Subject: [NEXTEL-1] CDPD is nearing extinction...know you wireless WAN options

From: [email-masked]
Date: Wed, 14 May 2003 01:47:35 -0400

CDPD is nearing extinction...know you wireless WAN options

By David Berlind

May 11, 2003

Since 1995, CDPD has been one of the preeminent wireless wide area
network (W-WAN) technologies used for transmitting data to and
from wireless devices in "the field."

Today, CDPD has two main attractions -- coverage and cost. CDPD is
available in most of the places where existing cell
 phones work, and is one of the few networks that satisfies my
three most important criteria for choosing a W-WAN:
 coverage, coverage, and coverage (C3). I'm often asked what the
best W-WAN is and why. People tend to focus on
 features such as speed (CDMA 1xRTT's forte) or the graceful
co-existence of voice and data (the main strength of
 GSM and GPRS). While both criteria are important, absence of a
signal when you need it most renders them moot.

The other advantage to CDPD is cost. Because it's a standard with
which various carriers could comply, the competition between those
carriers helped to make the monthly costs manageable. Depending on
your service provider, the monthly cost for an all-you-can-eat
data CDPD plan ranges from $30 to $50. I've been paying $40 per
month for CDPD service from Earthlink.

On the down side, CDPD is painfully slow when compared to the
speeds of 2.5G and 3G networks that are coming on line now, such
as 1xRTT, GPRS and their successors. Performance hasn't been an
issue for most mobile applications. (Whether the majority of
wireless application types in use have been designed to work with
the available bandwidth of performance or, it just happens that
performance isn't a major requirement for most applications, is a
good subject for debate.) As someone with fairly horizontal needs
(e-mail and the Web), I tend to absorb whatever performance I can
get. However, for plenty of other wireless
applications --especially verticals -- performance is a non-issue.

The other down side for CDPD is that it's on death row. At RIM's
Wireless Enterprise Symposium last week, AT&T representatives
explained to me that its nationwide CDPD network will be turned
off on June 30 or July 31 of 2004. Verizon, another CDPD provider,
will shut down its network in December of 2005. Rumor has it that
Verizon would have preferred to decommission its CDPD network
sooner, but a contract with the Illinois State Police that
guarantees availability until the end of 2005 is preventing that
earlier retirement.

Given CDPD's limited future, it doesn't matter whether you're an
existing CDPD customer or someone planning to deploy wireless
applications for the first time. Now is the time to be considering
your options. Provided you're willing to go the data only route,
and performance is a non-issue for your users, the two best
options at this point are Motient or one of the Mobitex network
providers.

Given my C3 requirement, which of the two networks has a better
footprint is hard to tell. Each claims to have the best national
coverage of any packet radio network. (Neither has anywhere near
the coverage of CDPD.) On its site, Mobitex provider Cingular
(http://www.cingularinteractive.com/business/mobitex_map) says it
is the "only nationwide Packet-Data Network in the country," a
claim that Motient's site doesn't seem to corroborate. For
example, whereas Motient's coverage map
(http://www.motient.com/find/national.asp) indicates some hot
spots around Alaskan cities Fairbanks and Anchorage, Cingular's
site (http://alliance.cingularinteractive.com/dev/cda/zip reveals
no coverage in Alaska.

Ultimately, both networks compete on Metropolitan Statistical Area
coverage
(http://www.census.gov/population/www/estimates/aboutmetro.html
(MSA) -- a statistic that's worth familiarizing yourself with.
Motient's site
(http://www.motient.com/Content/NetworkCoverage/networkoverview.ht
m) claims the "network provides in-building and on-street coverage
to all of the nation's Metropolitan Statistical Areas (MSAs) and
extends service to the 520 most populated U.S. cities, touching
more than 220 million people." Meanwhile, Cingular's site says the
company covers "more than 93 percent of the business population
located in 492 Metropolitan Statistical Areas (MSAs) and non-MSAs
including all 50 of the top markets, with a total population of
200 million people and over 130 of the top airports in the
nation."

I won't even attempt to make heads or tails of the claims because
they don't matter. What matters is whether the area your mobile
workforce operates in has coverage.

Increasingly however, data-only WWANs are being overlooked in
favor of networks and plans that support both voice and data. One
reason is that handheld devices like BlackBerries and cell phones,
which were previously confined to voice or data, are increasingly
supporting both. At its inception, the BlackBerry was primarily a
wireless e-mail device that worked over Mobitex and Motient. More
recently, certain models work as both a wireless phone and data
terminal, supporting a range of applications beyond e-mail such as
Siebel- and SAP-based customer relationship management systems
(CRM).

The main benefits are obvious. Our lives are simplified by
carrying a single integrated device instead of multiple devices
(and their chargers, etc.) and having a billing relationship with
a single wireless carrier. The downside? Compared to Mobitex and
Motient networks, the national footprint for these evolving
networks is substantially smaller, which means that for both voice
and data, your device will not work in as many places.

