Method for receiving control information in orthogonal frequency division multiplexing system of mobile communication system

Abstract

The present invention relates to receiving control information in an orthogonal frequency division multiplexing (OFDM) system of a mobile communication system. The present invention includes receiving information related to a number of OFDM symbols in a subframe for receiving first control information, receiving information related to a number of OFDM symbols in the subframe for receiving second control information, decoding the first control information according to the received information related to the number of OFDM symbols in the subframe for receiving the first control information, and decoding the second control information according to the received information related to the number of OFDM symbols in the subframe for receiving the second control information, wherein the number of OFDM symbols for receiving the first control information is less than or equal to the number of OFDM symbols for receiving the second control information.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is

In Equation (1), “m” represents the number of OFDM symbols through which the ACK/NAK channel is transmitted, “n” represents the number of OFDM symbols for control channel transmission, and “N” represents the maximum number of OFDM symbols for control channel transmission. Here, the ACK/NAK channel is allocated to first m OFDM symbols. Moreover, like the “N” value, a maximum number of OFDM symbols through which the ACK/NAK channel is transmitted (M) may be previously determined. Accordingly, the “m” value may be within a range from 0 to M. Preferably, the “M” value is less than or equal to the “N” value.

If the “n” value varies per subframe using the above-described method, and although the amount of time/frequency resources within the “n” number of OFDM symbols capable of being allocated to the ACK/NAK channel in one subframe also varies, the number of OFDM symbols for control channel transmission may be varied within a limited range per subframe while a structure of the ACK/NAK channel is semi-statically fixed in accordance with one embodiment of the present invention. Examples of the varying range of the “n” value according to the “M” value will be described with reference to FIG. 2.

FIG. 2(a) is a diagram illustrating an example that the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) is 1. In the example that m=1, the ACK/NAK channel is transmitted through predetermined resource elements within a first OFDM symbol of each subframe, and the “n” value may vary within a range from 1 to 3 per subframe.

FIG. 2(b) is a diagram illustrating an example that the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) is 2. In the example that m=2, the ACK/NAK channel is transmitted through predetermined resource elements within first and second OFDM symbols of each subframe, and the “n” value may vary within a range from 2 to 3 per subframe.

FIG. 2(c) is a diagram illustrating an example that the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) is 3. In the example that m=3, the ACK/NAK channel is transmitted through predetermined resource elements within first, second and third OFDM symbols of each subframe. In this particular case, the “n” value is fixed at 3.

Through the above described method, the number of OFDM symbols for control channel transmission may be varied within a limited range per subframe while a structure of the ACK/NAK channel is semi-statically fixed, wherein control signals are transmitted on the control channel. Also, if the ACK/NAK channel transmission is performed using the OFDM symbols for control channel transmission as above, downlink data transmitted through OFDM symbols other than the OFDM symbols for control channel transmission and ACK/NAK signals are multiplexed to be transmitted in each subframe. Accordingly, complication in setting data transmission power is prevented.

FIG. 3 is a flow chart illustrating one example of a method for transmitting information on the number of OFDM symbols for control channel transmission (n) and a control channel from a base station in accordance with one embodiment of the present invention.

Initially, a base station may determine the number of OFDM symbols for control channel transmission (n) within a range of minimizing the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) by considering the number of OFDM symbols through which a predetermined ACK/NAK channel is transmitted (S10). Here, the “n” value is preferably less than or equal to the maximum number of OFDM symbols for control channel transmission (N), as described above.

Thereafter, the base station may transmit, to at least one mobile terminal, information regarding the determined number of OFDM symbols for control channel transmission (n) (S11). Finally, the relevant control channel may be transmitted to the at least one mobile terminal (S12).

Particularly, when the ACK/NAK channel is allocated to be transmitted through the maximum number of OFDM symbols for control channel transmission (N) that can be used in transmitting scheduling signals (N=M and m=M), as explained with reference to FIG. 2(c), the “n” value cannot have a value other than n=N. Thus, the “n” value may not be broadcast through the CCFI per subframe. Accordingly, the time/frequency resources reserved for CCFI transmission may not be used for CCFI transmission, but may have other uses. Preferably, the time/frequency resources may be extensively used for control signal transmission including the scheduling signals or the ACK/NAK signals.

In the above descriptions, an “n” value and an “m” value do not always exist in a unit of 1 within n≦N and m≦N, respectively. Rather, the values may be selected from a specific natural number set existing within n≦N and m≦N. Herein, the specific natural number set may include 0.

FIG. 4 is a flow chart illustrating one example of a method for receiving information on the number of OFDM symbols for control channel transmission (n) and a control channel in a mobile terminal in accordance with one embodiment of the present invention.

In the present embodiment, the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) is a value that can be semi-statically varied as described above. Preferably, a mobile terminal previously acquires information regarding the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) through an upper layer RRC message or other broadcasting channel before receiving and decoding a corresponding subframe(s).

