A Knowledge Gap

Incident Communications Part 2

It appears as though the engineers and technologists working with the FCC’s Public Safety and Homeland Security Bureau (PSHSB), some within the FCC Commissioner’s office, and many staff members serving our congressional representatives do not understand the basics of wireless communications or, more specifically, the differences between commercial wireless voice and Land Mobile Radio voice systems.

This knowledge gap was evident to me during my recent trip to Washington DC and again when I saw that the PSHSB was preparing to issue a Public Notice on converting the 700-MHz narrowband voice frequencies for public safety to broadband usage. This spectrum (769-775 MHz and 799-805 MHz) was previously allocated for channelized voice communications systems using digital technologies on very narrow voice channels. Within this portion of the spectrum there are 1920 (2 blocks of 960 channels each) voice channels for use by public safety.

Those preparing to float this Public Notice don’t seem to understand several facts. First, broadband service for images, video, data, and other applications is desperately needed by the public safety community. HOWEVER, broadband services CANNOT replace all of the various requirements for voice systems, nor can LTE or any other commercial wireless technology provide all of the types of voice services needed by public safety.

Nor do these people understand that no matter how robust the broadband networks, no matter how much spectrum the public safety community has, its needs for different types of voice usage CANNOT be satisfied by LTE ( see part 1) or any other broadband technology. Even with the best broadband system in the nation, voice will remain a critical element of public safety communications.

So let’s start at the beginning:

  • Public safety voice services are varied. When a call is received by a call taker (PSAP operator), it is transferred to a dispatcher who puts the call out as a voice message on the dispatch channel. The dispatch channel is monitored by field personnel and it is important that the dispatch is heard not only by the units that will be responding to the call, but also by every other unit that is in the same district or area. This type of communications is based on push-to-talk, not dialing a phone number, and while it is a directed call, it is important that everyone else on the channel, including the commanders in the field, hear the call so they know what is happening in their area of responsibility.
  • The unit or units that will be responding to the call answer the dispatcher and start toward the incident. On their way, they could receive additional information either by voice or data. They might receive information about prior calls at the same address, if the subject is armed or there is a gun on the premises, or any number of other things that will help them evaluate how to approach the incident. Once they arrive on the scene, they notify the dispatcher and this communication is also heard by all others on the channel.
  • After that, several things happen at the same time. If the call is for police units, the dispatcher will start a timer giving those responding a set amount of time to re-contact the dispatch center and verify their safety. Once those at the incident have had time to assess the situation, they call into the dispatch center with an initial report and if they need assistance, they request it. Since the others in the field have been listening to the voice traffic, they may have already started moving closer to the scene so they can respond faster if they are needed for backup. Once again, this is automatic based on hearing the voice traffic for the call.
  • If the responders do not check in with the proper radio code within a specified period of time, the dispatcher calls them, again with the other units listening in. If there is still no answer, additional units are dispatched to the scene to check on them.
  • During this time, the dispatcher may also be receiving additional information about the call and relaying it to those in the field. In many cases, another officer has some firsthand knowledge of the address or people involved and will also contact those responding to the incident or on the scene to provide that information so they can be better informed about the situation.
  • During the incident, those on the scene are reporting back to the dispatcher and the conversations are being heard by others in the field as well as the commanders who are on duty and usually also on patrol.
  • Once the incident is cleared, those in the field respond to other incidents in the same manner. On a busy night, the dispatcher may be handling up to 50 or 75 cars or more on a single radio channel and making sure all of the calls are being handled in order of priority.

This scenario is standard operating procedure for public safety. If the incident had been a fire, the first unit on the scene would report a condition such as: two-story residence, flames showing on the second floor. Those responding in other units would hear the report and begin preparing to take directions from the incident commander (IC) as they approach the scene. In the meantime, the incident commander has heard the initial dispatch and knows what equipment is heading toward the scene. He or she sizes up the situation and may order a second alarm, but in any event, the IC knows how many and what types of apparatus are inbound and starts giving orders over the voice network. Perhaps one engine will come to the scene, the next engine will hook up to a fire hydrant to provide water, the rescue company will come onto the scene and be prepared to search the house, and the ladder company will also come to the house and set up to gain access to the second floor or to use its hose from above the roofline to battle the fire. The EMS vehicle might be next in and positioned so it can provide medical services to anyone injured, including firefighters.

Such scenarios are standard everyday occurrences and this is the type of voice activity the FCC and others believe can be handled by broadband networks in the future. This may be the case, but the issues will be how to enable the broadband network to provide one-to-many voice communications covering only a specific area, but having the additional instant ability to broaden the area of coverage for larger incidents. Further, the devices MUST have push-to-talk in them, and they must have speakers so the handheld can be worn and used with a single hand. Even when it is not being held, the voice messages coming from the handheld’s speaker have to be heard by the person in the car or wearing the device. So now this begins to sound a little different from standard broadband communications services.

