WO2016017038A1 - Communication system, base station and communication terminal - Google Patents

Abstract

Provided is a communication terminal that can suppress an increase in power consumption when D2D communications are performed. A communication terminal (20) is able to perform cellular communications with a base station that transmits an EPDCCH signal that includes a DCI indicating wireless resource allocation results and DMRS associated with the EPDCCH signal, and is also able to perform D2D communications with other communication terminals without going through the base station. The communication terminal (20) has a wireless receiver (231) and a blind detection unit (237). The wireless receiver (231) receives DMRS from the base station. The blind detection unit (237) performs DCI blind detection in a first search range for cellular communications when the received DMRS is determined to be a first code sequence generated using a first initial value. Meanwhile, the blind detection unit (237) performs DCI blind detection in a second search range for D2D communications when the received DMRS is determined to be a second code sequence generated using a second initial value obtained by adding an offset value to the first initial value.

Description

Communication system, base station and communication terminal

The present invention relates to a communication system, a base station, and a communication terminal.

Recently, in order to further increase the speed and capacity of a wireless communication in a wireless communication system such as a cellular system which is one of mobile phone systems, the next generation wireless communication technology is being studied. For example, 3GPP (3rd Generation Partnership Project), a standardization organization, will continue to formulate a communication standard called “LTE (Long Term Evolution)”, and will further improve performance based on LTE wireless communication technology. A communication standard called “LTE-A (LTE-Advanced)” has been studied.

There is a possibility that it will be introduced to LTE-A in the future, and one of the communication technologies that is currently being studied in 3GPP is a communication technology called “D2D (Device to Device) communication”. There is direct communication. In conventional cellular communication, communication terminals that are close to each other communicate with each other via a base station, whereas in D2D communication, communication terminals that are close to each other directly communicate with each other without using a base station. By enabling D2D communication, for example, even when a function of a base station stops and communication via the base station cannot be performed at the time of a disaster or the like, communication between communication terminals can be performed.

In the study on D2D communication, it is considered to perform D2D communication by sharing uplink radio resources of cellular communication with cellular communication. That is, performing D2D communication using the present uplink radio frequency band of cellular communication is being studied. In addition, introduction of a communication terminal capable of performing both cellular communication and D2D communication is also under consideration. Therefore, when performing D2D communication using the uplink radio frequency band of cellular communication, the base station allocates uplink radio resources for cellular communication to one communication terminal in the same radio frequency band. And allocation of radio resources for D2D communication.

Here, the layer 1 control information transmitted from the base station to the communication terminal in the current LTE is called “DCI (Downlink Control Information)”, and the DCI depends on the purpose of use, that is, the content of the control information. Format 0, 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 2D, 3, 3A, 4 is adopted. For example, the format of DCI for notifying the communication terminal of a radio resource allocation result used for the communication terminal to transmit a signal to the base station from the base station is format 0 or 4.

Also, DCI is transmitted from the base station to the communication terminal using “EPDCCH (Enhanced Physical Control Channel)” which is one of the radio physical channels. Each EPDCCH is mapped to a radio resource area composed of one or a plurality of continuous CCEs (Control Channel Elements). Each EPDCCH adopts one of formats 0 to 3 depending on its size. The format 0 EPDCCH takes a size of “N” corresponding to “1CCE”, and the format 1 EPDCCH takes a size of “2N” corresponding to “2CCE”. Also, the EPDCCH of format 2 takes a size of “4N” corresponding to “4CCE”, and the EPDCCH of format 3 takes a size of “8N” corresponding to “8CCE”. In other words, the sizes N, 2N, 4N, and 8N of the EPDCCH correspond to the number of connected CCEs 1, 2, 4, and 8, respectively, and the number of connected CCEs is referred to as an “aggregation level”.

DCI is encoded at a coding rate according to the downlink channel quality, and the DCI is encoded at a lower coding rate as the downlink channel quality decreases. Therefore, the size of the DCI after encoding becomes larger as the downlink channel quality decreases. On the other hand, when the encoded DCI is transmitted using the EPDCCH, the size of the encoded DCI is matched by rate matching so that it matches any of the four sizes N to 8N of the EPDCCH. Adjusted. That is, as the downlink channel quality deteriorates, a larger EPDCCH is used for DCI transmission, and the aggregation level is one of 1, 2, 4, and 8 depending on the size of the DCI after encoding. Selected from. The CCE modulation scheme is constant in QPSK (Quadrature Phase Shift Keying) regardless of the downlink channel quality.

Also, the radio resource area to which the EPDCCH for each communication terminal is mapped is called “Search Space”, and the search space is determined for each aggregation level as shown in FIG. FIG. 1 is a diagram for explaining a conventional search space. In FIG. 1, “SS” indicates a search space, and “AL” indicates an aggregation level. In the current LTE, as shown in FIG. 1, six search spaces SS0 to SS5 are defined for cellular communication according to the aggregation level. Of the search spaces SS0 to SS5, four search spaces SS0 to SS3 are search spaces specific to each communication terminal, and two search spaces SS4 and SS5 are search spaces common to all communication terminals. .

In FIG. 1, SS = 0 with AL = 1 is composed of six search units that can map EPDCCH of format 0, and each search unit corresponds to 1 CCE. SS = 2 with AL = 2 is composed of six search units to which EPDCCH of format 1 can be mapped, and each search unit corresponds to 2CCE. The SS2 of AL = 4 is composed of two search units that can map the EPDCCH of the format 2, and each search unit corresponds to 4CCE. The SS3 with AL = 8 is composed of two search units that can map the EPDCCH of the format 3, and each search unit corresponds to 8 CCEs. SS = 4 with AL = 4 is composed of four search units that can map the EPDCCH of format 2, and each search unit corresponds to 4CCE. The SS5 with AL = 8 is composed of two search units that can map the EPDCCH of the format 3, and each search unit corresponds to 8 CCEs.

