2. Millimeter-wave photonics technique in 5G fiber-wireless networks

Based on 4G LTE progress [3], 5G NR is in principle a novel stage of unprecedented technological innovation with ubiquitous speed connectivity. As a result, it is expected that 5G NR will radically transform a number of industries and will provide direct, super-speed connections between any users and any sensors and devices. By now, several reviews to analyze significant changes in the 5G NR approaches as compared to the existing 4G LTE networks have been published [8, 11] denoting a series of milestones. Developing this topic, Table 1 summarizes the results of the advanced analysis focusing on the investigations referred to a fronthaul network with mobile communication in mmWave-band.

The review of the current R&Ds in 5G NR area convincingly demonstrates the consistent achievement of the designated in Table 1 milestones, which is reflected in a vast number of publications and emergence of commercial products. Among them, much attention is paid to radically expanding the available spectral bands up to mmWaves (see item 1 of Table 1) to promote the throughput of mobile communication system. Following this tendency, currently, the local telecommunications commissions of various countries are proposing and harmonizing the plans of frequency allocation in mmWave-band, which will be reviewed this year at the World Radio Conference (WRC-2019). Currently, for the 5G NR networks, it is planned to allocate two frequency bands (see Figure 1), coexisting with available 4G LTE systems in the 1–6 GHz band (the so-called "low range" (LR)) and new one in the mmWaves within the range of 24.5–86 GHz according to [12] (the so-called "high range" (HR)).

Based on various investigations, let us review the key advantages and disadvantages of the mobile communication system operation in the millimeter range. The following are the advantages of the 5G mmWave mobile communication:

Design of Reconfigurable Multiple-Beam Array Feed Network Based on Millimeter-Wave… DOI: http://dx.doi.org/10.5772/intechopen.89076



terminals [7, 8]. This approach should lead to a newer network design technology using Radio-over-Fiber (RoF) building concept as well as PAA-assisted remote stations (RS) and user terminals (UT) [8, 9]. On this way, integrated and millimeter-wave (mmWave) photonics are extremely attractive technologies for realizing a PAA's interactive optical BFN due to its superior instantaneous operating

Following it, recently we designed photonics-based BFNs for ultrawide bandwidth mmWave (57–76 GHz) antenna arrays [10]. Elaborating the direction, in this chapter, we review the worldwide progress referred to designing multiple-beam photonic BFN and highlight our last simulation results on design and optimization of millimeter-photonics-based matrix beamformers. Thus, in the rest of the sections, the following topics are under consideration. In particular, Section 2 reviews the specialties of mmWave photonics technique in 5G mobile networks of RoF technology based on fiber-wireless (FiWi) architecture. In addition, Section 3 presents theoretical background of array antenna multiple-beam steering using ideal models of matrix-based phase shifters and time delay lines. Section 4 includes a general analysis of radiation pattern sensitivity to compare updated photonics beamforming networks produced on phase shifter or true-time delay (TTD) approach. The principles and ways to optimized photonics BFN design are discussed in Section 5 based on the photonics BFN scheme including integrated 88 optical Butler matrix (OBM). All schemes are modeled using VPIphotonics Design Suite and MATLAB software tools. Finally, Section 6

2. Millimeter-wave photonics technique in 5G fiber-wireless networks

fronthaul network with mobile communication in mmWave-band.

Based on 4G LTE progress [3], 5G NR is in principle a novel stage of unprecedented technological innovation with ubiquitous speed connectivity. As a result, it is expected that 5G NR will radically transform a number of industries and will provide direct, super-speed connections between any users and any sensors and devices. By now, several reviews to analyze significant changes in the 5G NR approaches as compared to the existing 4G LTE networks have been published [8, 11] denoting a series of milestones. Developing this topic, Table 1 summarizes the results of the advanced analysis focusing on the investigations referred to a