In the standard broadband world, the voice devices are designed for handheld operation and you must dial a number in order to communicate. Dialing a number connects you to a single person to talk to and does not connect you to many people at once. Further, you must use two hands to dial the number. You cannot expect a public safety first responder to use two hands for any form of communications unless it is to quickly turn a knob to change channels. There is no way a public safety field officer is going to use a device that takes two hands to operate. Next, of course, is the time it takes to dial a call. You have to select the number or remember its speed dial position and then dial, wait for the network connection and then the ring, and then wait some more until the person answers the phone. Compare this to today’s public safety communications where you depress a push-to-talk switch and talk, and within less than one-half of a second, your voice is being broadcast not only to the dispatch center, but to every field officer in your district or area.

If you are being shot at or are inside a burning building, you have time for one call for help. You need to make it quickly AND you need to know it was heard, not blocked because the network was busy at that moment. Dropped calls are NOT acceptable in public safety communications. This is one reason there are rules governing radio usage and the dispatcher or incident commander is charged with maintaining what is called “network discipline,” making sure traffic gets through all of the time, every time. They cannot tolerate a single dropped or blocked call; it could cost someone their life.

Will LTE be able to address these issues in the future? The answer is probably yes since the LTE specifications address the use of push-to-talk and Voice over IP (VoIP), and the specs refer to one-to-many or broadcast communications, although it is not yet clear if the LTE broadcast mode could be limited to only certain cell sites within a given city. The systems would need to be set up to support multiple broadcast sessions simultaneously since most public safety agencies use multiple dispatch channels based on geographic or other sets of boundaries.

A typical major city might have eight or ten different dispatch channels, each designed to provide coverage in a given segment of the city, and another citywide channel for commanders. All of this consumes bandwidth and all of these systems have to be up and running 24/7 with instant or near-instant push-to-talk capabilities.

The field units need to be able to move from one coverage area to another. The way this is handled today is to manually switch the channel or, in some cases, listen to one or more channels all of the time by scanning them. With the main channel set for priority, if they are listening to voice traffic on another channel and a call is received on their primary channel, the radio automatically reverts to the primary channel so the transmission can be heard in its entirety.

There are those who believe that public safety can make do with other ways of communicating, but they must understand that field personnel might have only a few seconds to call for help in an emergency, and they need to know with 100% certainly that their call will be heard. It makes more sense to use LTE voice capabilities when they become available in a few years for administrative and non-mission-critical voice communications while leaving the existing voice systems in place. One advantage a public safety broadband network will provide is that some of the voice traffic that can overload the system at peak hours can be moved to data requests and responses. This includes running license plates and drivers’ licenses, uploading accident reports, and receiving additional information while in route to an incident.

There is much more to public safety voice communications that cannot be addressed using a broadband network. It is in these areas where the lack of understanding of the public safety community’s needs could result in reducing effectiveness even when adding more capabilities. I will address these requirements in more detail In Part 3 of this COMMENTARY. Stay Tuned!

Andrew M. Seybold


1 Comment on "A Knowledge Gap"

  1. Nice job. Let me add a few things:

    * In public safety, PTT is king. As you pointed out, it is “one-to-many” voice communications. Since the Feds like to toss around acronyms, here’s a new one: ISA: Immediate Situational Awareness – that’s the immediate voice comms for a cop’s safety status at a domestic, or a firefighter’s size up when arriving as a working fire. The other “data stuff” can be SA: Situational Awareness, but it takes a little time and interaction to piece it together.

    * One of the latest buzz-topics is paging for firefighters when a comm system goes to a TRS. Some slave a conventional VHF or UHF channel to a Talk Group for multi-cast notification. However, some are talking actively about text-messaging for both initial response (call-back) and ongoing status reports (SitReps). Has any consideration been made that text messaging is largely unlawful when operating a motor vehicle? How will a volunteer or career (call-back) firefighter get a timely SitRep while attempting to read a text message enroute to the station? Oh, issue a $5,000 TRS portable to everyone? OK.

    * Lastly, the dust-up over LTE is getting a little old. You can’t (yet) do voice PTT, it is not friendly (yet) with one-to-many, and there seems to be no central focus for hardware form-factor or even applications that make sense for public safety. We seem to want to get there fast with no roadmap. Can you see the train coming? If each firefighter carried a TIC with LTE link to an IC, how much bandwidth would be needed, who would control it. (If a manufacturer is reading this and pushing LTE for public safety and does not know what a TIC is, or IC, please get out of the business…..now.)

    I will now practice my well-honed “duck and cover” techniques and don my FLAK jacket and Kevlar helmet.

    All the best Andrew!!!!

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