Solid Signals

Maintaining Public Safety Network Operation During Natural Disasters and Manmade Influences

October 20, 2021

Ensuring network connectivity so first responders can perform their mission-critical duties is never an easy task. Often, police, fire, and EMS are deployed to emergency situations that, by their very nature, can inhibit communication. One such scenario is during natural disasters. A new report sheds some light on the impact an earthquake can have on commercial and private networks.

The HayWired Earthquake Scenario—Societal Consequences is the third volume of U.S. Geological Survey (USGS) Scientific Investigations Report 2017–5013. Recently released, the report describes the HayWired scenario developed by USGS and its partners. The scenario is a hypothetical yet scientifically realistic earthquake sequence that is being used to better understand hazards for the San Francisco Bay region during and after a magnitude-7 earthquake (mainshock) on the Hayward Fault in California and its aftershocks.

One chapter of the report is devoted to observations of earthquake damage that could be realized on telecommunications and information communication technology. It covers every aspect of that ecosystem, including central offices, copper and fiber cables, base stations, and cell towers (free-standing, rooftop, and building-mounted antennas).

Impact of Earthquakes on Networks

The methodology includes telecommunications infrastructure data sources; shaking damage estimation for buildings, towers, and equipment; and infrastructure exposure analyses for ground failure and fire hazards. For free-standing cell towers, the scenario predicted that wind load designs for large towers – defined as self-supporting lattice towers (SST), guyed lattice towers (GT), and monopole towers (MP) – resisted mainshock shaking emulating a quake. It also revealed the structures may not be immune to liquefication hazards.

Figure 1 is a map showing the combined hazards for all types of cellular sites for the HayWired scenario mainshock in the San Francisco Bay region. Each cellular site is identified based on the highest level of hazard mapped for shaking, liquefaction and landslide probability, and fire density (burned-building square footage relative to the developed area containing the fires). The white star shows the mainshock epicenter.

Figure 1: Map from the HayWired Earthquake Scenario—Societal Consequences showing earthquake hazards on cell sites.

The USGS report highlights all the considerations that go into designing wireless networks. In a natural disaster scenario such as an earthquake, the hope is that public safety networks will continue to provide fast, reliable connectivity. First responders rely on effective communications to act quickly and save civilians and property. From firefighters racing to locations that are ablaze and EMS and first-aid squads traveling to care for those injured, to police officers maintaining control, the network is critical to controlling chaos that accompanies a natural disaster.

Maintaining connectivity during natural disasters can certainly be beyond a network operator’s control. Using the data results from the HayWired Earthquake Scenario report can help public safety organizations best plan to increase the chances of maintaining network operation during an earthquake. The best laid plans, however, do not provide a complete guarantee but it will certainly improve the possibility.

A Manmade Disaster - Interference

Network operation during clear days and without a natural disaster is something that mobile operators can control. A manmade problem – interference – is a factor that can be prevented, with proper network design and testing. This is particularly important as FirstNet continues to be deployed throughout the country.

FirstNet public safety LTE will occupy two 10-MHz-wide blocks of spectrum at 758 MHz to 768 MHz and 788 MHz to 798 MHz (Band 14). These frequency bands lie adjacent to existing public safety narrowband spectrum for LMR (769 MHz to 775 MHz and 799 MHz to 805 MHz). Plus, existing commercial wireless bands are also located next to and near the FirstNet bands.

All these LMR and LTE systems can coexist with proper engineering design practices and careful frequency planning. Interference issues are still a major concern as the interaction between all these systems in the 700 MHz band may create passive intermodulation (PIM) products. System uplinks can be significantly affected by PIM interference generated by existing LTE cellular downlinks from a wireless carrier’s network. This problem will only be exacerbated as FirstNet is added to the mix.

Proper Tools to Combat Interference

All carriers operating networks in the 700 MHz band will need to ensure high-quality installations with special care taken to limit or prevent PIM signal levels from degrading overall network performance. This applies to their own networks as well as other carriers’ networks, such as FirstNet.

Utilizing the proper test tools during FirstNet deployment will help minimize manmade causes of network issues for first responders during a mission-critical operation. Many PIM issues will likely be external. To locate these causes and remove them, field technicians will have to conduct the necessary testing of FirstNet networks. Anritsu offers a complete suite of AT&T-approved PIM hunting and testing equipment, including the PIM Master™ MW82119B analyzer (figure 2) and PIM Hunter™ probe.

Figure 2: Anritsu PIM Master analyzer.

Proper test solutions are only part of the solution. Field technicians will need training on how to use the equipment efficiently and conduct necessary measurements accurately. Anritsu provides certification courses that can help ensure PIM interference is not introduced.

Anritsu has developed educational technologies pages on FirstNet and legacy Land Mobile Radio (LMR) systems. Both provide overviews of public safety networks and how to maintain optimum operation.

As FirstNet Deployment Continues, Test Solutions Must Support 5G and Legacy Systems

July 14, 2021

From its inception, FirstNet promised increased speed as one of its benefits. Well, that appears to apply to more than signal transmission. The rollout of the nationwide public-safety broadband network (NPSBN) that will significantly improve the capability and reliability of communications between first responders is more than 90% complete. That puts it about a year ahead of schedule.

A key part of FirstNet deployment is testing the network to ensure it operates in accordance with specifications and regulations. Of course, interference is also a concern, as FirstNet continues the crowding of the RF spectrum and co-location of tower sites. For these reasons, selecting the proper field test solutions is an integral part of the network’s successful roll out.

Though only 10% of FirstNet remains to be deployed, the network is not expected to be complete until 2023. That is because many remaining sites are some of the most challenging to install.

Testing the base stations, which now cover more than 2.7 million square miles, is only one part of the project. For example, earlier this year, the FirstNet Authority announced the addition of 19 deployable assets to the dedicated FirstNet mobile LTE vehicle fleet. Communications Vehicles (CVs), Micro FirstNet Band 14 Satellite Cell on Light Trucks (SatCOLTs) and terrestrial Cell on Wheels (COWs) for Business Continuity and Disaster Recovery are part of this taskforce. All these vehicles are dedicated to quickly addressing operational requirements where there is no terrestrial coverage in an emergency situation or a planned event.