In accordance with the present invention, the mobile terminal receives CCFI, which is information regarding the number of OFDM symbols for control channel transmission (n), through PCFICH. Here, the number of OFDM symbols for control channel transmission (n) may be varied within a range of minimizing the number of OFDM symbols through which the ACK/NAK channel is transmitted (m) according to one embodiment of the present invention. Preferably, the mobile terminal decodes the received number of OFDM symbols for control channel transmission (n) by obtaining correlation values using expected “n” values that can be the number of OFDM symbols for control channel transmission, etc.

As stated above, the mobile terminal may assume the expected “n” values based on the “m” value previously informed to the mobile terminal according to the present embodiment. Thus, when decoding the “n” value, the mobile terminal may decode the CCFI assuming that the “n” value is within the range of m≦n≦N so that the CCFI decoding outputs the “n” value within the range (S20).

After obtaining the “n” value by the above procedure, a mobile terminal may decode the second control channels assuming the control channels are transmitted through “n” OFDM symbols (S30).

In another aspect of the invention, the mobile terminal may decode the CCFI to obtain the “n” value without considering the expected range of m≦n≦N. Therefore, the mobile terminal may obtain the “n” value which is out of the valid range of m≦n≦N. In this case, the mobile terminal may try to decode control channels for all possible “n” values, or for every possible “n” value within the range of m≦n≦N.

Otherwise, in another example, when the “n” value obtained deviates from the range m≦n≦N, then decoding CCFI is considered to have failed for the particular “n” value. If so, an operation corresponding thereto may be abandoned. For example, the mobile terminal may abandon receiving scheduling signals in the subframe if the “n” value does not satisfy m≦n≦N.

Particularly, as explained with reference to FIG. 2(c), when the already known “m” is equal to the maximum number of OFDM symbols for control channel transmission (N), such that m=N, then the base station does not transmit the CCFI, or the mobile terminal does not decode the CCFI even though the base station transmits the CCFI because the mobile terminal assumes that n=N. Therefore, the mobile terminal may operate assuming that the scheduling signals and other control signals are transmitted through the first N OFDM symbols.

Alternatively, if the already known “m” is equal to the maximum number of OFDM symbols for control channel transmission (N), such that m=N, and if the base station transmits the CCFI, the mobile terminal will decode the CCFI. However, the mobile terminal will assume that n=N regardless of the decoding results. Accordingly, the mobile terminal may also operate assuming that the scheduling signals and other control signals are transmitted through the first N OFDM symbols.

FIG. 5 illustrates a block diagram of a mobile station (MS) or UE 1 in accordance with the present invention. The UE 1 includes a processor (or digital signal processor) 210, RF module 235, power management module 205, antenna 240, battery 255, display 215, keypad 220, memory 230, speaker 245 and microphone 250.

A user enters instructional information, such as a telephone number, for example, by pushing the buttons of a keypad 220 or by voice activation using the microphone 250. The microprocessor 210 receives and processes the instructional information to perform the appropriate function, such as to dial the telephone number. Operational data may be retrieved from the memory module 230 to perform the function. Furthermore, the processor 210 may display the instructional and operational information on the display 215 for the user's reference and convenience.

The processor 210 issues instructional information to the RF module 235, to initiate communication, for example, transmits radio signals comprising voice communication data. The RF module 235 comprises a receiver and a transmitter to receive and transmit radio signals. An antenna 240 facilitates the transmission and reception of radio signals. Upon receiving radio signals, the RF module 235 may forward and convert the signals to baseband frequency for processing by the processor 210. The processed signals would be transformed into audible or readable information outputted via the speaker 245, for example. The processor 210 also includes the protocols and functions necessary to perform the various processes described herein.

FIG. 6 is a diagram explaining an example of a method for receiving information of orthogonal frequency division multiplexing (OFDM) symbols of a downlink control channel in an OFDM system in accordance with one embodiment of the present invention. Referring to FIG. 6, a mobile terminal receives information about number m of first OFDM symbols which is used for transmission of a channel, wherein the channel carries a hybrid automatic repeat request (HARQ) ACK/NACK (S61). The mobile terminal receives information about number n of second OFDM symbols which is used for transmission of the downlink control channel (S62). In this example, the number n is equal to or greater than the number m (n≧m) and a transmission interval of the information about the number m is greater than a transmission interval of the information about the number n.

It is obvious that embodiments can be configured by combining the claims not having clear citation relations in the claims or new claims may be included in the claims by means of amendments after filing an application.

The embodiments according to the present invention can be implemented by various means, for example, hardware, firmware, software, or a combination thereof, etc. When implemented by the hardware, a method for receiving a control channel according to one embodiment of the present invention can be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro controllers, micro processors, etc.

