Radio access method, radio base station and radio terminal

A radio base station, which is for use in a radio system including a radio terminal and a radio base station having an array antenna with a plurality of antenna elements and capable of transmitting directional multibeam from said array antenna of said radio base station to said radio terminal in a state where a different orthogonal code series is allocated to each of a plurality of directional beams, said radio base station comprising:

• a transmitting unit that transmits directional multibeam of a downlink physical channel to said radio terminal;
• a receiving unit that receives orthogonal code series identification information, transmitted from said radio terminal, identifying an orthogonal code series determined as having a high autocorrelation out of the directional multibeam transmitted from said transmitting unit, the orthogonal code series identification information is superimposed on information used for retransmission control between said radio base station and said radio terminal;
• and
• a determination unit that determines an orthogonal code series for the downlink physical channel to said radio terminal based on the orthogonal code series identification information received by said receiving unit.

A radio terminal, which is for use in a radio system including a radio terminal and a radio base station having an array antenna with a plurality of antenna elements and capable of transmitting directional multibeam from said array antenna of said radio base station to said radio terminal in a state where a different orthogonal code series is allocated to each of a plurality of directional beams, said radio terminal comprising:

• a receiving unit that receives directional multibeam of downlink physical channel from said radio base station;
• a correlation determination unit that obtains each of correlation between the orthogonal code series of the directional multibeam received by said receiving unit and orthogonal code series stored in said radio terminal, and determining an orthogonal code series having the highest autocorrelation;
• and
• a transmitting unit that transmits orthogonal code series identification information identifying the orthogonal code series determined by said correlation determination unit, to said radio base station by superimposing the orthogonal code series identification information on information used for retransmission control between said radio base station and said radio terminal.