PDA

View Full Version : wifi radio theory


TomCerul
01-24-2011, 12:03 PM
We're having some issues getting the wifi radios to talk to each other. What's the general configuration theory? Are both routers supposed to be bridges? Just one? Why would we run one as an access point at practice but as a bridge during competition? That violates my "Practice like you want to perform" rule.

The classmate can connect directly to the white DLink (ping) through the internal wifi card. I'm having a hard time understanding what the blue/black linksys is supposed to be doing at a high level though. I know it's supposed to provide better power for the classmate but is it acting as a bridge or what?

Thanks for you time!

Mark McLeod
01-24-2011, 01:33 PM
The 2011 wifi "standard" configuration uses just

the Classmate wireless
the white KOP D-Link on the robot (in AP mode)Other configuration options exist depending on what you want to get out of life, but that's the basic setup.

At Competition we get the addition of the FMS Field AP, so we turn all our individual team APs into bridges instead.

If you want to "Practice like you want to perform," then you can add your old Linksys router to pretend to be the Field Router. It won't be the same of course, because the field setup uses different equipment and virtual private networks for each team, network switches between the Classmate and the Field Router, 60' of Ethernet cable, network monitoring software, and a Big Brother FMS, etc.

Alan Anderson
01-24-2011, 03:04 PM
We're having some issues getting the wifi radios to talk to each other. What's the general configuration theory? Are both routers supposed to be bridges? Just one?

You should be using only the D-Link DAP-1522. Nothing more. If all your computers are capable of Wi-Fi, there should be no bridges. If you want to connect a wired-Ethernet-only computer, you can plug it into the DAP. If you want to add a bridge of your own, okay, but you're on your own for configuring it.

Why would we run one as an access point at practice but as a bridge during competition? That violates my "Practice like you want to perform" rule.

During competition, the access point is provided by the Field Management System. During development, there is no FMS, and the DAP must be in Access Point mode in order to connect the Driver Station to the robot.

The classmate can connect directly to the white DLink (ping) through the internal wifi card.

Sure it can. If yours does not, there is likely a misconfiguration somewhere. Your D-Link DAP should be set in Access Point mode, with its SSID set to your team number, and wireless security disabled. The Driver Station software configures the Classmate networking appropriately, based on the team number you provide to it.

I'm having a hard time understanding what the blue/black linksys is supposed to be doing at a high level though. I know it's supposed to provide better power for the classmate but is it acting as a bridge or what?

Last year's Linksys router is not used this year.




If you want to play around with alternate (and unsupported) network configurations, it should be possible to use the old blue Linksys as a fixed access point with your team number as its SSID on the 2.4 GHz band, configure the D-Link as a bridge to the wireless network thus created, and make sure everything is set to the appropriate IP addresses (similar to last year's setup). But you should first configure things as directed in the "How to" documents and get them to work the way they are supposed to, before starting any hacking.

Mike Betts
01-24-2011, 03:50 PM
... Your D-Link DAP should be set in Access Point mode, with its SSID set to your team number, and wireless security disabled...

Alan,

While I am sure that what you say will work, it is not what the teams were directed to do.

As per this document (http://usfirst.org/uploadedFiles/Robotics_Programs/FRC/Game_and_Season__Info/2011_Assets/Kit_of_Parts/How_to_Configure_Your_Radio.pdf), they were instructed to enable WPA-AES security and enter a passphrase (see the attached picture). We used 3518WPAKEY as per the example. I told the students that we would be getting a different, random and unique passphrase at the competition.

If there contradicting instructions in a different document, I would appreciate it if you could post a link.

Thanks,

Mike

Alan Anderson
01-24-2011, 04:14 PM
As per this document (http://usfirst.org/uploadedFiles/Robotics_Programs/FRC/Game_and_Season__Info/2011_Assets/Kit_of_Parts/How_to_Configure_Your_Radio.pdf), they were instructed to enable WPA-AES security and enter a passphrase (see the attached picture). We used 3518WPAKEY as per the example. I told the students that we would be getting a different, random and unique passphrase at the competition.

If there contradicting instructions in a different document, I would appreciate it if you could post a link.

That's only the first half of the instructions. It's specifically the "Configuring a radio for Competition" part. I don't know why it's in there, because it isn't how anyone is expected to use the system during development, and I think the settings should all be overwritten anyway when the kiosk does its stuff at competition.

The rest of the instructions, under the heading "Configuring a Radio for Access Point Use", tell you only to set the SSID and frequency band. The security remains disabled under AP mode.

Mike Betts
01-24-2011, 04:59 PM
That's only the first half of the instructions. It's specifically the "Configuring a radio for Competition" part. I don't know why it's in there, because it isn't how anyone is expected to use the system during development, and I think the settings should all be overwritten anyway when the kiosk does its stuff at competition.

The rest of the instructions, under the heading "Configuring a Radio for Access Point Use", tell you only to set the SSID and frequency band. The security remains disabled under AP mode.

Alan,

Because of your competence in such matters, I hate to disagree. But... It works just fine in AP mode when the WPA-AES is left on. You only have to enter your passphrase into the driver's station (and development station, if separate) and it works like a charm. This is our development configuration at Lecanto HS.

Nowhere did I see where WPA-AES was optional. The section it was in is titled "Configuring a radio for Competition:".

Regards,

Mike

Clayton Yocom
01-24-2011, 06:41 PM
To sound less blunt, the access point can be used with security, but any problems with it are less of a problem than to use without security. What is someone gonna do, access your cRIO? lol.

Alan Anderson
01-24-2011, 10:53 PM
Because of your competence in such matters, I hate to disagree. But... It works just fine in AP mode when the WPA-AES is left on. You only have to enter your passphrase into the driver's station (and development station, if separate) and it works like a charm. This is our development configuration at Lecanto HS.

Having security on the D-Link in Access Point mode works fine, certainly. It's just not how the instructions tell you to set it up. I've not seen anything in the documentation that mentions having to enter a passphrase on the Driver Station computer.

Nowhere did I see where WPA-AES was optional. The section it was in is titled "Configuring a radio for Competition:".

Yes, the instructions call for WPA security when using the D-Link in Bridge mode. If you follow the instructions, however, you'll be using it that way only at a competition event.

TomCerul
01-25-2011, 09:53 AM
Very good, it sounds like we're all set already then. The classmate was talking to the DLink just fine. The students were under the impression that the classmate wouldn't have the range that we'd need for competition. As the the normal configuration is relying on the classmate, I'll defer to you guys and stop fighting with the linksys.

And thanks for the explaination about the competition AP. That makes a lot of sense.

Thank you!

rsisk
01-25-2011, 10:12 AM
The students were under the impression that the classmate wouldn't have the range that we'd need for competition.

When you are at the competition, you are connected directly to the Field Management System by a network cable. You will not be using your Classmate's wireless network during the competition.