Solid Signals

The Case for LMR Continuing to Play a Prominent Role in Public Safety Networks

November 11, 2016

Major LMR vendors are shifting their focus to LTE, but does that mean the end of innovation and support for LMR technologies? The consensus of industry experts is NO!

LMR is not going to be replaced by LTE in public safety networks any time soon and all the market players will continue to innovate and support LMR technologies for the foreseeable future. A more likely scenario is that LMR will remain relevant for a very long time with LTE augmenting instead of replacing LMR for at least a decade or more.

Cost is the number one factor for LMR maintaining a share of the public safety network infrastructure. Many LMR operators have just finished converting from analog systems to digital counterparts such as P25, TETRA, and DMR. In fact, in the initial roll out of FirstNet, LTE is considered a complementary enabler to public safety systems that will sit on top of existing LMR voice systems. In addition, LTE requires much more bandwidth than narrowband LMR systems and the need for sufficient spectrum is a barrier for scalable deployments throughout the world.

Another import consideration is the technical challenges installers, maintainers, and operators will face. One of the reasons LTE was selected as the technology of choice for broadband communications in the public safety sector is because it has been rolled out by commercial operators, so it should be well understood and easy to install, use, and maintain. We must remember, however, that LTE systems for mission critical communications have special features and requirements that the commercial networks don’t have to worry about. The primary – and obvious – concern being that it needs to be much more reliable as lives of first responders and citizens are at stake. It also must operate in conjunction with existing LMR networks, which are often times in the same frequency bands. This can present challenging interference issues for system designers, installers, and maintainers.

RF coverage and other system considerations must be addressed, as well. LMR handsets typically transmit with 3-5 Watts, whereas an LTE handset may only be capable of transmitting with about 1 Watt. This translates directly into longer range for LMR systems. So, for an LTE network to provide the same coverage area as an LMR network, operators will need to install many more sites spaced closer together. The result is higher equipment and maintenance costs. Because of infrastructure expenditures, a broadband network at 700 MHz will not be able to replace LMR in many locations across the U.S. due to RF propagation properties and matching LTE to LMR coverage and reliability is just too cost-prohibitive.  

Interference Concerns

FirstNet public safety LTE in the United States will occupy two blocks of spectrum at 758-768 MHz and its duplex spectrum offset +30 MHz away at 788-798 MHz (figure 1). These frequency bands are adjacent to public safety narrowband spectrum for LMR at 769-775 MHz and its duplex pair +30 MHz away at 799-805 MHz. A study conducted by the U.S. Department of Homeland Security suggests that LMR and LTE systems operating at the frequency bands mentioned above can coexist with proper engineering design practices and careful frequency management. Interference issues may still be of concern, however, as the guard band between the LTE and LMR spectra are only 1 MHz wide.

Figure 1

Training

In areas where both LTE and LMR systems are deployed alongside each other, maintainers now must be proficient in two very different technologies. This means additional training for installers and maintainers or possibly even employing two separate crews, one dedicated to LTE and another to LMR.

LTE is a highly complex technology with its variable channel bandwidths and use of both MIMO and OFDMA to support high data rates. Both LTE and LMR systems have to contend with problems such as multipath and fading that degrades signal quality. Handheld test equipment that can deal with both the complexity of testing LTE networks and mapping bit error rate (BER) and modulation fidelity of LMR networks is critical to providing technicians and engineers that install and maintain public safety communications systems with confidence that these networks will work as expected. The Anritsu LMR Master™ S412E (figure 2) is the industry’s first and only battery-powered LMR field analyzer capable of testing both broadband LTE and narrowband LMR. It has all the capabilities to test all the technologies associated with public safety systems.

Figure 2

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 critical to ensuring mission-critical public safety communication and keeping the public safe. To learn more on the challenges associated with them and proper test techniques, download this white paper entitle The Impact of LTE on the LMR Industry.

In-Building Coverage Tests Becoming Increasingly Important with 5G on Horizon

September 29, 2016

Coverage testing for wireless systems is an important part of network and building management, whether the signals are generated by owned equipment located in-building or on-campus, or by provider-owned equipment outside. Coverage testing is a process that begins with planning and continues with equipment setup, test execution, data analysis, and corrective action. The testing process should be repeated periodically, and after major changes such as remodeling and construction.

