JP6594017B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system that performs wireless communication between a communication terminal device such as a mobile terminal device and a base station device.

  In the 3rd Generation Partnership Project (3GPP), which is a standardization organization for mobile communication systems, the wireless section is called Long Term Evolution (LTE), and the core network and wireless access network (hereinafter collectively referred to as the network) For example, a communication system called System Architecture Evolution (SAE) has been studied (for example, see Non-Patent Documents 1 to 12). This communication method is also called a 3.9G (3.9 Generation) system.

  As an LTE access scheme, OFDM (Orthogonal Frequency Division Multiplexing) is used in the downlink direction, and SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in the uplink direction. Also, LTE differs from W-CDMA (Wideband Code Division Multiple Access) in that it does not include circuit switching and is only a packet communication method.

  Non-Patent Document 1 (Chapter 5) described in 3GPP will be described with reference to FIG. FIG. 1 is an explanatory diagram showing a configuration of a radio frame used in an LTE communication system. In FIG. 1, one radio frame is 10 ms. The radio frame is divided into ten equally sized subframes. The subframe is divided into two equally sized slots. For each radio frame, a downlink synchronization signal is included in the first and sixth subframes. The synchronization signal includes a first synchronization signal (Primary Synchronization Signal: P-SS) and a second synchronization signal (Secondary Synchronization Signal: S-SS).

  Non-Patent Document 1 (Chapter 5) describes the determination items regarding the channel configuration in the LTE system in 3GPP. It is assumed that the same channel configuration as that of the non-CSG cell is also used in a CSG (Closed Subscriber Group) cell.

  A physical broadcast channel (PBCH) is a communication terminal device such as a base station device (hereinafter simply referred to as “base station”) to a mobile terminal device (hereinafter also simply referred to as “mobile terminal”). It is a channel for downlink transmission to (hereinafter sometimes simply referred to as “communication terminal”). A BCH transport block is mapped to four subframes in a 40 ms interval. There is no obvious signaling of 40ms timing.

  A physical control format indicator channel (PCFICH) is a channel for downlink transmission from a base station to a communication terminal. PCFICH notifies the communication terminal of the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols used for PDCCHs from the base station. PCFICH is transmitted for each subframe.

  A physical downlink control channel (PDCCH) is a channel for downlink transmission from a base station to a communication terminal. The PDCCH is information on resource allocation (allocation) of a downlink shared channel (DL-SCH) that is one of transport channels described later, and a paging channel (PCH) that is one of transport channels described later. ) Resource allocation (allocation) information and HARQ (Hybrid Automatic Repeat reQuest) information related to DL-SCH. The PDCCH carries an Uplink Scheduling Grant. The PDCCH carries Ack (Acknowledgement) / Nack (Negative Acknowledgement), which is a response signal for uplink transmission. The PDCCH is also called an L1 / L2 control signal.

  A physical downlink shared channel (PDSCH) is a channel for downlink transmission from a base station to a communication terminal. The PDSCH is mapped with a downlink shared channel (DL-SCH) which is a transport channel and PCH which is a transport channel.

  A physical multicast channel (PMCH) is a channel for downlink transmission from a base station to a communication terminal. A multicast channel (Multicast Channel: MCH) that is a transport channel is mapped to the PMCH.

  A physical uplink control channel (PUCCH) is a channel for uplink transmission from a communication terminal to a base station. The PUCCH carries Ack / Nack that is a response signal for downlink transmission. The PUCCH carries a CQI (Channel Quality Indicator) report. CQI is quality information indicating the quality of received data or channel quality. The PUCCH carries a scheduling request (SR).

  A physical uplink shared channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. An uplink shared channel (UL-SCH) that is one of the transport channels is mapped to the PUSCH.

  A physical HARQ indicator channel (PHICH) is a channel for downlink transmission from a base station to a communication terminal. PHICH carries Ack / Nack which is a response signal for uplink transmission. A physical random access channel (PRACH) is a channel for uplink transmission from a communication terminal to a base station. The PRACH carries a random access preamble.

  A downlink reference signal (Reference Signal: RS) is a symbol known as an LTE communication system. The following five types of downlink reference signals are defined. Cell-specific reference signal (Cell-specific Reference Signal: CRS), MBSFN reference signal (MBSFN Reference Signal), UE-specific reference signal (UE-specific Reference Signal) reference signal for data demodulation (Demodulation Reference Signal: DM-RS) Positioning reference signal (PRS), channel state information reference signal (CSI-RS). As a measurement of a physical layer of a communication terminal, there is a reference signal received power (RSRP) measurement.

  The transport channel described in Non-Patent Document 1 (Chapter 5) will be described. Of the downlink transport channels, a broadcast channel (Broadcast Channel: BCH) is broadcast to the entire coverage of the base station (cell). The BCH is mapped to the physical broadcast channel (PBCH).

  Retransmission control by HARQ (Hybrid ARQ) is applied to the downlink shared channel (DL-SCH). DL-SCH can be broadcast to the entire coverage of a base station (cell). DL-SCH supports dynamic or semi-static resource allocation. The quasi-static resource allocation is also called persistent scheduling. DL-SCH supports discontinuous reception (DRX) of a communication terminal in order to reduce power consumption of the communication terminal. DL-SCH is mapped to a physical downlink shared channel (PDSCH).