Growing Need for Testing

The need for public safety networks to deliver broad coverage has never been more important. There are now nearly 4 million primary first responders in the U.S., up from 3.5 million pre-pandemic. That number doesn’t even include doctors, nurses, and others who are also typically at mission-critical scenes. Nor does it account for first responders connecting multiple devices, from handsets to body cams and robotics.

Another reason why testing is playing a key role is the integration of 5G into FirstNet. A task order from the FirstNet Authority has prompted the launch of a 5G core to intuitively provide America’s first responders with an optimal experience. First responders in 38 cities now have access to millimeter wave (mmWave) 5G spectrum. We discussed how 5G will affect public safety networks in a previous blog.

All this adds another element for those responsible for public safety network operation. While the focus is on FirstNet, considerable attention and support must remain on legacy technologies and systems. Reliable operation of all mission-critical communications must be maintained in the most challenging environments.

5G + Legacy Testing Support

Public safety test solutions need to provide support to these emerging needs. For 5G in particular, an in-building coverage mapping bundle is beneficial, as it enables technicians to verify proper signal field strength across multiple frequencies in a single walk-through. Any signal from 9 kHz to 6 GHz can be measured, including all public bands, Wi-Fi, NB-IoT, and public service bands (P25, DMR, LTE/FirstNet, UMTS/WCDMA, TETRA). It does it without the need for GPS, allowing stairwells, elevators, and other difficult areas to be mapped easily.

Vector Signal Analysis (VSA) software is another valuable tool. It can provide the testing support to ensure legacy systems operate according to specification. VSA software analyzes IQ data acquired with handheld field analyzers, such as the LMR Master™ S412E and the Field Master Pro™ MS2090A. Software tests physical layer modulation quality of various transmission standards such as FSK and GFSK for DECT systems, and π/4 DQPSK for TETRA systems.

Multiple analysis formats are provided for comprehensive measurements and analysis. Examples include signal spectrum, error vector magnitude (EVM), constellation diagrams, eye diagrams, and numeric tables. Comprehensive insight into all aspects of transmitter performance is provided, as multiple results windows can be displayed simultaneously (figure 1) with the software.

Figure 1: VSA software display indicating transmitter performance.

Conducting measurements is straightforward. The receiver/analyzer captures and converts the RF signal into its complex baseband components, referred to as I/Q signals. The “I” is the in-phase and “Q” is the quadrature signal. The captured I/Q files are transmitted to a PC for various measurements relating to signal quality.

I/Q Conversion Process

Information is encoded into the RF signal by modulating the RF carrier. Once received, each signal is digitized into a bit pattern, which in turn is decoded by the receiver. The demodulation process begins after the transmitted RF signal is down-converted to a lower, intermediate frequency (IF), filtered, and presented to an analog-to-digital converter (ADC) in the receiver. A detector splits the signal into its in-phase and quadrature components, which are subsequently processed by the VSA.

The “I” and “Q” components of the signals are in the time domain. By performing a transformation, the digital stream can be Fourier transformed (FT) or fast Fourier transformed (FFT) for display in the frequency domain.

Once the signal is transformed into the frequency domain, phase information is lost. Although power levels as a function of frequency can be displayed, phase information is critical for signal quality estimations such as EVM and bit error rate (BER) measurements. The result is that demodulation is conducted while the signal remains in the time domain.

You can learn more about the VSA by downloading an application note on the subject. A Land Mobile Radio technology page also provides a primer on public safety communications systems.

How 5G will Affect In-building Public Safety Networks

November 10, 2020

During its quarterly meeting in June, the First Responder Network Authority Board approved $218 million for strategic investments that include initial core network upgrades as the first phase of moving FirstNet to 5G.¹ Shortly thereafter, AT&T stated it was in the process of updating FirstNet to 5G, even though the mobile operator stated tests showed FirstNet is faster than any other commercial network in the United States.¹

Based on this, it’s evident that public safety networks will be migrating to 5G. It likely will be a gradual evolution, however. Anritsu conducted a survey immediately before IWCE 2020 in August. Results revealed only 12.5% of respondents had integrated 5G into their public safety networks.

There are a few reasons for this conservative approach. One is that Band 14 leverages LTE, and earlier this year FirstNet announced that Band 14 will remain LTE for the foreseeable future. It was noted that 4G is working very well for first responders in public safety scenarios. Additionally, since first responder traffic receives priority on mobile networks, 4G meets the current bandwidth and speed requirements.

Still, it is wise for network planners to understand the challenges associated with 5G in public safety networks, particularly when it comes to in-building. Perhaps the biggest issue is that 5G has high attenuation. In short, walls (and doors and windows) and 5G are like oil and water – they don’t mix well. Add in variables such as corners and people walking in hallways and offices, and buildings have plenty of obstacles when related to 5G signals. This is particularly true for Frequency Range 2 (FR2) bands that operate at millimeter wave (mmWave).

Standards Set the Stage

Various governing bodies have written specifications pertaining to in-building network performance. These will apply to 5G networks, as well. The regulations are viewed more as guidelines, in large part because of the myriad of networks that call a building home. In addition to FirstNet, most commercial structures will have LTE, Wi-Fi, and NB-IoT. Some will have private networks, such as those for corporations and two-way radio networks such as TETRA.

Two regulations set the foundation for all in-building public safety networks:

International Fire Code (IFC) 510 – It specifies that, “All new buildings shall have approved radio coverage for emergency responders within the building based upon the existing coverage levels of the public safety communication systems of the jurisdiction at the exterior of the building.” Per IFC 510, two-way radio coverage must be a minimum of 95% on each floor of the building.

NFPA 72 – The National Fire Protection Association (NFPA) has established standards (figure 1) that are more specific than those created by the IFC. NFPA 72 states that critical areas, such as the fire command center(s), fire pump room(s), exit stairs, exit passageways, elevator lobbies, standpipe cabinets, sprinkler sectional valve locations, and other areas deemed critical by the authority having jurisdiction, shall be provided with 99% floor area radio coverage.

