Method and apparatus for performing synchronization in wireless communication system

1. A method for performing a synchronization in a wireless communication system, performed by a wireless device, the method comprising:

receiving a configuration including a resource relationship about reference signals (RSs) between a first cell and a second cell;

receiving a first reference signal (RS) from the first cell;

determining a timing reference to receive a second RS based on the resource relationship;

receiving the second RS from the second cell based on the determined timing reference;

receiving an indicator to indicate whether or not the second RS is applied for frequency tracking of data signals;

if the indicator indicates that the second RS is applied for the frequency tracking of data signals, performing the frequency tracking by using the second RS received from the second cell, and decoding data signals from the second cell; and

if the indicator indicates that the second RS is not applied for the frequency tracking of data signals, performing the frequency tracking by using the first RS received from the first cell, and decoding data signals from the first cell.

2. The method of claim 1 , wherein the resource relationship includes a first RS configuration and a second RS configuration for resource mapping,

the first RS includes at least one of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), a cell-common reference signal (CRS), or a channel information reference signal (CSI-RS) to be transmitted on the first cell,

the second RS signal includes a discovery signal to be transmitted on the second cell.

3. The method of claim 2 , wherein the resource relationship includes:

subframe information indicating a subframe gap between a subframe at which the first RS is received and a subframe at which the second RS is received, and

resource information indicating offset between resource blocks at which the first RS is received and resource blocks at which the second RS is received.

4. The method of claim 1 , wherein receiving the second RS from the second cell including:

receiving a second configuration including a resource relationship about RSs between second cells; and

receiving a plurality of second RSs from a plurality of second cells based on the resource relationship.

5. The method of claim 4 , wherein the resource relationship includes:

a first resource relationship including subframe information indicating a subframe gap between a subframe at which the first RS is received and subframes each at which the second RSs each is received, a second resource relationship including resource information indicating offset between resource blocks each at which the second RSs each is received,

wherein the second RS signals are transmitted from different transmitting points.

6. The method of claim 1 , wherein the indicator is determined by a mobility of the wireless device.

7. The method of claim 1 , wherein receiving the second RS from the second cell including:

determining a value of timing advance (TA) of the first cell and a predetermined offset of the second cell; and

receiving the second RS at subframes determined by the value of TA and the offset.

8. A wireless device for performing an initial access procedure in a wireless communication system, the wireless device comprises:

a radio frequency (RF) unit for transmitting and receiving a radio signal; and

a processor, operatively coupled to the RF unit, that:

controls the RF unit to receive a configuration including a resource relationship about reference signals (RSs) between a first cell and a second cell;

controls the RF unit to receive a first reference signal (RS) from the first cell;

determines a timing reference to receive a second RS based on the resource relationship;

controls the RF unit to receive the second RS from the second cell based on the determined timing reference;

controls the RF unit to receive an indicator to indicate whether or not the second RS is applied for frequency tracking of data signals;

if the indicator indicates that the second RS is applied for the frequency tracking of data signals, performs the frequency tracking by using the second RS received from the second cell, and decodes data signals from the second cell; and

if the indicator indicates that the second RS is not applied for the frequency tracking of data signals, performs the frequency tracking by using the first RS received from the first cell, and decodes data signals from the first cell.

9. The wireless device of claim 8 , wherein the resource relationship includes subframe information indicating a subframe gap between a subframe at which the first RS is received and a subframe at which the second RS is received, and

resource information indicating offset between resource blocks at which the first RS is received and resource blocks at which the second RS is received.

10. The wireless device of claim 8 , wherein the processor:

controls the RF unit to receive a second configuration including a resource relationship about RSs between second cells; and

controls the RF unit to receive a plurality of second RSs from a plurality of second cells.

11. The wireless device of claim 9 , wherein the resource relationship includes:

a first resource relationship including subframe information indicating a subframe gap between a subframe at which the first RS is received and subframes each at which the second RSs each is received, a second resource relationship including resource information indicating offset between resource blocks each at which the second RSs each is received,

wherein the second RS signals are transmitted from different transmitting points.

12. The wireless device of claim 8 , wherein the processor:

determines a value of timing advance (TA) of the first cell and a predetermined offset of the second cell; and

controls the RF unit to receive the second RS at subframes determined by the value of TA and the offset.