As we approach the completion of the IMT-2020 requirements and the rollout of 5G networks, coverage testing will be increasingly important. The reason is that in-building propagation of RF signals above 24 GHz is very different than signals from wireless technologies field technicians may be used to testing.

Reasons for Testing

Service Assurance - The performance of a wireless network has an effect on several metrics. Customer satisfaction and loyalty, employee satisfaction and retention, management process efficiency, and IS/IT system performance are all influenced by network quality.

Public Safety & Building Codes - Local governments often require in-building testing of wireless networks for public safety reasons, and for tying the performance of these systems to building codes. The technologies used to construct energy-efficient buildings (primarily low-emissivity glass and radiant-barrier insulation) will attenuate wireless signals. In many locations, conducting an in-building test to confirm performance of radios for police, fire, and emergency medical is required to obtain a certificate of occupancy.

Testing Challenges

RF Signal Performance in Millimeter Wavelengths - In 2016 the Federal Communications Commission (FCC) assigned the 28 GHz, 37 GHz, 39 GHz, and 64-71 GHz bands for use by future 5G wireless systems, and the agency is considering additional spectrum above 95 GHz. These frequencies will present new challenges for performance of in-building wireless networks.

Lower frequencies behave like water in a stream – flowing around obstacles. Higher frequencies behave like visible light – casting shadows behind the obstacle and creating “dead zones.” The RF energy is absorbed by the obstacle, reflected back, or scattered – and this RF energy can combine with the original signal and other reflections to form complex patterns of constructive and destructive interference. This is especially true for obstacles made of metal, and to a lesser extent any material capable of retaining moisture, such as gypsum wallboard, wood, and even fabrics.

Equipment - It’s important to use coaxial cable and connectors designed for microwave frequencies. RG-174 coax cable is rated up to 65.6 GHz; higher frequencies require semi-rigid coax. 1.85mm and V-type air dielectric connectors are rated up to about 70 GHz. Above that point, 1mm air dielectric connectors are required for 5G bands. The test receiver’s antenna should be omnidirectional.

Environmental Simulation - RF signals above 24 GHz are often affected by objects in and around the space being tested. In an office environment, the position of PCs, LCD displays, desks, chairs, bookcases, shelfs, cubicle walls, potted plants, and even people, will affect the coverage. Simulating an in-building RF environment that closely matches an occupied building is hard, so conducting another coverage test after the building is occupied is recommended.

Managing Variables - In-building coverage testing should be done when the interior space is unoccupied to minimize randomization of the signal propagation and measurements. Coax connectors should be torqued to specification to avoid variance, and coaxial cable or semi-rigid cable should be secured to ensure that changes in loss from movement do not cause measurement variance. Directional antennas are not recommended as reflections from objects in the environment will cause measurement variances.

Anritsu has just published a white paper on this topic. It can be downloaded here.

A Suggested Solution to the Public Safety Network Interoperability Issues

July 25, 2016

In April 2016 the FCC issued a Report & Order that mandates use of analog FM for mutual aid and interoperability channels in the Part 90 VHF, UHF, and 800 MHz bands. This is an interesting development, in light of the massive effort by (and funding from) the U.S. Government to make APCO Project 25 the interoperability standard. Yet it’s not a surprise to us – we’ve been saying since 2013 that interoperability isn’t easy.

In March 2013 this blog stated “we’re farther away from interoperability than we were 20 years ago,” and referenced a presentation given at the Disaster Management Initiative hosted by Carnegie Mellon University – Silicon Valley that pointed out that “Not all P25 is interoperable.” Therein lays the basis of the FCC’s Report & Order.

Profits Over Interoperability

Interoperability wouldn’t be such an issue if strict adherence to the TIA-102 standard was mandated, but in an effort to lock customers into lucrative contracts and protect profit margins the radio manufacturers have tweaked P25 in ways that prevents interoperability. Figure 1 outlines the Homeland Security Interoperability Continuum.

Figure 1

Back in 2012 our product management team was contacted by a systems integrator seeking confirmation of field test results found during use of the P25 Bit Capture function in the LMR Master™ S412E. The captured data showed that the P25 Phase 1 uplink data from two different radio vendors did not match, even though each vendor claimed their equipment was standards-compliant. This is just one anecdote of many, and most readers of this blog very likely have similar experiences.