Figure 1: NFPA has established standards for in-building public safety network performance.

There are two key elements that should be noted with NFPA 72:

• A minimum in-bound signal strength of -95 dBm, or other signal strength as required by authority having jurisdiction, shall be provided throughout the coverage area.
• Buildings and structures that cannot support the required level of coverage shall be enhanced to achieve the necessary adequate coverage. Typical improvements include adding a radiating cable system or distributed antenna system (DAS) with FCC-certified signal booster, or both.

While IFC 510 and NFPA 72 provide the roadmap, the path can – and often is – changed. Each jurisdiction can alter the national level model code to meet unique requirements. The specifics of these local ordinances and codes vary, but most include:

• Minimum signal strength limit
• Established limit over a specified percentage of each floor
• Specific level of reliability (i.e. power backup, water protection, and cable protection)
• Designated frequency band(s) for public safety coverage
• Testing requirements and procedures
• On-going monitoring and maintenance processes

Ultimately, the Authority Having Jurisdiction (AHJ) has final say, and building owners and contractors must get their approval. In most cases, a “Letter of Certification” must be submitted to the local fire officials before they will issue a “Certificate of Occupancy.” Without it, the buildings cannot open or operate. For these reasons, building owners, contractors, and network operators all must understand how to effectively install and maintain 5G public safety networks.

5G Changes Network Architecture

Public safety networks utilize mature technologies that operate in the sub-6 GHz frequencies. 5G will need new network nodes, as the architecture will change to support mmWave bands. It will go beyond enhancements to the radio access network (RAN). There also must be improvements to the core network, and the entire network architecture is more distributed with compute and storage at the edge. Advanced network planning analysis is necessary to accommodate 5G FR2 and its associated attenuation.

Coverage Mapping Aids In-building Verification

To meet all the testing, cost, and efficiency goals associated with streamlining in-building network verification, an integrated approach to coverage mapping has to be taken. An in-building coverage mapping bundle (figure 2) enables technicians to verify proper signal field strength across multiple frequencies in a single walk-through.

The system has three components – a Remote Spectrum Monitor with fast sweep speeds, a tracker worn by technicians to record in-building position to the tracking software as they conduct the walkthrough, and dedicated software. This system incorporates the tried and true method of coverage mapping that is aiding in the verification of in-building 4G LTE private networks.

 

Figure 2: Dedicated in-building coverage mapping solutions help ensure public safety networks are in compliance with AHJ guidelines.

 

The coverage mapping tools need to have a few extra capabilities for 5G. These include:

• Knowledge of FR1 versus FR2 characteristics
• More antennas/repeaters for FR2 coverage
• Modulation analysis to ensure signal throughput
• Awareness of 5G FR2 attenuation objects

To learn more about the impact 5G will have on public safety networks and how to overcome the associated challenges, watch this IWCE 2020 webinar.

Reference:

¹ Fierce Wireless; AT&T's Elbaz says the carrier plans to transition FirstNet to 5G

Method Simplifies Validating In-building Public Safety Network Performance

August 7, 2020

Validating public safety wireless network coverage in-building presents obstacles for contractors and network engineers. It is more than the technical challenges created by concrete walls, environmentally treated windows, and other common building materials. There are stringent government regulations to ensure performance in mission critical situations, as well.

Easy-to-use, time-efficient, and economical test solutions to satisfy in-building network verification are necessities, as much of this verification is now the responsibility of building contractors. They must ensure coverage meets local requirements, as well as the national NFPA 72 (National Fire Alarm and Signaling Code) standard published by the National Fire Protection Association. For in-building DAS and Wi-Fi systems, the standard requires 99% floor area radio coverage.

Alternative to GPS Signal

While the general scope may be clear and concise, the same can’t be said for the actual coverage validation process. The biggest hurdle is the in-building unreliability of a GPS signal – the most common way to coordinate position data with any kind of test data results. This lack of GPS signal is especially evident in NFPA72 “critical areas,” such as the fire command center(s), fire pump room(s), exit passageways, elevator lobbies, exit stairs, standpipe cabinets, and sprinkler sectional valve locations. In particular, the latter three areas are especially isolated, making GPS signal availability even more sparse.

While in-building networks are not the legal responsibility of the contractor, there may be occupancy permit requirements from the building owners requiring a certain coverage guarantee. Without the certificate of occupancy (CO), the building owner will not send the final payment to the contractor, creating a financial incentive for the contractor to verify network coverage.

Current building standards are constantly evolving, both at the public safety level and the commercial network level. The emergence of 5G at both Frequency Range 1 (FR1) and Frequency Range 2 (FR2) for in-building networks, and the requirements of high reliability low latency applications have increased the number of bands and air protocols that need to be supported. For example, the plans to introduce the CBRS band into buildings as private LTE will create additional requirements as they are implemented in different industries.

If building contractors must conduct RF scans for every band, the testing exercise will multiply linearly by the number of bands in the entire building. Each band has an associated cost factor for validation, meaning the expense can be dramatic for a contractor. To solve this dilemma, a solution (figure 1) that can validate all bands simultaneously while a technician walks through the building has been developed.

Figure 1: In-building network solution compact enough to fit in a backpack.

Integrated In-building Test Solution

The solution uses a local “tracker” rather than GPS to coordinate its position with the RF readings. A true 3D map is created by the tracker to enable technicians to easily pinpoint weak or no-coverage areas and address them appropriately. It also aids in preparing the necessary documents to satisfy legal requirements.

The solution can scan as many as six different frequencies simultaneously, including LTE bands, Wi-Fi, P25, and TETRA, in a single walkthrough. This saves significant time and cost.

Practicality is also addressed. Weighing less than 10 pounds, it can be carried without strenuous effort through a building, including stairwells. It also has a 4-hour battery, which is enough life to complete a walkthrough of a large multi-story commercial structure.

