Method of selecting a PCM modem signal constellation in relation to channel impairments
AssigneeTexas Instruments Incorporated
InventorsNirmal C. Warke, Murtaza Ali
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Abstract
Disclosed are methods of selecting a multi-dimensional signal constellation in relation to impairments in a communication system having a data frame consisting of a fixed number of symbols. The methods make use of impairments detected from a Digital Impairment Learning sequence (DIL) and channel impairments, such as POE and SNR. Signal points are individually assigned to each symbol in a data frame in relation to that symbol's particular digital impairments and a pre-selected minimum performance level and maximum power constraints.
Claims27
For a communication system using a data frame consisting of a fixed number of symbols, a method of selecting a signal constellation in relation to impairments in the system comprising the steps of:
- detecting impairments to each of said symbols from a Digital Impairment Learning sequence (DIL);
- assigning signal points individually to said symbols in relation to said impairments and a preselected minimum performance level.
A method for transmitting digital data within a communication system having a data frame defined to include a fixed number of symbols having a fixed number of specified possible energy levels, and a maximum average power value, the method comprising the steps of:
- (a) assembling a signal constellation by individually assigning signal points corresponding to each symbol in said data frame by the steps of:
- (i) computing a minimum distance required between symbol signal points to achieve a preselected performance level;
- (ii) receiving a Digital Impairment Learning (DIL) sequence;
- (iii) using said DIL sequence, identifying distinguishable energy levels from among said possible energy levels;
- (iv) searching each of said symbols in said data frame to identify the smallest available energy level greater than or equal to said minimum distance;
- (v) assigning as a first signal point, said smallest available energy level identified in step (a)(iv);
- (vi) searching each of said symbols in said data frame to identify the smallest available energy level greater than or equal to said minimum distance higher than a previously assigned signal point;
- (vii) assigning as a next signal point said smallest available energy level identified in step (a)(vi);
- (iix) while the average power is less than the maximum average power value and one or more of said available energy levels remain unassigned, repeating steps (a)(vi) and (a)(vii);
- and
- (b) transmitting digital data with said signal constellation.
Dependencies are inferred from the claim text.