Methods and apparatus for detecting of spoofing or jamming activities near a train or other railroad assets uses a message sent from each of a plurality of base stations receiving a wireless packet transmitted by a radio of a railroad asset that reports the PNT information determined by the radio using GNSS and a timestamp for the time of arrival of wireless packet at the base station. The position of the asset is then calculated based on the time arrival of the wireless packet at each base station and compared to the reported position. A warning is generated if the difference exceeds a predetermined threshold.
B61L 25/02 - Indicating or recording positions or identities of vehicles or trains
G01S 19/50 - Determining position whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks
2.
SYSTEMS FOR COMMUNICATIONS BETWEEN HEAD OF-TRAIN AND END-OF-TRAIN
Methods and apparatus for selecting from among multiple available path for transporting messages between a train application in a head-of-train area (HOT) and a train application in an end-of-train area (EOT), the multiple paths including at least one direct path and, optionally, one or more indirect paths, each path including at least one wireless segment. A communications manager selects a path using a predetermined method that considers, optionally, how many attempts there have been to transmit an application message and one or more predetermined key performance indicators.
Methods for detecting of spoofing or jamming activities near a train or other railroad assets uses a message sent from each of a plurality of base stations receiving a wireless packet transmitted by a radio of a railroad asset that reports the PNT information determined by the radio using GNSS and a timestamp for the time of arrival of wireless packet at the base station. The position of the asset is then calculated based on the time arrival of the wireless packet at each base station and compared to the reported position. A warning is generated if the difference exceeds a predetemiined threshold.
G01S 19/50 - Determining position whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks
4.
SYSTEMS FOR COMMUNICATIONS BETWEEN HEAD OF-TRAIN AND END-OF-TRAIN
A communication system for sending messages between a train application in a head-of-train area (HOT) and a train application in an end-of-train area (EOT) has multiple communication paths to send a message between train applications in the EOT and HOT, the paths including at least one direct path and, optionally, one or more indirect paths, with each path including at least one wireless segment. A communications manager may select the path using a predetermined method that considers, for example, how many attempts there have been to transmit an application message and, optionally, one or more predetermined key performance indicators.
Improvements for radios for communications between an end of train unit to a head of train that allows for simultaneous reception of messages on any one of three RF link types, for example, Association of American Railroads (AAR) S-9152 RF links in the 450 MHz band, ITCR (Interoperable Train Control Radio) links in the 220 MHz band, and RF links in the 450 MHz band using a higher-order modulation and coding scheme than provided by S-9152.
H04B 1/00 - Details of transmission systems, not covered by a single one of groups Details of transmission systems not characterised by the medium used for transmission
Improvements for radios for communications between an end of train unit to a head of train that allows for simultaneous reception of messages on any one of three RF link types, for example, Association of American Railroads (AAR) S-9152 RF links in the 450 MHz band, ITCR (lnteroperable Train Control Radio) links in the 220 MHz band, and RF links in the 450 MHz band using a higher-order modulation and coding scheme than provided by S-9152.
7.
ADAPTIVE CODING, MODULATION, AND POWER CONTROL FOR POSITIVE TRAIN CONTROL SYSTEMS
To improve throughput rates of packets transmitting positive train control (PTC) messages in an asynchronous wireless network that supports controlling movement of trains, data rates are adjusted based one or more conditions of the link. Modulation and coding schemes with less overhead can be employed to increase the data rate at which information is transferred when an estimated link quality or conditions are relatively good. Conversely, when the estimated link quality is relatively poor, more robust modulation and coding schemes for transmissions can be used to maintain link performance but at the cost of reduced data rates. Optionally, if the estimated link quality is higher than required to achieve a predefined maximum transmit rate at a given default power rate, transmit power can be reduced to that necessary for transmit at the predefined maximum transmit rate.
A wireless train control network is adapted for forwarding data between a remote radio in an EOT unit and remote radio at the head of train using the base stations of the wireless train control network. A base station's current table of base station radios and remote radios that it hears or has a connection is distributed to neighboring base stations by a routing information exchange application. Tables are sent to and received from the application using a messaging service of the wireless train control network. A base station builds from the tables of neighboring base stations a route to a remote radio to which it is not connected, and forwards wireless data packets received for it by transmitting it to another base station radio.
