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A Survey on Cellular-connected UAVs: Design Challenges, Enabling 5G/B5G Innovations, and Experimental Advancements

Debashisha Mishra, Enrico Natalizio

arXiv:2005.00781v1cs.NIeess.SP

TL;DR

Cellular-connected UAVs require wireless connectivity that accommodates their mobility, autonomous operation, mission-specific requirements, and integration challenges. This survey examines UAVs as aerial UEs in 5G/B5G networks, covering architectures, technological synergies, experiments, standardization, and open problems. It concludes that 5G/B5G innovations and softwarized, cloudified architectures address scalability and performance limitations, while adoption also requires attention to nontechnical constraints and unresolved channel and energy issues.

  • Problem

    Reliable, secure, and scalable cellular networking for autonomous UAV missions remains challenging because mobility, mission requirements, and multi-UAV coordination impose tightly coupled networking demands.

  • Method

    The survey analyzes cellular-connected UAVs as aerial UEs in 5G/B5G systems through taxonomies, integration challenges, network architectures, physical-layer innovations, experiments, field trials, and standardization efforts.

  • Results

    5G/B5G innovations complement cellular-connected UAV operation, while softwarized and cloudified architectures address practical performance and scalability limitations.

  • Takeaways & Limitations

    Successful cellular-connected UAV adoption must combine technical solutions with privacy, security, licensing, public-safety, administrative, and standardization considerations.

  • Takeaways & Limitations

    Accurate channel modeling across diverse deployment environments remains largely unexplored, and most existing studies do not adequately factor UAV energy limitations.

Abstract

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As an emerging field of aerial robotics, Unmanned Aerial Vehicles (UAVs) have gained significant research interest within the wireless networking research community. As soon as national legislations allow UAVs to fly autonomously, we will see swarms of UAV populating the sky of our smart cities to accomplish different missions: parcel delivery, infrastructure monitoring, event filming, surveillance, tracking, etc. The UAV ecosystem can benefit from existing 5G/B5G cellular networks, which can be exploited in different ways to enhance UAV communications. Because of the inherent characteristics of UAV pertaining to flexible mobility in 3D space, autonomous operation and intelligent placement, these smart devices cater to wide range of wireless applications and use cases. This work aims at presenting an in-depth exploration of integration synergies between 5G/B5G cellular systems and UAV technology, where the UAV is integrated as a new aerial User Equipment (UE) to existing cellular networks. In this integration, the UAVs perform the role of flying users within cellular coverage, thus they are termed as cellular-connected UAVs (a.k.a. UAV-UE, drone-UE, 5G-connected drone, or aerial user). The main focus of this work is to present an extensive study of integration challenges along with key 5G/B5G technological innovations and ongoing efforts in design prototyping and field trials corroborating cellular-connected UAVs. This study highlights recent progress updates with respect to 3GPP standardization and emphasizes socio-economic concerns that must be accounted before successful adoption of this promising technology. Various open problems paving the path to future research opportunities are also discussed.

1. Introduction

UAVs’ mobility, autonomy, and flexible deployment create broad application potential but require reliable wireless connectivity and introduce integration challenges. The paper distinguishes three cellular-network integration paradigms and prioritizes cellular-connected UAVs, where drones operate as aerial UEs.

  • UAV capabilities and motivation: UAVs’ three-dimensional mobility, autonomous operation, and flexible deployment support applications across civil, safety, industrial, security, and environmental domains.Their wireless connectivity must support diverse use cases and seamless service.
  • Research motivation: The paper identifies wireless-platform integration and the resulting scientific and technological challenges as its two central research directions.It examines these issues from an aerial-networking perspective.
  • 5G/B5G opportunity: 5G/B5G networks offer UAVs wide-area, secure, and reliable licensed connectivity, with targets including approximately 10 Gbits/s transmission and 1 ms round-trip latency.These capabilities support beyond-visual-line-of-sight operation and diverse UAV applications.
  • UAV communication requirements: UAV communication comprises low-rate, highly reliable Control and Non-Payload Communication and high-rate Payload Communication such as real-time video.CNPC supports navigation, telemetry, waypoint updates, and air-traffic-control updates, while payload links carry mission information.
  • Integration paradigms: Cellular integration spans UAV-assisted cellular communication, cellular-assisted UAV communication, and direct UAV-UAV communication.The paper focuses on cellular-assisted UAVs, in which drones act as aerial UEs coexisting with terrestrial UEs and access cellular infrastructure from the sky.

