Base Station Transmits

Effects of Various ‘Sight Screen’ Materials on 5G FR2 Transmission

April 17, 2020

As the first generation of 5G networks are being rolled out, an issue that can’t be overlooked by mobile carriers and installers is the effect of “sight screens” on transmission quality. For years, building landlords in urban areas have required operators to conceal antennas and transmission equipment used in rooftop installations so they are not seen at street level. While these screens caused minimal signal loss in LTE networks, they will have a more profound effect on 5G signals.

Another factor highlighting the importance of selecting the proper screens is that 5G radio deployments will be on more than rooftops. Street lampposts and dedicated poles will be installed in cities and other congested areas. This means the materials used for the sight screens must be properly selected or the 5G radios will transmit less efficiently at a higher power or there will be reduced coverage from each radio. 

Propagation loss due to sight screens will occur in the sub-6 GHz Frequency Range 1 (FR1) band  operating at 3.5 GHz. It is an even greater consideration with Frequency Range (FR2) transmissions since they operate at 28 GHz and 39 GHz. Because FR2 signals travel in the millimeter wave (mmWave) bands, the distance between base stations or small cells needs to be very short to provide reliable wide area coverage. For that reason, 5G FR2 radios in some American urban centers are being deployed every 100 meters. Higher frequencies are also more susceptible to outside factors such as screens.

Figure 1 shows a typical 5G FR2 radio rooftop installation. The radio is barely visible through the cut out in the sight screen being erected to hide the radios from street level. Careful selection of the materials used for this type of environment is essential to ensure optimum network performance. Materials should be accurately characterized for their RF attenuation properties to ensure networks meet key performance indicators (KPIs).

Figure 1: Sight screen installation.

Conducting Materials Measurements

One test tool to conduct these necessary measurements is the Anritsu Microwave Site Master S820E handheld cable and antenna analyzer configured with a waveguide horn antenna. Field engineers and technicians can use this field solution to conduct quantitative insertion loss measurements on a wide range of materials. Based on these results, network planners can model 5G network coverage and select materials that provide the best compromise between durability and aesthetics without sacrificing network coverage and user experience.

The S820E was used to measure the impact common office building materials will have on 5G signals. Results of the tests taken on these materials – drywall, wood paneling, regular and low-E thermopane windows, fiberglass, and office cubicle partition – can be seen in table 1.

Material Tested	Drywall	Wood Panel (3/4")	Regular Thermopane	Low E Thermopane	Fiberglass Insulation (8")	Office Cubicle Partition
Average Loss (dB)	~3	~4	~3	~43	<0.5	>60

Table 1: Propagation loss of 5G signals based upon common building material.

Let’s look at each measurement in a bit more detail:

Drywall and Wood Panel

Measurement taken with the Site Master antenna analyzer revealed that drywall and wood panels should pose no significant issues with respect to signal loss. Based on the measurement results, FR2 signals are able to propagate well through these materials.

Thermopane Glass

FR2 signals are able to propagate through a standard thermopane window (Figure 2) with little loss. The same can’t be said for the low-E (low-emissivity) thermopane window (Figure 3), which acts as a barrier for the FR2 signals. Low-E glass has a special microscopically thin reflective coating that minimizes the amount of infrared and ultraviolet light – and 5G signals – that enter a building. FR2 signals are not able to propagate through these types of windows.

Figure 2: Standard thermopane window.

Figure 3: Low-E thermopane window.

This will present some significant challenges, since many newer buildings utilize low-E thermopane windows due to their excellent overall energy efficiency. With considerably lower penetration of FR2 signal levels inside the building from 5G gNB external base stations, users may experience dropped calls, an inability to connect to a network, and very slow data speeds. In other words, all of the desired benefits provided by the wide bandwidth available in the FR2 bands will be negated by the high losses caused by the low-E type windows. 

There is also the issue of rain. Measurements indicated that a regular thermopane window created signal loss of ~3 dB. That same window’s loss increased significantly to ~17 dB with water sheeting. This could easily occur when a strong rainstorm with high winds forces the rain to fall angularly onto the glass.

Fiberglass and Office Cubical Partition

Test results indicated that commonly used fiberglass insulation poses no threat to FR2 signals. In contrast, office wall cubicle material is absolutely catastrophic to the FR2 signals, as shown in figure 4. This particular office cubical material would pose significant problems for indoor FR2 signal coverage.

