KR20080086317A - Method for mapping resource of physical downlink control channel of wireless communication system and apparatus for transmitting/receiving physical downlink control channel mapped thereby - Google Patents

Abstract

A method for mapping resources of a physical downlink control channel of a wireless communication system and an apparatus for transmitting/receiving a mapped physical downlink control channel are provided to maximize an interference diversity among base stations by interleaving control channels by base station or sub-frame and mapping a CE or LE to an RE by OFDM symbol. A plurality of control channels are channel-coded(110). One or more control channel elements are allocated to each of the multiple channel-coded control channels. The allocated control channel elements are concatenated(120). The concatenated control channel elements are interleaved(130). The interleaved control channel elements are mapped to resource elements(140). The mapping of the interleaved control channel elements to the resource elements includes configuring each of the interleaved control channel elements with one or more local elements, obtaining a control channel element index of the local elements and interleaving the local elements, and mapping the interleaved local elements to resource elements by base station, subframe and OFDM according to each control channel element index.

Description

Resource mapping method of physical downlink control channel and transmitting / receiving device of mapped physical downlink control channel in wireless communication system }

1 is a diagram illustrating a resource element mapping process of a physical downlink control channel according to the present invention;

2 is a diagram illustrating a process of mapping a control channel element and a resource element of a physical downlink control channel according to the present invention;

3 is a diagram illustrating an apparatus for transmitting a physical downlink control channel according to the present invention;

4 is a diagram illustrating a method for transmitting a physical downlink control channel according to the present invention;

5 is a diagram illustrating an apparatus for receiving a physical downlink control channel according to the present invention;

6 is a diagram illustrating a method of receiving a physical downlink control channel according to the present invention.

7 is a diagram showing a method of transmitting data to a plurality of users in a system using an orthogonal frequency division multiple access scheme according to the prior art.

The present invention relates to a method and apparatus for efficiently operating a control channel while obtaining maximum interference diversity in a wireless communication system, and in particular, a physical downlink control channel of a wireless communication system using an orthogonal frequency division multiple access method. Channel (PDCCH) relates to a method for efficiently mapping a frequency / time resource and a mapping device thereof.

In recent mobile communication systems, orthogonal frequency division multiplexing (hereinafter referred to as " OFDM ") has been actively studied as a useful method for high-speed data transmission in wired / wireless channels. The OFDM method is a method of transmitting data using a multi-carrier, and a plurality of sub-carriers having mutually orthogonality by converting symbol strings input in parallel in parallel. In other words, it is a type of Multi Carrier Modulation (MCM) scheme that modulates and transmits a plurality of sub-carrier channels. Orthogonal frequency division multiple access is a system for classifying multiple users through the plurality of subcarriers while taking the OFDM as a basic transmission scheme, that is, a system supporting multiple users by assigning different subcarriers to different users. Orthogonal Frequency Division Multiplex Access, hereinafter referred to as " OFDMA "

FIG. 7 illustrates an example of a method of transmitting data to multiple users in a system using the orthogonal frequency division multiple access scheme. Referring to FIG. 7, the horizontal axis represents the time axis and the vertical axis represents the frequency axis. Reference numeral 701 denotes a unit for reallocating resources on the time axis, and the resource allocation time unit is generally composed of a plurality of OFDM symbols. Hereinafter, a time unit for reallocating the resource will be referred to as a sub-frame. Reference numerals 702, 703 and 704 denote the first band, the N-1 st band and the N th band, respectively, when the total system band is divided by N. FIG. Each band typically consists of a plurality of subcarriers. As shown in FIG. 7, in the conventional OFDM system, a time and frequency resource is composed of a plurality of resource blocks, and a resource is allocated to a plurality of users in units of the resource block. . In the above, one resource block indicates resources included in one subframe and one band in FIG. 7. For example, assuming that one band consists of 12 subcarriers and one subframe consists of 14 OFDM symbols, 12 x 14 = 168 time and frequency resources in one resource block. . In the above description, one subcarrier in a minimum unit of time and frequency resources, that is, one OFDM symbol is commonly referred to as a resource element (hereinafter, referred to as a "RE").

