6G Internet of Things: A Comprehensive Survey

The sixth generation (6G) wireless communication networks are envisioned to revolutionize customer services and applications via the Internet of Things (IoT) towards a future of fully intelligent and autonomous systems. In this article, we explore the emerging opportunities brought by 6G technologies in IoT networks and applications, by conducting a holistic survey on the convergence of 6G and IoT. We first shed light on some of the most fundamental 6G technologies that are expected to empower future IoT networks, including edge intelligence, reconfigurable intelligent surfaces, space-air-groundunderwater communications, Terahertz communications, massive ultra-reliable and low-latency communications, and blockchain. Particularly, compared to the other related survey papers, we provide an in-depth discussion of the roles of 6G in a wide range of prospective IoT applications via five key domains, namely Healthcare Internet of Things, Vehicular Internet of Things and Autonomous Driving, Unmanned Aerial Vehicles, Satellite Internet of Things, and Industrial Internet of Things. Finally, we highlight interesting research challenges and point out potential directions to spur further research in this promising area.

[1]  Sherali Zeadally,et al.  Energy-Efficient Fog Computing for 6G-Enabled Massive IoT: Recent Trends and Future Opportunities , 2022, IEEE Internet of Things Journal.

[2]  Ting Li,et al.  DRLR: A Deep-Reinforcement-Learning-Based Recruitment Scheme for Massive Data Collections in 6G-Based IoT Networks , 2022, IEEE Internet of Things Journal.

[3]  Halim Yanikomeroglu,et al.  Energy-Efficient RIS-Assisted Satellites for IoT Networks , 2021, IEEE Internet of Things Journal.

[4]  Jinchao Huang,et al.  Accurate Interpretation of the Online Learning Model for 6G-Enabled Internet of Things , 2021, IEEE Internet of Things Journal.

[5]  H. Huang,et al.  Full-Duplex Nonorthogonal Multiple Access With Layers-Based Optimized Mobile Relays Subsets Algorithm in B5G/6G Ubiquitous Networks , 2021, IEEE Internet of Things Journal.

[6]  Zhenyu Na,et al.  UAV-Supported Clustered NOMA for 6G-Enabled Internet of Things: Trajectory Planning and Resource Allocation , 2021, IEEE Internet of Things Journal.

[7]  Sudeep Tanwar,et al.  BATS: A Blockchain and AI-Empowered Drone-Assisted Telesurgery System Towards 6G , 2021, IEEE Transactions on Network Science and Engineering.

[8]  Yacine Ouzrout,et al.  Toward ML-Based Energy-Efficient Mechanism for 6G Enabled Industrial Network in Box Systems , 2021, IEEE Transactions on Industrial Informatics.

[9]  Hengtai Chang,et al.  A Novel Nonstationary 6G UAV-to-Ground Wireless Channel Model With 3-D Arbitrary Trajectory Changes , 2021, IEEE Internet of Things Journal.

[10]  Aruna Seneviratne,et al.  Federated Learning for Internet of Things: A Comprehensive Survey , 2021, IEEE Communications Surveys & Tutorials.

[11]  Mohammad Ayoub Khan,et al.  Energy-Efficient Resource Allocation Strategy in Massive IoT for Industrial 6G Applications , 2021, IEEE Internet of Things Journal.

[12]  Houbing Song,et al.  Big Data Analytics for 6G-Enabled Massive Internet of Things , 2021, IEEE Internet of Things Journal.

[13]  Ali Kashif Bashir,et al.  Energy-Efficient Random Access for LEO Satellite-Assisted 6G Internet of Remote Things , 2021, IEEE Internet of Things Journal.

[14]  Ali Hassan Sodhro,et al.  Toward 6G Architecture for Energy-Efficient Communication in IoT-Enabled Smart Automation Systems , 2021, IEEE Internet of Things Journal.

[15]  W. Feng,et al.  MEC-Empowered Non-Terrestrial Network for 6G Wide-Area Time-Sensitive Internet of Things , 2021, Engineering.

[16]  H. Poor,et al.  A Tutorial on Ultrareliable and Low-Latency Communications in 6G: Integrating Domain Knowledge Into Deep Learning , 2021, Proceedings of the IEEE.

