Page 1259 - 5G Basics - Core Network Aspects

Transport aspects 2

0 –

P server

 P ? Enable
Client server
data
indication Memory Payload area
= Frame start
read/write Clock
enable
C (t) G.709-Y.1331(12)_FD.4
n

Figure D.4 – Sigma-delta accumulator

As the same start value and Cn(t) are used at the mapper and de-mapper the same results are obtained and
interworking is achieved.

D.2 Applying GMP in OTN
Clauses 17.7, 19.6 and 20.5 specify GMP as the asynchronous generic mapping method for the mapping of
CBR client signals into OPUk, the mapping of ODUk signals into a server OPUk (via the ODTUk.ts) and the
mapping of ODUk signals into an OPUCn (via ODTUCn.ts).

NOTE – GMP complements the traditional asynchronous client/server specific mapping method specified in clauses
17.6 and 19.5. GMP is intended to provide the justification of new CBR type client signals into OPUk.
Asynchronous mappings in the OTN have a default 8-bit timing granularity. Such 8-bit timing granularity is
supported in GMP by means of a cn with n=8 (c8). The jitter/wander requirements for some of the OTN
client signals are such that for those signals an 8-bit timing granularity may not be sufficient. For such a
case, a 1-bit timing granularity is supported in GMP by means of cn with n=1 (c1).

M-byte granularity mapping
Clauses 17.7 and 19.6 specify that the mapping of CBR client bits into the payload of an OPUk and the
mapping of ODUj bits into the payload of an ODTUk.ts is performed with 8  M-bit (M-byte) granularity.

The insertion of CBR client data into the payload area of the OPUk frame and the insertion of ODUj data
into the payload area of the ODTUk.ts multiframe at the mapper is performed in M-byte (or m-bit,
m = 8  M) data entities, denoted as Cm(t). The remaining CnD(t) data entities are signalled in the
justification overhead as additional timing/phase information.







c m   cn n     f client  B server      f client  B server    f client  B server 8 /    (D-12)



 m   f server m   f server 8 M   f server M 
As only an integer number of m-bit data entities can be transported per server frame or multiframe, the
integer value Cm(t) of cm has to be used. Since it is required that no information is lost, the rounding process
to the integer value has to take care of the truncated part, e.g., a cm with a value of 10.25 has to be
represented by the integer sequence 10,10,10,11.
 f client B server  8 /

C m t) (  int( c )  int     (D-13)
m
f
 server M 

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