As described above, in a system using a conventional OFDM scheme, resources are allocated to one or a plurality of terminals by using a resource block as a basic unit in every subframe, and a base station normally allocates resources to the terminals in every subframe. Inform A channel for transmitting resource allocation information for each subframe is commonly referred to as a shared control channel, a physical downlink control channel (PDCCH), and so on. Typically, the control channel may include various other information in addition to the resource allocation information, but a detailed description thereof will be omitted in this document. Typically, information transmitted through a control channel including the resource allocation information is called control information. Typically, one control channel includes resource allocation information for one terminal. Therefore, when resources are simultaneously allocated to a plurality of terminals in an arbitrary subframe, a plurality of control channels are transmitted.

In general, control channels for various users generated at the base station are mapped to frequency / time resource (RE) of the OFDM system in a TDM / FDM manner through respective channel coding and interleaving and transmitted to each terminal. The control channels transmitted in this way have the same resource mapping structure for each base station and for each subframe. Resource mapping in the above means that the control channels are mapped to a physical RE. For example, when five control channels are transmitted in any subframe, the RE mapping of the five control channels is the same for each base station. Therefore, when interference occurs between control channels of each base station, there is no randomization effect and thus a performance degradation may occur. In other words, any one control channel may be subject to some strong interference statistically, which may lead to performance degradation.

Accordingly, an object of the present invention for solving the above problems of the prior art is the physical downlink control of a wireless communication system for reducing the interference of physical downlink control channels of other base stations with respect to the physical downlink control channel of any base station in a wireless communication system. It is to provide a resource mapping method of the channel.

Another object of the present invention is to provide an apparatus for transmitting a physical downlink control channel mapped according to a predetermined method in order to reduce interference of physical downlink control channels of other base stations with respect to a physical downlink control channel of a base station in a wireless communication system. It is.

Another object of the present invention is to provide an apparatus for receiving a physical downlink control channel mapped according to a predetermined method in order to reduce interference of physical downlink control channels of other base stations with respect to a physical downlink control channel of a base station in a wireless communication system. It is.

The resource mapping method of the control channel proposed by the present invention first defines a control channel element (Control Channel Element: CCE, hereinafter simply referred to as Control Element: "CE") which is a resource allocation unit for control channel transmission. . It should be noted that the CE is different from the resource block. That is, the resource block is a resource allocation unit for data transmission, and the CE is an allocation unit for resources used for control channel transmission. When one or a plurality of control channel transmissions are determined by a predetermined scheduling procedure in any subframe, one or more CEs are allocated to each of the control channels, and all or some of the plurality of CEs are concatenated. The concatenated CEs are interleaved in a manner unique to each base station. The interleaved CEs are mapped to REs. The RE mapping procedure may also be performed through a method unique to each base station.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

1 is a view illustrating a RE mapping process of a physical downlink control channel according to the present invention. FIG. 1 illustrates an example in which six control channels are transmitted to six UEs in a subframe. The six control channels include resource allocation information for each of the six terminals. Hereinafter, the six control channels will be referred to as control channel 1, control channel 2, ..., control channel 6. Resource allocation information for each of the six terminals goes through a predetermined channel encoding process in step 110. For example, a convolutional encoding process is performed. Next, one or more CEs are allocated to each control channel. As described above, the CE is a resource allocation unit for control channel transmission. One CE includes a plurality of logical REs. In the above-mentioned logical RE, each CE is mapped to an actual physical RE, since the various implementations may vary depending on the mapping method. For example, one CE consists of 36 logical REs. This means that 36 modulation symbols can be transmitted through the single CE. Reference numerals 121 to 126 show examples in which one or a plurality of CEs are allocated to each control channel as described above. In the example of FIG. 1, one, two, three, two, one, and one CE are assigned to each of the control channels 1 to 6. The reason for assigning different numbers of CEs to different control channels as described above is that the channel environment (received signal to noise ratio) of each terminal is different. For example, the terminals receiving the control channels 1 (121), 5 (125), and 6 (126) have a good channel environment and can transmit control information through only one CE, that is, 36 modulation symbols. The terminal receiving the control channel 3 123 transmits control information through 108 modulation symbols corresponding to three CEs because the channel environment is not good. In the example of FIG. 1, a total of 10 CEs are used to transmit control channels, but the total number of CEs is variable every subframe. All CEs including the control channel as described above are concatenated as shown by reference numeral 120 of FIG. 1. Interleaving or permutation is applied to the concatenated CEs (130). If the interleaving process is different for each cell, it is easy to randomize the CE and RE mapping methods for each base station, thereby randomizing the interference from neighboring base stations in each control channel transmission. Will be obtained.