Proposed Solution

Fortunately, there’s a solution. Purchasers of P25 systems and equipment can and should insist on standards-compliance, and either independently verify compliance or require verification by the systems integrator and/or vendor. The LMR Master S412E Land Mobile Radio Modulation analyzer from Anritsu offers P25 analysis tools based on a strict interpretation of the TIA-102 standard, so that any variances found during testing can be recorded and documented as part of a corrective action order.

There are, of course, other reasons for this shift back to analog FM, not the least of which are ongoing issues with “voice codecs in high-noise environments” and issues with “digital cellular sites knocking digital public safety networks off the air.” Some fire departments have installed analog FM repeaters on incident command trucks because in some use cases analog has advantages over digital. The FCC’s Report & Order mandating analog will buy us some time to resolve these and other issues, but we also need to insist on standards-compliance supported by analysis and testing.

A library of technical documents outlining testing public safety networks and ensuring their operation has been published by Anritsu. You can access the full library here.

Will LTE take the place of push-to-talk LMR?

June 20, 2016

With the FirstNet RFP deadline now past and speculation rampant about the outcome, one common question is, “Will LTE eventually take the place of push-to-talk LMR radio?” There are several potential answers, depending on how you qualify it.

Economies of Scale vs Technical Realities

We know the FirstNet RFP winner will have to make an aggressive sales pitch touting the features of the system in order to get buy-in from states and agencies. Unfortunately, many of the decision makers for that buy-in are non-technical politicians and administrators who may not understand the nuances between a Direct Mode LTE handset with push-to-talk using Voice-over-LTE (PTT-VoLTE) and a digital LMR handset with talk-around on simplex channels. They want simple solutions that will allow them to leverage economies of scale – if LTE is good for some use cases, why can’t it be good for all use cases?

Trying to discuss technical nuances with non-technical people is often like attempting to apply shoe polish to a cat – it makes a big mess, doesn’t produce the intended result, and you only end up making the cat angry. So, whether or not LTE actually can replace LMR, decision makers and politicians need to believe that it ultimately can or they won’t buy into the sales pitch and join FirstNet.

Willingness of First Responders to Adopt LTE

LTE was originally designed as a system to transport data – running voice over LTE is fairly new even for large commercial carriers. Plus, features like “Direct Mode” for communications between handsets without a network have yet to be proven in deployment. First responders who rely on radio to keep them safe insist on highly reliable communications, and given that their lives are on the line they have that right.

Some agencies have resisted moving from analog FM to APCO P25 – so it’s unlikely that agencies resistant to digital technologies will give up analog in favor of PTT-VoLTE any time soon. On the positive side it’s likely that features such as Direct Mode and PTT-VoLTE will find their way into commercial handsets and networks, so if they perform well in wide use they may gain more rapid acceptance in public safety.

Adoption of LTE Standards in Equipment

As the 3GPP (Third Generation Partnership Project) adds new features to the standard, the user and network infrastructure equipment must be updated to take advantage of those changes. For FirstNet this won’t be such a challenge, because the network doesn’t exist yet and there are very few handsets in deployment. Of course the equipment used for FirstNet will need for more durable than a standard smartphone, and will need to meet higher performance standards for things such as water resistance, battery life and ease of battery replacement, speaker output level, and ambient noise rejection.

Unlike the commercial world, where carriers and operators delay deploying until they know handsets are coming to market – and handset vendors hold off until they see the carriers and operators deploying updated equipment – we know fairly well what FirstNet is supposed to be, so the RFP winner(s) will begin build-out and FirstNet-capable user equipment will follow. The costs, however, are not insignificant, and agencies that have only recently paid for the transition to P25 will be reluctant to make another costly transition.

Critical Communications vs Operational Efficiencies

Public safety communications networks serve a wide variety of use cases ranging from enabling daily operational and administration functions to providing critical communications for tactical deployments during major incidents. The more critical the incident, the more likely incident commanders will be to demand proven technologies. This is why fire departments that have converted to P25 often retain analog FM channels and install analog repeaters on their incident command trucks – while not the most efficient system, analog is a known quantity proven out over decades and is less prone to complex failure modes. When LTE begins to replace LMR it will first do so in the daily operation and administration use cases, eventually gaining trust in more critical use cases.

