Transmission Over a Multiple Input Multiple Output Broadcast Channel (Mimo-Bc)

摘要

A Multiple Input Multiple Output (MIMO) communication system 1 has a transmitter for transmitting signals over a MIMO Broadcast Channel (MIMO-BC) 6. Data for communication to respective receivers 4 ₁ , 4 _K-1 , 4 _K is encoded by encoding stages 10 ₁ , . . . , 10 _K-1 , 10 _K in a selected order by selecting codewords c₁, . . . c_K-1, c_K from codebooks C₁, . . . C_K-1, C_K of a nested lattice code. Dither adders 11 ₁ , . . . , 11 _K-1 , 11 _K are arranged to add a respective dither d₁ . . . , d_K-1, d_k to the selected codewords c₁, . . . c_K-1, c_K. Quantising stages 12 ₁ , . . . , 12 _K-1 , 12 _K each perform respective quantising operations modLambda_S,1, . . . , modLambda_S,K-1, modLambda_S,K using the shaping lattice Lambda_S of the nested lattice code. Quantised signals u₁, . . . , u_K-1, u_K of data encoded earlier in the selected order are output to feedbackward filter stages 14 ₁ , . . . , 14 _K-1 for filtering the codewords c₁, . . . c_K-1, c_K of data encoded later in the selected order before they are quantised by the quantising stages 12 ₁ , . . . , 12 _K-1 using a feedbackward filter F_b. At the receivers 4 ₁ , 4 _K-1 , 4 _K feedforward filter stages 15 ₁ , . . . , 15 _K-1 , 15 _K filter received signals y₁, . . . , y_K-1, y_K by applying a feedforward filter F_f. A combination of the feedbackward and feedforward filters F_b, F_f is substantially equivalent to a single filter for extracting the signals representing the data intended to be communicated to the receivers 4 ₁ , 4 _K-1 , 4 _K with a minimum mean squared error, but the feedforward filter F_f can be applied by each of the receivers 4 ₁ , . . . , 4 _K-1 , 4 _K without knowledge of signals y₁, . . . , y_K-1, y_K received by the other receivers 4 ₁ , . . . , 4 _K-1 , 4 _K.