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.
Claims18
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.
A method for dynamically selecting a multi-dimensional signal constellation for a data frame having a plurality of symbols, the symbols having a fixed number of specified possible energy levels and a maximum average power value, the method comprising:
- computing a minimum distance required between symbol signal points to achieve a preselected performance level;
- identifying a first smallest available energy level greater than or equal to said minimum distance;
- assigning the first smallest available energy level as a first signal point;
- searching each one of the plurality of symbols in the data frame to identify a next smallest available energy level greater than or equal to the minimum distance higher than a previously assigned signal point;
- assigning the next smallest available energy level as a next signal point;
- iteratively repeating the steps of searching, and assigning the next smallest available energy level while the average power is less than the maximum average power value and one or more of the available energy levels remain unassigned and transmitting digital data with said constellation.
A communication system for dynamically selecting a multi-dimensional signal constellation for a data frame having a plurality of symbols, the symbols having a fixed number of specified possible energy levels and a maximum average power value, the system comprising:
- means for computing a minimum distance required between symbol signal points to achieve a preselected performance level;
- means for identifying a first smallest available energy level greater than or equal to said minimum distance;
- means for assigning the first smallest available energy level as a first signal point;
- means for searching each one of the plurality of symbols in the data frame to identify a next smallest available energy level greater than or equal to the minimum distance higher than a previously assigned signal point;
- means for assigning the next smallest available energy level as a next signal point;
- means for iteratively repeating the steps of searching, and assigning the next smallest available energy level while the average power is less than the maximum average power value and one or more of the available energy levels remain unassigned and means for transmitting digital data with said constellation.
Dependencies are inferred from the claim text.