Patent ID: 7903752
Filing Date: 2011-03-08
Classification: H04L

Abstract:
1. Sphere decoding method for maximum likelihood receiver intended to receive PPM-PAM symbols from a plurality P of sources, each source emitting a flow of PPM-PAM symbols at M positions and at M′ modulation amplitudes, P PPM-PAM symbols emitted simultaneously by the P sources being represented by a point (a) of the modulation product constellation in a space of the signals transmitted 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, the signal received (x) by said receiver being transformed into a point representative (z) of this signal, referred to as the received point, in the space of the transmitted signals, said method determining the point of the product constellation the closest (â opt ) to the received point within a sphere of given quadratic radius, characterised in that, for each layer of rank p: (a) one carries out a ZF-DFE equalisation of the signal received in said layer considering the PPM-PAM symbols estimated in the P-p previous layers, referred to as layers higher than the layer p; (b) one selects a PPM-PAM symbol of this layer: (c) this contribution is added to those obtained for the previous layers to obtain a sum of contributions (σ the steps (a), (b), (c) being repeated until one attains the lowest layer; and one updates the quadratic radius of the sphere and said closest point if said sum of contributions is lower than the quadratic radius of the sphere.