Skywave adaptable communication apparatus

• US 4,937,822 A
• Filed: 06/27/1989
• Issued: 06/26/1990
• Est. Priority Date: 06/27/1989
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Cable, Stephen W., Weddle, Daniel O., Young, Charles D., Miller, Bill C., Bebee, Melvin G.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Edwards, Christopher O.
• Application Number:
  US07/371,906
• Time in Patent Office: 364 Days
• Field of Search: 370/76, 370/124, 370/50, 375/38, 455/62
• US Class Current: 370/436
• CPC Class Codes: H04B 7/18532 Arrangements for managing transmission, i.e. for transporting data or a signalling message
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713

Abstract

An adaptive TDMA (time division multiple access) communication system is illustrated which dynamically maintains potentially different frequencies between nodes of the communication system using a process of communicating the quality of received signals between the nodes and storing this information so that an optimum frequency band can be selected whereby whenever signal quality deteriorates, an alternate frequency can be selected to provide continued communications. An embodiment of the system spans both high frequency (HF) and very high frequency (VHF) to establish the communications through atmospheric induced refractions (reflections) beyond line of sight between directly communicating nodes of the system. Further, the system uses frequency hopping both for signal transmission security and for node identification. When a node is traffic idle and also on a periodic maintenance basis, frequency bands other than the traffic frequency are analyzed for potential future use.

Claims

1. A node for use in a HF multinode network wherein communication between other nodes in a set of N nodes is subject to natural vagaries such as fading and absorption and wherein each node in the network establishes communication with another node in the set of nodes in a probe mode, exchanges data in a traffic mode and maintains communication in a maintenance mode comprising, in combination:

N time slot multiplexing transmitter first means;

N time slot multiplexing receiver second means;

memory storage third means; and

control means, connected to said first, second and third means, comprising,

fourth means for transmitting a predetermined set of probe frequencies to a given further node at the next one of a predetermined set of times by the given further node,

fifth means for receiving a predetermined set of probe frequencies from the given further node and recording the quality of each probe frequency of the set received,

sixth means for transmitting the recorded quality of the received probe frequencies to the node from which they were received,

seventh means for storing the quality of probe signals received by other nodes which exceed predetermined minimum requirements for use in determining the frequencies to be used in communication with each assigned other node during further communications with that node,

selection eighth means for selecting the frequencies attributed to the highest quality signal of those stored by said seventh means to be used in a communication mode with a given node wherein the frequencies selected may be different for each other node being communicated with,

detection ninth means for switching to the transmission mode for communication with each node in the set of nodes after successful selection of a transmission frequency exceeding the predetermined minimum requirements,

switching tenth means for temporarily substituting a maintenance mode of communication with each node in the set of nodes, with whom successful communications have been established, on a periodic basis to establish to desirability of using a frequency other than the present for the transmission mode,

eleventh means for communicating a transmission mode frequency change sequence to a given node in the set of nodes upon establishment by said tenth means that such a change is will provide a desirably higher quality level of communication, and

monitoring twelfth means to return the system to a probe mode for a given node in the set of nodes when transmission errors exceed a predetermined value.

2. The method of establishing and maintaining radio communication between any two nodes in a spaced apart network of T nodes comprising, the steps of:

establishing a set of internode connections where each node is directly connected only to an assigned set N of other nodes where N is less than T and where communication to nodes outside the set N is via the set N;

independently establishing a transmission frequency with each node of the set of nodes by sending a predetermined set of trial transmission frequencies at predetermined times as part of a probe mode, in accordance with information stored in each node of the network, storing quality information relative each received signal and transmitting all previously dynamically stored signal quality information at each subsequent trial transmission frequency;

storing the information received as to the quality of various transmitted frequency signals and independently selecting the frequency having the highest quality to be used in a transmission mode with each of the nodes in the set where the frequencies sent and received may be different for each node of the set N and may be different for sending and receiving with respect to a given pair of nodes in the set N;

normally transmitting packets of information to any other node in the network of T nodes via one of the set of N nodes in a transmission mode;

periodically trading packets of information in a maintenance mode, interspersed with the packets of the transmission mode, concerning any stored information pertaining to the connectivity of any node with any other node, whereby each node builds and maintains a dynamic table of information for the purpose of determining the best next node in the path toward the ultimate destination; and

transmitting alternate frequency signals, from said predetermined set of trail frequencies, during maintenance mode time periods for continuously updating stored signal quality information whereby the transmission frequency automatically can be changed in accordance with predetermined parameters without having to revert to the probe mode.

