Citizens Broadband Radio Service Research Articles

Independent Calculation of Move Lists for Incumbent Protection in a Multi-SAS Shared Spectrum Environment.

In the 3.5 GHz Citizens Broadband Radio Service (CBRS), secondary users are managed by spectrum access systems (SASs) to protect incumbents from interference. Current practice requires each SAS to exchange detailed user information with other SASs, and to use a common algorithm to suspend transmissions so that an aggregate interference percentile is below a predefined threshold. We propose a simplified method that utilizes a tight bound on the aggregate interference distribution. Simulation results show that the proposed approach trades off a marginal reduction in spectral efficiency to greatly simplify incumbent protection procedure, allowing each SAS to independently manage its users.

Tiered Spectrum Measurement Markets for Joint Licensed and Unlicensed Secondary Access

We consider a three-tier spectrum sharing framework, recently adopted in the United States for the Citizens Broadband Radio Service, which enables commercial users to share this spectrum with the incumbent users. This sharing can be further assisted by environmental sensing capability operators (ESCs) that monitor the spectrum occupancy to determine when the incumbents are absent. Two key aspects of this framework that impact how spectrum access firms (SAs) using this spectrum may compete are the differences in information provided by different ESCs and how different firms bundle their services using the licensed and unlicensed band. We show that if the SAs tend to use the unlicensed band more, they will prefer to obtain information from different ESCs. On the other hand, if one of the SAs uses the licensed band more, both the SAs tend to obtain information from the same ESC. If both the SAs tend to differ more in accessing the unlicensed bandwidth, they tend to obtain information from the same ESC more. Our analysis reveals that regulation is required if there is a single ESC, as the unlicensed spectrum may be unused if the user's valuation is high.

Performance Impact of Coexistence Groups in a GAA-GAA Coexistence Scheme in the CBRS Band

The General Authorized Access (GAA) users in the Citizens Broadband Radio Service (CBRS) band are the lowest priority users. They must make sure that they do not cause harmful interference to the higher tier users while cooperating with each other to minimize potential interference among themselves. Thus, efficient GAA coexistence scheme is essential for the operation of GAA users and to obtain high spectrum utilization. Towards this goal, the Wireless Innovation Forum (WInnForum) has recommended three schemes to facilitate GAA-GAA coexistence. We had reported a performance study of one of these schemes (called Approach 1), but that study did not have any Coexistence Group (CxG). A CxG is responsible for managing interference among its CBRS devices (CBSDs). In this paper, we study the performance of Approach 1 without CxGs as well as with different number of CxGs, in various configurations. We conduct our study around two locations in the USA using actual terrain and land cover data of the continental USA. We evaluate performance of the scheme at different deployment densities, using different propagation models at those two locations with different number of CxGs. We provide some interesting insights into the costs and benefits of having CxGs in the deployment.

High gain cylindrical dielectric resonator integrated with horn for multiband wireless applications

In this article, a multiband high gain cylindrical dielectric resonator (CDR) integrated with conical horn antenna is reported. This antenna has been designed for multiband wireless frequency applications. To enhance the gain, modified conical-shaped horn is integrated to the CDR. The proposed antenna resonates at 2.3, 3.5, 3.9, 7.5, 9.2, and 9.95 GHz, respectively. Antenna attains measured 14.1 dBi peak gain at 10.7 GHz resonant frequency. In all the frequency bands, antenna offers more than 80% radiation efficiency. Simulated and experimental results show a commendable agreement. This antenna covers LTE services, Citizens Broadband Radio Service, WiMAX, vehicular communication, cellular communication, and radar applications.

