Decoder with maximum likelihood for multi-user system with pulse position modulation and amplitude.

摘要

Decoding method sphere for receiving maximum likelihood intended to receive PPM symbols PAM from a plurality P of sources, each source emitting a flow of PPM symbols-PAM to M positions and M 'modulation amplitudes, represented P PPM symbols PAM simultaneously emitted by the P sources at a point (a) of the modulation product constellation in a space of transmitted signals of dimension MP decomposed into P layers, each layer representing the M possible modulation positions and in each of these positions the M 'possible amplitudes of a PPM-PAM symbol emitted by this source, transforming the signal (x) received by said receiver at a point (z) representative of this signal, called the received point, in the space of the transmitted signals , said method determining the point of the product constellation closest (âopt) to the received point within a sphere of radius ty quadratic or, wherein, for each layer of rank p: (a) ZF-DFE of the signal received in said layer equalization is performed taking account of the PPM-PAM symbols estimated in the Pp previous layers, referred to above the layer p; (B) a PPM-PAM symbol from this layer is selected: (b1) by classifying, for each PPM of said layer position list (Lp m) of the PAM symbols in this position, based on the contributions made to the quadratic point received and retaining for each list the PAM symbol making the lowest contribution list named champion distance; (B2) by selecting the PPM position (pos (p)) making the lowest contribution (dp) and selecting as PPM symbol-PAM (pos (p) (m-pos (p))) the champion of the list in the position thus determined; (C) the contribution is added to those obtained for the previous layers to obtain a sum of contributions (p); repeating steps (a), (b), (c) until the lowest layer is reached; and the quadratic radius of the sphere and said closest point are updated if said sum of contributions is lower than the quadratic radius of the sphere.