Method and an arrangement for receiving a symbol sequence
First Claim
1. A method of detecting a symbol sequence in asynchronous reception, using a known digital sequence, comprising the steps of:
- a) dividing the known digital sequence into at least two separate segments;
b) allocating a number of specific threshold values equal to the number of said segments;
c) correlating said received symbol sequence and the first segment of the known digital sequence, therewith to obtain a first correlation value;
d) storing said first correlation value at least when said value exceeds a first of said threshold value;
e) setting a certain first time point in accordance with the length of the second segment;
f) correlating said received symbol sequence and the second segment of the known digital sequence at said first time point, therewith to obtain a second correlation value;
g) adding said second correlation value to the stored first correlation value so as to obtain a first summation value; and
h) comparing said first summnation value with a second of said threshold values, wherewith an indication that said symbol sequence has been detected is obtained when said sum exceeds said second threshold value.
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Abstract
The invention relates to synchronizing in communication systems by using a sequential correlation technique. A digital sequence known to the receiver, a so-called signature, is allocated a plurality of segments. The segments are correlated, segment for segment, in a correlator (300) which is equally as long as the segment. The segments may have the same or different bit patterns. When a first segment is received in the correlator (300) and the correlation value of this segment exceeds an associated threshold value, the segment is accepted as received and is saved in a memory (308) in response to a signal from the control unit (311). A timer (319) is set to a time point that corresponds to the length of the segments. There is then correlated a second segment whose correlation value on the signal from the timer (319) is added (304) to the value stored in the memory (308). If the sum exceeds an associated threshold value, the sum is stored in the memory (308). Detection continues in this way. When the sum of the correlation values of all segments have exceeded the threshold value of the last segment, there is generated a sync. time pulse signal (Ts). Should a threshold value not be exceeded, it is assumed that a wrong signature has been received, and detection of the first segment is recommenced.
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Citations
22 Claims
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1. A method of detecting a symbol sequence in asynchronous reception, using a known digital sequence, comprising the steps of:
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a) dividing the known digital sequence into at least two separate segments; b) allocating a number of specific threshold values equal to the number of said segments; c) correlating said received symbol sequence and the first segment of the known digital sequence, therewith to obtain a first correlation value; d) storing said first correlation value at least when said value exceeds a first of said threshold value; e) setting a certain first time point in accordance with the length of the second segment; f) correlating said received symbol sequence and the second segment of the known digital sequence at said first time point, therewith to obtain a second correlation value; g) adding said second correlation value to the stored first correlation value so as to obtain a first summation value; and h) comparing said first summnation value with a second of said threshold values, wherewith an indication that said symbol sequence has been detected is obtained when said sum exceeds said second threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An arrangement for detecting a symbol sequence in asynchronous reception, using a known digital sequence, comprising:
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at least one correlator which functions to correlate the received symbol sequence and the segments of the known digital sequence, therewith to obtain first and second correlation values; at least one memory for storing the first correlation value, at least when said correlation value exceeds a first threshold value; at least one adder which functions to add the second correlation value to said stored correlation value, such as to obtain a first summation value; at least one timer for setting a certain time point; and a control unit which functions to compare the first correlation value with the first of said threshold values for setting said timer, and for comparison of the first summation value with a second of said threshold values, wherewith an indication is obtained that said symbol sequence has been detected when the first summation value exceeds said second threshold value. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification