JP5404451B2 - Mobile station and control information decoding method - Google Patents

Description

  The present invention relates to a mobile station and a control information decoding method, and more particularly to a mobile station and a control information decoding method for detecting control information addressed to the own station included in a downlink control channel from a base station.

  In recent years, studies on LTE (Long Term Evolution) have been promoted in 3GPP, which is a standardization body for mobile communication systems. In order to transmit user data to a mobile station under the LTE base station, an LTE base station schedules which user data channel is allocated to which mobile station. And a base station notifies a scheduling result (control information) to each mobile station using PDCCH (Physical Downlink Control Channel) which is a downlink control channel (for example, refer nonpatent literatures 1-3).

  Control information from the base station is transmitted to each mobile station in units of CCE (Control Channel Element) included in the PDCCH. FIG. 3 is a diagram illustrating an example of assignment of control information to the CCE. The number of CCEs used for the control information to each mobile station is called an aggregation level (hereinafter referred to as “AL”). The base station sets an AL to be assigned to each mobile station in consideration of the number of mobile stations under its control and the radio communication quality of each mobile station. AL is set to any one of 1, 2, 4, or 8. When the AL is 2 or more, the base station assigns control information to continuous AL (for example, 2) CCEs. In the case of FIG. 3, the base station sets AL for mobile station A to 1 and assigns the second CCE for control information to mobile station A. In addition, the base station sets AL for mobile station B to 2, and allocates two consecutive CCEs of 12th and 13th for control information to mobile station B. In addition, when the data length of the control information to each mobile station is shorter than the assigned CCE, the base station repeatedly sets Coding Output including the same control information within the assigned CCE range as shown in FIG. A process called Rate Matching is performed.

  The base station transmits the control information to the mobile station with a CRC encoded with a unique ID (RNTI: Radio Network Temporary Identifier) of the corresponding mobile station. When receiving the PDCCH including the CCE from the base station, the mobile station performs CRC check by decoding the CRC of the signal included in each CCE with the unique ID of the mobile station (CRC decoding). When the CRC check passes, the mobile station can determine that the signal is control information addressed to itself.

  Note that it is not efficient for the mobile station to perform a CRC check on all CCEs included in the PDCCH. Therefore, as shown in FIG. Is set in advance. This allocation candidate position can be calculated using the unique ID of the terminal and the AL. For example, mobile station A can find control information (AL = 1) addressed to itself if it performs a CRC check on the 1st to 5th CCEs which are allocation candidate positions when AL is 1. . Further, if the mobile station B performs a CRC check on the 10th to 13th CCEs, which are allocation candidate positions when AL is 2, the mobile station B can find control information (AL = 2) addressed to itself. .

  In this way, the mobile station does not know the position of the control information addressed to itself transmitted from the base station, and performs CRC decoding on the signal included in the CCE belonging to the allocation candidate position until the control information is detected. This is called blind decoding. The mobile station decodes CRCs in an appropriate order for the CCEs included in the corresponding allocation candidate positions. When the mobile station finds control information addressed to itself by blind decoding, the mobile station can acquire user data addressed to itself and perform uplink data transmission using the control information.

3GPP TS36.211 (V8.7.0), "Physical Channels and Modulation", May 2009 3GPP TS36.212 (V8.7.0), “Evolved Universal Terrestrial Radio Access (E-UTRA) Multiplexing and channel coding”, May 2009 3GPP TS36.213 (V8.7.0), "Evolved Universal Terrestrial Radio Access (E-UTRA) Physical layer procedures", May 2009

  As described above, in the current blind decoding, the mobile station performs CRC decoding of signals included in the CCEs belonging to the allocation candidate position of the local station in an appropriate order, and therefore it is unlikely that control information is included. There was a problem in terms of processing efficiency, such as performing CRC decoding on CCE.

  Therefore, an object of the present invention made in view of such a point is to provide a mobile station capable of efficiently detecting control information addressed to itself by setting a priority of CRC decoding to CCEs belonging to allocation candidate positions. There is to do.

In order to solve the above-described problems, the mobile station according to the first aspect is
A mobile station that decodes a signal of a control channel element belonging to an allocation candidate position of the control information in order to detect control information from a base station to the own station included in a downlink control channel having a plurality of control channel elements. ,
A generator for generating a reception level of each control channel element belonging to the allocation candidate position;
A control unit configured to set a priority according to the reception level for each control channel element, and to control decoding of the signals of the control channel elements in an order according to the priority.