The DCI before encoding includes a 16-bit CRC (Cyclic Redundancy Check) bit masked with a 16-bit bit string indicating the ID of the communication terminal in order to identify the communication terminal of the DCI transmission destination. Added. Each communication terminal performs CRC by demasking the CRC bit portion of the decoded bit string with the ID of the own terminal, and detects DCI addressed to the own terminal. That is, each communication terminal determines that the received DCI is the DCI addressed to itself when the CRC by demasking with the ID of the terminal is successful.

Here, one subframe includes SS4 and SS5 common to all communication terminals and SS0 to SS3 unique to each communication terminal. Then, the communication terminal performs DCI blind detection by CRC using its own ID for each search unit constituting each search space. That is, the search space corresponds to the DCI search range.

As shown in FIG. 1, the total number of all search units in SS0 to SS5 is 22. In addition, since the size of DCI before encoding differs depending on the format and there are two types of DCI, the communication terminal performs blind detection for each of the two types of DCI in each search unit. Do. Therefore, the maximum number of blind detections performed in one subframe is 22 times × 2 = 44 times per communication terminal.

3GPP TR36.913, “Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced)”, V9.0.0, Release 9, December 2009. 3GPP TR36.912, “Feasibility study for further advancements for E-UTRA (LTE-Advanced)”, V9.3.0, Release 9, June 2010. 3GPP TS36.321, “Medium Access Control (MAC) protocol specification”, V10.2.0, Release 10, June 2011. 3GPP TS36.133, “Requirements for support of radio resource management”, V10.3.0, Release 10, June 2011. 3GPP TS36.213, “Physical layer procedures”, V10.2.0, Release 10, June 2011. 3GPP TS36.300, “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)”, V10.4.0, Release 10, June 2011.

Here, in the current LTE, there is no DCI format for notifying the communication result of the allocation of radio resources for D2D communication from the base station to the communication terminal. Therefore, it is conceivable to introduce DCI having a new format for notifying the result of allocation of radio resources for D2D communication. However, introduction of DCI in a new format for D2D communication leads to an increase in the number of times of blind detection in the communication terminal.

FIG. 2 is a diagram for explaining the problem. In FIG. 2, “SS” indicates a search space, “AL” indicates an aggregation level, and the numbers in parentheses indicate the number of search units constituting each search space. As described with reference to FIG. 1, there are 22 search units for cellular communication per communication terminal. In addition, since there are two types of DCI in the past, the number of times of blind detection for cellular communication is 44 times at maximum in one subframe per communication terminal as described above.

On the other hand, for example, if SS6 to SS9 are prepared for DCI of a new format for D2D communication as shown in FIG. 2 following the conventional SS0 to SS3 prepared for each communication terminal, D2D The number of times of blind detection for communication is 6 + 6 + 2 + 2 = 16 at maximum in one subframe per communication terminal. Therefore, in a communication terminal capable of performing both cellular communication and D2D communication, a maximum of 44 times + 16 times = 60 times of blind detection is performed within one subframe. That is, the amount of processing required for blind detection is increased by about 36% compared to the prior art. Since an increase in the number of blind detections leads to an increase in power consumption of the communication terminal, it is preferable to reduce the number of blind detections as much as possible.

The disclosed technique has been made in view of the above, and aims to suppress an increase in power consumption of a communication terminal when performing D2D communication.

In an aspect of the disclosure, the communication system includes a base station, a first communication terminal, and a second communication terminal capable of communicating directly with the first communication terminal without going through the base station while communicating with the base station. And having. The base station is a base station that transmits a control channel signal including control information indicating a radio resource allocation result and a reference signal accompanying the control channel signal to the second communication terminal. Further, the base station uses the control channel signal to indicate a first allocation result of the first radio resource allocated to the first communication which is communication between the base station and the second communication terminal. When notifying the terminal, the first code sequence generated using the first initial value is used as the reference signal. On the other hand, the base station uses the control channel signal to calculate a second allocation result of the second radio resource allocated to the second communication which is a direct communication between the second communication terminal and the first communication terminal. When notifying to the second communication terminal, a second code sequence generated using a second initial value obtained by adding an offset value to the first initial value is used as the reference signal. On the other hand, the second communication terminal receives the reference signal from the base station. Further, when the second communication terminal determines that the received reference signal is the first code sequence, the second communication terminal detects the control information in the first search range for the first communication. On the other hand, when the second communication terminal determines that the received reference signal is the second code sequence, the second communication terminal detects the control information in the second search range for the second communication.

According to the disclosed aspect, it is possible to suppress an increase in power consumption of the communication terminal when performing D2D communication.

FIG. 1 is a diagram for explaining a conventional search space. FIG. 2 is a diagram for explaining the problem. FIG. 3 is a diagram illustrating an example of a configuration of the communication system according to the first embodiment. FIG. 4 is a functional block diagram illustrating an example of the configuration of the base station according to the first embodiment. FIG. 5 is a functional block diagram illustrating an example of the configuration of the communication terminal according to the first embodiment. FIG. 6 is a diagram illustrating an example of a processing sequence of the communication system according to the first embodiment. FIG. 7 is a diagram illustrating a hardware configuration example of the base station. FIG. 8 is a diagram illustrating a hardware configuration example of the communication terminal.

Hereinafter, embodiments of a communication system, a base station, and a communication terminal disclosed in the present application will be described in detail based on the drawings. Note that the communication system, base station, and communication terminal disclosed in the present application are not limited by this embodiment. Moreover, the same code | symbol is attached | subjected to the structure which has the same function in each Example, and the step which performs the same process, and the overlapping description is abbreviate | omitted.