Integrated Approach Key to Success

To meet all the testing, cost, and efficiency goals associated with streamlining in-building testing, an integrated approach has to be taken. The best tool for this environment combines hardware and software:

Remote Spectrum Monitor: A hardware unit for this application must deliver outstanding sweep speeds, even for smaller resolution (RBW) or video bandwidths (VBW). The latter specifications are important for narrowband public safety communications standards, such as analog FM, P25, TETRA, DMR, and dPMR.

Tracker: Technicians must be able to wear a device that delivers in-building position to the tracking software as they conduct the walkthrough. It can store the technician’s position in 3D, allowing previously hard-to-analyze areas, such as stairwells and elevators, to be accurately tested.

Software: Two software packages are necessary. The first is a signal mapper that controls the remote spectrum monitor by collecting the RF data from the user-defined frequency bands and coordinating it with the position data. The second is command software that analyzes the data gathered by the signal mapper, as well as offers users the capability to prepare any necessary reports and 2D/3D coverage mapping images (figure 2). It also automatically gathers the building outlines from satellite data and accepts photos of building floor plans.

Figure 2: Coverage mapping images created by dedicated software.

Simple Measurement Process

The time necessary to conduct tests is further reduced by a simple measurement process, which also minimizes training. Because the solution has a high level of intelligence, accuracy is not sacrificed for speed. The process consists of:

1. Opening a web browser on any Android device and typing in the IP address of the remote spectrum monitor unit. Once communication with the test unit has been verified, the browser can be closed.
2. Setting up the Signal Mapper and Channel Scanner. This process includes entering all bands of interest by defining frequency, SPAN, RBW, and Ref Level.
3. Accessing Building Outline/Floor Plan. The building outline is automatically input by the command software using current location coordinates and accessing the building outline from a database of satellite images. Next, the user simply snaps a picture of the floor plan normally found at a main entrance/exit to the floor, or the elevator doors and fire exits. The photo of the floor plan is overlaid onto the building floor plan and adjusted by the user until there is a fit (Figure 3). There is also a manual editing mode if a picture of a floor plan is not available.
   
   

   Figure 3: Integration of building floor plan with image taken while in-building.
4. Calibration. Technicians must calibrate the tracking unit with his/her stride by walking at a normal pace for at least 30 feet in a straight line. Once finished, the user needs to mark the end position on the floor plan. While this two-point calibration is sufficient, it is recommended that an additional calibration step be done. The technician should return to the original start position and mark it as the third calibration point for greater accuracy.

Analysis results can be stored locally in the required Android device for security purposes. It can also be uploaded to the cloud for reporting convenience. The results can be displayed in 2D or 3D so engineers can visually inspect for weak coverage areas.

To learn more about how to conduct these in-building measurements on public safety networks, download the Validating In-Building Wireless Coverage of Public Safety, LTE, and Wi-Fi^® Networks app note.

Test Procedures Help PTC ACSES Systems Meet Year-end Compliance, Functionality Deadline

May 18, 2020

The federal government is calling “All aboard” to the United States railroad industry in a louder voice and with greater urgency, as the industry speeds towards the December 31, 2020 deadline for full compliance and functionality of Positive Train Control (PTC) Advanced Civil Speed Enforcement System (ACSES) systems. For those railways, much work remains – particularly testing – before the calendar flips to 2021. 

Forty-two Class 1 railroads are required to implement PTC systems, ranging from large passenger lines to freight railroads. The technology will cover approximately 60,000 miles of the national railroad network, and affect an estimated 20,000 locomotives, 24,000 waypoints (each with a unique digital address), and back office servers. All of this will be done utilizing a new interoperable secure wireless network with more than 400,000 components.

That’s a tall order in and of itself, but there is more. Three criteria must be met for railroads to have their PTC ACSES systems meet government approval. They have to:

1. Receive Federal Railroad Administration (FRA) approval of their PTC Safety Plan for system certification
2. Install full PTC operations on all mainline route miles
3. Verify interoperability so tenant locomotives operating on the same main line can communicate to PTC and seamlessly cross property boundaries

PTC = Increased Safety

Undoubtedly, PTC is worth all of the effort. PTC is a processor-based/communication-based train control system that can automatically control train speeds and movements in the event a rail operator fails to take appropriate action. It can prevent overspeed derailments, incursion into an established work zone, passing through a main line switch in the improper position, among other accidents. All of this will save countless lives.

Another benefit of PTC is interoperability. It allows for equipped locomotives traversing another railroad’s PTC-equipped territories to communicate with and respond to that respective railroad’s PTC system.

ACSES is one of three PTC systems. It utilizes sets of wayside transponders installed at home signals, distant signals, pre-distance signals, block points, or cut section locations to communicate to the on-board components. PTC ACSES provides railway trains with positive enforcement of speed restrictions based on the physical characteristics of the line, such as bridges, curves, and tilting. The on-board components keep track of a train’s position and continuously calculate a maximum safe braking curve for upcoming speed restrictions. If the train exceeds the safe braking curve, the brakes are automatically applied.

Testing to Ensure Operation, Compliance

Several stages of testing must be completed to receive government approval. Among the most challenging is testing a PTC ACSES implementation during field and revenue service demonstration (RSD) to ensure that the new deployment is operating properly.

Most PTC ACSES signals shown in the block diagram of figure 1 are in a proprietary protocol. Over-the-Air (OTA) transmission enables this message flow to be captured. With the correct modulation decode capabilities, testing of the PTC ACSES system quality and accuracy can be made.

