The remarkable growth of wireless data traffic in recent times has driven the need to explore suitable regions in the radio spectrum to meet the projected requirements. In pursuance of this, millimeter wave communications have received considerable attention in the research fraternity. Due to the high path and penetration losses at millimeter wavelengths, antenna beamforming assumes a pivotal role in establishing and maintaining a robust communication link. Beamforming for millimeter wave communications poses a multitude of diverse challenges due to the large channel bandwidth, unique channel characteristics, and hardware constraints. In this paper, we track the evolution and advancements in antenna beamforming for millimeter wave communications in the context of the distinct requirements for indoor and outdoor communication scenarios. We expand the scope of discussion by including the developments in radio frequency system design and implementation for millimeter wave beamforming. We explore the suitability of millimeter wave beamforming methods, both, existing and proposed till midyear 2015, and identify the exciting new prospects unfolding in this domain.

Beamforming for Millimeter Wave Communications: An Inclusive Survey

This article discusses the challenges, benefits and approaches associated with realizing largescale antenna arrays at mmWave frequency bands for future 5G cellular devices. Key design considerations are investigated to deduce a novel and practical phased array antenna solution operating at 28 GHz with near spherical coverage. The approach is further evolved into a first-of- a-kind cellular phone prototype equipped with mmWave 5G antenna arrays consisting of a total of 32 low-profile antenna elements. Indoor measurements are carried out using the presented prototype to characterize the proposed mmWave antenna system using 16-QAM modulated signals with 27.925 GHz carrier frequency. The biological implications due to the absorbed electromagnetic waves when using mmWave cellular devices are studied and compared in detail with those of 3/4G cellular devices.

Study and prototyping of practically large-scale mmWave antenna systems for 5G cellular devices

This paper presents the first reported 28-GHz phased-array IC for 5G communications. Implemented in 130-nm SiGe BiCMOS, the IC includes 32 TRX elements and features concurrent independent beams in two polarizations in either TX or RX operation. Circuit techniques to enable precise beam steering, orthogonal phase and amplitude control at each front end, and independent tapering and beam steering at the array level are presented. A TX/RX switch design is introduced which minimizes TX path loss resulting in 13.5 dBm/16 dBm Op1dB/Psat per front end with >20% peak power added efficiency of the power amplifier (including switch and off-mode LNA) while maintaining a 6 dB noise figure in the low noise amplifier (including switch and off-mode PA). Comprehensive on-wafer measurement results for the IC across multiple samples and temperature variation are presented. A package with four ICs and 64 dual-polarized antennas provides eight 16-element or two 64-element concurrent beams with 1.4°/step beam steering (<0.6° rms error) across a ±50° steering range without requiring calibration. A maximum saturated effective isotropic radiated power of 54 dBm is measured in the broadside direction for each polarization. Tapering control without requiring calibration achieves up to 20-dB sidelobe rejection without affecting the main lobe direction.

A 28-GHz 32-Element TRX Phased-Array IC With Concurrent Dual-Polarized Operation and Orthogonal Phase and Gain Control for 5G Communications

While 5G is being commercialized worldwide, research institutions around the world have started to look beyond 5G and 6G is expected to evolve into green networks, which deliver high Quality of Service and energy efficiency. To meet the demands of future applications, significant improvements need to be made in mobile network architecture. We envision 6G undergoing unprecedented breakthrough and integrating traditional terrestrial mobile networks with emerging space, aerial and underwater networks to provide anytime anywhere network access. This paper presents a detailed survey on wireless evolution towards 6G networks. In this survey, the prime focus is on the new architectural changes associated with 6G networks, characterized by ubiquitous 3D coverage, introduction of pervasive AI and enhanced network protocol stack. Along with this, we discuss related potential technologies that are helpful in forming sustainable and socially seamless networks, encompassing terahertz and visible light communication, new communication paradigm, blockchain and symbiotic radio. Our work aims to provide enlightening guidance for subsequent research of green 6G.

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A Survey on Green 6G Network: Architecture and Technologies

Ultra-high bandwidth, negligible latency and seamless communication are envisioned as milestones that will revolutionize the way by which societies create, distribute and consume information. The remarkable expansion of wireless data traffic has advocated the investigation of suitable regimes in the radio spectrum to satisfy users’ escalating requirements and allow the exploitation of massive capacity and massive connectivity. To this end, the Terahertz (THz) frequency band (0.1-10 THz) has received noticeable attention in the research community as an ideal choice for scenarios involving high-speed transmission. As such, in this work, we present an up-to-date review paper to analyze key concepts associated with the THz system architecture. THz generation methods are first addressed by highlighting the recent progress in the devices technology. Moreover, the recently proposed channel models available for propagation at THz band frequencies are introduced. A comprehensive comparison is then presented between the THz wireless communication and its other contenders. In addition, several applications of THz communication are discussed taking into account various scales. Further, we highlight the milestones achieved regarding THz standardization activities. Finally, a future outlook is provided by presenting and envisaging several potential use cases and attempts to guide the deployment of the THz frequency band.