The review of the current R&Ds in 5G NR area convincingly demonstrates the consistent achievement of the designated in Table 1 milestones, which is reflected in a vast number of publications and emergence of commercial products. Among them, much attention is paid to radically expanding the available spectral bands up to mmWaves (see item 1 of Table 1) to promote the throughput of mobile communication system. Following this tendency, currently, the local telecommunications commissions of various countries are proposing and harmonizing the plans of frequency allocation in mmWave-band, which will be reviewed this year at the World Radio Conference (WRC-2019). Currently, for the 5G NR networks, it is planned to allocate two frequency bands (see Figure 1), coexisting with available 4G LTE systems in the 1–6 GHz band (the so-called "low range" (LR)) and new one in the mmWaves within the range of 24.5–86 GHz according to [12] (the so-called

Based on various investigations, let us review the key advantages and disadvantages of the mobile communication system operation in the millimeter range. The

following are the advantages of the 5G mmWave mobile communication:

bandwidth, immunity to electromagnetic interference, lightweight, and

reconfigurability [3].

Advances in Array Optimization

concludes the chapter.

"high range" (HR)).

110

The milestones in the way to transform 4G LTE to 5G NR.

Figure 1. Planned 5G NR spectrum allocations [12].


Due to these benefits, 5G mmWave is suitable for mobile communication over sub-6 GHz wireless technologies. The main disadvantages of 5G mmWave communication are the next:


• The service radius of the pico-cell under investigation is 50 m.

• The operating frequency band is 37.0–43.5 GHz (see Figure 1).

neously exchanging information with several RSs.

Sketch of a typical wireless pico-cell for 5G access network.

DOI: http://dx.doi.org/10.5772/intechopen.89076

steering

113

Figure 2.

3. Theoretical background of multiple-beam array antenna beam

Design of Reconfigurable Multiple-Beam Array Feed Network Based on Millimeter-Wave…

As noted in chapter 2, mmWave array antennas capable of operating in ultrawide frequency range are considered as one of the key enabling technologies for designing RS of 5G NR network. There, a formation of a narrow steered beam by means of a PAA makes it possible to increase the directive gain to compensate for the excessive loss in the mmWave-band. Besides, the use of narrow beams would reduce the interference effects from other closely spaced mobile terminals and provides the possibility of spatial multiplexing to increase throughput while simulta-

Generally, electronic scanning in the PAA is provided by a beamforming network, which includes phase shifters or delay lines [1]. The BFN supports a continuous or discrete beam movement in space due to phase control or signal delay between the array elements. In our previous work devoted to the study of the PAA BFN [10], a single-beam PAA with electron scanning of the radiation pattern was considered. Nevertheless, for 5G pico-cells in conditions of simultaneous communication with a large number of terminal units, using a set of multiple-beam antenna (MBA) is considered to be a more practical way. PAAs based on MBA have greater functionality, but they are very complex, bulky, energy-consuming, and expensive devices. These factors limit their use to date mainly in special-purpose radars and unique satellite communication stations, for example, in satellite arrays of the iridium global mobile communication system [15]. There, PAA of the transponder has 106 channels and forms 16 fixed beams covering the contour-shaped

These disadvantages must be considered during 5G mmWave link budget calculation.

The drawbacks mentioned above led to the need for a radical change in the architecture of access networks compared to 4G LTE. In particular, instead of macro-cells, a multistage configuration was introduced, additionally containing micro-cells and pico-cells [3, 14]. In this direction, a newer RoF-based access networks of FiWi architecture is considered as the most promising approach (see item 3 of Table 1) ([9, 11]). The reason is that the important drawback for the implementation of the wired links, for example, of Fiber-to-the-Home (FTTH) architecture is feasible for fixed UTs only. In contrast, current wireless access networks of 4G LTE that provide a flexible communication with a relatively simple infrastructure cannot meet growing in geometric progression demands to increase the capacity of mobile systems. The most promising technique to meet it, which is actively discussed in the referred publications, is to expand the operating frequency band and to apply multi-position digital modulation of a radio frequency (RF) carrier through fiber fronthaul to simplify pico-cell RS layout. Figure 2 illustrates a typical pico-cell in a large city. The mmWave wireless network is managed from a remote station including one unidirectional PAA for downlink and uplink channels.
