Patent ID: 8908490

Claim:
A base station in a wireless communication system, the base station comprising: a layer mapper to perform mapping of a codeword to a layer; at least two precoders to perform precoding of mapped symbols sequentially, using a precoding matrix; and two or more antennas to transmit a wireless signal comprising the precoded symbol, wherein the most internal precoder from among the precoders performs precoding using a precoding matrix satisfying P in P in H =I (P in denotes the most internal precoding matrix, H denotes an operator of the Hermitian matrix, and I denotes a unit matrix), wherein the precoding matrix includes the most internal precoding matrix and an external precoding matrix, and the most internal precoding matrix is selected from an internal codeword codebook including codewords satisfying c in n (c in n ) H =I (c in n denotes a codeword written by an index n) and the external precoding matrix is selected from an external codeword codebook including codewords satisfying min n , m ⁢  V t - c i ⁢ ⁢ n n × c out m  (V t denotes an eigen vector of a channel or a covariance matrix at t and c out m denotes a codeword written by an index m).