Hereinafter, the interleaving process of 130 will be described in detail. Each CE connected in step 120 of FIG. 1 is composed of a plurality of Logical Elements (LEs) 127, and the CE indexes of the respective LEs 127 are represented by Equation 1 below.

Interleaving of each LE belonging to each CE is possible in any way and is not limited to a specific method. As a result, the LEs belonging to each CE are interleaved by Equation 2 below.

k _{interleavedLE} = f _interleaving (i _LE )

In the above formula, f _interleaving (.) Means an interleaving function.

PBRO (Pruned Bit Reversal Order) permutation can be used as the method of randomly dropping N _LE LEs and the nearest LEs. The generated PBROs have different offsets for each base station and subframe. Here, Offset _{sector, subframe_index} indicates an offset of PBRO for each base station and for each subframe. The index of each LE after interleaving may be expressed as in Equation 3 below.

k _{interleavedLE} = f _interleaving ((i _LE + Offset _{sector , subframe _ index} ) modN _LE )

= PBRO ((i _LE + Offset _{sector , subframe _ index} ) modN _LE , N _LE )

y = PBRO (i, N _LE )

Here, the PBRO permutation value is generated by the following procedure.

1. First, select n value, which is a PBRO parameter, as shown in Equation 5 below.

N _LE ≤ 2n

2. Initialize i and j to 0.

3. Defining the value of x means the bit backwards value of j using n-bit binary notation. For example, if n is 4 and j is 3, then x is 12.

4.If x <N _LE , set PBRO ((i, N _LE ) to x and increase i by 1.

5. Otherwise, increase j by one.

6. If i <M, go to step 3.

In the above manner, if i _LE th LE is relocated to k _{interleavedLE} th LE, and the index of relocated LE is O _{interleavedLE} , O _{interleavedLE} is a sequential index of interleaved LE having values of 0 and N _LE -1. .

The above interleaving method N _LE For example, when = 12, k _{interleavedLE} , (i _LE + Offset _{sector , subframe _ index} ) modN _LE and O _{interleavedLE} using the PBRO interleaving method are as follows when Offset _{sector and subframe _ index} = 2.

(i _LE + Offset _{sector , subframe _ index} ) modN _LE 2 3 4 5 6 7 8 9 10 11 0 One k _{interleavedLE} 4 2 10 6 One 9 5 3 11 7 0 8 O _{interleavedLE} 0 One 2 3 4 5 6 7 8 9 10 11

값은

를 가장 멀리 분산시킨 형태의 인덱스를 가지고 있다.As you can see in Table 1 above

The value is

It has an index of the farthest distributed form.

In the above description, a method of changing interleaving for each base station by applying an offset unique to each base station to the interleaving method based on the PBRO method has been described. However, it should be noted that various other methods may be used in addition to the above method.

The modulation symbols of the interleaved control channel are mapped to the REs allocated for transmission of the control channels (140). The mapping method may be different for each base station, may be different for each subframe, or may be different for each OFDM symbol. Alternatively, different methods may be applied for each base station, different for each subframe, and different for each OFDM symbol. The mapping will be described below in detail with reference to FIG. 2.

