Terminal apparatus, base station, radio communication method and program storage medium

A communication method comprising:

• receiving a signal from a base station;
• estimating a state of a channel based on a received signal to obtain an estimated state value of the channel;
• providing a codebook including a plurality of channel state values;
• acquiring index of search number representing a number of candidates to be selected from among the channel state values in the codebook for a correlation calculation with the estimated state value;
• selecting candidates for which the correlation calculation with the estimated state value should be performed from among the channel state values in the codebook according to the index of search number;
• calculating a correlation between the estimated state value and each of selected candidates;
• selecting a candidate having a highest correlation value from among the selected candidates;
• and
• reporting a selected candidate to the base station.

A program storage medium storing a computer program for causing a computer to execute instructions to perform the steps of:

• receiving a signal from a base station;
• estimating a state of a channel based on a received signal to obtain an estimated state value of the channel;
• reading out a codebook including a plurality of channel state values from a codebook storage;
• acquiring index of search number representing a number of candidates to be selected from among the channel state values in the codebook for a correlation calculation with the estimated state value;
• selecting candidates for which the correlation calculation with the estimated state value should be performed from among the channel state values in the codebook according to the index of search number;
• calculating a correlation between the estimated state value and each of selected candidates;
• selecting a candidate having a highest correlation value from among the selected candidates;
• and
• reporting a selected candidate to the base station.

A base station for communicating with a terminal apparatus, the terminal apparatus estimating a state of a channel to obtain an estimated state value of the channel and calculating a correlation between the estimated state value and each of candidates selected from a codebook which includes channel state values to detect a candidate having a high correlation with the estimated state value, comprising:

• a quality measuring unit configured to measure quality of a channel between the base station and the terminal apparatus;
• a storage configured to store a base station side codebook having same contents as the codebook of the terminal apparatus;
• an index acquisition unit configured to acquire an index of the candidate detected by the terminal apparatus from the terminal apparatus;
• a selecting unit configured to select a channel state value having an acquired index from the base station side codebook;
• a weighted signal generation unit configured to multiply a transmission signal to the terminal apparatus by a weight depending on a selected channel state value to generate a weighted signal;
• a transmission unit configured to transmit the weighted signal to the terminal apparatus;
• an index of search number determining unit configured to determine index of search number representing a number of the candidates to be selected from the codebook in the terminal apparatus, based on measured quality of the channel;
• and
• a reporting unit configured to report the index of search number to the terminal apparatus.

A communication method performed by a base station which communicates with a terminal apparatus, the terminal apparatus estimating a state of a channel to obtain an estimated state value of the channel and calculating a correlation between the estimated state value and each of candidates selected from a codebook which includes channel state values to detect a candidate having a high correlation with the estimated state value, comprising:

• measuring quality of a channel between the base station and the terminal apparatus;
• providing a storage configured to store a base station side codebook having same contents as the codebook of the terminal apparatus;
• acquiring an index of the candidate detected by the terminal apparatus from the terminal apparatus;
• selecting a channel state value having an acquired index from the base station side codebook;
• multiplying a transmission signal to the terminal apparatus by a weight depending on a selected channel state value to generate a weighted signal;
• transmitting the weighted signal to the terminal apparatus;
• determining index of search number representing a number of the candidates to be selected from the codebook in the terminal apparatus, based on measured quality of the channel;
• and
• reporting the index of search number to the terminal apparatus.

A program storage medium storing a computer program for causing a base station which communicates with a terminal apparatus, the terminal apparatus estimating a state of a channel to obtain an estimated state value of the channel and calculating a correlation between the estimated state value and each of candidates selected from a codebook which includes channel state values to detect a candidate having a high correlation with the estimated state value, to execute instructions the steps of:

• measuring quality of a channel between the base station and the terminal apparatus;
• reading out a base station side codebook identical to the codebook of the terminal apparatus, from a codebook storage;
• acquiring an index of the candidate detected by the terminal apparatus from the terminal apparatus;
• selecting a channel state value having an acquired index from the base station side codebook;
• multiplying a transmission signal to the terminal apparatus by a weight depending on a selected channel state value to generate a weighted signal;
• transmitting the weighted signal to the terminal apparatus;
• determining index of search number representing a number of the candidates to be selected from the codebook in the terminal apparatus, based on measured quality of the channel;
• and
• reporting the index of search number to the terminal apparatus.