[Example 1]
<Configuration of communication system>
FIG. 3 is a diagram illustrating an example of a configuration of the communication system according to the first embodiment. In FIG. 3, the communication system 1 includes a base station BS1 connected to a network (not shown), a communication terminal UE1, and a communication terminal UE2. The communication terminal UE1 can communicate with the base station BS1. Further, the communication terminal UE1 can directly communicate with the communication terminal UE2 without going through the base station BS1, that is, D2D communication with the communication terminal UE2. That is, the communication terminal UE1 is a communication terminal capable of performing both cellular communication and D2D communication. Base station BS1 forms cell C1. The communication terminal UE1 receives DCI from the base station BS1 when performing cellular communication and D2D communication.

<Base station configuration>
FIG. 4 is a functional block diagram illustrating an example of the configuration of the base station according to the first embodiment. The base station 10 shown in FIG. 4 corresponds to the base station BS1 shown in FIG. In FIG. 4, the base station 10 includes a PDSCH (Physical Downlink Shared Channel) signal generation unit 115, a DCI formation unit 11, and EPDCCH signal generation units 102 and 105. In addition, the base station 10 includes a mapping unit 103, a DMRS (Demodulation Reference Signal) generation unit 106, and a notification signal generation unit 107. In addition, the base station 10 includes a radio transmission unit 108, a duplexer 109, an antenna 110, a radio reception unit 111, and a UL (UpLink) data acquisition unit 112. The DCI forming unit 11 includes a D2D communication DCI forming unit 101 and a cellular communication DCI forming unit 104.

PDSCH signal generation section 115 performs coding processing and modulation processing on user data addressed to communication terminal UE1, that is, DL (DownLink) data, generates a PDSCH signal, and outputs the generated PDSCH signal to mapping section 103 .

The D2D communication DCI forming unit 101 may be referred to as an allocation result of radio resources allocated to D2D communication between the communication terminal UE1 and the communication terminal UE2 (hereinafter referred to as “D2D communication RA (Resource Allocation) result”). ) Is entered. When the D2D communication RA result is input, the D2D communication DCI forming unit 101 forms a D2D communication DCI indicating the D2D communication RA result according to a specific format, and generates the formed D2D communication DCI as an EPDCCH signal. Output to the unit 102.

The cellular communication DCI forming unit 104 receives an assignment result of radio resources assigned to the cellular communication between the base station 10 and the communication terminal UE1 (hereinafter may be referred to as “cellular communication RA result”). The When the cellular communication RA result is inputted, the cellular communication DCI forming unit 104 forms the cellular communication DCI indicating the cellular communication RA result according to a specific format, and generates the formed cellular communication DCI as an EPDCCH signal. To the unit 105.

Also, the DCI forming unit 11 outputs an identification signal indicating whether the formed DCI is D2D communication DCI or cellular communication DCI to the DMRS generation unit 106.

Here, the DCI for D2D communication formed by the DCI forming unit 101 for D2D communication and the DCI for cellular communication formed by the DCI forming unit 104 for cellular communication adopt the same specific format. For example, both D2D communication DCI and cellular communication DCI adopt format 0.

The EPDCCH signal generation unit 102 performs encoding processing and modulation processing on the DCI for D2D communication to generate an EPDCCH signal for D2D communication, and outputs the generated EPDCCH signal to the mapping unit 103. That is, the EPDCCH signal output from the EPDCCH signal generation unit 102 includes DCI for D2D communication.

The EPDCCH signal generation unit 105 performs coding processing and modulation processing on the DCI for cellular communication to generate an EPDCCH signal for cellular communication, and outputs the generated EPDCCH signal to the mapping unit 103. That is, the EPDCCH signal output from the EPDCCH signal generation unit 105 includes DCI for cellular communication.

Here, for DCI addressed to communication terminal UE1, EPDCCH signal generation sections 102 and 105 encode the DCI after adding a CRC bit masked with a bit string indicating the ID of communication terminal UE1 to DCI. Also, EPDCCH signal generation sections 102 and 105 encode DCI at a lower coding rate as the downlink channel quality to communication terminal UE1 decreases. EPDCCH signal generation sections 102 and 105 perform the same encoding process on DCI addressed to communication terminals other than communication terminal UE1.

The DMRS generating unit 106 generates a DMRS according to the identification signal input from the DCI forming unit 11. That is, when the DCI formed by the DCI forming unit 11 is the DCI for D2D communication, the DMRS generating unit 106 generates a DMRS for D2D communication (hereinafter may be referred to as “D2D communication DMRS”). . On the other hand, when the DCI formed by the DCI forming unit 11 is a DCI for cellular communication, the DMRS generating unit 106 generates a DMRS for cellular communication (hereinafter may be referred to as “DMRS for cellular communication”). To do. The DMRS generation unit 106 outputs the generated DMRS to the mapping unit 103.

Here, DMRS is a reference signal for demodulating an EPDCCH signal including DCI, and is a reference signal accompanying the EPDCCH signal. The DMRS is generated according to a predetermined calculation formula using the scramble value and the offset value. Details of DMRS generation by the DMRS generation unit 106 will be described later.

The notification signal generation unit 107 generates a notification signal indicating a scramble value and an offset value, and outputs the generated notification signal to the mapping unit 103.

The mapping unit 103 maps the EPDCCH signal for D2D communication to the search unit of any one of the search spaces SS6 to SS9 shown in FIG. Further, mapping section 103 maps an EPDCCH signal for cellular communication to the search unit of any one of search spaces SS0 to SS5 shown in FIG.