Figure 1: PTC ACSES Communications Block Diagram

Several tests are important to verify that signals are being transmitted in accordance with the specification. Among the most critical are:

• Receive Signal Strength Indicator (RSSI) to test the RF received signal strength
• Error Vector Magnitude (EVM) to ascertain the quality of the received ACSES data transmitted by the system
• Per Message Bit Error Rate (BER) to ensure the data quality received per message
• Cumulative Packet Error Rate (PER) to verify signal/data quality at the packet level

To perform these tests, field engineers and technicians responsible for the safety systems need a high-performance receiver/spectrum analyzer, such as the Anritsu LMR Master™ S412E analyzer (figure 2). It can be used to conduct several critical functions during field testing:

• Decoding the message type, such as source of message (i.e., wayside) and destination type (i.e., office or central control)
• Capturing raw message payload data in a familiar hex format
• Leveraging hex also enables other information to be captured and decoded, such as source and destination ATCS addresses, as well as time slot in frame and epoch

Figure 2: LMR Master S412E high-performance receiver/spectrum analyzer

Value of OTA Testing PTC ACSES

OTA testing is preferred because it captures a signal and makes a measurement between the base radio unit (waypoint) and mobile radio unit (locomotive/railcar). This is critical, as this is the only way a high-performance receiver/signal analyzer can access and analyze the otherwise secure PTC ACSES transmission.

To perform these tests accurately and efficiently, a high-performance receiver/spectrum analyzer needs PTC ACSES demodulation capabilities. The configuration also includes the appropriate antenna (and possibly a filter) tuned in to the PTC ACSES transmit frequency. Field engineers and technicians can measure and analyze the PTC ACSES signal quality and demodulate the messages to help validate proper PTC ACSES functionality, as well as spot potential problems for troubleshooting. You can learn more about PTC ACSES OTA testing by watching this educational video.

PTC ACSES Coverage Mapping

Coverage mapping is another essential tool in assessing a PTC ACSES signal environment and ensuring proper deployment, installation, and operation. Field engineers and technicians can use coverage mapping to verify signal strength and quality over a specific area by effectively monitoring RSSI and ACPR levels, as well as to conduct BER mapping. For PTC ACSES systems, coverage mapping should be conducted over the various rail lines used for passenger rail as well as integrated lines with Class 1 commercial traffic.

Coverage mapping can be performed with a high-performance receiver/signal analyzer with GPS connected to the PTC ACSES radio’s antenna system. The high-performance receiver/spectrum analyzer with mapping capabilities can also perform coverage mapping by accurately and simultaneously collecting key PTC ACSES signal quality measurements, such as EVM, BER, and RSSI data, for the PTC ACSES frequency under test. Parameters from each measurement is plotted on a map of the area/route being tested.

All the information saved is in .kml format so it is compatible with Google maps. All three values can then be displayed on Google Maps to gain a clear insight into any areas that may need improved coverage to ensure seamless operation (Figure 3).

Figure 3: PTC ACSES Coverage Mapping Using Google Maps

A PTC technology page has been published that outlines PTC and how to properly test it, as well as valuable resources, including videos and application notes. You can also download an Anritsu application note on Testing PTC ACSES deployments to meet mandated implementation standards.

Co-existence of Public Safety LTE and LMR Requires Planning, Proper Test Tools

October 3, 2018

One of the hottest topics in the public safety arena is the deployment of private Long Term Evolution (LTE) high-speed wireless communications – either as a replacement (not likely) or complement (probable) to traditional Land Mobile Radio (LMR) standards such as P25 and TETRA. Industry expert consensus is that a profound transformation is underway and those of us in the LMR community need to understand the changes and their meaning.  

The Need for LTE

Narrowband analog and digital LMR systems have been sufficient for police, fire, EMS, and other first responders for years. In today’s mission critical world, however, many situations require broadband services. Examples include when first responders need to access data-intensive applications, search databases, or share video. LTE enables such extremely high-speed data communications while current LMR technologies are severely limited in these applications. The enhanced data services of LTE are some of the main driving forces that makes it attractive for public safety.

LTE is also the technology that will allow public safety networks to meet the mandates set by Congress when it passed FirstNet in the aftermath of the September 11 attacks. LTE technology will be a cornerstone of the high-speed, nationwide wireless broadband network dedicated to public safety.

One reason LTE was selected for the public safety sector is because it has already been successfully rolled out by commercial operators. Because of this fact, the premise is that the technology is well understood and easy to install, use, and maintain.

It is important to note, though, that commercial LTE differs quite a bit from LTE systems for critical communications. Public safety LTE networks will have special features and requirements to make them much more reliable, a necessity given the environments in which they will be used. Two key factors that those responsible for public safety need to consider when planning LTE network deployment are interference and handset power.

Interference – As we stated at the beginning of this post, LTE will not supplant P25 and TETRA. Rather, it will operate in conjunction with existing LMR networks. Because these networks will often occupy the same frequency bands, interference becomes a primary concern for system designers, installers, and maintainers.  

Handset Power – LMR handsets typically transmit with 3 to 5 watts of power. Their LTE counterparts may only transmit with 1 watt, approximately. This means LMR systems will have longer range. To compensate, operators will need to install many more LTE sites spaced closer together. The result will be higher equipment and maintenance costs. Therefore, a broadband network at 700 MHz will not be able to replace LMR in many locations across the country because of RF propagation properties, and matching LTE to LMR coverage and reliability is just too cost-prohibitive.

Test Considerations

As noted earlier, LTE and LMR networks will invariably co-exist – at least for the foreseeable future. For this reason, testing is an important issue for carriers and those responsible for installing and maintaining the networks. FirstNet public safety LTE will occupy two 10-MHz-wide spectrum blocks from 758 MHz to 768 MHz and its duplex spectrum offset +30 MHz away at 788 MHz to 798 MHz. These frequency bands lie adjacent to the public safety narrowband spectrum of 769 MHz to 775 MHz and its duplex pair +30 MHz away at 799 MHz to 805 MHz.

A recent study conducted by the U.S. Department of Homeland Security (DHS) suggests that LMR and LTE systems operating at these frequencies can coexist with proper engineering design practices and careful frequency planning. Even with these proper design considerations, interference may still be a concern because the guard bands between the LTE and LMR spectra are only 1 MHz wide.

Some portions of the 700-MHz FirstNet bands may be heavily affected by passive intermodulation (PIM) interference generated by existing LTE cellular downlinks used by major wireless carriers. This means all carriers operating those networks will need to ensure high-quality installations with particular attention given to reduce or prevent PIM signal levels from de-grading overall network performance.

