DSSS or not?
Submitted by baskin on Wed, 01/23/2008 - 10:47.
I don't know if this is a valid question but i want to ask (if it is possible) how can we distinguish a DSSS (Direct-Sequence Spread Spectrum) transmission from an non DSSS one?
Can we see difference on the Chanalyzer graphs?
Baskin, I spoke with my superior, the one and only ChiefGeek. Any device that takes a general shape on chanalyzer's topographic view will be DSSS. The only real way to determine if it is non dsss is if it frequency hops. I will be providing a link to a frequency hopping device here, but also check out our Device Signatures Page
I am not fully educated on DSSS, however based on the wikipedia article I skimmed, it seems like the signal makes a specific shape, and the receiver mimicks it?
I think this would be a good example, the receiver signal is the same shape above the 802.11g broadcast. I think most of the shapes you will see in our screenshots will be DSSS, however I will talk to one of my superiors and see if they can shed some light on it. Because I believe most wifi, cordless phones, and zigbee devices are dsss....
And then maybe something like a microwave or a jammer would not be dsss.
I don't think you would be able to tell. All a spectrum analyzer will show is frequency usage. You would need some way to extract the data on the frequency to tell what type of encoding it is using. Both allocate a range of frequencies for use in a band. I too could be mistaken on that, but the only way to know would to compare a G-only and B-only Transmission.
The shape that appears on the spectrum analyzer is related to frequency usage. I have yet to get a WiSpy though I plan on getting a 2.4x as soon as I can. I have used HP's in other bands.
PS Trent: 802.11g is ODFM - not DSSS. Just like 802.11a in the 5.8ghz band.