This FAQ focuses on the uses
of the Public Land Mobile Network (PLMN) and allied technologies to
transport data for handheld computers.
¿Why should I read this page?
Awareness of 3G technology
is increasing, but remains low in the US when compared to other
developed nations. In a study covering 13 countries, about 89% of
mobile phone or Internet users in the US are "unaware of" or feel
"poorly informed" about wireless Internet technology. The percentage
was 86% in the UK, 77% in Italy and 54% in Germany. Ownership of mobile
phones, for people 15 and older, was 36% in the US. Those figures were
69% in the UK and 59% in Germany. Only 6% of mobile phone users in the
US say they send a text message at least once a week; that compares to
56% in UK, 55% in Germany and 58% in Belgium. (Taylor Nelson
Sofres Telecoms, 6/2001.)
¿What are the major cellular systems and how popular are they in the States?
There are five major international mobile systems in
the world today. Here's some info for North American users as of 2002.
With exceptions noted below, the
rest of the world uses GSM.
| TLA or eTLA |
|
in kbps |
Covers (US pop) |
(source: IDC) |
some major North American carriers |
| AMPS | Advanced Mobile Phone System |
|
|
42 million* | numerous (Ed.
note: AMPS will no longer be FCC-mandated as of Feb. 2008, and the
majority of providers no longer offer CDPD data service via AMPS). |
| CDMA | Code Division Multiple Access |
|
|
40 million | 3 Rivers, Alaska Digitel, ALLTEL, BellMobility, Blackfoot, CellCom, Cellular 2000 of St. Cloud, Centennial, Cricket, Disney, Eatel, Horizon, Inland Cellular, PrimeCo (IL & Houston), Qwest, Sprint, Telus Mobility, US Cellular, US Unwired, Verizon, WirelessNorth. |
| GSM | Groupe Spécial Mobile |
|
|
10 million | Cingular (including the former ATT Wireless), Fido, PowerTel, T-Mobile (formerly Ariel, Powertel, Ominpoint and Voicestream) |
| iDEN | Integrated Dispatch Enhanced Network |
|
|
7.7 million* | NEXTEL, SouthernLinc, Telus Mobility |
| TDMA | Time Division Multiple Access |
|
|
20 million | At one time, carriers included ATT Wireless (pre-merger customers), Bluegrass, CellularOne, Cellular South, CenturyTel, Inc., Cincinnatti Bell, Dobson Cellular, EDGE, Hickory Tech, Illinois Valley, Midwest Wireless, MobileTel, Pioneer/Enid, RogersATT, SunCom, Unicel Wireless, US Cellular. (Cingular had offered TDMA in Midwest & Dixie sans Carolinas, east Tennessee & coastal GA.) |
For a different look at the
same issue, click
here or here
and here
for a breakdown of customer head count by US wireless company.
¿Can I use IR to connect through a mobile for data service?
Possible, yes, as are cables,
but Bluetooth is
by far preferred if you wish to 'tether' your handheld to the Internet
through your mobile phone.
¿What's the difference between 'PCS' and cellular?
PCS is just cellular in the
1900mHz band. Originally, the FCC thought PCS would bring us extra
features (paging, caller ID, et al.), but the non-PCS (800mHz) digital
cellular companies added the extra features of PCS to their
systems, so today PCS is just a marketing buzzword.
AMPS is "good ol' analog"; then, there's N-AMPS, which is AMPS with narrow (10kHz bandwidth instead of 30kHz) which triples the number of users in the FCC allotment of frequencies allowed any one company. Herein I will use AMPS to refer to both.
You could, I suppose, use an analog modem with an AMPS phone for data, but throughput would really suffer, especially since AMPS and its variants are on the way out; the FCC mandate for legacy carriers to support AMPS ends in February of 2008, and CDPD data servie has been discontinued by the majority of providers. AMPS uses frequencies in the 800mHz band which carry farther and penetrates buildings better than PCS. There were Cellular Data Interfaces for 'bag phones' (old 3w AMPS celmobiles). However, the two extra conversions, digital-to-analog and analog-to-digital, realliy hikes the error rate and therefore slows the transmission speed.
AMPS is also a voice backup if
you have a 'dual mode' mobile; since 95% of the US population lives
where
there's AMPS coverage, it's a valuable safety net if your digital
carrier doesn't cover you when you are out in the boonies.
CDMA (IS-95A) mobile phones when connected to a handheld now provide 14.4kbps data throughput, suitable for text e-mails but not web-surfing or e-mail with much HTML or attachments. CDMA systems are in North and South America, Israel, Australia, New Zealand, central Africa, greater Russia and eastern Asia. Providers in Japan, Singapore, Hong Kong and South Korea use the IS-95B variant of CDMA to provide 64kbps data service since 2001, and CMDA is the sole system in South Korea.
