I read the 802.15.4 standard and something is really confusing me: How is spreading achieved in 802.15.4? is it by multiplying, encoding or modulating each data symbol (4 bits) with a certain code like in conventional DSSS or just by replacing the symbol by that code without any multiplication, encoding or modulation (which wouldn't make sense to me) ? I would think the former one but I have to say I am not sure.I guess the word "mapping" is confusing me
Asked
Viewed
27 times
1
$\begingroup$
$\endgroup$
-
$\begingroup$ Do you have a link to or citation from the standard that can illustrate exactly what you're asking about? $\endgroup$ – Jason R Aug 2 '18 at 23:31
-
$\begingroup$ Here it is : 10.2 Modulation and spreading The O-QPSK PHY employs a 16-ary quasi-orthogonal modulation technique. During each data symbol period, four information bits are used to select 1 of 16 nearly orthogonal pseudo-random noise (PN) sequences to be transmitted. The PN sequences for successive data symbols are concatenated, and the aggregate chip sequence is modulated onto the carrier using offset quadrature phase-shift keying (O-QPSK). also: 10.2.4 Symbol-to-chip mapping In the 2450 MHz band, each data symbol shall be mapped into a 32-chip PN sequence as specified in Table 73 $\endgroup$ – Hatem Tawfik Aug 3 '18 at 0:47
-
$\begingroup$ It sounds like you answered your question? (It is like conventional DSSS as you asked) $\endgroup$ – Dan Boschen Aug 3 '18 at 22:22
-
$\begingroup$ @Dan Boschen. Thank you very much for confirming what I thought was the right answer. Not that I want to bother you in the future with more questions, but just in case I do have a question may I connect with you on Linkedin? $\endgroup$ – Hatem Tawfik Aug 4 '18 at 0:02
-
$\begingroup$ Hi Hatem- Go ahead and post your questions here so that you get the best answers. $\endgroup$ – Dan Boschen Aug 4 '18 at 4:06
