WO2010077042A2

WO2010077042A2 - A method and apparatus for transmitting and receiving control channels in a wireless communication system

Info

Publication number: WO2010077042A2
Application number: PCT/KR2009/007839
Authority: WO
Inventors: Hyoung Ju Ji; Joon Young Cho; Ju Ho Lee; Jin Kyu Han
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2008-12-30
Filing date: 2009-12-28
Publication date: 2010-07-08
Also published as: KR101494643B1; KR20100078232A; WO2010077042A3

Abstract

A method and apparatus is disclosed that transmits and receives downlink physical control channels in a wireless communication system. The method for transmitting downlink physical control channels of a sub-frame using a multi-carrier includes generating a primary carrier and sub-carriers, and transmitting the sub-frame. The primary carrier of the sub-frame contains packet data control channel (PDCCH) of all carriers. The sub-carrier of the sub-frame contains physical control format indicator channel (PCFICH) having a channel allocation indicator (L) indicating that the downlink shared channel (PDCCH) is not transmitted.

Description

A METHOD AND APPARATUS FOR TRANSMITTING AND RECEIVING CONTROL CHANNELS IN A WIRELESS COMMUNICATION SYSTEM

The present invention relates to wireless communication systems, and more particularly, to a method and apparatus that can transmit and receive control channel in a wireless communication system to efficiently utilize wireless resources.

Orthogonal frequency division multiplexing (OFDM) transmission method transmits data using a multi-carrier. That is, OFDM transmission method refers to a type of multi carrier modulation where input symbol streams are parallelized and modulated into a plurality of multi-carriers, mathematically orthogonal to each other, i.e., a plurality of sub-carrier channels, and the carries are transmitted.

The first systems using multi-carrier modulation (MCM) were military high frequency (HF) radio links in the late 1950’s. OFDM transmission method with densely spaced subcarriers with overlapping spectra of the modulating signal was initially developed in 1970’s. It was, however, so difficult to implement orthogonal modulation among multi-carriers. Therefore, MCM has limitations in applications to actual systems. Rapid progress in the development of OFDM technology has been made since Weinstein et al. published that the modulation/demodulation using OFDM can be efficiently processed using Discrete Fourier Transform (DFT). Also, since a method where guard intervals are used and Cyclic Prefix (CP) symbols are inserted into the guard intervals has been disclosed, the negative effects of multi-path propagation and delay spread on systems have been remarkably reduced.

Owing to these technical advances, the OFDM method is being widely applied to digital transmission technology, such as digital audio broadcasting (DAB), digital video broadcasting (DVB), wireless local area network (WLAN) communication, and wireless asynchronous transfer mode (WATM). That is, the OFDM method has not been widely used due to its hardware complexity, but has recently become practicable with the development of various digital signal processing techniques, such as Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT), etc.

Although the OFDM method is similar to a conventional frequency division multiplexing (FDM) method, it is characterized in that it can achieve optimal transmission efficiency at high-speed data transmission by transmitting data while maintaining the orthogonality among a plurality of tones. The OFDM method is also characterized in that, since it efficiently uses frequencies and is robust to multi-path fading, it can achieve optimal transmission efficiency during the high-speed data transmission.

The OFDM method has other advantages in that it is efficient in frequency use with overlapping frequency spectra, it is robust to frequency selective fading and multi-path fading, it can reduce the effect of inter-symbol interference (ISI) by employing guard intervals, it can allow an equalizer to be simply designed in hardware, and it is robust to impulsive noises. Therefore, the OFDM method is actively applied to communication system architectures.

In wireless communication, the communication speed and the quality of data communication services are affected by the changes in the channel environment. Channel environment in wireless communication frequently changes due to a variety of factors, such as additive white Gaussian noise (AWGN), a fading incurred change in the power of received signal, shadowing, Doppler effects caused by movement of a mobile station and frequent changes in its velocity, and interference caused by other users and multi-path signals. Therefore, in order to support a high communication speed and a high quality of data communication services in wireless communication, it is required to effectively process the factors deteriorates the channel environment.

In an OFDM method, a modulated signal is delivered in the two-dimensional resource composed of time and frequency. Resources on the time axis are distinguished by different OFDM symbols that are orthogonal to each other. Resources on the frequency axis are distinguished by different tones that are orthogonal to each other. A minimum resource unit can be defined with an OFDM symbol on the time axis and a tone on the frequency axis. This is called a ‘resource element (RE).’ Although different Res are processed via a frequency selective channel, they are orthogonal. Therefore, signals transmitted via different Res don not cause interference at the receiver.

Physical channels refer to physical layer channels that transmit symbols modulated with one or more encoded bit streams. In orthogonal frequency division multiple access (OFDMA), a plurality of physical channels are formed and then transmitted, according to the purposes of information streams or the types of receivers. The term ‘mapping’ refers to a protocol set between a transmitter and a receiver how to deploy one physical channel to an RE and transmit it.

Long term evolution advance (LTE) systems refer to systems where OFDM is adopted as the downlink. In recent years, long term evolution-advance (LTE-A) systems, evolved from LTE systems, have been researched and developed. An LTE-A system will be configured with a variety of scenarios. For example, an LTE-A system may use OFDM symbol structure improved so that it can be adapted to an indoor channel environment. An indoor environment is short in the channel delay because the cell size is small and is small in the effect of the multi-path. In that case, unlike the conventional LTE system structure, the LTE-A system can reduce the length of CP to increase the frequency efficiency in one symbol, so that it can use a symbol structure that differs from that of the conventional LTE system.

Since the LTE-A system has an architecture evolved from the LTE system, it can access the LTE system. All control channels used by the LTE system can be reused. At the initial stage where the LTE-A system starts to be introduced, since the ratio of LTE mobile stations to the LTE-A mobile stations is large, the LTE-A base station must be configured to sufficiently support the transmission and reception of the LTE mobile state. When an LTE-A mobile station is connected to an LTE-A base station installed doors, the LTE-A base station may form sub-frames dedicated to only an LTE-A mobile station in order to achieve higher frequency efficiency. In that case, the conventional LTE mobile station may receive LTE-A dedicated sub-frames but cannot recover data. Therefore, the conventional LTE mobile station cannot detect information regarding LTE-A dedicated sub-frames through a conventional LTE system control channel architecture, and also cannot distinguish among each of the sub-frames.

FIG. 1 is a view that describes structure of a conventional downlink frame.

