Page 10 - ITU Journal Future and evolving technologies – Volume 2 (2021), Issue 2

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 2

Computer-aided design for analog wireless fronthaul of B5G cellular
communication systems

Pages 35-46
Mikhail E. Belkin, Vladislav Golovin, Yuriy Tyschuk, Alexander S. Sigov

Specialties of an analog fronthaul based on Radio-over-Fiber architecture and key principles of
exploiting microwave photonics technology when designing a millimeter-wave Radio Unit (RU) are
reviewed and discussed. To clarify, in this paper we perform a comparative simulation for a specific
example of developing an obligatory RU's node as a reference oscillator with an output radio frequency
(RF) of more than 100 GHz, which is typically implemented by means of a circuit that includes a
relatively low-frequency RF oscillator followed by a high-order frequency multiplier. Following the
principles and approaches outlined, we propose and describe two alternative schemes for implementing
a frequency multiplier from 4.25 to 102 GHz using microwave-electronics or microwave-photonics
approach. Further, using Cadence AWRDE software with an additional introduction of the previously
proposed models of optoelectronic devices, their main characteristics are considered. To ensure the
practical orientation of the model experiments, the parameters of each of the models used are selected
based on the specifications of commercially available discrete components.
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EMR: A new metric to assess the resilience of directional mmWave
channels to blockages

Pages 47-60
Fatih Erden, Ozgur Ozdemir, Ismail Guvenc, David W. Matolak

Millimeter-wave (mmWave) communication systems require narrow beams to compensate for high
path loss and to increase the communication range. If an obstacle blocks the dominant communication
direction, alternative paths (directions) should be quickly identified to maintain reliable connectivity.
In this paper, we introduce a new metric to quantify the Effective Multipath Richness (EMR) of a
directional communication channel in the angular domain. In particular, the proposed metric takes into
account the strength and spatial diversity of the resolved Multipath Components (MPCs), while also
considering the beamwidth of the communication link and the blockage characteristics. The metric is
defined as a weighted sum of the number of distinct MPC clusters in the angular domain, where the
clustering of the MPCs is performed based on the cosine-distance between the dominant MPCs. For a
given transmitter (TX) and receiver (RX) pair, the EMR is a single scalar value that characterizes the
robustness of the communication link against blockages, as it captures the number of unique
communication directions that can be utilized. It is also possible to characterize the blockage robustness
for the whole environment by evaluating the spatial distribution of the EMR metric considering various
different TX/RX locations. Using our proposed metric, one can assess the scattering richness of
different environments to achieve a particular service quality. We evaluate the proposed metric using
our 28 GHz channel measurements in a library environment for Line-of-Sight (LOS) and NLOS
scenarios, and compare it with some other commonly used propagation metrics. We argue that EMR is
especially informative at higher frequencies, e.g., mmWave and terahertz (THz), where the propagation
attenuation is high, and directional Non-Light-of-Sight (NLOS) communication is critical for the
success of the network.
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