Figure 4: Office cubical partition.

Manufacturers of office cubicle materials will need to investigate using different materials to obtain the desired structural strength of the cubicle partitions while minimizing FR2 propagation loss. Alternative materials will need to be considered with a focus on ensuring negligible propagation losses at FR2 frequency bands.

Canvas Fabric

Dry canvas measurement results were <0.5 dB, making it appear as though canvas fabric is a good choice for concealing antennas and/or 5G base stations. It is easy to work with, durable, and very flexible. Not everything is as it appears, however. If not properly treated to prevent moisture absorption, the canvas material becomes one of the worst possible choices! Its loss increases dramatically once it has absorbed moisture. One layer of wet canvas had ~10 dB of loss (Figures 5a and 5b).

Figure 5a: Layer of dry canvas.

Figure 5b: Layer of wet canvas.

Consider this. If an antenna system is concealed using very thick and rugged canvas that is equivalent to 4 layers of the sample tested, the insertion loss will be <0.5 dB when dry. After the canvas absorbs moisture, the insertion loss increases to ~40 dB, which makes it likely that a connection can be lost. Dry vs. wet open cell foam exhibited similar characteristics compared with the dry vs. wet canvas. You can watch a video of this effect (and others) that was taken by the testing crew.

An application note, Measuring Path Loss of 5G FR2 Transmissions Through Common Materials Found in the Signal Path, has been published and can be downloaded from the Anritsu website. It provides more insight into selecting proper sight screen materials.

Proper Test Tools Simplify Sports Venue DAS Install

July 12, 2016

Distributed Antenna Systems (DAS) pose many challenges, including the fact they are usually installed in havens for interference. However, as the case study below shows, using the proper test solutions, such as handheld cable and antenna analyzers, passive intermodulation analyzers and a cloud-based software solution, can help successfully deploy DAS networks – in this case ensuring operation while reducing test time by 70%.

Project Situation

A large state university on the east coast was upgrading the wireless network in its basketball arena to provide spectators with improved venue coverage/capacity, particularly for high-bandwidth services. Communication Technology Services (CTS), the contractor hired by Crown Castle for the project, needed test tools that could simplify the complex challenge of collecting thousands of traces to verify the DAS installations in a very tight time window.

The 8,000-seat indoor multi-purpose arena posed a set of obstacles that ranged from building architecture to environmental conditions. CTS Project Manager Legion Marks and his team had only a few weeks to install the DAS network throughout the basketball facility. To verify the network, more than 2,000 traces had to be done on the various passive branches that stretched across the complex. Some venues have 10,000 to 15,000 traces required. All of the traces had to be reviewed and approved before the project could be closed out. In the past, there was a time lag in compiling and presenting results to the Crown Castle RF Engineering team, which could result in project delays. They needed a more automated testing solution to compile and upload data for quicker reviews in order to track the cycle time and ensure data integrity.

“With the emergence of LTE technology, DAS complexity and density has greatly increased along with demand for line sweep detail. It is a daunting task to manage the large amount of traces during a project. The DAS industry as a whole needs a powerful trace management tool. Thankfully, we had SkyBridge Tools,” explained Marks.

Test Solutions Save Time Marks, experienced in engineer, furnish, and install (EF&I) management, selected a suite of Anritsu field solutions. His team used Site Master™ “E” and “L” series cable and antenna analyzers, as well as the PIM Master™ MW82119B. SkyBridge Tools™ Test Manager cloud-based trace management tool was used with all the instruments to simplify the testing processes associated with the DAS installation. It provided a number of benefits, including:

Automated Test Scripts – The easyTest™ feature of SkyBridge Tools makes it simple to create a set of instrument control scripts based on Crown Castle’s MOP (Method of Procedure). This allowed the CTS team to conduct measurements by pressing a single button per test.

Reporting – Skybridge Tools offers a one-click solution for reporting.

Marks could track the progress of the project by simply logging into his account, eliminating the tedious, time-consuming and error-prone practice of manually compiling data and sending a periodic report. Marks explained, “Skybridge Tools eliminated many of the headaches with manipulating large amounts of trace data, including pass/fail review, naming convention mistakes, and batch processing. It even allowed me to export the data into a tabulated form, which reduces manual data entry for closeout documentation.”

