{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T22:32:21Z","timestamp":1778711541124,"version":"3.51.4"},"reference-count":32,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2020,4,17]],"date-time":"2020-04-17T00:00:00Z","timestamp":1587081600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"The International Science and Technology Cooperation Program of China","award":["2017YFE0118900"],"award-info":[{"award-number":["2017YFE0118900"]}]},{"DOI":"10.13039\/100014718","name":"Innovative Research Group Project of the National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61801062,61831002"],"award-info":[{"award-number":["61801062,61831002"]}],"id":[{"id":"10.13039\/100014718","id-type":"DOI","asserted-by":"publisher"}]},{"name":"The Chongqing Natural Science Foundation","award":["cstc2019jcyj-msxmx0288"],"award-info":[{"award-number":["cstc2019jcyj-msxmx0288"]}]},{"name":"The High-end Project for Doctoral Students at Chongqing University of Posts and Telecommunications","award":["BYJS201801"],"award-info":[{"award-number":["BYJS201801"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>As an emerging solution for line-of-sight (LOS) wireless communications, in air-to-ground (A2G) channels, the unmanned aerial vehicle (UAV), and allowing the dynamic and flexible network deployments enables the supplement or\/and replacement of the terrestrial base stations (BSs). However, in conventional multiple-input-multiple-output (MIMO) systems, high-speed communications are significantly limited by channel crosstalks and spectrum scarcities. An orbit angular momentum (OAM) wireless network, allowing co-existence of multiple physical channels within the same frequency band, offers new degrees of freedom to address this dilemma. In this paper, we investigate the UAV-based A2G radio vortex wireless networks and study its channel model. Then we propose a branch and bound search-based mode selection (BBS-MS) scheme, which uses the spatial distribution characteristics of vortex beams to optimize the spectrum efficiency (SE). Theoretical derivations and numerical results demonstrate that our developed BBS-MS scheme can obtain the optimal performance, which outperforms conventional OAM-based MIMO systems. Also, it possesses a lower complexity compared with exhaustive searches.<\/jats:p>","DOI":"10.3390\/s20082289","type":"journal-article","created":{"date-parts":[[2020,4,21]],"date-time":"2020-04-21T04:49:38Z","timestamp":1587444578000},"page":"2289","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Orbit Angular Momentum MIMO with Mode Selection for UAV-Assisted A2G Networks"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5401-8164","authenticated-orcid":false,"given":"Tao","family":"Hu","sequence":"first","affiliation":[{"name":"School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yang","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bo","family":"Ma","sequence":"additional","affiliation":[{"name":"Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield S10 2TN, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jie","family":"Zhang","sequence":"additional","affiliation":[{"name":"School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"},{"name":"Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield S10 2TN, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Thid\u00e9, B., Tamburini, F., Then, H., Someda, C.G., and Ravanelli, R.A. (2015, January 16\u201324). The physics of angular momentum radio. Proceedings of the 2015 1st URSI Atlantic Radio Science Conference (URSI AT-RASC), Las Palmas, Gran Canaria, Spain.","DOI":"10.1109\/URSI-AT-RASC.2015.7302908"},{"key":"ref_2","first-page":"78001","article-title":"Encoding many channels in the same frequency through radio vorticity: First experimental test","volume":"14","author":"Tamburini","year":"2011","journal-title":"New J. Phys."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2456","DOI":"10.1109\/ACCESS.2015.2503293","article-title":"Radio Vortex\u2013Multiple-Input Multiple-Output Communication Systems with High Capacity","volume":"3","author":"Zhu","year":"2015","journal-title":"IEEE Access"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"645","DOI":"10.1002\/2015RS005862","article-title":"OAM multiple transmission using uniform circular arrays: Numerical modeling and ex- perimental verification with two digital television signals","volume":"51","author":"Gaffoglio","year":"2016","journal-title":"Radio Sci."