Link adaptation method using a polar modulation constellation

Method for adapting a link between an emitter and a receiver, the emitter grouping together binary data to be transmitted in the form of blocks having a length m=log2M, and transforming said blocks into complex symbols via digital modulation to transmit them over a transmission channel, said symbols belonging to a polar-modulation constellation C(M,Γ) of order M consisting of Γ=2n equidistant concentric circles where m>n+1 and n>1, each of the concentric circles carrying the same plurality M/Γ of symbols, the angular distribution of said symbols being uniform and identical on each of the concentric circles, two successive symbols on a circle corresponding to two words of m bits having a Hamming distance equal to 1 and two symbols, in the same angular direction, belonging to two successive concentric circles, corresponding to two words of m bits having a Hamming distance equal to 1, said method for adapting a link being characterized in that:

• the emitter transmits (410) a sequence of control symbols to the receiver via the transmission channel;
• the receiver derives (420), from the control symbols received, an estimation of the variance in the additive noise as well as an estimation of the variance in the phase noise affecting the transmission channel and sends back (430) to the emitter, via an indicator of state of the channel, the estimated variances;
• the emitter reads (440) in a table stored in a memory, on the basis of the values of said variances and a target bit error rate, an order M as well as a number Γ of concentric circles compatible with a target bit error rate;
• the emitter transmits (450), over the link, said binary data via a modulation constellation of order M and having a number of concentric circles, Γ, thus read in the table.