  The paging channel (PCH) supports DRX of the communication terminal in order to enable low power consumption of the communication terminal. The PCH is required to be broadcast to the entire coverage of the base station (cell). The PCH is mapped to a physical resource such as a physical downlink shared channel (PDSCH) that can be dynamically used for traffic.

  The multicast channel (MCH) is used for broadcast to the entire coverage of the base station (cell). The MCH supports SFN combining of MBMS (Multimedia Broadcast Multicast Service) services (MTCH and MCCH) in multi-cell transmission. The MCH supports quasi-static resource allocation. MCH is mapped to PMCH.

  Among uplink transport channels, retransmission control by HARQ (Hybrid ARQ) is applied to an uplink shared channel (UL-SCH). UL-SCH supports dynamic or semi-static resource allocation. UL-SCH is mapped to a physical uplink shared channel (PUSCH).

  A random access channel (RACH) is limited to control information. RACH is at risk of collision. The RACH is mapped to a physical random access channel (PRACH).

  HARQ will be described. HARQ is a technique for improving the communication quality of a transmission path by combining automatic repeat request (ARQ) and error correction (Forward Error Correction). HARQ has an advantage that error correction functions effectively by retransmission even for a transmission path whose communication quality changes. In particular, further quality improvement can be obtained by combining the initial transmission reception result and the retransmission reception result upon retransmission.

  An example of the retransmission method will be described. When the reception side cannot decode the received data correctly, in other words, when a CRC (Cyclic Redundancy Check) error occurs (CRC = NG), “Nack” is transmitted from the reception side to the transmission side. The transmitting side that has received “Nack” retransmits the data. When the reception side can correctly decode the received data, in other words, when no CRC error occurs (CRC = OK), “Ack” is transmitted from the reception side to the transmission side. The transmitting side that has received “Ack” transmits the next data.

  A logical channel (logical channel) described in Non-Patent Document 1 (Chapter 6) will be described. The broadcast control channel (BCCH) is a downlink channel for broadcast system control information. The BCCH that is a logical channel is mapped to a broadcast channel (BCH) that is a transport channel or a downlink shared channel (DL-SCH).

  The paging control channel (Paging Control Channel: PCCH) is a downlink channel for transmitting changes of paging information (Paging Information) and system information (System Information). PCCH is used when the network does not know the cell location of the communication terminal. The PCCH that is a logical channel is mapped to a paging channel (PCH) that is a transport channel.

  The common control channel (CCCH) is a channel for transmission control information between the communication terminal and the base station. CCCH is used when the communication terminal does not have an RRC connection with the network. In the downlink direction, the CCCH is mapped to a downlink shared channel (DL-SCH) that is a transport channel. In the uplink direction, the CCCH is mapped to an uplink shared channel (UL-SCH) that is a transport channel.

  A multicast control channel (MCCH) is a downlink channel for one-to-many transmission. MCCH is used for transmission of MBMS control information for one or several MTCHs from a network to a communication terminal. MCCH is used only for communication terminals receiving MBMS. The MCCH is mapped to a multicast channel (MCH) that is a transport channel.

  The dedicated control channel (DCCH) is a channel for transmitting individual control information between the communication terminal and the network on a one-to-one basis. The DCCH is used when the communication terminal is an RRC connection. The DCCH is mapped to the uplink shared channel (UL-SCH) in the uplink, and is mapped to the downlink shared channel (DL-SCH) in the downlink.

  The dedicated traffic channel (Dedicated Traffic Channel: DTCH) is a channel for one-to-one communication to an individual communication terminal for transmitting user information. DTCH exists for both uplink and downlink. The DTCH is mapped to the uplink shared channel (UL-SCH) in the uplink, and is mapped to the downlink shared channel (DL-SCH) in the downlink.

  The multicast traffic channel (MTCH) is a downlink channel for transmitting traffic data from the network to the communication terminal. MTCH is a channel used only for communication terminals receiving MBMS. The MTCH is mapped to a multicast channel (MCH).

  CGI is a cell global identifier. ECGI is an E-UTRAN Cell Global Identifier. In LTE, LTE-A (Long Term Evolution Advanced) and UMTS (Universal Mobile Telecommunication System) described later, a closed subscriber group (CSG) cell is introduced.

  A CSG (Closed Subscriber Group) cell is a cell in which an operator identifies an available subscriber (hereinafter may be referred to as a “specific subscriber cell”). The identified subscriber is allowed to access one or more cells of the Public Land Mobile Network (PLMN). One or more cells to which the identified subscribers are allowed access are referred to as “CSG cells (CSG cells (s))”. However, PLMN has access restrictions.

  The CSG cell is a part of a PLMN that broadcasts a unique CSG identity (CSG identity: CSG ID; CSG-ID) and broadcasts “TRUE” using CSG indication (CSG Indication). Members of the subscriber group who have been registered in advance and permitted access the CSG cell using the CSG-ID that is the access permission information.

