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 41, 4K-I, 4K is encoded by encoding stages 10l, ..., 10k-1 10K in a selected order by selecting codewords CIV"CK-I, CK from codebooks CI,...CK-I, CK of a nested lattice code. Dither adders 11 u .", HK-U 11K are arranged to add a respective dither d1..., dk-1, dk to the selected codewords C1,...Ck-1, Ck. Quantising stages 12i,..., 12K-I, 12&Kgr; each perform respective quantising operations modAs 1, ..., modAs,k-1,, modals using the shaping lattice As of the nested lattice code. Quantised signals u1,..., UK:-I, UK of data encoded earlier in the selected order are output to feedbackward filter stages 14i5 ..,, 14K-I for filtering the codewords C1,...Ck-.i, Ck;- of data encoded later in the selected order before they are quantised by the quantising stages 12i, ..., 12K. 1 using a feedbackward filter Fb. At the receivers 41, 4K-i, 4K feedforward filter stages 151, ..., 15&Kgr; 1 15K filter received signals y1,..,y&kgr;-u y&Kgr; by applying a feedforward filter Ff. A combination of the feedbackward and feedforward filters F, Ff is substantially equivalent to a single filter for extracting the signals representing the data intended to be communicated to the receivers 41, 4K.b 4K with a minimum mean squared error, but the feedforward filter Ff can be applied by each of the receivers 4], ,.,, 4K-b 4K without knowledge of signals y1,..,y &Kgr-1, y&Kgr; received by the other receivers 41, ..., 4K-b 4K-