By Dr. Ernest Simo
20.0 What process takes place at the Mobile Receiver upon receiving an input with a Short PN Code?
Let us examine the simplified processes at each receiver (each Mobile). The received or input to Mobile A is:
A) + dj(t)•PN(t- B)Mobile A is assumed to have synchronized with cell A. So, it is tuned to cell A with its local short PN code set to PN(t-
A).Incoming input signal Mobile A will then “multiply” its local code PN(t-
A), with the received or. The resulting output signal is:A)• PN(t- A) + dj(t)•PN(t- B)• PN(t- A) As noted earlier, the normalized Auto-correlation PN(t-
A)• PN(t- A) is 1. And the normalized Cross-correlation PN(t- B)• PN(t- A) is -1/L. For large values of L therefore, the second term can be ignored. This simply reduces the output to di(t). (Note that the signal from cell B is nicely ignored !)
© 2001 DR. ERNEST SIMO - SPACE2000