Page 83 - Kaleidoscope Academic Conference Proceedings 2024

Innovation and Digital Transformation for a Sustainable World

conversion to radio signals at 92 and 108 GHz. The
generated signals were fed to a 35-dBi antenna and
transmitted into free space using an identical wireless link
with those shown in Figs. 3 and 6. Photonic downconversion
was employed for signal demultiplexing. Another two-tone
optical signal with a frequency separation of 80 GHz was
generated. The two sidebands were separated, and the lower
sideband was used for signal modulation. At the output of
the modulator, the signal, as shown in inset B of Fig. 8, was
divided into two parts using an optical coupler. In one part,
the signal was input to an optical filter, and the optical carrier
and one modulated sideband of the 92-GHz signal were
selected. The selected signal, shown in inset C of Fig. 8, was
transmitted to an AP and input to another high-speed PD to
generate a signal at 92 GHz. The signal was transmitted to
an Rx using the same 2-m wireless link as that shown in Fig.
6. Finally, the signal was down-converted to the microwave Fig. 9. Performance of 28- and 92-GHz signals.
band and demodulated using 5G NR software. In the other
part, photonic downconversion was employed to down- transmission, the other 5G NR signal was turned off at the
converting the 108-GHz signal to 28 GHz. The upper CS. Satisfactory performance was achieved for all signal
modulated sideband of the 108 GHz signal was selected and transmissions. For the 28-GHz signal, the performance of the
combined with the upper unmodulated sideband of the two- single transmission was better than that of the simultaneous
one optical signal. The frequency separation between the two transmission, especially in the high-photocurrent region.
sidebands of the combined signal was 28 GHz (= 108–80 However, the performance of the 92-GHz signal for
GHz), as shown in the inset D of Fig. 8. The combined signal simultaneous transmission was slightly better. This could be
was transmitted to an AP and input to a low-speed PD for due to the optimal ratio of the optical carrier and modulation
conversion into a radio signal at 28 GHz. The signal was sidebands in each case. Moreover, the 28-GHz signal
transmitted to free space using a 28-dBi horn antenna. After performed better than the 92-GHz signal. This is attributed
transmission over approximately 2 m in free space, the to the superior performance of the devices at 28 GHz. The
signals were received using another antenna and sent to a results confirmed the possibility of simultaneous generation,
receiver for demodulation. transmission, reception, and distribution of multiple radio
signals in different frequency bands. The system is flexible
Table 3 – Multi-RAN and IAB system and can be used in different applications, including multiple-
RAN coexistence and in-band and out-band IAB.
Parameter Value Parameter Value
6. CONCLUSIONS AND OUTLOOK
Radio link 1 (RRH to RN)
Frequency 92, 108 GHz Distance 4 m Radio communications in the mmW and THz bands play a
Tx. antenna 35 dBi Rx antenna 42 dBi vital role in providing high-speed and low-latency services.
However, current bottlenecks must be overcome to construct
92-GHz radio link (AP to Rx)
a high-speed, cost-effective, and energy-efficient network
Frequency 92 GHz Distance 2
for achieving sustainable development goals. Photonic
Tx. antenna 25 dBi Rx antenna 25 dBi technology is promising not only for generation and
5G NR 64 QAM 200 MHz EVM 5.3% transmission, but also for the reception and downconversion
of radio signals to reduce the cost, complexity, power
28-GHz radio link (AP to Rx)
consumption, and footprint of antenna sites and transceivers.
Frequency 28 GHz Distance 2m
In this paper, we present key fiber–wireless technologies that
Tx. antenna 28 dBi Rx antenna 28 dBi
can enable the deployment of radio communications in the
5G NR 64-QAM 200 MHz EVM 4% mmW and THz bands. A seamless fiber–wireless bridge
system using all-photonic transceivers is useful for high-
Table 3 summarizes the main parameters and performance speed, low-latency, and energy-efficient communications in
of the system. We transmitted 5G NR standard-compliant FWA and emergency events. A radio signal transparent relay
signals over both the 28- and 92-GHz systems. A 200-MHz and routing system is promising for extending the coverage
bandwidth 64-QAM 5G NR signal at 12 and 18 GHz was to indoor environments and dead-zone areas. Additionally,
generated using commercial software and transmitted over the simultaneous generation, transmission, and reception of
the system. Figure 9 shows the performance of the 28- and multiple radio signals in different frequency bands can
92-GHz signals for different photocurrents of the PD at the facilitate the deployment of multiple RAN and IAB
RRH. The EVM required for a 64-QAM signal is 8% [13]. technologies in 6G and beyond networks. The obtained
For comparison, the signal performances with and without results confirm the potential of the proposed systems and can
the simultaneous transmission with the other signal are also pave the way for the deployment of radio communication in
shown in the figure. In the case of a single-signal high-frequency bands in IMT-2030 and beyond.

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