[17]  Xin Jian,et al.  Blockchain-Empowered Trusted Networking for Unmanned Aerial Vehicles in the B5G Era , 2021, IEEE Network.

[18]  Kai Zhou,et al.  Optimization of Achievable Rate in the Multiuser Satellite IoT System With SWIPT and MEC , 2021, IEEE Transactions on Industrial Informatics.

[19]  Christian Wietfeld,et al.  Client-Based Intelligence for Resource Efficient Vehicular Big Data Transfer in Future 6G Networks , 2021, IEEE Transactions on Vehicular Technology.

[20]  Zhu Han,et al.  Reconfigurable Intelligent Surfaces in 6G: Reflective, Transmissive, or Both? , 2021, IEEE Communications Letters.

[21]  Zhihua Cui,et al.  A Many-Objective Optimization Based Intelligent Intrusion Detection Algorithm for Enhancing Security of Vehicular Networks in 6G , 2021, IEEE Transactions on Vehicular Technology.

[22]  Shuguang Cui,et al.  A Comprehensive Survey on 6G Networks: Applications, Core Services, Enabling Technologies, and Future Challenges , 2021, ArXiv.

[23]  Junjuan Xia,et al.  Battery-constrained Federated Edge Learning in UAV-enabled IoT for B5G/6G Networks , 2021, Phys. Commun..

[24]  Xin Liu,et al.  Spectrum Sharing for 6G Integrated Satellite-Terrestrial Communication Networks Based on NOMA and Cognitive Radio , 2021 .

[25]  Shuguang Cui,et al.  Federated Learning for 6G: Applications, Challenges, and Opportunities , 2021, Engineering.

[26]  Bin Han,et al.  The Road Towards 6G: A Comprehensive Survey , 2021, IEEE Open Journal of the Communications Society.

[27]  Jianhua He,et al.  Deep-Learning-Based Intelligent Intervehicle Distance Control for 6G-Enabled Cooperative Autonomous Driving , 2020, IEEE Internet of Things Journal.

[28]  Anandarup Mukherjee,et al.  Magnum: A Distributed Framework for Enabling Transfer Learning in B5G-Enabled Industrial IoT , 2020, IEEE Transactions on Industrial Informatics.

[29]  Erik G. Larsson,et al.  Towards 6G wireless communication networks: vision, enabling technologies, and new paradigm shifts , 2020, Science China Information Sciences.

[30]  Xiaohong Huang,et al.  Low-Latency Federated Learning and Blockchain for Edge Association in Digital Twin Empowered 6G Networks , 2020, IEEE Transactions on Industrial Informatics.

[31]  Wei Feng,et al.  5G Embraces Satellites for 6G Ubiquitous IoT: Basic Models for Integrated Satellite Terrestrial Networks , 2020, IEEE Internet of Things Journal.

[32]  Zhenyu Na,et al.  Collaborative Design of Multi-UAV Trajectory and Resource Scheduling for 6G-Enabled Internet of Things , 2020, IEEE Internet of Things Journal.

[33]  Kun Yang,et al.  6G Cellular Networks and Connected Autonomous Vehicles , 2020, IEEE Network.

[34]  Zhu Han,et al.  LEO-Satellite-Assisted UAV: Joint Trajectory and Data Collection for Internet of Remote Things in 6G Aerial Access Networks , 2020, IEEE Internet of Things Journal.

[35]  Caijun Zhong,et al.  Robust Design for NOMA-Based Multibeam LEO Satellite Internet of Things , 2020, IEEE Internet of Things Journal.

[36]  W. Feng,et al.  Cell-Free Satellite-UAV Networks for 6G Wide-Area Internet of Things , 2020, IEEE Journal on Selected Areas in Communications.

[37]  Ripon Patgiri,et al.  6G Communication Technology: A Vision on Intelligent Healthcare , 2020, Health Informatics.

[38]  Aruna Seneviratne,et al.  Blockchain and AI-Based Solutions to Combat Coronavirus (COVID-19)-Like Epidemics: A Survey , 2020, IEEE Access.

[39]  Chao Dong,et al.  UAVs as an Intelligent Service: Boosting Edge Intelligence for Air-Ground Integrated Networks , 2020, IEEE Network.

[40]  H. Vincent Poor,et al.  Enabling AI in Future Wireless Networks: A Data Life Cycle Perspective , 2020, IEEE Communications Surveys & Tutorials.

