It seems like a step backwards in time. Way back in the 40s and 50s the first wireless mobiles were one-way voice channels (termed half-duplex) requiring users to say “Over” and switch to receive before the party at the other end could push their button and speak. But this push-to-talk, walkie-talkie approach was superseded by having the two simultaneous voice paths (full duplex) in today’s mobile phone networks, wasn’t it?

Apparently not. Nextel in the US has been running a cellular-based push-to-talk service for over a decade as an adjunct to its regular two-way cellular service but now suddenly the other mobile network operators have seen the light. Leading US network operator Verizon launched a new service in August last year, followed by Sprint PCS and with others in the US to come. Now, in Europe, Orange has announced this month a new cellular-based push-to-talk service (variously referred to as PTT, P2T and PoC – Push-to-talk over Cellular) to commence during the second quarter of this year in France and the UK and then spreading to 8 other countries. This will be the first PTT service on GSM.

Is this nostalgia gone mad?

What’s your 20?

To those who remember the trucker culture of the mid-1970s, this perhaps raises the happy prospect of rejuvenating the CB lingo with immortal lines like

“This here’s the Rubber Duck” and

“You gotta copy on me, Pig Pen, c’mon?”

and being chased by the “Bear in the Air” (helicopter police) and the “Smokies” (speed cops).

Maybe not. Nextel’s service is squarely aimed at business users. Their special PTT phones are now evidently the phones of choice for such activities as messengers in large cities like New York. Also, construction workers out on site, real estate agents out in the field, factory managers and others who need to be in constant contact with a particular group of co-workers. All are equipped with similar phones so they can chat easily and quickly without having to dial-ring-answer.

So what is it?

Each phone has a dedicated PTT button. The typical method is first to push the PTT button, which causes a display to show a list of your PTT contacts. Using up and down arrow keys, you highlight the individual or group you want to call. Then you push and hold the PTT button, wait about two seconds for a beep that confirms the connection, then start talking.

At the other end, everyone in the group hears a bleep and then your voice. No dialling, no ringing, no need to pick up. When you finish talking, you let go of the PTT button and everyone else hears another beep. The next person in the group to press his/her PTT button can then respond. Anyone else in the group pressing their PTT button just later gets a busy signal and has to wait. A group is typically 1 to 10 contacts, so as well as co-workers it could be family members, different groups for different friends, and so on.

The opportunity is therefore to open up this type of application to a wider set of users, inevitably including the youth market. Indeed, Nextel has demonstrated the positive impact of this feature on ARPU (Average Revenue per User) and that is really what has got operators excited about it.

But here in Europe?

This is all very well in the US, where text messaging is still in the minority. In Europe, though, texting is very popular and now already being supplemented by picture messaging and voice messaging, and video for some – collectively multimedia messaging. Is there a threat that this will tend to cannibalise messaging revenue for no real gain?

The theory is clearly not. Also, there is a concern that use of multimedia messaging may not grow as hoped. In addition, there are many mobile users who simply do not use text messaging. Particularly the over-40s apparently. PTT offers a simpler method for instant, one-way communication that does not involve learning to type on 12 tiny keys!

The mobile phone suppliers are certainly in on the act. Motorola makes the phones for Nextel, so has been in the PTT business forever. For them, this new interest is particularly welcome since they were late onto the camera phone scene.

Meanwhile Nokia launched its first PTT phone in November, also the first PTT phone to work on GSM. The 5140 also has a built-in VGA camera and looks like being the first of many in the Nokia range. The company has indicated that it will introduce a full range of push-to-talk capable GSM phones, including Symbian OS based smartphones. In fact, from 2005 onwards push-to-talk is expected become available for all Nokia GPRS/WCDMA phones.

Siemens has also announced it will be supplying PTT phones, as has Kyocera. Others will surely follow, with it looking increasingly likely that most mobiles will be equipped with PTT within the next few years – along with a camera of course!

Whatever next

PTT is implemented in different ways in different systems. Some use IP telephony over GPRS, others argue that this is too slow. The network links, though, are IP-based and typically use SIP (Session Initiation Protocol) – an IP-based protocol that makes call set up easy and flexible. This makes it possible to introduce “presence” detection on PTT phones. It means that, when the PTT button is pressed and the list of contacts is displayed, it also indicates who on your list has their phone on and is ready to receive PTT calls. It is exactly like buddy lists for instant messaging.

This makes a lot of new features possible. For example, Orange has highlighted the ease of moving from a group PTT call, with one person speaking to a group – perhaps inviting all those available within the group to a conference call, to a full multi-party conference phone call. There is also the potential for connecting to IP telephony services for low cost international calls, complete with presence detection. That might not be so quick in coming though! 

. . . wait for it

There are a few issues with PTT though. Chief among these is latency – the time it takes for the voice path to travel through the system before a response can be given. While a couple of seconds may not be a problem, if this goes to 5 or 6 seconds or more, it could become frustrating to use. This could significantly impact on how much operators can charge for the service – especially to business users.

There is also an issue of etiquette in using it. The same executive who loves the immediacy of simultaneously directing several colleagues to a business lunch at a hard-to-find restaurant may not be happy when one of those colleagues butts into an important client meeting three hours later.

Signing off could be fun though. As in traditional CB-speak,

“That’s a big 10-4, good buddy”.

 © e-principles 2004

Robin Duke-Woolley