Referring to FIG. 1, reference number 111 shows that control signals in all carriers are received via controls channels. If controls channels PCIFICH, PHICH, and PDCCH by sub-frames of each carrier are transmitted to a mobile station, the mobile station needs to demodulate a downlink physical control channel (DPCCH) of a corresponding carrier since all

carriers

101, 103, 105, 107, and 109 contain information regarding DPCCH. That is, since a mobile station must receive control cannels of all carriers, the complexity increases according to the number of carriers.

For example, if a base station designates carrier 1 (101) and carrier 104 (107) with respect to one sub-frame as an LTE-A dedicated sub-frame, it cannot transmit

corresponding carriers

1 and 4 and sub frame No. 2 to an LTE mobile station via a downlink. If the base station communicates with the mobile station using multi-carriers, such as

carriers

1 and 4, the mobile station receives controls channels of carrier 1, i.e., PCFICH, PHICH, and PDCCH, and then data of the carrier 1. It also receives PCFICH, PHICH, and PDCCH of carrier 4 and then data of carrier 4. Here, the LTE-A mobile station increase the number of control channel demodulation attempts according to the number of used multi-carriers, compared with an LTE mobile station that cannot use multi-carriers. Therefore, the number of attempts increases in proportional to the increase in the number of used multi-carriers.

Reference number 113 shows that a downlink physical control channel is transmitted via carrier 1 (101) as a primary carrier. Although a downlink physical control channel is transmitted via a primary carrier, PCFICH and PHICH must be transmitted via all carriers.

As shown by

reference numbers

127, 129, 131 and 133, the size of area of a downlink physical control channel is defined as the value of PCFICH transmitted via a primary carrier, so three symbols 135 at the head of four

carriers

103, 105, 107, and 109, and 20 symbols in total are transmitted without PDCCH. In that case, the area of PDCCH of all carriers is determined according to the value of PCFICH provided by the primary carrier, and thus the area of PDCCH of other carriers becomes empty without data to be transmitted, which causes a waste of resources. That is, data downlink physical control channels without information occupy bands, and this brings about a waste of wireless resources.

If a base station transmits downlink physical control channels through the entire bandwidth, although the number of modulation attempts does not increase in the mobile station, the number of wasted downlink physical control channels is greatly increased in comparison with the number of users, which lowers the efficiency. In particular, the control channel reception performance cannot be guaranteed due to low transmission power caused by broadband transmission.

The present invention has been made in view of the above problems, and provides a method and apparatus that can transmit and receive a downlink physical control channel in a downlink frame in a wireless communication system in such way that an LTE mobile station does not perform a reception operation with respect to a corresponding sub-frame and an LTE-A mobile station does not receive downlink physical control channels of a portion of carriers but instead uses the area to transmit data when transmitting a multi-carrier, where the downlink frame containing a sub-frame for the LTE-A mobile station using a multi-carrier or a sub-frame that cannot be received by the LTE mobile station using a single carrier.

In accordance with an exemplary embodiment of the present invention, the present invention provides a method for transmitting downlink physical control channels of a sub-frame using a multi-carrier, the method including: determining whether the sub-frame is a frame for transmitting a broadcast information channel; setting, if the sub-frame is not a frame for transmitting a broadcast information channel, a channel allocation indicator for indicating the number of symbols showing that a packet data control channel is allocated to each carrier of the sub-frame; and transmitting the sub-frame.

In accordance with another exemplary embodiment of the present invention, the present invention provides a method for receiving downlink physical control channels of a sub-frame using a multi-carrier, the method including: receiving the sub-frame; determining whether the sub-frame is a frame for transmitting a broadcast information channel; receiving, if the sub-frame is not a frame for transmitting a broadcast information channel, a packet data control channel according to the number of symbols indicated by a channel allocation indicator of each carrier of the sub-frame; and receiving a downlink shared channel according to the number of symbols.

In accordance with another exemplary embodiment of the present invention, the present invention provides an apparatus for transmitting downlink physical control channels in a wireless communication system of a sub-frame using a multi-carrier, including: a scheduler for scheduling whether a packet data control channel by carriers is transmitted via the sub-frame; a physical control format indicator channel processing unit for generating a channel allocation indicator that indicates the number of symbols showing that the packet data control channel of each carrier of the sub-frame, if the sub-frame is not a frame for transmitting a broadcast information channel; and a transmitting unit for transmitting the sub-frame.

In accordance with another exemplary embodiment of the present invention, the present invention provides an apparatus for receiving downlink physical control channels in a wireless communication system of a sub-frame using a multi-carrier, including: a receiving unit for receiving the sub-frame; a physical control format indicator channel receiving unit for extracting a channel allocation indicator of each carrier of the sub-frame; a packet data control channel receiving unit for receiving a packet data control channel according to the number of symbols indicated by the extracted channel allocation indicator if the sub-frame is not a frame for transmitting a broadcast information channel; and a downlink shared channel receiving unit for receiving downlink shared channel according to the number of symbols.

As described above, if the LTE-A mobile station performs transmitting/receiving operation via multi-carrier, the control channel area between carriers is restricted to reduce the reception complexity of the mobile station but instead the restricted area is used to transmit data, thereby increasing the frequency efficiency. In particular, the mobile station does not perform operations for receiving downlink physical control channels, thereby reducing power consumption. When the LTE-A mobile station using a single carrier transmits and receives an LTE-A system dedicated sub-frame, it can distinguish between the LTE-A system dedicated sub-frame and the existing LTE system sub-frame, through an existing channel. While the LTE mobile station and the LTE-A mobile station are simultaneously managing an LTE-A base station, they can minimize the influence on the scheduling operation.

The features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a view that describes structure of a conventional downlink frame;

FIG. 2 is a view that describes structure of a sub-frame of a downlink frame according to an embodiment of the present invention;

FIG. 3 is a view that describes a downlink frame having sub-frames according to an embodiment of the present invention;

FIG. 4 is a view that describes a sub-frame using a multi-carrier according to an embodiment of the present invention;

FIG. 5 is a flow chart that describes a method for transmitting downlink physical control channels according to an embodiment of the present invention;

FIG. 6 and FIG. 7 is a flow chart that describes a method for receiving downlink physical control channels according to an embodiment of the present invention;

FIG. 8 is a view that describes a sub-frame using a multi-carrier according to another embodiment of the present invention;

FIG. 9 and FIG. 10 is a flow chart that describes a method for transmitting downlink physical control channels according to another embodiment of the present invention;

FIG. 11 and FIG. 12 is a flow chart that describes a method for receiving downlink physical control channels according to another embodiment of the present invention;

FIG. 13 is a view illustrating a configuration of an apparatus for transmitting downlink physical control channels according to an embodiment of the present invention; and

FIG. 14 is a view illustrating a configuration of an apparatus for receiving downlink physical control channels according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention are described in detail with reference to the accompanying drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention less clear.

