Sierra
Wireless PC AirCard 750 for Laptops
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Simply plug the Sierra
Wireless PCMCIA card into your laptop or PDA and within
seconds, you're connected to the internet.
This is a convenient
way of getting internet access anywhere there is cell phone
service. But it is also expensive to buy, and gives
only a very slow connection speed. |
Here's a different approach to
getting internet access while you're traveling.
Because it connects to the
internet through a cell phone service, it has the great benefit
of working in much of the country, unlike Wi-Fi. It can
even work while you're being driven in a car.
But the theoretical promise of
this device is not equaled by its practical real-world use.
Introductory Comments - Why Buy
a Sierra Card?
The Sierra card is
essentially a cell phone built into a PCMCIA card. Instead
of connecting to the internet via a modern digital cellphone,
you can use this Sierra card instead. You can even plug a
headset into the Sierra card and use it as a regular cellphone
(but only while it is plugged in to a laptop - it has no
independent power supply).
Why would you buy a wireless
modem card that clumsily doubles as a telephone, at a $300 cost,
rather than a telephone that also provides the identical
wireless modem service, and probably available for free when
signing up for cell phone service?
I asked this question of
Sierra Wireless' Manager of Marketing Communications, Kathleen
Gallagher. She never even replied to my email, and so I
can only assume that she, like me, is unable to come up with any
convincing reason why you should go out and buy her expensive
product.
Now that most cell phones
have built in data capabilities, it does seem that this is a
unit which no longer has a niche in the marketplace.
But, in case you're still
interested, read on.
What you get
Sierra Wireless PC AirCards
are Type II PCMCIA devices. They fit entirely within the
PCMCIA slot, with nothing sticking out except for the external
aerial. This means the card is not likely to get damaged
if you transport it while inside your laptop.
Each Sierra Wireless card
has a detachable external aerial. This can swivel and tilt
- promotional material says so as to allow you to position it
for the best signal, but in reality, the main of the swivel/tilt
is to stop it being broken off.
And, if you do break the 3"
aerial, because it is detachable, it is also replaceable.
It is much less money to buy a replacement aerial than a
complete replacement card. But, at a $35 replacement cost
- for what is little more than a piece of wire - you'll still
want to be careful with your aerial.
The removable antenna has
another benefit, too. You can swap the on-card antenna for
a remote antenna, and then run a coax cable from the remote
antenna to the card, giving you (potentially) a much stronger
signal, meaning more range and faster data transfers.
The card comes complete with
a Quick Start guide, a regular manual (with about 15 small pages
of information) and a CDrom with software to be installed onto
whatever computing device you are plugging the Sierra Card into.
Like most other PCMCIA
cards, the unit comes in a nice protective clear plastic carry
container.
When purchased through a
service provider, it also comes with a SIM card containing your
account information for that service provider.
Most people will want to get
a SIM and dedicated account for their Sierra card.
If you preferred, you could
buy a Sierra card by itself, and then use the SIM from your
regular GSM phone; simply swapping the SIM between the phone and
the card, depending on which you wanted to use. But it is
not clear why you'd want to do that!
The Sierra Card is
compatible with Win 95, 98, Me, NT4, 2K, and XP. It is
also compatible with PDAs running PPC, PPC 2002 and HPC2000.
It is not compatible with Mac, *NIX or other OS devices.
The AirCard 750 is a
tri-band unit, compatible with GSM/GPRS cellular service in the
US (1900 MHz) and most of the rest of the world (900/1800 MHz).
It has a non-transferable
one year limited warranty.
Installation
The Quick Start Guide has a
simple four or five step procedure to install the software
drivers onto your laptop. You install the software first
and then plug the card into the laptop second, and both the
Quick Start Guide and the installation program make certain you
understand this.
The installation program was
fast and simple. It didn't ask me any difficult questions,
didn't require me to key in any ridiculous long serial numbers,
and did nothing unexpected or undocumented. Bravo.
I inserted the SIM into the
Sierra card, and with T-Mobile's help, quickly set the user
account details, and then it was working. Wow - networking
didn't used to be this easy!
