Quantum Dot Coherent Comb Laser Source for Converged Optical-Wireless Access Networks

5G emerges with ultra-dense deployments of small cell networks to serve various vertical sectors’ location specific service requirements. While the development of technical solutions for network densification is progressing, less attention is paid to the spectrum models for the new ultra-dense networks and location specific service offerings. This paper examines the problems currently faced by industry in acquiring spectrum to support the Industrial Internet of Things (IIOT). Industrial applications where such spectrum is needed were assessed and their requirements identified. The US Citizens Broadband Radio Service (CBRS) spectrum sharing model to support the IIOT needs is introduced and how it addresses the IIOT requirements were evaluated based on four different real-life use cases. This study developed a view of options for the spectrum supply side, how this could interface with demand from private networks. Results showed that the CBRS model is well suited for several IIOT use cases based on having smaller licensed areas for PALs allowing a low-cost path for acquiring exclusive use spectrum along with a no cost option of using GAA spectrum. The leasing rules defined for CBRS PALs also provides an excellent minimal overhead option for enterprises to lease spectrum to other neighboring enterprises. Furthermore, the CBRS concept was found to leverage all the three forces of the long tail framework: Democratizing the tools of production through access to affordable spectrum, cutting the costs of consumption by democratizing distribution with web-scale automatization and connecting supply and demand via marketplace via SAS.

To overcome the spectrum scarcity issues, the citizens broadband radio service (CBRS) presents a centralized spectrum management solution. The efficiency of spectrum utilization could be further improved by introducing spectrum trading. Blockchain-based spectrum trading has been considered as a decentralized, flexible, and secure approach. However, current studies rarely investigate the interference to incumbent users caused by spectrum trading between CBRS devices (CBSDs), and the scalability issues in blockchain-based spectrum trading are rarely discussed. To address the problems above, this paper develops the blockchain-based spectrum trading mechanisms for CBRS. Particularly, we propose a queuing mechanism for intra-coexistence group (CxG) trading, in which spectrum trading is leveraged to reduce the aggregated interference to incumbents. A new parameter termed “network feature” is proposed to prioritize spectrum transactions in different queues, which helps to achieve the trade-off between the interference to incumbents and resource requirements in spectrum transactions. Furthermore, we propose a multi-blockchain architecture and a corresponding cross-chain mechanism to improve the speed of inter-CxG spectrum trading. Simulation results show that the aggregated interference to incumbents can be reduced by adopting the proposed method. Meanwhile, when adopting the proposed cross-chain spectrum trading mechanism, the network throughput can be improved by up to 24% compared with the traditional CBRS spectrum management framework.

Dynamic spectrum sharing (DSS) has recently attracted keen interest from regulatory bodies around the world as a key strategy to overcome spectrum scarcity in beyond 5G networks. In the United States, the Federal Communications Commission has adopted a three-tier DSS model for the Citizens Broadband Radio Service (CBRS) band managed by a spectrum access system (SAS) to share incumbents' spectrum with commercial cellular broadband applications. In this article, we first present a survey of current DSS approaches and their limitations and then discuss the benefits of using in-band full-duplex (IBFD) techniques in DSS networks. To illustrate the improvement in the performance of priority access license (PAL) and general authorized access (GAA) users in an IBFD-assisted CBRS, we consider a CBRS mobile broadband network (MBN) architecture comprising an incumbent in the form of a MIMO radar system and an IBFD MIMO MBN, consisting of PAL and GAA users. In particular, we design joint beamformers at the MBN, with constraints on transmit power at the MBN and detection probability of the radar system, and beamformers at the radar system to mitigate the interference from the radar system toward the cellular system. It is shown that the IBFD CBRS network architecture not only leads to improved performance of PAL and GAA users, but does so while producing less interference toward the radar than state-of-the-art half-duplex solutions. Finally, we present some open research challenges to invigorate research on beyond 5G IBFD DSS networks.