An end-of-train (EOT) unit that comprises an enclosure housing its monitoring, control, and communication equipment and systems, an arm that positions and supports at least one auxiliary wheel on a rail of a track to rotate electrical generator coupled to the auxiliary wheel while the train is moving.
B61L 15/00 - Indicators provided on the vehicle or train for signalling purposes
H02K 7/10 - Structural association with clutches, brakes, gears, pulleys or mechanical starters
H02J 7/14 - Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
11.
END OF TRAIN TO HEAD OF TRAIN COMMUNICATION OVER A TRAIN CONTROL NETWORK
B61K 13/00 - Other auxiliaries or accessories for railways
H04W 4/42 - Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for mass transport vehicles, e.g. buses, trains or aircraft
H04W 40/02 - Communication route or path selection, e.g. power-based or shortest path routing
H04W 40/24 - Connectivity information management, e.g. connectivity discovery or connectivity update
H04W 60/00 - Affiliation to network, e.g. registrationTerminating affiliation with the network, e.g. de-registration
Improvements to demodulators in receivers of radios used for train communications t to receive a radio frequency (RF) signal transmitting a packet of data. A demodulator is configured to generate a soft decision for a decoder, the soft decision including reliability information determined by calculating for the bit position a logarithmic likelihood ratio (LLR). The demodulator is configured to correct a bias in the LLR calculation for any one of the bit positions resulting from a difference in the number symbols in the set of all possible symbols that could have a 0 value in the bit position and the set of all possible symbols that could have a 1 in the bit position.
Improvements to demodulators in receivers of radios used for train communications t to receive a radio frequency (RF) signal transmitting a packet of data. A demodulator is configured to generate a soft decision for a decoder, the soft decision including reliability information determined by calculating for the bit position a logarithmic likelihood ratio (LLR). The demodulator is configured to correct a bias in the LLR calculation for any one of the bit positions resulting from a difference in the number symbols in the set of all possible symbols that could have a 0 value in the bit position and the set of all possible symbols that could have a 1 in the bit position.
To improve throughput rates of packets transmitting positive train control (PTC) messages in an asynchronous wireless network that supports controlling movement of trains, data rates are adjusted based one or more conditions of the link. Modulation and coding schemes with less overhead can be employed to increase the data rate at which information is transferred when an estimated link quality or conditions are relatively good. Conversely, when the estimated link quality is relatively poor, more robust modulation and coding schemes for transmissions can be used to maintain link performance but at the cost of reduced data rates. Optionally, if the estimated link quality is higher than required to achieve a predefined maximum transmit rate at a given default power rate, transmit power can be reduced to that necessary for transmit at the predefined maximum transmit rate.
09 - Scientific and electric apparatus and instruments
Goods & Services
Downloadable computer software for the remote testing and enhancement of positive train control network communications; Downloadable software for the remote testing of the functionality of communications and the exchange of messages in a positive train control network
09 - Scientific and electric apparatus and instruments
Goods & Services
radios; radio frequency transceivers for controlling, transmitting, receiving, and routing wireless messages and data; radios used for positive train control operations; wireless communication devices used for receiving and transmitting messages in a positive train control system; wireless communication devices used for receiving and transmitting messages in a interoperable train control 220 MHz network
09 - Scientific and electric apparatus and instruments
Goods & Services
radios; radio frequency transceivers for controlling, transmitting, receiving and routing wireless messages and data; radios used for positive train control operations; wireless communication devices used for receiving and transmitting messages in a positive train control system
42 - Scientific, technological and industrial services, research and design
Goods & Services
Providing an Internet website portal featuring technology enabling users to remotely monitor, report and provide analysis of active positive train control radios; Providing an Internet website portal featuring technology enabling users to remotely monitor and report radio connection and signal flow issues within the positive train control radio network; Providing an Internet website portal featuring technology enabling users to provide real time positive train control data, operational status, alerts, and notifications
42 - Scientific, technological and industrial services, research and design
Goods & Services
providing on-line, non-downloadable geographic information system (GIS) software for use in the railroad industry; providing an on-line, non-downloadable, Internet-based software application used for radio frequency mapping for use in the railroad industry; computer services, namely, hosting an online software program that captures, stores, analyzes and displays positive train control radio status and events
09 - Scientific and electric apparatus and instruments
Goods & Services
computer interface boards; computer hardware used to interface to external wayside devices; computer hardware used to interface with positive train control technology
09 - Scientific and electric apparatus and instruments
Goods & Services
computer hardware and downloadable computer software platform to support on-board and wayside data processing for railway operations; computer hardware and downloadable software for wayside messaging, monitoring and control of wayside systems, bi-directional communications, and data analytics; device comprised of computer hardware and downloadable software for use in rail operations
09 - Scientific and electric apparatus and instruments
Goods & Services
high speed central processing units; high speed central processing units for use with positive train control platforms; computer central processing units for use with wayside messaging, analytics and processing applications
24.
