Method and apparatus for determining the log-likelihood ratio with precoding

In a wireless communications system, a method of determining soft decision symbols based on received modulation symbols, the method comprising:

• determining a first subset of signal points for which a bit is equal to a first value;
• determining a second subset of signal points for which the bit is equal to a second value, wherein the first and second subsets are signal points from an expanded signal constellation;
• determining the probability that the bit is equal to the first value or the second value as a function of the received signal point;
• and
• determining the soft decision symbol based on the probability that the bit is equal to the first value or the second value.

In a wireless communication system, an apparatus for recovering transmitted data, the apparatus comprising:

• means for receiving a plurality of signal points, the signal point comprising a plurality of modulation symbols from a plurality of coded bits;
• means for determining a first subset of signal points for which a bit is equal to a first value;
• means for determining a second subset of signal points for which the bit is equal to a second value, wherein the first and second subsets are signal points from an expanded signal constellation;
• means for determining the probability that the bit is equal to the first value or the second value as a function of the received signal point;
• and
• means for determining a soft decision symbol based on the probability that the bit is equal to the first value or the second value.

In a wireless communication system, an apparatus for recovering transmitted data, the apparatus comprising:

• a receiver configured to receive a plurality of modulation symbols from a plurality of coded bits;
• a processor coupled to the receiver, the processor configured to perform the following method steps:
• determining a first subset of signal points for which a bit is equal to a first value;
• determining a second subset of signal points for which the bit is equal to a second value, wherein the first and second subsets are signal points from an expanded signal constellation;
• determining the probability that the bit is equal to the first value or the second value as a function of the received signal point;
• and
• determining a soft decision symbol based on the probability that the bit is equal to the first value or the second value.

A computer readable medium containing instructions for controlling a computer system to perform a method, the method comprising:

• determining a first subset of signal points for which a bit is equal to a first value;
• determining a second subset of signal points for which the bit is equal to a second value, wherein the first and second subsets are signal points from an expanded signal constellation;
• determining the probability that the bit is equal to the first value or the second value as a function of the received signal point;
• and
• determining a soft decision symbol based on the probability that the bit is equal to the first value or the second value.