Usage
Connecting to the internet
is simple.
There is nothing to dial, nothing else to configure. Just click the
'connect' button,
and you're online.
It can take over 50 seconds
for the device to be recognized and initialized and connected to
the internet. This is, of course, not a huge delay, and
comparable to what you'd wait for with a regular modem dial up
connection.
Like all GPRS devices, it is
an 'always on' type connection, and you'd never normally want to
disconnect it, unless either
(a) You had a faster
network connection
(b) You were trying to
save battery power
(c) You're being
charged for data usage rather than having an unlimited use
account
If you want to disconnect
it, simply click the 'disconnect' button in the control
window and it disconnects.
Performance (AirCard 750)
Note that different
performance will be experienced with the different model
AirCards on different types of cellular networks.
GPRS performance varies
depending on how many channels are open for the connection.
The Sierra 750 is a GPRS Class 12 device, capable of taking over
up to five channels simultaneously, with a maximum of four being
used for either uploading or downloading, and the balance being
used for data being sent in the opposite direction
simultaneously.
Each GPRS channel represents
about 10-15kb of bandwidth.
If the cell site is
servicing very many data requests simultaneously, you'll get
fewer channels than if it is only servicing a few data requests.
Actual speed depends both on
the number of channels you get and also the signal quality.
I tested the card at
www.bandwidthplace.com which reported performance of (at
various different times) 37.4 and 39.5kb downloading, while
signal strength was showing at three out of the four bars.
This performance is consistent with three or four channels being
allocated to downloading. Repeating the test with a 10dB
degradation in signal quality (now showing two bars) slowed the
speed down to 33.6kB.
Testing for latency, I did
some pings of www.google.com.
These varied enormously, indicating some congestion and
instability in the wireless data link. The first set of
four pings resulted in one lost, and the other three averaging
2125 msec. The next set all returned, with an average of
874 msec. The next set averaged 906 msec. The next
set averaged 1601 msec. The highest time (apart from the
timed out lost ping) was 3829 msec and the lowest was 589 msec.
By comparison, I dialed out
on a modem with a 53.2k connection, and got pings averaging 220 msec
with little variation in timing. This was five times
faster than from the Sierra card.
And then, for the sake of
completeness, I swapped from the Sierra card to a LAN
connection, and Google pings then came in at a consistent 45-46 msec
- a massive 25 times faster than the Sierra card!
The much longer latency and
occasional packet loss means that the effective throughput of
the Sierra card will probably be appreciably lower than you'd get on a regular phone
modem connected at the same raw data speed. But, sometimes
balancing this is the fact that the Sierra card can transmit and
receive data simultaneously, whereas a phone modem only works in
one direction at a time. A lot depends on the type of
application you're running - a simple ftp streaming file
transfer might be faster with the Sierra card, but something
more interactive like email or web pages would not be.
Both the Sierra card and
regular modems support V.42bis type data compression, which can
sometimes speed up effective data rates.
Clearly, GPRS data
connectivity is no speed demon, and the simple bandwidth
measurement is only part of the overall performance picture.
It is also very
inconsistent. Late in the evening, I went to repeat my
testing (originally done in the middle of the afternoon),
expecting to get better results. I was unable to do this.
Bandwidth was so slow I couldn't even open up any web pages.
Some extra throughput can
possibly be obtained, if using the T-Mobile service, by changing
some proxy server settings at
https://getmorespeed.t-mobile.com . This speeds up web
page serving by reducing the size of images on pages and using
other data compression techniques. However, during
my several weeks of testing, this service was always offline for
'upgrading' so it could not be evaluated.
As a Phone
If the service plan you've
signed up for allows it, the card can also be used as a regular
phone. You manage its virtual phone capability through the
little control program, dialing numbers, accessing address
books, etc.
The unit did not come with a
phone headset. It seems miserly that a $300 unit
does not include a $5 headset.
Annoyingly, the card does
not use headsets with common three wire type plugs, but instead
requires a Nokia type connector with four wires.