Network capacity will also play a factor in this adoption curve. As it exists today, FirstNet’s spectrum in E-UTRA Band 14 is large enough to support a reasonable number of data-only tasks, such as full-motion video and file transfer, but if the incident is very large (e.g. on the order of Sept 11th response with impacts across a large region and multiple agencies) then the system will not be large enough for data. So, reliable PTT-VoLTE will not even be possible – which means that LMR continues to be the tool of choice until FirstNet gets more bandwidth.

Ensuring System Efficiency

Maximizing the efficiency of any LTE system involves analyzing and understanding the network’s performance on the ground, in locations where users are going to be. The Anritsu LMR Master™ S412E land mobile radio modulation analyzer (figure 1) with LTE options is a great tool for conducting this analysis. Field-tough, portable, yet powerful enough to measure critical LTE performance metrics, the LMR Master is designed to support the public safety communications of today and tomorrow.

Figure 1

A white paper on how to effectively test LTE for public safety is now available. It provides insight on how to test LTE broadband and P25 narrowband networks.

The State of Positive Train Control in the U.S.

May 11, 2016

In 2008, a major train collision involving a Union Pacific freight train and a Metrolink commuter train occurred in the Los Angeles area that resulted in over $7 million in physical damage, 135 injuries, and 25 deaths. The NTSB investigation faulted the Metrolink engineer, concluding that he had been distracted by text messages and did not heed a right-of-way signal given by dispatch. In response to the collision, the U.S. Congress passed the Rail Safety Improvement Act of 2008, which mandated Class 1 railroads implement Positive Train Control (PTC) by December 31, 2015.

The mandate applies to all main-line tracks where intercity passenger railroads and commuter railroads operate, as well as on lines carrying toxic-by-inhalation hazardous materials. Recognizing that the Class 1 railroads would fail to meet this deadline, Congress voted in October 2015 to extend the deadline by three years. Part of the reason cited by the Federal Railroad Administration (FRA) for the delay is the complexities of developing technology to implement PTC on the systems. Figure 1 outlines the architecture of PTC.

Figure 1

Technology Crossroads

There are, in fact, several different flavors of PTC, which creates an interoperability challenge on shared track sections. Class 1 railroads are implementing competing systems such as the Interoperable Electronic Train Management System (I-ETMS) and the Vital Train Management System (VTMS). Amtrak is implementing the Advanced Civil Speed Enforcement System (ACSES) on its Northeast Corridor that runs between Boston and Washington, D.C.

Back in 2010, the FRA awarded Amtrak $12.8 million to develop interoperability between ACSES and VTMS; this is being done primarily through equipment duplication – where an ACSES system is installed alongside the VTMS system. Amtrak is also implementing the Incremental Train Control System (ITCS), initially on its Michigan Line. Caltrain, a passenger railroad in the San Francisco Bay Area that shares some track with Class 1 railways, is implementing the Communications Based Overlay Signal System (CBOSS).

Why all the complexity? First and foremost, the Rail Safety Improvement Act of 2008 was an unfunded mandate – Congress initially did not provide financial support for PTC. It’s estimated that the railroad industry has invested over $500 million to date on developing the hardware and software necessary to implement PTC, and a 2010 report commissioned by the American Association of Railroads (AAR) projected the total cost to develop PTC to be as high as $13 billion over 20 years. In general, these systems are either evolving from existing work (already in progress prior to the 2008 accident) or have been created from scratch.

A Speed Issue

Another challenge is that PTC systems have differing capabilities. The Class 1 railroads’ I-ETMS system does not work above 79 mph – not an issue for freight trains, but some passenger lines operate at higher speeds. Amtrak’s ITCS system tops out at 115 mph – which is fine for existing passenger lines, but the proposed California High Speed Rail service will reach 220 mph on tracks between San Jose and Los Angeles, and the CA High Speed Rail will share tracks with Caltrain.

Finally, developing and implementing PTC in the U.S. has been challenging because there’s not a clear allocation of spectrum for the system. PTC in the I-ETMS and ITCS systems is using a small segment of the 220 MHz band and won’t support data rates above 9,600 bits-per-second. Other PTC systems use both licensed and unlicensed spectrum, allowing for higher data rates. It’s clear that implementation of PTC in the United States is far from a done deal. We’re likely to see more changes in the years to come, as each railroad works to meet the congressional mandate and develop a system that serves its individual needs.