When implemented by the firmware or the software, a method for receiving a control channel according to one embodiment of the present invention can be implemented in the shapes of modules, processes, and functions, etc. performing the functions or the operations explained as above. Software codes are stored in a memory unit, making it possible to be driven by a processor. The memory unit is positioned inside or outside the processor, making it possible to exchange data with the processor by means of various means already publicly known.

Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes might be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structure described herein as performing the recited function and not only structural equivalents but also equivalent structures.

Claims

1. A method of transmitting downlink control channels at a base station of an orthogonal frequency division multiplexing (OFDM) system, the method comprising:

transmitting first information indicating related to a size m of a first region through a broadcast channel, wherein the first region is defined by m OFDM symbol(s) starting from a beginning of a subframe and the first region is used for first control channels that carry hybrid automatic repeat request (HARQ) ACK/NACKs;

transmitting second information indicating related to a size n of a second region through a physical control format indicator channel (PCFICH), wherein the second region is defined by n OFDM symbol(s) starting from the beginning of the subframe and the second region is used for second control channels that carry downlink control information; and

transmitting the HARQ ACK/NACKs and the downlink control information through the first control channels and second control channels, respectively,

wherein first resources for the first control channels are identified from the first information, and second resources for the second control channels are identified from remaining resources excluding other than the first resources within the second region, and

wherein the second control channels are physical downlink control channels (PDCCHs).

2. The method of claim 1, wherein the size n is configured to be equal to or greater than the size m such that n≧m.

3. A method of receiving downlink control channels at a mobile terminal of an orthogonal frequency division multiplexing (OFDM) system, the method comprising:

receiving first information indicating related to a size m of a first region through a broadcast channel, wherein the first region is defined by m OFDM symbol(s) starting from a beginning of a subframe and the first region is used for first control channels that carry hybrid automatic repeat request (HARQ) ACK/NACKs;

receiving second information indicating related to a size n of a second region through a physical control format indicator channel (PCFICH), wherein the second region is defined by n OFDM symbol(s) starting from the beginning of the subframe and the second region is used for second control channels that carry downlink control information; and

receiving the HARQ ACK/NACKs and the downlink control information through the first control channels and second control channels, respectively,

wherein first resources for the first control channels are identified from the first information, and second resources for the second control channels are identified from remaining resources excluding other than the first resources within the second region, and

wherein the second control channels are physical downlink control channels (PDCCHs).

4. The method of claim 3, wherein the size n is configured to be equal to or greater than the size m such that n≧m.

5. The method of claim 3, further comprising:

performing operations in accordance with one of the second control channels received through the second region that is designated to the mobile terminal.

6. A base station used in an orthogonal frequency division multiplexing (OFDM) system, the base station comprising:

a radio frequency unit; and

a processor,

wherein the processor is configured to:

transmit first information indicating related to a size m of a first region through a broadcast channel, wherein the first region is defined by m OFDM symbol(s) starting from beginning of a subframe and the first region is used for first control channels that carry hybrid automatic repeat request (HARQ) ACK/NACKs;

transmit second information indicating related to a size n of a second region through a physical control format indicator channel (PCFICH), wherein the second region is defined by n OFDM symbol(s) starting from the beginning of the subframe and the second region is used for second control channels that carry downlink control information; and

transmit the HARQ ACK/NACKs and the downlink control information through the first control channels and second control channels, respectively,

wherein first resources for the first control channels are identified from the first information, and second resources for the second control channels are identified from remaining resources excluding other than the first resources within the second region, and

wherein the second control channels are physical downlink control channels (PDCCHs).

7. The base station of claim 6, wherein the size n is configured to be equal to or greater than the size m such that n≧m.

8. A mobile terminal used in an orthogonal frequency division multiplexing (OFDM) system, the mobile terminal comprising:

a radio frequency unit; and

a processor,

wherein the processor is configured to: receive first information indicating related to a size m of a first region through a broadcast channel, wherein the first region is defined by m OFDM symbol(s) starting from a beginning of a subframe and the first region is used for first control channels that carry hybrid automatic repeat request (HARQ) ACK/NACKs;

receive second information indicating related to a size n of a second region through a physical control format indicator channel (PCFICH), wherein the second region is defined by n OFDM symbol(s) starting from the beginning of the subframe and the second region is used for second control channels that carry downlink control information; and

receive the HARQ ACK/NACKs and the downlink control information through the first control channels and second control channels, respectively,

wherein first resources for the first control channels are identified from the first information, and second resources for the second control channels are identified from remaining resources excluding other than the first resources within the second region, and

wherein the second control channels are physical downlink control channels (PDCCHs).

9. The mobile terminal of claim 8, wherein the size n is configured to be equal to or greater than the size m such as that n≧m.

10. The mobile terminal of claim 8, wherein the processor is further configured to:

perform operations in accordance with one of the second control channels received through the second region that is designated to the mobile terminal.