The Citizens Broadband Radio Service (CBRS) band in the United States, particularly the 3.5 GHz frequency range, has emerged as a pivotal asset in accelerating 5G deployment. This paper explores the strategic approaches and inherent challenges associated with implementing CBRS spectrum for 5G networks. By leveraging shared access models and spectrum management frameworks, CBRS provides opportunities for both mobile network operators and private network implementers. This study reviews the current state of CBRS integration in 5G, highlights the primary deployment strategies, and discusses challenges in regulatory, technical, and economic domains.

Abstract— The development of the "Smart City" concept has historically been limited by public cellular networks and the fragmentation of unlicensed connectivity standards. As cities transition from passive data collection to active, real-time automation, the need for deterministic latency, enhanced security, and widespread coverage has driven the adoption of a new architectural approach. This paper explores the emerging role of Private Wireless Networks (PWNs), particularly Private 5G (P5G) and Private LTE, which utilize shared-spectrum frameworks like the Citizens Broadband Radio Service (CBRS) as the foundation for future urban management. Through a comprehensive technical comparison, this study demonstrates that Private 5G surpasses Wi-Fi 6 and LoRaWAN in mission-critical applications, especially those requiring mobility and ultra-reliable low-latency communication (URLLC). Additionally, we review key deployments in Las Vegas (USA), Sunderland (UK), Liverpool (UK), Tucson (USA), and Brownsville (USA) to assess tangible impacts on traffic management, digital inclusion, public safety, and autonomous logistics. The research concludes that, despite regulatory and integration challenges, transitioning toward municipal "micro-operators" and neutral host architectures offers a viable path for sustainable, sovereign, and scalable smart city connectivity. Keywords: Private 5G, Private LTE, CBRS, Smart Cities, Industrial Internet of Things (IIoT), Wi-Fi 6, LoRaWAN, Connected and Automated Logistics (CAL), Network Slicing, Municipal Infrastructure.

Explosion of the multitude of current and future wireless services has motivated the search for more efficient ways to allocate spectrum than fixed channel allocations enforced by regulatory agencies. In particular, dynamic spectrum‐sharing techniques allow spectrum to be assigned or selected for use based on the users and demand in a given geographic region. In this chapter, we consider collaborative spectrum sharing (CSS), in which users or networks share information about their spectrum needs and usage to facilitate efficient use of spectrum resources. We provide an ontology of CSS approaches and give an overview of previous CSS research. Then, we provide a more in‐depth discussion of the roles of CSS in two different example systems. The first is the Citizen Broadband Radio Service (CBRS), which is a system established by the Federal Communications Commission (FCC) in the United States, and which uses a centralized, hierarchical approach to CSS. The second is the Spectrum Collaboration Challenge (SC2), which was a competition run by the Defense Advanced Research Projects Agency (DARPA) in the United States to develop intelligent radios systems for CSS. In contrast to CBRS, the SC2 enforces a distributed, unified approach to CSS. The chapter concludes with a brief discussion of the progress and challenges in implementing CSS.

Emergence of shared spectrum, such as the 3.5-GHz citizen broadband radio service (CBRS) band in the U.S., promises to broaden the mobile operator ecosystem and lead to proliferation of small cell deployments. We consider the inter-operator interference problem that arises when multiple small cell networks access the shared spectrum. Towards this end, we take a novel communication-free approach that seeks implicit coordination between operators without explicit communication. The key idea is for each operator to sense the spectrum through its mobiles to be able to model the channel vacancy distribution and extrapolate it for the next epoch. We use reproducing kernel Hilbert space kernel embedding of channel vacancy and predict it by vector-valued regression. This predicted value is then relied on by each operator to perform independent but optimal channel assignment to its base stations taking traffic load into account. Via numerical results, we show that our approach, aided by the above channel vacancy forecasting, adapts the spectrum allocation over time as per the traffic demands and more crucially, yields as good as or better performance than a coordination-based approach, even without accounting the overhead of the latter.