Another aspect is how to test these systems. PTC radio system project commissioning teams from several different railroads are using their own individual approaches, with no final testing procedures defined. One potential universal methodology uses existing test solutions, such as the Anritsu LMR Master™ S412E, as well as different instrument configurations and PTC radios. To learn more about PTC radio systems and this proposed testing approach, download a free PTC testing application note.

Innovative 3D System Revolutionizes Public Safety In-Building-Wireless System Testing

April 27, 2016

Public safety networks have evolved quite a bit over the past decade. This goes beyond the conversion from analog networks to digital LTE systems. Just a few years ago, public safety communications were predominantly based on powerful, external high site transmitters that supplied sufficient signal levels to reach into buildings. Modern energy efficient construction and increasing reliance on anytime, anywhere communications have changed all of that, requiring Distributed Antenna Systems (DAS) to be used. Proper DAS installation and operation is integral to ensure first responders can communicate in any mission critical situation.

Improvements to public safety networks have meant that test solutions must evolve as well. One advancement that was introduced at IWCE 2016 last month is a 3D in-building coverage mapping solution (figure 1). The system provides a new level of testing capability to ensure proper installation and operation of in-building wireless (IBW) networks used by public safety agencies. It exceeds the capability of any alternative on the market, especially in testing areas that have traditionally posed significant challenges, such as stairwells.

Figure 1

Developed by Anritsu and TRX Systems, the system provides coverage maps based on RF measurements taken with Anritsu handheld analyzers such as the LMR Master™ S412E. The TRX NEON® Signal Mapper application provides an Android user interface so in-building measurements can be made at specific locations. The NEON Command Software allows users to import floor plans with grids to support mapping procedures per NFPA 72 and NFPA 1221, the wireless communication standards developed by the National Fire Protection Association (NFPA).

Technicians now have an easier and more effective testing method. They simply watch the display of their Android device while wearing the small NEON Tracking Unit attached to the their waist (typically on a belt) equipped with a gyroscope, accelerometer, pressure sensor, compass, and various other sensors. RF measurements taken with the handheld analyzer are sent via a USB connection and location information from the NEON Tracking Unit sent via Bluetooth to the NEON Signal Mapper application on the Android device, which then couples this data together to provide 3D geo-referenced RF coverage results.

System Setup

The first step in using the system is to create maps, which can be done in three simple steps.

1. Convert building floor plans to a graphics format, such as a .jpg, .bmp, or .gif file. If desired, a grid layout can be superimposed on the floor plan image. A walking plan could be superimposed, as well, if there are obstacles that need to be avoided. Once the floor plan image is finalized, it can be loaded into the NEON Command Software for mapping.
2. Enter building addresses into the NEON Command Software so the building map can be viewed on a PC screen.
3. Create the outline and add the proper number of floors for the building to be mapped in the NEON Command Software.
4. Import the floor plan (with the grid/walking path) for each floor to the building.

The next phase begins by placing the S412E handheld analyzer on a cart and connecting it to a quarter wavelength measurement antenna three to four feet above the floor level and an equal distance from the operator. The Android device is connected to the S412E via a USB OTG cable to transfer measurements into the NEON Signal Mapper software. A NEON Tracking Unit must be worn around the waist of the operator and connected to the Android device via a Bluetooth connection as well.

Making Measurements

Once the system has been configured using the steps outlined above, the public safety operator simply follows the location calibration procedures shown on the Android smart phone or tablet to conduct measurements. The operator follows the specified walking plan by observing the location on the Android device. When finished, the user uploads the measurement results with locations to the cloud or saves it on the smart phone or tablet.

Measurement results can be reviewed in 2D or 3D using the NEON Command Software, which also provides a heat map display that uses a measurement average to predict coverage around the walking path – helping to ensure in-building network coverage. A comma separated file can also be generated with results and location information for each measurement.

This new system by Anritsu and TRX Systems provides users who must verify public safety networks with a powerful in-building mapping solution. They can now make measurements and create detailed maps and reports of in-building coverage more easily and accurately to verify network coverage and help ensure safety of police, fire, EMS and other first responders.

To learn more, download a free application note from Anritsu.