Incumbent Informing Capability (IIC) for Time-Based Spectrum Sharing

As the President's principal advisor on the regulation of the telecommunications industry, and policies relating to the Nation's economic and technological advancement, the National Telecommunications and Information Administration (NTIA), U.S. Department of Commerce programs and policymaking focus largely on protecting federal spectrum-based capabilities while expanding the availability of spectrum for all users. Managing core federal spectrum programs effectively and efficiently, identifying innovative approaches to increase spectrum access and sharing opportunities, and ensuring that the Internet remains an engine for continued economic growth, which promotes a 21st century Internet economy and expands broadband Internet access in America are a driving force for NTIA policy decisions. A key pillar of this policy is to increase spectrum access for all users through improved cooperation and collaboration between Federal and non-Federal spectrum stakeholders. This paper describes an Incumbent Informing Capability (IIC) for Time-Based Sharing, an innovative way to collaboratively, securely, and dynamically increase opportunistic spectrum access within spectrum allocations principally used by the federal government. The IIC is a mechanism for more reliably informing “new entrants” in a shared spectrum band when incumbent federal systems are operating in close proximity and thus need to be protected. New entrant access to the spectrum would be controlled through an enhanced, near-real-time Spectrum Coordination System (SCS). The IIC could replace extra layers of sharing techniques such as the environmental sensing capability (ESC), which presently is required by the Federal Communications Commission (FCC) for the Citizen Broadband Radio Service (CBRS) in the 3550-3700 MHz band. IIC has several potential benefits including support for mid-band spectrum sharing, reduced dependence on environmental sensing, more secure and reliable operations, and improved incumbent control of real-time spectrum usage information. Mid-band spectrum (between 1 GHz and 10 GHz) is valuable for broadband mobile wireless (e.g., 5G) communications because of its favorable propagation characteristics combined with potential for large individual channel bandwidth. This paper describes the concept for the IIC solution including operational needs and proposed business processes. It outlines how the IIC could be employed to enable spectrum sharing in the CBRS 3550-3650 MHz band and the 3450–3550 MHz band with potential for application to other bands in the future. Successful implementation of IIC will require interdisciplinary collaboration across institutions to apply AI/machine learning, secure distributed processing and data storage, and automated aggregate interference analysis. We expect the capability to evolve over time toward a dynamic spectrum sharing paradigm in selected bands where “everyone informs”, building on work demonstrated in the DARPA Spectrum Collaboration Challenge (SC2) that can more fully optimize the use of spectrum. The work is relevant to US global leadership in 5G and beyond, inspiring innovation and further research into advanced dynamic spectrum sharing.

Analysis of the On-Demand Spectrum Access Architecture for CBRS Cognitive Radio Networks

An on-demand spectrum access cognitive radio network offers spectrum services to users, so that users can dynamically set up application-oriented virtual topologies to support user applications. In this paper, we develop a mathematical model for the on-demand spectrum access architecture for cognitive radio networks based on the citizens broadband radio service (CBRS). The model can be used to estimate the blocking probability of spectrum demands from priority access license users, the network capacity, and the number of free spectrum bands available for lower priority general authorized access users. The performance evaluation indicates that the results from the mathematical model match simulation results well, which validates the accuracy of our model.

Enabling a “Use-or-Share” Framework for PAL–GAA Sharing in CBRS Networks via Reinforcement Learning

By implementing reinforcement learning-aided listen-before-talk (LBT) schemes over a citizens broadband radio service (CBRS) network, we increase the spatial reuse at secondary nodes while minimizing the interference footprint on higher-tier nodes. The federal communications commission encourages “use-or-share” policies in the CBRS band across the priority access license (PAL)–general authorized access (GAA) priority tiers by opportunistically allowing the lower-priority GAA nodes to access unused higher-priority PAL spectrum. However, there is currently no mechanism to enable this cross-tier spectrum sharing. In this paper, we propose and evaluate LBT schemes that allow opportunistic access to PAL spectrum. We find that by allowing LBT in a two carrier, two eNB scenario, we see upward of 50% user perceived throughput (UPT) gains for both eNBs. Furthermore, we examine the use of ${Q}$ -learning to adapt the energy-detection threshold (EDT), combating problematic topologies, such as hidden and exposed nodes. With merely a 4% reduction in primary node UPT, we see up to 350% gains in average secondary node UPT when adapting the EDT of opportunistically transmitting nodes.

Communication-Free Inter-Operator Interference Management in Shared Spectrum Small Cell Networks

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.

Deep Learning Classification of 3.5 GHz Band Spectrograms with Applications to Spectrum Sensing.