2. Related surveys and tutorials

The survey addresses a gap in prior UAV-cellular literature by focusing solely on cellular-connected UAVs and providing a unified view of their research developments, challenges, technologies, experiments, and adoption issues.

  • Related literature: Existing surveys mainly examine UAV-assisted cellular communication or isolated challenges, leaving cellular-connected UAV research fragmented.The paper identifies limited holistic coverage of the cellular-connected UAV paradigm.
  • Survey scope: The survey covers applications, communication requirements, integration challenges, 5G/B5G architectures and physical-layer improvements for UAVs as aerial users.Its scope includes virtualization, softwarization, slicing, and other enabling technologies.
  • Experimental advances: It reviews experimental testbeds, field trials, measurement campaigns, and prototyping efforts to connect theoretical analysis with realistic cellular-connected UAV deployments.The survey also outlines features for an ideal experimental prototype.
  • Adoption and future directions: The work discusses ongoing standardization, regulatory frameworks, market and socio-economic issues that affect successful and widespread adoption.These topics are presented alongside future research opportunities.

3. Taxonomy of UAV Applications and Use cases

Cellular-connected UAVs support diverse application domains, including observation, disaster response, infrastructure, industrial, and immersive-media use cases, with missions shaped by their mobility, sensing, and communication capabilities.

  • Earth and atmospheric observations: UAVs gather real-time geophysical and atmospheric measurements autonomously, supporting observation of hazards, environmental conditions, and abnormal processes.Their sensors and defined flight trajectories enable data acquisition across geophysical and atmospheric applications.
  • Disaster management: During disasters, UAVs provide situational awareness, early warnings, and movement information while helping responders assess damage and restore connectivity.The first 48 to 72 hours are identified as crucial for mitigation and recovery.
  • Civil infrastructure and logistics: UAVs support public infrastructure through surveillance, land surveying, worker tracking, construction, demolition, and faster, cost-effective delivery services.These applications include highways, railways, construction sites, and logistics operations.
  • Industrial IoT platforms (IIoT): Industrial IoT applications use UAVs to inspect hazardous or inaccessible sites and collect sensor data for real-time communication with industrial control stations.This reduces reliance on manual inspection in challenging environments.
  • AR/VR applications: AR/VR-enabled UAVs provide high-altitude video, aerial photography, virtual tours, and real-estate visualization experiences.These applications extend UAV use into immersive media and enterprise markets.
  • Cellular-connected operation: Cellular-connected UAVs operate as aerial UEs exchanging control and payload data with ground infrastructure, while cellular networking supports applications such as observation, surveillance, and industrial IoT.The survey positions cellular integration as a common communication basis across varied missions.

4. Integration Challenges of UAVs over 5G

Cellular-connected UAVs require adaptations to terrestrial networks because aerial users experience distinct coverage, interference, and propagation conditions. The section surveys 3D channel and coverage models alongside coexistence challenges between aerial and ground users.

  • Cellular Integration Motivation: Cellular connectivity offers UAVs cost-effective, low-latency, high-throughput, scheduled, robust, secure, and reliable communication services.The section presents existing cellular infrastructure as an alternative to costly dedicated UAV spectrum and satellite links.
  • Coverage and Antenna Patterns: 3D coverage is necessary because terrestrial base stations are down-tilted for ground users, while UAVs typically fly above antenna height.Antenna down-tilt reduces gains toward aerial users and affects uplink and downlink coverage probabilities.
  • Interference Management: Higher-altitude UAVs create dominant line-of-sight links to multiple base stations, increasing interference and complicating existing interference-management mechanisms.Conventional ICIC approaches may fail because UAV interference involves many base stations and higher coordination complexity.
  • Channel Modeling: UAV channel models must account for G2U and U2G links, with LoS-sensitive fading and propagation conditions varying across rural, suburban, and urban environments.Free-space, altitude/angle-dependent, and probabilistic LoS models address different deployment and blockage conditions.
  • Channel Modeling: 3GPP models LoS probability using terrestrial assumptions below H_low, a distance- and altitude-dependent function between H_low and H_high, and 100% LoS above H_high.The model covers UMi, UMa, and RMa deployment scenarios and uses UAV-height-dependent parameters l_1 and p_1.