The invention according to the second aspect is the mobile station according to the first aspect,
When detecting control information included in N (N> 1) consecutive control channel elements, a change in reception level of N consecutive control channel elements belonging to the control information allocation candidate position is equal to or greater than a threshold value. If the fluctuation of the reception level is greater than or equal to a threshold value, the priority of the N consecutive control channel elements is set low.

The invention according to the third aspect is the mobile station according to the first or second aspect,
The generation unit generates an average value of soft values of signals included in the control channel elements as the reception level,
The said control part sets the said priority according to the average value of the said soft value.

The invention according to a fourth aspect is the mobile station according to any one of the first to third aspects,
When detecting control information included in N (N> 1) consecutive control channel elements, is the reception level of some control channel elements of the N consecutive control channel elements equal to or greater than a threshold value? If the reception level of the part of the control channel elements is equal to or higher than a threshold value, the decoding unit is controlled to decode only the part of the control channel elements.

  As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent thereto, and the scope of the present invention. It should be understood that these are also included.

For example, a decoding method of control information according to a fifth aspect that realizes the present invention as a method includes:
Control information decoding method for decoding a signal of a control channel element belonging to an allocation candidate position of the control information in order to detect control information from a base station to the own station included in a downlink control channel having a plurality of control channel elements Because
Generating a reception level of each control channel element belonging to the allocation candidate position;
Setting a priority according to the reception level for each control channel element, and controlling decoding of signals of the control channel elements in an order according to the priority.

  According to the present invention, it is possible to efficiently detect control information addressed to the own station by setting a priority of CRC decoding to control channel elements (CCEs) belonging to allocation candidate positions.

FIG. 1 is a functional block diagram of a mobile station according to an embodiment of the present invention. FIG. 2 is a process flowchart of the control unit of the mobile station shown in FIG. FIG. 3 is a diagram illustrating an example of assignment of control information to the CCE. FIG. 4 is a diagram illustrating an example of repetition of control information within the CCE.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a mobile station 1 according to an embodiment of the present invention. The mobile station 1 includes an antenna ANT, a generation unit 10, a control unit 20, and a decoding unit 30. The generation unit 10 is configured by an interface device / circuit suitable for the LTE system, and the control unit 20 and the decoding unit 30 are configured by a suitable processor such as a CPU. Details of each part will be described below.

  Upon receiving a PDCCH (downlink control channel) signal from the base station through the antenna ANT, the generation unit 10 performs resource element mapping and demodulation processing on the received signal, and performs each CCE (control channel element) belonging to the allocation candidate position. ) Bit string (soft value string: reception level). The soft value referred to here represents each bit value of CCE by a value representing “1” and “0” instead of 1 or 0, and is also called likelihood. . For example, the range of soft values can be expressed as -10 to 10, and “0” bits can be expressed as soft values closer to −10, and “1” bits can be expressed as soft values closer to 10.

  The control unit 20 sets priorities corresponding to the soft value sequences generated by the generation unit 10 for the CCEs belonging to the allocation candidate positions of the control information, and the CCEs by the decoding unit 30 in the order corresponding to the priorities. The CRC decoding of the signal is controlled. FIG. 2 is a process flowchart of the control unit 20.

  The control unit 20 calculates the soft value average (or the average of the absolute values of the soft values) of each CCE belonging to the control information allocation candidate position (step S101). For example, as described above, when the soft value range is −10 to 10 and the “0-like” bit is a soft value closer to −10, and the “1-like” bit is represented by a soft value closer to 10, The higher the average of the absolute values, the more easily the CCE contains a signal that can be identified as 0 or 1. That is, a CCE having a higher soft value average is more likely to include control information addressed to the own station or another station. Therefore, the control unit 20 can first determine whether or not control information is included in each CCE by calculating the soft value average of each CCE.

  When detecting control information of AL = 1 (No in Step S102), the control unit 20 sets priorities of CCEs belonging to allocation candidate positions in descending order of the soft value average (Step S103). As described above, since a CCE having a high soft value average includes many signals that can be easily identified as 0 or 1, the higher the soft value average, the higher the reliability of the signal and the possibility of decoding as a control signal. This is because it is expensive.

  When detecting control information of AL ≧ 2 (for example, AL = 2, 4 or 8) (Yes in step S102), the control unit 20 has a variation in the soft value average of each CCE for continuous AL CCEs. Is determined (step S104). For example, as shown in FIG. 3, AL = 2 information for a certain mobile station (B) is assigned to consecutive CCEs (12, 13). Further, as shown in FIG. 4, Coding Output including control information is repeatedly set in consecutive CCEs. For this reason, when control information of two or more ALs is allocated, the average soft value of each continuous AL CCE is a close value, and there is a low possibility that a large fluctuation will occur. That is, when there is a large variation in the average soft value of each AL continuous CCE, it is considered that each CCE is unlikely to contain control information having an AL of 2 or more. Therefore, when the average soft value variation of each CCE is greater than or equal to the threshold for the continuous AL CCEs, the control unit 20 sets the priority of the continuous AL CCEs to be low (step S105). On the other hand, when the variation of the average soft value of each CCE is less than the threshold value, the control unit 20 presumes that there is a high possibility that the control information having AL of 2 or more is included, and prioritizes the continuous AL CCE The degree is set high (step S106).