The terms or words described in the present description and the claims should not be limited by a general or lexical meaning, instead should be analyzed as a meaning and a concept through which the inventor defines and describes the present invention at his most effort, to comply with the idea of the present invention. Therefore, one skilled in the art will understand that the embodiments disclosed in the description and configurations illustrated in the drawings are only preferred embodiments, instead there may be various modifications, alterations, and equivalents thereof to replace the embodiments at the time of filing this application.

In the following description, although embodiments of the present invention are explained based on an LTE system, it should be understood that the present invention is not limited to the embodiments. It will be appreciated that the present invention can also be applied to other wireless communication systems employing base station scheduling.

FIG. 2 is a view that describes structure of a sub-frame of a downlink frame according to an embodiment of the present invention.

Referring to FIG. 2, the total transmission bandwidth 209 is composed of N umber of resource blocks (RBs), N_RB. Each RB is composed of 12 tones 237 arrayed in frequency axis and 14 OFDM symbols 239 in time axis, which is a unit of resource allocation. One sub-frame 211 has a 1 ms duration and is composed of two slots 241.

A reference signal (hereinafter called RS) refers to a signal that is predetermined between a mobile station and a base station and transmitted to the mobile station so that the mobile station can estimate a channel. RS0 233, RS1 229, RS2 231 and RS3 235 are transmitted from

antenna ports

0, 1, 2, and 3, respectively. It is preferable to use a multi-antenna if the number of antenna ports is equal to or greater than 2.

If a transmitting antenna uses only one port, only RS0 233 is used to transmit data but RS1 229 is not transmitted. Also, RS2 231 and RS3 235 are used to transmit data or control signal symbols, respectively. If transmitting antenna ports are defined as two types, RS0 233 and RS1 229 serve to transmit data and RS2 231 and RS 235 are used to transmit data or control signal symbols.

Although the absolute position of a resource element (RE) where a reference signal (RS) is deployed on a frequency axis is differently set according to cells, the relative spacing between RSs are maintained. That is, the spacing between RSs of the same antenna port is retained with 6RE, and the spacing between RS0 233 and RS1 229 and the spacing between RS2 231 and RS3 235 are also maintained with 3RE. The reason the absolute position of an RS is differently set according to cells is to avoid a collision between cells.

A control channel signal is located at the head of one sub-frame on a time axis. In FIG. 2, reference number 213 denotes an area where a control channel signal is located.

A control channel signal can be transmitted via an L number of OFDM symbols at the head of a sub-frame. L may be 1, 2 or 3. If the number of downlink physical control channels is relatively small and thus transmission of a control channel signal can be achieved by one OFDM symbol, only 1 OFDM symbol 1 at the head is used for the transmission of a control channel signal (L=1), and the remaining symbols, i.e., 13 OFDM symbols, are used to transmit data channel signals.

If a control channel signal consumes 2 OFDM symbols, only 2 OFDM symbols at the head are used to transmit a control channel signal (L=2) and the remaining symbols, i.e., 12 OFDM symbols, are used for the transmission of data channel signals.

In addition, if an amount of control channel signal is relatively large and thus 3 OFDM symbols all are used for the transmission of control signals, 3 OFDM symbols at the head are used to transmit a control channel signal (L=3) and the remaining 11 OFDM symbols are used to transmit data channel signals.

L serves as information regarding a deep mapping in a control channel reception operation. Therefore, if L is not received, a control channel signal cannot be recovered.

If a sub-frame is a multi-media broadcast over a signal frequency network (MBSFN) channel, L becomes 2. The MBSFN channel serves to transmit broadcast information.

The reason that a control channel signal is located at the head of a sub-frame is to allow a mobile station to receive a control channel signal and to detect whether a data channel signal is transmitted to itself and, so that it can perform a data channel reception operation. If the mobile station ascertains that there is no data channel signal transmitted to itself, it does not need to receive any data channel signal, thereby saving power required to perform the operation.

A downlink physical control channel (DPCCH) defined in the LTE system is composed of physical control format indicator channels (PCFICH) 101, 105, and 107, physical hybrid ARQ indicator channels (PHICH) 121, 123, and 125, a packet data control channel (PDCCH) 115, etc. In the following description, PCFICH is also called a format indicator channel, PHICH is called an ARQ indicator channel, and PDCCH is called a data control channel.

PCFICH

101, 105, and 107 refer to physical channels to transmit control channel format indicator (CCFI). The CCFI is information that is composed of 2 bits and provides a control channel allocation indicator, i.e., an ‘L’ value. A mobile station needs to receive CCFI to detect the number of symbols allocated to DPCHCH and then receives the symbols. To this end, all mobile stations initially need to receive PCFICH in a sub-frame, except for a case where downlink resources are fixedly allocated thereto. Since it is impossible to detect the L value before the mobile station receives PCFICH. PCFICH needs to be transmitted in the first OFDM symbol. PDFICH is divided into four sub-channels 201, 203, 205 and 207 with 16 sub-carriers and then transmitted over the full bandwidth.

PHICH

221, 223, and 225 refer to physical channels to transmit a downlink ACK/NACK signal. A mobile station receiving the

PHICH

221, 223, and 225 is also transmitting data in an uplink. Therefore, the number of PHICH is proportional to the number of mobile stations that are transmitting data in uplinks. PHICH is transmitted in the first OFDM symbol (L_PHICH=1) or through 3 OFDM symbols (L_PHICH=3). L_PHICH denotes a parameter defined in each cell and is introduced to control the situation that, if the size of a cell is large, it is not sufficient to transmit PHICH through only one OFDM symbol. Configuration information regarding PHICH, such as an amount of channels used and L_PHICH, is provided to all mobile stations through a primary broadcast channel (PBCH) when they initially accesses a cell. Similar to the PCFICH, PHICH is transmitted to a location designated at each cell. Therefore, if a mobile station is linked to a cell and acquires information regarding PBCH, it can receive PHICH irrespective of information regarding other DPCCH.

PDCCH 115 refers to a physical channel that transmits data channel allocation information or power control information. PDCCH may differently set a channel coding rate according to the channel state of a mobile station that is performing a reception operation. PDCCH is fixedly modulated by a quadrature phase shift keying (QPSK) modulation. If it is needed to alter a channel coding rate, the amount of resources used by one PDCCH is required to be changed. If a mobile station is in a good channel state, a high channel coding rate is applied thereto, so as to reduce the amount of resources used thereby. On the contrary, if a mobile station is in a low channel state, the amount of resources used thereby increases to apply a high channel coding rate thereto, so that it can perform a reception operation. The amount of resources consumed by individual PDCCH is determined a unit of control channel element (CCE). CCE is composes of a plurality of resource element groups (REGs) 237. The REG of PDCCH is processed by an interleaver to secure the diversity, and then deployed to a control channel resource.