4.3. System Operations & Mobility

UAV mobility changes cell association, handover behavior, and trajectory planning because flight altitude, speed, and connectivity constraints vary in three dimensions. The section highlights frequent handovers and communication-aware routes as central operational concerns.

  • Handover Management: At 150 m altitude, UAVs experience 5 handovers per minute, compared with one handover per minute for the ground-user reference scenario.UAVs are also prone to frequent and ping-pong handovers, with handover frequency increasing at higher altitude.
  • Handover Management: UAVs need enhanced cell selection and handover solutions that support changing altitudes and three-dimensional mobility.Terrestrial RSRP-based decisions are less suitable because aerial users receive signals from multiple base-station side lobes.
  • Trajectory Optimization: Communication-aware trajectory design may require curved rather than distance-optimal routes to preserve persistent cellular connectivity.Poor rural coverage and mmWave path loss or blockage can interrupt connections during a mission.
  • Trajectory Optimization: If a trajectory’s connectivity discontinuity exceeds the acceptable tolerance, the UAV may fail to accomplish its mission.Trajectory optimization therefore incorporates discontinuity thresholds alongside distance and mission requirements.
  • Trajectory Optimization: With a zero discontinuity threshold, the optimized trajectory stays within cellular coverage, whereas a 15-time-unit threshold produces a nearly straight distance-oriented path.The same threshold-dependent behavior is reported for two different cellular layouts.

4.5. Security Challenges

Cellular-connected UAVs face cyber-physical risks because their sensors, payloads, control systems, and cooperative missions expose them to attacks. The section surveys application-specific threats and emphasizes protection, regulation, and further technical investigation.

  • Threat Landscape: Attackers may steal, misuse, or control UAV payloads by compromising communication and control systems or reprogramming flight behavior.The section identifies cyber-physical attacks as a concern for sensor-equipped UAVs performing sensitive missions.
  • Protection and Open Needs: Secure cellular-connected UAV operation requires protection methodologies, intrusion-detection mechanisms, operator guidelines, and regulations.The surveyed work includes ANN-based security approaches and identifies areas needing attention for UAV intrusion detection systems.
  • Application-Specific Threats: Delivery UAVs can have goods or physical assets destroyed, stolen, or delayed after malicious takeover or physical attack.The risk includes both the transported package and the UAV itself.
  • Application-Specific Threats: Real-time multimedia UAVs face identity manipulation and disrupted transmissions, while centralized processing can impose delay and computational burden at scale.These risks affect delivery of video, VR, and tracking information to the control station.
  • Application-Specific Threats: In UAV-enabled intelligent transportation systems, unidentified swarm members can steal information or disrupt UAV-to-UAV communication and mission safety.Such attacks can include forced self-collision within cooperative UAV operations.

5. Synergies of 5G/B5G innovations for Cellular-connected UAVs

Cellular-connected UAVs are remotely managed through networks that must support diverse missions, coordinated multi-UAV communication, and reconfigurable architectures. 5G/B5G virtualization and programmable networking provide the envisioned architectural foundations.

  • System Requirements: Cellular-connected UAVs are remotely controlled by a Ground Control Station, and their networking requirements depend on mission and hardware characteristics.Multi-UAV systems additionally require reliable, secure communication and efficient reconfigurable network architectures.
  • 5G/B5G Architectural Synergies: 5G/B5G architectures contribute SDN, NFV, SFC, network slicing, and physical-layer improvements to cellular-connected UAV applications.These innovations support cloudification, virtualization, softwarization, and programmable network functions.