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Terahertz Band: The Last Piece of RF Spectrum Puzzle for Communication Systems

A 60GHz short-range wireless system offers new opportunities for achieving wireless high-definition video links and multi-Gb/s wireless data transfer. Recent works have realized a 60GHz transceiver by means of a cost-effective CMOS process [1-3], but using a 60GHz system in mobile terminals poses the difficult challenge of achieving low power consumption as well as small form factor. The publication [3] achieves a power consumption of less than 756mW, but uses a simple MAC protocol incompatible with global standards and also suffers from a limited distance of less than 4cm. This paper presents a fully integrated transceiver chipset based on WiGig/IEEE802.11ad standards targeting mobile usage. The chipset is developed for a single-carrier (SC) modulation, which is suitable for reduced power consumption as compared to using OFDM modulation. However, the SC modulation is sensitive to in-band amplitude variation, mainly made worse by the gain variation of analog circuits and multipath delay spread. In order to compensate for those gain variations, the proposed chipset employs built-in TX in-band calibration and an RX frequency domain equalizer (FDE). The proposed techniques can relax the requirement for high speed analog circuits, leading to less power consumption while minimizing the increase of hardware size.

A fully integrated 60GHz CMOS transceiver chipset based on WiGig/IEEE802.11ad with built-in self calibration for mobile applications

A single-chip CMOS transceiver (TRX) capable of wireless data rates up to 80 Gb/s using part of frequencies (252–279 GHz) covered by IEEE Std 802.15.3d is presented. The TRX chip operates in either transmitter (TX) or receiver (RX) mode at frequencies comparable to ${f_{\mathrm {max}}}$ of the NMOSFET. The TX part adopts mixer-last architecture with four-way power combining using a ring circuit called a double-rat-race. The RX part adopts fundamental-mixer-first direct-conversion architecture. In the RX mode, the TX serves as an LO multiplier chain, which conventionally accounted for a significant part of the RX die area. The double-rat-race, having an improved design than the original one, integrates the TX and RX and also rejects unwanted harmonics generated by the frequency-doubler-based upconversion mixer. Low-loss, low-characteristic-impedance transmission lines are used extensively to combat losses. The TRX was fabricated using a 40-nm CMOS process. The saturated output power of the TX is −1.6 dBm at 265.68 GHz. The mean single-sideband noise figure (SSB NF) of the RX is 22.9 dB. The TX mode and the RX mode consume dc power of 890 and 897 mW, respectively. A wireless data rate of 80 Gb/s between a pair of TRX chips is demonstrated with 16QAM over a distance of 3 cm.

An 80-Gb/s 300-GHz-Band Single-Chip CMOS Transceiver

IEEE Standard 802.15.3d, published in October 2017, defines a high-data-rate wireless physical layer that enables up to 100Gb/s using the lower THz frequency range between 252 and 325GHz (hereafter referred to as the “300GHz band”). It stipulates that the 300GHz band be channelized into thirty-two 2.16GHz-wide channels (Fig. 9.5.1) or a smaller number of wider channels whose bandwidths are all integer multiples of 2.16GHz. This paper presents a CMOS transceiver (TRX) chip targeted at channels 49 through 51 and 66 of 802.15.3d (Fig. 9.5.1). The TRX was fabricated using a 40nm CMOS process. There have been reports on solid-state transceivers (TRXs) operating in or near the 300GHz band [1]–[6]. Some of these [1]–[3] were TX/RX or block-level chipsets, which can enjoy more flexibility in design and independent optimization of TX and RX. They successfully achieved $\geq 64$ Gb/s. On the other hand, single-chip TRXs [4]–[6] did not always reveal achievable data-rates nor were capable of supporting quadrature amplitude modulation (QAM). Nevertheless, eventual development of full-featured single-chip TRXs is desirable especially for applications requiring deployment of many TRXs, as is envisioned implicitly by 802.15.3d. The single-chip QAM-capable CMOS TRX presented herein is an outcome of efforts in that direction.

9.5 An 80Gb/s 300GHz-Band Single-Chip CMOS Transceiver

An injection locked frequency divider and a PLL circuit, having a wide operating frequency bandwidth and capable of reducing the influence of any parasitic capacitance, are provided. Injection locked frequency divider ( 100 ) includes ring oscillator 140 that cascade-connects first amplifier circuit ( 141 ) including N-channel MOS transistor ( 111 ) and P-channel MOS transistor ( 112 ), and second amplifier circuit 142 and third amplifier circuit ( 143 ) that have the same configuration as first amplifier circuit ( 141 ) in three stages in a ring; N-channel MOS transistor 150 in which the sources of N-channel MOS transistors ( 111, 121, 131 ) in the respective stages are connected to the drain thereof; and differential signal injection circuit ( 160 ) that injects injection signal I 1 to the gates of P-channel MOS transistors ( 112, 122, 132 ) in the respective stages and injects a reverse phase signal of injection signal I 1 . as a differential signal to the gate of N-channel MOS transistor ( 150 ).

Injection-locked frequency divider and pll circuit

A radio communication system includes a base station (104) of a radio communication system A, a base station (106) of a radio communication system B operation in non-synchronized way with the base station (104), and a mobile station (101) capable of communicating with both of the radio communication system A and the radio communication system B. The base station (104) includes a radio unit for transmitting/receiving a radio wave to/from the mobile station (101) and a system information estimation unit for estimating the system information on the radio communication system B and outputting the system estimation information. The radio unit of the base station (104) reports the system estimation information on the base station (106) to the mobile station (101). The mobile station (101) receives the system estimation information on the base station (106) in advance so as to perform effective switching without using a cabled connection from the radio communication system A to the radio communication system B via a relay device or the like.

Junji Sato

Papers

A fully integrated 60GHz CMOS transceiver chipset based on WiGig/IEEE802.11ad with built-in self calibration for mobile applications

An 80-Gb/s 300-GHz-Band Single-Chip CMOS Transceiver

9.5 An 80Gb/s 300GHz-Band Single-Chip CMOS Transceiver

Injection-locked frequency divider and pll circuit

Radio communication system base station and mobile station