In the United States, the Federal Communications Commission has adopted rules permitting commercial wireless networks to share spectrum with federal incumbents in the 3.5 GHz Citizens Broadband Radio Service band. These rules require commercial systems to vacate the band when sensors detect radars operated by the U.S. military; a key example being the SPN-43 air traffic control radar. Such sensors require highly-accurate detection algorithms to meet their operating requirements. In this paper, using a library of over 14,000 3.5 GHz band spectrograms collected by a recent measurement campaign, we investigate the performance of thirteen methods for SPN-43 radar detection. Namely, we compare classical methods from signal detection theory and machine learning to several deep learning architectures. We demonstrate that machine learning algorithms appreciably outperform classical signal detection methods. Specifically, we find that a three-layer convolutional neural network offers a superior tradeoff between accuracy and computational complexity. Last, we apply this three-layer network to generate descriptive statistics for the full 3.5 GHz spectrogram library. Our findings highlight potential weaknesses of classical methods and strengths of modern machine learning algorithms for radar detection in the 3.5 GHz band.

GreenLoading: Using the citizens band radio for energy-efficient offloading of shared interests

Cellular networks are susceptible to being severely capacity-constrained during peak traffic hours or at special events such as sports and concerts. Many other applications are emerging for LTE and 5G networks that inject machine-to-machine (M2M) communications for Internet of Things (IoT) devices that sense the environment and react to diurnal patterns observed. Both for users and devices, the high congestion levels frequently lead to numerous retransmissions and severe battery depletion. However, there are frequently social cues that could be gleaned from interactions from websites and social networks of shared interest to a particular region at a particular time. Cellular network operators have sought to address these high levels of fluctuations and traffic burstiness via the use of offloading to unlicensed bands, which may be instructed by these social cues. In this paper, we leverage shared interest information in a given area to conserve power via the use of offloading to the emerging Citizens Broadband Radio Service (CBRS). Our GreenLoading framework enables hierarchical data delivery to significantly reduce power consumption and user fairness variation and includes a Broker Priority Assignment (BPA) algorithm to select data brokers for users. With the use of in-field measurements and web-based Google data across four diverse U.S. cities, we show an order of magnitude power savings via GreenLoading over a 24-hour period, on average, and power savings up to 97% at peak traffic times. Finally, we consider the role that a relaxation of wait times can play in the power efficiency of a GreenLoading network.

Coordinated Spectrum Allocation and Coexistence Management in CBRS-SAS Wireless Networks

Since the introduction of the idea of cognitive radio, various approaches towards spectrum sharing have been considered, for example, the Licensed Shared Access (LSA), which is considered in Europe, or Citizens Broadband Radio Service (CBRS) with Spectrum Access System (SAS) regulated by the US. This paper deals with the problem of coordinated resource allocation among a set of available base stations. A detailed definition of the problem is provided, followed by a discussion on a set of heuristics proposed for solving the problem. Four solutions are presented that are based on existing standards as well as on the approaches described in the literature. Next, new multi-selection (multi-choice) algorithm is proposed and discussed in detail. The main problem is divided in two subproblems, which are solved by using graph theorem and analytical description. The performance of the proposed solutions is analyzed in various scenarios. Finally, a trade-off between power allocation and frequency use is provided. All challenges identified during the investigation of the problem are presented.

Resource Allocation in Moving and Fixed General Authorized Access Users in Spectrum Access System

Spectrum access system (SAS) is a spectrum sharing framework proposed to share the spectrum between the incumbent users and the citizen broadband radio service devices, i.e. Priority access users and general authorized access (GAA) users. In this paper, we propose an interfering angle based method for the joint resource (channel and transmit power) allocation problem to the mobile and fixed GAA users. With mobile GAA users, the set of GAA users that can hear each other will change at different time instants making the resource allocation problem more challenging. The resource allocation of fixed and mobile GAA users is done considering coexistence with priority users, as well as coexistence between mobile and fixed GAA users. For the conflict-free resource allocation to fixed and mobile GAA users, we propose to use the maximum allowed transmit power for the beams of fixed GAA users that lie within the interference range of mobile GAA users. The simulation results show improved capacity from our proposed method while satisfying a predetermined interference constraint.