5.1. Network Architectures

The survey groups cellular-connected UAV architectures by key 5G networking enablers, including NFV, MEC, IoT, and service-oriented designs. These approaches address UAV resource constraints, mission-specific deployment, computation offloading, and application services.

  • Cellular-connected UAV architectures are categorized as NFV-, MEC-, IoT-, and service-oriented designs.
  • NFV Oriented Architectures: NFV enables agile, automated, and reconfigurable UAV deployment by installing mission-specific virtual network functions on UAV infrastructure.
  • MEC Oriented Architectures: MEC architectures offload computational tasks from resource-constrained UAVs to ground-station edge servers, including during trajectory optimization.
  • IoT Oriented Architectures: IoT-oriented architectures use UAV sensors, clustering, cellular connectivity, and analytics to support applications such as disaster mitigation and crowd surveillance.
  • Service Oriented Architectures: Service-oriented architectures provide reusable, rapidly configurable mission services by decomposing UAV functionality into smaller components.

5.2. Hardware and Physical layer consideration

The survey reviews 5G physical-layer and access technologies relevant to cellular-connected UAVs, emphasizing high-rate, low-latency connectivity alongside aerial interference and beam-management challenges. Massive MIMO, mmWave, beamforming, and NOMA are presented as candidate techniques for improving aerial communication and coexistence.

  • 5G physical-layer candidates for cellular-connected UAVs include massive MIMO, mmWave communication, beamforming, BDMA, and new modulation schemes.
  • URLLC targets 1 ms latency and 99.999% reliability for applications such as beyond-visual-line-of-sight remote UAV piloting.
  • Massive MIMO: Massive MIMO can support aerial-ground coexistence, large uplink data rates, and consistent control-link behavior while restricting interference to terrestrial users.
  • mmWave Communication: mmWave offers high bandwidth but is vulnerable to blockage, requiring efficient beamforming and tracking; simulations report 1 Gbps throughput with sub-ms latency near the ground station.
  • Beamforming and Coexistence: Aerial mobility and line-of-sight conditions make beam grouping and interference mitigation challenging, while directional steering jointly optimized with flight paths can improve coexistence.
  • Multiple Access: NOMA with interference cancellation allows UAVs to reuse ground-user resource blocks by decoding stronger aerial signals before ground-user signals.

5.3. Summary of Lessons Learnt

The survey concludes that conventional cellular infrastructure does not scale well to diverse cellular-connected UAV use cases. 5G/B5G softwarization, cloudification, architectural innovations, and physical-layer enhancements improve scalability and support mission-specific communication demands.

  • Classical cellular infrastructures are not well scalable for the diverse and growing use cases of cellular-connected UAVs.
  • NFV, MEC, SOA, and IoT-driven architectures address practical performance and scalability limitations through softwarized and cloudified resources.
  • 5G/B5G hardware, NR, and UAV technology improvements accommodate application-specific latency, rate, and reliability demands.
  • Physical-layer enhancements further improve the effectiveness of cellular-connected UAV applications.

6. Design Trials and Prototyping

Design trials and field studies provide practical evidence about cellular-connected UAV performance, but existing prototypes remain specialized and incomplete. Results show useful LTE/5G connectivity and favorable aerial propagation in some conditions, alongside interference, handover, coverage, and reliability limitations.

  • Existing work lacks a complete real-world testbed characterizing all cellular-connected UAV challenges and benefits, with prototypes differing by objectives, features, and platforms.
  • Experimental Testbeds: An open-source 4G prototype used commercial off-the-shelf hardware and software, demonstrated more than one hour of flight, and provided detailed build guidance.
  • Experimental Testbeds: LTE testing found sufficient bit rate, latency, and jitter for beyond-visual-line-of-sight UAV operation, although the prototype omitted several features.
  • Experimental Testbeds: The prototype design omitted coverage holes, fail-safe mechanisms, and coexistence penalties with ground UEs.
  • Field Trials: Higher altitude increases handovers and may force fallback from 5G to 4G, while LTE/5G deployments can provide several hundred Mbps downlink but limited uplink gains.
  • Field Trials: Aerial UEs can achieve stronger received signal strength and better uplink throughput than ground UEs, but experience lower SINR, stronger interference, and more radio link failures.
  • Field Trials: At 150 m altitude, measured UAV throughput averaged 20 Mbps downlink and 40 Mbps uplink, supporting many applications and use cases.