[41]  D. Niyato,et al.  Deep Reinforcement Learning Based Massive Access Management for Ultra-Reliable Low-Latency Communications , 2020, IEEE Transactions on Wireless Communications.

[42]  Jun Li,et al.  Privacy Preservation in Location-Based Services: A Novel Metric and Attack Model , 2018, IEEE Transactions on Mobile Computing.

[43]  Andrei Gurtov,et al.  The Roadmap to 6G Security and Privacy , 2021, IEEE Open Journal of the Communications Society.

[44]  D. Niyato,et al.  A Comprehensive Survey of 6G Wireless Communications , 2020, 2101.03889.

[45]  M. S. Kaiser,et al.  6G Access Network for Intelligent Internet of Healthcare Things: Opportunity, Challenges, and Research Directions , 2020, Advances in Intelligent Systems and Computing.

[46]  Yao Yuanyuan,et al.  An Improved Algorithm for Adaptive Communication Frame Length Based on Modbus Protocol , 2020, 2020 IEEE 6th International Conference on Computer and Communications (ICCC).

[47]  Dinh C. Nguyen,et al.  Blockchain and Edge Computing for Decentralized EMRs Sharing in Federated Healthcare , 2020, GLOBECOM 2020 - 2020 IEEE Global Communications Conference.

[48]  R. Glitho,et al.  ETSI Multi-Access Edge Computing for Dynamic Adaptive Streaming in Information Centric Networks , 2020, GLOBECOM 2020 - 2020 IEEE Global Communications Conference.

[49]  Shaohui Sun,et al.  System integration of terrestrial mobile communication and satellite communication —the trends, challenges and key technologies in B5G and 6G , 2020, China Communications.

[50]  Mohamed-Slim Alouini,et al.  The Potential of Multi-Layered Hierarchical Non-Terrestrial Networks for 6G , 2020, ArXiv.

[51]  Tao Sun.  Mining and utilization of special information for archives management based on 5G network and Internet of Things , 2020 .

[52]  M. Ylianttila,et al.  The role of 5G for digital healthcare against COVID-19 pandemic: Opportunities and challenges , 2020, ICT Express.

[53]  Yong Xiao,et al.  Towards Self-learning Edge Intelligence in 6G , 2020, ArXiv.

[54]  Shuangfeng Han,et al.  Artificial-Intelligence-Enabled Air Interface for 6G: Solutions, Challenges, and Standardization Impacts , 2020, IEEE Communications Magazine.

[55]  Antonios Tsourdos,et al.  Trustworthy Deep Learning in 6G-Enabled Mass Autonomy: From Concept to Quality-of-Trust Key Performance Indicators , 2020, IEEE Vehicular Technology Magazine.

[56]  Symeon Chatzinotas,et al.  Reconfigurable Intelligent Surfaces for Smart Cities: Research Challenges and Opportunities , 2020, IEEE Open Journal of the Communications Society.

[57]  Oscar Sanjuán Martínez,et al.  Blockchain based integrated security measure for reliable service delegation in 6G communication environment , 2020, Comput. Commun..

[58]  Zhu Han,et al.  6G Wireless Systems: A Vision, Architectural Elements, and Future Directions , 2020, IEEE Access.

[59]  Fadi Al-Turjman,et al.  Survival Study on Blockchain Based 6G-Enabled Mobile Edge Computation for IoT Automation , 2020, IEEE Access.

[60]  Tianqing Zhu,et al.  Security and privacy in 6G networks: New areas and new challenges , 2020, Digit. Commun. Networks.

[61]  Özgür Gürbüz,et al.  Terahertz communications at various atmospheric altitudes , 2020, Phys. Commun..

[62]  Alagan Anpalagan,et al.  Empowering the Edge Intelligence by Air-Ground Integrated Federated Learning in 6G Networks , 2020, ArXiv.

[63]  Song Han,et al.  TinyTL: Reduce Memory, Not Parameters for Efficient On-Device Learning , 2020, NeurIPS.

[64]  Ian F. Akyildiz,et al.  6G and Beyond: The Future of Wireless Communications Systems , 2020, IEEE Access.

[65]  Preben E. Mogensen,et al.  Towards 6G in-X Subnetworks With Sub-Millisecond Communication Cycles and Extreme Reliability , 2020, IEEE Access.

