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.

Claims

.[.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.sub.0, K.sub.0+└N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, K.sub.0+└2N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, and K.sub.0+└3N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, respectively, wherein K.sub.0 is determined as (N.sub.SC.sup.RB/2)*(N.sub.ID.sup.cell mod 2 N.sub.RB.sup.DL), wherein N.sub.RB.sup.DL indicates a number of resource blocks (RBs) transmitted in a downlink, wherein N.sub.SC.sup.RB indicates a number of REs per a RB in the frequency domain, and wherein N.sub.ID.sup.cell is a physical layer cell identifier..].

.[.2. The base station of claim 1, wherein the N.sub.SC.sup.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.sub.0, K.sub.0+└N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, K.sub.0+└2N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, and K.sub.0+└3N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, respectively, wherein K.sub.0 is determined as (N.sub.SC.sup.RB/2)*(N.sub.ID.sup.cell mod 2 N.sub.RB.sup.DL), wherein N.sub.RB.sup.DL indicates a number of resource blocks (RBs) transmitted in a downlink, wherein N.sub.SC.sup.RB indicates a number of REs per a RB in the frequency domain, and wherein N.sub.ID.sup.cell is a physical layer cell identifier..].

.[.6. The user equipment of claim 5, wherein the N.sub.SC.sup.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..].

.Iadd.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.sub.0, K.sub.0+└N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, K.sub.0+└2N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, and K.sub.0+└3N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, respectively, wherein the additions are modulo N.sub.RB.sup.DLN.sub.SC.sup.RB, wherein K.sub.0 is determined as (N.sub.SC.sup.RB/2)*(N.sub.ID.sup.cell mod 2N.sub.RB.sup.DL), wherein N.sub.RB.sup.DL indicates a number of resource blocks (RBs) transmitted in a downlink, wherein N.sub.SC.sup.RB is 12, and wherein N.sub.ID.sup.cell is a physical layer cell identifier..Iaddend.

.Iadd.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..Iaddend.

.Iadd.11. The method of claim 9, wherein, when a starting resource element of K.sub.0 collides with a resource element used for transmitting the reference signal, K.sub.0 is determined as (N.sub.SC.sup.RB/2)*(N.sub.ID.sup.cell mod 2N.sub.RB.sup.DL)+1..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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.sub.0, K.sub.0+└N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, K.sub.0+└2N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, and K.sub.0+└3N.sub.RB.sup.DL/2┘*N.sub.SC.sup.RB/2, respectively, wherein the additions are modulo N.sub.RB.sup.DLN.sub.SC.sup.RB, wherein K.sub.0 is determined as (N.sub.SC.sup.RB/2)*(N.sub.ID.sup.cell mod 2N.sub.RB.sup.DL), wherein N.sub.RB.sup.DL indicates a number of resource blocks (RBs) transmitted in a downlink, wherein N.sub.SC.sup.RB indicates a number of resource elements (REs) per RB in a frequency domain, and wherein N.sub.ID.sup.cell is a physical layer cell identifier..Iaddend.

.Iadd.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..Iaddend.

.Iadd.15. The method of claim 13, wherein, when a starting resource element of K.sub.0 collides with a resource element used for transmitting the reference signal, K.sub.0 is determined as (N.sub.SC.sup.RB/2)*(N.sub.ID.sup.cell mod 2N.sub.RB.sup.DL)+1..Iaddend.

.Iadd.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..Iaddend.

Description

DESCRIPTION OF DRAWINGS

(1) The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

(2) In the drawings

(3) FIG. 1 illustrates a conventional mapping method in which 4 symbols are mapped to 2 REGs;

(4) FIG. 2 illustrates the case where mapping can not be implemented in a conventional mapping method;

(5) FIG. 3 is a flow chart illustrating a PCFICH mapping method according to an exemplary embodiment of the present invention; mapping method;

(6) FIG. 4 is a flow chart illustrating a PCFICH mapping method according to another exemplary embodiment of the present invention; mapping method;

(7) FIG. 5 illustrates an example of REGs when 2 or less transmit antennas are used; mapping method;

(8) FIG. 6 illustrates an example of REGs when 4 transmit antennas are used; and mapping method;

(9) FIG. 7 illustrates an example of PCFICH mapping according to a cell ID.

BEST MODE

(10) Reference will now be made in detail to the exemplary embodiments of the present invention with reference to the accompanying drawings. The detailed description is intended to explain exemplary embodiments of the present invention, rather than to show the only embodiments that can be implemented according to the invention.

(11) In an exemplary embodiment of the present invention, a method applying different mapping rules according to N.sub.RB.sup.DL is proposed.

(12) In a conventional mapping method, the above-described problems do not occur for N.sub.RB.sup.DL of an even number, so the conventional mapping method is used for N.sub.RB.sup.DL of an even number and the following mapping method is used for N.sub.RB.sup.DL of an odd number.

(13) Hereinbelow, y(0), . . . , y(15) denotes 16 QPSK symbols, N.sub.RB.sup.DL denotes the number of resource blocks transmitted in downlink, and N.sub.sc.sup.RB denotes the number of resource elements per resource block.

(14) According to an exemplary embodiment of the present invention, if N.sub.RB.sup.DL is an odd number, y(0), . . . , y(3) are mapped to resource elements starting with a position of k=k.sub.0, y(4), . . . , y(7) are mapped to resource elements starting with a position of k=k.sub.0+.left brkt-bot.(N.sub.RB.sup.DL-1)N.sub.sc.sup.RB/4.right brkt-bot., y(8), . . . , y(11) are mapped to resource elements starting with a position of k=k.sub.0+.left brkt-bot.2N.sub.RB.sup.DLN.sub.sc.sup.RB/4.right brkt-bot. or k=k.sub.0+.left brkt-bot.2(N.sub.RB.sup.DL-1)N.sub.sc.sup.RB/4.right brkt-bot., and y(12), . . . , y(15) are mapped to resource elements starting with a position of k=k.sub.0+.left brkt-bot.3(N.sub.RB.sup.DL-1)N.sub.sc.sup.RB/4.right brkt-bot.

