Hi all, there always said long PN sequence(period 2^n-1) got a small cross-correlation property as -1/(2^n-1). But in practice, one symbol could only be spread by a small amount(128 etc) but not 2^n-1, so how can we guarantee the cross correlation property -1/(2^n-1)? Thanks. B. R. Laron
long PN sequence' usage in CDMA
Started by ●September 9, 2009
Reply by ●September 12, 20092009-09-12
On Tue, 08 Sep 2009 22:37:01 -0500, Laron wrote:> Hi all, > there always said long PN sequence(period 2^n-1) got a small > cross-correlation property as -1/(2^n-1). But in practice, one symbol > could only be spread by a small amount(128 etc) but not 2^n-1, so how > can we guarantee the cross correlation property -1/(2^n-1)? Thanks.You can't. The level of noise from other transmitter's PN-modulated traffic can be high, which is why there are layers of synchronous demodulation and error correction after the first despreading. -- http://www.wescottdesign.com