Method and apparatus for transmitting ACK/NACK signals

A method for processing, at a user equipment, a Physical Hybrid Automatic Repeat reQuest (HARQ) Indicator Channel (PHICH) in a wireless communication system, the method comprising:

• receiving spread sequences corresponding to HARQ indicator (HI) codeword (b0, b1, b2) through Resource Element Groups (REGs), wherein each spread sequence corresponds to a respective bit of the HI codeword (b0, b1, b2) and is mapped on a respective Resource Element Group (REG) of the PHICH, and each REG includes 4 neighboring subcarriers in an Orthogonal Frequency Division Modulation (OFDM) symbol;
• de-spreading the spread sequences to provide the HI codeword (b0, b1, b2);
• and
• channel-decoding the HI codeword (b0, b1, b2) to provide HARQ indicators (HI0 and HI1) in accordance with table 1,
• wherein the first bit (b0) and the second bit (b1) of the HI codeword correspond to the HI0 and HI1, respectively;
• and the third bit (b2) of the HI codeword is a result of an exclusive OR (XOR) of the first bit (b0) of the HI codeword and the second bit (b1) of the HI codeword,
• TABLE 1
• HI codeword
• HI0
• HI1
• <b0,b1,b2>
• 0
• 0
• <1,1,0>
• 0
• 1
• <1,0,1>
• 1
• 0
• <0,1,1>
• 1
• 1
• <0,0,0>.

A base station configured to transmit a Physical Hybrid Automatic Repeat reQuest (HARQ) Indicator Channel (PHICH) in a wireless communication system, the base station comprising:

• a Radio Frequency (RF) unit;
• and
• a processor,
• wherein the processor is configured to
• channel-code HARQ indicators (HI0 and HI1) to provide HI codeword (b0, b1, b2) in accordance with table 1,
• spread the HI codeword (b0, b1, b2) to provide spread sequences, each spread sequence corresponding to a respective bit of the HI codeword (b0, b1, b2), and
• transmit each spread sequence through a respective Resource Element Group (REG) of the PHICH, each REG including 4 neighboring subcarriers in an Orthogonal Frequency Division Modulation (OFDM) symbol,
• wherein the first bit (b0) and the second bit (b1) of the HI codeword are generated by the HI0 and HI1, respectively;
• and the third bit (b2) of the HI codeword is a result of an exclusive OR (XOR) of the first bit (b0) of the HI codeword and the second bit (b1) of the HI codeword,
• TABLE 1
• HI codeword
• HI0
• HI1
• <b0,b1,b2>
• 0
• 0
• <1,1,0>
• 0
• 1
• <1,0,1>
• 1
• 0
• <0,1,1>
• 1
• 1
• <0,0,0>.

A user equipment configured to process a Physical Hybrid Automatic Repeat reQuest (HARQ) Indicator Channel (PHICH) in a wireless communication system, the user equipment comprising:

• a Radio Frequency (RF) unit;
• and
• a processor,
• wherein the processor is configured to
• receive spread sequences corresponding to HARQ indicator (HI) codeword (b0, b1, b2) through Resource Element Groups (REGs), wherein each spread sequence corresponds to a respective bit of the HI codeword (b0, b1, b2) and is mapped on a respective Resource Element Group (REG) of the PHICH, and each REG includes 4 neighboring subcarriers in an Orthogonal Frequency Division Modulation (OFDM) symbol;
• de-spread the spread sequences to provide the HI codeword (b0, b1, b2), and channel-decode the HI codeword (b0, b1, b2) to provide HARQ indicators (HI0 and HI1) in accordance with table 1,
• wherein the first bit (b0) and the second bit (b1) of the HI codeword correspond to the HI0 and HI1, respectively;
• and the third bit (b2) of the HI codeword is a result of an exclusive OR (XOR) of the first bit (b0) of the HI codeword and the second bit (b1) of the HI codeword,
• TABLE 1
• HI codeword
• HI0
• HI1
• <b0,b1,b2>
• 0
• 0
• <1,1,0>
• 0
• 1
• <1,0,1>
• 1
• 0
• <0,1,1>
• 1
• 1
• <0,0,0>.