Synchronization for entry to a network in a frequency hopping communication system

• US 5,121,408 A
• Filed: 10/16/1989
• Issued: 06/09/1992
• Est. Priority Date: 10/16/1989
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Cai, Khiem V., O'Connor, Roger J.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/422,257
• Time in Patent Office: 967 Days
• Field of Search: 380/34, 380/38, 380/39, 380/46, 380/48, 375/1, 375/40, 375/100, 375/115, 370/50, 455/51, 455/56, 455/71, 455/76, 455/161, 455/165, 455/166
• US Class Current: 375/134
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04B 1/7156 Arrangements for sequence synchronisation
• CPC Class Codes: H04B 2001/71563 Acquisition

Abstract

Synchronization of a frequency hopping transceiver to a network by embedding synchronization codes in the pseudo-random frequency hopping transmission sequence. A receiver is implemented with a frequency detector and a correlator to generate a correlator signal in response to the synchronization codes in the pseudo-random frequency hopping transmission sequence. Detection of a peak in the correlator signal is indicative of synchronization of the receiver with the network. The network entry synchronization scheme is such that, when two transceivers A and B are communicating, a third unnetworked transceiver C extracts the hidden network entry code pattern from the A-B transmission in order to enter the network. As a part of the communication between the two transceivers A and B, transceiver A transmits a known pattern as a hidden part of the communication which allows transceiver C to enter the A-B network. This hidden code pattern permits rapid synchronization and correction of large initial time errors, and permits correction of time drift from then on.

Claims

1. A frequency hopping communication transmitter comprising:

a controller adapted to generate a sequence of control signals for each of a plurality of frames of communication information, wherein the sequence of control signals includes at least one synchronization control signal pseudo-randomly interleaved with a plurality of data control signals;

a frequency synthesizer coupled to the controller and adapted to generate a sequence of pseudo-random frequency hopped signals including at least one synchronization frequency signal randomly interleaved with a plurality of data frequency signals in response to the at least one synchronization control signal and plurality of data control signals; and

a transmitter coupled to the frequency synthesizer and adapted to transmit the synchronization frequency signal and plurality of data frequency signals as an interleaved pseudo-random frequency hopping communication signal.

2. A frequency hopping communication receiver comprising:

a preprocessor adapted to generate a sequence of frequency signals in response to an applied pseudo-random frequency hopping communication signal comprising at least one synchronization frequency signal and a plurality of data frequency signals;

a frequency detector coupled to the preprocessor and adapted to generate synchronizting frequency signals in response to detection of a frequency signal having a predetermined frequency;

a correlator coupled to the frequency detector and adapted to generate a synchronizing signature signal in response to a sequential combination of synchronizing frequency signals; and

a synchronizing clock coupled to the correlator and adapted to generate a synchronizing clock signal in synchronization with the synchronizing signature signal, which synchronizing signature signal is adapted to synchronize the receiver with transmission of a transmitter from which the applied pseudo-random frequency hopping communication signal was generated.

3. The frequency hopping communication receiver of claim 2 wherein:

the applied pseudo-random frequency hopping communication signal comprises two synchroniztion frequency signals;

the frequency detector includes a first detector circuit adapted to generate a first synchronizing frequency signal in response to detection of a first frequency signal having a first selected frequency included in the sequence of frequency signals, and adapted to generate a second synchronizing frequency signal in response to detection of a second frequency signal having a second selected frequency included in the sequence of frequency signals;

the correlator includes a first correlator processor adapted to generate a first synchronizing signature signal in response to a sequential combination of the first synchronizing frequency signal and a second correlator processor adapted to generate a second synchronizing signature signal in response to a sequential combination of the second synchronizing frequency signal; and

the synchronizing clock is adapted to generate the synchronizing clock signal in synchronization with a selected one of the first and second synchronizing signature signals.

4. A frequency hopping communication system that provides for preamble-less network entry synchronization, said system comprising:

a controller adapted to generate a sequence of control signals for each of a plurality of frames of communication information, wherein the sequence of control signals includes at least one synchronization control signal interleaved with a plurality of data control signals;

a frequency synthesizer coupled to the controller and adapted to generate a sequence of pseudo-random frequency hopped signals including at least one synchronization frequency signal and a plurality of data frequency signals in response to the at least one synchronization control signal and plurality of data control signals; and

a transmitter coupled to the frequency synthesizer and adapted to transmit the at least one synchronization frequency signal and plurality of data frequency signals as an interleaved pseudo-random frequency hopping communication signal;

a receiver electromagnetically coupled to the transmitter and adapted to generate a sequence of frequency signals in response to an applied pseudo-random frequency hopping communication signal comprising at least one synchronization frequency signal and a plurality of data frequency signals;

a frequency detector coupled to the preprocessor and adapted to generate synchronizing frequency signals in response to detection of a frequency signal having a predetermined frequency;

a correlator coupled to the frequency detector and adapted to generate a synchronizing signature signal in response to a sequential combination of synchronizing frequency signals; and

a synchronizing clock coupled to the correlator and adapted to generate a synchronizing clock signal in synchronization with the synchronizing signature signal, which synchronizing signature signal is adapted to synchronize the receiver with transmission of the transmitter.

