Self-supporting simplex packets

• US 8,275,080 B2
• Filed: 11/07/2007
• Issued: 09/25/2012
• Est. Priority Date: 11/17/2006
• Status: Active Grant

• Current Assignee: Comtech Mobile Datacom Corporation (Comtech Telecommunications Corporation)
• Original Assignee: Comtech Mobile Datacom Corporation (Comtech Telecommunications Corporation)
• Inventors: Jordan, Luis G.
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Malek, Leila
• Application Number:
  US11/936,784
• Publication Number:
  US 20080117952A1
• Time in Patent Office: 1,784 Days
• Field of Search: 375/130, 375/131, 375/133, 375/134, 375/135, 375/136, 375/137, 375/140, 375/141, 375/145, 375/146, 375/147, 375/149, 375/354, 375/357, 375/369, 375/372, 375/373, 375/374, 370/395.62, 370/507, 455/265, 702/89, 713/375, 713/400
• US Class Current: 375/354
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 3/0608 Detectors therefor, e.g. correlators, state machines
• CPC Class Codes: H04L 1/0042 Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 1/0079 Formats for control data H04L1/16 takes precedence; training sequences H04L25/00 and H04L27/00

Abstract

Existing message fields and/or message parameters are configured to facilitate the packet and message synchronization and decoding tasks that conventionally rely upon a known bit sequence in each packet, thereby eliminating the need for a predefined message preamble in each packet. In example embodiments, the unique identifier of each transmitter is structured to facilitate determination of bit polarity and the start of each packet; packet sequence numbers use an unconventional counting sequence to assure synchronizing bit transitions; and so on. Other techniques, such as the use of run-length limited (RLL) message encoding, or 8b/10b encoding, to assure within-packet bit transitions, are also used to enhance clock synchronization and proper header location determination.

Claims

1. A method of decoding a packet that does not include a preamble of known bit values, comprising:

at a device configured to decode the packet;

despreading the packet using a spreading code,

identifying a header of the packet that includes a sequence of bit transitions,

identifying a body of the packet that includes information that has been transmitted by a transmitter, wherein identifying the header includes identifying a start of the packet based on the sequence of bit transitions,

determining a first bit transition rate based on transitions in the header,

identifying an end of packet sequence,

determining a second bit transition rate based on transitions in the end of packet sequence, and

estimating a bit transition rate for decoding bits in the body of the packet based on the first and second bit transition rates.

2. The method of claim 1, wherein the sequence of bit transitions identifies a transmitter of the packet.

3. The method of claim 1, wherein the end of packet sequence corresponds to an error correction code.

4. The method of claim 1, including determining a polarity of bits in the packet based on the sequence of bit transitions.

5. The method of claim 1, including synchronizing a demodulation of the packet based on the sequence of bit transitions.

6. A receiver comprising:

a receive buffer that is configured to receive a composite signal,

a phase detector that is configured to detect a code-phase of a message that does not include a sequence of known bit values,

a demodulator that is configured to;

identify a header of the packet that includes a sequence of bit transitions,

identify a start of the packet based on the sequence of bit transitions,

identify a body of the packet that includes information that has been transmitted

by a transmitter,

determine a first bit transition rate based on the bit transitions in the header,

identify an end of packet sequence,

determine a second bit transition rate based on transitions in the end of packet sequence, and

determine a bit transition rate for decoding bits in the body of the packet based on the first and second bit transition rates.

7. The receiver of claim 6, wherein

the sequence of bit transitions identifies a transmitter of the packet.

8. The receiver of claim 6, wherein

the demodulator is configured to determine a polarity of bits in the packet based on the sequence of bit transitions.