IRN-200D-001
IS-GPS-200D
7 Mar 2006
6
3.2.1.1 P-Code
. The PRN P-code for SV ID number i is a ranging code, P
i
(t), of 7 days in length at a chipping
rate of 10.23 Mbps. The 7 day sequence is the modulo-2 sum of two sub-sequences referred to as X1 and X2
i
; their
lengths are 15,345,000 chips and 15,345,037 chips, respectively. The X2
i
sequence is an X2 sequence selectively
delayed by 1 to 37 chips thereby allowing the basic code generation technique to produce a set of 37 mutually
exclusive P-code sequences of 7 days in length. Of these, 32 are designated for use by SVs and 5 are reserved for
other purposes (e.g. ground transmitters, etc.). Assignment of these code phase segments by SV-ID number (or
other use) is given in Table 3-I. Additional PRN P-code sequences with assigned PRN numbers are provided in
Section 6.3.5.2, Table 6-I
3.2.1.2 Y-Code
. The PRN Y-code is used in place of the P-code when the A-S mode of operation is activated.
3.2.1.3 C/A-Code
. The PRN C/A-Code for SV ID number i is a Gold code, G
i
(t), of 1 millisecond in length at a
chipping rate of 1023 Kbps. The G
i
(t) sequence is a linear pattern generated by the modulo-2 addition of two sub-
sequences, G1 and G2
i
, each of which is a 1023 chip long linear pattern. The epochs of the Gold code are
synchronized with the X1 epochs of the P-code. As shown in Table 3-I, the G2
i
sequence is a G2 sequence
selectively delayed by pre-assigned number of chips, thereby generating a set of different C/A-codes. Assignment
of these by GPS PRN signal number is given in Table 3-I. Additional PRN C/A-code sequences with assigned PRN
numbers are provided in Section 6.3.5.1, Table 6-I
3.2.1.4 L2 CM-Code (IIR-M, IIF, and subsequent blocks)
. The PRN L2 CM-code for SV ID number i is a ranging
code, C
M,i
(t), which is 20 milliseconds in length at a chipping rate of 511.5 Kbps. The epochs of the L2 CM-code
are synchronized with the X1 epochs of the P-code. The C
M,i
(t) sequence is a linear pattern which is short cycled
every count of 10230 chips by resetting with a specified initial state. Assignment of initial states by GPS PRN
signal number is given in Table 3-II. Additional PRN L2 CM-code sequence pairs are provided in Section 6.3.5.3,
Table 6-II
3.2.1.5 L2 CL-Code (IIR-M, IIF, and subsequent blocks)
. The PRN L2 CL-code for SV ID number i is a ranging
code, C
L,i
(t), which is 1.5 seconds in length at a chipping rate of 511.5 Kbps. The epochs of the L2 CL-code are
synchronized with the X1 epochs of the P-code. The C
L,i
(t) sequence is a linear pattern which is generated using the
same code generator polynomial as the one used for C
M,i
(t). However, the C
L,i
(t) sequence is short cycled by
resetting with a specified initial state every code count of 767250 chips. Assignment of initial states by GPS PRN
signal number is given in Table 3-II. Additional PRN L2 CL-code sequence pairs are provided in Section 6.3.5.3,
Table 6-II