Page 691 - 5G Basics - Core Network Aspects

Transport aspects 2

Figure 5-5 – Application reference model for FTTdp with reverse powering and POTS

Table 5-2 – Signal flows applicable at the reference points shown in Figure 5-5

Reference ITU-T G.9701 Reverse power feeding Analogue voice signals Out of band POTS
point signals (RPF) signalling
U-O2 Yes No No No
U-O2O No No Yes Yes
U-O2P No Yes No No

U-O/U-R Yes Yes Yes Yes
U-R2P No Yes No No
U-R2S No Yes (Note) Yes Yes
U-R2 Yes No No No
NOTE – RPF provides power for FXS POTS adapters implementing signalling conversion.
The power is inserted on the wire-pair by the power source equipment (PSE) located in the customer
premises and extracted from the wire-pair by the power extractor (PE) located in the DPU. Power is
extracted from each active port and combined in the power supply unit (PSU). The PSE and the NT may be
integrated into the same physical box.

Because of reverse power feeding direct current (DC) from the customer premises, the underlying POTS
service can only share the same wire-pair with the data service if POTS adapters are applied. POTS adapters
provide alternative signalling means on the U reference point, equivalent to POTS signalling. At the network
side, a FXO-type POTS adapter converts the foreign exchange office (FXO) interface POTS DC signalling from
the narrowband network into the alternative signalling on the U reference point. At the customer premises
side, a FXS-type POTS adapter converts the alternative signalling on the U reference point into foreign
exchange subscriber interface (FXS) POTS DC signalling towards the telephones.
As an alternative to the POTS provided from the exchange-side narrowband network, a derived POTS
service may be provided. The derived POTS uses voice-over-IP (VoIP) technology on the U reference point,
with the VoIP terminated in an analogue telephone adapter (ATA). The ATA is connected to the home
network (e.g., [b-ITU-T G.9960] and [b-ITU-T G.9961]) or is integrated with the NT1 or NT2 in the same
physical box, with the FXO-type POTS adapter located in the customer premises. The application of reverse
powering and derived POTS is depicted in Figure 5-6.

681