Wide band sensing of transmissions in FDM signals containing multi-width channels
A radio for determining the occupancy of a variable width channel for secondary use, the variable width channel with a bandwidth equal to an integer multiple of the bandwidth of a plurality of narrowband channels in an RF frequency band. The radio decides whether the variable width channel in the RF band is occupied by whether classifying each of the narrowband channels corresponding to the variable width channel and each of a plurality of sub-bands with bandwidths of narrowband channels but center frequencies shifted by one-half of the bandwidth of the narrowband channel and overlap with the bandwidth of the variable width channel as containing signal or noise based on measured energy levels.
A method for facilitating the more efficient opportunistic use of one or more frequency division multiplexed (FDM) channels in a frequency band by a group of two or more secondary users (SU) that have formed a point-to-multipoint, centralized ad hoc network, with one SU acting as a central node and the remaining SU acting as remote nodes. Each SU adheres to a predetermined protocol utilizing synchronized time slots in each of the channels being used by the network, each time slot having at least one data transmission period and at least one primary user detection period during which no SU transmits. The central SU node determines channel availability. Remote SU nodes may listen for primary user transmissions in a channel and inform the central SU node of detected activity. Remote nodes contend for transmission during a data transmission period of a time slot unless the channel has been reserved by a remote node after successful transmission in the data transmission period of a preceding time slot.
To sense and detect primary user activity in variable-width channels in a radio frequency (RF) band that is divided into a predetermined number of narrowband channels, a radio for secondary use transmissions within the RF band classifies as either signal or noise each the narrowband channels and each of a plurality of subbands with the RF band. The sub-bands have bandwidths equal to the bandwidths of narrowband channels and center frequencies shifted by one-half of the bandwidth of the narrowband channels. The radio decides whether a variable width channel is occupied by a primary user transmissions, and thus whether it is free for secondary use, based on classification of each narrowband channel and shifted sub-band that overlaps with the variable width channel.
Systems and methods for interfacing a railroad centralized traffic control wayside and a railroad centralized traffic control office using interoperable train control messaging
A method of exchanging centralized train control (CTC) messages in a railroad communication system includes generating a message having a format defined by a protocol with an application running on a sending one of a railroad wayside system and a railroad dispatch system. A railroad edge messaging protocol (EMP) header and a railroad Class D messaging transport header are appended to the message to generate a packet. The packet is transmitted to a receiving one of the railroad dispatch system and the railroad wayside system across the railroad communications system.
A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.
B61L 3/22 - Continuous control along the route using magnetic or electrostatic inductionContinuous control along the route using electromagnetic radiation
B61L 15/00 - Indicators provided on the vehicle or train for signalling purposes
B61L 3/12 - Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control controlling electrically using magnetic or electrostatic inductionDevices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control controlling electrically using radio waves
B61L 27/00 - Central railway traffic control systemsTrackside controlCommunication systems specially adapted therefor
09 - Scientific and electric apparatus and instruments
Goods & Services
Communications software for connecting computer networks; computer software for the exchange of data between networks; electronic communications systems comprised of computer hardware and software for the transmission of data between two points; communications software that allows applications to exchange messages; communications software for connecting global computer networks
09 - Scientific and electric apparatus and instruments
42 - Scientific, technological and industrial services, research and design
Goods & Services
Computer software for communications monitoring, tracking, configuring, diagnosis, and data analytics; computer operating programs and computer operating systems; communications software for connecting railroad operations; computer software for monitoring, tracking, and diagnosing assets over a computer network; radios; radio frequency transceivers Development of wired and wireless communication hardware and software
31.
