HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 04, 2009, 12:17 PM
Registered User
Joined Oct 2009
1 Posts
Question
2.4 Ghz Technology based on..?

Just out of interest, with all the new 2.4Ghz RC systems, are they loosely based on any 802 protocols, (802.11 WLAN / 802.15 WPAN) or are the systems completely proprietary to each manufacturer?

I'm mostly interested in the hardware behind it, and have been assuming it might be built on top of 802.15.4 lower layers as they'd be perfect for the task i.e. low bandwidth (not much needed to send a few servo position bytes) and low-power consumption and can have very good range.

Don't imagine Spektrum and Futaba tell any old tom dick or harry about the specifics of their designs but if anyone can clear this up for me I'd appreciate it,

Cheers,
shifteroo is offline Find More Posts by shifteroo
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 04, 2009, 12:22 PM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,306 Posts
Hi!

There are some systems based on the ZigBit protocol (xps, Jeti), but most of the system have nothing in common, be it bandwidth, data rate, FHSS or not, number of channels used simultaneously, etc.
Julez is offline Find More Posts by Julez
Reply With Quote
Old Dec 04, 2009, 02:03 PM
Registered User
Canada, NB, Fredericton
Joined May 2002
927 Posts
Most of the other 2.4ghz systems (other than Jeti & XPS) are one-way transmissions...so they don't need the overhead of a link layer/protocol stack. So, they've basically written their own simplex protocols and defined their own signal properties (w.r.t. spread spectrum, channels, and bandwidths) within the limitations of the chipsets their each using.

D.
darkith is offline Find More Posts by darkith
Reply With Quote
Old Dec 04, 2009, 05:13 PM
Registered User
Christchurch, New Zealand
Joined Jun 2006
6,794 Posts
XPS use 802.15.4 radios, but with their own custom protocol. Spektrum use Cypress wireless USB chipsets, with their own custom protocol and much more power on the transmitters. Futaba went full-custom, and built their own chips. The others I don't know, but it wouldn't be surprising if many of them are using radio chips made for 802.15.4.
Andrew McGregor is offline Find More Posts by Andrew McGregor
Reply With Quote
Old Dec 05, 2009, 02:47 AM
Proud to eat Kraut ;-)
Julez's Avatar
Germany
Joined Dec 2003
5,306 Posts
Jeti uses the premade ZigAmp transmitter module in their modules.
Julez is offline Find More Posts by Julez
Reply With Quote
Old Dec 05, 2009, 02:56 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,773 Posts
"XPS use 802.15.4 radios, but with their own custom protocol."

Andrew, have you personally confirmed that there is anything unique going on there - not pushing you just interested.
teamdavey is offline Find More Posts by teamdavey
Reply With Quote
Old Dec 05, 2009, 04:39 PM
Registered User
Indy
Joined Aug 2007
62 Posts
An Introduction to Spread-Spectrum Communications

http://www.maxim-ic.com/appnotes.cfm/an_pk/1890
12ten is offline Find More Posts by 12ten
Reply With Quote
Old Dec 05, 2009, 04:46 PM
The reviewer
XJet's Avatar
Tokoroa
Joined Mar 2004
3,827 Posts
Quote:
Originally Posted by Andrew McGregor View Post
XPS use 802.15.4 radios, but with their own custom protocol.
Bzzt. Wrong.

Protocol analysis shows that the XPS systems used stock standard protocols. The latest versions may move away from that but the originals were not a custom protocol at all.
XJet is offline Find More Posts by XJet
Reply With Quote
Old Dec 05, 2009, 04:49 PM
Registered User
Christchurch, New Zealand
Joined Jun 2006
6,794 Posts
Jim Drew is on record on this site saying they did something to the firmware.

Now maybe that was just tweaking for latency, rather than protocol changes, but they did do something; their modules are XBee hardware, but with firmware changes.

Or at least, that's what Jim said.
Andrew McGregor is offline Find More Posts by Andrew McGregor
Reply With Quote
Old Dec 05, 2009, 05:01 PM
Xtreme Power Systems
Lake Havasu, AZ
Joined Jun 2005
15,845 Posts
We definitely have never used the stock 802.15.4 protocols. In fact, the XBEE modules have to be put into pure 802.15.4 compatibility mode if you want to use them on a normal 802.15.4 network, and we don't do that. Also, our backoff exponent and other features are not the same as true 802.15.4.

802.15.4 protocol has been used in everything from water control systems to hospital inter-communications. This technology predates 2.4GHz for R/C, so it has a long history of success in numerous other industries.
JimDrew is offline Find More Posts by JimDrew
RCG Plus Member
Reply With Quote
Old Dec 05, 2009, 05:50 PM
Registered User
Christchurch, New Zealand
Joined Jun 2006
6,794 Posts
Ah, here's Jim

Yep, protocols are more than just frame formats.
Andrew McGregor is offline Find More Posts by Andrew McGregor
Reply With Quote
Old Dec 06, 2009, 04:19 PM
Registered User
Sunnyvale, CA, USA
Joined Apr 2000
1,773 Posts
Hmmmm
teamdavey is offline Find More Posts by teamdavey
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion HK 2.4 GHz radio 6ch stuck on T6 config software mrk Radios 5 Jan 21, 2010 07:13 PM
Discussion 2.4 Ghz technology? kyle7119 Radios 5 Sep 24, 2009 11:43 AM
Sold FS E-flight LP5DSM TX LIKE NEW 2.4 GHZ w/Spektrum Technology ov10mech Aircraft - General - Radio Equipment (FS/W) 0 Mar 05, 2008 09:22 PM
Discussion 2.4 Ghz technology in Japan. seric Japan 1 Aug 05, 2007 02:28 AM
Discussion 2.4 Ghz technology limitations? khaoz Radios 5 Feb 23, 2007 03:21 PM