Sprint and its MVNOs (Mobile
Virtual Network Operators, e.g. Cricket, Disney, Qwestm et al.) use
1900mHz
('PCS') frequencies. Verizon uses 800mHz frequencies, so
incompatabilities may exist if your device is not dual-band.
CDMA is also the foundation of W-CDMA (on the GSM upgrade path), as well as CDMA2000's 1xRTT and 1xEV for more bandwidth. 1xRTT was "2.5G" technology and 1xEV-DO is "3G" with more capability and speed. Sprint offers it (called 'PCS Vision') nationwide, as does Verizon. It offers substantial cost, time-to-market and spectral advantages for TDMA, CDMAone, analog and GSM operators, as well as newly licensed 3G operators.
Verizon launched 1xRTT in the continental US with IMTS CDMA2000 in the Northeast U.S., from Norfolk, VA, Washington, D.C., Baltimore, Philadelphia, New York, up to Boston and in Portland, Maine; in Silicon Valley and Bay Area of Northern California; in Salt Lake City, site of the 2002 Winter Olympics. The second wave of CMDA2000 expansion in April 2002 included Buffalo, Rochester, Pittsburgh, Chicago, St. Louis, Dallas, Houston, Miami, West Palm Beach, Tampa, Lakeland, Key West, and Portland (Oregon).
The first one-piece WinCE
PDA-phone in the US is the Audiovox
"Thera", also CDMA.
1xEV
is now broadly deployed (e.g., Verizon's VZAccess)
and provides radically
faster throughput.
GSM systems generally dominate beyond the Americas.
GSM provides 9.6-14.4 kbps data feeds on its cellphones using a version of TDMA different from the IS-136 version used by ATTWS et al.; see US roaming map. GSM is also the Euro standard (except for Russia and Romania which have both CDMA and GSM), but North American GSM mobiles use different frequencies (PCS/1900MHz, and 800MHz from Cingular) than Euro GSM mobiles (900MHz & 1800MHz). Don't expect to use your GSM mobile on both continents unless you have a 'world phone' including 900MHz and 1800MHz.
GSM is very range-limited because it uses the older TDMA technology to time-slice the spectrum. Don't expect long range even if you have line-of-sight with GSM (i.e., mountaintops).
Some GSM mobiles have infrared
('IR') built-in as well as a 'data modem'. Some don't. Make
sure to get both if you want to use GSM, or go Bluetooth.
GPRS bands multiple channels together for more bandwidth (that is, if those channels are available). However, Moto admits at their GPRS website for developers, "With current handsets the real data rates are about 15 kb/s using TCP/IP and about 22 kb/s using UDP/IP." The FCC confirms power problems in current handsets cap GPRS at about 20-30 kbps. Moto mobiles are shown here, BTW, and here's a list of other GPRS mobiles.
The next step up is EDGE, with HSDPA
to follow. GSM operators typically expect
to migrate to W-CDMA (sometimes called UMTS), a less sophisticated CMDA
variant which does not permit downwards compatability (as CDMA2000
does) and demands large contiguous chunks of spectrum (very difficult
in heavily built-out markets like major metro areas).
TDMA (AKA IS-136, ANSI
136, et al.) systems supported data once, but no more. TDMA is
very range-limited
because it allocates slices of each frequency to different users
technology to time-slice the spectrum.
Don't expect long range even if you have line-of-sight with TDMA (i.e.,
mountaintops) as by the time the signal gets back, the cell system has
moved on to the next user. TDMA was popular in the Americas,
New Zealand, parts of Russia and Pacific Asia, but most carriers have
moved to GSM or CDMA.
iDEN is a
proprietary Motorola system, used by NEXTEL, Southern Linc and others,
which integrates a mobile radio system with cellular-like features. iDEN
is range-limited
because it uses the older TDMA technology to time-slice the
spectrum. Don't expect long range even if you have line-of-sight
with iDEN (i.e., mountaintops).
¿Where can I learn more?
Here's another explanation of cellphone transmission standards (from a CDMA vendor).
Can I confuse you any further? Read the FCC report on cellular and paging systems.
Here's another FAQ
on wireless. Phonescoop
is pretty good, too.
¿Where do I get a current version of this FAQ?
This FAQ currently lives at http://www.503bartley.com and at http://kiloseven.blogspot.com
¿Where do I contact
you?
Drop me a note with problems at
my email in the web log, above.
John E. Bartley, III
Telcom sysadmin, Portland OR
http://www.503bartley.com
