Page 1176 - 5G Basics - Core Network Aspects

2 Transport aspects

The OPUk overhead for this mapping consists of a:

– payload structure identifier (PSI) including the payload type (PT) as specified in Table 15-9, the
client signal fail (CSF) and 254 bytes plus 7 bits reserved for future international standardization
(RES);
– three justification control (JC1, JC2, JC3) bytes carrying the value of GMP overhead Cm;
– three justification control (JC4, JC5, JC6) bytes carrying the value of GMP overhead CnD and

– one byte reserved for future international standardization (RES).
The JC1, JC2 and JC3 bytes consist of a 14-bit Cm field (bits C1, C2, .., C14), a 1-bit Increment Indicator (II)
field, a 1-bit Decrement Indicator (DI) field and an 8-bit CRC-8 field which contains an error check code over
the JC1, JC2 and JC3 fields.

The JC4, JC5 and JC6 bytes consist of a 10-bit CnD field (bits D1, D2, .., D10), a 5-bit CRC-5 field which
contains an error check code over the bits 4 to 8 in the JC4, JC5 and JC6 fields and nine bits reserved for
future international standardization (RES). The default value of n in CnD is 8. The support for n=1 is client
dependent and specified in the clauses hereafter when required.
The values of m, Cm,min, Cm,max, n, Cn,min and Cn,max for CBR client into OPUk are as follows:

m  , 8 16 , 64 , 256 , 640
(17-1)
 CBR _ nom_ client _ bit _ rate  Number _ of _ GMP_ blocks _ in _ OPUk 
c m, nom    (17-2)


 OPUk _ nom _ bit _ rate 
 CBR _1 client _ bit _ rate _ tolerance 
c m min,  c m, nom      (17-3)
 1 OPUk _ bit _ rate _ tolerance 
 CBR _1 client _ bit _ rate _ tolerance 
c m max,  c m, nom     (17-4)

 1 OPUk _ bit _ rate _ tolerance 
C  floor c  (17-5)
m , min m , min
C  ceiling c  (17-6)
m , max m , min
n  1 , 8
(17-7)

 CBR _ client _ nom _ bit _ rate  Number _ of _ GMP_ blocks _ in _ OPUk 
c n, nom     (17-8)

 OPUk _ nom _ bit _ rate 
 CBR _1 client _ bit _ rate _ tolerance 
c n min,  c n, nom     (17-9)

 1 OPUk _ bit _ rate _ tolerance 
 CBR _1 client _ bit _ rate _ tolerance 
c n max,  c n, nom     (17-10)

 1 OPUk _ bit _ rate _ tolerance 
C  floor c  (17-11)
, n min , n min
C  ceiling c  (17-12)
, n max , n min
Cm,min, Cn,min, Cm,max and Cn,max values represent the boundaries of client/OPU ppm offset combinations
(i.e., min. client/max. OPU and max. client/min. OPU). In steady state, given instances of client/OPU offset
combinations should not result in generated Cm and Cn values throughout this range but rather should be
within as small a range as possible.

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