How Remote Monitoring Can Help FCC's Enforcement Efforts Against Pirate Radio

February 18, 2016

In January 2016 the Federal Communications Commission (FCC) notified three unlicensed FM broadcasters ("pirates" is the popular term for these denizens of the electromagnetic Wild West) in the Bronx, one of New York City’s five boroughs, that they must immediately cease transmissions. This is part of the FCC’s commitment to step up enforcement against pirate radio broadcasters. Chairman Tom Wheeler said late last year that shutting down unlicensed broadcast stations is a priority and asked Congress during a House Energy and Commerce Committee oversight hearing for legislative support against pirate radio. Wheeler’s efforts against illegal broadcasters were apparently in part a response to a letter from Senators Charles Schumer (D-N.Y.) and Kirsten Gillibrand (D-N.Y.) urging the FCC to take action.

This seems odd given that in mid-2015 the FCC published a draft plan to close nearly a dozen field offices and eliminate nearly four dozen positions in their Enforcement Bureau – the same unit that goes after illegal broadcasters. Wheeler noted that the reductions were spurred by increased budgetary pressure from lawmakers. “Congress has ordered that we spend less,” he said.

Aside from their basic illegality and the interference potential to licensed commercial broadcasters, pirate radio stations are typically hand-built or use cheap components purchased offshore. The result is they generate significant interference to nearby bands – including aeronautical users (figure 1). It’s not surprising that even given limited resources the FCC is focusing on enforcement against pirate radio stations such as the aforementioned – those stations in the Bronx were directly under flight paths for nearby LaGuardia Airport.

Figure 1: Aeronautical bands, critical for traveler safety, are located just above the FM broadcast band.

The FCC is in an unenviable position – Congress wants more enforcement, but doesn’t want to pay for it. Clear aviation communications between aircraft and flight controllers near busy metropolitan airports are critical – a missed instruction could result in loss of human lives. Monitoring for interference from pirate radio in aviation bands is critical to determine if immediate action is needed, but barring increased funding for people can the FCC resolve this dilemma?

Possible Solution: Remote Monitoring

Remote monitoring systems offer a possible solution. A network of remote monitoring stations combined with a control dashboard system is less expensive than adding headcount. It multiplies the value of field engineers by allowing them to “travel” instantly to affected areas and view real-time spectrum behavior, and to make simultaneous measurements in several places at once (figure 2). Spectrum recording tools allow engineers to “go back in time” and view spectrum events that occurred during off-duty hours, and to see the spectrum as it existed at the time complaints were logged.

Figure 2: Remote monitoring software allows for the geo-location of signals on a map overlay.

Being able to receive automated alerts is also useful – especially in the case of pirate radio monitoring where FM broadcasters in crowded markets are assigned to channels 400 kHz apart – and pirates often transmit on the “unused” channels between legal assignments. By setting up a trigger that generates an email or text message when a signal is received on a buffer channel, field engineers can know instantly when a pirate station is on the air. And while tracking stations to their exact location is still done by field engineers, a network of remote stations can provide initial guidance via triangulation estimates – saving time and travel costs.

Pirate radio detection is just one of many applications for remote spectrum monitoring. Ways in which these tools can help ensure wireless networks are detailed in a free application note.

A Multi-Technique Approach is Critical to Successful LTE Testing

January 14, 2016

Engineers and technicians responsible for the performance of LTE systems are increasingly faced with challenges brought on by the complexity of modern wireless networks, such as multiple cellular data frequency bands, increased usage and number of subscribers, and network densification. The industry is shifting from macro cells to small cells and DAS testing is becoming more complicated.

At the same time, the rapidly-increasing use of wireless technology for consumer and enterprise or infrastructure applications can generate RF noise that adversely impacts LTE systems. Given these complexities, a practical approach to LTE testing must be flexible and allow the engineer to combine several techniques depending on what’s being tested. These techniques can be roughly classified as Direct Analysis, Remote Analysis, Active Monitoring, and Passive Monitoring.

Direct Analysis

Direct Analysis is the classic test and measurement model: parametric analysis of the RF, signal, and protocol aspects of the LTE system under the direction of an experienced technologist. This could be as simple as measuring the RF signal power or channel power, a more complex signal analysis of the Physical Broadcast Channel Power level, or a complex protocol analysis such as viewing the Power Versus Resource Block allocations in real time, as shown in figure 1.