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Liu, S., Zhang, Y., Fu, C.L., Bai, Z., Li, Z., Liao, C., Wang, Y., He, J., Liu, Y., and Wang, Y. (2018). Temperature Insensitivity Polarization-Controlled Orbital Angular Momentum Mode Converter Based on an LPFG Induced in Four-Mode Fiber. Sensors, 18.","DOI":"10.3390\/s18061766"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"488","DOI":"10.1038\/nphoton.2012.138","article-title":"Terabit free-space data transmission employing orbital angular momentum multiplexing","volume":"6","author":"Wang","year":"2012","journal-title":"Nat. Photonics"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1308","DOI":"10.1109\/TWC.2016.2645199","article-title":"Mode Division Multiplexing Communication Using Microwave Orbital Angular Momentum: An Experimental Study","volume":"16","author":"Zhang","year":"2017","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1038\/ncomms5876","article-title":"High-capacity millimetre-wave communications with orbital angular momentum multiplexing","volume":"5","author":"Yan","year":"2014","journal-title":"Nat. Commun."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"59114","DOI":"10.1109\/ACCESS.2019.2915035","article-title":"OFDM-OAM modulation for future wireless communications","volume":"7","author":"Hu","year":"2019","journal-title":"IEEE Access"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Bu, X., Zhang, Z., Liang, X.D., Chen, L., Tang, H., Zeng, Z., and Wang, J. (2018). A Novel Scheme for MIMO-SAR Systems Using Rotational Orbital Angular Momentum. Sensors, 18.","DOI":"10.3390\/s18103511"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1873","DOI":"10.1109\/LAWP.2016.2542187","article-title":"Generation of Orbital Angular Momentum Beams for Electromagnetic Vortex Imaging","volume":"15","author":"Liu","year":"2016","journal-title":"IEEE Antennas Wirel. Propag. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2334","DOI":"10.1109\/COMST.2019.2902862","article-title":"A Tutorial on UAVs for Wireless Networks: Applications, Challenges, and Open Problems","volume":"21","author":"Mozaffari","year":"2018","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1438","DOI":"10.1109\/LCOMM.2018.2828110","article-title":"Three-dimensional geometry-based UAV-MIMO channel modeling for A2G communication environments","volume":"7","author":"Jiang","year":"2018","journal-title":"IEEE Commun. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1109\/MWC.2018.1800196","article-title":"UAV communications based on non-orthogonal multiple access","volume":"26","author":"Liu","year":"2019","journal-title":"IEEE Wirel. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Lee, T.R., Buban, M., Dumas, E., and Baker, C.B. (2019). On the Use of Rotary-Wing Aircraft to Sample Near-Surface Thermodynamic Fields: Results from Recent Field Campaigns. Sensors, 19.","DOI":"10.3390\/s19010010"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Alaoui-Sosse, S., Durand, P., Medina, P., Pastor, P., Lothon, M., and Cernov, I. (2019). OVLI-TA: An Unmanned Aerial System for Measuring Profiles and Turbulence in the Atmospheric Boundary Layer. Sensors, 19.","DOI":"10.3390\/s19030581"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Rautenberg, A., Sch\u00f6n, M., zum Berge, K., Mauz, M., Manz, P., Platis, A., van Kesteren, B., Suomi, I., Kral, S.T., and Bange, J. (2019). The Multi-Purpose Airborne Sensor Carrier MASC-3 for Wind and Turbulence Measurements in the Atmospheric Boundary Layer. Sensors, 19.","DOI":"10.3390\/s19102292"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Rautenberg, A., Graf, M.S., Wildmann, N., Platis, A., and Bange, J. (2018). Reviewing Wind Measurement Approaches for Fixed-Wing Unmanned Aircraft. Atmosphere, 9.","DOI":"10.3390\/atmos9110422"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Witte, B.M., Singler, R.F., and Bailey, S.C.C. (2017). Development of an Unmanned Aerial Vehicle for the