And, compounding its limited
phone capabilities, you can't use it with any microphone or speakers
that might be built in or connected to your laptop (or PDA).
In operation, the card
worked much the same as a regular phone, with similar sound
quality, although perhaps the volume, at maximum, was a bit
quieter than on my Nokia 3650.
Note that this card can only
be used as a phone while it is plugged in to a powered on laptop
or other PDA device. It has no power supply of its own,
and also uses the laptop or PDA to give you a dial pad and other
control buttons.
Battery Life
The card has no power supply
of its own. It takes its power from whatever it is plugged
into.
The faster the data
connection, the more current that the card uses. With a
normal fast connection, it is using about 3 - 3.5W of power.
My laptop averages about 30W of power, and so if the Sierra card
was to be permanently in use at full speed, my typical 2 - 2.5
hour battery life would be reduced by about 15 minutes to
compensate for the extra power used by the Sierra Card.
Note that if your laptop is
not as power hungry as my P4 monster, then the impact of the
Sierra Card's power consumption will be proportionately greater.
But even if your laptop used only half the power of my Dell
Inspiron 8200, then a battery that normally lasts 3 - 3.5 hours
would reduce by about 30 - 40 minutes to reflect the impact of
AirCard.
Different Models for Different
Networks
Sierra offer three main
types of PC Card that are essentially identical, other than
being designed for each of the different types of cell phone
networks.
They are :
-
Model 750 for GSM/GPRS
service (this
is the unit tested here), compatible with
T-Mobile,
AT&T and
Cingular
-
Model 555 for CDMA service,
compatible with Verizon,
Cellular One, US Cellular and Alltel
-
Model 550 for CDMA service,
compatible with Sprint
It is fair to note that soon
these models will be obsolete, when all wireless networks move
to much faster '3G' type data services. Buying a $300 item
for a very short period of usage is something you should think
carefully about, especially with the alternative being to simply
get a free cellphone instead.
Purchase Cost
The Model 750 has a list
price of $429 if bought directly from
Sierra Wireless.
T-Mobile sells it for $350 regular price and $250 rebated price,
if you also sign up a service plan from them.
AT&T sell
them for $300.
I've sometimes noticed advertisers in the advertising bar on the
right of this column offering the card for between $50-130,
which makes it much more affordable and a more tempting
purchase. But, even at this low price, you also need to
sign up for an extra line of wireless service - you're paying
both to buy the card and then to use it (compared to using the
inbuilt capabilities of a data capable phone).
Monthly/Usage Costs
AT&T have plans ranging from
$30/month up to $80 a month. The $80/month plan includes
unlimited data transfer, the other plans have very limited
amounts of included data transfer (10 - 60 MB) and charge
between $1.30 and $3 per extra MB; plus extra charges if you're
roaming (even on the unlimited plan). Voice is extra, with
no free minutes; all calls are charged at 40c/minute and extra
if roaming outside your 'home area'.
T-Mobile have an
unlimited/anywhere service for $30/month, making it by far the
better value.
Note that GSM/GPRS Sierra
cards can be locked, the same as
phones, tying them to only one network provider, so if you
buy a card from, eg, AT&T, you may not be able to subsequently
use it with a T-Mobile SIM.
One more comment about
monthly fees. T-Mobile will charge only $20 a month to add
unlimited data transfer to an existing cell phone account.
This lower cost is another reason to consider using a cell phone
for data access, rather than buying an additional expensive
Summary
If you're an ultimate road
warrior, then possibly you might get some benefit from the easy
connectivity and convenient that these cards offer.
But for most of us,
answerable to someone else for how we spend our travel and
technology budgets, it will be hard to justify the investment in
this costly card and extra for the monthly connectivity.
And, quite ignoring the cost
issues, using GPRS or similar service to access the internet is
the slowest of all seven options discussed on our
Connecting to the Internet page.
That is okay when it is a more or less free 'bonus' feature of a
regular cell phone, but not so satisfactory when it requires an
expensive extra piece of equipment and extra monthly service
fees.
Not recommended.
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Originally published
23 January 2004, last update
21 Jul 2020
You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.
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