Channel structures and protocol for asset tracking satellite communications links
First Claim
Patent Images
1. A two-way satellite communication system for communicating telemetry data, network parameters and control information, and commands between a network control terminal (NCT) and a plurality of tracking units, comprising:
- at least one frequency division multiple access/time division multiplexed (FDMA/TDM) outbound carrier signal having scheduled slots, broadcast/group message slots, and response/acknowledgment slots;
at least one hybrid frequency division multiple access/time division multiple access (FDMA/TDMA) inbound channel having scheduled slots and random access slots, each inbound channel being associated with a respective outbound carrier signal;
a transmitter at the NCT for transmitting outbound signals to said plurality of tracking units;
a receiver at the NCT for receiving inbound signals from the tracking units;
a transmitter at each of the tracking units for transmitting signals on the shared FDMA/TDMA inbound channels to the NCT; and
a receiver at each of the tracking units for receiving FDMA/TDM outbound signals from the NCT, the outbound carrier signals having (i) scheduled time slots dedicated for transmission from the NCT to assigned tracking units, (ii) broadcast/group message slots for transmission from the NCT to at least a designated group of tracking units, network parameters and control information and commands, and (iii) response/acknowledgment time slots for transmission, from the NCT to tracking units, of responses to and acknowledgments of messages received on inbound channel random access slots; and
each inbound channel having (i) scheduled time slots assigned to tracking units by the NCT and (ii) random access time slots for use by any tracking unit assigned to said each inbound channel and by tracking units logging into the satellite communication system using a slotted ALOHA random channel access method.
0 Assignments
0 Petitions
Accused Products
Abstract
A hybrid FDMA/TDMA technique with both scheduled and random access slots in the return link (tracking unit to hub) and scheduled, broadcast, and acknowledgment slots in the forward link (hub-to-tracking unit) and the associated protocol enables the use of low-energy modem signal processing, while providing advantageous features such as polling, expedited exception event reporting, terrestrial wireless local area network support, tracking unit login/logout, and beam-to-beam hand-off.
-
Citations
24 Claims
-
1. A two-way satellite communication system for communicating telemetry data, network parameters and control information, and commands between a network control terminal (NCT) and a plurality of tracking units, comprising:
-
at least one frequency division multiple access/time division multiplexed (FDMA/TDM) outbound carrier signal having scheduled slots, broadcast/group message slots, and response/acknowledgment slots;
at least one hybrid frequency division multiple access/time division multiple access (FDMA/TDMA) inbound channel having scheduled slots and random access slots, each inbound channel being associated with a respective outbound carrier signal;
a transmitter at the NCT for transmitting outbound signals to said plurality of tracking units;
a receiver at the NCT for receiving inbound signals from the tracking units;
a transmitter at each of the tracking units for transmitting signals on the shared FDMA/TDMA inbound channels to the NCT; and
a receiver at each of the tracking units for receiving FDMA/TDM outbound signals from the NCT, the outbound carrier signals having (i) scheduled time slots dedicated for transmission from the NCT to assigned tracking units, (ii) broadcast/group message slots for transmission from the NCT to at least a designated group of tracking units, network parameters and control information and commands, and (iii) response/acknowledgment time slots for transmission, from the NCT to tracking units, of responses to and acknowledgments of messages received on inbound channel random access slots; and
each inbound channel having (i) scheduled time slots assigned to tracking units by the NCT and (ii) random access time slots for use by any tracking unit assigned to said each inbound channel and by tracking units logging into the satellite communication system using a slotted ALOHA random channel access method. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
-
14. A method of forming wireless local area networks (LANs) of asset tracking units in a satellite communications system, wherein said system includes a network control terminal (NCT), comprising the steps of:
-
providing notification from said NCT to a tracking unit via an outbound channel transmission that said tracking unit is to act as a master tracking unit for a terrestrial wireless LAN;
providing acknowledgement by the appointed master tracking unit to said NCT that said notification has been received;
providing notification from said NCT to the appointed LAN master tracking unit of identification numbers of prospective network member subordinate tracking units;
providing notification from said NCT to the prospective local area network member subordinate tracking units of the identification number of the appointed LAN master tracking unit;
initiating communication between the LAN network master tracking unit and subordinate tracking units via terrestrial wireless LAN protocol to assimilate the subordinate tracking units into the LAN; and
providing the outcome of the subordinate tracking unit entry attempts from the master tracking unit to the NCT. - View Dependent Claims (15, 16)
-
-
17. In a method of tracking mobile assets which comprises affixing a tracking unit to each asset to be tracked, communicating with each tracking unit from a central station to receive from each tracking unit an identification number and location, storing and maintaining a table at the central station, said table including the identification number and location of each tracking unit, sorting tracking units in the table by location to identify tracking units within groups proximate to one another, the improvement of a multiple access technique and a two-way protocol between the central station and the tracking units comprising the steps of:
-
designating scheduled and random access slots in a return link transmitted from the tracking units to the central station;
designating scheduled, broadcast and acknowledgment slots in a forward link transmitted from the central station to the tracking units, the acknowledgment slots associated with the random access slots;
transmitting, by a tracking unit, a login request on a randomly selected random access slot after receiving a broadcast slot;
transmitting, by the central station, an acknowledgment message on an acknowledgment slot corresponding to the randomly selected random access slot on which the login request was transmitted, the acknowledgment including a channel and slot assignment;
tuning, by the tracking unit, to a frequency corresponding to the channel assignment of the acknowledgment;
executing a handshake procedure between the tracking unit and the central station; and
thereafter periodically conducting two-way communication between the tracking unit and the central station over the assigned channel. - View Dependent Claims (18, 19, 20, 21, 22)
-
-
23. In a method of tracking mobile assets which comprises affixing a tracking unit to each asset to be tracked, communicating with each tracking unit from a central station to receive from each tracking unit an identification number and location, storing and maintaining a table at the central station, said table including the identification number and location of each tracking unit, sorting tracking units in the table by location to identify tracking units within groups proximate to one another, the improvement comprising the steps of:
-
designating scheduled and random access slots in a return link transmitted from the tracking units to the central station;
designating scheduled, broadcast and acknowledgment slots in a forward link transmitted from the central station to the tracking units, the acknowledgment slots associated with the random access slots;
transmitting, by the central station, messages to a plurality of selected tracking units in said LAN, simultaneously, via a forward link broadcast slot using a group address;
transmitting, by one of said selected tracking units, a login request on a randomly selected random access slot after said braodcast slot;
transmitting, by the central station, an acknowledgment on an acknowledgment slot corresponding to the randomly selected random access slot on which the login request was transmitted, the acknowledgment including a channel and slot assignment;
tuning, by the tracking unit, to a frequency corresponding to the channel assignment of the acknowledgment;
executing a handshake procedure between said one of said tracking units and the central station; and
thereafter periodically conducting two-way communication between said one of said tracking units and the central station over the assigned channel. - View Dependent Claims (24)
-
Specification