Systems and methods using digital predistortion to linearize radio transmitter operation
A method of linearizing a relationship between a signal to an amplifier and an output signal from the amplifier includes applying an inverse of a transfer function of the amplifier to the signal prior to presenting the signal as the amplifier input. The inverse transfer function is represented by a polynomial defined by a set of coefficients. The transmitter output signal is measured by the idle receiver in a time division duplex system. The output signal is filtered to isolate intermodulation products of a selected order and the peak power of the isolated intermodulation products is then estimated. An adaptive algorithm is applied in response to the estimate of the peak power to update the set of coefficients of the polynomial representing the inverse of the transfer function of the amplifier.
H04K 1/02 - Secret communication by adding a second signal to make the desired signal unintelligible
H04L 25/03 - Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
H04L 25/49 - Transmitting circuitsReceiving circuits using code conversion at the transmitterTransmitting circuitsReceiving circuits using predistortionTransmitting circuitsReceiving circuits using insertion of idle bits for obtaining a desired frequency spectrumTransmitting circuitsReceiving circuits using three or more amplitude levels
H03F 1/32 - Modifications of amplifiers to reduce non-linear distortion
H04L 25/08 - Modifications for reducing interferenceModifications for reducing effects due to line faults
H03F 3/19 - High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
H03F 3/24 - Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
H04L 5/14 - Two-way operation using the same type of signal, i.e. duplex
32.
Systems and methods using digital predistortion to linearize radio transmitter operation
A method of linearizing a relationship between a signal to an amplifier and an output signal from the amplifier includes applying an inverse of a transfer function of the amplifier to the signal prior to presenting the signal as the amplifier input. The inverse transfer function is represented by a polynomial defined by a set of coefficients. The transmitter output signal is measured by the idle receiver in a time division duplex system. The output signal is filtered to isolate intermodulation products of a selected order and the peak power of the isolated intermodulation products is then estimated. An adaptive algorithm is applied in response to the estimate of the peak power to update the set of coefficients of the polynomial representing the inverse of the transfer function of the amplifier.
H04K 1/02 - Secret communication by adding a second signal to make the desired signal unintelligible
H04L 25/03 - Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
H04L 25/49 - Transmitting circuitsReceiving circuits using code conversion at the transmitterTransmitting circuitsReceiving circuits using predistortionTransmitting circuitsReceiving circuits using insertion of idle bits for obtaining a desired frequency spectrumTransmitting circuitsReceiving circuits using three or more amplitude levels
H03F 1/32 - Modifications of amplifiers to reduce non-linear distortion
H04L 5/14 - Two-way operation using the same type of signal, i.e. duplex
H04L 25/08 - Modifications for reducing interferenceModifications for reducing effects due to line faults
H03F 3/19 - High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
09 - Scientific and electric apparatus and instruments
Goods & Services
computer software for communications monitoring, troubleshooting, configuring, diagnosis, and data analytics; computer operating programs and computer operating systems; communications software for connecting railroad operations; computer software for monitoring, tracking, and diagnosing assets over a computer network
09 - Scientific and electric apparatus and instruments
Goods & Services
computer software for communications monitoring, troubleshooting, configuring, diagnosis, and data analytics; computer operating programs and computer operating systems; communications software for connecting railroad operations; computer software for monitoring, tracking, and diagnosing assets over a computer network
35.
Host-radio exchange interface for railroad communications and railroad communications methods using the same
A method of exchanging messages between a railroad communications system radio operating in accordance with a host-radio exchange protocol and a railroad messaging system. A communications manager of the railroad messaging system, operating in accordance with the host-radio exchange protocol, transmits a request to the radio requesting registration as a host of the radio. The communications manager is selectively registered with the radio as a primary host. The radio sends a message to the primary host identifying an available wireless link between the radio and another radio of the railroad communications system. Data messages, which include data being exchanged between the primary host and the primary host of the another radio across the wireless link, are exchanged between the radio and the primary host in accordance with the host-radio exchange protocol.
