Big Differences in Voice

About now, many who are convinced that broadband is the only wireless technology we need going forward will be saying that broadband services will be able to handle all of the Public Safety voice communications described in the first two articles in this series. I respectfully disagree. In part 1, “Incident Communications,” I described the need for local as well as wide-area voice communications and in part 2, “A Knowledge Gap,” I discussed how Public Safety voice communications cannot be addressed using a broadband network. Here, in part 3, I will take a more in-depth look at the requirements for local, non-network voice communications services.

One of the difficulties in explaining these requirements is that there is a difference in the terminology used by the Public Safety community and the commercial wireless and IT worlds. Here I will be talking about the use of voice radio communications for one-to-many communications that do not rely on cell sites or radios mounted on towers. This type of communications is referred to in several ways including “simplex,” “tactical,” and “talk-around” communications. There are no terms to describe these capabilities in the world of commercial wireless since none of these are available over standard commercial networks. What’s more, there probably never will be. Perhaps those of you who are more familiar with IT jargon will understand that this type of communications is peer-to-peer, or more precisely, peer-to-multi-peer.

Anyone who has used Citizens Band radio, or more recently the walkie-talkies for the Family Radio band, can relate. You talk to another unit that is within direct range of your radio without the signal being received and relayed by a cell site or tower. The range is limited, sometimes to as little as one-quarter of a mile and sometimes over longer distances, depending on the type of radio, its power, and the frequency band it uses. This type of communications is essential for the Public Safety community as well as other land mobile radio (LMR) users.

This unique form of communications is not technically possible with a cellular handset since it does not use a cell site or tower to be able to communicate with other units on the same channel. It is important to Public Safety because it enables various groups of first responders to communicate at the scene of an incident without adding to congestion on the primary dispatch channel. We all know we must be in range of a cell site for our cell phone to work. If we are out of range and have no network coverage, or are inside a building, parking structure, or other place where there is no coverage, our cell phone is merely a paperweight. This cannot be tolerated in the world of Public Safety, thus the radios must be capable of simplex operation.

Let’s consider a hostage situation in a bank as an example. The call is dispatched over the primary one-to-many dispatch channel and the first unit on the scene calls in a situation report: a bank with armed robbers inside and customers who have been taken hostage. The dispatcher sends additional units including a commander, the swat team, and fire and EMS to the scene. One person assumes the role of the Incident Commander (IC), whose job is to coordinate all of the activity on the scene: position the swat team, perhaps evacuate buildings surrounding the incident, and deploy the officers and other personnel at the scene.

If all of this radio traffic was on the primary dispatch channel, the dispatcher would not be able to dispatch other calls and the chances of people talking on top of each other would be high. Instead, those at the incident who are working as groups—the swat team, evacuation team, hostage negotiation team, fire, and EMS personnel—switch over to their own simplex or peer-to-peer channels. Each team leader listens to two radio channels, one for his/her team and one that is a direct link to the Incident Commander. None of this traffic interferes with the primary dispatch channel and each group on the scene can communicate within the group and hear all of the traffic for their own team without disrupting other communications.

The Incident Commander (or team) is in touch with the dispatch center and perhaps a higher-ranking commander and can instantly contact each of the teams on the scene. (The one caveat here is that police, EMS, and fire personnel can usually talk only within their own teams, not between teams. This means that fire personnel can talk to each other but not to police on the scene. Since they are all being coordinated by the Incident Command center, when needed, voice messages are relayed by the IC to the other units on the scene.)

At this point, in this fairly small area within a city there would be numerous channels in use. One between the Incident Commander and the dispatch center, one for the swat team, one for the uniformed officers, one or more for fire, another for EMS, and perhaps one or two more for other specialized groups on the scene. If they all had to share a common radio channel, communications would become confusing, and if someone needed immediate assistance, his/her call for help might be blocked by another person talking on the same channel. Using different and distinct channels for each team minimizes the potential for this type of communications error.

Public Safety agencies handle incidents like military operations. Each group has a commander and a mission, and it is up to the IC to make sure every field commander understands what needs to be done and works with the officers to see that the tasks are accomplished. As new personnel arrive on the scene, they are assigned to a team or a new team is formed, assigned its own communications channel, and is integrated into the incident.

