Page 697 - 5G Basics - Core Network Aspects

Transport aspects 2

NOTE – The upper layer application entities in Figure 5-11 correspond to L2+ function in Figure 5-2 (for FTU-O) and
Figure 5-3 (for FTU-R). Similarly, the upper layer management and control entity in Figure 5-11 corresponds to the ME,
DRA, TCE and VCE functions in Figure 5-2 for the FTU-O and PSE, TCE, and DRR functions in Figure 5-3 and FTU-R.

The PMD and PMS-TC functions are defined in the main body of this Recommendation. The packet-based
TPS-TC (PTM-TC) function is defined in clause 8.3. Other types of TPS-TC are for further study. Functions
above the γ reference point are beyond the scope of this Recommendation, except the NTR and ToD
functions of the TCE, which are defined in clauses 8.4 and 8.5, respectively.

Figure 5-11 – FTU functional model

The principal functions of the PMD are symbol generation and recovery, constellation mapping and
decoding, modulation and demodulation, and FEXT cancellation (at the FTU-O). The PMD may also include
line equalization. The symbol timing of the FTU-R is synchronized to the central clock of the DPU. All the
aforementioned PMD functions are supported by the corresponding management/control primitives
exchanged via the PMD_MGMT reference point (see clause 10.1.2). The PMD function of the FTU-O also
provides the precoding necessary to support vectoring. The ε and η reference points (at the FTU-O) define,
respectively, transmit and receive interfaces with PMD functions of other lines in the vectored group
(see clause 10.3).

The main functions of the PMS-TC sub-layer are forward error correction (FEC) encoding and decoding,
framing and frame synchronization, retransmission, error detection, interleaving and de-interleaving, and
scrambling and descrambling. The PMS-TC is connected to the PMD by the δ reference point, and is
connected to the TPS-TC by the α-reference point. PMS-TC functions are supported by the corresponding
management/control primitives exchanged via the PMS-TC_MGMT reference point (see clause 9.1.2). The
PMS-TC also establishes the robust management channel (RMC).

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