REG 237 is a unit of control channel resource composed of CCE, PCFICH and PHICH. PCFICH and PHICH use a certain amount of fixed resource that is determined with a group of REGs so that the multiplexing operation and the transmitting diversity can be easily applied to the PDCCH. One PCFICH is composed of N_PCFICH number of REGs. One PHICH is composed of N_PHICH number of REG. N_PCFICH = 4 and N_PHICH = 3 means that PCFICH uses 16 REs and PHICH uses 12 REs.

PHICH employs a code domain multiplexing (CDM) technique to multiplex ACK/NACK signal. In one REG, 8 PHICH signals are processed to 4 real parts and 4 imaginary pats by the CDM, and this format is repeated by N_PHICH times to acquire a frequency diversity gain, so that they can be spaced as far apart as possible on a frequency axis and then transmitted. Therefore, if N_PHICH number of REGs has been used, 8 or less than number of PHICH signals can be composed. In order to exceed 8 PHICH signals, it needs N_PHICH number of other REGs.

After determining the amount of resources and their allocation with respect to the PCFICH and PHICH, a scheduler sets L value, maps a physical control channel, excluded based on the L value, to an REG of an allocated DPCCH, and performs an interleaving operation to acquire a frequency diversity gain.

Interleaving is performed with respect to the total REG of sub-frames that are determined by the L value based on an REG unit of DPCCH. The output of the interleaver of the DPCCH serves to prevent an inter-cell interference caused due to the use of the same interleaver between cells and to a function so that REGs of DPCCH allocated to one or a plurality of symbols can acquire a diversity gain, spacing far apart from a frequency axis. REG composed of the same channels secures an equal distribution between symbols according to channels.

In the following description, a description is provided a downlink frame having sub-frames as described above, with reference to FIG. 3. FIG. 3 is a view that describes a downlink frame having sub-frames according to an embodiment of the present invention.

FIG. 3 shows a portion of downlink radio frame if sub-frames of an LTE system and an LTE-A system are transmitted with

multi-carriers

301, 303, 305, 307, and 309 from one base station.

As shown in FIG. 3,

LTE sub-frames

331, 333, 335, 337, 339, 355, 357, 359, 361, and 363 and LTE-

A sub-frames

341, 349, 343, 345, 347, 351, 353, 365, 367, 369, 371, 373, 375, 377, and 379 are allocated to one radio frame.

Although the LTE-A sub-frame may be located at a certain location, it cannot be transmitted via downlink sub-frame No. 0 (311) and downlink sub-frame No. 5 (321). Since, although an LTE mobile station using a single carrier needs to access a cell so that it coexists with an LTE-A mobile station using a multi-carrier, a default channel for accessing a cell is transmitted via the downlink sub-frame No. 0 (311) and downlink No. 5 (321).

An LTE mobile station and/or an LTE-A mobile station can transmit a particular sub-frame via an uplink, according to the result of the scheduler. That is, an LTE mobile station can use an LTE-A dedicated sub-frame when it performs a transmitting operation via an uplink.

In an embodiment of the present invention, it is assumed that the location of an LTE-A dedicated sub-frame is indicated by an MBSFN sub-frame because the location is transmitted to an LTE-A mobile station by an up-signaling operation but an LTE mobile station does not recognize the LTE-A sub-frame.

If it is needed to transmit PHICH of DPCCH and to perform transmission via an uplink, uplink scheduling information is configured in such a way that they can be received by both the LTE and LTE-A mobile stations in all sub-frames.

That is, LTE and LTE-A mobile stations both can also receive PHICH and uplink scheduling information in an MBSFN sub-frame. This is because a mobile station can transmit a sub-frame via the uplink sub-frame, as described above.

Embodiment 1

FIG. 4 is a view that describes a sub-frame using a multi-carrier according to an embodiment of the present invention.

Referring to FIG. 4, when a DPCCH of a structure using a multi-carrier is transmitted, a DPCCH 413 is transmitted via a primary carrier 411 and a physical downlink shared channel (PDSCH), which is called downlink shared channel in the present invention, is also transmitted to PDCCH areas 413 ~ 421 of a sub-carrier other than the primary carrier.

According to the prior art, the LTE-A dedicated sub-frame serves as an MBSFN sub-frame for the LTE mobile station. To this end, PCFICH of subframes except for a primary carrier needs to be set to ‘2’.

However, all mobile stations attempt to perform a blind decoding by the second symbol of a corresponding sub-frame, thereby wasting resources. Therefore, according to an embodiment of the present invention, the L value of PCFICH is set to ‘4’ and PDSCH is transmitted to an area except for PCFICH and PHICH. If PCFICH is indicated by four, all mobile stations stop receiving PDCCH of a corresponding sub-frame. PHICH can be received, according to uplink scheduling information previously scheduled, irrespective of PCFICH.

Therefore, although a base station transmits PDSCH to a PDCCH area, the mobile station does not attempt to receive the PDCCH. Furthermore, since the LTE-A mobile station also provide scheduling information regarding all carriers in a primary carrier, it does not need to additional perform al receiving operation that generated during the multi-carrier transmission.

In a control channel structure transmitting PDCCH to the primary carrier descried above, a base station indicates information regarding an LTE-A sub-frame and information regarding a primary sub-frame, by sub-frame indexes of each radio frame, to an LTE-A mobile station. PDCCH is transmitted to only the sub-frame indicated by the base station and all LTE-A mobile stations can receive control signals via the primary carrier. The primary carrier can provide it to a mobile station through a carrier of the lowest or highest carrier index in a corresponding LTE-A sub-frame. Alternatively, the primary carrier may differently indicate it by sub-frames with an uplink signaling.

The following table 1 describes gains according to a method for transmitting downlink physical control channels according to an embodiment of the present invention.

Table 1

	2 carriers	3 carriers	4 carriers	5 carriers
Gain	7.1%	9.5%	10.7%	11.4%

If each carrier has the same bandwidth, table 1 shows gains and spectral efficiency with respect to each carrier when PDCCH (3 symbols) are transmitted. Corresponding gains do not consider overhead of PCFICH and PHICH. That is, as shown by reference number 421, the frequency of additional reception attempts, performed by sub-carriers to receive PDCCH, increases in proportional to the number of transmitted multi-carriers. On the contrary, as shown by reference number 413, the embodiment according to the present invention can reduce the frequency of additional reception attempts.

