From: "Mark Wood (ETL)" <Mark.Wood@etl.ericsson.se>
To: "'warnings@ntia.doc.gov'" <warnings@ntia.doc.gov>
Date: Fri, Jul 14, 2000 12:35 PM
Subject: Warnings by cell broadcasting.
Friends,
From:- Mark wood, (working group on emergency telecommunications, WGET)
My thanks to Paul Thompson at InterWorks for asking me to contribute to this very important
roundtable. Here are some thoughts on mobile systems and their features for your kind
consideration.
Cell Broadcasting
-------------------------
Most of today's wireless systems such as IS 54 D-AMPS and GSM, support a feature called 'Cell
Broadcasting'. A public warning message in text, can be sent to the screens of all mobiles (having
such capability) in any group of cells of any size, ranging from one single cell (about 5 miles
across) to the whole country if required. To my present knowledge all GSM phones have this
capability, as do D-AMPS phones, but not analogue AMPS phones. I do not know about the IS95
CDMA system, I feel sure that it must have CB. Since the iDen system (trading as Nextel) is
based on GSM, I see no immediate reason to doubt that it too has a CB functionality.
Access to Cell Broadcasting is done from the 24/7 Network Operations Centre (NOC) of the
operating company. To send a CB you would have to have a separate arrangement in advance
with every operator in the target area (about four or five of them, including Nextel). I foresee no
technical barrier to automating this process, but since the potential for abuse of the system is so
great, operators may want to check each message before sending it to CB. However since a senior
manager is always on duty at the NOC, it should be simple to set up an arrangement.
The advantage of Cell Broadcast is that there is no cost or special technology to set up for either
party and that 90% of all mobile users already have what they need to receive CB without any
further upgrades. Also since the same message is sent out from the control channel on a
broadcast basis, there is no overload of the system while each terminal is sent the message. CB
does not require acknowledgement from the terminals and is forward error corrected.
The disadvantage is that the message can be text only, and must contain less than 250 characters
or so. A further problem is that many users do not know how to read a text message when they
receive it. Those users with old style analogue AMPS phones will not receive CB messages.
However this is presently around 10% and diminishing rapidly.
Short Message System (SMS)
--------------------------------------------
SMS is rather like a two way message pager system, in which text messages are targeted at
individual users rather than all users in the same cell. It can be accessed directly by the Internet,
as users get an internet address for access to SMS. Therefore no special arrangement is needed to
target a specific group this way. However it will involve the transmission of thousands of
messages, which may seriously congest the SMS system. This approach is best for groups of
hundreds rather than thousands. Also SMS takes no account of position. The user could be out of
the country and still get the message.
Cellular Positioning systems (CPS)
----------------------------------------------------
Since the E911 regulations have mandated positioning systems which find locations down to
120M, it will be possible to send a message to a specific user only if that user is in a certain
position. The positioning server will find the location of the user only when a request for that
particular mobile has been made. I the target user is known, then a position can be determined,
and the message sent can be changed depending of the location of that user.
However there is a charge for the locating service, and there is a limit to how many positions can
be performed by the location server in an area, so locating a huge number of users this way
would be less efficient than Cell Broadcast.
CDPD and GPRS
--------------------------
Packet data systems such as Cellular Digital Packet Data (CDPD) and coming on to the scene
this year will be General Packet Radio Service (GPRS) will rise in importance very soon. To my
present knowledge both also have the same features of cell broadcasting and position finding.
Public warnings could be pushed to any terminal in a certain geographical area, again by the
same arrangement with the operator. In fact CDPD is used by the AMPS-D-AMPS operators, and
GPRS by GSM operators. However I am unsure at this time if the terminals feature an alert on
receipt of CB messages. In many sectors, advertising is seen as the primary use for CB, so it may
not be getting the respect it deserves from the terminal and application makers. Please consider
the following on WAP.
WAP and push
----------------------
My present information is that all terminals (and mobile phones) in the future will be equipped
with some form of Wireless Access Protocol browser client (WAP). This will enable users to get
access to WAP WebPages, in order to pull information. However if the WAP browser is
configured to work via an SMS gateway, CDPD, GPRS or EDGE gateway, then the user is
logged on to his wireless service provider all the time. This in turn will enable push services to
be offered. In other words, the user could go to a WAP webpage and subscribe to any kind of
public information that he wanted. When the public information bulletin is published on the
WAP webpage, the WAP pusher would push this information to all who had subscribed to this
webpage. Since the WAP infrastructure will be already in place, and WAP browsers will be
commonplace two years from now, this is another way to very cheaply push public information.
Furthermore, one WAP webpage will push messages whichever barer system is c!
urrently in use by the client.
The disadvantage is that it will only inform those who have subscribed to the information and
that it would send thousands of messages at one time. If a seriously large group were to subscribe
to public information overload of the gateways and barer network could result. A further problem
is that like SMS, the message would be pushed to the user regardless of the users position. In fact
the push can be linked to the position server, but the success of that depends on the volume of
position requests involved.
We should study this and make sure that the application developers, particularly the 'WAP forum'
has prioritised the pushing of public safety messages on their applications. Since there are very
many application developers, this may have to be accomplished by mandate or at least by
gentlemen's agreement among application developers interest groups.
Nevertheless it is a very simple, cheap and easy to administer system requiring no special
hardware.
Third Generation 'Wireless Internet'
-------------------------------------------------
My information is that 3G systems such as Enhanced Data Rates for GSM Evolution (EDGE),
Wideband Code Division Multiple Access (W-CDMA) (known as UMTS in Europe, or
CDMA2000 and IMT 2000 in many other places) and other third and fourth generation systems
will also offer Cell broadcasting. In addition, the same servers that provide push messages for
WAP can also push to any 3G device. No further development would be needed when 3G
systems are rolled out, as their gateways are accessed by IP networking.
However since the graphical capabilities of the third generation systems are much greater, a
public message could also include a map showing the extent of the expected disaster, such as a
radar image of a Hurricane, or map of the warning squares.
My information is that 3G systems will feature much more developed 'narrowcasting' capabilities
which will enable pushing to certain areas, or certain terminals, but on a broadcast basis rather
than a one-at-a-time basis (which would cause overload).
Conclusion
----------------
This is the perfect moment to discuss this issue as we can in one stroke, settle the landscape for
first, second and third generation mobile systems. By arranging Memorandums of Understanding
with all operators within a region and lobbying application developers of 3G devices, public
safety messages can be pushed to all users of any future communications device.
I will be honoured to expand on any aspects of the above if requested, and am ready to participate
in this very worthy project.
Mark Wood. mark.wood@engineer.com
BIO
-----
Mark Wood is the author of the book 'Disaster Communications' (APCO) and has received a
recognition from the secretary general of the ITU for his work as a consultant to the United
Nations Office of the Co-Ordination of Humanitarian Affairs (UNOCHA), and as a member of
the secretariat of the Working Group on Emergency Telecommunications (WGET). He also
lectures Telecommunications for the Disaster Management project at the University of
Wisconsin. Mark is a British citizen and lecturers mobile systems for Ericsson in London.
CC: "'host@disastercenter.com'" <host@disastercenter.c...