly installed ground kits. At some sites, the issue can be bullet holes and even nails in the cable!

Return Loss/VSWR

Return Loss and VSWR are two different ways to measure reflections. Return Loss is a logarithmic scale while VSWR is linear; the choice as to which to use is yours or based on company requirements. There is a basic conversion formula to maintain consistency in measurements between the methods:

Limit lines, such as those in figure 1, can be created on select handheld analyzers, such as the Master series from Anritsu, and can be transferred from one instrument to another via a USB stick or compact flash memory. Not only does this make looking for faults straightforward it helps ensure consistency. Return Loss, with an antenna on the far end, should be between 15 dB to 25 dB. For a line with a load on the far end, the value should be between 30 dB and 40 dB.

Figure 1

Distance to Fault (DTF)

Once faults have been identified by Return Loss or VSWR measurements, DTF is the preferred means to locate them. Trace comparisons are often used for diagnostics because small changes in cables will have large effects on the DTF trace. Because of this, it is accepted practice to take reference sweeps of each cable at commissioning for later comparison. Changes are often more significant than actual values, however typical values with a good setup are:

Open or Short         0 to 5 dB

Antenna                     Better than 16 dB

Connectors              Better than 25 dB

Propagation velocity (PV or Vp) directly affects distance accuracy and must be set either manually or by entering a cable type. Cable Loss also needs to be set precisely using the same method. False cable loss values can mask Return Loss or VSWR problems, making your job more difficult.

The frequency range for DTF sweeps should stay within the load’s bandwidth. If an antenna is used for the load, any portion of the DTF sweep that goes outside the pass band is mostly reflected, reducing the accuracy of the vertical axis Return Loss or VSWR measurements.

A wider frequency range improves distance resolution and lowers the maximum measureable distance. Always remember if an antenna is in place at the other end of the cable, the DTF frequency range should be restricted to the antenna’s pass band.

Antenna Isolation

Poor base station antenna isolation allows RF signals from one base station antenna to leak to another. If the leak is strong enough, BTS signal quality can be compromised. This problem can affect more than radios with poor isolation. Failures mean that the sector is prone to excessive intermodulation distortion, resulting in lower signal quality, increased dropped calls, and possibly interference with other radio services.

If you maintain cellular systems, base station antenna isolation limits typically should be lower than -50 dB to -60 dB, although different situations require various limit numbers. Repeaters with insufficient isolation between the two antennas are prone to oscillations, creating interference that can harm communications over a wide area. Repeaters are tested in much the same way as base stations but they require better isolation numbers. Refer to your repeater installation instructions for specific guidelines.

Tower Mounted Amplifiers (TMAs)

A base station’s receive coverage can be compromised by a TMA with low gain or distortion, is in bypass mode, is improperly installed, or is completely open. You can test a TMA directly on the tower, which verifies both the TMA and its installation. This saves time and eliminates the expense associated with a tower crew taking the TMA down.

TMA tower testing should be done with two-port analyzers that have:

• A built-in bias tee with voltage selection to supply power to the TMA
• High RF power mode (0 dBm) for tower testing
• Lower RF power mode (-35 dBm) for direct gain measurements on the ground
• A current draw display, to check for excessive TMA current drain

TMA gain can be measured using the two-port insertion loss measurement. The first step is to measure the TMA without power supplied from the bias tee followed by a measurement with the bias switched on. The difference between the two readings is the TMA gain. The TMA must have a power fail bypass mode for this measurement. When checking TMA gain, save the two traces so you can easily use delta markers to measure the difference. It also makes it simple to check for in-band flatness, pass-band width, and the slope of the TMA filters.

We have only scratched the surface on troubleshooting base station cables and antennas. If you are interested in learning more, download a free white paper entitled Understanding Cable and Antenna Analysis.