A method of exchanging messages between a railroad communications system radio operating in accordance with a host-radio exchange protocol and a railroad messaging system. A communications manager of the railroad messaging system, operating in accordance with the host-radio exchange protocol, transmits a request to the radio requesting registration as a host of the radio. The communications manager is selectively registered with the radio as a primary host. The radio sends a message to the primary host identifying an available wireless link between the radio and another radio of the railroad communications system. Data messages, which include data being exchanged between the primary host and the primary host of the another radio across the wireless link, are exchanged between the radio and the primary host in accordance with the host-radio exchange protocol.
A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.
B61L 15/00 - Indicators provided on the vehicle or train for signalling purposes
B61L 3/12 - Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control controlling electrically using magnetic or electrostatic inductionDevices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control controlling electrically using radio waves
B61L 3/22 - Continuous control along the route using magnetic or electrostatic inductionContinuous control along the route using electromagnetic radiation
B61L 27/00 - Central railway traffic control systemsTrackside controlCommunication systems specially adapted therefor
38.
SYSTEMS AND METHODS FOR USING A RAILROAD RAIL AS RADIATING ELEMENT FOR TRANSMITTING WIRELESS COMMUNICATIONS SIGNALS
A railroad communication system includes a radio transmitter for generating radio communications signals and a length of railroad rail coupled to the radio transmitter. The length of rail is disposed on a set of nonconductive railroad ties to form a transmission line for radiating the radio communications signals to a radio receiver in a vicinity of the length of railroad rail.
H01B 7/40 - Insulated conductors or cables characterised by their form with arrangements for facilitating mounting or securing
H01B 11/18 - Coaxial cablesAnalogous cables having more than one inner conductor within a common outer conductor
H01Q 9/40 - Element having extended radiating surface
H04B 1/38 - Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
H04B 7/26 - Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
A method of messaging in a communications system includes generating a message at an application layer. The message and associated message handling codes are passed to a transport layer and the message fragmented. The fragmented message and the message handling codes are passed to a network layer and the fragmented message selectively segmented as indicated by the message handling code. The selectively segmented message and the message handling code are passed to a link layer and formed into a packet including packet type information and data parts. The packet is passed to a physical layer and a preamble is added. The preamble and packet are transmitted with a radio.
A radio receiver including a memory storing a reference sample sequence and a synchronizer. The synchronizer receives a data packet, samples and modulates symbols from the data packet and then generates phase-information samples from the modulated samples. The phase-information samples are low-pass to generate a filtered phase-information sample sequence. Samples of the filtered phase-information sample sequence are selectively compared with samples of the reference sample sequence and bit synchronization is established when a selected number of samples of the filtered phase-information sample sequence match a selected number of samples of the reference sample sequence.
A radio system including a selected number inputs for substantially simultaneously receiving radio signals in different frequency bands and a selected number of conversion paths for converting the radio signals received at corresponding ones of the inputs into a corresponding number of digital streams. Digital processing circuitry substantially simultaneously processes digital samples for plurality of channels, the samples taken from at least one of the digital streams, wherein a maximum number of channels is greater than a maximum number of digital streams provided by the conversion paths.
H03D 3/18 - Demodulation of angle-modulated oscillations by detecting phase difference between two signals obtained from input signal by means of synchronous gating arrangements
An interface device for interfacing a set of wayside systems with a radio transmitter includes a plurality of input ports each having at least one input for receiving a signal representing a state of a corresponding wayside system and first and second parallel data paths coupled to the plurality of input ports. Each data path includes input protection circuitry coupled to the inputs of the input ports for preventing short-circuit and open-circuit conditions from triggering a false input state, a multiplexer for selecting between the input port; and a processor for scanning the input ports with the multiplexer to determine the state of current signals appearing at the inputs. In response to determining the state of the current signals appearing at the inputs, the processor generates a message communicating a current state of the wayside systems for delivery to the radio transmitter.