2 is a diagram illustrating a process of mapping a control channel element and a resource element of a physical downlink control channel according to the present invention, with reference to this will be described in detail the process of mapping the CE or LE and RE. As described above, a CE may be a resource allocation unit of a control channel, and one physical downlink control channel may occupy one or several CEs. In addition, LE is a unit constituting CE. When mapping CE to RE, LE is mapped one-to-one to RE. All LEs interleaved in FIG. 1 are mapped to REs in FIG. 2. RE means useful subcarriers other than those used for pilot or other purposes in the frequency / time resource domain. In FIG. 2, 210 denotes pilot subcarriers of each antenna, and 220 denotes one RE.

2 illustrates a 3GPP Long Term Evolution (LTE) system as an example, this is only an embodiment and the present invention is not limited to a specific system and can be applied to various systems. In FIG. 2, the OFDM system defines seven OFDM symbols as one slot and two slots as one subframe. In the frequency / time resource region, the pilot subcarriers transmitted to each antenna, such as 230, are configured with an RE that will map the LE. As shown in 240 to 260, there are a maximum of three OFDM symbols including REs to which LEs can be mapped, and the same or different LEs may be mapped to REs for each OFDM symbol.

라고 하고 인터리빙된 LE의 인덱스를 상기에서 사용한

를 사용하는 경우에, 만약 첫 번째 OFDM 심볼에 LE의 RE로의 매핑에 사용할 수 있는 RE의 개수를

이라 하고,

<=

이라고 하면, LE 중에서

가 0,… 까지 첫 번째 OFDM 심볼의 RE 에 임의의 방법에 따라 매핑된다. 두 번째 및 세 번째 OFDM심볼에서의 매핑도 마찬가지이며, 하기의 수학식6과 같이 각 심볼에 매핑되는 LE의 인덱스를 계산할 수 있다.Each RE included in each OFDM symbol is mapped in an arbitrary pattern only within the corresponding OFDM symbol. In particular, when not using all the REs in the last symbol, a randomly distributed form is used in the entire frequency band in an arbitrary manner. For example, the total number of interleaved LEs

Using the index of the interleaved LE

In the case of using, the number of REs available for mapping the LEs to the REs in the first OFDM symbol

This is called,

<=

Speaking of LE

0,… Up to the first OFDM symbol is mapped according to any method. The same applies to the mapping in the second and third OFDM symbols, and the index of the LE mapped to each symbol can be calculated as shown in Equation 6 below.

이면, LE중에서

가 0,…

-1까지 첫 번째 OFDM심볼의 사용 가능한 RE에 임의의 분산된 방법으로 매핑된다. On the other hand, if

If in LE

0,…

Up to -1 is mapped in any distributed way to the available REs of the first OFDM symbol.

The index of LEs mapped to all OFDM symbols can be expressed as in Equation 6 below.

The index of LE is mapped by the mapping of LE and RE and can use any mapping rule. In the present invention will be described using a PBRO.

When the index of LE to be used for mapping each OFDM symbol is obtained, the mapping from LE to RE may be sequentially performed as in Equation 7 in all cases of Equation 6.

Meanwhile, the mapping from LE to RE may be performed as in Equation 8 using the PBRO method already described in the interleaving method.

인 경우를 예로 들면,

은

=1,

=2,

=3 일 경우 다음과 같다.In the present invention in the mapping from LE to RE

For example,

silver

= 1,

= 2,

If = 3, then

0 One 2 3

2 One 3 0

One 3 0 2

3 0

Referring to Table 2, when the last OFDM symbol is mapped to only the 0th and 3rd REs in the frequency domain, when one of the OFDM symbols cannot be filled, the PBRO scheme can be used to maximize the dispersion.