A proof of concept system that enables real-time geospatial spectrum sharing between 5G/6G networks and Earth Exploration Satellite Services (EESS) has been developed. A simple algorithm that pauses network transmissions when there is potential interference from 5G/6G transmitters provides 99.6% network availability in the 24 GHz NR2 band while protecting all currently working EESS radiometers operating in the 23.8 GHz band. A more sophisticated algorithm that modifies transmission power levels and (if necessary) network traffic (similar to the methodologies used by Citizens Broadband Radio Service) can reduce interference so that there is no adverse impact on network availability. In addition to preventing interference, RGSS provides other significant benefits to both the wireless and the weather/climate communities, including improving network performance and coverage, the ability to support changes in network architectures, network elements, endpoints, and new or more sensitive radiometers, and a simple mechanism to test and police compliance with out-of-band emission requirements. RGSS is also compatible with existing spectrum management systems.

A droplet-shape inspired wideband bow-tie dielectric resonator antenna for sub-6 GHz and IoT applications

<title>Abstract</title> Efficient spectrum sharing in the Citizens Broadband Radio Service (CBRS) band is essential for maximizing 5G networkcapacity, particularly when high-traffic base stations require simultaneous access to multiple channels. Standard formulationsof the Quantum Approximate Optimization Algorithm (QAOA) impose such multi-channel constraints using penalty terms, somost of the explored Hilbert space corresponds to invalid assignments. We propose a subspace-confined QAOA tailored toCBRS multi-channel allocation, in which each node-wise channel register is initialized in a Generalized Dicke state and evolvedunder an intra-register XY mixer. This ansatz confines the dynamics to a tensor product of Johnson graphs that exactly encodeper-node Hamming-weight constraints. For an 8-node CBRS interference graph with 24 qubits, the effective search space isreduced from the full Hilbert space of size 2^24 to 2,916 feasible configurations. Within this subspace, the algorithm convergesrapidly to low-conflict assignments without large penalty coefficients. Simulations on instances with up to eight nodes showthat the proposed ansatz achieves near-optimal conflict levels and consistently outperforms standard penalty-based QAOAand a greedy classical heuristic in terms of feasibility. Noise simulations with depolarizing channels further indicate that theconstraint-preserving structure maintains a high feasibility ratio in NISQ-relevant error regimes.

In this paper, we investigate the coexistence of the 5G communication network with a fixed-satellite service (FSS) in the 3.5 GHz and 26 GHz frequency bands. We analyze a distance protection scheme for the FSS Earth station (ES) and 5G base stations (BS). Furthermore, we define the exclusion and restriction zones to develop a transmit power control scheme based on the Citizens Broadband Radio Service (CBRS). An interactive power control scheme is also devised for the restriction zone and extensively analyzed through simulations. The proposed scheme is examined for practical scenarios such as the rural macrocells (RMa), urban macrocells (UMa), and urban microcells (UMi) as defined by the 3GPP. The impact of the antenna type is also investigated, and BSs with omnidirectional, 4 × 4, 8 × 8, and 16 × 16 antenna arrays are examined, as defined by 3GPP, for the 5G networks. The results confirm that 5G systems can coexist with the FSS and provide quantitative insights into the selection of the system parameters, including interference margins, exclusion sizes, and reduction zones, for different scenarios and antenna types.

Machine learning provides automated means to capture complex dynamics of wireless spectrum and support better understanding of spectrum resources and their efficient utilization. As communication systems become smarter with cognitive radio capabilities empowered by machine learning to perform critical tasks such as spectrum awareness and spectrum sharing, they also become susceptible to new vulnerabilities due to the attacks that target the machine learning applications. This chapter identifies the emerging attack surface of adversarial machine learning and corresponding attacks launched against wireless communications in the context of 5G systems. The focus is on attacks against (i) spectrum sharing of 5G communications with incumbent users such as in the Citizens Broadband Radio Service (CBRS) band and (ii) physical layer authentication of 5G User Equipment (UE) to support network slicing. For the first attack, the adversary transmits during data transmission or spectrum sensing periods to manipulate the signal-level inputs to the deep learning classifier that is deployed at the Environmental Sensing Capability (ESC) to support the 5G system. For the second attack, the adversary spoofs wireless signals with the generative adversarial network (GAN) to infiltrate the physical layer authentication mechanism based on a deep learning classifier that is deployed at the 5G base station. Results indicate major vulnerabilities of 5G systems to adversarial machine learning. To sustain the 5G system operations in the presence of adversaries, a defense mechanism is presented to increase the uncertainty of the adversary in training the surrogate model used for launching its subsequent attacks.

