Page 610 - 5G Basics - Core Network Aspects

2 Transport aspects

8.1 Reference points

Figure 8-1 shows a set of reference points that are defined in this Supplement.

iRoF-BB iRoF-IF or -RF S/R R/S iRoF-BB or -IF iRoF-RF

ONU FCP RF BEP/FEP

BB M/dMP FCP OLT
ODN

BB M/dMP FCP OLT
ONU FCP RF BEP/FEP

Down and Up SNI UNI Down- and Up-
baseband data RF signals
(backhaul) G Suppl.55(15)_F8-1
iRoF-BB Radio over fibre baseband interface
iRoF-IF Radio over fibre intermediate frequency band interface
iRoF-RF Radio over fibre radio frequency band interface

Figure 8-1 – Reference configuration for a RoF over ODN

The ODN offers one or more optical paths between one or more optical line terminals (OLTs) and one or
more optical network units (ONUs). Each optical path is defined between reference points S and R in a
specific wavelength window.
This system consists of OLT, ONU and fibre cable, which has an ODN configuration with passive optical
devices (e.g., optical power splitter, optical wavelength MUX/DEMUX).
The RoF signal transmission in downstream and upstream directions can take place on an ODN with same
fibre and components (duplex/diplex working) or on separate fibres and components (simplex working).
We have to consider ODN architecture including the following.

One local (e.g., central office) hosting several baseband stations to one antenna site hosting several remote
antennas with optional protection scheme.
One local (e.g., central office) hosting several baseband stations to several antenna sites hosting several
remote antennas with optional protection scheme.
Multiple access techniques should be considered to achieve a limited number of fibres in the ODN and
optical interfaces. The multiplexing technologies are as follows.
Time division multiple access should be used for digital (preferred) and analogue (potential) RoF signals.

For digital RoF, we have to consider two levels of time multiplexing, as follows.
The first concerns the capability to time multiplex several digital RoF signals in the electrical domain and
transmit the result as one wavelength channel. In other words, the time multiplexing here means the
capability to aggregate different links with smaller data rate into one link with much higher data rate. Then,
the high data rate link could be mapped to one wavelength channel pair. One example of this capability is
the aggregation of four 2.5 Gbps CPRI links into one 10 Gbps CPRI link.
The second concerns the capability to address several ONUs (several RF BEP/FEPs) connected to the same
ODN and a single OLT port connected to several baseband modulation and demodulation (BB M/dMP)
processors. Time division multiple access is used to achieve a transmission technique involving the
multiplexing of many digital RoF inside time slots onto the same time payload.

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