Apparatus and method for the synchronization of data in a bit stream
First Claim
1. A method for detecting the beginning of data in a bit stream, wherein the bit stream comprises sequences of a preamble, byte synch and data, wherein the byte synch comprises an EOP bit sequence which identifies the end of the preamble and the beginning of the data, said method comprising the steps of:
- determining a frequency and phase related to the bit stream for clock synchronization;
wherein said step of determining is completed within an initial portion of a pattern of bits in the preamble, said pattern being a repetition of instances of a specific bit string having a bit with a first value and one or more bits having a different second value;
performing EOP searches to detect a first occurrence of said EOP bit sequence in said bit stream, wherein at least one of said EOP searches commences at a first bit position within said bit stream, said first bit position separated by a second bit position from a third bit position at which a next EOP search is commenced, wherein no EOP search commences at said second bit position; and
determining where the data begins in the bit stream using an EOP bit sequence detected in one of said EOP searches;
wherein said step of performing EOP searches allows an EOP bit sequence to be used which is shorter than a bit sequence which would be required if an EOP search were commenced at said second bit position.
0 Assignments
0 Petitions
Accused Products
Abstract
In the system of the present invention, the system includes a pre-synchronizer to eliminate the need for examining every possible substring preceding the EOP (end of preamble) mark in order to detect the EOP. For the case where autocorrelation techniques are used to provide error synchronization error tolerance, this results in a much shorter EOP, since it is possible to find shorter EOPs which do not falsely synchronize prior to the arrival of the true EOP. In particular, the preamble is utilized to perform pre-synchronization. Once pre-synchronization has been achieved, the search for the EOP can be focused on a subset of all possible substrings as opposed to prior techniques which looked at all possible substrings. The resultant system solves the problem with less logic and more error tolerance.
-
Citations
17 Claims
-
1. A method for detecting the beginning of data in a bit stream, wherein the bit stream comprises sequences of a preamble, byte synch and data, wherein the byte synch comprises an EOP bit sequence which identifies the end of the preamble and the beginning of the data, said method comprising the steps of:
-
determining a frequency and phase related to the bit stream for clock synchronization; wherein said step of determining is completed within an initial portion of a pattern of bits in the preamble, said pattern being a repetition of instances of a specific bit string having a bit with a first value and one or more bits having a different second value; performing EOP searches to detect a first occurrence of said EOP bit sequence in said bit stream, wherein at least one of said EOP searches commences at a first bit position within said bit stream, said first bit position separated by a second bit position from a third bit position at which a next EOP search is commenced, wherein no EOP search commences at said second bit position; and determining where the data begins in the bit stream using an EOP bit sequence detected in one of said EOP searches; wherein said step of performing EOP searches allows an EOP bit sequence to be used which is shorter than a bit sequence which would be required if an EOP search were commenced at said second bit position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 17)
-
-
9. A method for detecting the beginning of data in a bit stream, wherein the bit stream comprises sequences of a preamble, byte synch and data, wherein the byte synch comprises an EOP bit sequence having bits of a first value and bits of a different second value which identifies the end of the preamble and the beginning of data, said method comprising the steps of:
-
determining a frequency and phase related to the bit stream for synchronizing a clock for the system; wherein said step of determining is completed using an initial portion of a pattern of bits in the preamble by synchronizing the clock based on a predetermined bit position in each instance of a specific bit sequence repeated in the pattern of bits in the preamble; searching, following said step of determining, for said EOP bit sequence in said bit stream at a location of said predetermined bit position in additional instances of said specific bit sequence occurring beyond said initial portion, said predetermined bit position indicative of a possible start of an occurrence of said EOP bit sequence, wherein said step of searching includes searching for only the bits of said EOP bit sequence having said first value; detecting the existence of said EOP bit sequence to determine the start of data which begins after said EOP bit sequence.
-
-
10. An apparatus for use in locating data in a string of bits comprising a preamble, an EOP bit sequence having bits of a first value and bits of a different second value, and the data, said data occurring after the EOP bit sequence, said apparatus comprising:
-
means for determining a frequency and phase related to the string of bits by detecting a predetermined bit position in instances of a specific bit sequence repeated in the preamble, wherein said means for determining is used for synchronizing a clock for said apparatus to said frequency and phase, the clock being synchronized in an initial portion of the preamble to occurrences of said predetermined bit position; EOP detector means for determining a likelihood of whether a substring in said string of bits, beginning at a first bit position in any one of said instances and having a bit length equal to said EOP bit sequence, represents said EOP bit sequence wherein said EOP detector means examines less than all bit positions of the substring in determining a likelihood that the substring represents said EOP bit sequence; pre-synchronizer means for (a) locating additional instances of said specific bit sequence in said preamble beyond said initial portion, and (b) activating said EOP detector means for one or more of said additional instances, wherein less than every bit position is used as said first position. - View Dependent Claims (11, 12, 13, 14, 15, 16)
-
Specification