Pages: [1]   Go Down
Author Topic: methods of preventing RF/wireless crosstalk?  (Read 946 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 3
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Im a bit of a noob. I know for RC stuff, if you are racing with others, normally you'd switch over to another frequency band so you prevent cross talk between competitor controls-vehicles.

For arduino using RF communications, what are the methods you would use to prevent similar cross-talk scenarios in an environment where there may be more than one similar device also using the same wireless frequencies trying to communicate? I guess one method may be the baud rate but you are still limited there and sometimes you can still get cross talk by picking up the data. So what method do you suggest?

Encryption? Appending special start and end data that must be recognized to register a dataset? How does the receiver pull the correct signal in an environment drowned with the same frequency signals?
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 545
Posts: 27353
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

You could use frequency hopping.
Take a look at parts like DNT24P
http://www.rfm.com/products/spec_sheet.php?record=DNT24P
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

the land of sun+snow
Offline Offline
Faraday Member
**
Karma: 159
Posts: 2916
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

This is a common problem today for the 2.4-Ghz wifi band. Total BW [bandwidth] is only 80-Mhz,
which can accomodate only 3 wifi channels without severe overlap. And obviously, if you look
in your PC's "View Wireless Networks" window, you'll typically see a dozen of so wifi routers
within close proximity. Plus, XBee works in the same band, plus microwave ovens work at
the top of the same band.

Why does this even work at all? Mainly through something called spread-spectrum DSSS [not
the same as frequency-hopping, BTW],

http://en.wikipedia.org/wiki/Direct-sequence_spread_spectrum
http://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum

They also use multiple-access techniques to prevent conflicts.

http://en.wikipedia.org/wiki/Multiple_access





Logged

Offline Offline
Newbie
*
Karma: 0
Posts: 3
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Cool thanks for the info.

How do you actually implement this in software using simple cheap RF transmitter/receiver pair or transceiver modules sending vial serial?

Or is this stuff usually done at hardware level by a dedicated controller?
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 545
Posts: 27353
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Usually done at hardware level by a dedicated controller - by a part like the DNT24P.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

the land of sun+snow
Offline Offline
Faraday Member
**
Karma: 159
Posts: 2916
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

We just buy off-the-shelf devices like Bluetooth, Zigbee, and other 2.4-Ghz transceivers,
available from many sources.

Popular with Arduino are the XBee shields, which were first designed to mount the XBee zigbee
module from digi [old Maxstream], but now there are many modules that mount on the same shield,
with some working at other frequencies, BT, and also wifi.

http://www.digi.com/products/wireless-wired-embedded-solutions/zigbee-rf-modules/zigbee-mesh-module/

http://www.seeedstudio.com/depot/index.php?main_page=advanced_search_result&search_in_description=1&keyword=beefamily

http://rovingnetworks.com/products/RN_XV
Logged

Pages: [1]   Go Up
Jump to: