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PUSH TO TALK PUSH
TO
TALK Executive Summary
One of the most exciting new services
anticipated for GSM is Push-to-Talk. It is a
relatively new term to describe the original,
long established mode of operation for
mobile radio. With it, a group of users
speak in sequence, one way at a time,
while holding down a transmit button,
rather than speaking in conversational
mode as with a conventional mobile phone.
Although a simpler mode of operation, it
has its own special advantages.
Communication is instantaneous just
push the microphone button and you are
in contact. There is no need to look up and
dial a number first. The called person does
not need to touch the radio to hear the
message it is always on and in contact.
All members of the group can hear all of
the messages simultaneously and
communications can be monitored by
people authorised to provide support and
direction, who can also communicate to
the group.
In a professional environment, the one way-
at-a-time speech encourages short,
to-the-point dialogue, which reinforces
discipline and discourages argument and
repudiation. Thus in many command,
business and commercial situations these
systems, usually called two-way radio or
dispatch services, remain the preferred
method of radio communication and have
continued to grow alongside mobile
phones. Simple two-way radios have very
restricted communications range and so,
for the more demanding applications,
networks of base stations have been
deployed, which are interconnected by
fixed links, just like cellular.
One company in the USA took this one
stage further and combined cellular
telephony, with its conversational mode
and dial-up, with a Push-to-Talk dispatch
service. Although it was very successfully
marketed to business and commercial
users, the additional Push-to-Talk facility
quickly caught on with consumers who
found that the enhanced contact between
groups of family and friends extends the
most fundamental attraction of cellular
communication, making the social ties
between groups of people even closer.
The result has been an outstanding success
for the company, which has shown the
highest revenue growth, ARPU and lowest
churn for any cellular operator.
In order to capitalise on this opportunity,
the GSM community is developing a set
of standards called Push-to-Talk over
Cellular (PoC). Unlike the earlier systems
that were based on extensive modifications
to the networks, the new solution is based
on the IP Multimedia Subsystem (IMS)
and GPRS, EDGE or WCDMA for the radio.
It can be brought to market more quickly,
with much less disruption and at
substantially lower cost than by the
previous means. By using IMS, PoC can
be easily combined with other GSM
features such as Presence and Location
Based Services to create yet more
enhanced services as yet undreamed
about, adding to the already proven financial
rewards of Push-to-Talk on its own.
PoC has the chance to capture a good slice
of the market for both consumer and
professional two-way radio services, as
well as the ability to create brand new
opportunities. It all adds up to a wealth of
new revenue opportunities for the network
operators.
Introduction
Push-to-Talk is expected to be one of the
most important new services on GSM. It
adds an instantaneous, one-way-at-a-time,
one-to-many communications mode to the
already established one-to-one
conversational mode of cellular, but with
many advantages over conventional two-way
radio or simple walkie-talkies. This
paper explains the long established
historical background to push-to-talk, which
sets the precedent for guaranteed success
for the service on cellular. The operational
differences between push-to-talk and
conventional mobile telephony are detailed
and it is explained why combining the
modes on a cellular network provides
benefits all round. The commercial
advantage that operators who have already
deployed Push-to-Talk have gained is noted
and it is explained how the service can be
added to GSM networks easily and at
relatively low cost by means of the new
Open Mobile Alliance (OMA)-led standard,
Push-to-Talk over Cellular (PoC). Finally,
the additional ways in which PoC will
enhance the user experience and the
cellular market are predicted.
What is Push-to-Talk?
Push-to-Talk is a relatively new term to
describe a long established mode of
operation for mobile radio, in fact, the
original mode that goes back many
decades. Today, members of the public
are most familiar with mobile radio in the
form of the cellular mobile phone. Here
the user simply operates the device like a
normal telephone he dials the number,
the other party answers and the two have
a natural conversation together. The only
difference is the SEND button, which
initiates the dialling, acts as the off-hook
switch when the called party answers and
as the on-hook switch when either party
ends the call. This one-to-one
conversational mode has been made
possible by advanced radio and signalling
technology that has only been feasible
since the mid-1980s.
Before that time, things were much
simpler. The lack of sophisticated
technology, like miniature filtering, meant
that radios could not transmit and receive
at the same time. Thus rather than a natural
conversation, the users had to speak one
way at a time, in sequence, punctuated
by those immortal words over and out.
In order to put the radio into transmit mode,
so allowing the operator to speak, the early
bulky radios had manually operated, panel
mounted transmit-receive switches. As
lighter units were developed for vehicles,
aircraft and man-packs, the panel switches
were replaced by push button switches on the microphone or control column
(aircraft) and usually they were marked
Push-to-Talk!
This type of radio is still in wide use today
and with it, the operator can hear the
transmissions from all the others that are
tuned to the same frequency and that are
in radio range. Thus users separate
themselves into groups of interest by
tuning the radio to a particular frequency
or switching to a particular channel again
a manual process. Whether they be
platoons of soldiers or squadrons of aircraft
or police units, everyone in the group can
hear their commander and each other. The
first applications were for the police and
military during the 1930s, quickly followed
by aircraft. The first use in private hands
was with marine radios, primarily for
trawlermen and then car units for taxi
drivers. Around 1980, two-way radio as it
was called (to distinguish it from broadcast
radio which was one-way) exploded
onto the popular market from the USA in
the form of Citizens Band (CB) radio.
Although it originally had a serious side to
enable truckers and remote communities
in rural America to keep in touch, it acquired
a cult status and a mass market for a brief
period through the Hollywood film
Convoy. Through popular demand, it
forced its way over reluctant conservative
authorities in Europe and in effect opened
the doors to the consumer revolution that
has embraced radio communication today
in the form of mobile phones. While CB
radio in its original form has virtually
disappeared, something similar exists today
in the form of the brightly coloured little
walkie-talkie radios that can be bought in
many stores and supermarkets. The
intention is the same, to keep family and
friends instantly in contact.
It might have been expected that the
coming of mobile phones with their
convenience, privacy and the absence of
any need to understand special operating
procedures would have finished off any
interest in two-way radio. However, there
are powerful reasons why it still survives
as the method of choice for many
applications and it is important to
understand these lessons from recent
history, because it points the way to the
benefit and need for compelling Push-to-
Talk services and applications on cellular:
Communication is instantaneous just
push the microphone button and you are
in contact. No need to look up and dial a
number first. This is essential when instant
response and fast action is needed.
For these reasons, two-way radio remains
The message recipient does not need
to touch the radio to hear the message
it is always on and in contact.
Essential for when the user is busy
with his hands full.
All members of the group can hear all
the messages, thus they can help one
another out in a tight situation if
necessary or at least understand the
situation that other members of the
group are in.
The one way at a time speech, which
encourages short, to-the-point dialogue
actually reinforces discipline in a
command and control situation.
Furthermore, the fact that all members
of the group and its hierarchy hear the
orders, acknowledgements and
responses also enforces discipline and,
unlike conversational mode,
discourages argument and repudiation.
Communications within the group can
be monitored by those responsible for
strategy and tactics, enabling them to