3 is a diagram illustrating an apparatus for transmitting a physical downlink control channel according to the present invention. Referring to FIG. 3, each physical downlink control channel (hereinafter referred to as "PDCCH") is subjected to channel coding in the channel encoders 301 to 308, respectively. The signals that have undergone channel coding are concatenated in a predetermined manner in the concatenation unit 302. In the present invention, a method of concatenating a plurality of PDCCHs is not limited to a specific method. The concatenated PDCCH signals are interleaved differently for each base station and subframe in the interleaver 303. The base station and subframe information required in the interleaving process is acquired through the controller 304 utilizing information such as PilotPN, subframe index, OFDM symbol, and the like. The signals interleaved in the interleaver 303 are modulator 305. The CE-to-RE mapping unit 306 maps different CEs for each base station, subframe, and OFDM symbol generated by the controller 304 through the modulation. After the CE and RE mapping is performed, the pilot tone inserter 307 inserts a pilot tone corresponding to each antenna, and then, together with the PDSCH (Physical Downlink Shared Channel) applied through the PDSCH transmitter 309, performs an IFFT processor ( 310). The signal multiplexed by the IFFT processor 310 and transformed into the time domain is transmitted through the transmitter 312 after the Cyclic prefix is added in the Cyclic prefix 311.

4 is a diagram illustrating an apparatus for transmitting a physical downlink control channel according to the present invention. Referring to FIG. 4, in step 401, the base station configures the PDCCH of each terminal through predetermined scheduling. Here, the total number of PDCCHs depends on the scheduling result. CEs are configured using the PDCCHs generated in step 403. Here, one PDCCH may have one or several CEs. The concatenation is performed by the predetermined method in step 405 with respect to the CEs configured in step 403. The above predetermined method is not limited to the specific method in the present invention can be carried out in various ways. Thereafter, in step 407, the concatenated CEs are interleaved differently for each base station and subframe. In step 411, the concatenated CEs are mapped from CE to RE for each base station, subframe, and each OFDM symbol.

5 is a diagram illustrating an apparatus for receiving a physical downlink control channel according to the present invention. Referring to FIG. 5, a signal received from an antenna is inputted to a downconverter and an analog / digital converter 501, converted from a high frequency to a baseband, and then converted into a digital signal through an analog to digital (A / D) conversion. Is converted. The digital signal is applied to the CP remover 502, and after the CP is removed, is converted into the frequency domain by the FFT processor 503. PDSCH-related subcarriers, which have undergone demultiplexing among respective subcarriers transformed into the frequency domain by the FFT processor 503, receive general OFDM data by the PDSCH receiver 513. Meanwhile, a pilot of each antenna is extracted through a pilot tone extractor 505 in the RE region to which CEs are mapped in the demultiplexed signal by the FFT processor 503, and the extracted pilot tone is a channel by the channel estimator 507. Used to make an estimate. The information generated from the PilotPN, the subframe index, and the OFDM symbol except for the pilot tone is used when the RE-to-CE mapping unit 506 maps the RE to the CE under the control of the controller 514. The CEs extracted by the RE-to-CE mapping unit 506 are demodulated by the demodulator 508 using the channel estimation information obtained by the channel estimator 507. The demodulated signal in the demodulator 508 is deinterleaved in a pattern generated in the controller 514 using the PilotPN, subframe index, and OFDM symbol information. All of the deinterleaved CEs are divided into respective PDCCH information through the divider 510, and each PDCCH information is demodulated into PDCCH information through the channel demodulators 511 to 512.

6 is a diagram illustrating a method for receiving a physical downlink control channel according to the present invention. Referring to FIG. 6, in operation 601, the received signal performs mapping from different CEs to REs for each base station, subframe, and each OFDM. The mapped CEs are deinterleaved per base station and subframe in step 603. The deinterleaved signals divide respective CEs in step 605 and form a PDCCH from each CE in step 607. Since one PDCCH may be composed of several CEs, in step 607, it is necessary to know in advance how many CEs each PDCCH is composed of.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the appended claims, but also by the equivalents of the claims.