Measurement of Turbulence in the Atmospheric Boundary Layer. Atmosphere, 8.","DOI":"10.3390\/atmos8100195"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Nolan, P.J., McClelland, H.G., Woolsey, C.A., and Ross, S.D. (2019). A Method for Detecting Atmospheric Lagrangian Coherent Structures Using a Single Fixed-Wing Unmanned Aircraft System. Sensors, 19.","DOI":"10.3390\/s19071607"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Nolan, P.J., Pinto, J., Gonz\u00e1lez-Rocha, J., Jensen, A., Vezzi, C.N., Bailey, S.C.C., De Boer, G., Diehl, C., Laurence, R., and Powers, C.W. (2018). Coordinated Unmanned Aircraft System (UAS) and Ground-Based Weather Measurements to Predict Lagrangian Coherent Structures (LCSs). Sensors, 18.","DOI":"10.3390\/s18124448"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Schuyler, T.J., Gohari, S.M.I., Pundsack, G., Berchoff, D., and Guzman, M.I. (2019). Using a Balloon-Launched Unmanned Glider to Validate Real-Time WRF Modeling. Sensors, 19.","DOI":"10.3390\/s19081914"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Schuyler, T.J., Bailey, S.C.C., and Guzman, M.I. (2019). Monitoring Tropospheric Gases with Small Unmanned Aerial Systems (sUAS) during the Second CLOUDMAP Flight Campaign. Atmosphere, 10.","DOI":"10.3390\/atmos10080434"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Madridano, \u00c1., Al-Kaff, A., Mart\u00edn, D., and de la Escalera, A.A. (2020). 3D Trajectory Planning Method for UAVs Swarm in Building Emergencies. IEEE Access, 20.","DOI":"10.3390\/s20030642"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Da Rosa, R., Aurelio Wehrmeister, M., Brito, T., Lima, J.L., and Pereira, A.I.P.N. (2020). Honeycomb Map: A Bioinspired Topological Map for Indoor Search and Rescue Unmanned Aerial Vehicles. Sensors, 20.","DOI":"10.3390\/s20030907"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Challita, U., and Saad, W. (2017, January 4\u20138). Network formation in the Sky: Unmanned aerial vehicles for multi-hop wireless backhauling. Proceedings of the IEEE Global Telecommunications Conference (GLOBECOM), Singapore.","DOI":"10.1109\/GLOCOM.2017.8254715"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2163","DOI":"10.1109\/JSAC.2017.2720238","article-title":"Millimeter wave communications with OAM-SM scheme for future mobile networks","volume":"35","author":"Ge","year":"2017","journal-title":"IEEE J. Sel. Areas Commun."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"339","DOI":"10.1109\/TSP.2003.821099","article-title":"Fast antenna subset selection in MIMO systems","volume":"52","author":"Gershman","year":"2004","journal-title":"IEEE Trans. Signal Process."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1759","DOI":"10.1109\/TWC.2005.850307","article-title":"Capacity of MIMO systems with antenna selection","volume":"4","author":"Molisch","year":"2005","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"852","DOI":"10.1109\/LCOMM.2018.2803805","article-title":"A Beam Selection Algorithm for Millimeter-Wave Multi-user MIMO Systems","volume":"22","author":"Pal","year":"2018","journal-title":"IEEE Commun. Let."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"917","DOI":"10.1109\/TC.1977.1674939","article-title":"A Branch and Bound Algorithm for Feature Subset Selection","volume":"26","author":"Narendra","year":"1977","journal-title":"IEEE Trans. Comput."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"9134","DOI":"10.1109\/TVT.2017.2714693","article-title":"Rotman Lens Based Hybrid Analog-Digital Beamforming in Massive MIMO Systems: Array Architectures, Beam Selection Algorithms and Experiments","volume":"66","author":"Gao","year":"2017","journal-title":"IEEE Trans. Veh. Technol."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/8\/2289\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T13:21:20Z","timestamp":1760361680000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/8\/2289"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,4,17]]},"references-count":32,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2020,4]]}},"alternative-id":["s20082289"],"URL":"https:\/\/doi.org\/10.3390\/s20082289","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,4,17]]}}}