Self-Supporting Simplex Packets

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.

1 . A method of encoding a packet at a transmitter, comprising:
 creating a header of the packet;   creating a body of the packet that includes information that is to be transmitted by the transmitter; and   encoding the packet for transmission using a spreading code,   wherein the header is configured to include a sequence of bit transitions that enables a receiver to determine a start of the packet without prior knowledge of the particular sequence of bit transitions.   
     
     
         2 . The method of  claim 1 , wherein the sequence of bit transitions corresponds to an identifier of the transmitter. 
     
     
         3 . The method of  claim 1 , wherein the sequence of bit transitions is configured to enable the receiver to determine a polarity of bits in the packet. 
     
     
         4 . The method of  claim 1 , wherein the sequence of bit transitions is configured to include a minimum number of transitions to enable synchronization of the receiver to the packet. 
     
     
         5 . The method of  claim 1 , wherein:
 the header of the packet includes a plurality of identifiers; and   the identifiers are configured to include a minimum number of transitions to enable synchronization of the receiver to the packet.   
     
     
         6 . The method of  claim 1 , including providing an error correcting sequence within the packet, wherein the error correcting sequence is configured to include a minimum number of transitions to enable synchronization of the receiver to the packet. 
     
     
         7 . The method of  claim 6 , wherein the error correcting sequence is configured to enable the receiver to determine an end of the packet. 
     
     
         8 . The method of  claim 1 , wherein the sequence of bit transitions is based on a self-correcting code. 
     
     
         9 . The method of  claim 1 , wherein the body of the packet is encoded so as to include a minimum number of transitions to enable synchronization of the receiver to the packet. 
     
     
         10 . The method of  claim 1 , wherein the packet includes a polarity-independent encoding having a maximum span of non-transitions. 
     
     
         11 . A method of decoding a packet that does not include a preamble of known bit values, comprising:
 identifying a header of the packet that includes a sequence of bit transitions, 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.   
     
     
         12 . The method of  claim 11 , wherein the sequence of bit transitions identifies a transmitter of the packet. 
     
     
         13 . The method of  claim 11  further comprising identifying a body of the packet that includes information that has been transmitted by the transmitter. 
     
     
         14 . The method of  claim 11  further comprising despreading the packet using a spreading code. 
     
     
         15 . The method of  claim 11 , wherein the end of packet sequence corresponds to an error correction code. 
     
     
         16 . The method of  claim 11 , including determining a polarity of bits in the packet based on the sequence of bit transitions. 
     
     
         17 . The method of  claim 11 , including synchronizing a demodulation of the packet based on the sequence of bit transitions. 
     
     
         18 . A transmitter comprising:
 a packet creator that is configured to:
 create a header of a packet that includes a sequence of bit transitions that enables a receiver to determine a start of the packet without prior knowledge of the particular sequence of bit transitions; 
 create a body of the packet that includes information that is to be transmitted by the transmitter; and 
 a spread-spectrum encoder that is configured to encode the packet for transmission using a spreading code. 
   
     
     
         19 . The transmitter of  claim 18 , wherein the sequence of bit transitions corresponds to an identifier of the transmitter. 
     
     
         20 . The transmitter of  claim 18 , wherein the sequence of bit transitions includes a minimum number of transitions to enable synchronization of the receiver to the packet. 
     
     
         21 . The transmitter of  claim 18 , wherein the packet creator is configured to create an error correcting sequence that includes a minimum number of transitions to enable synchronization of the receiver to the packet. 
     
     
         22 . A receiver comprising:
 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; 
 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. 
   
     
     
         23 . The receiver of  claim 22 , wherein the sequence of bit transitions identifies a transmitter of the packet. 
     
     
         24 . The receiver of  claim 22  further comprising a receive buffer that is configured to receive a composite signal. 
     
     
         25 . The receiver of  claim 22  further comprising a phase detector that is configured to detect a code-phase of a message that does not include a sequence of known bit values. 
     
     
         26 . The receiver of  claim 22 , wherein the demodulator is further configured to identify a body of the packet that includes information that has been transmitted by the transmitter. 
     
     
         27 . The receiver of  claim 22 , wherein the demodulator is configured to determine a polarity of bits in the packet based on the sequence of bit transitions. 
     
     
         28 . A system comprising:
 a spread-spectrum receiver, and   a plurality of spread spectrum transmitters,   wherein each transmitter is configured to transmit packets using a common spreading code, and each packet includes a header that includes a sequence of bit transitions that enables a receiver to determine a start of the packet without prior knowledge of the particular sequence of bit transitions.