| 摘要 |
A trellis decoder identifies the closest points from each coset in a four dimensional trellis decoder by reading a received point and determining upper and lower threshold values in a signal constellation to define a decode region within the constellation. The dimensions of the decode region are based on the number of bits of information in the received signal. The decoder translates the received point in four directions to provide four image points. Any image point that transitions outside the constellation decode region is mapped into the decode region to ensure that the four imaged points are within the decode region of the constellation. For each of the cosets, bit extraction is then performed to find the closest point to the received point. Once the closest coset points are identified, the trellis decoder performs a maximum likelihood sequence estimation using the Viterbi algorithm to determine the received sequence. Advantageously, the trellis decoder of the present invention provides a fast technique for determining the closest points to a received point from each coset.
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