Meanwhile, if a mobile station using a multi-carrier does not perform multi-carrier transmission as an exceptional case of the first embodiment of the present invention, a base station needs to consider a case that information regarding an uplink and other control channel information is transmitted or received to and from the mobile station. In that case, the base station set PDFICH of a corresponding sub-frame to 2 and then transmits it to the mobile station. Since an actual PDSCH uses control information regarding the primary carrier, the mobile station starts to transmit the PDSCH at max {2, L}.

FIG. 5 is a flow chart that describes a method for transmitting downlink physical control channels according to an embodiment of the present invention.

Steps

503, 525, and 527 are repeated when a base station performs steps 505 to 523 with respect to each sub-carrier that will be transmitted.

The base station checks whether a sub-frame of a carrier that will be currently transmitted is an MBSFN sub-frame (505).

If the base station ascertains that a sub-frame of a carrier that will be currently transmitted is an MBSFN sub-frame at 505, the procedure proceeds to step 507. Otherwise, it proceeds to step 533.

That is, if the base station ascertains that a sub-frame of a carrier is not an MBSFN sub-frame at 505, it determines an L value of PCFICH using scheduling information and performs a mapping operation (533). The base station performs a mapping operation with respect to PHICH (535). After that, the base station performs a mapping operation with respect to PDCCH until the L-1-th symbol (537). The base station performs a mapping operation with respect to PDSCH from the L-th symbol (539).

On the contrary, if the base station ascertains that a sub-frame of a carrier is an MBSFN sub-frame at 505, it determines whether a sub-frame that will be currently transmitted is a primary carrier (507). If the base station ascertains that a sub-frame is a primary carrier at 507, the procedure proceeds to step 517. Otherwise, the procedure proceeds to step 511.

That is, if the base station ascertains that a sub-frame is a primary carrier at 507, it determines L value of PCFICH using scheduling information regarding a multi-carrier (517). After that, the base station maps PHICH to a corresponding area (519). The base station performs a mapping operation with respect to PDCCH until the L-1-th symbol (521). The base station performs a mapping operation with respect to PDSCH from the L-th symbol (523).

On the contrary, if the base station ascertains that a sub-frame is not a primary carrier at 507, it sets the L value of PCFICH to 4 (511). After that, the base station performs a mapping operation with respect to PHICH (513). The base station performs a mapping operation with respect to PDSCH from 0^th symbol, irrespective of the L value of PDFICH of a primary carrier corresponding to a corresponding sub-carrier (515). If PDCCH has been transmitted using the primary carrier, only PDSCH is transmitted to sub-frames of a sub-carrier.

In the following description, a detailed description is provided regarding a method for receiving downlink physical control channels in a mobile station according to a first embodiment of the present invention, with reference to FIGS. 6 and 7.

FIG. 6 and FIG. 7 is a flow chart that describes a method for receiving downlink physical control channel according to an embodiment of the present invention. In an embodiment of the present invention, it is assumed that a mobile station has received a system information block (SIB) from a corresponding base station and known the location of an MBSFN sub-frame.

As shown in FIGS. 6 and 7, the mobile station checks whether a current sub-frame is an MBSFN sub-frame (605). If the mobile station ascertains that a current sub-frame is an MBSFN sub-frame at 605, it proceeds to step 607. Otherwise, the mobile station proceeds to step 649 as shown in FIG. 7.

That is, if the mobile station ascertains that a current sub-frame is not an MBSFN sub-frame at 605, it receives PCFICH of its currently camping sub-carrier and extracts an L value (649). After that, the mobile station receives PDCCH according to the L value and then PHICH (651). The mobile station receives PDSCH according to the extracted L value, from the L-th symbol, referring to PDCCH (653). Next, the mobile station receives the next sub-frame (655).

If the LTE-A mobile station uses a plurality of carriers, it receives PDCCH via a primary carrier and data via the remaining areas according to the L value. On the contrary, if the LTE mobile station and the LTE-A mobile station are a mobile station using a single carrier, they ignores a corresponding sub-frame (i.e., blank) and receive the next sub-frame since there is no DPCCH if L=1.

On the contrary, if the mobile station ascertains that a current sub-frame is an MBSFN sub-frame at 605, it determines whether a mobile station is an LTE mobile station or an LTE-A mobile station (607). If a mobile station is an LTE mobile station at 607, the procedure proceeds to step 641 as shown in FIG. 7. If a mobile station is an LTE-A mobile station at 607, the procedure proceeds to step 609.

That is, if a mobile station is an LTE mobile station at 607, it receives PCFICH and extracts an L value (641). After that, the mobile station determines whether the extracted L value is 2 (643). If the extracted L value is 2 at 643, the mobile station receives PDCCH and PHICH (645). On the contrary, if the extracted L value is not 2 at 643, it ignores a corresponding sub-frame (i.e., blank) and proceeds to step 655.

Referring to

steps

643 and 645, if a current sub-frame is an MBSFN sub-frame, the LTE mobile station receives the L value of PCFICH from a linked carrier j. If the L value is 2, the LTE mobile station receives PDCCH and PHICH until the L-1-th symbol. On the contrary, if the L value is not 2, the LTE mobile station stops receiving a current sub-frame.

On the contrary, if a current sub-frame is an MBSFN sub-frame and a mobile station is an LTE-A mobile station at 607, the mobile station switches a reception frequency with a primary carrier, receives PCFICH and extracts an L value (609). The mobile station receives PDCCH and PHICH according to the extracted L value (611).

Steps

613, 629, and 631 relate to a process for receiving a sub-frame according to each carrier, based on the PDCCH received at step 611. That is, the mobile station checks subframes from the first carrier at 613 and the last carrier M at 631. To this end, the parameter i is increased to identify the next carrier (629). i denotes a parameter that indicates the carrier index and is varied in a range of 1~M. These processes are performed as follows.

First, the mobile station determines whether a corresponding carrier is a primary carrier (615).

If the mobile station ascertains that a corresponding carrier is not a primary carrier at 615, it receives PCFICH (617), and then PHICH (619). After that, the mobile station determines whether the L value of PCFICH, received at 617, is 2 (621). If the mobile station ascertains that the L value of PCFICH is 2 at 621, it compares the L value of the primary carrier with 2 of the PCFICH of a current carrier if a corresponding sub-frame contains a transmission resource allocated to itself. After that, the mobile station receives PDCCH until L-1-th symbol according to L larger than 2, and PDSCH from the L-th symbol (623). On the contrary, if the mobile station ascertains that the L value of PCFICH is not 2 at 621, it receives PDSCH from 0^th symbol if a corresponding sub-frame contains a transmission resource allocated to itself (625). The mobile station can detect whether there is a transmission resource allocated to itself via the PDCCH received at 611.

