Page 1264 - 5G Basics - Core Network Aspects

2 Transport aspects

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8
2
The CRC-8 located in JC3 is calculated over the JC1 and JC2 bits. The CRC-8 uses the g(x) = x + x + x + 1
generator polynomial, and is calculated as follows:
1) The JC1 and JC2 octets are taken in network octet order, most significant bit first, to form a 16-bit
pattern representing the coefficients of a polynomial M(x) of degree 15.
2) M(x) is multiplied by x and divided (modulo 2) by G(x), producing a remainder R(x) of degree 7 or
8
less.
7
3) The coefficients of R(x) are considered to be an 8-bit sequence, where x is the most significant bit.
4) This 8-bit sequence is the CRC-8 where the first bit of the CRC-8 to be transmitted is the coefficient
7
0
of x and the last bit transmitted is the coefficient of x .
The de-mapper process performs steps 1-3 in the same manner as the mapper process, except that here,
the M(x) polynomial of step 1 includes the CRC bits of JC3, resulting in M(x) having degree 23. In the
absence of bit errors, the remainder shall be 0000 0000.

Table D.3 – 10-bit Cm(t) increment and decrement indicator patterns

C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 II DI Change
U U U U U U U U U U 0 0 0
I U I U I U I U I U 1 0 +1
I U U I U I I U U I 0 1 –1
U I U I I U U I U I 1 0 +2
U I I U U I U I I U 0 1 –2
binary value 1 1 More than
+2/–2
NOTE
– I indicates inverted Ci bit
– U indicates unchanged Ci bit
The CRC-6 located in JC3 is calculated over bits 3-8 of JC1 and JC2 (i.e., the bits containing the GMP
3
2
6
overhead value shown in Table D.3). The CRC-6 uses the g(x) = x + x + x + 1 generator polynomial, and is
calculated as follows:
1) The JC1 and JC2 octets are taken in network octet order, most significant bit first, such that bit 3 of
JC1 through bit 8 of JC2 form a 12-bit pattern representing the coefficients of a polynomial M(x) of
degree 11.
6
2) M(x) is multiplied by x and divided (modulo 2) by G(x), producing a remainder R(x) of degree 5 or
less.
5
3) The coefficients of R(x) are considered to be a 6-bit sequence, where x is the most significant bit.
4) This 6-bit sequence is the CRC-6 where the first bit of the CRC-6 to be transmitted is the coefficient
5
0
of x and the last bit transmitted is the coefficient of x .
The de-mapper process performs steps 1-3 in the same manner as the mapper process, except that here,
the M(x) polynomial of step 1 includes the CRC bits of JC3, resulting in M(x) having degree 17. In the
absence of bit errors, the remainder shall be 000000.

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