Also, the mapping unit 103 maps the DRS for DM2D communication to the same subframe as the subframe to which the EPDCCH signal for D2D communication is mapped, and outputs it to the radio transmission unit 108. Further, mapping section 103 maps cellular communication DMRS to the same subframe as the subframe to which the cellular communication EPDCCH signal is mapped, and outputs the result to radio transmission section 108. Further, mapping section 103 maps the PDSCH signal to the same subframe as the subframe to which the EPDCCH signal for cellular communication is mapped, and outputs it to radio transmission section 108. Here, each subframe is formed of two slots, a first slot and a second slot. Therefore, the mapping unit 103 maps the EP2CH communication signal for D2D communication and the DMRS for D2D communication to the same slot, and maps the EPDCCH signal for cellular communication and the DMRS for cellular communication to the same slot.

Also, the mapping unit 103 maps the notification signal generated by the notification signal generation unit 107 to a predetermined subframe, and outputs it to the wireless transmission unit 108. For example, the predetermined subframe to which the notification signal is mapped is the first subframe at the start of communication between the base station 10 and the communication terminal UE1.

The wireless transmission unit 108 performs digital-analog conversion, up-conversion, and the like on the PDSCH signal, EPDCCH signal, DMRS signal, and notification signal to obtain a wireless signal, and communicates the wireless signal via the duplexer 109 and the antenna 110. It transmits to terminal UE1. Through the transmission of this radio signal, the DCI for D2D communication and the DCI for cellular communication are notified to the communication terminal UE1. In addition, the scramble value and the offset value are notified to the communication terminal UE1 by the transmission of the radio signal.

On the other hand, the radio reception unit 111 obtains a baseband signal by performing down-conversion, analog-digital conversion, and the like on the radio signal received from the communication terminal UE1 via the antenna 110 and the duplexer 109, and obtains a UL data acquisition unit 112. Output to.

The UL data acquisition unit 112 extracts a UL signal from a baseband signal according to a mapping result at the communication terminal UE1 for an uplink (UpLink: UL) signal, performs demodulation processing and decoding processing on the extracted UL signal, and performs UL processing. Get the data. Since the mapping at the communication terminal UE1 for the UL signal is performed according to the DCI for cellular communication, the UL data acquisition unit 112 can know the mapping result of the UL signal from the RA result for cellular communication input to the DCI forming unit 11. it can.

<Configuration of communication terminal>
FIG. 5 is a functional block diagram illustrating an example of the configuration of the communication terminal according to the first embodiment. The communication terminal 20 illustrated in FIG. 5 corresponds to the communication terminal UE1 illustrated in FIG. In FIG. 5, the communication terminal 20 includes a reception antenna 201, a separator 202, radio reception units 203 and 231, demodulation units 204, 233 and 238, and decoding units 205, 236 and 239. Further, the communication terminal 20 includes a demapping unit 232, a channel estimation unit 234, a DMRS determination unit 235, a blind detection unit 237, and a communication control unit 21. The communication control unit 21 includes a D2D communication control unit 212 and a cellular communication control unit 213. In addition, the communication terminal 20 includes a D2D communication unit 22, a cellular communication unit 23, a wireless transmission unit 225, and a transmission antenna 226. The D2D communication unit 22 includes a D2D signal forming unit 215, an encoding unit 216, a modulation unit 217, and a mapping unit 218. The cellular communication unit 23 includes a UL signal forming unit 221, an encoding unit 222, a modulation unit 223, and a mapping unit 224.

The separator 202 separates the radio signal received via the reception antenna 201 into a radio signal from the communication terminal UE2 and a radio signal from the base station BS1, and transmits the radio signal from the communication terminal UE2 to the radio reception unit. 203, and a radio signal from the base station BS1 is output to the radio receiver 231.

The radio reception unit 203 performs down-conversion, analog-digital conversion, etc. on the radio signal from the communication terminal UE2, obtains a baseband signal, and outputs it to the demodulation unit 204.

Demodulation section 204 performs demodulation processing on the baseband signal input from wireless reception section 203 and outputs the demodulated signal to decoding section 205.

The decoding unit 205 performs a decoding process on the signal input from the demodulation unit 204. By the decoding process in the decoding unit 205, D2D data transmitted from the communication terminal UE2, that is, data of D2D communication is obtained.

The radio reception unit 231 performs down-conversion, analog-digital conversion, etc. on the radio signal from the base station BS1 to obtain a baseband signal and outputs it to the demapping unit 232.

The demapping unit 232 performs mapping at the base station BS1, that is, demapping corresponding to the mapping at the mapping unit 103 (FIG. 4), on the baseband signal, from the baseband signal to the PDSCH signal, EPDCCH signal, DMRS and notification signal are extracted. The demapping unit 232 outputs the PDSCH signal to the demodulation unit 238, outputs the EPDCCH signal to the demodulation unit 233, outputs the DMRS to the channel estimation unit 234 and the communication type determination unit 235, and transmits the notification signal to the communication type determination unit 235. Output to.

The channel estimation unit 234 performs downlink channel estimation using DMRS to calculate a channel estimation value, and outputs the calculated channel estimation value to the demodulation unit 238 and the demodulation unit 233.

Demodulation section 238 performs demodulation processing on the PDSCH signal input from demapping section 232 using the channel estimation value input from channel estimation section 234, and transmits the PDSCH signal after demodulation processing to decoding section 239. Output.

The decoding unit 239 performs a decoding process on the PDSCH signal input from the demodulation unit 238. Through the decoding process in the decoding unit 239, DL data that is user data transmitted from the base station BS1 is obtained.

Demodulation section 233 performs demodulation processing on the EPDCCH signal input from demapping section 232 using the channel estimation value input from channel estimation section 234, and transmits the demodulated EPDCCH signal to decoding section 236. Output.

