Method and device for precoding in wireless communication system

A method of precoding in a wireless communication system, the method comprising:

• (a) generating a first precoding matrix, W1, for deciding transmit power of one antenna group among a plurality of antenna groups as maximum power per antenna group;
• (b) generating a zero forcing (ZF) precoding matrix, Ti, which does not affect the antenna group whose transmit power is decided as the maximum power per antenna group, based on (i−1)th precoding matrix Wi−1 (i=2, 3, . . . );
• (c) determining a constant αi which decides transmit power of one antenna group from the remaining antenna groups whose transmit power are not determined as the maximum power per antenna group, based on the Ti;
• and
• (d) generating ith precoding matrix Wi based on the Ti and the αi,
• wherein the steps from (b) to (d) are repeated by incrementing i by one until the condition i≦NG, NtNG−K−(i−1)Nt≧Nt is satisfied,
• where NG is the number of the plurality of antenna groups, Nt is a number of transmission antennas included in each antenna group, and K is a number of total users using a single reception antenna.

An apparatus in a wireless communication system, the apparatus comprising:

• a radio frequency (RF) unit configured to transmit or receive a wireless signal;
• and
• a processor connected to the RF unit,
• wherein the processor is configured to:
• (a) generate a first precoding matrix, W1, for deciding transmit power of one transmission antenna among a plurality of transmission antennas as maximum power per antenna;
• (b) generate a zero forcing (ZF) precoding matrix, Ti, which does not affect the transmission antenna whose transmit power is decided as the maximum power per antenna, based on (i−1)th precoding matrix Wi−1 (i=2, 3, . . . );
• (c) determine a constant αi which decides transmit power of one transmission antenna from the remaining transmission antennas whose transmit power are not determined as the maximum power per antenna, based on the Ti;
• and
• (d) generate ith precoding matrix Wi based on the Ti and the αi,
• wherein (b), (c) and (d) are repeated by incrementing i by one until a condition i=Nt−K+1 is satisfied, and
• where Nt is a number of the plurality of transmission antennas, and K is a number of total users using a single reception antenna.