Transmission apparatus, transmission method, and wireless communication system for orthogonal cover code (occ) generation and occ mapping

A Multiple Input Multiple Output (MIMO) transmission method, comprising:

• generating, by a base station, reference signals by spreading elements with four groups of different orthogonal code sequences derived from a set of Walsh code sequences, each group of orthogonal code sequences including four orthogonal sequences, wherein the orthogonal code sequences correspond to transmission layers and each of the orthogonal code sequences has a length of four, and
• transmitting, by the base station, the reference signals,
• wherein the four groups of orthogonal code sequences include a first group, a second group in which the orthogonal code sequences are represented by mirroring of the orthogonal code sequences in the first group, a third group, and a fourth group in which the orthogonal code sequences are represented by mirroring of the orthogonal code sequences in the third group, —
• wherein the first group of orthogonal code sequences are used to spread elements for reference signals mapped to a first frequency resource, the second group of orthogonal code sequences are used to spread elements for reference signals mapped to a second frequency resource, the third group of orthogonal code sequences are used to spread elements for reference signals mapped to a third frequency resource, and the fourth group of orthogonal code sequences are used to spread elements for reference signals mapped to a fourth frequency resource, and
• wherein the first and second frequency resources are adjacent frequency resources in frequency resource elements within a resource block used for reference signal transmission and the third and fourth frequency resources are other adjacent frequency resources in the frequency resource elements within the resource block used for reference signal transmission.

A method for receiving Multiple Input Multiple Output (MIMO) communication, the method comprising:

• receiving reference signals spread by four groups of different orthogonal code sequences derived from a set of Walsh code sequences, each group of orthogonal code sequences including four orthogonal sequences, wherein the orthogonal code sequences correspond to transmission layers and each of the orthogonal code sequences has a length of four;
• wherein the four groups of orthogonal code sequences include a first group, a second group in which the orthogonal code sequences are represented by mirroring of the orthogonal code sequences in the first group, a third group, and a fourth group in which the orthogonal code sequences are represented by mirroring of the orthogonal code sequences in the third group,
• wherein the first group of orthogonal code sequences are used to spread elements for reference signals mapped to a first frequency resource, the second group of orthogonal code sequences are used to spread elements for reference signals mapped to a second frequency resource, the third group of orthogonal code sequences are used to spread elements for reference signals mapped to a third frequency resource, and the fourth group of orthogonal code sequences are used to spread elements for reference signals mapped to a fourth frequency resource,
• wherein the first and second frequency resources are adjacent frequency resources in frequency resource elements within a resource block used for reference signal transmission and the third and fourth frequency resources are other adjacent frequency resources in the frequency resource elements within the resource block used for reference signal transmission, and
• despreading the received reference signals.