Method for physical control format indicator channel mapping

Abstract

A method of mapping symbols of a physical control format indicator channel (PCFICH) is described. A start position of a resource element to map the symbols for the PCFICH is determined by flooring a value, obtained by multiplying the number of resource blocks by a variable proportional to a symbol index for the PCFICH and then dividing the multiplied result by 2, wherein the resource blocks are transmitted in downlink. The symbols are mapped in the start position. Therefore, a problem of wasting resource elements or not being able to implement mapping can be solved by applying a simple mapping rule while mapping symbols of the PCFICH.

What is claimed is: 
     
       1. A base station in a wireless communication system, the base station comprising:
 means for mapping 16 physical control format indicator channel (PCFICH) symbols to four resource element groups (REGs) in a first orthogonal frequency division multiplexing (OFDM) symbol of a downlink subframe; and   means for transmitting the mapped 16 PCFICH symbols to a user equipment (UE),   wherein the four REGs comprises a first REG including first four resource elements (REs), a second REG including second four REs, a third REG including third four REs s and a fourth REG including fourth four REs,   wherein first REs from the first four REs, the second four REs, the third four REs and the fourth four REs have positions given by:   K 0 ,   K 0 +└N RB   DL /2┘*N SC   RB /2,   K 0 +└2N RB   DL /2┘*N SC   RB /2, and   K 0 +└3N RB   DL /2┘*N SC   RB /2, respectively,   wherein K 0  is determined as (N SC   RB /2)*(N ID   cell  mod 2 N RB   DL ),   wherein N RB   DL  indicates a number of resource blocks (RBs) transmitted in a downlink,   wherein N SC   RB  indicates a number of REs per a RB in the frequency domain, and   wherein N ID   cell  is a physical layer cell identifier.   
     
     
       2. The base station of  claim 1 , wherein the N SC   RB  is 12. 
     
     
       3. The base station of  claim 1 , further comprising:
 means for transmitting reference signals to the UE,   wherein each of the first REG, the second REG, the third REG and the four REG has 6 contiguous REs in the first OFDM symbol of the downlink subframe, and 2 of the 6 contiguous REs are used for the reference signals.   
     
     
       4. The base station of  claim 1 , wherein the 16 PCFICH symbols notify the UE of whether 1, 2 or 3 OFDM symbols in the downlink subframe are used for transmitting a control channel. 
     
     
       5. A user equipment in a wireless communication system, the user equipment comprising:
 means for receiving 16 physical control format indicator channel (PCFICH) symbols via a first orthogonal frequency division multiplexing (OFDM) symbol of a downlink subframe from a base station, wherein the 16 PCFICH symbols are mapped to four resource element groups (REGs), wherein the four REGs comprises a first REG including first four resource elements (REs), a second REG including second four REs, a third REG including third four REs and a fourth REG including fourth four REs,   wherein first REs from the first four REs, the second four REs, the third four REs and the fourth four REs have positions given by:   K 0 ,   K 0 +└N RB   DL /2┘*N SC   RB /2,   K 0 +└2N RB   DL /2┘*N SC   RB /2, and   K 0 +└3N RB   DL /2┘*N SC   RB /2, respectively,   wherein K 0  is determined as (N SC   RB /2)*(N ID   cell  mod 2 N RB   DL ),   wherein N RB   DL  indicates a number of resource blocks (RBs) transmitted in a downlink,   wherein N SC   RB  indicates a number of REs per a RB in the frequency domain, and   wherein N ID   cell  is a physical layer cell identifier.   
     
     
       6. The user equipment of  claim 5 , wherein the N SC   RB  is 12. 
     
     
       7. The user equipment of  claim 5 , further comprising:
 means for receiving reference signals from the base station,   wherein each of the first REG, the second REG, the third REG and the four REG has 6 contiguous REs in the first OFDM symbol of the downlink subframe, and 2 of the 6 contiguous REs are used for the reference signals.   
     
     
       8. The user equipment of  claim 5 , further comprising:
 means for acquiring information about a number of OFDM symbols used for a control channel based on the received 16 PCFICH symbols.   
     
     
       9. A method of mapping a physical control format indicator channel (PCFICH) transmitted to a user equipment (UE), the method comprising:
 mapping the PCFICH to four resource element regions in a first orthogonal frequency division multiplexing (OFDM) symbol in a downlink subframe,   wherein each of the four resource element regions includes four adjacent resource elements which are not used for transmitting a reference signal,   wherein indexes of starting resource elements corresponding to the four resource element regions are given by:   K 0 ,   K 0 +└N RB   DL /2┘*N SC   RB /2,   K 0 +└2N RB   DL /2┘*N SC   RB /2, and   K 0 +└3N RB   DL /2┘*N SC   RB /2, respectively,   wherein the additions are modulo N RB   DL N SC   RB ,   wherein K 0  is determined as (N SC   RB /2)*(N ID   cell  mod 2N RB   DL ),   wherein N RB   DL  indicates a number of resource blocks (RBs) transmitted in a downlink,   wherein N SC   RB  is 12, and   wherein N ID   cell  is a physical layer cell identifier.   
     
     
       10. The method of claim 9, wherein each of the four resource element regions corresponds to each of four resource element groups including 6 contiguous resource elements, and the 6 contiguous resource elements include 2 resource elements used for the reference signal. 
     
     
       11. The method of claim 9, wherein, when a starting resource element of K 0  collides with a resource element used for transmitting the reference signal, K 0  is determined as (N SC   RB /2)*(N ID   cell  mod 2N RB   DL )+1. 
     
     
       12. The method of claim 9, wherein the PCFICH notifies the UE of a number of symbols in the downlink used for transmitting a control channel. 
     
     
       13. A method of receiving a physical control format indicator channel (PCFICH) by a user equipment (UE), the method comprising:
 receiving the PCFICH in a first orthogonal frequency division multiplexing (OFDM) symbol in a downlink subframe,   wherein the PCFICH is mapped to four resource element regions in the first OFDM symbol of the downlink subframe,   wherein each of the four resource element regions includes four adjacent resource elements which are not used for transmitting a reference signal,   wherein indexes of starting resource elements corresponding to the four resource element regions are given by:   K 0 ,   K 0 +└N RB   DL /2┘*N SC   RB /2,   K 0 +└2N RB   DL /2┘*N SC   RB /2, and   K 0 +└3N RB   DL /2┘*N SC   RB /2, respectively,   wherein the additions are modulo N RB   DL N SC   RB ,   wherein K 0  is determined as (N SC   RB /2)*(N ID   cell  mod 2N RB   DL ),   wherein N RB   DL  indicates a number of resource blocks (RBs) transmitted in a downlink,   wherein N SC   RB  indicates a number of resource elements (REs) per RB in a frequency domain, and   wherein N ID   cell  is a physical layer cell identifier.   
     
     
       14. The method of claim 13, wherein each of the four resource element regions corresponds to each of four resource element groups including 6 contiguous resource elements, and the 6 contiguous resource elements include 2 resource elements used for the reference signal. 
     
     
       15. The method of claim 13, wherein, when a starting resource element of K 0  collides with a resource element used for transmitting the reference signal, K 0  is determined as (N SC   RB /2)*(N ID   cell  mod 2N RB   DL )+1. 
     
     
       16. The method of claim 13, wherein the PCFICH notifies the UE of a number of symbols in the downlink used for transmitting a control channel.