Police Walkie Talkies: From Primary to Backup

Public safety was the first major non-military user of Land Mobile Radios (LMR).  Even now, many voice communication systems still use analog radios. Since analog radios cannot share radio spectrum, each agency uses multiple frequencies for dispatch and tactical communications.  To avoid interfering with nearby agencies, police, fire and EMS operate on their own frequencies.  So long as field personnel only talk to other personnel within their agency, analog radios are satisfactory.

Inexpensive high-powered hand-held analog radios can punch a signal through buildings.  Three to six watt hand-held radios have a range of several miles depending on geography and structures.  Car radios, which are ten times more powerful and have better antennas, have a range of as much as 30 miles. 

Most law enforcement agencies have been able to provide almost 100% coverage of their jurisdiction using point-to-point communications between mobile radios and between mobile radios and their command centers.

Analog radios have another advantage over digital Project 25 (P25) digital radios.  Voice communications degrades gracefully as signal strength decreases or noise/interference increases.  Even when one cannot hear the other person perfectly, analog signals are often still intelligible, and in the worst case simple communication is possible with key clicks.  In addition, analog radios introduce no delay (latency) in hearing people speak.

Analog Is Not Perfect

However, analog radios are not perfect.  Agencies in the same locality often have incompatible radios that cannot communicate.  Even when the radios can communicate, policies on the purpose of the various channels are not the same at different agencies, which can result in communications failures.  Analog radios offer no way of knowing if anyone is listening, and if they are not, where to transmit to be heard.  More often than we care to admit, people are not heard – sometimes with tragic results.

Even when people are listening on the right channel, life and death communications can be missed.  Personnel unintentionally step on each other’s communications, and senders have no immediate feedback that they were not heard.  Moreover, one can be heard, but the import of the message not recognized.  LMR channels often have many people speaking on the same frequency, and it is possible for listeners to mentally merge messages with resulting dangerous misinterpretations. 

For example if one person says “Help, I am in serious trouble” and the next person to speak says “The lights just went out.”  The message could get merged in listeners’ minds, causing them to perceive the situation as critical, but perhaps not life threatening.

After the communications failures on 9-11, agencies at the local, state and federal levels reevaluated their wireless systems, and many concluded that it was time to go digital.  Over the last decade, the transition from analog to digital proceeded at a snail’s pace.  However, beginning January 1, 2013 the Federal Communications Commission (FCC) will require that public safety LMR reduce its bandwidth from 25 kHz per channel to 12.5 kHz.

P25 has a well-deserved reputation for not working in situations where analog LMR is noisy but still intelligible.  The P25 digital voice standard was already 12 years old when it was selected to replace analog LMR.  While it was appropriate for the slower hardware that was available when it was first developed in the late 1980’s, modern hardware could support an updated P25 standard with better error correction. 

In addition, P25 compliance does not guarantee compatibility with P25 equipment made by other manufacturers.  Despite its limitations, P25 will almost certainly be the narrowband voice communication standard for the next 10 to 20 years.

4G LTE Broadband Solutions

The rollout of mobile cellular communication to the public began in the 1990’s.  Initially, it provided just voice; but soon cellphones started providing digital data services.  We are now beginning the fourth generation of mobile digital data services, with the dominant technology being the Long Term Evolution (LTE) standard. 

LTE offers data rates, both uploading and downloading that are more than ten times faster than third-generation (3G) cellular. Despite having high data rates, the initial release of LTE, is not entirely suitable for mission critical voice communications because it was designed to provide data services such as e-mail, internet and streaming video. 

The Voice over LTE (VoLTE) standard is in development, and is likely to eventually transform mobile voice from switched-based to Internet Protocol (IP) voice, just as has already happened for our landlines.  However, LTE has two major limitations which could jeopardize mission-critical voice and make it unsuitable as the only voice option for public safety.

The first limitation is power.  A single LTE channel requires as much as 20 MHz of bandwidth, versus the 12.5 kHz used by current generation P25.  Because LTE can use 1,600 times as much spectrum as P25, it is necessary to minimize the geographical area that each transmitter uses to avoid interference. 

Consequently, LTE mobile devices are restricted to 0.6 watts by FCC regulations.  Public safety personnel need more powerful transmitters that can be heard when they are inside buildings or not close to a tower.

The second limitation is the inability of current generation LTE devices to communicate directly with one another in the absence of cellular towers. This is referred to as “talk around.”  If the towers are unreachable, either because they are out of range or have been knocked out, police, fire and EMS personnel still must be able to communicate.

LTE as Primary - P25 as Backup

P25 LMR offers higher power than LTE and talk around, but has minimal data services.  When LTE works, it provides high-quality voice and high-speed data services that enable highly useful command and control and situational awareness capabilities.  The capabilities of LMR and LTE are complementary.

Motorola and other manufacturers have added Bluetooth capabilities to their P25 and LTE devices to allow them to share data.  This opens the possibility of using a single microphone for both devices and automatically having it transmit voice over LTE when a broadband connection is available and switch to the narrowband P25 for both voice and data when only the LMR works.  In this way the venerable walkie talkie provides a necessary backup to the LTE device.

