Method and user equipment for receiving downlink signals, and method and base station for transmitting downlink signals

A method of transmitting a downlink signal in a narrowband by a base station in a wireless communication system, the method comprising:

• transmitting a first cell identifier through a first carrier;
• transmitting carrier information for a second carrier;
• and
• transmitting downlink data on the second carrier based on the carrier information and a narrowband reference signal (NB-RS),
• wherein each of the first and second carriers operates in one resource block (RB),
• wherein the first carrier is a carrier on which a narrowband synchronization signal (nSS) and a narrowband physical broadcast channel (nPBCH) are present and the second carrier is a carrier on which the nSS and the nPBCH are not present,
• wherein the NB-RS are transmitted based on the first cell identifier, and
• wherein the carrier information includes cell identifier information indicating whether a second cell identifier used for a cell specific reference signal (CRS) on the second carrier is the same as the first cell identifier,
• wherein if the cell identifier information indicates that the second cell identifier used for the CRS is the same as the first cell identifier, the number of antenna ports for the CRS is the same as the number of antenna ports for the NB-RS, and
• wherein if the cell identifier information indicates that the second cell identifier used for the CRS is different from the first cell identifier, the carrier information further includes number-of-antenna ports information and the number of antenna ports for the CRS is the same as the number of antenna ports corresponding to the number-of-antenna ports information.

A user equipment for receiving a downlink signal in a narrowband in a wireless communication system, the user equipment comprising,

• a radio frequency (RF) unit, and
• a processor configured to control the RF unit, the processor configured to:
• acquire a first cell identifier from a first carrier;
• control the RF unit to receive carrier information for a second carrier;
• and
• control the RF unit to receive downlink data on the second carrier based on the carrier information and a narrowband reference signal (NB-RS), and
• wherein each of the first and second carriers operates in one resource block (RB),
• wherein the first carrier is a carrier on which a narrowband synchronization signal (nSS) and a narrowband physical broadcast channel (nPBCH) are present and the second carrier is a carrier on which the nSS and the nPBCH are not present,
• wherein the NB-RS are received based on the first cell identifier, and
• wherein the carrier information includes cell identifier information indicating whether a second cell identifier used for a cell specific reference signal (CRS) on the second carrier is the same as the first cell identifier,
• wherein if the cell identifier information indicates that the second cell identifier used for the CRS is the same as the first cell identifier, the number of antenna ports for the CRS is the same as the number of antenna ports for the NB-RS, and
• wherein if the cell identifier information indicates that the second cell identifier used for the CRS is different from the first cell identifier, the carrier information further includes number-of-antenna ports information and the number of antenna ports for the CRS is the same as the number of antenna ports corresponding to the number-of-antenna ports information.

A base station for transmitting a downlink signal in a narrowband in a wireless communication system, the base station comprising,

• a radio frequency (RF) unit, and
• a processor configured to control the RF unit, the processor configured to:
• control the RF unit to transmit a first cell identifier through a first carrier;
• control the RF unit to transmit carrier information for a second carrier;
• and
• control the RF unit to transmit downlink data on the second carrier based on the carrier information and a narrowband reference signal (NB-RS), and
• wherein each of the first and second carriers operates in one resource block (RB),
• wherein the first carrier is a carrier on which a narrowband synchronization signal (nSS) and a narrowband physical broadcast channel (nPBCH) are present and the second carrier is a carrier on which the nSS and the nPBCH are not present,
• wherein the NB-RS are received based on the first cell identifier, and
• wherein the carrier information includes cell identifier information indicating whether a second cell identifier used for a cell specific reference signal (CRS) on the second carrier is the same as the first cell identifier,
• wherein if the cell identifier information indicates that the second cell identifier used for the CRS is the same as the first cell identifier, the number of antenna ports for the CRS is the same as the number of antenna ports for the NB-RS, and
• wherein if the cell identifier information indicates that the second cell identifier used for the CRS is different from the first cell identifier, the carrier information further includes number-of-antenna ports information and the number of antenna ports for the CRS is the same as the number of antenna ports corresponding to the number-of-antenna ports information.