3. The method of establishing radio communication between any two nodes in a spaced apart finite network of T nodes comprising, the steps of:

establishing a set of internode connections where each node is directly connected only to an assigned finite set N of other nodes where N is less than T and where communication to nodes outside the set N is via the set N;

independently establishing a transmission frequency with each node of the set of nodes by sending a predetermined set of trial transmission frequencies at predetermined times as part of a probe mode, in accordance with information stored in each node of the network, storing quality information relative each received signal and subsequently transmitting all previously stored signal quality information at each subsequent trial transmission frequency in a further set of transmissions; and

storing at each node the information received as to the quality of various transmitted frequency signals and selecting from information stored at each node the frequency having the highest quality to be used in a transmission mode with each of the nodes in the set where the frequencies sent and received may be different for each node of the set N and may be different for sending and receiving with respect to a given pair of nodes in the set N.

4. The method of maintaining radio communication between any two nodes in a set of N nodes in a spaced apart network of T nodes comprising, the steps of:

storing information as to the quality of various transmitted frequency signals between each of T nodes in a network;

establishing a set of internode connections where each node is directly connected only to an assigned set N of other nodes where N is much less than T and where communication to nodes outside the set N is via the set N;

normally transmitting packets of information to any other node in the network of T nodes via one of the set of N nodes in a transmission mode where the transmission frequency may be different for each one of the set of N nodes and may be different for sending and receiving with respect to a given pair of nodes in the set N;

periodically trading packets of information in a maintenance mode, interspersed with the packets of the transmission mode, concerning any stored information pertaining to various frequency signal quality between any node and any other directly connected node, whereby each node maintains a dynamic table of information; and

transmitting alternate frequency signals during maintenance mode time periods for continuously updating stored signal quality information.

5. A node for greater than line of sight communication with another node where the communication is subject to natural vagaries such as fading and absorption comprising, in combination:

N time slot multiplexing transmitter first means;

N time slot multiplexing receiver second means;

memory storage third means; and

control means, connected to said first, second and third means, comprising,

fourth means for transmitting a predetermined set of probe frequencies to the other node at a time expected by the given other node,

fifth means for receiving a predetermined set of probe frequencies from the other node and recording the quality of each probe frequency of the set received,

sixth means for transmitting the recorded quality of the received probe frequencies received to the node from which they were received,

seventh means for storing the quality of probe signals received by the other node which exceed predetermined minimum values for use in determining the frequencies to be used in communication with each said other node during further communications with the node,

selection eighth means for selecting the frequencies attributed to the highest quality signal of those stored by said seventh means to be used in a communication mode with a given node,

detection ninth means for switching to the transmission mode for communication with said other node after successful selection of a transmission frequency exceeding the predetermined minimum requirements,

switching tenth means for temporarily substituting a maintenance mode of communication with said other node, on a periodic basis, to establish the desirability of using a frequency other than the present for the transmission mode,

eleventh means for communicating a transmission mode frequency change sequence upon establishment by said tenth means that such a change will provide a desirably higher quality level of communication, and

monitoring twelfth means to return the node to a probe mode whenever transmission errors exceed a predetermined value.

6. A method of establishing and maintaining VHF beyond line of sight radio communication between two transceiver nodes, comprising the steps of:

establishing an initial transmission frequency in each direction between the nodes by sending a predetermined set of trial transmission frequencies at predetermined times as part of a probe mode, in accordance with information stored in each node, storing quality information relative each received signal and transmitting all previously stored signal quality information at each subsequent trial transmission frequency;

storing the information received as to quality of various transmitted frequency signals and selecting the frequency having the highest quality to be used in a transmission mode with the other node where the frequencies sent and received may be different;

normally transmitting packets of user information to said other node in a transmission mode;

periodically trading packets of information in a maintenance mode, interspersed with the packets of the transmission mode, concerning any stored information pertaining to the connectivity of either node, whereby each node builds and maintains a dynamic table of connectivity information; and

transmitting alternate frequency signals during transmission mode time periods for continuously updating stored signal quality information whenever it is determined that there is no user traffic to be transmitted.

7. The method of maintaining communications between two transmitter/receiver units operating in a packet message mode comprising the steps of:

time interspersing maintenance transmission trial data rate packets with message packets where the data rate of the maintenance packets differs from that of the current message packets;

measuring the quality of the maintenance packets of various trial data rates received;

transmitting the measured values of the quality of received trial data rate maintenance packets to the unit sending same; and

adjusting the data rate of the message packets to a maximum value while maintaining at least a given minimum message quality.

8. The method of maintaining beyond line of sight VHF radio communication between two spaced apart nodes comprising, the steps of:

storing information as to the quality of various transmitted frequency signals between each of the nodes;

normally transmitting packets of information in a transmission mode where the transmission frequency may be different for sending and receiving;

periodically trading packets of information in a maintenance mode, interspersed with the packets of the transmission mode, concerning any stored information pertaining to various frequency signal quality, whereby each node maintains a dynamic table of information; and

transmitting alternate frequency signals during maintenance mode time periods for continuously updating stored signal quality information.