The decoding unit 236 performs a decoding process on the EPDCCH signal input from the demodulation unit 233. By the decoding process in the decoding unit 236, a plurality of DCIs transmitted from the base station BS1 are obtained. The plurality of DCIs include those addressed to the communication terminal 20 and those addressed to other communication terminals other than the communication terminal 20. Each DCI is added with a CRC bit masked with a bit string indicating the ID of each communication terminal. The decoding unit 236 outputs the decoded bit string, that is, the DCI to which the CRC bits are added, to the blind detection unit 237.

The DMRS determination unit 235 determines whether the DMRS input from the demapping unit 232, that is, the DMRS received by the communication terminal 20, is the DMRS for cellular communication or the DMRS for D2D communication. That is, the DMRS determination unit 235 determines the type of DMRS. The DMRS determination unit 235 generates a DMRS replica according to a predetermined calculation formula using the scramble value and the offset value indicated in the notification signal. The DMRS determination unit 235 includes a replica for cellular communication (hereinafter sometimes referred to as “replica for cellular communication”) and a replica for D2D communication (hereinafter sometimes referred to as “replica for D2D communication”). Create two replicas. The DMRS determination unit 235 performs a correlation calculation between the received DMRS and these two replicas to obtain a first correlation value and a second correlation value. The first correlation value is a correlation value between the received DMRS and the cellular communication replica, and the second correlation value is a correlation value between the received DMRS and the D2D communication replica. Then, the DMRS determining unit 235 determines whether the received DMRS is the cellular communication DMRS or the D2D communication DMRS based on the comparison result between the first correlation value and the second correlation value. . That is, DMRS determination section 235 determines that the received DMRS is a cellular communication DMRS when the first correlation value is greater than or equal to the second correlation value. On the other hand, when the first correlation value is less than the second correlation value, the DMRS determination unit 235 determines that the received DMRS is a DMRS for D2D communication. Then, the DMRS determination unit 235 notifies the blind detection unit 237 of the determination result.

The blind detection unit 237 determines a search space that is a target of blind detection according to the determination result in the DMRS determination unit 235, and performs blind detection only in the target search space.

That is, when the DMRS determination unit 235 determines that the received DMRS is a DMRS for cellular communication, the blind detection unit 237 selects a search space to be subjected to blind detection among the search spaces SS0 to SS9 shown in FIG. The search spaces SS0 to SS5 are determined. Then, the blind detection unit 237 performs blind detection for each search unit only in each of the search spaces SS0 to SS5, and detects cellular communication DCI addressed to the communication terminal 20.

On the other hand, when the DMRS determination unit 235 determines that the received DMRS is a DMRS for D2D communication, the blind detection unit 237 searches for the search space to be subjected to blind detection among the search spaces SS0 to SS9 shown in FIG. Are determined as search spaces SS6 to SS9. Then, the blind detection unit 237 performs blind detection for each search unit only in each of the search spaces SS6 to SS9, and detects the DCI for D2D communication addressed to the communication terminal 20.

That is, the search spaces SS0 to SS5 correspond to the first search range for cellular communication, and the search spaces SS6 to SS9 correspond to the second search range for D2D. The blind detection unit 237 outputs the DCI for cellular communication detected in the search spaces SS0 to SS5 to the cellular communication control unit 213, and outputs the DCI for D2D communication detected in the search spaces SS6 to SS9 to the D2D communication control unit 212.

The D2D communication control unit 212 notifies the mapping unit 218 of the RA result indicated in the DCI for D2D communication. When the D2D communication DCI is input from the blind detection unit 237, the D2D communication control unit 212 issues a signal formation instruction to the D2D signal formation unit 215.

Upon receiving a signal formation instruction from the D2D communication control unit 212, the D2D signal forming unit 215 converts the data addressed to the communication terminal UE2, that is, D2D data into a predetermined signal format for D2D communication, and forms a D2D signal. The D2D signal is output to the encoding unit 216.

Encoder 216 encodes the D2D signal and outputs the encoded D2D signal to modulator 217.

Modulation section 217 modulates the encoded D2D signal and outputs the modulated D2D signal to mapping section 218.

The mapping unit 218 maps the D2D signal to the wireless communication resource indicated by the RA result notified from the D2D communication control unit 212 and outputs the D2D signal to the wireless transmission unit 225.

The cellular communication control unit 213 notifies the mapping unit 224 of the RA result indicated in the DCI for cellular communication. In addition, when the cellular communication control unit 213 receives the DCI for cellular communication from the blind detection unit 237, the cellular communication control unit 213 issues a signal formation instruction to the UL signal forming unit 221.

Upon receiving a signal formation instruction from the cellular communication control unit 213, the UL signal forming unit 221 converts the data addressed to the base station BS1, that is, UL data into a predetermined signal format of the UL signal, and forms a UL signal. The UL signal is output to the encoding unit 222.

Encoder 222 encodes the UL signal and outputs the encoded UL signal to modulator 223.

Modulation section 223 modulates the encoded UL signal, and outputs the modulated UL signal to mapping section 224.

The mapping unit 224 maps the UL signal to the radio communication resource indicated by the RA result notified from the cellular communication control unit 213, and outputs the UL signal to the radio transmission unit 225.

The wireless transmission unit 225 performs digital-analog conversion, up-conversion, and the like on the baseband D2D signal and the baseband UL signal to obtain each wireless signal, and transmits each wireless signal to the communication terminal via the transmission antenna 226. It transmits to UE2 and base station BS1, respectively.

<Operation of base station and communication terminal>
First, the operation of the base station 10 will be described.

In the base station 10 shown in FIG. 4, the DMRS generating unit 106 converts the pseudo-random sequence having the code length 144 formed from the codes r (0) to r (143), for example, according to the equation (1), to the DMRS for cellular communication. And D2D communication DMRS. In Equation (1), c (2m) and c (2m + 1) are Gold codes, and N _RB ^{max, DL} represents the number of resource blocks allocated to each communication terminal. Here, for example, N _RB ^{max, DL} is “ 12 ”is constant.

