What Is Push-To-Talk?

I think it is time for the network operators to begin promoting PTT by educating their sales people in stores and their existing customers about what PTT is, what it can do, and why it would be appealing. Today’s younger generation grew up with cellular phones and has taken to them for texting, Internet access, and not so much for voice. Voice seems to be their last choice for wireless communications.

Push-To-Talk (PTT) is a technology used for conducting voice conversations over a radio channel that has been used by the military, police, fire, EMS, and business and industrial two-way radio users since the 1930s. In its crudest form it is voice communications over a voice channel that permits one person at a time to talk and one or more people to listen. Over time, push-to-talk systems have evolved to provide more flexible capabilities, but the basic purpose for PTT is still for one person at a time to be able to communicate by voice to one or more other people simultaneously.

To be viable, push-to-talk services need to be near instantaneous; when a user pushes the PTT button on the device and starts talking, there can be little or no delay. In traditional two-way radio systems (Land Mobile Radio or LMR) the delay from the time the PTT button is pushed and the transmission begins is measured in milliseconds. When the user lets go of the PTT button another user can answer, again, within milliseconds. The timing of the “set-up” and “volley” are critical to the success of a PTT system. One test we have used over the years is to push the PTT button and say, “Don’t Shoot!” If those listening hear the entire “Don’t shoot,” the system is functioning properly. However, if they miss the first word because of set-up delays, the results are not as intended.

With the exception of Nextel, early competitors to LMR did not fully understand how critical fast set-up and volley times were. Nextel solved the problem by designing a system that operated close to LMR set-up and volley times and provided a near instantaneous “beep.” This beep indicated the device was connected to the network, set-up was complete, and the PTT conversation could begin.

Today AT&T, Sprint, and Verizon all offer PTT services across their networks. All of the systems work well and all have most if not all of the same features. PTT has an interesting history with fierce competition; I’ll hit some of the highlights for you here.

A Little History

Push-to-talk services are much more robust today and are still used by the military, police, fire, EMS, and business two-way radio (Land Mobile Radio). Nextel was the first commercial wireless operator to offer push-to-talk service and it did so for a very good reason. The Nextel cellular system began as mostly local Specialized Mobile Radio (SMR) in the 800-MHz band, which had been used only for LMR. When 800-MHz cellular spectrum was divided into A and B blocks, one block was originally allocated to the existing wireline network operator in each area (AT&T for example), and the second was available to a non-wireline cellular provider in order to encourage competition.

Nextel, (originally FleetCall) began buying out other SMR operators and then persuaded Congress and the FCC to allow it to compete as another cellular operator. Then it convinced them to allow recasting its LMR spectrum into a cellular-like architecture. The selling points were that Nextel would create more jobs, invest in a new nationwide wireless network, and add competition to the existing two commercial cellular providers, a win-win for everyone. (These same talking points have been used over the years to convince Congress and the FCC to enable other companies to enter the fast growing cellular, now wireless, industry.)

Nextel started buying up SMR systems in earnest, and SMR folks, mostly two-way radio shops, made a lot of money. However, SMR customers were then told that many established systems providing their two-way radio functionality were going away. Since Nextel used a Motorola-designed cellular technology (iDen) that included PTT along with dial-up cellular, many SMR customers became Nextel customers. Now they had PTT, dial-up voice and, over time, SMS and other services not available with SMR.

As Nextel grew it continued to attract customers accustomed to LMR PTT services but found Nextel coverage better, and the ability to handle dial-up calls compelling. Soon Nextel attracted other customers who had never used push-to-talk but found it to be useful. Instead of dialing up the person they wanted to talk to, one at a time, they set up a group PTT call and were at once connected to all those they needed.

Over the years, Nextel tried to convince some within Public Safety that Nextel push-to-talk service could replace Public Safety’s dedicated dispatch systems. Though this did not turn out to be true, Nextel did enjoy a solid Public Safety customer base for administrative and other personnel to communicate with others without having to carry a two-way radio or listen to routine dispatch traffic.

In its heyday, Nextel enjoyed an advantage due to its PTT capabilities. Customers who knew what PTT was and what it could do signed up with Nextel and became captive customers because no other network offered push-to-talk services. Others including Qualcomm (QChat) later tried to duplicate the Nextel experience but the first version did not meet the need for speed for set-up and volley times. Qualcomm worked with Motorola and Nextel to get it right but with the caveat that Qualcomm could not sell QChat anywhere there was an existing Motorola iDEN system. Because both Nextel and SouthernLINC were using iDEN, QChat was prevented from being used by any U.S.-based wireless networks.