9. A node for greater than line of sight communication with another node where the communication is subject to natural vagaries such as fading and absorption comprising, in combination:

N time slot multiplexing transmitter first means;

N time slot multiplexing receiver second means;

memory storage third means; and

control means, connected to said first, second and third means, comprising,

fourth means for transmitting a predetermined set of probe frequencies to the other node at a time expected by the given other node,

fifth means for receiving a predetermined set of probe frequencies from the other node and recording the quality of each probe frequency of the set received,

sixth means for transmitting the recorded quality of the received probe frequencies received to the node from which they were received,

seventh means for storing the quality of probe signals received by the other node which exceed predetermined minimum requirements for use in determining the frequencies to be used in communication with each said other node during further communications with that node,

selection eighth means for selecting the frequencies attributed to the highest quality signal of those stored by said seventh means to be used in a communication mode with a given node,

detection ninth means for switching to the transmission mode for communication with said other node after successful selection of a transmission frequency exceeding the predetermined minimum requirements,

switching tenth means for temporarily substituting a maintenance mode of communication with said other node, on a periodic basis, to establish to desirability of using a data rate other than the present for the transmission mode, and

eleventh means for communicating a transmission mode data rate change upon establishment by said tenth means that such a change will be desirable.

10. The method of automatically establishing communication between two nodes in a communications network where each of said two nodes has stored information of the trial frequencies stored internally by the other node of said two nodes and further has information stored internally as to the time, relative an established reference, that a set of trial frequencies will be transmitted comprising the steps of:

a. transmitting each frequency of a first set of trial frequencies at predetermined relative times to the other node of said two nodes in a probe phase;

b. recording the quality of any signals received at expected times during the probe phase;

c. transmitting the signal quality recorded results of each trial frequency attempted in step (b) at each of the frequencies used in step (a) in a response phase;

d. storing signal quality information, as to the best quality signals of any remote node received signals, received from the other node of said two nodes as a result of the transmissions of step (a), at each of the receive signal frequencies previously used in step (b) as part of the response phase;

e. transmitting acknowledgement messages to and receiving acknowledgement messages from the other node of said two nodes for establishing the traffic frequency each node will use in communicating with the other of said two nodes in a verify phase each receiving node thereby establishing the frequency that the other node shall use in its communicating transmissions; and

f. repeating steps (a) to (e) for new sets of stored trial frequencies if either node fails to receive signals of sufficient quality to sustain communication in step (b).

11. A node for use in a HF multinode network wherein communication between other nodes in a set of nodes is subject to natural vagaries such as fading and absorption and wherein each node in the network establishes communication with another node in the set of nodes in a probe mode, exchanges data in a traffic mode and maintains communication in a maintenance mode comprising, in combination:

N time slot multiplexing transmitter first means;

N time slot multiplexing receiver second means;

memory storage third means; and

control means, connected to said first, second and third means, comprising,

fourth means for transmitting a predetermined set of probe frequencies to a given further node at a time expected by the given further node,

fifth means for receiving a predetermined set of probe frequencies from the given further node and recording the quality of each probe frequency of the set received,

sixth mean for transmitting the recorded quality of the received probe frequencies to the node from which they were received,

seventh means for storing the quality of probe signals received by other nodes which exceed predetermined minimum requirements for use in determining the frequencies to be used in communication with each assigned other node during further communications with that node,

selection eigth means for selecting the frequencies attributed to the highest quality signal of those stored by said seventh means to be used in a communication mode with a given node wherein the frequencies selected may be different for each other node being communicated with,

detection ninth means for switching to the transmission mode for communication with each node in the set of nodes after successful selection of a transmission frequency exceeding the predetermined minimum requirements,

switching tenth means for temporarily substituting a maintenance mode of communication with each node in the set of nodes, with whom successful communications have been established, on a periodic basis to establish the desirability of using a data rate other than the present for the transmission mode,

eleventh means for communicating a transmission mode data rate change sequence to a given node in the set of nodes upon establishment by said tenth means that such a change will provide a desirably higher quality level of communication, and

monitoring twelfth means to return the system to a probe mode for a given node in the set of nodes whenever transmission errors exceed a predetermined value and cannot be corrected by changing transmission parameters.

