Neither iPhone or OpenMoko are revolutionary
andreas at kostyrka.org
Thu Jan 18 21:39:22 CET 2007
* Renaissance Man <renaissanceman at macmail.com> [070118 20:20]:
> And why do you keep making moot points about the technical problems of WiFi on a mobile device when many such devices already have it and Neo will eventually have it too?
Because currently it works well, because almost nobody uses it. So you
get 11Mb/s brutto, which is more like 4-5Mb/s true bandwidth. Now
despite that there are other codecs available, most sip providers ask
for 2x100kb/s bandwidth during a call (up/down stream).
200kb/s is usually easy accomodated by a hotspot. 10 people doing
200kb/s will become jerky. And yes, most hotspots have just a puny
ADSL connection. Typical uplink speeds are 64-128kb/s for these.
I've got locally the biggest non-ADSL2 package, and I get 768kb/s
upload-wise. Meaning that my WLAN at best can conduct 3-4 calls at the
same time. But what that means in reality is, that there might be
hotspots that are not capable to do even one VoIP call, and most will
max out their upload speed with 1-2 calls. This might be not the case
with a network like the one you mentioned in London. OTOH, it might be
an issue, depending upon their backbone.
Furthermore, QoS on WLAN is extremly difficult by the nature of the
thing: it's a shared medium with collision detection. That means, you
need to have a strict oversupply of bandwidth to do VoIP.
WLAN (11mbit ~ 4mbit usable) can probably support 10 calls concurrently.
ADSL (64kb/s => 768kb/s uplink) can probaby support 3-4 calls at most,
and in some extreme cases not even one (you just need one other user
that does some transfers, and your phone call quality is gone).
So while one guy walking around London and doing VoIP via WLAN
wouldn't probably have problems, thousands of them running around will
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