Figure 1

Measurement of RF levels is useful for rough estimation but can be misleading if there’s undesirable RF energy from other sources. For this reason, signal and protocol measurement is a better approach because it shows the performance of the desired signal in the presence of noise. Measurement of the Reference Signal Received Quality (RSRQ) is defined as the ratio of the Reference Signal Received Power (RSRP) to the channel Received Signal Strength Indicator (RSSI) measured over the same bandwidth. RSRQ gives a good sense for performance in the presence of ambient RF and can be used to calculate other performance metrics.

Remote Analysis

Remote Analysis is done via unattended recording and post-recording analysis of RF, signal, and protocol measurements. It can also involve remote spectrum analysis systems that allow monitoring of spectrum and alerting engineers when signals exceed preset levels and masks. Remote Analysis is typically done by experienced technologists in an effort to confirm and maintain baseline performance, or diagnose specific problems.

Figure 2: Anritsu Vision dashboard showing multi-site display and a spectrum w/ limit mask

Active Monitoring

Active Monitoring is much like Direct Analysis except that it’s typically conducted with an automated system designed to collect data on various performance indicators. An example of an Active Monitoring system is “Drive Testing” in which an analysis system (either test equipment or custom-modified user devices) is installed in a vehicle that collects and records location-tagged performance measurements as the vehicle moves about. Active Monitoring does not necessarily require operation by an experienced technologist; although when hunting for specific problems, Active Monitoring can be a useful tool for engineers.

Passive Monitoring

Passive Monitoring is typically done via apps or processes that reside on user devices, usually smartphones and tablets. Passive Monitoring could be termed “Crowd-sourced Monitoring” in that it relies on aggregated data from a large number of user devices to build a database of performance metrics over a mapped area. There are several problems with this technique, notably that the performance of any given user device can vary depending on how it’s being carried (openly, in a pocket or purse, in a vehicle, etc.) and the radio performance of user devices can vary between manufacturers and model numbers. Nevertheless, the value of Passive Monitoring as a source of information should be considered. Consistent performance problems shown by Passive Monitoring data will indicate that further analysis by Active Monitoring and Direct Analysis is needed.

Application notes on techniques to test public safety networks and ensure performance in the most mission critical environments is available from Anritsu’s online technical library.

States Opting Out of FirstNet National Network Emphasizes Importance of Testing

December 4, 2015

In October, FirstNet released its final legal interpretations on the ability for a state to “opt out” of FirstNet and build its own LTE radio access network (RAN) within its borders. While there has been much discussion on the topic – including an APCO 2015 session on the efforts made by FirstNet to drum up support within states to stay in – it has centered almost solely on economics. One other key factor is compatibility of the state RAN with the nationwide mobile broadband public safety network FirstNet is developing.

Back in August at the APCO show, Amanda Hilliard and Dave Buchanan of FirstNet spoke about the actions taken by the organization to gain the approval of each state for the nationwide mobile broadband public safety network. At the time of the show in Washington, D.C., they had conducted 46 meetings yet still had nine more states to visit before their September 30 deadline.

Shortly after that deadline passed, the FirstNet board gave its legal interpretation on states opting out of the national network. Most of that clarification centered on any excess revenue generated by public safety networks built and operated by those states that opt out. FirstNet stated they should receive those funds, which will be used to help build out the emergency-communications system in the rest of the country, just as FirstNet would do if it were deploying the network in the respective jurisdiction.

Despite the red tape that FirstNet has wrapped around the ability for a state to opt out, some governors are still considering it. The reason is simple – that excess revenue. While FirstNet is stating the money should be used to build the national public safety network, state officials claim that they should be able to keep those funds to make their networks more robust and reliable.

More Than Money

While that discussion will be waged, the other key point – that the state network must connect seamlessly with the broader FirstNet nationwide LTE system – seems to be placed on the back burner. Another discussion point from the APCO session led by FirstNet spokespeople Hilliard and Buchanan that is seemingly being tabled is the coverage challenges. The latter point was one of three key areas highlighted by the 40-member Public Safety Committee established by FirstNet, with the others being the use of mobile broadband and current capacity usage.  

Seamlessly connecting to the nationwide LTE system and ensuring coverage will ultimately be more important than revenue. After all, no amount of money can justify a public safety network failing during a mission critical situation. Addressing these two factors during network deployment is only the first part of effective urgent communications. Maintaining the performance of the network is equally important.