Meanwhile, if the mobile station ascertains that a corresponding carrier is a primary carrier at 615, it receives DPCCH until the L-1-th symbol and data channels from the L-th symbol (627).

After receiving all carriers, the mobile station receives the next sub-frame (655), and then repeats the processes described above.

Embodiment 2

In the following description, a description is provided regarding a method for transmitting downlink physical control channels according to another embodiment of the present invention with reference to FIGS. 8 to 12.

FIG. 8 is a view that describes a sub-frame using a multi-carrier according to another embodiment of the present invention.

In an embodiment of the present invention, when scheduling information is needed to be transmitted by using carriers that are used for multi-carrier transmission, other than a primary carrier, the amount of DPCCH of a corresponding sub-frame is set to 2 (723), irrespective of the L value of PCFICH of a primary carrier.

Although PCFICH of a sub-frame, transmitted with a corresponding carrier, is set to 2 (707, 723), since the actually transmitted PDSCH uses control information regarding the primary carrier, a transmission beginning time point of the PDSCH and a transmission area of PDCCH are defined according to the L value of the primary carrier. However, the primary carrier can schedule a number of mobile stations and the L value is proportional to the number of scheduled users. Therefore, the carrier where PDFICH is actually set to 2 is very likely to be transmitted without using the third symbol, which causes resource waste.

In order to prevent such resource waste, regarding the

carriers

707 and 723 where PCFICH is set to 2, a mobile station receives PDCCH until the L-2-th symbol, i.e., symbol 1, irrespective of the L value of the primary carrier and then uses PDSCH from the L-th symbol.

In the following description, a description is provided regarding a method for transmitting downlink physical control channels in a base station, according to an embodiment of the present invention, with reference to FIGS. 9 and 10.

FIG. 9 and FIG. 10 is a flow chart that describes a method for transmitting downlink physical control channels according to another embodiment of the present invention.

Steps

803, 841, and 843 are repeated when a base station performs steps 805 to 829 with respect to each sub-carrier that will be transmitted.

The base station checks whether a sub-frame of a carrier that will be currently transmitted is an MBSFN sub-frame (805). If the base station ascertains that a sub-frame of a carrier that will be currently transmitted is an MBSFN sub-frame at 805, the procedure proceeds to step 807. Otherwise, it proceeds to step 833.

That is, if the base station ascertains that a sub-frame of a carrier is not an MBSFN sub-frame at 805, it determines an L value of PCFICH using scheduling information and performs a mapping operation (833). The base station performs a mapping operation with respect to PHICH (835). After that, the base station performs a mapping operation with respect to PDCCH until the L-1-th symbol (837). The base station performs a mapping operation with respect to PDSCH from the L-th symbol (839).

On the contrary, if the base station ascertains that a sub-frame of a carrier is an MBSFN sub-frame at 805, it determines whether a sub-frame that will be currently transmitted is a primary carrier (807). If the base station ascertains that a sub-frame is a primary carrier at 807, the procedure proceeds to step 823. Otherwise, the procedure proceeds to step 811 as shown in FIG. 10.

That is, if the base station ascertains that a sub-frame is a primary carrier at 807, it determines an L value of PCFICH using scheduling information regarding a multi-carrier (823). After that, the base station maps PHICH to a corresponding area (825). The base station performs a mapping operation with respect to PDCCH until the L-1-th symbol (827). The base station performs a mapping operation with respect to PDSCH from the L-th symbol (829).

On the contrary, if the base station ascertains that a sub-frame is not a primary carrier at 807, it sets the L value of PCFICH to 2 or 4 (811), as shown in Fig. 10. Alternatively, as described above, if the base station needs to transmit scheduling information using a carrier other than a primary carrier, it sets the L value of PCFICH to 2.

After that, the base station performs a mapping operation with respect to PHICH (813). The base station determines whether the L value of PCFICH of a primary carrier is 2 or 4 (815). That is, if L is 4 at 815, the base station performs a mapping operation with respect to PDSCH from the L-3-th symbol, i.e., the 0^th symbol (819). On the contrary, if L is 2 at 815, the base station performs a mapping operation with respect to PDSCH from the L-1-th symbol, i.e., the 0^th symbol (821).

FIG. 11 and FIG. 12 is a flow chart that describes a method for receiving downlink physical control channels according to another embodiment of the present invention.

In an embodiment of the present invention, it is assumed that a mobile station has received a system information block (SIB) from a corresponding base station and known the location of an MBSFN sub-frame (903).

The mobile station receives a downlink frame and checks whether a current sub-frame is an MBSFN sub-frame (905). If the mobile station ascertains that a current sub-frame is an MBSFN sub-frame at 905, it proceeds to step 907. Otherwise, the mobile station proceeds to step 953 as shown in FIG. 12.

That is, if the mobile station ascertains that a current sub-frame is not an MBSFN sub-frame at 905, it receives PCFICH of its currently camping sub-carrier and extracts an L value (953). After that, the mobile station receives PDCCH according to the L value and then PHICH (955). The mobile station receives PDSCH according to the extracted L value, from the L-th symbol, referring to PDCCH (957). Next, the mobile station receives the next sub-frame (959).

On the contrary, if the mobile station ascertains that a current sub-frame is an MBSFN sub-frame at 905, it determines whether a mobile station is an LTE mobile station or an LTE-A mobile station (907). If a mobile station is an LTE mobile station at 907, the procedure proceeds to step 945 as shown in FIG. 12. If a mobile station is an LTE-A mobile station at 907, the procedure proceeds to step 909.

That is, if a mobile station is an LTE mobile station at 907, it receives PCFICH and extracts an L value (945). After that, the mobile station determines whether the extracted L value is 2 (949). If the extracted L value is 2 at 949, the mobile station receives PDCCH and PHICH (951). On the contrary, if the extracted L value is not 2 at 949, proceeds to step 959. That is, if the current sub-frame is an MBSFN, the LTE mobile station receives the L value of PCFICH from a linked carrier j. If the L value is 2, the LTE mobile station receives PDCCH and PHICH until the L-1-th symbol. On the contrary, if the L value is not 2, the LTE mobile station stops receiving a current sub-frame.

On the contrary, if a current sub-frame is an MBSFN sub-frame and a mobile station is an LTE-A mobile station at 907, the mobile station switches a reception frequency with a carrier k serving as a primary carrier, receives PCFICH and extracts an L value (909). The mobile station receives PDCCH and PHICH according to the extracted L value (911).

Steps

913, 929, and 931 relate to a process for receiving each carrier of a sub-frame according to on the PDCCH received at step 911. That is, the mobile station checks a primary carrier and carriers from 1 to M. These processes are performed as follows.

