I'm not sure if this applies to all mica2's, or just some older versions. I'm also not sure about OEM's. You'll have to screen yours nodes yourself to see if this applies.
Our experience (and we're not alone) has been that there was not a good 50-ohm impedance match on the passive network connecting the radio chip with the antenna. Where there should be 50-ohm traces on the PCB, there is not. This steals a few dB of output power, and significantly decreases range (you double the range for every 3 dB, so even 3 dB less is half the range). Mica2Dot's are even worse: in an attempt to meet size specifications, the matching network is split across two sides of a PCB. This is never a good idea, because you may not be able to guarantee the reliability of the radio's matching network. With the matching network separated, small manufacturing differences of the PCB can cause significant differences in RF response from module to module. And, mica2dot's don't have a sufficient ground plane. Finally, the curly-q loop thing added to the end of the wire antennas that come with the mica2dot's are a bad idea. This adds some unnecessary horizontal polarization to the wave. A vertically polarized wave is much better. Horizontal polarization gets eaten quickly by the ground. Straighten out those wire antennas, and add a ground plane. -David -----Original Message----- From: Michael Schippling [mailto:[EMAIL PROTECTED] Sent: Monday, April 14, 2008 8:05 PM To: David Moss Cc: 'Edgar Charry'; 'Eric Keller'; tinyos-help@millennium.berkeley.edu Subject: Re: [Tinyos-help] Pumping up bandwidth - Mica2Dot/Mica2 YOW!!! Another information packed post (IPP). Maybe we could start a radio theory page on our new improved doc site? But what's "that broken matching network" mean? MS David Moss wrote: > Manchester encoding. And CSMA. > > > > Manchester halves the throughput. Instead of 76.8 kbps, Manchester will > force your radio to transmit at 38.4 kbps. Getting rid of Manchester > may not be a simple task: it's there to zero out the energy seen by a > receiver, so it can easily know that it's receiving valid data. > > CSMA causes your transmitter to share the channel with other > transmitters, and the channel checks may be spaced relatively far apart > which dramatically decreases throughput. > > > > The CC1000 radio could be a really kick-ass radio if it were implemented > properly. The ability to easily enable/disable Manchester, CSMA, etc. > (among other things) would really improve its situation. The CC1000 > radio is much more energy efficient than the CC2420 radio, and can > transmit a lot farther than the CC2420 radio (but that broken matching > network on mica2's and especially mica2dot's really cause everyone > problems). It's unfortunate so many people dismiss the CC1000 radio as > obsolete, when it could really outperform their radios in terms of > efficiency and range (not throughput). > > > > 29 bytes is only a software (and RAM) limitation. Increase it by doing > a CFLAGS+=-DTOSH_DATA_LENGTH=50 or something in your Makefile. Removing > unnecessary fields from the CC1000 header will decrease the > header:payload ratio and increase payload throughput. > > > > If you're thinking about rolling your own hardware, you should really be > using CC1100 or CC2500 radios for any wireless application that doesn't > require 802.15.4 compatibility: > http://docs.tinyos.net/index.php/CC1100/CC2500 > > > > -David > > > > > > > > > > > > ------------------------------------------------------------------------ > > *From:* [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] *On Behalf Of > *Edgar Charry > *Sent:* Monday, April 14, 2008 3:57 PM > *To:* [EMAIL PROTECTED]; Eric Keller > *Cc:* tinyos-help@millennium.berkeley.edu > *Subject:* Re: [Tinyos-help] Pumping up bandwidth - Mica2Dot/Mica2 > > > > Hi all, > > Thanks for your prompt replies. Unfortunately I that link didn't let me > through. > > In fact I am still trying to undestand them, as I wasn't aware of that > limitation of 33-50ms of the Mica2's! You are saying that the maximum > bandwidth my app should require is 0-25Hz so that I have a nice > reconstruction of my wave, due to HW limitations? > I knew that the CC1000 has a maximum bandwidth of 76.8kbps and of course > due to EEPROM readings/writings, CPU instructions, ADC's > measurements etc. this number should decrease. But I wasn't expecting a > final bandwidth of 30pckts/s!!! In fact, I thought there were problems > related to the TOSBase. > My app requirement need at least 100Hz (Mica2's transmission needed thus > 200 pckts/s), which is necessary to track a complete gait cycle using > acc and gyros with good definition. > > What is the most critical factor in the Mica2's that blow the > transmission rate so bad? Does this happen with the Mica2Dot too? Data > compression (sample with a higher freq, store in the RAM and then send > the whole bunch of bytes) has a limitation of 29 bytes due to TinyOS, > correct? > > Thanks guys for the good info. > Cheers, > Edgar Charry > >> Date: Mon, 14 Apr 2008 12:20:38 -0600 >> From: [EMAIL PROTECTED] >> To: [EMAIL PROTECTED] >> CC: tinyos-help@millennium.berkeley.edu >> Subject: Re: [Tinyos-help] Pumping up bandwidth - Mica2Dot/Mica2 >> >> Well, since people are quoting my second source messages, have a look at: >> http://www.etantdonnes.com/Motes/report_mica2/ >> (which seems to be down right now but will hopefully be back soon...). >> >> However my message speed/reliability measurements use only the standard >> GenericComm and TOS1 code. I think the OP was trying to fiddle timeouts >> and backoffs to speed things up further. Data mining of the help list >> should turn up some more useful advice in this respect. >> >> MS >> >> Eric Keller wrote: >> > There is a limit to how many packets you can send with a mica2 which > you are >> > at or above. You probably want to lower your bandwidth requirements > somehow. >> > See this message: >> > > https://www.millennium.berkeley.edu/pipermail/tinyos-help/2008-April/032464. html >> > >> > Eric >> > >> > >> > On Mon, Apr 14, 2008 at 4:59 AM, Edgar Charry <[EMAIL PROTECTED]> > wrote: >> >> Hi all, >> >> >> >> I am trying to pump my packet transmission up between a Mica2Dot and a >> >> Mica2 to at least 200Hz [pckts/s]. >> >> >> >> I've decreased the timer constant to a bottleneck of 33ms (30 > pckts/s) that >> >> pratically executes a round of ADC measurements and send the packet. >> >> Decreasing from this point doesn't give me more bandwidth. However, my >> >> packet is 14bytes long (the TinyOS header + just a couple of adc >> >> measurements + CRC). >> >> >> >> I suspect that this 33ms (parsed time stamps from XSniffer) are > limited to >> >> the TOSBase.nc on the Mica2. I suspect that the PLL of the Mica2 is >> >> listening through channels and is not locked to the transmitter's > one. Every >> >> loop thus should take 33ms. >> >> >> >> Actually, I haven't been through the CC1000 conf/mod components > though, but >> >> I reckon with your experience this can be solved easily. >> >> Cheers, >> >> Edgar Charry >> >> >> >> ________________________________ >> >> Explore the seven wonders of the world Learn more! >> >> _______________________________________________ >> >> Tinyos-help mailing list >> >> Tinyos-help@millennium.berkeley.edu >> >> > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >> >> >> > _______________________________________________ >> > Tinyos-help mailing list >> > Tinyos-help@millennium.berkeley.edu >> > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >> >> -- >> Platform: WinXP/Cygwin >> TinyOS version: 1.x, Boomerang >> Programmer: MIB510 >> Device(s): Mica2, MicaZ, Tmote >> Sensor board: homebrew >> >> _______________________________________________ >> Tinyos-help mailing list >> Tinyos-help@millennium.berkeley.edu >> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > ------------------------------------------------------------------------ > > Explore the seven wonders of the world Learn more! > <http://search.msn.com/results.aspx?q=7+wonders+world&mkt=en-US&form=QBRE> > -- Platform: WinXP/Cygwin TinyOS version: 1.x, Boomerang Programmer: MIB510 Device(s): Mica2, MicaZ, Tmote Sensor board: homebrew _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