However, when the DCI formed by the DCI forming unit 11 is the DCI for cellular communication, the DMRS generating unit 106 generates the DMRS for cellular communication using the initial value c _{init, cell} shown in Expression (2). On the other hand, when the DCI formed by the DCI forming unit 11 is the DCI for D2D communication, the DMRS generating unit 106 generates the DM2 for D2D communication using the initial values c _{init and D2D} shown in Expression (3). .

In equations (2) and (3), c _{init, cell} and c _{init, D2D} are initial values of c (2m) and c (2m + 1) in equation (1). Since n _s is the slot number, each sub-frame is formed from two slot, n _s takes a value of "0" or "1". n _{ID, i} ^EPDCCH is a scramble value and ^takes any value from 0 to 533 and is designated by the base station 10. n _SCID ^EPDCCH is the first offset value, for example, “2”. N _D2D is a second offset value, which is an offset value for DM2 for D2D communication. N _D2D is “2”, for example. That is, the initial value c _{init, D2D} used for generating the DMRS for D2D communication is obtained by adding the offset value N _D2D to the initial value c _{init, cell} used for generating the DMRS for cellular communication. Thus, the cellular communication DMRS and the D2D communication DMRS are the same by making the initial values of c (2m) and c (2m + 1) in Equation (1) different for cellular communication and D2D communication. The code sequences have different sequence lengths. That is, the DMRS for cellular communication is the first code sequence generated according to the equation (1) and the initial value c _{init, cell} . On the other hand, the DMRS for D2D communication is a second code sequence different from the first code sequence, and the initial value c obtained by adding the offset value N _D2D to the equation (1) and the initial value c _{init, cell.} It is a code sequence generated according to _{init, D2D} .

In contrast, the communication terminal 20 operates as follows.

In communication terminal 20 shown in FIG. 5, DMRS determining section 235 generates a DMRS replica for cellular communication (that is, a replica for cellular communication) according to equations (1) and (2), similarly to base station 10. . Similarly to the base station 10, the DMRS determination unit 235 generates a D2D communication DMRS replica (that is, a D2D communication replica) according to the equations (1) and (3). The DMRS determination unit 235 performs a correlation operation between the received DMRS and the cellular communication replica to obtain a first correlation value. In addition, the DMRS determination unit 235 obtains a second correlation value by performing a correlation calculation between the received DMRS and the D2D communication replica. When the first correlation value is equal to or greater than the second correlation value, DMRS determination section 235 determines that the received DMRS is a cellular communication DMRS. On the other hand, when the first correlation value is less than the second correlation value, the DMRS determination unit 235 determines that the received DMRS is a DMRS for D2D communication.

<Processing sequence of communication system>
FIG. 6 is a diagram illustrating an example of a processing sequence of the communication system according to the first embodiment.

In FIG. 6, the base station BS1 notifies the communication terminal UE1 of the scramble value and the offset value using the notification signal (step S41). Scramble value, equation (2), an n _{ID, i} ^EPDCCH shown in (3), the offset value, the formula (2) includes a n _SCID ^EPDCCH and N _D2D shown in (3).

Next, the communication terminal UE1 generates a cellular communication replica and a D2D communication replica according to equations (1) to (3) using the scramble value notified from the base station BS1 and the offset value ( Step S42).

Next, the base station BS1 transmits an EPDCCH signal including DCI and DMRS to the communication terminal UE1 (step S43). DCI is DCI for cellular communication or DCI for D2D communication. DMRS is DMRS for cellular communication or DMRS for D2D communication. The EPDCCH signal including the DCI for cellular communication is accompanied by DMRS for cellular communication. On the other hand, the DMDC for D2D communication accompanies the EPDCCH signal including the DCI for D2D communication.

Next, the communication terminal UE1 obtains a first correlation value by performing a correlation calculation between the reception DMRS and the cellular communication replica, and performs a correlation calculation between the reception DMRS and the D2D communication replica to obtain a second correlation value. Obtain (step S44).

Next, the communication terminal UE1 determines the type of DMRS (step S45). When the first correlation value is equal to or higher than the second correlation value, the communication terminal UE1 determines that the received DMRS is a cellular communication DMRS. On the other hand, when the first correlation value is less than the second correlation value, the communication terminal UE1 determines that the received DMRS is a DM2 for D2D communication.

Next, the communication terminal UE1 performs blind detection in the search range corresponding to the determination result in step S45 (step S46). When the communication terminal UE1 determines that the received DMRS is a DMRS for cellular communication, the communication terminal UE1 performs blind detection in the search range for cellular communication. On the other hand, when the communication terminal UE1 determines that the received DMRS is a DMRS for D2D communication, the communication terminal UE1 performs blind detection in a search range for D2D communication, which is a search range different from the search range for cellular communication. For example, when the communication terminal UE1 determines that the received DMRS is a cellular communication DMRS, the communication terminal UE1 performs brand detection in each of the search spaces SS0 to SS5 shown in FIG. On the other hand, when the communication terminal UE1 determines that the received DMRS is a DM2 for D2D communication, the communication terminal UE1 performs blind detection in each of the search spaces SS6 to SS9 shown in FIG.

As described above, in the first embodiment, the communication system 1 includes the base station BS1, the communication terminal UE1, and the communication terminal UE2. The communication terminal UE1 can perform cellular communication with the base station BS1, but can perform D2D communication with the communication terminal UE2 without going through the base station BS1.