First, the mobile station determines whether a corresponding carrier is a primary carrier (915).

If the mobile station ascertains that a corresponding carrier is not a primary carrier at 915, it receives PCFICH (917), and then PHICH (919). After that, the mobile station determines whether the L value of PCFICH, received at step 917, is 2 (921). If the mobile station ascertains that the L value of PCFICH is 2 at 921 and a corresponding sub-frame contains a transmission resource allocated to the mobile station, it receives PDCCH until the L-1-th symbol, referring to the L value of PCFICH of a current carrier, i.e., 2, and then PDSCH from the 2^nd symbol (925). On the contrary, if the mobile station ascertains that the L value of PCFICH is not 2 at 921 and a corresponding sub-frame contains a transmission resource allocated to the mobile station, it receives PDSCH from the 3^rd symbol (923). The mobile station can detect whether there is a transmission resource allocated to itself via the PDCCH received at 911.

Meanwhile, if the mobile station ascertains that a corresponding carrier is a primary carrier at 915, it receives DPCCH until the L-1-th symbol and PDSCH from the L-th symbol (927).

After receiving all carriers, the mobile station receives the next sub-frame (959), and then repeats the processes described above.

In the following description, apparatus for transmitting downlink physical control channels and an apparatus for receiving downlink physical control channels are explained in detail with reference to FIGS. 13 and 14.

FIG. 13 is a view illustrating a configuration of an apparatus for transmitting downlink physical control channels according to an embodiment of the present invention.

Referring to FIG. 13, the control channel transmitting apparatus of a base station establishes a downlink physical control channel (DPCCH), and includes a scheduler 1001, a PDFICH processing unit 1005, a PHICH processing unit 1007, and a PDCCH processing unit 1009. When establishing DPCCH, the apparatus may further include a reference symbol (RS) processing unit 1003 for transmitting RS symbols previously agreed between the base station and the mobile station.

In an embodiment of the present invention, the control channel transmitting apparatus may further include a PDSCH processing unit 1013 for processing PDCCH. When establishing PDCCH, the control channel transmitting apparatus may further include an RS processing unit 1011 for transmitting RS symbols previously agreed between the base station and the mobile station.

In an embodiment of the present invention, the control channel transmitting apparatus may further include a first multiplexer 1015 for multiplexing DPCCHs, a second multiplexer 1017 for multiplexing PDCCHs, a time domain multiplexer 1019 for multiplexing the multiplexed DPCCHs and the PDCCHs in a time domain, and a transmitting unit (Tx) 1021 for transmitting the multiplexed DPCCHs and the PDCCHs to the mobile station.

The scheduler 1001 determines a mapping rule by DPCCHs based on multi-carrier transmission information, MBSFN information, and the number of PHICHs, and set an amount of symbols of the DPCCHs that will be used according to the information. That is, the scheduler 1001 determines an L value of PCFICH. When the L value is set, the scheduler 1001 determines whether PDCCH is applied to a corresponding sub-frame and then controls the PDCCH processing unit 1009.

In an embodiment of the present invention, the scheduler 1001 controls the PCFICH processing unit 1005 and the PDCCH processing unit 1009, so that PDCCH of all carriers can be allocated to a primary carrier of one of the sub-frames using multi-carriers. The scheduler 1001 determines whether PDCCH is allocated to a sub-carrier and then controls PCFICH processing unit 1005 and PDCCH processing unit 1009.

That is, the scheduler 1001 controls PCFICH processing unit 1005 so that PDCCHs can be allocated to the primary carrier by the L value (for example, L = 1~3), and then controls the PDCCH processing unit 1009 so that the PDCCH can be contained in the carrier according to a corresponding L value. If PDCCH is not transmitted via sub-carriers, the scheduler 1001 controls the PCFICH processing unit 1005 so that the L value of the PCFICH can be set to a particular value, and then controls the PDCCH processing init 1009 so that the PDCCH cannot be contained in the sub-carriers. In particular, if the scheduler 1001 needs to transmit PDCCH via a sub-frame of a sub-frame using multi-carriers, it controls the PCFICH processing unit 1005 so that the L value of PCFICH of a sub-carrier can be set to a particular value.

The PDFICH processing unit 1005 generates a PDFICH signal, where an L value is generated under the control of the scheduler 1001. In an embodiment of the present invention, the PDFICH processing unit 1005 can set an L value of sub-frames to 4 under the control of the scheduler 1001, where the L value of sub-frames correspond to an L value of a primary carrier that is used to perform communication via multi-carriers. If a mobile station liked to a base station without using multi-carriers, it sets PCFICH of a corresponding sub-frame to 2 and then transmits information regarding an uplink and information other DPCCHs.

The PHICH processing unit 1007 collects 8 PHICH signals from each PHICH signal generator, and generates and outputs a CDM. The PHICH signal refers to a downlink acknowledgement/Non-acknowledgement (ACK/NACK) signal.

The PDCCH processing unit 1009 includes a PDCCH signal generator for generating PDCCH signals to be transmitted to different mobile stations. The scheduler 1001 determines the number of CCES occupied by one PDCCH. If the PDCCH processing unit 1009 needs to transmit PDCCH, it performs an interleaving operation under the control of the scheduler 1001.

FIG. 14 is a view illustrating a configuration of an apparatus for receiving downlink physical control channel according to an embodiment of the present invention.

Referring to FIG. 14, the control channel receiving apparatus includes a receiving unit (Rx) 1101 for converting a received signal to a base band signal and outputting it, a time domain de-multiplexer 1105 for de-multiplexing the base band signal to PDCCHs and DPCCHs, a third multiplexer 1107 for separating the PDCCHs to RS signals and PDSCHs and outputting them, and a fourth multiplexer 1109 for separating the DPCCHs to RS signals, PHICHs, and PDCCHs and outputting them.

In an embodiment of the present invention, the control channel receiving apparatus serves to receive DPCCHs and further includes a PCFICH receiving unit 1103, a channel estimator 1115, a PHICH receiving unit 1117, and PDCCH receiving unit 1119.

In an embodiment of the present invention, the control channel receiving apparatus may further include a channel estimator 1111 and a PDSCH receiving unit 1113.

When the receiving unit (Rx) 1101 converts a received signal to a base band signal and outputs it, the PCFICH receiving unit 1103 receives a PCFICH and extracts an L vale therefrom. The areas of PHCCH and PDSCH of all carriers are discriminated according to the extracted L value.

