Browsing by Author "Chen Sau-Gee"

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Cyclic comparison method for low-density parity-check decoder
(2011-06-21)
Hung Jui-Hui
;
Hung Jui-Hung
;
Chen Sau-Gee
A cyclic comparison method for an LDPC decoder. The nth element of the input k elements, wherein n=1, . . . , k, is sequentially removed by the corresponding comparator to obtain k first level sequences. Next, pairs of two elements selected from the k elements are used to form k second level sequences. The preceding step is repeated k×┌log2(k−1)┐ times to obtain k output results. Either of one first level sequences and one output results contains (k−1) elements. The first level sequences are compared with the output results to determine whether they are identical. If they are identical, the process stops. If they are not identical, the abovementioned step is repeated to obtain new output results. The cyclic comparison method of the present invention needs only k×┌log2(k−1)┐ comparisons to obtain output results. Thus, the present invention can reduce the number of basic operations and can apply to any input number.
Set-cyclic comparison method for low-density parity-check decoder
(2011-05-17)
Hung Jui-Hui
;
Hung Jui-Hung
;
Chen Sau-Gee
The present invention discloses a set-cyclic comparison method for an LDPC (Low-Density Parity-Check) decoder, which applies to a CNU (Check Node Unit) or a VNU (Variable Node Unit). In the systematized method of the present invention, all the input elements are initialized to obtain a matrix. Based on the symmetry of the matrix and the similarity between the rows of the matrix are sequentially formed different sets respectively corresponding to the horizontally-continuous elements having the maximum iteration number in the horizontal and vertical directions, the symmetric non-continuous non-boundary elements, and the boundary elements plus the end-around neighboring elements in the same row. The present invention applies to any input number. Via the large intersection between the compared sets, the present invention can effectively reduce the number of comparison calculations and greatly promote the performance of an LDPC decoder.
Symbol time synchronization method for OFDM systems
(2012-07-10)
Chin Wen-Long
;
Chen Sau-Gee
A symbol time synchronization method for OFDM systems is disclosed. The invention presents a joint maximum-likelihood (ML) synchronization method for symbol time offset (STO) in OFDM systems. The method is developed in frequency domain under time-variant multipath channels. By analyzing the received frequency-domain data, a mathematical model for the joint effects of symbol time offset (STO), carrier frequency offset (CFO) and sampling clock frequency offset (SCFO) is derived. The results are used to formulate a log-likelihood function of two consecutive symbols. The joint estimation's method is robust, because it exhibits high performances in high mobility and time-variant multipath fading channels.