Packet start detection using check bit coding
OwnerSung-Moon Yanginventor
Life of this patent
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Abstract
In a digital radio system, data is transmitted in packet form. A check or parity bit is used to determine whether any errors have occurred between data transmission and demodulation. That same check bit is used to identify its location in a packet. From that check bit location, it is then possible to identify the starting and ending data bits in a packet and to correctly interpret the packet data.
Claims28
In a digital data system transmitting digital data in data packets, a method for identifying the check bit location within said data packets, by counting syndrome bits, comprising the steps of:
- a. selecting a test check bit location in said data packets;
- b. producing a new check bit from said data packets;
- using said digital data in said packet without said test check bit;
- c. comparing said test check bit at said test check bit location with said new check bit;
- d. producing a syndrome bit indicative of said comparison;
- e. counting said syndrome bits;
- f. comparing said syndrome bit count with a good threshold and a bad threshold;
- g. identifying said test check bit location as correct when said syndrome bit count exceeds said good threshold;
- or
- h. identifying said test check bit location as incorrect when said syndrome bit exceeds said bad threshold and shifting said test check bit location relative to said data stream and repeating steps a. to h.
A system for transmitting digital data in packets and for identifying the check bit location within said packets, by counting syndrome bits, comprising:
- a. means for selecting a test check bit location in said data packets;
- b. means connected to said means for selecting, for using said packet data without said test check bit for producing a new check bit from said data steam;
- c. said means connected to said means for producing a new check bit, including means for comparing said test check bit at said test check bit location with said new check bit
- d. said means connected to said means for producing a new check bit, including means for producing a syndrome bit indicative of said comparison;
- e. said means connected to said means for producing a syndrome bit, including means for counting said syndrome bits;
- f. said means connected to said means for counting said syndrome bits, including means for comparing said syndrome bit count with a first threshold and with a second threshold;
- g. said means connected to said means for counting said syndrome bits, including means for identifying said test check bit location as correct when said syndrome bit count exceeds said first threshold and identifying said test check bit location as incorrect when said syndrome bit count exceeds said second threshold;
- and
- h. means connected to said means for identifying for shifting said test check bit location in said data packet and said means for selecting, selecting a new test check bit location in response to said means for identifying said test check bit location as incorrect when said syndrome bit count does exceeds said second threshold.
A method for using the location of a check bit in a digital data stream transmitted in data packets, to establish the boundaries of said packets by counting syndrome bits, comprising the steps of:
- a. selecting a test check bit location in the data packets and defining an image packet with reference to said test check bit location;
- b. using the data within said image packet except for said test check bit to produce a new check bit;
- c. comparing said test check bit with said new check bit;
- d. producing syndrome bits indicative of said comparison and counting said syndrome bits;
- e. comparing said syndrome bit count with a good threshold and a bad threshold identifying said test check bit location as correct when said syndrome bit count exceeds said good threshold and identifying said test check bit location as incorrect when said syndrome bit count exceeds said bad threshold and shifting said test check bit location in said data stream and repeating the steps a. through e.
Dependencies are inferred from the claim text.