Page 621 - 5G Basics - Core Network Aspects

Transport aspects 2

9.2.3.2 IF-band SCM RoF system with a digital aggregation technique

Figure 9-11 shows an aggregated analogue RoF system with the 36 LTE channels, consisting of six
bandwidth groups each having six channels for 2  2 MIMO and three sectors, aggregated in a single optical
wavelength. This is a kind of IF-band SCM RoF system with a digital aggregation technique.

6×1.4 MHz 6×5 MHz 6×15 MHz 6×20 MHz
0
Relative power (dB)
Core –10 Antenna Antenna
–20
network –30 6×3 MHz 6×10 MHz Antenna
–40
0 0.1 0.2 0.3 0.4 0.5 0.6
Frequency (GHz)
Backhaul Centralized BBU pool WDM WDM RRU RRU RRU
BBU
baseband Aggregation/ DAC TX … … RX ADC De-Aggregation/
processing De-aggregation ADC RX Optical TX DAC Aggregation
… fib re link
G Suppl.55(15)_F9-11

Figure 9-11 – Aggregated analogue RoF system with the 36 LTE channels,
aggregated in a single optical wavelength

Figure 9-12-a shows the typical experimental set-up and Figure 9-12-b shows the 64-QAM signal
constellations recovered after 20 km transmission over a standard single-mode fibre (SSMF) with −10 dBm
received optical power for the six bandwidth groups, corresponding to the LTE bandwidths of 1.4, 3, 5, 10,
15 and 20 MHz. Evidently, the recovered signal constellations show high SNR.

(a) IM/DD experimental setup

Aggregation De-aggregation
DSP DAC AMP DML 20-km SSMF VOA APD AMP ADC DSP

(b) Measured constellations of the 36 E-UTRA channels arranged according to the channel bandwidth

G Suppl.55(15)_F9-12

Figure 9-12 – Typical experimental set-up and measurement results.
IM/DD: intensity modulation with direct detection

Figure 9-13 shows the measured EVMs of all the 36 LTE channels after transmission through the aggregated
analogue RoF system. To achieve an EVM of less than 8% EVM, as required for 64-QAM (see [b-3GPP TS
36.104]), the received optical power needs to be larger than −24 dBm, which corresponds to a link loss
budget of 26 dB assuming a typical optical signal power of 2 dBm. This link loss budget can be readily
achieved in WDM PONs, indicating the validity of the proposed bandwidth-efficient MFH approach based
on aggregated analogue RoF. With the assumption of 8 dBm signal power at the transmitter, the link loss
budget can be increased to 32 dB. We expect that with additional performance improvement techniques,
the link loss budget may be further increased.

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