Today, the only information the Incident Commander and the rest of the team have is the verbal description from the person talking on the radio. It might be a swat team sniper on a roof advising the team and commander of the situation inside of the bank and whom and what the sniper can see happening. Based on this information, the team commander and Incident Commander will make decisions about how to react.

When we add broadband and video capabilities to this scenario, it will be like giving a blind person sight. The sniper on the roof will be able to transmit video in addition to voice. The commanders will have both verbal and visual awareness of the situation, which will enable them to make decisions faster and with more certainty of the outcome. Even so, voice is still the most critical element in this type of operation.

The radios being used in this case provide speaker audio to each person on the scene so responders don’t have to hold a phone to their ear. If they need to talk, they simply use one hand and press the push-to-talk button on the radio, leaving their other hand free. Further, when they talk, they know they will be heard by others on their team. It does not matter whether they are in range of a cell site; they only need to be in range of each other. No matter where they are working, on a street, in a sub-basement, or virtually anywhere, they will have communications with at least some of their own team members to be able to provide information and receive assistance when and if they need it.

This type of communications is needed not only during a major incident but also on a day-to-day basis. The officers inside the police cars need to be able to talk to each other car-to-car or to an officer on the street and not tie up the primary dispatch channel. On busy nights, most dispatch channels are already overloaded with calls going out, officers responding, and requests for additional information. Tying up these channels with voice traffic between two officers who are only a few blocks apart is not good use of the Public Safety spectrum.

There are those, including some in our government, who believe that tomorrow’s broadband networks will support simplex communications. I don’t believe that to be true. Think about it. Commercial network operators want people to use their networks so they can charge for minutes of use and data services. It is not in their best interest to push the equipment vendors into building handheld devices that will be able to bypass cell sites, and thus networks, and communicate directly with each other. Another impediment to this is that the amount of transmitter power used in a cell phone to communicate to a cell site is far less than the power used in the handheld two-way radios carried by first responders.

Most cell phones operate in full duplex (transmit data in two directions simultaneously so both parties can talk at once) or semi-duplex mode because they transmit and receive on different portions of the spectrum. If the above capabilities were included in the handsets, another set of transmitters and receivers would have to be included. Further, transmit and receive channels are different in each of the commercial bands. This would present a real challenge to the device and chip companies and would add substantially to the cost of each device. It would also be difficult to build a product that supported enough simplex (peer-to-multi-peer) communications channels to accommodate the many incidents where simplex communications are required.

For example, during the recent fires in Santa Barbara County, the channels being used within close proximity included 18 command channels (same as dispatch channels) and 78 simplex or tactical channels. Every available frequency assigned to the local fire departments, Cal Fire, and the National Fire service was in use. These channels were augmented by commercial cellular networks, and several temporary cell sites (COWs) were brought in, but much of the need was beyond cellular coverage. In fact, some needs were beyond the range of many of the command systems. Using simplex or tactical channels, each group fighting its own portion of the fire had its own channels to operate on while Incident Commanders were able to communicate with the commander of each group.

In the world of commercial wireless, there is a huge growth in demand for data services, and networks already have to take measures to better manage their bandwidth so all of their customers have equal access to their data services. Data is gaining in usage, but voice is still the primary wireless communications tool. According to the Bank of America–Merrill Lynch 2009 survey, the average U.S. wireless customer uses 833 minutes of voice each month. Most networks keep their voice and data traffic separated with most voice traffic running over existing 2G technology networks while most data services are on 3G or wireless broadband networks. There are some 3G systems that mix voice and data on the 3G broadband networks, but voice over IP (VoIP) is not as efficient as 2G voice services, and this will be true for many years to come.

The bottom line is that none of these networks can or do provide access to direct device-to-device voice communications services without the use of a cell site. This is a key requirement for Public Safety systems and will continue to be a requirement even after the nationwide broadband system is completed. Voice, both wide-area and local-area, will continue to provide mission-critical services for the first responder community. Those who believe that broadband systems are the only way forward need to understand that voice systems will be needed for many years, and that neither today’s nor tomorrow’s broadband networks can meet the Public Safety community’s voice requirements.

Andrew M. Seybold


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