PN Sequences - Part 2
How PN Codes are used in IS-95 CDMA Systems
By Dr. Ernest Simo
1.0 Using the Short PN Code
How the Short PN Code is Used
Let us assign the Short PN Offsets PN(t- t A) and
PN(t- t B) to cell A and cell B respectively.
The signal from cell A to Mobile A is of the form di(t)•
PN(t- t A). Likewise the signal from cell
B to Mobile B is of the form dj(t)•
PN(t- t B).
The received signal at Mobile A is the composite signal from cell A and cell B.
(Both cells are on the same 1.25 MHz Frequency band.). Likewise, the received
signal at Mobile B is the same composite signal from cell A and cell B. The
composite signal received by each Mobile can be represented as:
Rx = di(t)•
PN(t- t A) + dj(t)•
PN(t- t B)
Here, we have ignored the propagation delay which can be readily resolved by the
synchronization process at the Mobiles.