Testing Will Be Key

As targeted as the needs of public safety are, the field test instrumentation that is required to ensure seamless connectivity and coverage must be equally specific. Analyzers used for FirstNet deployment should be handheld multi-function instruments that address the needs of technicians and engineers who will install and maintain the networks, whether it is a state-operated RAN or the national broadband network.

These Land Mobile Radio (LMR)-specific analyzers (figure 1) will need to support the analysis and testing of narrowband FM radio systems and integrate coverage mapping of RSSI, transmitter SINAD, and transmitter THD. They will also need to support digital LMR standards, such as P25 (TIA-102.CAAA-C), P25 Phase 2 (TIA-102.CCAA), NXDN™, ETSI DMR Tier 2(MotoTRBO™), ETSI TETRA, and PTC.

Figure 1

Connecting state-run public safety networks from those that opt out of FirstNet with the nationwide mobile broadband network will be vital to the safety of first responders. Using the proper test solutions during deployment of the network will be an important step to ensure operation in any situation.

Learn more about testing public safety LTE broadband and P25 narrowband networks by downloading a free white paper.

Next Generation 911 Deployment Needs to Hit the Express Lane

October 22, 2015

The annual APCO show had plenty of sessions and presentations that were of great interest to public safety professionals. Perhaps no speaker was more anticipated than Federal Communications Commission (FCC) Chairman Tom Wheeler, who voiced his opinion on the current state of next-generation 9-1-1 (NG911). Like so many of us involved in public safety, the FCC chair feels the pace of NG911 is too slow and needs to be expedited before the safety of police officers, firefighters, emergency response personnel, and the public in general is put at risk.

Speaking to members of the nation’s largest public safety association, Wheeler made it clear that while there is much to be encouraged about in terms of technology and the adoption of new rules – including more focus on text-to-9-1-1 service, improving the accuracy of location data in wireless 9-1-1 calls, and 9-1-1 system reliability – a lot of work still must be done. Most notably, Congress must step in to accelerate the process with legislation designed to help move forward the essential shared mission of public safety.

In the four months preceding APCO 2015 in August, the FCC issued nearly $40 million in penalties for outages that left millions of people unable to reach 9-1-1 for hours at a time. As Wheeler plainly put it, “I cannot imagine a more harrowing experience than desperately needing to call 9-1-1 because a loved one needs medical attention – only to pick up the phone and hear nothing.”

To prevent that from ever happening, Wheeler spoke of a federal task force that is expected to establish guidelines before the year-end for public safety answering points (PSAPs) migrating to NG911. Wheeler had more to say about PSAPs, specifically how the federal government should get involved in the national mapping process. We agree that the maps our PSAPs use to identify the location of callers can’t stop at the county or state line. The RF spectrum that carries emergency messages doesn’t understand geography, so we shouldn’t be confined to geographic boundaries developed decades ago.

Funding NG911

Wheeler (pictured right) said local municipalities must resist the temptation to take funds intended for improving NG911 and diverting it for other programs. Along those lines, a few weeks after Wheeler spoke, the National Association of State 911 Administrators published a white paper that outlined several funding models states have at their disposal when planning how they will support the rollout of the IP network. The group offered four suggestions:  

• Keep the current funding model and add fees for prepaid wireless and other services
• Impose a general sales tax
• Add a fee to health insurance plans
• Use a state universal service fund

Those were two of the main NG911 themes discussed by Wheeler and there is some synergy between the two. As Wheeler noted, maintaining two infrastructures (legacy and NG911) increases costs and complexities. The sooner the transition can be fully made, the better off everyone will be. It is our current interim period that is a big concern.

To ensure communications are not lost, it will be imperative to maintain the quality of both legacy and next generation networks. That will require test tools that can conduct measurements on both analog and digital signals. While that sounds as if multiple instruments (read: extra cost) will be necessary, it is not truly the case. The LMR Master™ S412E Land Mobile Radio Modulation analyzer can address both network scenarios. It is the only truly portable solution for analysis and mapping of P25 TDMA Phase 2, ITC-R Positive Train Control, and FirstNet Public Safety LTE, providing a durable single-instrument solution to the legacy/next generation 911 testing dilemma.

With handheld tools such as the LMR Master, issues associated with public safety networks can be monitored and corrected before they result in dropped calls that can jeopardize the safety of public safety professionals and the citizenry. An application note on measuring signal strength of P25 networks is available that can provide insight on reducing such a possibility.