As described above, the present invention maximizes interference diversity between base stations by interleaving control channels for each base station and subframe in downlink, and mapping CE or LE to RE for each base station, subframe, and OFDM symbol. It is effective to provide an efficient system.

Claims (12)

In the method of mapping resources to a plurality of control channels in the downlink of the wireless communication system, Channel coding the plurality of control channels; Allocating one or more control channel elements to each of the channel coded control channels; Concatenating the assigned control channel elements; Interleaving the contiguous control channel elements; And And mapping the interleaved control channel elements to resource elements. The method of claim 1, wherein the mapping of the interleaved control channel elements to the resource elements comprises: Configuring each of the interleaved control channel elements with one or more local elements; Obtaining a control channel element index of local elements constituting each of the control channel elements, interleaving the local elements; And mapping the interleaved local elements to resource elements according to base station, subframe, and OFDM according to each control channel element index. The method of claim 1, wherein the interleaving of the control channel elements comprises: A method for resource mapping of a physical downlink control channel in a wireless communication system, characterized in that a plurality of control channel elements are interleaved as a whole for each base station and subframe. The method of claim 1, wherein the mapping of the control channel elements to the resource elements comprises: A resource mapping method of a physical downlink control channel in a wireless communication system, characterized by mapping using all resource elements of an OFDM symbol The method of claim 2, wherein the mapping of the local elements to the resource elements comprises: When all resource elements of an OFDM symbol are used, the interleaved local elements are sequentially mapped to the resource elements. The method of claim 2, wherein mapping the local elements to the resource elements comprises: When all resource elements of an OFDM symbol are not used, interleaved local elements are sequentially mapped to resource elements. The method of claim 2, wherein the mapping of the control channel elements to the resource elements comprises: When all resource elements of an OFDM symbol are not used, the interleaved local elements are sequentially mapped to resource elements for each base station and for each subframe index. An apparatus for transmitting resources by mapping resources to a plurality of control channels of a wireless communication system, A channel encoder for channel coding the plurality of control channels; A concatenation unit for assigning one or more control channel elements to each of the channel coded control channels and concatenating the assigned control channel elements; An interleaver for interleaving the contiguous control channel elements; And And a control channel element-resource element mapping unit for mapping the interleaved control channel elements to resource elements. The method of claim 8, Control unit for generating the base station, sub-frame, OFDM information from the PilotPN, sub-frame index, OFDM symbols to provide to the interleaver and the control channel element-resource element mapping unit mapped physical downlink of the wireless communication system further comprising Control channel transmitter. The method of claim 8, A pilot tone inserter for inserting a pilot tone corresponding to each antenna into a signal output from the control channel element-resource element mapping unit; An IFFT processor for multiplexing the pilot signal-inserted mapping signal and a physical downlink common channel and converting the pilot signal into a time domain; And And a transmitter for transmitting the multiplexed and time-domain-converted signal. An apparatus for receiving a control channel to which resources of a wireless communication system are mapped, An analog / digital converter for digitally converting the signal received from the antenna; An FFT processor converting the digital signal into a frequency domain; A pilot tone extractor for extracting, as each antenna pilot, a resource element region to which control channel elements are mapped among de-multiplexed signals among the subcarriers transformed into the frequency domain; A channel estimator for estimating a channel using the extracted pilot tones; A resource element-control channel element mapping unit for mapping the resource element to the control channel element; A demodulator for decoding the control channel elements extracted by the resource element-control channel element mapping unit by using channel estimation information obtained by the channel estimator; A deinterleaver for deinterleaving the demodulated signal in the demodulator; A divider for dividing all of the deinterleaved control channel elements into respective physical downlink control channel information; And And a plurality of channel demodulators for demodulating the divided pieces of physical downlink control channel information into physical downlink control channel information. The method of claim 11, Control unit for generating the base station, sub-frame, OFDM-specific information from the PilotPN, sub-frame index, OFDM symbols to provide to the resource element-control channel element mapping unit and the deinterleaver; Downlink control channel receiver.

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