[66]  Yang Gao,et al.  An Inter-Disciplinary Modelling Approach in Industrial 5G/6G and Machine Learning Era , 2020, 2020 IEEE International Conference on Communications Workshops (ICC Workshops).

[67]  Jue Wang,et al.  Enabling 5G on the Ocean: A Hybrid Satellite-UAV-Terrestrial Network Solution , 2020, IEEE Wireless Communications.

[68]  Marko Jurmu,et al.  6G White Paper on Edge Intelligence , 2020, ArXiv.

[69]  Derrick Wing Kwan Ng,et al.  Distributed Estimation Framework for Beyond 5G Intelligent Vehicular Networks , 2020, IEEE Open Journal of Vehicular Technology.

[70]  Mohamed-Slim Alouini,et al.  Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How it Works, State of Research, and Road Ahead , 2020, ArXiv.

[71]  Octavia A. Dobre,et al.  A Prospective Look: Key Enabling Technologies, Applications and Open Research Topics in 6G Networks , 2020, IEEE Access.

[72]  Lingyang Song,et al.  Beyond D2D: Full Dimension UAV-to-Everything Communications in 6G , 2020, IEEE Transactions on Vehicular Technology.

[73]  Jaafar M. H. Elmirghani,et al.  Patient-Centric HetNets Powered by Machine Learning and Big Data Analytics for 6G Networks , 2020, IEEE Access.

[74]  Jesus Alonso-Zarate,et al.  Massive Connectivity in 5G and Beyond: Technical Enablers for the Energy and Automotive Verticals , 2020, 2020 2nd 6G Wireless Summit (6G SUMMIT).

[75]  L. Mucchi,et al.  How 6G Technology Can Change the Future Wireless Healthcare , 2020, 2020 2nd 6G Wireless Summit (6G SUMMIT).

[76]  Lingyang Song,et al.  Deep Learning for Ultra-Reliable and Low-Latency Communications in 6G Networks , 2020, IEEE Network.

[77]  Ke Zhang,et al.  Deep Reinforcement Learning and Permissioned Blockchain for Content Caching in Vehicular Edge Computing and Networks , 2020, IEEE Transactions on Vehicular Technology.

[78]  Octavia A. Dobre,et al.  Decision Fusion for IoT-Based Wireless Sensor Networks , 2020, IEEE Internet of Things Journal.

[79]  Sameer Qazi,et al.  Internet of Things (IoT) for Next-Generation Smart Systems: A Review of Current Challenges, Future Trends and Prospects for Emerging 5G-IoT Scenarios , 2020, IEEE Access.

[80]  Christian Wietfeld,et al.  Towards Cooperative Data Rate Prediction for Future Mobile and Vehicular 6G Networks , 2020, 2020 2nd 6G Wireless Summit (6G SUMMIT).

[81]  Leonardo Mostarda,et al.  Cognition in UAV-Aided 5G and Beyond Communications: A Survey , 2020, IEEE Transactions on Cognitive Communications and Networking.

[82]  Guan Gui,et al.  6G: Opening New Horizons for Integration of Comfort, Security, and Intelligence , 2020, IEEE Wireless Communications.

[83]  Gaurav Sharma,et al.  A Survey of Healthcare Internet of Things (HIoT): A Clinical Perspective , 2020, IEEE Internet of Things Journal.

[84]  Rabindranath Bera,et al.  A Comprehensive Survey on Internet of Things (IoT) Toward 5G Wireless Systems , 2020, IEEE Internet of Things Journal.

[85]  Omprakash Kaiwartya,et al.  Physical Layer Security in Vehicular Networks with Reconfigurable Intelligent Surfaces , 2019, 2020 IEEE 91st Vehicular Technology Conference (VTC2020-Spring).

[86]  Zhu Han,et al.  Reconfigurable Intelligent Surfaces based RF Sensing: Design, Optimization, and Implementation , 2019, ArXiv.

[87]  Dinh C. Nguyen,et al.  Blockchain for 5G and Beyond Networks: A State of the Art Survey , 2019, J. Netw. Comput. Appl..

[88]  Gang Chen,et al.  PhoneBit: Efficient GPU-Accelerated Binary Neural Network Inference Engine for Mobile Phones , 2019, 2020 Design, Automation & Test in Europe Conference & Exhibition (DATE).