5. In a networked frequency hopping communication system, a method of synchronizing network entry comprising the steps of:

generating a frame of interleaved pseudo-random frequency hopping signals comprising a frame synchronization signal pseudo-randomly interleaved with a plurality of data signals;

transmitting the frame of interleaved pseudo-random frequency hopping signals;

receiving the transmitted frame of interleaved pseudo-random frequency hopping signals;

separating the frame synchronization signal from the interleaved pseudo-random frequency hopping signals;

synchronizing a clock signal in response to the frame synchronization signal in order to synchronize to the network.

6. The method of claim 5 wherein the steps of separating the frame synchronization signal from the interleaved pseudo-random frequency hopping signals and synchronizing the clock comprises the steps of:

processing the interleaved pseudo-random frequency hopping signals to detect the frame synchronization signal; and

correlating the frame synchronization signal with the clock signal to synchronize to the network.

7. The method of claim 6 further comprising the step of:

generating a plurality of data signals in response to the received pseudo-randomly interleaved frequency hopping signals and the synchronized clock signal.

8. In a frequency hopping communication system, a method of synchronizing network entry comprising the steps of:

generating a frame of interleaved frequency hopping signals including a frame synchronization signal pseudo-randomly interleaved with a plurality of data signals;

transmitting the frame of interleaved frequency hopping signals to a remote location;

receiving the frame of interleaved frequency hopping signals at the remote location;

separating the frame synchronization signal from the frame of interleaved frequency hopping signals;

synchronizing remote location clock signals to the frame synchronization signal to generate a frame synchronized clock signal that synchronize the remote location to the transmitted frame synchronization signal and hence synchronize the remote location to the network.

9. The method of claim 8 further comprising the step of:

generating a plurality of data signals in response to the received pseudo-randomly interleaved frequency hopping signals and the frame synchronized clock signals.

10. In a frequency hopping communication transmitter comprising a controller for generating a sequence of control signals for each of a plurality of frames of communication information, a frequency synthesizer coupled to the controller for generating a sequence of frequency signals, and a transmitter coupled to the frequency synthesizer for transmitting the sequence of frequency signals, wherein the improvement comprises:

means for pseudo-randomly interleaving a frame synchronization signal with a plurality of data signals in the sequence of frequency signals transmitted by the transmitter.

11. In a frequency hopping communication receiver comprising a receiver for generating a sequence of input frequency signals in response to receipt of a frequency hopping communication signal, a frequency detector coupled to the receiver for generating output frequency signals in response to the sequence of input frequency signals, wherein the improvement comprises:

correlator means coupled to the frequency detector for generating synchronizing signature signals in response to a sequential combination of the output frequency signals; and

a synchronizing clock coupled to the correlator for generating a synchronizing clock signal in synchronism with the synchronizing signature signals that synchronizes the receiver to a transmitter that communicated the frequency hopping communication signal.

12. In a networked frequency hopping communication system, a method of synchronizing network entry comprising the steps of:

generating a frame of interleaved pseudo-random frequency hopping signals comprising a frame synchronization signal pseudo-randomly interleaved with a plurality of data signals;

transmitting the frame of interleaved pseudo-random frequency hopping signals;

receiving the transmitted frame of interleaved pseudo-random frequency hopping signals;

separating the frame synchronization signal from the interleaved pseudo-random frequency hopping signals by processing the interleaved pseudo-random frequency hopping signals to detect the frame synchronization signal; and

synchronizing a clock signal in response to the frame synchronization signal by correlating the frame synchronization signal with the clock signal to synchronize to the network.

13. The method of claim 12 further comprising the step of:

generating a plurality of data signals in response to the received pseudo-randomly interleaved frequency hopping signals and the synchronized clock signal.

14. In a frequency hopping communication system, a method of synchronizing network entry comprising the steps of:

generating a frame of interleaved frequency hopping signals including a frame synchronization signal pseudo-randomly interleaved with a plurality of data signals;

transmitting the frame of interleaved frequency hopping signals to a remote location;

receiving the frame of interleaved frequency hopping signals at the remote location;

separating the frame synchronization signal from the frame of interleaved frequency hopping signals;

generating a plurality of data signals in response to the received pseudo-randomly interleaved frequency hopping signals and the frame synchronized clock signals; and

synchronizing remote location clock signals to the frame synchronization signal to generate a frame synchronized clock signal that synchronize the remote location to the transmitted frame synchronization signal and hence synchronize the remote location to the network.