This paper describes a radio architecture for distributed spectrum sharing of multiple channels among secondary users (SUs) in a wide band of frequencies and a localized area. A novel Multichannel Immediate Multiple Access (MIMA) physical layer is developed such that each SU can monitor all the channels simultaneously for incoming signals and achieve fast rendezvous within the multiple channels. The spectrum utilized by an SU pair can be changed dynamically based upon spectrum sensing at the transmitter and tracking synchronization and control messages at the receiver. Although information about the number of active SUs can be used to improve the spectrum sharing efficiency, the improvement is small relative to the cost of obtaining such information. Therefore, the architecture adopts Multichannel Carrier Sense Multiple Access (CSMA) for medium access control regardless of the number of active SUs. A prototype implementation of the architecture has been developed using an advanced software defined radio (SDR) platform. System tests demonstrate that the spectrum sharing efficiency of the prototype is close to an upper bound if the signal-to-noise ratio (SNR) is sufficiently high. Among other practical issues, imaged interference caused by hardware IQ imbalance limits system performance. In the prototype, the MIMA is based on an LTE waveform. Therefore, the spectrum sharing radio can be potentially applied to the 3.5 GHz radar band for Citizens Broadband Radio Service (CBRS).

Cellular operators have begun deploying 5G New Radio (NR) in all available bands: low ( 24 GHz) to exploit the different capabilities of each. At the same time, traditional 4G Long Term Evolution (LTE) deployments are being enhanced with the addition of bands in the unlicensed 5 GHz (using License Assisted Access, or LAA) and the 3.5 GHz Citizens Broadband Radio Service (CBRS) resulting in throughput performance comparable to 5G in mid-band. We present a detailed study comparing 4G and 5G deployments, in all bands in Chicago, and focused mmWave measurements and analysis in Miami. Our methodology, based on commercial and custom apps, is scalable for crowdsourcing measurements on a large scale and provides detailed data (throughput, latency, signal strength, etc.) on actual deployments. Our main conclusions based on the measurements are (i) optimized 4G networks in mid-band are comparable in both throughput and latency to current deployments of 5G (both standalone (SA) and non-standalone (NSA)) and (ii) mmWave 5G, even in NSA mode, can deliver multi-Gbps throughput reliably if the installation is dense enough, but performance is still brittle due to the propagation limitations imposed by distance and body-loss. Thus, while 5G demonstrates significant early promise, further work needs to be done to ensure that the stated goals of 5G are met.

Optical fibre links for distributing optical frequencies and time stamps were researched and experimentally tested in the past fifteen years. They have been used mainly for stability comparison of experimental optical clocks. But recent development puts demands on a technology transfer from laboratory experiments to the real industry. The remote calibration of interrogators of Fibre Bragg Grating strain sensory networks is one of important examples. The first step of the adoption the time and frequency broadcasting should be the drop-out free long-term operation of this technology between research laboratories connected via long-haul fibre links. We present a 306 km long-haul optical fibre link between the cities of Prague and Brno in the Czech Republic where a coherent transfer of stable optical frequency and a stable time signal has been firstly demonstrated. The link between ISI CAS Brno and CESNET Prague uses an internet communication fibre where a window of 1540-1546 nm is dedicated for the coherent transfer and 1PPS signal. The link is equipped with 6 bidirectional EDFA amplifiers. The optical frequency standard based on the highly-coherent laser Koheras Adjustik working at 1540.5 nm and stabilized with a saturation absorption spectroscopy technique was used for the coherent wave transfer. The suppression of the Doppler shift induced by the optical fibre was based on an accoustooptical modulator with a servo-loop including a fast PID controller processing the beat-note frequency given by mixing of the Adjustik laser (Brno) and the reflected frequency of this laser from the far end of 306 km long-haul fibre link (Prague). We verified the Doppler shift suppression for the coherent wave with a measuring method analysing the transport delay of the 1PPS signal.