  In accordance with the priority set by the control unit 20, the decoding unit 30 decodes the CRC of the signal included in each CCE using its own unique ID, and performs a CRC check. When the CRC check passes, the mobile station can determine that the signal is control information addressed to itself.

  As described above, according to the present embodiment, when the generation unit 10 generates the CCE soft value sequence belonging to the control information allocation candidate position, the control unit 20 performs decoding according to the average soft value of the soft value sequence. The priority is set, and the decoding unit 30 performs CRC decoding of each CCE in the order according to the priority. For this reason, the mobile station according to the present embodiment can perform CRC decoding in order from the CCE most likely to contain control information, and can efficiently detect control information addressed to itself. Become. Further, by quickly detecting the control information, subsequent processing such as user data reception using the control information and uplink data transmission can be quickly performed.

  In addition, when detecting control information included in N (N> 1) continuous CCEs with AL of 2 or more, the control unit 20 determines N consecutive CCEs belonging to the allocation candidate positions. It is determined whether or not the variation in the reception level is equal to or greater than the threshold value. If the variation in the reception level is equal to or greater than the threshold value, the priority of the N consecutive CCEs is set low. Therefore, CRC decoding of CCE that is unlikely to contain control information with AL of 2 or more is postponed, and CRC decoding is performed from CCE that is likely to contain control information with AL of 2 or more. Therefore, it becomes possible to efficiently detect the control information addressed to the own station.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and multiple components, steps, etc. can be combined or divided into one It is.

  For example, in the above-described embodiment, the reception level generated by the generation unit for each control channel element has been described as a soft value. However, the reception level according to the present invention is not limited to a soft value, and reception strength and SINR ( Note that various information can be used, such as signal to noise interference ratio.

  For example, when AL is 2 or more and control information included in two or more continuous CCEs is detected, the control unit 20 receives the reception level (reception strength, soft value) of a part of the continuous CCEs. If the reception level is equal to or higher than the threshold, it is possible to control to perform CRC decoding only on the partial CCE. As described above, it is possible to determine the possibility that the control information is included according to the reception level of the CCE, and when the reception level is sufficiently high, there is a possibility that the signal is highly reliable and can be decoded as the control signal. This is because it is expensive. That is, by performing CRC decoding only on CCEs that are likely to contain control information, unnecessary repetitive processing can be prevented and control information addressed to the own station can be detected efficiently.

DESCRIPTION OF SYMBOLS 1 Mobile station 10 Generation part 20 Control part 30 Decoding part

Claims (5)

A mobile station that decodes a signal of a control channel element belonging to an allocation candidate position of the control information in order to detect control information from a base station to the own station included in a downlink control channel having a plurality of control channel elements. ,
A generator for generating a reception level of each control channel element belonging to the allocation candidate position;
A control unit configured to set a priority according to the reception level for each control channel element and to control decoding of signals of the control channel elements in an order according to the priority.   When the control unit detects control information included in N (N> 1) consecutive control channel elements, the reception level of N consecutive control channel elements belonging to the control information allocation candidate position The priority of the N consecutive control channel elements is set to be low when the fluctuation of the reception level is equal to or greater than the threshold. The listed mobile station. The generation unit generates an average value of soft values of signals included in the control channel elements as the reception level,
The control unit sets the priority according to an average value of the soft values;
The mobile station according to claim 1 or 2.   When the control unit detects control information included in N (N> 1) consecutive control channel elements, reception levels of some control channel elements of the N consecutive control channel elements are It is determined whether or not the threshold level is equal to or higher than a threshold value, and when the reception level of the partial control channel element is equal to or higher than the threshold value, the decoding unit is controlled to decode only the partial control channel element. The mobile station according to any one of claims 1 to 3. Control information decoding method for decoding a signal of a control channel element belonging to an allocation candidate position of the control information in order to detect control information from a base station to the own station included in a downlink control channel having a plurality of control channel elements Because
Generating a reception level of each control channel element belonging to the allocation candidate position;
A control information decoding method comprising: setting a priority according to the reception level for each control channel element, and controlling decoding of signals of the control channel elements in an order according to the priority. .

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