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Self-organized Time-division Multiple Access
Self-organized time-division multiple access (STDMA or SOTDMA) is a channel access method designed by Håkan Lans, based on time-division multiplexing. The term "self-organized" describes the manner in which time slots are assigned to users. Time-division multiple access (TDMA) divides a channel into frames, which furthermore are subdivided into a vast number of time slots. Users transmit in rapid succession, one after the other, each using their own time slot. One of the drawbacks of TDMA is that it requires a central station for slot assignment and time synchronization. STDMA proposes a method for assigning slots without the involvement of a central station. Time synchronization is usually taken care of using Coordinated Universal Time (UTC). Slot assignment is handled by each transmitter broadcasting its next slot reservation as part of the message during its current slot. STDMA is in use by the Automatic Identification System (AIS), a standard marine short-range coastal track ...
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Håkan Lans
Anders Håkan Lans (born 2 November 1947 in Enskede) is a Swedish inventor, employed by the Swedish National Defence Research Institute (FOA), and then Stockholm University. whose primary contribution is the Self-Organized Time Division Multiple Access (STDMA) datalink technology used in Automatic Identification System (AIS) for vehicle navigation. Lans has won many notable Swedish honors for his inventions. Lans is also known for various ultimately unsuccessful legal disputes over his computer-related patents. STDMA Håkan Lans is the designer of a tracking system which makes use of a Self-Organized Time Division Multiple Access (STDMA) datalink. The STDMA datalink is currently in use in Automatic Identification System (AIS). AIS is a short range coastal tracking system which is mandatory aboard international voyaging ships with gross tonnage (GT) of 300 or more tons, and all passenger ships regardless of size. STDMA is also in use as one of the three physical layer models ...
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Time-division Multiple Access
Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream. TDMA is used in digital 2G cellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, in the Maritime Automatic Identification System, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for portable phones. TDMA was first used in satellite communication systems by Wester ...
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Frame (telecommunications)
A frame is a digital data transmission unit in computer networking and telecommunications. In packet switched systems, a frame is a simple container for a single network packet. In other telecommunications systems, a frame is a repeating structure supporting time-division multiplexing. A frame typically includes frame synchronization features consisting of a sequence of bits or symbols that indicate to the receiver the beginning and end of the payload data within the stream of symbols or bits it receives. If a receiver is connected to the system during frame transmission, it ignores the data until it detects a new frame synchronization sequence. Packet switching In the OSI model of computer networking, a frame is the protocol data unit at the data link layer. Frames are the result of the final layer of encapsulation before the data is transmitted over the physical layer. A frame is "the unit of transmission in a link layer protocol, and consists of a link layer header followed b ...
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Coordinated Universal Time
Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communication, navigation, scientific research, and commerce. UTC has been widely embraced by most countries and is the effective successor to Greenwich Mean Time (GMT) in everyday usage and common applications. In specialised domains such as scientific research, navigation, and timekeeping, other standards such as Universal Time, UT1 and International Atomic Time (TAI) are also used alongside UTC. UTC is based on TAI (International Atomic Time, abbreviated from its French name, ''temps atomique international''), which is a weighted average of hundreds of atomic clocks worldwide. UTC is within about one second of mean solar time at 0° longitude, the currently used prime meridian, and is not adjusted for daylight saving time. The coordination of t ...
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Automatic Identification System
The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships and is used by vessel traffic services (VTS). When satellites are used to receive AIS signatures, the term ''Satellite-AIS'' (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport. Although technically and operationally distinct, the ADS-B system is analogous to AIS and performs a similar function for aircraft. Information provided by AIS equipment, such as unique identification, coordinate system, position, course (navigation), course, and speed, can be displayed on a screen or an electronic chart display and information system (ECDIS). AIS is intended to assist a vessel's watchstanding officers and allow sea, maritime authorities to track and monitor vessel movements. AIS integrates a standardization, standardized very high frequency, VHF transceiver with a positioning system such a ...
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International Civil Aviation Organization
The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international scheduled air transport, air transport to ensure safe and orderly growth. The ICAO headquarters are located in the Quartier international de Montréal of Montreal, Quebec, Canada. The ICAO Council adopts standards and recommended practices concerning air navigation, its infrastructure, flight inspection, prevention of unlawful interference, and facilitation of border-crossing procedures for international civil aviation. ICAO defines the protocols for Aviation accidents and incidents, air accident investigation that are followed by :Organizations investigating aviation accidents and incidents, transport safety authorities in countries signatory to the Convention on International Civil Aviation. The Air Navigation Commission (ANC) is the techn ...
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VHF Data Link
The VHF Data Link or VHF Digital Link (VDL) is a means of sending information between aircraft and ground stations (and in the case of VDL Mode 4, other aircraft) over VHF. Aeronautical VHF data links use the band 117.975–137 MHz assigned by the International Telecommunication Union to Aeronautical mobile (R) service. There are ARINC standards for ACARS on VHF and other data links installed on approximately 14,000 aircraft and a range of ICAO standards defined by the Aeronautical Mobile Communications Panel (AMCP) in the 1990s. Mode 2 is the only VDL mode being implemented operationally to support Controller Pilot Data Link Communications (CPDLC). ICAO VDL Mode 1 The ICAO AMCP defined this Mode for validation purposes. It was the same as VDL Mode 2 except that it used the same VHF link as VHF ACARS so it could be implemented using analog radios before VHF Digital Radio implementation was completed. The ICAO AMCP completed validation of VDL Modes 1&2 in 1994, after which ...
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United States Patent And Trademark Office
The United States Patent and Trademark Office (USPTO) is an List of federal agencies in the United States, agency in the United States Department of Commerce, U.S. Department of Commerce that serves as the national patent office and trademark registration authority for the United States. The USPTO's headquarters are in Alexandria, Virginia, after a 2005 move from the Crystal City, Virginia, Crystal City area of neighboring Arlington County, Virginia, Arlington, Virginia. The USPTO is "unique among federal agencies because it operates solely on fees collected by its users, and not on taxpayer dollars". Its "operating structure is like a business in that it receives requests for services—applications for patents and trademark registrations—and charges fees projected to cover the cost of performing the services [it] provide[s]". The office is headed by the Under Secretary of Commerce for Intellectual Property, under secretary of commerce for intellectual property and directo ...
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Reexamination
In United States patent law, a reexamination is a process whereby anyone—third party or inventor—can have a U.S. patent reexamined by a patent examiner to verify that the subject matter it claims is patentable. To have a patent reexamined, an interested party must submit prior art, in the form of patents or printed publications, that raises a "substantial new question of patentability". The Leahy-Smith America Invents Act makes substantial changes to the U.S. patent system, including new mechanisms for challenging patents at the U.S. Patent and Trademark Office. One of the new mechanisms is a post-grant review proceeding, which will provide patent challengers expanded bases on which to attack patents. Process A request for a reexamination can be filed by anyone at any time during the period of enforceability of a patent. To request a reexamination, one must submit a "request for reexamination" which includes (1) a statement pointing out each "substantial new question of pa ...
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