All of this made for a seamless process. Team members would upload completed traces to SkyBridge Tools. Once Marks approved them, each batch was made available to Crown Castle RF engineers through Skybridge Tools for their review. The result was a very efficient method to verify the installation of the entire DAS network, allowing Crown Castle to ensure that all the test criteria has been met with all the corrections in place, before approving the project.

The Anritsu staff went above and beyond when it came to support, according to Marks. Hands-on training was provided to CTS and it was completed in only three hours so the team could begin gathering traces the same day.

Results

CTS was able to meet the project timeline in large part because SkyBridge Tools created a highly efficient method for storing traces that shaved at least 70% off the job timeline, according to Marks. Crown Castle was able to review and approve the project more quickly, ultimately allowing the project to be closed out faster and for payment to be expedited.

“Skybridge Tools takes trace management to the next level. I see a huge value in it for my company, both on cost savings and customer service. After implementing this process, I don’t see any other way to collect large amounts of trace data,” said Marks.

SkyBridge Tools helped CTS close out the sports venue project more efficiently, get paid faster and move on to the next project. To learn more about SkyBridge Tools can to help your DAS installations, visit a comprehensive page on the cloud-based solution.

Cloud-based Test Tools Simplify and Expedite DAS Installation Process

June 28, 2016

Every mobile communications report published has a recurring theme – mobile date usage is skyrocketing to new heights. People rely on their mobile devices (smartphones, tablets, etc.) more than desktop and laptop computers in everything they do and wherever they are. In fact, approximately 80% of mobile usage happens indoors and not just from the comfort of a living room couch via Wi-Fi. Consumers use their smartphones while shopping in brick and mortar stores (84% of them according to Google) and another study found that three quarters of workers would consider leaving their current mobile operator to get better coverage in their office.

All of this makes it imperative for providers (and landlords) to ensure coverage in malls, office buildings and other venues. Not only will it ensure mobile data usage for potentially increased revenue, it will help reduce churn because consumers have high service quality expectations when using their mobile devices indoors.

There is just one problem – indoor coverage is not simple. “Outside-in” signal loss can be up to 7 dB due to windows, and reach 10 dB for brick or 12 dB for concrete walls. Metal wall framing may cause a loss of up to 10 dB, while concrete floors can result in losses approaching 30 dB, according to one analyst group. That is why there has been tremendous growth in the deployment of In-building Wireless (IBW) systems, specifically Distributed Antenna Systems (DAS).

Despite the challenges associated with DAS, the aforementioned market conditions provide compelling business reasons for operators to deploy indoor networks to accommodate their customers. Providers in North America and Asia-Pacific have particularly taken an interest, evident by the statistics in figure 1.

Figure 1

Understanding DAS

Hybrid and/or passive DAS has become a popular architecture for multi-operator, multi-NEM, multi-technology applications because it is able to accept RF inputs from a variety of signal sources, making the DAS network equipment manufacturer as well as technology (2G, 3G, 4G) neutral. When possible, DAS antennas should be placed in locations with a clear view of the environment they are serving rather than near metal objects such as light fixtures, ceiling tile frames and metal HVAC ductwork. Placement close to these objects can generate high levels of passive intermodulation (PIM), even with transmit power levels as low as 20 dBm (100 mW).

Studies conducted by Anritsu indicate that external PIM sources close to IBW antennas are more likely to impact performance at low frequencies, such as 700 MHz, 850 MHz, and 900 MHz. Best practice when deploying low-frequency band systems is to perform a low power PIM test at each candidate antenna location prior to final installation. Internally generated PIM is worst at the higher frequencies, so in this case a PIM test at one of the higher bands, such as 2100 MHz or 2600 MHz, is best practice. Eliminating PIM in DAS is discussed on our PIM Source blog.

A DAS may require 1,000 to 15,000 traces, photos, and other deliverables to show that the installation meets performance standards. This can be as much as 100x more than what is required when installing a typical tower-based antenna system. When you consider each of these deliverables needs to be inspected, renamed, and perhaps have the markers and limit lines set and judged, the task can become quite lengthy and costly if the traditional manual inspection process is used.

Given the complexity and myriad technologies used in DAS, as well as the technical aptitude of some technicians, there is a definite need for simplified testing processes to the DAS installation workflow. Fortunately, there are now cloud-based tools to ensure time savings for operators and allow contractors to more quickly close out jobs, get paid and move on to the next project. One such solution is SkyBridge Tools™ from Anritsu, which enables reliable and quick creation of test plans, fast and accurate testing, and assists in report creation.

