Page 1037 - 5G Basics - Core Network Aspects

Transport aspects 2

DTA update where:
Time M ds ( +1) > n M ds ( )n DS ACK
window shift
DS ACK window n DS ACK window +1n
DS
. .. US . . .

( +1) > n ( )n
a) DS ACK window size increases in case of a DTA update where M ds M ds

DTA update where:
Time M ds ( +1) < n M ds ( )n DS ACK
window shift
DS ACK window n DS ACK window +1n
DS
. .. US . . .

b) DS ACK window size decreases in case of a DTA update where M ( +1) < n M ( )n
ds ds

DTA update where:
Time M ds ( +1) < n M ds ( )n
US ACK
window shift
DS
. . . US . . .

US ACK window n US ACK window +1n

c) US ACK window is not affected due to DTA updates G.9701(14)-Amd.3(17)_FX.3

Figure X.3 – Examples to illustrate the impact of a DTA update on the ACK window size

X.6.4.1 Performance during transitions
After a DTA procedure, for a period no longer than the configured maximum delay (delay_max), the
ErrorFreeThroughput (EFTR), and INP may be worse than the EFTR and INP expected with the new TDD
frame parameters.
NOTE – Jitter on the packets may also increase for the same period of time.
X.6.5 Superframe structure for DTA

The superframe structure shall be as specified in clause 10.6 except that TDD frames within the
superframes during which DTA updates are applied may have different values of Mds.

X.6.6 Timing and synchronization for DTA
The 'DTA update' RMC command contains the Mds that determines the new TDD frame configuration, and a
4-bit DTA frame down count (DTAFDC) that indicates when the new Mds value shall take effect. The
minimum initial value of DTAFDC shall be greater than or equal to 2 and is a capability of the FTU-R,
indicated during initialization with the R-MSG 2 message (see parameter 'min initial DTAFDC' in Table X.18).
The FTU-O shall use an initial value of DTAFDC that is between this 'min initial DTAFDC' and 15, inclusive.

The first 'DTA update' RMC command initiating a new DTA update contains a DTAFDC value in the range of
valid initial values indicated by the FTU-R during initialization. Following this command, the FTU-O shall
repeat the 'DTA update' RMC command with the new requested Mds value for the subsequent logical
frames, while decrementing DTAFDC in each logical frame by 1 until DTAFDC reaches the value of zero,
which indicates the activation of the new TDD frame configuration. The new Mds setting shall be applied
starting from the TDD frame that contains the 'DTA update' RMC command with DTAFDC = 0
(see Figure X.2). For the reason of robustness, the FTU-O shall continue to send the 'DTA update' RMC
command with the updated Mds value and DTAFDC=0 at least until it has received an upstream transmission

1027