The base station BS1 is a base station that transmits an EPDCCH signal including DCI indicating a radio resource allocation result and a DMRS accompanying the EPDCCH signal to the communication terminal UE1. When the base station BS1 notifies the communication terminal UE1 of the cellular communication RA result using the EPDCCH signal, the base station BS1 sets DMRS as the first code sequence generated using the first initial value. On the other hand, when the base station BS1 notifies the communication terminal UE1 of the RA result for D2D communication using the EPDCCH signal, the second code generated using the second initial value obtained by adding the offset value to the first initial value. Let the series be DMRS.

On the other hand, the communication terminal UE1 receives DMRS from the base station BS1. When determining that the received DMRS is the first code sequence, the communication terminal UE1 performs DCI blind detection in the first search range for cellular communication. On the other hand, when the communication terminal UE1 determines that the received DMRS is the second code sequence, the communication terminal UE1 performs DCI blind detection in the second search range for D2D communication.

In addition, the base station 10 can communicate the EPDCCH signal including the DCI indicating the radio resource allocation result and the DMRS associated with the EPDCCH signal with the base station 10 and can perform D2D communication with the communication terminal UE2. It is a base station that transmits to the terminal UE1. The base station 10 includes a DMRS generator 106 and a radio transmitter 108. When notifying the cellular communication RA result to the communication terminal UE1 using the EPDCCH signal, the DMRS generating unit 106 generates the first code sequence as the DMRS using the first initial value. On the other hand, when the DMRS generating unit 106 notifies the communication terminal UE1 of the RA result for D2D communication using the EPDCCH signal, the DMRS generating unit 106 uses the second initial value obtained by adding the offset value to the first initial value. Is generated as DMRS. The radio transmission unit 108 transmits the DMRS generated by the DMRS generation unit 106 to the communication terminal UE1.

In addition, the communication terminal 20 can perform cellular communication with the base station 10 that transmits the EPDCCH signal including the DCI indicating the radio resource allocation result and the DMRS accompanying the EPDCCH signal. It is possible to perform D2D communication with the communication terminal UE2 without intervention. The communication terminal 20 includes a wireless reception unit 231 and a blind detection unit 237. The radio reception unit 231 receives DMRS from the base station 10. When it is determined that the received DMRS is the first code sequence generated using the first initial value, the blind detection unit 237 performs DCI blind detection in the first search range for cellular communication. On the other hand, when the blind detection unit 237 determines that the received DMRS is the second code sequence generated using the second initial value obtained by adding the offset value to the first initial value, the blind detection unit 237 is for D2D communication. DCI blind detection is performed in the second search range.

In this way, the communication terminal UE1 (communication terminal 10) can determine whether the DCI included in the EPDCCH signal is DCI for cellular communication or DCI for D2D communication using the received DMRS. Therefore, when DCI included in the EPDCCH signal is DCI for cellular communication, communication terminal UE1 performs DCI blind detection in the first search range for cellular communication. Further, when the DCI included in the EPDCCH signal is the DCI for D2D communication, the communication terminal UE1 performs DCI blind detection in the second search range for D2D communication. In other words, when the DCI included in the EPDCCH signal is the DCI for cellular communication, the communication terminal UE1 does not perform blind detection in the second search range for D2D communication. Communication terminal UE1 does not perform blind detection in the first search range for cellular communication when the DCI included in the EPDCCH signal is DCI for D2D communication. Thereby, as shown in FIG. 2, even when a new search space for DCI in a new format for D2D communication is prepared, the maximum number of times of blind detection in one subframe can be suppressed.

For example, when a new search space for DCI of a new format for D2D communication is prepared, if blind detection is performed for all search spaces in one subframe, the maximum number of times of blind detection in one subframe Is 60 times as described above.

On the other hand, according to the first embodiment, when the DCI included in the EPDCCH signal is the DCI for cellular communication, 16 unnecessary blind detections for the DCI for D2D communication can be avoided, so the maximum number of times of blind detection is 44 times for DCI for cellular communication. On the other hand, when DCI included in the EPDCCH signal is DCI for D2D communication, 44 unnecessary blind detections for DCI for cellular communication can be avoided, so the maximum number of blind detections is 16 times for DCI for D2D communication. It becomes. Therefore, according to the first embodiment, even when a new search space for DCI having a new format for D2D communication is prepared in performing D2D communication, the power consumption of the communication terminal UE1 when performing D2D communication is increased. Can be suppressed.

Further, according to the first embodiment, the base station BS1 notifies the communication terminal UE1 of the offset value. The communication terminal UE1 is generated using the first initial value obtained by adding the offset value to the magnitude of the first correlation value between the cellular communication replica generated using the first initial value and the received DMRS. Based on the comparison result of the second correlation value between the replica for D2D communication and the received DMRS, the DCI search range is set to either the first search range for cellular communication or the second search range for D2D communication. decide.

In this way, the communication terminal UE1 can generate the same replica as the DMRS generated by the base station BS1. In addition, since the communication terminal UE1 determines the DCI search range based on the comparison result of the magnitude of the correlation value between the received DMRS and the replica, the DCI search range is used as the first search range for cellular communication or for D2D communication. The second search range can be accurately determined.

[Other embodiments]
[1] The base station 10 of the above embodiment can be realized by the following hardware configuration. FIG. 7 is a diagram illustrating a hardware configuration example of the base station. As illustrated in FIG. 7, the base station 10 includes a processor 10a, a memory 10b, a wireless communication module 10c, and a network interface module 10d as hardware components. Examples of the processor 10a include a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and an FPGA (Field Programmable Gate Array). Further, the base stations 10 and 30 may include an LSI (Large Scale Integrated circuit) including a processor 10a and peripheral circuits. Examples of the memory 10b include RAM such as SDRAM, ROM, flash memory, and the like. The wireless transmission unit 108, the duplexer 109, the antenna 110, and the wireless reception unit 111 are realized by the wireless communication module 10c. The DCI formation unit 11, the EPDCCH signal generation units 102 and 105, the mapping unit 103, the DMRS generation unit 106, the notification signal generation unit 107, and the UL data acquisition unit 112 are realized by the processor 10a.

