Push-to-talk fever escalates
Do you know what PTT stands for? Of course you do, you have been reading about it in MRT since its inception. But this well-known acronym relating to a basic operational function for two-way radios has recently become hyped at fever pitch in the cellular world.
Adding to the excitement, on June 20, 2003, Nextel announced that the U.S. Patent and Trademark Office approved the registration of its trademark for its “Push To Talk” service.
Nextel officials have insisted that their trademark application process began in January 2002 and addresses a concept the company pioneered for more than 10 years.
While this is, and likely will continue to be a hotly debated issue, they certainly have been the most successful at developing a wide-area system that supports full-duplex voice communications coupled with push-to-talk services in the SMR band. They have excelled in their marketing strategy and have moved from a niche player to becoming one of the top six U.S. carriers. Their numbers speak for themselves: 10.6 million customers, average revenue per client of $69 per month, and a churn rate of 2.1 percent. Because this success has largely been attributed to its differentiated push-to-talk service known as Direct Connect, other cellular carriers now want a piece of the action.
Verizon Wireless officials disagree that “PTT” and “Push To Talk” are exclusive to Nextel’s, stating that these terms have been used to describe two-way transmissions since the 1940s. They also have stated that since the 1990s, others including Microsoft, Ericsson, Motorola, AT&T and Nokia also have used the terms. Verizon argues that Nextel’s attempts to trademark the words goes against those precedents.
And there is motive behind their actions. Verizon and Sprint PCS both have announced plans for some sort of push-to-talk solution by the end of 2003. Carriers such as AT&T Wireless, T-Mobile and Cingular also may have a deployable technology in the works, as the GSM standards community appears to be adopting a standard for push-to-talk services.
From a land mobile radio system perspective, changing from a full-duplex only cellular system to one that can accommodate PTT seems non-trivial. It may appear that a wide-scale replacement or massive upgrade of the entire system architecture would be in order-possibly ranging from thousands of cell sites to several regional switching centers. But the technology driving the transformation to cellular PTT services is software-based and takes advantage of the IP packet data services now available in the new generation networks. The technology is dubbed voice-over-IP (VoIP) and already has been deployed by at least one land mobile radio system, M/A-Com’s OpenSky.
Interestingly, Nextel also is supporting the new VoIP strategy for possible deployment in its next generation push-to-talk service. Its Direct Connect system, based on iDEN, is a proprietary non-VoIP technology based on Motorola’s Dispatch Application. But through a partnership with the CDMA magnate, Qualcomm, a product called QChat advertises itself as “The Complete Push-to-Talk Solution for CDMA Operations.” What is peculiar is that Nextel is not a CDMA operator. Deploying it would require new infrastructure using much wider channels. However, their eagerness for new spectrum is evident in their December 2002 Consensus Plan to remedy the ongoing Public Safety interference issues in the 800 MHz band. As part of the plan, Nextel is seeking 10 MHz in the 1.9 GHz band, as compensation for eliminating the interference by funding the relocation of affected incumbents.
From a user perspective, QChat operates in a similar fashion to trunked radio. Communication begins with a single press of the PTT button on the handset. A call is formed by combining separate point-to-point connections between each IP endpoint and a managing server, deployed on the operator’s IP Wide Area Network. Pressing the PTT button originates a call to the target QChat user and provides the originator with a response tone indicating the availability of the target users.
An interesting aspect of Qchat is that it is implemented on the mobile phone as a software application. Qualcom’s Binary Runtime Environment for Wireless provides the framework to manage the intersection of data and telephony features. Through it, existing BREW-enabled phones can support PTT by simply downloading the QChat client over-the-air.
Qualcomm is not alone in their developments. The other major network providers are salivating at growth in this market. Nokia, for example, announced in June 2003 their prediction for strong sales of PTT, saying that the walkie-talkie service will be offered over any Internet-enabled mobile phone network, from GPRS and EDGE to 3G. They claim it allows consumers to use ordinary mobile phones as an easy and cheap way to speak to relatives or groups of colleagues.
Sonim Technologies has partnered with Ericsson to provide an IP multimedia system-based push-to-talk solution interoperable over GPRS, EDGE, W-CDMA and CDMA 2000 networks. It is are focused on driving the industry’s PTT standards for a client/server solution with support for a variety of devices. Sonim’s Instant Communications Client is integrated at the chipset level and has been endorsed by chipset leaders such as TI, Intel, Infineon and Agere. This native integration on devices enables Sonim to support PTT features not only on high-end smartphones and PDAs, but also on mass-market feature phones where memory and processing power are usually limited. According to Wade Vesey, Sonim’s chief marketing officer who previously managed Nextel’s Direct Connect launch, push-to-talk is compelling to both consumers and business professionals. He believes that as a majority of these users carry low to medium priced feature phones, the ability to support PTT on their preferred phones becomes critical in a carrier’s go-to-market plan. Vesey also reveals that Sonim is working with four of the top five handset manufacturers on PTT integration.
Providing push-to-talk services over an IP backbone provides useful features unavailable in traditional land mobile radio systems.
For example, if you want to call Howard, you look him up in your contact list (see Figure 1). If his device is turned on, an icon indicating he is available appears next to his name in the contact list. This feature is advantageous because it can potentially avoid wasted airtime and improve communication effectiveness. The user experience is also fun and consistent to that of instant messaging, equally important since a core market segment for these services will be teens, young adults, and families.
Although these new push-to-talk services will soon be deployed en masse, the technology has not yet matured. Work needs to be done to provide Quality of Service on the underlying networks themselves to ensure consistent and reliable results. So building a carrier-grade PTT solution with real-time capabilities will require significant time and effort. Many, including competitors in the industry, are challenging latency claims and call setup delays. Some claim, depending on the technology deployed, these may range from two to 10 seconds. This is likely not tolerable for field service or public safety users, but may be reasonable for non-critical communications.
The immediate impact of this technology on existing SMRs will likely be subtle. Today’s two-way business has already endured substantial stress through Nextel’s business strategy. While some operators have retained key customers due to their superior service arrangements, others have folded or sold their spectrum. The proliferation of PTT services on common carrier networks will likely have a broad appeal as an instant messaging platform, but not for mission critical needs.
Gutowski is a Telecommunications Consultant at PacifiCorp in Portland, Oregon. He can be reached via e-mail at [email protected]