Research On Key Technologies Of Machine-type Communication In Maritime Internet Of Things

The concept of maritime Internet of Things(Io T)is developed initially to modernize the maritime industries by the International Maritime Organization(IMO)under the name E-Navigation,involves the harmonized collection,integration,exchange,presentation,and analysis of maritime information to enhance berth-to-berth navigation and related services for safety and security at sea,and the protection of the marine environment.Just as for any other Io T applications,machine-type communication(MTC)is the key to maritime Io T due to the need for establishing the communication between vessels or maritime equipment(i.e.,“things”)and control stations as well as among vessels.VHF Data Exchange System(VDES),put forward by the International Association of Marine Aids to Navigation and Lighthouse Authorities(IALA),is arguably the first truly maritime MTC system for maritime Io T,and probably one of the most complicated MTC networks in the sense that it involves the terrestrial communication(i.e.,VDE-TER),the satellite communication(i.e.,VDE-SAT),as well as the proximity communication,i.e.,Automatic Identification System(AIS)and Application Specific Message(ASM).This dissertation outlines the key technical requirements regarding the ubiquity,continuity,heterogeneity,simplicity,interoperability,and scalability for maritime Io T services,and addresses these requirements with a practical maritime MTC system design,based on the VHF spectrum allocated for maritime MTC by the International Telecommunication Union(ITU).The main contents and contributions are listed as follows:(1)The two problems need to be managed in the spectrum allocation for maritime MTC(i.e.,VDES)are studied,including the satellite downlink interference to the land systems on the same frequency band and the cross-link interference introduced by the out-of-band emissions.It proposes an electromagnetic “power flux density(PFD)mask” concept for evaluating and constraining the emission onto earth from a satellite space station,and demonstrates the mathematical derivation of such a PFD mask from three closely related regulations on the legacy land mobile systems by the Electronic Communications Committee(ECC)and ITU,ensuring that the actual interference from a space station that a land system experiences is no worse than that from any other land system allowed by the regulations.The PFD mask derived with this methodology has been acceptedby the ITU as one of the emission constraints for VDE-SAT spectrum allocation.It then analyzes the potential scenarios with out-of-band leakage interference in the VDES spectrum allocation,including the cross-interference between uplink and downlink in the VDE-TER and VDE-SAT,as well as the out-of-band emissions to AIS and ASM signal from the VDE-TER or VDE-SAT air interface.It explains the rationale behind the spectrum allocation of VDES licensed recently by ITU.It then proposes the spectrum sharing and interference management mechanism for such unique spectrum,which provides insight into the air interface design of the maritime MTC system operating on this spectrum.(2)A highly adaptive,service-centric,as well as spectrum and energy-efficient maritime MTC network framework is studied.The network structure leverages the three functional network components,including the two logically centralized entities,i.e.,the Network Controller and the Maritime Application Server,as well as the entity of the Control Station.It then presents a four-layer protocol stack model for maritime MTC and the functionality of each layer.A unified method using the concept of layer channels and protocol data units for control and service data exchange between protocol layers is described.Finally,the routing scheme for the service data between the internal maritime MTC network and the maritime service providers on the external public IP networks is studied,which provides a spectrum and energy-efficient means for maritime devices to obtain various maritime Io T services.(3)The radio interface of a maritime MTC system operating on the VDES spectrum is studied,including the design of air interface for ASM,VDE-TER and VDE-SAT under VDES.To avoid the pitfalls in AIS,the design of ASM air interface based on the layered protocol structure that decouples the application layer from the air interface is firstly presented,for delivering more versatile maritime proximity applications.It also demonstrates a new physical layer design for ASM with significantly improved robustness and spectral efficiency over AIS,via channel coding as well as adaptive modulation and coding scheme.Following consideration of the spectral efficiency in the ASM interface is limited by the distributed resource allocation mechanism,the VDE-TER and VDE-SAT air interfaces design uses a centralized resource allocation mechanism to improve spectral efficiency.By leveraging the proposed transmission resource block concept,the VDE-TER and VDE-SAT channelization can provide a maximally unified framework for VDE-TER and VDE-SAT air interfaces;both FDD and TDD transmissions;and supporting different maritime device categories.A unified framework not only reduces the complexity and cost of a VDES transceiver but,more importantly,eases the coordination between VDE-TER and VDE-SAT in spectrum sharing and interference management.