Test Plan

A sound test plan is the best first step in simplifying the test process. Data can be imported from iBwave designer, Excel, and operator-supplied test criteria with the assistance of a wizard to create detailed Test Plans such as the one shown in figure 2. This documentation enables test sequencing, job progress tracking, trace judgement, and report generation.

Figure 2

Test Sequencing

After the test plan is created, pressing one button will create instrument control scripts for that specific plan. Necessary tests, proper instrument setups, limit lines, and accurate file names for traces are included. These scripts can then be run on certain Anritsu field instruments, including Site Master™, BTS Master™, and PIM Master™ handheld analyzers, greatly reducing technician workload. Failures are often visible while the cable is still connected to the instrument. Missing or duplicated tests, misconfigured setups, and misnamed traces are eliminated through this tool.

Reporting

A key element to the DAS testing process is the reporting mechanism to verify the tests were conducted properly and the results sound. Traditional PDF or zipped reports are standard formats but having a CSV file with one row per test is also sometimes necessary and advantageous. Automated reports in a variety of formats forever eliminates the tedious and inconsistent processes used in the past.

There is much more to learn about IBW systems and the various system architectures, such as DAS, Distributed Radio Systems (DRS) and Distributed Small Cells (DSC), as well as how to test each. You can download an Understanding IBW white paper to gain more information.

How Cloud-based Tools Can Simplify DAS Verification

December 10, 2015

As anyone who spends time in the field climbing towers knows, the need for documentation of antenna systems is increasing. A typical tower-based antenna system may require 50-150 measurements, traces, and photos to show that the installation meets quality standards. That is nothing compared to a Distributed Antenna System (DAS), which might need 1,000-15,000 traces, photos, and other deliverables to verify the installation is to specification. Each deliverable needs to be inspected, renamed, and in some cases have the markers and limit lines set and judged.

Typically, all of this has been performed via manual inspection procedures. While that was (barely) acceptable for tower environments, it does not scale well for the much larger DAS systems. For tower inspection professionals, verifying the completion of tests and documenting said measurements are required to get paid. Therefore, developing a process that allows them to close out jobs, get paid, and move on to the next job more efficiently is imperative to successful operations.

Tools for Greater Efficiency

Cloud-based trace management tools, such as SkyBridge Tools™ (figure 1), have been designed to simplify this growingly complex environment. Contractors or owner/operators can use these online tools to show that their work is complete so they can be paid faster. DAS system installers will find these tools particularly beneficial, as they automate the collection and validation of thousands of traces. It creates a place for each and every deliverable, and shows progress towards meeting those requirements. These virtual slots, so to speak, can be designated for line sweep traces, OTDR traces, PIM traces, site photos, as well as any required construction documents.

Figure 1

Another benefit of cloud-based tools is that site technicians have access to real-time information. They also make uploading test data easier. Through these systems, confusion is eliminated and project management involvement reduced because pass/fail results are very clear and easy to read.

As mentioned earlier, a cloud-based tool can be particularly effective in DAS installations. Here are three steps to take that will simplify this complex workflow.

1. Create Test Plan – Cloud-based tools can gather input from custom software, Excel or similar spreadsheets, and customer-supplied test criteria to efficiently build a comprehensive test plan that enables test sequencing, job progress tracking, trace judgement, and report generation.
2. Test Sequencing – A set of instrument control scripts for the test plan can be created by simply pressing a single button on a compatible field analyzer (figure 2). Necessary tests, precise instrument setups, limit lines, and accurate file names for the resulting traces are included in the scripts that can run on the test instrument to greatly reduce workload. Technicians will be able to see failures immediately while the cable is still connected to the instrument. They no longer have to worry about missing or duplicated tests, misconfigured setups, or misnamed traces, thereby improving efficiently.
3. Reporting – There are several choices for reporting. Traditional PDF or zipped reports are available. Reporting is also available in a CSV format, with one row per test. Each row contains the test name, the criteria, a significant number for the measurement, a pass/fail indication, and a PDF of the trace. These reports automate what has been a tedious process in past.

Figure 2

Cloud-based tools can offer other benefits in DAS and tower-based antenna systems. To see how these solutions integrate with test instruments and can simplify closing out system testing for faster payment, download this application brief on cloud-based tools.