12. A node for use in a HF multinode network wherein communication between other nodes in a set of nodes is subject to natural vagaries such as fading and absorption and wherein each node in the network establishes communication with another node in the set of nodes in a probe mode, exchanges data in a traffic mode and maintains communication in a maintenance mode comprising, in combination:

N time slot multiplexing transmitter first means;

N time slot multiplexing receiver second means;

memory storage third means; and

control means, connected to said first, second and third means, comprising,

fourth means for transmitting a predetermined set of probe frequencies to a given further node at a time expected by the given further node,

fifth means for receiving a predetermined set of probe frequencies from the given further node and recording the quality of each probe frequency of the set received,

sixth means for transmitting the recorded quality of the received probe frequencies to the node from which they were received,

seventh means for storing the quality of probe signals received by other nodes which exceed predetermined minimum requirements for use in determining the frequencies to be used in communication with each assigned other node during further communications with that node,

selection eighth means for selecting the frequencies attributed to the highest quality signal of those stored by said seventh means to be used in a communication mode with a given node wherein the frequencies selected may be different for each other node being communicated with,

detection ninth means for switching to the transmission mode for communication with each node in the set of nodes after successful selection of a transmission frequency exceeding the predetermined minimum requirements,

switching tenth means for temporarily substituting a maintenance mode of communication with each node in the set of nodes, with whom successful communications have been established, on a periodic basis to establish the desirability of using a frequency other than the present for the transmission mode,

eleventh means for communicating a transmission mode frequency change sequence to a given node in the set of nodes upon establishment by said tenth means that such a change will provide a desirably higher quality level of communication, and

monitoring twelfth means to return the system to a probe mode for a given node in the set of nodes when transmission errors still exceed a predetermined value after attempts have been made to reduce same by changing system transmission parameters.

13. The method of establishing radio communication between any two nodes in a spaced apart network of T nodes for the transmission of data packets comprising, the steps of:

initiating transmissions from a transmitter node to a given receiver node based on a predetermined set of trial transmission frequencies sent at predetermined times as part of a probe mode where said set of trail transmission frequencies and predetermined times are known to said receiver node;

storing information relative the quality of each signal received of the set of trial transmission frequencies at the receiver node;

determining at the receiver node which of the received signals is best suited for the transmission of data packets based on the stored information; and

transmitting instruction information from the receiver node to the transmitter node as to the frequency to be used by the transmitter during the transmission of data packets whereby the frequency used by a transmitter in each of the two nodes is selected by and controlled by the other of the two nodes.

14. The method of selecting a usuable communication channel frequency from a range of frequencies including HF (high frequency) and VHF (very high frequency) as part of a procedure for establishing and maintaining beyond line of sight radio communication between two transceiver nodes, comprising the steps of:

establishing an initial transmission frequency in each direction between a pair of nodes by sending a predetermined set trial transmission frequencies covering the range of HF and VHF as part of a probe mode;

storing quality information relative each signal received as part of the probe mode procedure;

transmitting stored signal quality information to the other node of said pair of nodes along with an indication of the frequency the other node is to use for normal communications as part of a verify mode, the result being that the frequencies sent and received, by one node of the pair of nodes for normal communication of data packets, may be different;

normally transmitting packets of user information to said other node in a transmission mode;

periodically trading packets of information in a maintenance mode, interspersed with the packets of the transmission mode, concerning any stored information pertaining to the connectivity of either node, whereby each node builds and maintains a dynamic table of connectivity information; and

transmitting alternate frequency signals during transmission mode time periods for continuously updating stored signal quality information whenever it is determined that there is no user traffic to be transmitted.

15. The method of selecting a usable communication channel frequency from a range of frequencies including HF (high frequency) and VHF (very high frequency) as part of a procedure for establishing and maintaining beyond line of sight radio communication between two transceiver nodes, comprising the steps of:

establishing an initial transmission frequency in each direction between a pair of nodes by sending a predetermined set of trial transmission frequencies covering the range of HF and VHF as part of a probe mode;

storing quality information relative each signal received as part of the probe mode procedure; and

transmitting stored signal quality information to the other node of said pair of nodes along with an indication of the frequency that the other node is to use for normal communications as part of a verify mode, the result being that the frequencies sent and received, by one node of the pair of nodes for normal communication of data packets, may be different, and the frequencies sent by each node of the pair is selected and controlled by the receiving node.

16. The method of selecting a usable data rate and communication channel frequency from a range of frequencies including HF (high frequency) and VHF (very high frequency) as part of a procedure for establishing and maintaining beyond line of sight radio communication between two transceiver nodes, comprising the steps of:

establishing an initial transmission frequency in each direction between a pair of nodes by sending a predetermined set of trial transmission frequencies having data occuring at a given rate and covering the range of HF and VHF as part of a probe mode;

storing BER (bit error rate) signal quality information relative each signal received as part of the probe mode procedure; and

transmitting stored signal quality information to the other node of said pair of nodes along with an indication of the data rate that the other node is to use for normal communications as part of a response/verify mode, the result being that the data rates sent and received, by one node of the pair of nodes for normal communication of data packets, may be different, and the frequencies sent by each node of the pair is selected and controlled by the receiving node.