| Author |
Wireless roaming(helicopter project)
|
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| Martin Holm Pedersen 2005-09-24, 6:58 pm |
| Hey everyone.
Im a part of a project where we are designing a robust communication
system for a model-helicopter with a combination of Wlan and radio
modem. The idea is to use Wlan when it is within range and switch to
radio modem otherwise. Both connections use tcp/ip(The radio modem via SLIP)
We have worked out how to write an application which can do this in an
applikation. However, the best solution would be to construct a layer
between the tcp-layer and the applikation-layer to manage the shifting
connection-availability. The theory is that in this way it would be
possible to connect to the helicopter via ssh or ftp and maintain those
connections even when the connection shifts from Wlan to radio-modem and
vice versa..
My question is this.. Is this even possible to write an application that
can facilitate continous connection from the ssh/ftp-client though? That
is without having to rewrite the tcp-protocol or something :-)
If anyone has some pointers regarding what is needed to do this i would
be very much appriciated.. Anyone know of any other similar projects?
Kind Regards
Martin Holm Pedersen
Group 736
Aalborg
Denmark
| |
| Mr. Uh Clem 2005-09-25, 6:59 pm |
| Martin Holm Pedersen wrote:
> Hey everyone.
> Im a part of a project where we are designing a robust communication
> system for a model-helicopter with a combination of Wlan and radio
> modem. The idea is to use Wlan when it is within range and switch to
> radio modem otherwise. Both connections use tcp/ip(The radio modem via
> SLIP)
>
> We have worked out how to write an application which can do this in an
> applikation. However, the best solution would be to construct a layer
> between the tcp-layer and the applikation-layer to manage the shifting
> connection-availability. The theory is that in this way it would be
> possible to connect to the helicopter via ssh or ftp and maintain those
> connections even when the connection shifts from Wlan to radio-modem and
> vice versa..
>
> My question is this.. Is this even possible to write an application that
> can facilitate continous connection from the ssh/ftp-client though? That
> is without having to rewrite the tcp-protocol or something :-)
>
> If anyone has some pointers regarding what is needed to do this i would
> be very much appriciated.. Anyone know of any other similar projects?
>
> Kind Regards
> Martin Holm Pedersen
> Group 736
> Aalborg
> Denmark
What's the nature of the communications?? TCP would be bad for
realtime because of the delays which will occur in the case of
dropped packets. I should think that ssh would make it even
worse because of the extra handshaking at connection
(re)establishment.
--
Clem
"If you push something hard enough, it will fall over."
- Fudd's first law of opposition
| |
| Martin Holm Pedersen 2005-09-26, 8:01 am |
| Mr. Uh Clem wrote:
> Martin Holm Pedersen wrote:
>
>
>
> What's the nature of the communications?? TCP would be bad for
> realtime because of the delays which will occur in the case of
> dropped packets. I should think that ssh would make it even
> worse because of the extra handshaking at connection
> (re)establishment.
>
>
Hello.. Thank you for your reply. The communication is split in two
parts, none of which have any real time requirements. The one im worried
about is the ssh-connection which is going to be used to upload
flight-plans and such while in air. This means that the connection
cannot be broken at any point during flight, not even during the
transition between Wlan and radio-modem. Is it possible to maintain the
connection without any (re)astablishment. I'we been looking into the
prospect of multicasting. That is, just sending all the data
simultaniusly though both Wlan and radio, so if one fails the other one
will take over without any loss in connection at the app-layer..
Thanks again
- Martin
| |
| A. Melinte 2005-09-26, 7:00 pm |
| > modem. The idea is to use Wlan when it is within range and switch to
> radio modem otherwise. Both connections use tcp/ip(The radio modem via
SLIP)
Take a look at the mobile IP RFC
Regards
a.
| |
| Martin Holm Pedersen 2005-09-26, 7:00 pm |
| A. Melinte wrote:
>
> SLIP)
>
> Take a look at the mobile IP RFC
>
> Regards
> a.
>
>
Thankyou.. You saved my life. That was exactly what i needed..
The mosquitonet implementation sounds promising..
Thanks again.
- Martin
| |
| A. Melinte 2005-09-26, 7:00 pm |
| >
> The mosquitonet implementation sounds promising..
>
I have the impression it is somehow outdated - it mentions RFC2002 whereas
the latest mobile IP RFC I know of is 3344. The download page mentions
kernel 2.2, no plans for 2.4 and we are at 2.6. But there is probably some
other group developing newer software? Hopefully an old implementation can
suit you - if you can fully control your clients and agents? Unfortunately,
I do not know of any free implementation.
Regards
a.
| |
| Martin Holm Pedersen 2005-09-26, 7:00 pm |
| A. Melinte wrote:
>
>
> I have the impression it is somehow outdated - it mentions RFC2002 whereas
> the latest mobile IP RFC I know of is 3344. The download page mentions
> kernel 2.2, no plans for 2.4 and we are at 2.6. But there is probably some
> other group developing newer software? Hopefully an old implementation can
> suit you - if you can fully control your clients and agents? Unfortunately,
> I do not know of any free implementation.
>
> Regards
> a.
>
>
Yes.. I see your point. However the main thing is to get the hang of the
socket handover techniqe.. Do you know anything about the particular
techniqe? The network is deterministic and under our control. I don't
think we don't need the advanced stuff..
-Martin
| |
| A. Melinte 2005-09-26, 7:00 pm |
| > socket handover techniqe.. Do you know anything about the particular
> techniqe?
Nothing, except to dig into the sources.
Regards
a.
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