Patent ID: 7173973

Claim:
A receiver for receiving data and pilot symbols simultaneously over multiple channels comprising: at least one antenna; a demodulator coupled to an output of the antenna for demodulating received symbols in accordance with a multi-carrier transmission technique, a channel estimator coupled to the demodulator for estimating a channel of a multi-carrier system using received pilot symbols; a storage medium for storing a multi-level signal constellation defining C points, of which at least one point defines a first level and a plurality of points define a second level, and a minimum inter-level distance between points is based on a maximized minimum difference between conditional probability distributions; and a mapper coupled to the demodulator and to the storage medium for converting the demodulated symbols to a plurality of data signals that each alone or in combination correspond to a constellation point wherein the demodulator determines a maximum likelihood conditional probability distribution of the received symbols and wherein the conditional probability distribution is p â¡ ( X i â˜ S i , H ^ i ) = â¢ E H ~ i â¢ { p â¡ ( X i â˜ S i , H ^ i , H ~ i ) } = â¢ 1 Ï€ â¡ ( Ïƒ 2 + Ïƒ E 2 â¢ ï˜… S i ï˜† 2 ) â¢ exp â¢ { - ï˜… X i - S i â¢ H ^ i ï˜† 2 Ïƒ 2 + Ïƒ E 2 â¢ ï˜… S i ï˜† 2 } such that the detector maximizes over at least two possible values for S i to find a transmitted symbol wherein S i comprises a transmitted signal vector, Ä¤ i comprises a channel estimate matrix, X i comprises a received signal vector, {tilde over (H)} i comprises an estimation error matrix at an i th frequency bin, E {tilde over (H)} i is an error estimation matrix, and Ïƒ E is the estimation variance at each frequency bin.