Page 82 - Kaleidoscope Academic Conference Proceedings 2024

2024 ITU Kaleidoscope Academic Conference

CS RRH RN
Data Power 92, 108 Power
GHz
λ 20-km fiber 92-108 GHz
Optical modulator 100 GHz f 4 m
Two-tone
opt. gen. 1 High-speed
Optical coupler Photodetector-1
A optical modulator
B
Rx 80 GHz AP
80
92 GHz GHz
Power
2 m
Rx. signal 92 GHz f
C
Photodetector-2 108 GHz
Two-tone
Power
opt. gen. 2
Rx AP λ
28 GHz Power 28 GHz 80
GHz
Power
2 m 28 GHz f
28 GHz f D
Rx. signal Photodetector-2 OBPF
Rx OC
Fig. 10. Performance of 28- and 92-GHz signals.
108 GHz 92 GHz 28 GHz
A B C D
92 GHz
92 GHz
108 GHz
Fig. 8. System diagram for simultaneous generation, transmission, and reception of 28- and 92-GHz signal.
CS: central station; RRH: remote radio head; RN: relay node; AP: access point; Rx: receiver.
Gb/s signals using 32-QAM and 16-QAM modulation. and backhaul connectivity, which can enhance signal
Satisfactory performance was confirmed for the 16-QAM performance and spectrum usage and reduce equipment costs.
signal, achieving a transmission line rate of 48 Gb/s. For the In both cases, the multiplexing and demultiplexing of radio
32-QAM signal, a 40-Gb/s signal was successfully signals from/to different frequency bands play vital role.
transmitted with EVMs satisfying the 20% FEC limit. The Electrical multiplexers and demultiplexers can be developed
performance of the 50-Gb/s 32-QAM signal was slightly and employed for signal multiplexing and demultiplexing.
above the required threshold, which could be attributed to the However, their efficiency and frequency are limited by the
low SNRs in some subcarriers. Similar to the bridge system, roll-off factor and bandwidth limitations of electrical devices.
this problem can be solved by optimizing the system and In this subsection, we propose a novel system using photonic
applying a robust DSP. The system is flexible and can be technology for the efficient multiplexing and demultiplexing
applied to the generation, transmission, and relay of radio of radio signals. The proposed system was applied to the
signals in higher-frequency bands. To date, the transmitted simultaneous generation, transmission, reception, and
data rates are the highest over a relay system, confirming the distribution of 28- and 92-GHz radio signals over a single
potential of the proposed system for high-speed radio fiber–wireless system in the 100-GHz band.
communications in 6G networks.
A diagram of this system is shown in Fig. 8. A two-tone
5. MULTI-RAN AND IAB SYSTEM optical signal with a frequency separation of 80 GHz was
generated at the CS. The two sidebands were separated, and
In 5G-Advanced and 6G networks, the coexistence of the upper sideband was used for data modulation. In the
multiple RANs in different frequency bands is important for experiment, 5G NR signals at 12 GHz and 28 GHz were
supporting different use cases. RANs in the low mmWave generated and combined using an electrical combiner. The
band can be deployed for wide coverage and popular uses, combined signal was fed to an intensity optical modulator for
whereas high-frequency RANs are useful for high-speed and conversion into an optical signal. The upper sideband of the
low-latency services. However, the deployment of multi- modulated signal was selected and combined with the lower
RANs poses significant challenges to transport networks. sideband of the two-tone optical signal. The frequency
The simultaneous generation and transmission of multi-RAN differences between the unmodulated and modulated
signals over common transport systems is crucial for sidebands were 92 GHz (= 80 + 12 GHz) and 108 GHz (= 80
reducing the cost and complexity. In this case, the signals + 28 GHz) as shown in inset A of Fig. 8. Notably, 5G NR
must be multiplexed and demultiplexed before and after the signals can also be converted into the optical domain using
transmission. These technologies are also important for different optical modulators. The combined signal was
facilitating IAB technology. In IAB applications, wireless transmitted to an RRH using a 20-km SMF. At the RRH, the
backhauling uses the same wireless spectrum for coverage signal was input into a high-speed PD for simultaneous

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