Subject: [NEXTEL-1] Wireless: The 1-2 Punch Push to Talk

From: Marcelrf <[email-masked]>
Date: Sun, 28 Mar 2004 14:17:51 -0500

Wireless: The 1-2 Punch Push to Talk

Market heats up as four approaches battle for supremacy.

Ken Rehbehn

Chirp, chirp! That cheery signal from a wireless phone announcing your
turn to talk may be coming soon to a cellular network near you. For
consumers, the promise is exciting new opportunities for social dialog
between groups of friends as well as efficient group business
communication. For operators, the goal is increased revenue and reduced
churn.

While Nextel has ruled the PoC (Push to Talk over cellular) market for
the past decade, new technology and standards promise to extend PTT to
more mobile operators in North America. And while Europe has not had the
benefit of multiple wireless technologies because of its regulatory
mandate for GSM, European operators now seem poised to introduce
GSM-based PoC.

Yet, services aside, an operator faces multiple choices in how to
deliver PoC services. Today, four approaches for delivering PTT are
available (see Table 1 ).

Motorola iDEN

Achieving rapid “Chirp to Talk” times has been a hallmark of the
proprietary iDEN experience. iDEN sets the bar for North American PoC
service — and as the only real commercial PTT solution, iDEN essentially
set the bar for PTT everywhere.  With sub-second “Chirp To Talk” times
common, Nextel has been a huge hit among businesses and recently moved
into the public safety sector.

The price for this high performance, however, has been the embrace of a
single network infrastructure and device supplier. The tight binding to
Motorola limits Nextel’s purchasing flexibility while the proprietary
architecture eliminates the potential of interoperability.

iDEN is also showing its age. While newer solutions integrate presence
functions that leverage lessons learned from Instant Messenger services,
iDEN remains a basic PTT service. Likewise, Nextel only introduced
nationwide PTT last year.  Yet, with a relatively small subscriber base
and a mature, well-entrenched infrastructure, functionality upgrades are
difficult to justify and costly to deploy.

Open Mobile Alliance

While proprietary approaches to PoC may produce performance
optimizations, many vendors believe broader market success results from
achieving massive economy of scale only enabled by open standards. To
this end, Ericsson, Nokia, Motorola and Siemens collaborated on a PoC
standard and introduced the completed work to OMA (Open Mobile
Alliance), an industry group producing specifications for mobile
services.

The OMA PoC solution builds on the extensive 3GPP IMS (IP multimedia
subsystem) architecture — leveraging IP protocols for signaling and
voice transport. Using SIP (Session Initiation Protocol) as a general
purpose signaling mechanism, subscriber handsets establish contact with
a PoC server. SIP-enabled presence extensions produce buddy lists
displayed on each talk group member’s handset.

As the OMA considered the initial proposal, some of the contributing
companies produced pre-standard implementations. Motorola’s newly
acquired Winphoria division delivered a working version of PTT to
Verizon and Sprint PCS, while Nokia demonstrated GSM-based PTT server
infrastructure and a new PTT handset, all based on a pre-standard
version of the OMA proposal. In addition to systems that embed PTT deep
in the handset, several handset software client solutions are available,
for example, FastMobile offers FastChat, a Symbian client that works
with the FastMobile PoC service.

With the drive toward a consistent IMS environment between GSM and
CDMA2000 — extending even toward non-mobile networks such as WLAN —

OMA PoC promises to extend universal group communication to collections
of subscribers on disparate networks. Building on the IMS architecture —
with its generic application of SIP-based signaling and the IP-based RTP
(Real-time Transport Protocol) — sets the stage for other “Push To”
services such as “Push to Video,” needed for both consumer-friendly and
business-oriented “see-what-I-see” services.

Performance of pre-standard OMA-based PoC implementations has ranged
from disappointing to surprisingly good. CDMA2000 deployments of
Motorola’s implementation suffer from time delays resulting from
CDMA2000 dormant mode transitions and packet data network procedures.
While optimizations coming in CDMA2000 Release A should improve
performance, the initial service has not posed a threat to Nextel’s iDEN
network.

Waiting in the wings, however, is a pre-standard GSM-based PoC solution
from Nokia that has already demonstrated rapid connection initiation and
fast “Chirp to Talk” responses. Taking advantage of permanent GPRS PDP
(Packet Data Protocol) contexts, Nokia has wrung optimizations out of
the GSM infrastructure to yield performance comparable to Nextel’s iDEN
network. Like Nokia, Motorola has also demonstrated GSM capability, with
plans to deploy it at FastLink, a Jordanian GSM operator.

Qualcomm’s QChat

Qualcomm is famous for championing CDMA spread spectrum technologies,
which are now found in CDMA2000 and UMTS networks. However, behind the
scenes, the vendor has been working on its own PoC technology.
While Qualcomm developed and now markets QChat as a solution for
CDMA2000 operators around the globe, Nextel holds exclusive rights to
the technology in North America — maintaining a possible alternative to
its Motorola-supplied iDEN technology.

QChat targets performance and network efficiency. Qualcomm claims less
than two-second latency when QChat service is accessed over the newer
CDMA2000 Release A network infrastructure.

In the quest to supply “iDEN-like” performance capable of scaling to
millions of subscribers, Qualcomm avoids use of SIP for session
signaling; instead, the QChat QSP engine applies an optimized
proprietary protocol.

Handset support for QChat is limited to four models from Kyocera.
However, broader access to the QChat QSP engine is available via
BrewChat, a BREW client supplied by Qualcomm. By simply installing the
BREW client on a BREW-compatible handset, consumers gain access to all
the QChat functions today, but without some of the optimizations
available in a native handset implementation.

Circuit-switched PoC
Rounding out operator options for PoC is a novel approach from
California start-up Kodiak Networks: Skip VoIP and connect instead to a
PoC server with traditional circuit connections. Already winning deals
with Orange in Europe (GSM) and Alltel in the United States (CDMA2000),
Kodiak Networks has made its presence felt.

With its claim that current cellular packet networks are incapable of
delivering high-quality PoC, Kodiak neatly side steps performance issues
with an architecture that melds packet-based presence functions with
circuit-switched voice transmission.
As with OMA PoC, subscribers with a Kodiak solution get to see fellow
group member’s presence status. But when a request is made to talk, the
handset initiates a circuit call to the Kodiak Real-Time Exchange
System, located in the operator’s network. The system then initiates
outgoing circuit calls to all members of the group, acting as a PTT
relay.

The Achilles’ heel of Kodiak’s implementation is handset availability.
Despite a promise from Kyocera for a CDMA handset, the big GSM handset
suppliers will not be quick to embrace competition to the OMA approach.
But Orange, in its quest to offer a distinctive PTT service, has seized
on Kodiak’s solution. The fact that Kodiak support is readily available
via clients installed on smart phones allowed Orange to introduce the
service. And, in the end, handset suppliers to Orange may find they have
no choice but to cooperate.

The Next Generation
For one-to-many communication, PoC promises a repeat of the SMS growth
story, with mobile operators reaping benefits from vital new revenue
sources. With four different approaches for delivering service, mobile
operators will be forced to carefully weigh costs and benefits, setting
the stage for significant service differentiation.
Ken Rehbehn is principal analyst, wireless infrastructure for Current
Analysis

([email-masked]).

http://www.telecommagazine.com/default.asp?journalid=3&func=articles&page=0403t07_03&year=2004&month=3

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