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Precoding scheme for transmitting data using optimally-shaped constellations over intersymbol-interference channels

  • US 5,388,124 A
  • Filed: 06/12/1992
  • Issued: 02/07/1995
  • Est. Priority Date: 06/12/1992
  • Status: Expired due to Term
First Claim
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1. A digital communication apparatus that transmits binary data from a transmitter to a receiver over a channel, the apparatus comprising:

  • means for receiving a stream of input binary data,a shaping encoder means for mapping a block of data from the stream of input binary data to a point in a constellation of dimension N having a constituent d-dimensional constellation, the constellation point being represented as a concatenation of i constituent points each from the constituent d-dimensional constellation where i and d are integers;

    whereini) boundary of the constituent d-dimensional constellation is chosen to minimize the peak energy for a given predetermined data transmission rate and a given predetermined d-dimensional constellation expansion ratio, and boundary of the constellation approximating a boundary that maximizes shaping gain;

    ii) the mapping from the block of data to the constellation point is invertible and is performed by;

    (a) partitioning the constituent d-dimensional constellation into t groups of points where t is an integer, each group containing equal number of points;

    (b) assigning an integer length to each point in a group, the length being a non-decreasing function of the average energy of all the points in that group;

    (c) assigning a unique index between 1 and t to each of the t groups;

    (d) assigning a total length to each constellation point, the total length being sum of the lengths of its i constituent points;

    (e) ordering all the constellation points such that;

    i) constellation point with smaller total length precedes constellation point with larger total length, and. ii) for two constellation points with same total length, order depends on indices of groups that their i constituent points belong to,(f) assigning a unique binary address to each constellation point depending on its position in set of ordered constellation points; and

    (g) mapping the block of data to a constellation point that has same address as a binary number represented by the block of data.

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