Once you go the integrated path, however, your choices narrow to
two types of carriers--those that support GSM/GPRS and those that
support CDMA 1xRTT.

While I've already written one article
(http://techupdate.zdnet.com/techupdate/stories/main/0,14179,29084
62,00.html) the differences, it was interesting to hear the pitch
from the carriers at RIM's Wireless Enterprise Symposium.

One issue I didn't mention in my previous article was that devices
supporting the GSM/GPRS option (available from carriers like
T-Mobile, AT&T, and Cingular) generally work in other parts of the
world, making them ideal for international travelers. Another
benefit of the GSM/GPRS option is that it provides an important
voice/data co-existence feature that's not available on CDMA 1xRTT
(available from carriers like Sprint and Verizon). In the GSM/GPRS
world, if your device is in the middle of passing data back and
forth across the network, and an inbound call comes in, the data
exchange is interrupted to accept the call. When the call is
complete, the data application resumes where it left off. Verizon
representatives admit that if a CDMA 1xRTT device is in the middle
of exchanging data with the network when an inbound call comes in,
that call will be forced to roll into voice mail. The problem is
not solved by the targeted successor to CDMA 1xRTT ,CDMA 1xEVDO.

I say "targeted" because it's not absolutely clear whether 1xEVDO
is a step that carriers like Verizon are willing to take.
Upgrading the infrastructure apparently isn't cheap. 1xEVDO's
chief selling proposition is that it will be significantly faster
than 1xRTT. The theoretical limits for both are 2.4mpbs and 144
kpbs, respectively, with the real world experience throughput
close to half the advertised speed. Already, 1xRTT, which averages
50- to 70 kpbs, has proven to be almost twice as fast than GPRS.
Currently, Verizon is testing 1xEVDO in the San Diego and
Washington D.C. markets. The company is trying out Nortel's 1xEVDO
equipment in the San Diego market, and Lucent's in D.C.

Verizon representatives said the decision to deploy nationwide
will depend on how well the technology is received in those
markets. Though no information is available, my guess is that the
service must cost substantially more than 1xRTT, or acceptance
wouldn't be much of an issue. After all, for those on or
considering 1xRTT, 1xEVDO seems like a no-brainer because it's
backwards compatible with 1xRTT. That means if you buy
1xEVDO-based client devices, they'll work on 1xRTT networks
(though not the other way around). This is important because, if
and when 1xEVDO gets rolled out on a wider scale, you'll want your
mobile users to have continuous connectivity, even when they roam
out of 1xEVDO coverage areas into ones that have 1xRTT. This
should be another critical decision criteria when picking between
GSM/GPRS and 1x-anything.

According to the Verizon reps, the next step for GSM/GPRS, known
as EDGE (Enhanced Data for GSM Evolution), has a theoretical
maximum of 384 kpbs but will deliver only 100- to 120 kbps in
practice. More importantly, they said, achieving backwards
compatibility along the lines of what should be available with
1xEVDO and 1xRTT has yet to be demonstrated. If backwards
compatibility is achieved, it will invariably require more
expensive client devices that have two radios because GPRS
operates on a different radio frequency than does EDGE.

For those considering their WWAN options for new applications or
because they have to migrate off of CDPD, cost will also play a
role. Whereas all-you-can-eat-data plans are available and
reasonably priced for CDPD, the price will go up if higher
performance or merged voice and data are on your checklist. For
example, with AT&T GPRS, data is billed separately from voice and
the highest monthly volume plan, which costs $100, allows for 100
megabytes. Additional data transfer is charged at $ .001 for each
additional kilobyte beyond the 100 megabytes monthly.

GPRS carriers generally allow users to use phones like Ericsson's
Bluetooth-enabled T68i as a GPRS-modem for data devices on
computers and PDAs. CDMA 1xRTT-based Sprint, as another example,
provides all-you-can-eat-data with all of its voice plans, but
doesn't endorse using one the devices it provides as a 1xRTT modem
for PDAs (unless the PDA functionality is integrated into the
device) or for PCs.

There are workarounds
(http://techupdate.zdnet.com/techupdate/stories/main/0,14179,29135
28,00.html but they're not endorsed by Sprint. Sprint has a
data-only, all-you-can-eat plan for $120 per month, and it
requires the purchase of a PC Card-based adapter.

I could go on with more pricing examples, but you get the picture.
Expect to pay more if your CDPD migration/WWAN plan includes one
of the voice/data networks versus a lower bandwidth data-only
network. Cost and features will factor into your decision, but
don't forget that at the end of the day, C3 is the golden rule.

http://techupdate.zdnet.com/techupdate/stories/main/0,14179,2913614,00.html

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