The channel estimator 1115 estimates a channel using the RS signals output from the fourth multiplexer 1109. The PHICH receiving unit 1117 and PDCCH receiving unit 1119 receive PHICH and PDCCH, respectively, according to the channel value estimated by the channel estimator 1115 and the L value of PCFICH. In particular, the PDCCH receiving unit 1117 determines whether PDCCH is received with respect to the use or defined area of PDCCH, according to the L value. If PDCCH receiving unit 1117 needs to receive PDCCH, it performs a de-interleaving operation, extracts a signal by de-mapping the PDCCH, and then decodes PDCCH.

In an embodiment of the present invention, when performing a transmitting/receiving operation using a multi-carrier, the PDCCH receiving unit 1117 receives PDCCH in a primary carrier and detects RE, allocated to all carriers including the primary carrier, from the received PDCCH. That is, when the PDCCH receiving unit 1117 performs a transmitting/receiving operation using a multi-carrier, it receives PDCCHs from the primary carrier according to a channel allocation indicator L that is extracted from a primary carrier of a sub-frame. The PDCCH receiving unit 1117 may receive PDSCH via a corresponding sub-carrier according to a channel allocation indicator L that is extracted from a sub-carrier.

If a mobile station using a signal carrier performs a camping operation with respect to a corresponding sub-carrier, the PDCCH receiving unit 1119 receives PDCCH via a corresponding sub-carrier according to a channel allocation indicator L that the PCFICH receiving unit 1103 extracts from the corresponding sub-carrier. If PDCCH does not exist in the sub-carrier, the PDCCH receiving unit 1119 ignores the sub-carrier (which is called a blank process) according to the channel allocation indicator L.

The channel estimator 1111 estimates a channel using an RS signal output from the third multiplexer 1107. The PDSCH receiving unit 1113 can detect an area, allocated to itself, according to the L value of PCFICH and the reception result of PDCCH. Therefore, the channel estimator 111 can receive data from estimated channel value, through RE.

In an embodiment of the present invention, when the PDSCH receiving unit 1113 performs a transmission/reception operation using a multi-carrier, it can detect RE allocated to all carriers from PDCCH that is received via a primary carrier.

If a mobile station using a signal carrier performs a camping operation with respect to a corresponding sub-carrier, the PDSCH receiving unit 1113 can receive PDSCH according to the PDCCH that the PCFICH receiving unit 1103 receives via a corresponding sub-carrier.

Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may be apparent to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined in the appended claims.

Claims

A method for transmitting downlink physical control channels of a sub-frame using a multi-carrier, the method comprising:determining whether the sub-frame is a frame for transmitting a broadcast information channel;setting, if the sub-frame is not a frame for transmitting a broadcast information channel, a channel allocation indicator for indicating the number of symbols showing that a packet data control channel is allocated to each carrier of the sub-frame; andtransmitting the sub-frame.
The method of claim 1, further comprising:setting, if the sub-frame is a frame for transmitting a broadcast information channel, a channel allocation indicator for indicating the number of symbols showing that a packet data control channel is transmitted via a primary carrier of the frame for transmitting a broadcast information channel.
The method of claim 1, further comprising:setting, if the sub-frame is a frame for transmitting a broadcast information channel, a channel allocation indicator for indicating that a packet data control channel is not transmitted to a sub-carrier of the frame for transmitting a broadcast information channel.
A method for receiving downlink physical control channels of a sub-frame using a multi-carrier, the method comprising:receiving the sub-frame; determining whether the sub-frame is a frame for transmitting a broadcast information channel;receiving, if the sub-frame is not a frame for transmitting a broadcast information channel, a packet data control channel according to the number of symbols indicated by a channel allocation indicator of each carrier of the sub-frame; andreceiving a downlink shared channel according to the number of symbols.
The method of claim 4, wherein receiving a packet data control channel is ignoring carriers through which the packet data control channel is not transmitted according to the number of symbols indicated by the channel allocation indicator.
The method of claim 4, further comprising:selectively receiving a packet data control channel according to the channel allocation indicator if a mobile station uses a single carrier and the sub-frame is the frame for transmitting a broadcast information channel.
The method of claim 5, further comprising:receiving a packet data control channel, according to a channel allocation indicator, via a primary carrier, if a mobile station uses a multi-carrier and the sub-frame is the frame for transmitting a broadcast information channel; andreceiving a downlink shared channel according to the number of symbols of the downlink shared channel indicated by the channel allocation indicator of each carrier.
An apparatus for transmitting downlink physical control channels in a wireless communication system of a sub-frame using a multi-carrier, comprising:a scheduler for scheduling whether a packet data control channel (PDCCH) by carriers is transmitted via the sub-frame;a physical control format indicator channel processing unit for generating a channel allocation indicator that indicates the number of symbols showing that the packet data control channel of each carrier of the sub-frame, if the sub-frame is not a frame for transmitting a broadcast information channel; anda transmitting unit for transmitting the sub-frame.
The apparatus of claim 8, wherein, if the sub-frame is a frame for transmitting a broadcast information channel, a channel allocation indicator indicates the number of symbols showing that the packet data control channel is transmitted via a primary carrier of the frame for transmitting a broadcast information channel.
The apparatus of claim 8, wherein, if the sub-frame is a frame for transmitting a broadcast information channel, a channel allocation indicator indicates that packet data control channel is not transmitted to a sub-carrier of the frame for transmitting a broadcast information channel.
An apparatus for receiving downlink physical control channels in a wireless communication system of a sub-frame using a multi-carrier, comprising:a receiving unit for receiving the sub-frame;a physical control format indicator channel receiving unit for extracting a channel allocation indicator of each carrier of the sub-frame;a packet data control channel receiving unit for receiving a packet data control channel according to the number of symbols indicated by the extracted channel allocation indicator if the sub-frame is not a frame for transmitting a broadcast information channel; anda downlink shared channel receiving unit for receiving downlink shared channel according to the number of symbols.
The apparatus of claim 11, wherein the packet data control channel receiving unit ignores carriers through which the packet data control channel is not transmitted according to the number of symbols indicated by the channel allocation indicator.
The apparatus of claim 11, wherein, if a mobile station uses a single carrier and the sub-frame is the frame for transmitting a broadcast information channel, the packet data control channel receiving unit selectively receives a packet data control channel according to the channel allocation indicator.
The apparatus of claim 11, wherein, if a mobile station uses a multi-carrier and the sub-frame is the frame for transmitting a broadcast information channel, the packet data control channel receiving unit receives a packet data control channel, according to a channel allocation indicator, via a primary carrier.
The apparatus of claim 11, wherein the downlink shared channel receiving unit receives a downlink shared channel according to the number of symbols of the downlink shared channel indicated by the channel allocation indicator of each carrier.