Then Nextel was sold to Sprint. Sprint’s original plan was to convert the Nextel spectrum from iDEN to CDMA to more effectively compete with Verizon and AT&T. Without iDEN, Sprint was able to launch its own PTT service using QChat. The first version Sprint launched was better than Qualcomm’s first attempt but still did not measure up to Nextel’s PTT. Over time, Sprint got it right and moved forward with plans to replace Nextel’s iDEN and move all Nextel subscribers to the Sprint Network.

As Sprint’s plans became apparent, other operators experimented with their own versions of PTT and several software companies designed their own PTT over wireless services, turning PTT into an application rather than a network technology. Verizon, which was after Nextel’s existing customer base, decided it did not need a PTT offering to attract Nextel users but later found it did. Verizon experimented for months and arrived at a solution that was slow and awkward to use. Set-up time was measured in seconds not milliseconds and volley times were also long. AT&T, meanwhile experimented with its own PTT vendor and also launched a PTT product that was not up to par. However, this PTT solution hid some timing delays by recording the voice transmission while the call was being set up, thus users on the other end did heard the entire transmission but with a slight delay.

Fast Forward to Today

The most significant PTT capability is for multiple talk groups—separate groups made up of different members that can be chosen by the person setting up the PTT call. Next is the ability to visually see whose phone is on and available for the PTT call, and the call set-up and volley times are on a par with the old Nextel system. The downside for PTT is that none of these network operators offers a solution that can be used across networks. I believe this is a major flaw and is stinting the growth of PTT services. Text messaging (SMS), and Multi-Media Systems (MMS) did not gain wide acceptance until they worked across all of the various networks in the United States and around the world. Today there is no PTT standard for cellular systems but now that Public Safety has its 700-MHz spectrum for broadband and is building out LTE, this is finally being addressed by the standards bodies.

As AT&T, Sprint, and Verizon aimed at the Nextel customer base, which had begun to shrink, they also decided, almost at the same time, that if they could interface to existing Land Mobile Radio Systems (LMR) perhaps they could convince other LMR radio operators to switch to PTT over their networks. The idea was simple: Sign up for service on a given network, install an IP bridge between the commercial and LMR network, and allow all LMR and wireless customers to use PTT via the bridge. This would provide a smooth migration path and enable companies to move a few LMR users at a time over to the commercial network without having to shut down the LMR network and move everyone at once. It also provided a learning period for companies to see if PTT over one of the commercial networks would work for them without a large investment.

There are companies today that offer cross-network PTT services. The most successful to date is Twisted Pair Solutions. Its system does not care if devices are on LMR, AT&T, Sprint, Verizon, T-Mobile, or even Wi-Fi. Its software application ties them all together. Several Public Safety entities on the west coast recently contracted with Twisted Pair for PTT service for their administrative personnel. The results so far have been mostly good and the system well received. One Sheriff, a recent new Twisted Pair user, told me recently that there is a delay in setting up the PTT call and he and his staff understand that it does not pass the “Don’t Shoot” test. However, it still provides the ability to communicate among each other and to follow any incidents in the field by being cross-connected between the commercial and their own PTT radio system.

The Market

The market for commercial PTT services is very small today but has the potential to grow dramatically. Of the 300-plus million wireless devices in use in the United States there are perhaps 15 million or so push-to-talk devices in use on commercial networks. PTT is, therefore, still considered a niche market. Yet among all three of the networks that offer PTT services (T-Mobile is still among the missing), there is hope that this market will grow over time.

I don’t disagree, but I think it is time for the network operators to begin promoting PTT by educating their sales people in stores and their existing customers about what PTT is, what it can do, and why it would be appealing. Today’s younger generation grew up with cellular phones and has taken to them for texting, Internet access, and not so much for voice. Voice seems to be their last choice for wireless communications.

Those of us who grew up before cell phones (1981 in the United States) were exposed to push-to-talk using CB radios, ham radios, and business and Public Safety two-way radios. The vast majority of those who make up the growing wireless market today have never experienced PTT. Many don’t even know what it is or how it is used. Even the TV shows about police, fire, and EMS show mostly cell phones being used, which is not a true picture of how Public Safety communicates on a day-to-day basis. One-to-many instantaneous communications (PTT) is still their most used and most valuable form of communications today. Those of us who grew up with PTT and still use it everyday understand the benefits of fast, efficient, one-to-many voice communications.

The younger generation would embrace the concept of PTT services if they understood it. They are a one-to-many communications type of users; they like to tweet, which is one-to-many text messaging. If they were aware of PTT and its one-to-many instant voice communications capabilities, I believe they would quickly take to it.

The issue has been that those offering PTT over commercial networks have not implemented a common standard that works across networks. Groups of teens would not be satisfied with being able to use PTT to communicate only with friends on the same network.

It is time to get PTT up and running as a common, fully functional application that can be used on many different devices across any and all networks. Then the networks might even convince the younger generation that PTT is Twitter for voice!

Andrew M. Seybold