The Test Conundrum

LMR and LTE are vastly different technologies. LTE is much more complex, due to its variable channel bandwidths and use of both multiple-input multiple-output (MIMO) communications and orthogonal frequency-division multiple access (OFDMA) modulation to support high data rates.

Supporting two separate networks can become challenging in terms of personnel requirements and test equipment needs. Both LTE and LMR systems have to contend with multipath, fading, and other factors that degrade signal quality. Handheld test equipment that can handle the complexity of testing LTE networks and mapping bit error rate (BER), as well as the modulation fidelity of LMR networks, is critical so technicians and engineers have confidence that the public safety communications systems they install and maintain will work according to specification.  

It is typically assumed that all these measurements need to be taken with multiple instruments. This poses a few problems. The first is that it is cumbersome to carry numerous tools into the field. It also requires crews to be trained and proficient in two highly different technologies or deploy two teams — one dedicated to LTE and one to LMR.

That is not the case, however. The LMR Master™ S412E (figure 2) is the industry’s first and only battery-powered LMR handheld field analyzer that can test broadband and narrowband systems. It combines many of the tools needed to install, maintain and certify LTE and LMR systems into a single instrument with one user interface. Multi-function analyzers such as the LMR Master S412E can significantly reduce the number of tools technicians and engineers need to verify operation of wireless network infrastructure and diagnose problems in the field.

Figure 2

What the Future Holds

Next-generation public safety communications will more than likely pair narrowband LMR networks for voice with broadband LTE networks for high-speed data. Ensuring these networks are properly installed and maintained is vital to ensuring mission-critical public safety communications so first responders and the general public remain safe.

To learn more about public safety communications systems, visit the Anritsu Land Mobile Radio technology page.

Class 1 National Railroad PTC Radios Stay on Track Thanks to Anritsu

August 31, 2018

Verifying Positive Train Control (PTC) radio performance in the field is no easy task. That point was proven recently when a Class 1 national railroad believed its PTC radios were drifting out of tolerance. When the OEM radio supplier challenged the field test results and began charging thousands of dollars in service fees, the railroad needed a reliable and accurate test process. Thankfully, Anritsu developed a solution that has saved the railroad money while also ensuring the PTC network is operating according to specification.

Upon conducting initial field tests, the railroad returned to the supplier a small number of radios that appeared to be out of specification. When the OEM conducted its tests, it found no issues but did not levy a No Fault Found (NFF) charge for the evaluation. As the number of radios returned increased to almost 100, however, the OEM supplier assessed a $1,150 Return Merchandise Approval (RMA) fee to the railroad.

This increase in radios found out of specification was escalated to railroad management, who became worried that the fees assessed for all the returned units would be significant. There was the added concern by railroad executives that their PTC collision avoidance system was not in compliance with the design requirements. If that was the case, the railroad would be subject to potential government fines. Additionally, if the system did not operate properly, there was an increased risk of a preventable accident occurring.

With all these variables lurking, railroad management needed a reliable field deployable test analyzer that could accurately measure Peak Envelope Power (PEP) or run the risk of incurring significant NFF and RMA fees. That’s when Anritsu offered to work with them to develop a solution.

PEP Testing Challenge

Specifically, the test solution that was necessary had to be capable of accurately verifying that the PEP on PTC mobile radios operating in a 217.6-222 MHz range met published specifications. By definition, PEP is the highest undistorted power supplied to the antenna transmission line over a single or a series of RF cycles. Pass/fail criteria are determined by how well the RF power measurement falls within the window.

Recognizing the urgent need for a solution that met these requirements, Anritsu representatives met with railroad personnel. Working closely with the railroad company throughout, Anritsu was able to quickly develop the PTC Analyzer option for its LMR Master™ S412E Land Mobile Radio Modulation Analyzer (figure 1).

Figure 1

The LMR Master-based PEP solution was able to verify that the radios complied with the 48.75+/-1 specification defined by the PTC network supplier and adhered to by the OEM supplier. It has eliminated the need to return radios to the OEM for verification, saving money and maintaining the relationship between the Tier 1 national railroad and the supplier.

Field technicians are currently using the handheld analyzer during pre-installation component test, system test, preventative maintenance, and repair and troubleshooting. Its ease of operation and accurate results has made management more confident in their PTC network.

Overall, the LMR Master has proven to be a valuable field tool in other applications for the national railroad. It is an easy-to-use, lightweight (<10 lbs.), field-rugged, battery-operated solution that replaces an RF power meter, antenna/system line sweep solution, and 2-port device tester. The analyzer can detect rogue interference sources ranging from CW to bursty signals, map RF coverage, and support individual radios and radio systems. In addition to PTC, railroad technicians are using the LMR Master to test P25, TETRA, DMR, and analog UHF and VHF radio systems. The LMR Master’s LTE Analyzer can also be used to verify the new FirstNet nationwide LTE public safety network.

Summary

By working closely with a Tier 1 national railroad, Anritsu developed a test solution to quickly and accurately test PEP radio power without to avoid very costly RMA and NFF fees. Additionally, railway technicians can now use the LMR Master with the PTC Analyzer option to troubleshoot and remediate issues they were unable to address previously.

To learn more about the LMR Master and how it can be used in PTC applications, download the PTC testing application note.

Hybrid Public Safety Networks Converging LTE and LMR Solution for Evolving Mission Critical Comms

July 18, 2018

The convergence of 3G and 4G private mobile networks and LMR radio communications remains a key talking point in the public safety industry. It has been a primary conversion during industry trade shows, APCO meetings, association gatherings, and in police, fire, and EMS command centers.

Even though broadband LTE networks have been around for more than a decade, it may come as a surprise to many that the analog to digital transition has been a bit of a slow move and is still in process. Digital systems didn’t overtake their analog counterparts until 2017. While LTE devices used in the mission critical sector are still only a fraction compared to LMR radios, the projection is that in the next 10-20 years LTE will become the go-to mission critical technology, according to IHS Market Research (table 1).

 

Table 1

As public safety networks evolve to meet the growing demands of mission critical applications, LTE and LMR will coexist for the next decade or two. Ensuring such systems can operate as they should in life-threatening situations will be challenging, as a result.