(15) FIG. 3 is a flow chart illustrating a PCFICH mapping method according to an exemplary embodiment of the present invention.

(16) A symbol index i for PCFICH mapping is initialized to 0 (step S310).

(17) Next, a determination is made as to whether N.sub.RB.sup.DL is an odd number (step S320). If N.sub.RB.sup.DL is an odd number, positions of resource elements to map 4 symbols of a PCFICH are determined using N.sub.RB.sup.DL-1 and the 4 symbols are mapped to corresponding positions (step S330).

(18) If N.sub.RB.sup.DL is an even number, positions of resource elements to map 4 symbols of a PCFICH are determined using N.sub.RB.sup.DL and the 4 symbols are mapped to corresponding positions (step S340).

(19) If mapping is completed, the symbol index i is increased by 4 (step S350).

(20) If the symbol index i is less than 16 (step S360), the above operations (steps S320 to S350) are repeated since symbols to be mapped remain.

(21) Finally, if the symbol index i is equal to or greater than 16 (S360), a procedure is ended.

(22) Meanwhile, another exemplary embodiment of the present invention proposes a single mapping method irrespective of whether N.sub.RB.sup.DL is an odd number or an even number.

(23) That is, the following mapping rule using a single expression regardless of N.sub.RB.sup.DL can solve the conventional problems in mapping symbols for a PCFICH.

(24) According to another exemplary embodiment of the present invention, y(0), . . . , y(3) are mapped to resource elements starting with a position of k=k.sub.0, y(4), . . . , y(7) are mapped to resource elements starting with a position of k=k.sub.0+.left brkt-bot.N.sub.RB.sup.DL/2.right brkt-bot.N.sub.sc.sup.RB/2, y(8), . . . , y(11) are mapped to resource elements starting with a position of k=k.sub.0+.left brkt-bot.2N.sub.RB.sup.DL/2.right brkt-bot.N.sub.sc.sup.RB/2, and y(12), . . . , y(15) are mapped to resource elements starting with a position of k=k.sub.0+3N.sub.RB.sup.DL/2.right brkt-bot.N.sub.sc.sup.RB/2.

(25) In the above method, k.sub.0 is determined according to N.sub.ID.sup.cell. If an index indicated by k.sub.0 collides with an index of a resource element using a reference signal, k.sub.0 may use an index increased by ‘1’.

(26) FIG. 4 is a flow chart illustrating a PCFICH mapping method according to another exemplary embodiment of the present invention.

(27) First, a symbol index i for PCFICH mapping is initialized to 0 (step S410).

(28) A start position of a resource element for PCFICH mapping is determined by flooring a value obtained by multiplying a variable I.sub.i proportional to the symbol index by N.sub.RB.sup.DL and then dividing the multiplied result by 2 (step S420). The variable may be, for example, I.sub.0=0, I.sub.4=1, I.sub.8=2, and I.sub.12=3.

(29) If mapping is completed, the symbol index i is increased by 4 (step S450).

(30) If the symbol index i is less than 16 (step S460), the above operations (steps S420 to 5450) are repeated since symbols to be mapped remain.

(31) Finally, if the symbol index i is equal to or greater than 16 (S460), a procedure is ended.

(32) The above mapping rule according to another exemplary embodiment of the present invention may be modified as follows.

(33) Namely, y(0), . . . , y(3) are mapped to resource elements starting with a position of k=k.sub.0, y(4), . . . , y(7) are mapped to resource elements starting with a position of k=k.sub.0+3.left brkt-bot.N.sub.RB.sup.DL/2.right brkt-bot.N.sub.sc.sup.RB/2, y(8), . . . , y(11) are mapped to resource elements starting with a position of k=k.sub.0+2.left brkt-bot.N.sub.RB.sup.DL/2.right brkt-bot.N.sub.sc.sup.RB/2, and (12), . . . , y(15) are mapped to resource elements starting with a position of k=k.sub.0+3.left brkt-bot.N.sub.RB.sup.DL/2.right brkt-bot.N.sub.sc.sup.RB/2.

(34) FIG. 5 illustrates an example of REGs when two or less transmit antennas are used.

(35) In the first OFDM symbol (first line) through which a PCFICH is transmitted, since reference signals of respective antennas are transmitted, one REG is comprised of 6 resource elements. Since no reference signal exists in the second OFDM symbol (second line) when using 2 or less transmit antennas, one REG is comprised of 4 resource elements.

(36) FIG. 6 illustrates an example of REGs when 4 transmit antennas are used.

(37) In the first OFDM symbol (first line) through which a PCFICH is transmitted, since reference signals of antennas are transmitted, one REG is comprised of 6 resource elements. When using 4 transmit antennas, since reference signals exist even in the second OFDM symbol (second line), one REG is comprised of 6 resource elements.

(38) FIG. 7 illustrates an example of PCFICH mapping according to a cell ID.

(39) In FIG. 7, a system band corresponds to 20 resource blocks. Different start positions are set for 10 cell IDs. Positions denoted by “1” indicate positions of k.sub.0 in the above-described mapping method. Accordingly, interference between cell IDs is reduced.

(40) It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

(41) The present invention provides a mapping method for frequency and OFDM symbol regions of a signal transmitted in downlink in a cellular OFDM wireless packet communication system and is applicable to a base station, a user equipment, etc. in a 3GPP LTE system.