7. Standardization & Socio-economic Concerns

Cellular-connected UAV adoption requires coordinated standardization alongside technical, regulatory, privacy, safety, and socio-economic safeguards. 3GPP study items address aerial-user support, identification, tracking, and application-layer requirements, while unified operating rules remain incomplete.

  • Standardization: 3GPP study items and working groups address cellular-connected UAV technical, identification, tracking, and application-layer requirements.Release-15 examined LTE support, while later work includes remote identification, UAS connectivity, tracking, service requirements, and UAV-specific KPIs.
  • Standardization: Release-15 introduced enhanced radio events, height-dependent aerial-UE reporting, subscription-based identification, and improved mobility, interference detection, power control, and flight-path support.
  • Regulatory concerns: UAV regulation must control airspace use, flight limitations, and administrative privileges including licensing, authorization, and data handling.
  • Socio-economic concerns: Cellular-connected UAVs raise privacy, security, public-safety, licensing, and administrative challenges that require solutions beyond communications technology.Surveillance and sensor data can infringe privacy, while command-and-control discontinuities or malicious intrusion can endanger people, assets, and missions.
  • Regulatory concerns: A unified set of rules governing UAV operation over cellular spectrum across national and international airspace is still far away.
  • Socio-economic concerns: Commercial cellular-connected UAV production must match the true requirements and specifications of each use case to maximize its benefits.

8. Future Outlooks

Future research must address unresolved propagation, energy, security, mobility, and evaluation challenges for cellular-connected UAVs. The paper also identifies AI/ML and MEC as promising directions for autonomous operation and computational offloading.

  • 8.1. Accurate Channel Models: Accurate channel models remain largely unexplored across diverse deployment environments and must account for mmWave and massive-MIMO effects.Relevant settings include stadiums, urban, rural, suburban, industrial, over-water, and highway environments.
  • 8.2. Energy/Battery Power Limitations: Onboard energy is a bottleneck because flight, communication, software execution, and planning consume battery power, yet many studies omit this constraint.Energy-aware research is especially needed for UAV VNF deployment, trajectory optimization, learning-based methods, and mission longevity.
  • 8.3. Security and Privacy: Open communication links expose cellular-connected UAVs to control-signal spoofing, motivating security and privacy research across all protocol layers.Spoofing can cause confidential-information loss or mission failure and make recovery difficult.
  • 8.5. 3D Mobility and Handovers: UAVs served by base-station sidelobes experience distant cell selection and frequent handovers, requiring aerial-aware antennas, radio planning, and mobility mechanisms.Nearest- or strongest-RSRP selection may be unsuitable because blockage, mobility, and altitude variation shape handover behavior.
  • Experimental validation: Field trials and real-world testbeds are needed because simulations and measurement campaigns alone cannot fully characterize cellular-connected UAV performance.The paper notes a shortage of working prototypes and practical evaluation resources.
  • AI/ML and MEC: AI/ML and MEC offer research directions for autonomous UAV networking and offloading computationally intensive tasks to edge nodes.MEC can support tasks such as real-time face recognition while improving UAV endurance under limited onboard computation and energy.

9. Conclusions

The survey presents cellular-connected UAVs as aerial UEs integrated with existing 5G/B5G systems and organizes their architectures, innovations, deployment evidence, and adoption barriers. It concludes that technical, standardization, regulatory, and socio-economic issues must be considered together.

  • 9. Conclusions: The survey comprehensively examines cellular-connected UAVs as new aerial UEs integrated into existing 5G/B5G cellular systems.
  • 9. Conclusions: It covers network architectures, 5G/B5G physical-layer improvements, hardware and software design challenges, prototypes, field trials, simulations, and deployment issues.
  • 9. Conclusions: The survey also reviews 3GPP standardization, national and international regulations, and socio-economic barriers relevant to successful adoption.
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