Non-uniform constellations

摘要

A method for efficiently generating an optimum non-uniform constellation is described. The method comprises the step of performing a first process, comprising the steps of: obtaining 201 a first constellation C_Last defined by one or more parameter values; and generating a second constellation based on the first constellation using a second process. The second process comprises: obtaining a set of candidate constellations 205, wherein the set of candidate constellations comprises the first constellation and one or more modified constellations, wherein each modified constellation is obtained by modifying the parameter values defining the first constellation, possibly using a step size variation to the parameter values 203, 205; determining the performance of each candidate constellation according to a predetermined performance measure, e.g. capacity 207; selecting 209 the candidate constellation having the best performance as the second constellation C_best. The first process further comprises the steps of: determining a difference between the first constellation, C_Last and the second constellation C_best i.e. to see if the constellation has converged; and if the difference is greater than a threshold amount, repeating the first process using C_best as input 213. A further iteration may be performed with e.g. a half step size 219 until a minimum step size is reached 217. A second embodiment involves finding an optimum constellation with maximum capacity for a given SNR or Ricean factor.