Spectrum Management Application for Virtualized Wireless Vehicular Networks: A Step Toward Programmable Spectrum Management in Future Wireless Networks

Spectrum management is a key challenge in the domain of wireless network virtualization. An efficient tool is needed to support dynamic, yet policy-compliant allocation of the frequency resources in virtual networks. In this article, we discuss the idea of a spectrum management application (SMA) as a tool for solving this technoeconomic issue in virtualized networks. The generic idea is exemplified in the application of the Citizen Broadband Radio Service (CBRS) model for spectrum sharing, and it has been tested in field trials with real operating networks. The results of this study show that the fully automated allocation of frequency resources, following the rules provided by the SMA, may be used for better spectrum utilization, while preserving the quality of all managed networks. This result may be treated as an important step toward efficient network management in a virtualized wireless networks.

Online Algorithm for Leasing Wireless Channels in a Three-Tier Spectrum Sharing Framework

The three-tier spectrum sharing framework (3-TSF) is a spectrum sharing model adopted by the Federal Communications Commission. According to this model, under-utilized federal spectrum like the Citizens Broadband Radio Service band is released for shared use where the highest preference is given to Tier-1 followed by Tier-2 (T2) and then Tier-3 (T3). In this paper, we study how a wireless operator, who is interested in maximizing its profit, can strategically operate as a T2 and/or a T3 user. T2 is characterized by paid but ”almost” guaranteed and interference-free channel access while T3 access is free but has the lesser guarantee and also faces channel interference. So the operator has to optimally decide between paid but better channel quality and free but uncertain channel quality. Also, the operator has to make these decisions without knowing future market variables like customer demand or channel availability. The main contribution of this paper is a deterministic online algorithm for leasing channels that has finite competitive ratio, low time complexity, and that does not rely on the knowledge of market statistics. Such algorithms are desirable in the early stages of the deployment of 3-TSF because the knowledge of market statistics may be rather inaccurate. We use tools from the ski-rental literature to design the online algorithm. The online optimization problem for leasing channels is a novel generalization of the ski-rental problem. We, therefore, make fundamental contributions to the ski-rental literature, the applications of which extend beyond this paper. We also conduct simulations using synthetic traces to compare our online algorithm with the benchmark and state-of-the-art algorithms.

Reduced-Power Almost Black Subframe Based Pulse Radar Spectrum Sharing for LTE System

Cochannel pulse radar and long term evolution (LTE) deployments are considered by the FCC citizen broadband radio service (CBRS) and also 5G spectrum sharing. This paper proposes a radar spectrum sharing method based on LTE reduced-power almost blank subframe (RP-ABS) mechanism, which is used to mitigate interference to pulse radar while maintaining high LTE throughput. For LTE, payload bits are first packed into nonradar interfered time domain subframes (SFs), and then RP-ABS or even zero-power almost blank subframe (ABS) are adopted in the rest SFs. For pulse radar, target detection performance is guaranteed, thanks to the decreased interference caused by LTE RP-ABS power. We also formulate and solve an optimization problem for radar and RP-ABS-based LTE spectrum sharing, which consider tradeoffs between RP-ABS-based LTE performance (bit error rate and throughput) and radar detection probability concurrently. Using 3rd generation partnership project (3GPP) LTE sensitivity test as a benchmark, 28.83% throughput gain can be obtained for RP-ABS-based method. A hardware-in-the-loop testbed is also designed to prove spectrum sharing between RP-ABS-based LTE and radar viable.

Modelling the Impact of Spectrum Sharing on Spectrum Value: The US Citizen Broadband Radio Service Ecosystem