LTE Growth in Public Safety

There are a few reasons why LTE is making its move in public safety networks:

Standards Development – Mission critical communications LTE standards are developing quickly, with elements to meet the market needs being passed. Release 13, which was completed by the 3GPP in 2016, addressed the key issue of reduced latency, as well as enhancements to machine-type communications, and single cell point-to-multipoint. In 2017, Release 14 was approved and it further enhanced mission critical push-to-talk capability as well as mission critical data and mission critical video.

Data-intensive Requirements – Many public safety tasks require broadband services, such as when first responders need to access data-intensive applications, search databases, or share video or images. For example, an engine company is dispatched to a burning building. With an LTE network, the command center can send the fire fighters a floor plan, so they don’t enter the burning building blind.

LMR Still has a Voice

Despite the growth of LTE, LMR still has a strong presence in public safety networks, and that will continue. Despite the data advantages provided by LTE, there are technology trade-offs. For one, to ensure the high data rate associated with broadband networks such as LTE, the frequency spectrum used must be increased. The result is lower power, shorter range and less resistance to interference. Because of this, narrowband LMR is preferred for rural areas where these considerations are essential. 

What this all means is that LMR is not going to be replaced by LTE in the near term. Cost, not surprisingly, is another reason why LMR will remain relevant. Many LMR operators have just finished converting from analog systems to digital systems such as P25, TETRA, and DMR and don’t want to invest in a new technology so quickly. Plus, for LTE networks to provide the same coverage area as an LMR system, operators will need to install many more cell sites closely together, resulting in higher equipment and maintenance expenses.

Public Safety Road Ahead

Ultimately that means LTE will augment LMR for the next decade. During that time, there will be hybrid systems to accommodate the reliability, cost, and data needs. This presents potential interference issues, as the guard band between the LTE and LMR spectra is only 1 MHz wide. Another potential cause of interferences is that the primary LMR standards (figure 1) do not play nice with each other. 

Figure 1

Deploying and maintaining the operation of public safety networks during this transition has its obstacles. As we have outlined here, LMR and LTE are very different technologies. Supporting two separate networks can prove challenging both in terms of staffing and test equipment requirements.

Making Test Cost-effective

Carrying multiple instruments into the field is not acceptable. Not only does it add cost to deploying and maintaining networks, it requires field technicians to learn and be adept with separate test equipment. Fortunately, the Anritsu LMR Master™ S412E is a battery-powered LMR field analyzer capable of supporting the complexity of testing LTE networks and mapping

bit error rate (BER) and modulation fidelity of LMR networks.

The handheld analyzer combines many of the tools needed to install, maintain, and certify LTE and LMR systems into a single instrument with a common user interface. This gives technicians and engineers responsible for public safety communications systems confidence that these networks will work as expected.

To learn more about the market conditions surrounding public safety networks, you can watch a land mobile radio (LMR) versus mission-critical LTE webinar by IHS Market sponsored by Anritsu.

Field-Portable Spectrum and Signal Analysis: Critical in an Increasingly Wireless World

It seems like every week brings more news stories about emerging wireless technologies. Existing companies are seeking to expand their current wireless offerings, while others are offering wireless communications as a new product. There are even corporations who want to use both new and existing wireless technologies to support their products and services. All this means the wireless world continues to be increasingly complex. 

These are exciting times, to be sure, but as each new technology and application adds complexity it creates geometrically-expanding opportunities for interference. Laboratory testing and certification helps, but in the real world these conflicts are both created and resolved in the field. When it comes to solving interference in public safety networks, the proper test solutions can be the difference between a mission critical signal being successfully transmitted and received or not.

The proper test solutions can be the difference between a mission critical signal being successfully transmitted and received or not.

 

Case in Point: California’s East Bay

Consider the case of the FCC finding against Full Spectrum. Reviewing the FCC’s Notice of Apparent Liability (NAL) in DA 18-322, agents from the FCC’s East Bay (California) Field Office responded to complaints from a licensed cellular carrier about interference to the 776 – 787 MHz (C Block Upper 700 MHz band). The interference affected the licensee’s base stations in and around San José, California. Initially using mobile direction-finding equipment, agents added field-portable spectrum analyzers to discover antennas and radios at a mountain-side site were causing interference in the licensed cellular band. 

Nothing Replaces Field Tests

In some scenarios, cellular carriers are the offenders. The case of Oakland, California and its public safety radio system illustrates clearly that laboratory testing and standards cannot prevent interference in the field. It took the City of Oakland and their consultants several months to realize that cellular signals were causing interference to the city’s digital APCO Project 25 radio network.

The most noted example of this problem was the now-famous incident where the public safety radio network failed during a visit to the city by the President of the United States. It took field analysis and the deduction of some clever engineers to understand the cause of this issue. Further field analysis was done to ensure that the fixes to the problem did not, in turn, create more difficulties. 

Merger Impact

T-Mobile (Deutsche Telekom) and Sprint (Softbank Group) have announced intention to merge and begin pursuing 5G deployments. Sprint/Softbank has extensive spectrum holdings in the 2.5 GHz band, and T-Mobile obtained spectrum in the 600 MHz reverse auction. The interaction between 5G signals and current technologies is still unknown – but we can be sure that if problems arise, it will be portable analysis, such as what is offered through the Anritsu LMR Master™ Land Mobile Radio Modulation Analyzer (figure 1), that’s used to identify the problem. 

 

Anritsu’s solutions extend far beyond the LMR Master, and all are tested and proven. From basic spectrum analysis to measuring complex protocols like 4G LTE, there is a field test solution to solve interference issues and ensure the operation of public safety networks in mission critical applications.

To learn more, visit our interference hunting solutions page.

Why Remote Spectrum Monitoring is Important When Deploying PTC Systems

January 16, 2018

According to the Federal Railroad Administration, there were more than 1,000 train accidents in the United States in 2017. This should come as little surprise to those in the industry, as well as anyone who watches news programs or reads a newspaper. Incidents in New York, Philadelphia, and Washington, D.C. are just three of the accidents that have garnered coverage by the media last year.