A method for exchanging information within a radio communications system includes establishing communications between radio systems utilizing a carrier sense multiple access mode during a period of lower traffic load on the radio communications system and establishing communications between the radio systems utilizing a time division multiple access mode during a period of higher traffic load on the radio communications system.
A method for implementing communications in a railroad communications system having a base station radio and remote radios, the remote radios including a mobile radio and a wayside radio. The method includes assigning a common radio communications channel for allowing a remote radio to connect with the base station radio using a carrier sense multiple access (CSMA) communications protocol and assigning a local channel for allowing communications between the radio base station and the remote radios and between the remote radios, wherein communications on the local channel utilizes a selected one of fixed time division multiple access (FTDMA) and dynamic time division multiple access (DTDMA) communications protocols.
A method for implementing communications in a railroad communications system having a base station radio and remote radios, the remote radios including a mobile radio and a wayside radio. The method includes assigning a common radio communications channel for allowing a remote radio to connect with the base station radio using a carrier sense multiple access (CSMA) communications protocol and assigning a local channel for allowing communications between the radio base station and the remote radios and between the remote radios, wherein communications on the local channel utilizes a selected one of fixed time division multiple access (FTDMA) and dynamic time division multiple access (DTDMA) communications protocols.
B60L 15/40 - Adaptation of control equipment on vehicle for remote actuation from a stationary place
B61C 17/12 - Control gearArrangements for controlling locomotives from remote points in the train or when operating in multiple units
B61L 3/08 - Devices along the route for controlling devices on the vehicle or train, e.g. to release brake or to operate a warning signal at selected places along the route, e.g. intermittent control controlling electrically
B61L 7/06 - Remote control of local operating means for points, signals, or track-mounted scotch-blocks using electrical transmission
B61L 27/00 - Central railway traffic control systemsTrackside controlCommunication systems specially adapted therefor
B61L 27/04 - Automatic systems, e.g. controlled by trainChange-over to manual control
H04J 3/16 - Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
A method for implementing communications in a railroad communications system having a base station radio and remote radios, the remote radios including a mobile radio and a wayside radio. The method includes assigning a common radio communications channel for allowing a remote radio to connect with the base station radio using a carrier sense multiple access (CSMA) communications protocol and assigning a local channel for allowing communications between the radio base station and the remote radios and between the remote radios, wherein communications on the local channel utilizes a selected one of fixed time division multiple access (FTDMA) and dynamic time division multiple access (DTDMA) communications protocols.
A method for implementing communications in a railroad communications system having a base station radio and remote radios, the remote radios including a mobile radio and a wayside radio. The method includes assigning a common radio communications channel for allowing a remote radio to connect with the base station radio using a carrier sense multiple access (CSMA) communications protocol and assigning a local channel for allowing communications between the radio base station and the remote radios and between the remote radios, wherein communications on the local channel utilizes a selected one of fixed time division multiple access (FTDMA) and dynamic time division multiple access (DTDMA) communications protocols.
A communications system includes a plurality of operational nodes and a plurality of data distribution systems. A data distribution system operating in an active mode manages exchanges of data between the operational nodes and further operable to periodically transmit go passive messages commanding at least one other of the data distribution systems to operate in a passive mode. A data distribution system operating in the passive mode waits for receipt of one of the go passive messages, continues to operate in the passive mode after receiving one of the go passive messages within a predetermined time out period, and transitions to the active mode after the time out period has expired without receipt of one of the go passive messages.
09 - Scientific and electric apparatus and instruments
Goods & Services
Communications software for connecting network; Computer hardware and software for setting up and configuring local area networks; Computer hardware and software for setting up and configuring wide area networks; Computer operating programs; Computer operating programs and computer operating systems; Computer software for administration of computer local area networks; Computer software for administration of computer networks; LAN (local area network) operating software; Network access server operating software; WAN (wide area network) operating software
09 - Scientific and electric apparatus and instruments
Goods & Services
radios; packet radios; wireless modems; communications terminals for message and data communications; computer hardware and software for two-way data and messaging services; systems, namely, radio frequency tranceivers, for controlling, transmitting, receiving and routing wireless messages and data; computer hardware and software for tracking the location and status of fleet vehicles and vessels and for communicating and exchanging data with and among fleet vehicles and vessels