In 2015, the US Federal Communications Commission released a Report and Order to enhance the availability of spectrum across the nation with a particular focus on wireless broadband services.The decision consisted of designating the 3.5 GHz band (3550 to 3700 MHz) as a three-tiered spectrum sharing space, knows as Citizens Broadband Radio Service (CBRS). The tiers are occupied by incumbent users in the upper tier (mainly federal aeronautical uses and non-federal fixed satellite services and terrestrial wireless operations), new entities known as Priority Access Licensees (PALs) on the middle tier, and a non-licensed access mode called General Authorised Access (GAA) on the bottom tier. Fast, and seemingly chaotic, technological progress and the pressing interests from stakeholders demand a closer, sharper consideration of an integral approach to determining the value of the spectrum. The assumptions in this paper rely strongly on stating that the goal of efficient spectrum management is to maximize the social and economic value of spectrum subject to conditions and constraints set by policy makers, possible via a spectrum authority. The proposed US 3.5 GHz ecosystem, or CBRS, provides a rich structure that allows for an assessment of spectrum value distribution among the ecosystem actors and uses. Building upon recent work in the UK that proposes three components for spectrum value, namely private use value, private external use value, and broad social value, our paper presents and discusses a descriptive model of spectrum value aimed to investigate the effects of spectrum sharing on the value of spectrum perceived by the players sharing the band. The short story of utilization of the upper part of the 3.5 GHz band by Wireless Interent Service Providers, or WISPs, in the US, and the spectrum regulatory changes occurred over the last 10 years are used to exemplify the complex arrangements that need to be considered in order to assess the value of spectrum. The case reveals the importance of using the above mentioned three components of value. The fact that no definitive clear boundaries can be defined between the value components adds to the complex task of assessing how valuable spectrum is and how changes to permitted uses affect its value. Currently divergent interests clash over what pathway to regulatory conditions must be adopted for tier-2 PALs. The struggle centers on the license terms and auction conditions. Currently PALs would be allocated via an auction in census tract areas if there is enough competition; upon assignment, a PAL would get 3-year licenses with no assurance for renewal. Big telecommunications companies, thirsty for more spectrum capacity for 5G services, want longer terms with assurance of renewal, a change from census tracts to larger “Partial Economic Areas”, and the abolition of “enough competition” for PAL assignment so that even when there is only one license seeker, the FCC will have to grant a license. In a new notice of consultation the FCC is also considering hybrid solutions that might allow combinations of such competing terms to apply to different geographical areas. Our model of value allows us to understand not only how value is distributed across the CBRS but also how the proposed changes may affect such distribution, hence the social and economic goals expected from the 3.5 GHz ecosystem.

국내 주파수 공동사용 활성화를 위한 정책 도입방안 연구

Herein, we survey the current state of the recent legal revision of the Citizens Broadband Radio Service, a type of city spectrum-sharing service used in the United States of America, and the introduction of spectrum sharing in the frequency ranging from 3.8～4.2 GHz, based on the United Kingdom framework for spectrum sharing. Specifically, the subjects of topical interest, including the radio station licensing of the spectrum-sharing service system face-to-face multitier user structure, regional frequency allocation, and applicable service types, are discussed. Furthermore, factors to be considered while selecting candidate channels for joint use are suggested, emphasizing their importance for introducing spectrum sharing in Korea and revitalizing the related industrial sectors. In addition, methods of introducing a radio station license system for spectrum sharing, techniques of introducing incentive auctions, and the types of services where spectrum sharing is applicable are discussed.

Debating a New Regulatory Framework for Radio Spectrum: Citizens Broadband Radio Service

The FCC has billed 3.5 GHz as the “innovation band,” with the idea that “regulatory adaptability should make the 3.5 GHz band hospitable to a wide variety of users, deployment models, and business cases, including some solutions to market needs not adequately served by our conventional licensed or unlicensed rules.” Whether the FCC can align the goals of access by a wide range of stakeholders and allocative efficiency will depend on the specifics of the rules concerning geographic license areas and license terms.

RF Dataset of Incumbent Radar Signals in the 3.5 GHz CBRS Band.

This Radio Frequency (RF) dataset consists of synthetically generated waveforms of incumbent 3.5GHz radar systems. The intended use of the dataset is for developing and evaluating detectors for the 3.5GHz Citizens Broadband Radio Service (CBRS) \cite{cbrs} or similar bands where the primary users of the band are Federal radar systems. The dataset can be used for developing and testing radar detection algorithms using machine learning/deep learning techniques. The algorithm aims to detect whether the radar signal is present or absent regardless of the signal type. The target signals have a variety of modulation types and parameters chosen from wide ranges. In addition, the start time and the center frequency of the radar signals are randomized in the waveform. The variety of signals and their random parameters makes the detection problem more challenging when using non-naive (e.g., energy detector is a naive signal detector) classical signal processing techniques.

Licensed Shared Access evolution enables early access to 5G spectrum and novel use cases

This paper discusses the regulatory and standardization status of the Licensed Shared Access (LSA), compares it with the US Citizens Broadband Radio Service concept, and reviews results from the ongoing feasibility study in the European Telecommunications Standards Institute on temporary spectrum ac