Likelihood calculating method and communication method

A likelihood calculating method, which is used in a receiver having information data of plural signal points based on predefined data which consist of plural bits transmitted from a transmitter, comprising:

• receiving a reception signal from the transmitter;
• selecting a first signal point which, among the plural signal points, is the shortest distance from the reception signal in a phase plane;
• calculating a square of a first distance in the phase plane between the first signal point and the reception signal, and calculating a square of a second distance in the phase plane between a second signal point corresponding to a signal obtained by inverting one of bits of the first signal point and the reception signal;
• and
• calculating the difference between the square of the first distance and the square of the second distance and using the result of calculation as a likelihood of the bit in the reception signal.

A likelihood calculating method, which uses a receiver having information data of plural signal points based on predefined data which consist of plural bits transmitted from a transmitter and the receiver comprising a first and a second reception antennas, comprising:

• receiving reception signals from the transmitter by each of the first and second reception antennas;
• selecting a first signal point which, among the plural signal points, has the smallest sum of a distance from a reception signal of the first reception antenna in the phase plane and a distance from a reception signal of the second reception antenna in the phase plane, with respect to each of the first and second reception antennas;
• calculating a first distance sum of the distance in the phase plane between the reception signal of the first reception antenna and the first signal point, and the distance in the phase plane between the reception signal of the second reception antenna and the first signal point;
• calculating a second distance sum of the distance in the phase plane between a second signal point corresponding to a signal obtained by inverting one of bits of the first signal point and the reception signal of the first reception antenna, and the distance in the phase plane between the second signal point and the reception signal of the second reception antenna;
• and
• calculating the difference between the first and second distance sums and using the result of calculation as a likelihood indicative of certainty of the bit in the reception signal.

A likelihood calculating method, which uses a receiver having information data of plural signal points based on predefined data which consist of plural bits transmitted from a transmitter and the receiver comprising a first and a second reception antennas, comprising:

• receiving reception signals from the transmitter by each of the first and second reception antennas;
• selecting a first signal point which, among the plural signal points, has the smallest sum of a square of a distance from a reception signal of the first reception antenna in the phase plane and a square of a distance from a reception signal of the second reception antenna in the phase plane, with respect to each of the first and second reception antennas;
• calculating a first sum of the square of the distance in the phase plane between the reception signal of the first reception antenna and the first signal point, and the square of the distance in the phase plane between the reception signal of the second reception antenna and the first signal point;
• calculating a second sum of the square of the distance in the phase plane between a second signal point corresponding to a signal obtained by inverting one of bits of the first signal point and the reception signal of the first reception antenna, and the square of the distance in the phase plane between the second signal point and the reception signal of the second reception antenna;
• and
• calculating the difference between the first and second sums and using the result of calculation as a likelihood indicative of certainty of the bit in the reception signal.

A likelihood calculating method, which uses a receiver having information data of plural signal points based on predefined data which consist of plural bits transmitted from a transmitter, comprising:

• receiving a reception signal from the transmitter;
• selecting a first signal point which, among the plural signal points, is the shortest distance from the reception signal in a phase plane;
• calculating a first distance in the phase plane between the first signal point and the reception signal, and calculating a second distance in the phase plane between a second signal point corresponding to a signal obtained by inverting one of bits of the first signal point and the reception signal;
• calculating the difference between the first and second distances and using the result of calculation as a likelihood indicative of certainty of the bit in the reception signal;
• and
• changing one or more of a transmission power, a modulating method and a coding rate of the transmitter on the basis of an average of the likelihoods of the bits of the reception signal.