Originally Posted by s/v Jedi
I have some questions for you, if you don't mind:
link speed. You write that connecting an AxcessPoint ir WXA-200 increases the speed from 2,4kbps to 3.0kbps. How does that work, as the satellite
link that the phone
has is 2.4kbps maximum? I think you have been misinformed and observed higher rate is the result of data compression
, which a lot of devices, incl. Pactor
modems, can do.
2. You claim the isatphone is 2.0kbps download and 1.6kbps upload. But Inmarsat claims the same 2.4kbps as Iridium. Are they lying?
3. You claim that satphones are 3 to 5 times as fast as Pactor
3. However, the satphones you reference are both 2.4kbps rate, while my Pactor modem
is 2.7kbps which is actually faster than either satphone can provide. I regularly download gribfiles over Email
and this is faster over my Winlink Pactor than it is over my satphone, which is conform the specifications.
4. You state Iridium will provide us with FREE email
when we buy the AxcessPoint device. How does that work, do they send you cards with minutes as you use them? Or can you call a free number? Also, are there limits to this FREE service
? Or is it not free and must we pay the regular full price
for minutes used? Might it be that they just give a free email address like Hotmail, GMail etc. also do without the need to buy equipment
Answers to your questions...
Iridium actually runs faster than 2400 baud application to application. What slows it down is contention for the PPP connection by other system and user level process that want access to the net. When measuring application to application transfer rates using the USB we routinely see between 12-18 Kbytes per minute over Iridium. This is true for both Macs and Pcs. When doing the same measurements with an AxcessPoint wifi
we see transfer rates > 3000 baud 3118 being the record
so far. However... note that your milage will vary depending on signal strength, occlusions, satellite
Bottom line.. the firewall on the AxcessPoint Wifi and WXA-202 allow you to squeeze the most out of your connection.
2. Yes.. that is the claim... but we don't see that. The Isatphone is considerably slower than Iridium when measuring application to application transfers. There are some distinct advantages of iridium over isatphone here they are...
a. iridium has 20 second billing increments. Isatphone has one minute inclurements. This mens that you play for two minutes of airtime on isatphone if you rseession is 61 seconds long. Note the case with iridium.
b. It takes over 1 minute to bring up a ppp connection with isatphone. it takes 15 seconds for iridium. This means that in isatphone you blow a full minute of airtime before you transmit a single
byte of data.
c. Iridium is considerably faster than isat. this is especially true on uploads.
d. iridium line turn around latency is 1.4 seconds. Its 5 seconds for isatphone. When you take into account protocol overhead this is a real killer. Take SMTP for example... SMTP requires 5 line turn arounds for setup and one additional line turn around for each email address. So... to send an mail with 5 recipients over isatphone takes 50 seconds of overhead before you send a single
byte of data. with Iridium 14 seconds.
Using optimized compression software
for both iridium and isatphone is essential.... However, without it isatphone just doesnt work.
3. I said on average.... You rarely (never) get 2400 baud out of pactor. A smoking pactor III connection gets you 10 kbytes per minute. A good connection gets you 5 kbytes per minute. An average connection 1-3 Kbytes.
AND the line turn arounds for pactor are dismal. Once you get it going in one direction it does ok but as soon as you have to turn the line around the protocol really slows down.
4. Free email does not mean free airtime. You get the software
and an email account at iridium which allows you to do email with out having to subscribe to a service
. i.e. free email. You still pay for the airtime. Free email is only available to users with 9555 or 9575 phones who also own an AxcessPoint Wifi device. Chekout the iridium.com or more info.
The email has been optimized for transfer over satellite phones and works very well. We should know since we did the implementation... AxcessPoint Mail & Web is powered by XGate. So... you get the same performance as you do with our XGate email software.
Note that there are some advantages to subscribing to a comercial service over getting the email for from from iridium. Iridium only allows access to the email through their airtime. You can't use webmail or an internet
connection to check for mail. The system also only works for the 9555 and 9575. XGate on the other hand allows you to use wifi, cell phones, satellite phones, and other connectivity methods to get your mail. So although you might pay $20 per month for xgate the flexibility might offset the cost.