[89]  Alessio Zappone,et al.  Holographic MIMO Surfaces for 6G Wireless Networks: Opportunities, Challenges, and Trends , 2020, IEEE Wireless Communications.

[90]  Yifei Yuan,et al.  Potential key technologies for 6G mobile communications , 2019, Science China Information Sciences.

[91]  Nasir Saeed,et al.  A Software-Defined Opto-Acoustic Network Architecture for Internet of Underwater Things , 2019, IEEE Communications Magazine.

[92]  Shakil Ahmed,et al.  6G Wireless Communication Systems: Applications, Requirements, Technologies, Challenges, and Research Directions , 2019, IEEE Open Journal of the Communications Society.

[93]  Albert Y. Zomaya,et al.  Edge Intelligence: The Confluence of Edge Computing and Artificial Intelligence , 2019, IEEE Internet of Things Journal.

[94]  Aruna Seneviratne,et al.  Integration of Blockchain and Cloud of Things: Architecture, Applications and Challenges , 2019, IEEE Communications Surveys & Tutorials.

[95]  Aruna Seneviratne,et al.  Privacy-Preserved Task Offloading in Mobile Blockchain With Deep Reinforcement Learning , 2019, IEEE Transactions on Network and Service Management.

[96]  Solmaz Niknam,et al.  Federated Learning for Wireless Communications: Motivation, Opportunities, and Challenges , 2019, IEEE Communications Magazine.

[97]  Stefano Tomasin,et al.  Requirements and Enablers of Advanced Healthcare Services over Future Cellular Systems , 2019, IEEE Communications Magazine.

[98]  Sundeep Rangan,et al.  Towards 6G Networks: Use Cases and Technologies , 2019, ArXiv.

[99]  Walid Saad,et al.  A Vision of 6G Wireless Systems: Applications, Trends, Technologies, and Open Research Problems , 2019, IEEE Network.

[100]  Mehdi Bennis,et al.  A Speculative Study on 6G , 2019, IEEE Wireless Communications.

[101]  Saoucene Mahfoudh,et al.  Routing Protocols for Wireless Nanosensor Networks and Internet of Nano Things: A Comprehensive Survey , 2020, IEEE Access.

[102]  Xudong Wang,et al.  Terahertz Communications (TeraCom): Challenges and Impact on 6G Wireless Systems , 2019, ArXiv.

[103]  Younsun Kim,et al.  Advanced Data Transmission Framework for 5G Wireless Communications in the 3GPP New Radio Standard , 2019, IEEE Communications Standards Magazine.

[104]  Haitao Zhao,et al.  Deployment Algorithms of Flying Base Stations: 5G and Beyond With UAVs , 2019, IEEE Internet of Things Journal.

[105]  Pingzhi Fan,et al.  6G Wireless Networks: Vision, Requirements, Architecture, and Key Technologies , 2019, IEEE Vehicular Technology Magazine.

[106]  Antonios Tsourdos,et al.  Generalized Hybrid Beamforming for Vehicular Connectivity Using THz Massive MIMO , 2019, IEEE Transactions on Vehicular Technology.

[107]  Soumyajit Mandal,et al.  Wireless Communications and Applications Above 100 GHz: Opportunities and Challenges for 6G and Beyond , 2019, IEEE Access.

[108]  Xu Chen,et al.  Edge Intelligence: Paving the Last Mile of Artificial Intelligence With Edge Computing , 2019, Proceedings of the IEEE.

[109]  Petar Popovski,et al.  Inter-Plane Satellite Matching in Dense LEO Constellations , 2019, 2019 IEEE Global Communications Conference (GLOBECOM).

[110]  Xiaodai Dong,et al.  Distributed and Multilayer UAV Networks for Next-Generation Wireless Communication and Power Transfer: A Feasibility Study , 2019, IEEE Internet of Things Journal.

[111]  Wei Chen,et al.  The Roadmap to 6G: AI Empowered Wireless Networks , 2019, IEEE Communications Magazine.

[112]  David López-Pérez,et al.  IEEE 802.11be Extremely High Throughput: The Next Generation of Wi-Fi Technology Beyond 802.11ax , 2019, IEEE Communications Magazine.