When many people share a single channel, critical messages can get missed.  Analog and P25 LMR rely on there being a reliable connection when the voice message is transmitted and that the intended recipient be on the same channel and listening when the message is sent.  In many cases this is not the case. 

Consequently, during operations one often hears requests that transmissions be repeated, and sometime important messages are missed.  At the Foothill-De Anza Community College District Police Department we have been testing a new technology that eliminates these problems and adds new capabilities.

Rather than relying on there being a connection when each person speaks, each voice message is stored as a series of small files on the speaker’s device, the files are transmitted when a connection is available, and played back on the receiver’s devices as they are received.

This architecture has several advantages over normal voice. First, voice transmissions always get through and with perfect fidelity.  If there is no connection, or the connection is noisy, the transmission is delayed, but it will eventually be heard.  Under normal circumstances when the connection is good, the voice gets through with no more delay than Voice over Internet Protocol (VoIP). 

Second, messages can be instantly replayed by any device.  It is no longer necessary to ask for retransmission.  Third, all transmissions contain the location when transmitted (i.e., they are “geo-tagged” using the devices’ GPS) and time-stamped.  This information can be extremely useful during incidents or afterwards at after action reviews.

Pushing Critical Information to Personnel

Command center personnel such as dispatchers often have a more complete view of what is happening then the on-site personnel.  It can be difficult to convey this information by voice. 

Smart LTE devices offer the opportunity to put more critical information in the hands of on-site personnel so that they have access to information such as pictures, streaming video, maps and locations of public safety personnel and 911 callers, text messaging, access to databases containing information such as license plates lookup, names of residents including outstanding warrants, and prior calls to same vicinity and guaranteed voice communications.

Over the last year, the Foothill-De Anza Community College District Police Department has been testing Covia Lab’s Alert & Respond™ command and control and situational awareness program, which integrates these capabilities into a powerful simple-to-use application. 

Initially, we started out running it on PCs in our dispatch center and HTC Imagio smartphones running Windows Mobile for officers in the field.  We then added iPhones (iPhone 3GS’s which were upgraded to iPhone 4’s), and finally moved to HTC Thunderbolt smartphones running Android, because they supported faster LTE networking.

Real-time Information Sharing

Foothill-De Anza often has major political figures, earlier this year Tony Blair, came to our campus.  The campus police force provides security, often in cooperation with the visitor’s security personnel.  This requires sharing information in real-time, and the system must be simple enough to use with no prior training. 

In other words, it has to be as usable as a well-designed smartphone application.  Moreover, once the event is over (or during the operation if a person leaves the detail), we must be certain that all access to operational data has terminated for the visiting personnel.

We initiate operations with external agencies by sending e-mails or text messages containing a link to our servers.  The visiting security personnel click-on on the link to download a copy of Alert & Respond to their PC’s and mobile phones.  Since the system operates on Windows, OS/X and Linux PC’s, as well as many smartphones, compatibility has not been an issue. 

Each person gets a copy of the program and security credentials that are specific to them as well as being specific to the operation.  The data within the operation can only be understood by people in the operation, and members of the operation cannot access data outside the operations.  Each operation is its own secure enclave protected by encryption that is in-process for FIPS-140-2 certification.

Bringing External Agencies Up-To-Date

A useful characteristic of this system is that it intelligently synchronizes data to all devices participating in the operation.  During the Department of Defense’s Coalition Warrior Interoperability Demonstrations (CWID), a hazardous materials attack on Colorado Springs was simulated.  The event started out with local responders, escalated to the state police and the local airbase.  When it was decided that it might be a terrorist attack, the Joint Forces Command (JFCOM) got involved.

In the past, bringing JFCOM up to speed would have been done almost entirely verbally, which would have been incomplete as well as taking a long time.  Instead JFCOM was e-mailed a link to join the operation and all of the historical voice data, text messages, pictures, and Blue Force Tracking GPS data were uploaded to their computers so that they had a complete detailed picture of what had happened before they joined the operation.

Ready for “The Big One”

The Foothill-De Anza campus is located almost directly on the San Andreas fault-line.  Therefore, we have had to be prepared for an earthquake that will require coordination with other local and state public safety agencies, the government and the public.  We constantly train for major disruptions.

It is of great concern that the systems and procedures used during major events are only implemented on rare occasions, so that when something major happens we may not be sufficiently familiar with the interoperability tools at our disposal that are needed to coordinate with other federal, state and local agencies.  Fortunately, the system that we now use for everyday activities can scale to provide the command structure and situational awareness needed at all levels of the command chain no matter how large the event.

Covia Labs has been improving the system, and with our input and the input of other agencies which Covia Labs is collecting as part of a Department of Homeland Security, Science and Technology project, we are confident that we have a system that improves our performance and prepares us for the challenges ahead.

Ronald J. Levine is the Chief of the Foothill-De Anza Community College District Police. David E. Kahn is the CEO of Covia Labs, Inc.

Published in Law and Order, Feb 2012

Rating : Not Yet Rated

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