What may not be as obvious is that, while accidents continue to be a too-frequent occurrence, the number has decreased since 2014. One reason is the implementation of Positive Train Control (PTC). The advanced communications system that automatically controls train activity to minimize collisions, derailments, and improper movement through track switches is scheduled for full implementation by the end of this year. As shown in figure 1, many of the rail carriers are gearing up to meet that Congressional deadline.

Figure 1

PTC Benefits

Using an On Board Computer (OBC), PTC systems (figure 2) monitor static and dynamic conditions in real time to alert train engineers of on-coming speed limits or track conditions that require the train to slow down or stop completely depending on the train’s position, direction and speed. If the engineer does not respond correctly or in time, the OBC automatically decelerates the train and can even bring it to a halt within a safe braking distance from the restriction. Even though PTC systems cannot stop train-vehicle accidents at crossings or incidents that occur when people illegally walk on a track, the amount of incidents they can prevent makes them a vital component of modern train systems.

Figure 2

Because of the mission critical nature of PTC, interference-free communications is required. The importance of clear spectrum is evident by a recently completed three-year study conducted by Clifton Weiss & Associates, Inc. (CWA), an engineering consultancy that specializes in electronic communication systems planning, design, and integration. CWA, which provides services that improve transportation and utility systems through technological innovations, leveraged the testing capability of the Anritsu MS27101A Remote Spectrum Monitor™ with Vision™ database software to monitor PTC systems by capturing signals across a wide dynamic range in real time and logging the data for later analysis.

As part of the study, CWA monitored RF signals on an actively operating railway to identify periodic or persistent interferers that would degrade the performance of the railway’s pre-assigned PTC public safety system locations. A challenge under normal circumstances, CWA was given a deadline of less than four months to provide the first detailed report.

Due to the short timeline, three remote spectrum monitoring instruments with LTE connectivity were needed to capture signals across the required frequency range with fast measurement speeds. Database software was also necessary to log the data for analysis and create customized reports.  

Anritsu Solutions

Using the MS27101A, 9 kHz – 6 GHz, ½-rack Remote Spectrum Monitor web-based automated data capturing hardware and Vision software platform, CWA was able to meet the interference study’s stringent technical requirements. Vision provided complete command and control of all three spectrum monitoring receivers. The software also created a near-real-time and continuous spectrum view while minimizing backhaul data usage, no easy task given the potentially short signal duration in the PTC band.

Each MS27101A used a cellular 4G network via LTE modem. Vision’s customized database presented the spectrum monitoring information correlated to GPS coordinates from each MS27101A. CWA engineers regularly monitored the acquired data, providing monthly reports. They conducted power measurements in signal and guard bands to measure signal activity and minimize spillover. Collecting data 24/7 allowed for periodic occupancy reports generated by Vision’s monitoring system. Figure 3 shows the measurement dashboard and spectrum occupancy statistics.

Figure 3

Anritsu’s remote spectrum monitors and associated software suites were able to monitor, analyze and archive spectral activity, which was critical for maximizing available spectrum resources and minimizing interfering events. Complementing these features were the fast sweep and low noise floor of the MS27101A, which assisted with capturing the necessary signal data and analyzing it in CWA’s short deadline.

For more information about this application, read a complete success story on the project. For more information on spectrum monitoring techniques, as well as Anritsu’s solutions for these environments, visit our Remote Spectrum Monitoring page.

As FirstNet Opt-Out Deadline Nears, Questions Remain

December 8, 2017

In 2012, Congress passed legislation providing both radio spectrum and initial funding for FirstNet, a nationwide network of wireless broadband, for use by public safety agencies. After completing a Request for Proposal (RFP) process, AT&T was selected as the prime contractor to build FirstNet. Each state and U.S. territory has the option to opt-out of FirstNet and use another contractor for the Radio Access Network (RAN), but these alternative RANs must adhere to standards and be completely interoperable with the primary network. The question of how to test for this interoperability remains open, as is the question of who will define the interoperability standard. 

 

 

Governors of 50 states and six U.S. territories have until the end of this month to opt-out or opt-in. If they do nothing, this results in an automatic opt-in. Not surprisingly, competitors to AT&T, namely Verizon Wireless and Rivada Networks, have been making the case for states to use alternative RANs.  

RAN Options

What will happen if a state chooses an alternative RAN? Because interoperability is a core mission for the FirstNet project, alternative RANs must be tested to ensure 100% compatibility with the opt-in network. Regardless of who authors it, an interoperability standard will have to be written and approved by stakeholders, likely under the guidance of the National Institute of Standards and Technology (NIST) and National Telecommunications and Information Administration (NTIA). Despite the fact that it leads and controls the 4G/LTE standard on which FirstNet is based, it is highly unlikely that 3GPP, a global organization, will take on definition of FirstNet interoperability – this will end up being a U.S. effort.

Once an interoperability standard is defined, a test plan will be developed. This will require an extensive amount of laboratory and field work to ensure that the alternative RAN’s LTE uplink and downlink will work with user equipment from the opt-in network. Testing of user equipment in Direct Mode (which allows user-to-user communication, without a network) will also be done. 

Investment in Test

The level of effort in this cannot be underestimated. States that believe they will save money by using an alternative RAN must factor in the added expense of people and management needed to realize those savings. Reducing those costs will require an investment in test equipment that can multiply the effectiveness of field test personnel and allow them to test more sites in less time.

Fortunately, Anritsu already has portable tools to field test FirstNet. The LMR Master™ S412E Land Mobile Radio Modulation Analyzer (figure 1) was designed from Day One to field test both digital narrowband and LTE systems.

Figure 1

We invite you to review our thought leadership on this topic by reading our Effectively Testing 700 MHz Public Safety LTE Broadband and P25 Narrowband Networks and The Impact of LTE on the LMR Industry white papers, as well as an application note entitled Receiver Blocking Analysis.

You can also visit the Anritsu website for additional materials, as well as contact information to learn more about how the LMR Master handheld analyzer can help make FirstNet a reality.