[113]  Antonis A. Argyros,et al.  Accurate Hand Keypoint Localization on Mobile Devices , 2018, 2019 16th International Conference on Machine Vision Applications (MVA).

[114]  Michail Matthaiou,et al.  Hardware-Constrained Millimeter-Wave Systems for 5G: Challenges, Opportunities, and Solutions , 2018, IEEE Communications Magazine.

[115]  Javier Gozálvez,et al.  5G and Beyond: Smart Devices as Part of the Network Fabric , 2018, IEEE Network.

[116]  Martin Reisslein,et al.  Ultra-Low Latency (ULL) Networks: The IEEE TSN and IETF DetNet Standards and Related 5G ULL Research , 2018, IEEE Communications Surveys & Tutorials.

[117]  Sergey Andreev,et al.  Future of Ultra-Dense Networks Beyond 5G: Harnessing Heterogeneous Moving Cells , 2017, IEEE Communications Magazine.

[118]  Pubudu N. Pathirana,et al.  Blockchain for Secure EHRs Sharing of Mobile Cloud Based E-Health Systems , 2019, IEEE Access.

[119]  Octavia A. Dobre,et al.  Signature-Based Nonorthogonal Massive Multiple Access for Future Wireless Networks: Uplink Massive Connectivity for Machine-Type Communications , 2018, IEEE Vehicular Technology Magazine.

[120]  Bikramjit Singh,et al.  5G URLLC: Design Challenges and System Concepts , 2018, 2018 15th International Symposium on Wireless Communication Systems (ISWCS).

[121]  Mehmet Rasit Yuce,et al.  A Wireless Implantable Sensor Design With Subcutaneous Energy Harvesting for Long-Term IoT Healthcare Applications , 2018, IEEE Access.

[122]  Octavia A. Dobre,et al.  All Technologies Work Together for Good: A Glance at Future Mobile Networks , 2018, IEEE Wireless Communications.

[123]  Markku J. Juntti,et al.  Terahertz Technologies to Deliver Optical Network Quality of Experience in Wireless Systems Beyond 5G , 2018, IEEE Communications Magazine.

[124]  Tianqing Zhu,et al.  Machine Learning Differential Privacy With Multifunctional Aggregation in a Fog Computing Architecture , 2018, IEEE Access.

[125]  Daniele Munaretto,et al.  Multi-Access Edge Computing: The Driver Behind the Wheel of 5G-Connected Cars , 2018, IEEE Communications Standards Magazine.

[126]  Muhammad Imran,et al.  Energy Efficiency Perspectives of Femtocells in Internet of Things: Recent Advances and Challenges , 2017, IEEE Access.

[127]  Der-Jiunn Deng,et al.  Efficient Ultra-Reliable and Low Latency Communications and Massive Machine-Type Communications in 5G New Radio , 2017, GLOBECOM 2017 - 2017 IEEE Global Communications Conference.

[128]  Victor C. M. Leung,et al.  Exploiting Interference for Energy Harvesting: A Survey, Research Issues, and Challenges , 2017, IEEE Access.

[129]  Seong Joon Oh,et al.  Adversarial Image Perturbation for Privacy Protection A Game Theory Perspective , 2017, 2017 IEEE International Conference on Computer Vision (ICCV).

[130]  Octavia A. Dobre,et al.  Power-Domain Non-Orthogonal Multiple Access (NOMA) in 5G Systems: Potentials and Challenges , 2016, IEEE Communications Surveys & Tutorials.

[131]  Nicholas D. Lane,et al.  DeepX: A Software Accelerator for Low-Power Deep Learning Inference on Mobile Devices , 2016, 2016 15th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN).

[132]  Maria Rita Palattella,et al.  Internet of Things in the 5G Era: Enablers, Architecture, and Business Models , 2016, IEEE Journal on Selected Areas in Communications.

[133]  Mohsen Guizani,et al.  Internet of Things: A Survey on Enabling Technologies, Protocols, and Applications , 2015, IEEE Communications Surveys & Tutorials.

[134]  Felix Wortmann,et al.  Internet of Things , 2015, Business & Information Systems Engineering.

[135]  Pratap Tokekar,et al.  Sensor planning for a symbiotic UAV and UGV system for precision agriculture , 2013, 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems.