# What is the meaning of BPSK(n)

I am doing some research into GNSS (Global Navigation Satellite Systems) and have come across various signals listed as having the in-phase or quadrature channels modulated with BPSK(2) or BPSK(10), etc. However, I am struggling to find a definition of BPSK that includes this additional parameter.

What does the (n) signify in BPSK(n)?

I understand the basic concept of BPSK - Binary Phase Shift Keying and have implemented this in very basic tests by multiplying the LO by 1 or -1 for a 1 or 0 chip respectively.

It has been suggested by a colleague that the n is simply the chip rate and that BPSK(1) is a chip rate of 1MHz, BPSK(2) 2MHz, BPSK(10) 10MHz, etc. as mentioned in the comments by Jim Clay.

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I am very familiar with BPSK, and I have never seen BPSK(n), BPSK(2), or BPSK(10). Could you provide a quote that gives the context? –  Jim Clay Feb 6 '13 at 19:37
As a couple of examples, see the characteristics table in en.wikipedia.org/wiki/… where various signals are described as BPSK(1) [GPS L1 C/A which is what I understood as BPSK], BPSK(2) or BPSK(10); or Figure 2 in www2.ulg.ac.be/ipne/garnir/time/galileo/gal_stf_final_paper.pdf –  Darran Feb 6 '13 at 19:44
Both of those signals are CDMA. A quick review didn't indicate explicitly what the numbers mean, but it appears to me that they probably indicate the chip rate that is used. I saw a reference in a Galileo paper that seemed to suggest that BPSK(5) meant a BPSK signal at 5*fo chip rate. –  Jim Clay Feb 6 '13 at 19:58
Yuck, more tower of babel terminology rampant in the literature. >< –  Mohammad Feb 6 '13 at 20:18
Sorry, but I find it a bit ironic to start a question about unexplained acronym, BPSK(n), with an unexplained acronym, GNSS. –  Hilmar Feb 7 '13 at 5:34

It appears that the "(n)" notation means that the signal has a chip rate of $n*f_o$, and in the case of the Compass signals $f_o$ is 1.023 Mchips/s.