[2] The communication terminal 20 of the above embodiment can be realized by the following hardware configuration. FIG. 8 is a diagram illustrating a hardware configuration example of the communication terminal. As illustrated in FIG. 8, the communication terminal 20 includes a processor 20a, a memory 20b, and a wireless communication module 20c as hardware components. Examples of the processor 20a include a CPU, DSP, FPGA, and the like. The communication terminal 20 may include an LSI including a processor 20a and peripheral circuits. Examples of the memory 20b include RAM such as SDRAM, ROM, flash memory, and the like. The reception antenna 201, the separator 202, the wireless reception units 203 and 231, the wireless transmission unit 225, and the transmission antenna 226 are realized by the wireless communication module 20c. Demodulation unit 204,233, decoding unit 205,236, demapping unit 232, channel estimation unit 234, DMRS determination unit 235, blind detection unit 237, communication control unit 21, D2D communication unit 22, The cellular communication unit 23 is realized by the processor 20a.

[3] The EPDCCH in the above embodiment may be expressed as ePDCCH.

[4] A base station may be called a radio base station, Base Station, eNodeB, or NodeB. The communication terminal is sometimes called a wireless terminal, a mobile station, or a user terminal (UE: User Equipment).

DESCRIPTION OF SYMBOLS 1 Communication system BS1,10 Base station UE1, UE2,20 Communication terminal 11 DCI formation part 101 D2D communication DCI formation part 102,105 EPDCCH signal generation part 103 Mapping part 104 Cellular communication DCI formation part 235 DMRS judgment part 237 Blind detection Unit 212 D2D communication control unit 213 cellular communication control unit

Claims (6)

A base station,
A first communication terminal;
A communication system comprising: a second communication terminal capable of communicating directly with the first communication terminal without going through the base station while being able to communicate with the base station,
The base station
A base station that transmits a control channel signal including control information indicating a radio resource allocation result and a reference signal accompanying the control channel signal to the second communication terminal,
When notifying the second communication terminal of the first assignment result of the first radio resource assigned to the first communication that is communication between the base station and the second communication terminal using the control channel signal, The first code sequence generated using the first initial value as the reference signal,
Notifying the second communication terminal of the second assignment result of the second radio resource assigned to the second communication which is a direct communication between the second communication terminal and the first communication terminal using the control channel signal. The second code sequence generated using a second initial value obtained by adding an offset value to the first initial value as the reference signal,
The second communication terminal is
Receiving the reference signal from the base station;
When it is determined that the received reference signal is the first code sequence, the control information is detected in the first search range for the first communication,
When it is determined that the received reference signal is the second code sequence, the control information is detected in the second search range for the second communication.
Communications system. The base station notifies the second communication terminal of the offset value,
The second communication terminal is
Generated using the first initial value generated from the first replica and the first correlation value between the received reference signal and the second initial value obtained by adding the offset value to the first initial value The control information search range is determined as either the first search range or the second search range based on a comparison result between the second replica and the magnitude of the second correlation value of the received reference signal. ,
The communication system according to claim 1. A second communication terminal capable of communicating directly with the first communication terminal while being able to communicate with the own station a control channel signal including control information indicating a radio resource allocation result and a reference signal accompanying the control channel signal A base station transmitting to
When notifying the second communication terminal of the first assignment result of the first radio resource assigned to the communication between the local station and the second communication terminal using the control channel signal, the first initial value is used. And generating the first code sequence as the reference signal, the second allocation result of the second radio resource allocated to the direct communication between the second communication terminal and the first communication terminal as the control channel signal When notifying to the second communication terminal using, a generating unit that generates a second code sequence as the reference signal using a second initial value obtained by adding an offset value to the first initial value;
A transmission unit for transmitting the reference signal to the second communication terminal;
A base station. While it is possible to perform first communication with a base station that transmits a control channel signal including control information indicating a radio resource allocation result and a reference signal associated with the control channel signal, the base station A communication terminal capable of performing second communication that communicates directly with other communication terminals without intervention,
A receiver for receiving the reference signal from the base station;
When it is determined that the received reference signal is the first code sequence generated using the first initial value, the control information is detected in the first search range for the first communication. so,
When it is determined that the received reference signal is a second code sequence generated using a second initial value obtained by adding an offset value to the first initial value, the second signal for the second communication is used. A detection unit for detecting the control information in a search range;
A communication terminal comprising: Reference signal generation in a base station that transmits a control channel signal including control information indicating a radio resource allocation result and a reference signal accompanying the control channel signal to a second communication terminal capable of directly communicating with the first communication terminal A method,
When notifying the second communication terminal of the allocation result of the first radio resource allocated to the communication between the base station and the second communication terminal using the control channel signal, the first initial value is used. While generating a first code sequence as the reference signal,
When notifying the second communication terminal of the allocation result of the second radio resource allocated to the direct communication between the second communication terminal and the first communication terminal using the control channel signal, the first initial A second code sequence is generated as the reference signal using a second initial value obtained by adding an offset value to the value,
Reference signal generation method. While it is possible to perform first communication with a base station that transmits a control channel signal including control information indicating a radio resource allocation result and a reference signal associated with the control channel signal, the base station A control information detection method in a communication terminal capable of performing second communication that communicates directly with another communication terminal without intervention,
Receiving the reference signal from the base station;
When it is determined that the received reference signal is the first code sequence generated using the first initial value, the control information is detected in the first search range for the first communication,
When it is determined that the received reference signal is a second code sequence generated using a second initial value obtained by adding an offset value to the first initial value, the second search range for the second communication Detecting the control information in
Control information detection method.

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