  The CSG-ID is broadcast by the CSG cell or cell. There are a plurality of CSG-IDs in an LTE communication system. The CSG-ID is then used by a communication terminal (UE) to facilitate access for CSG-related members.

  The position tracking of the communication terminal is performed in units of areas composed of one or more cells. The position tracking is performed to track the position of the communication terminal and call the communication terminal even in the standby state, in other words, to enable the communication terminal to receive a call. This area for tracking the location of the communication terminal is called a tracking area.

  In 3GPP, base stations called Home-NodeB (Home-NB; HNB) and Home-eNodeB (Home-eNB; HeNB) are being studied. HNB in UTRAN and HeNB in E-UTRAN are base stations for access services for homes, corporations, and commercials, for example. Non-Patent Document 3 discloses three different modes of access to HeNB and HNB. Specifically, an open access mode, a closed access mode, and a hybrid access mode are disclosed.

  Each mode has the following characteristics. In the open access mode, the HeNB and HNB are operated as normal cells of a normal operator. In the closed access mode, the HeNB and HNB are operated as CSG cells. This CSG cell is a CSG cell accessible only to CSG members. In the hybrid access mode, the HeNB and HNB are operated as CSG cells in which non-CSG members are also allowed to access at the same time. In other words, a hybrid access mode cell (also referred to as a hybrid cell) is a cell that supports both an open access mode and a closed access mode.

  In 3GPP, among all physical cell identities (PCIs), there is a PCI range reserved by the network for use in CSG cells (see Non-Patent Document 1 chapter 10.5.1.1). Dividing the PCI range may be referred to as PCI split. Information on the PCI split (also referred to as PCI split information) is notified from the base station to the communication terminals being served by the system information. Being served by a base station means that the base station is a serving cell.

  Non-Patent Document 4 discloses a basic operation of a communication terminal using PCI split. A communication terminal that does not have PCI split information needs to perform cell search using all PCIs, for example, using all 504 codes. On the other hand, a communication terminal having PCI split information can perform a cell search using the PCI split information.

  In 3GPP, as a release 10, a Long Term Evolution Advanced (LTE-A) standard is being developed (see Non-Patent Document 5 and Non-Patent Document 6). LTE-A is based on the LTE wireless section communication system, and is configured by adding several new technologies.

  In the LTE-A system, two or more component carriers (CCs) are aggregated (also referred to as “aggregation”) in order to support wider transmission bandwidths up to 100 MHz. Carrier aggregation (CA) has been studied.

  When CA is configured, the UE has a network (NW) and only one RRC connection. In the RRC connection, one serving cell provides NAS mobility information and security input. This cell is called a primary cell (PCell). In the downlink, a carrier corresponding to PCell is a downlink primary component carrier (DL PCC). In the uplink, the carrier corresponding to the PCell is an uplink primary component carrier (UL PCC).

  Depending on the UE capability (capability), a secondary cell (SCell) is configured to form a set of a PCell and a serving cell. In the downlink, the carrier corresponding to the SCell is a downlink secondary component carrier (DL SCC). In the uplink, the carrier corresponding to the SCell is an uplink secondary component carrier (UL SCC).

  A set of one PCell and a serving cell composed of one or more SCells is configured for one UE.

  In addition, new technologies in LTE-A include a technology that supports a wider bandwidth (Wider bandwidth extension), a coordinated multiple point transmission and reception (CoMP) technology, and the like. Non-Patent Document 7 describes CoMP being studied for LTE-A by 3GPP.

  The amount of mobile network traffic is increasing and the communication speed is also increasing. When LTE and LTE-A start full-scale operation, it is expected that the communication speed is further increased and the traffic volume is increased.

  In addition, with the spread of smartphones and tablet-type terminal devices, the amount of traffic due to cellular wireless communication has increased explosively, and there is a concern over the shortage of wireless resources around the world.

  In response to the problem of an increase in traffic volume, the 3GPP is proceeding with the formulation of the 12th release standard. In the 12th edition of the standard, use of a small eNB is considered in order to cope with a huge amount of traffic in the future. For example, a technology for increasing frequency utilization efficiency and increasing communication capacity by installing a large number of small eNBs and configuring a large number of small cells has been studied.

  Among them, dual connectivity is discussed as a technology for connecting a communication terminal to both the macro cell and the small cell when the macro cell and the small cell overlap (non-patent document 11). reference).

  Furthermore, a fifth generation (hereinafter sometimes referred to as “5G”) mobile communication system aimed at starting service after 2020 is being studied for mobile communication that is becoming more sophisticated. For example, in Europe, 5G requirements are compiled by an organization called METIS (see Non-Patent Document 12).

  In the 5G mobile communication system, the system capacity is 1000 times, the data transmission speed is 100 times, the data processing delay is 1/10 (1/10), and the number of simultaneous connections of communication terminals is 100 times that of the LTE system. As a requirement, further reduction in power consumption and cost reduction of the apparatus are mentioned as requirements.

  In order to satisfy the above requirements, use of antenna beam forming technology to increase the data transmission capacity by using the frequency in a wide band and increase the frequency efficiency to increase the data transmission capacity and enable spatial multiplexing Is being considered. In order to secure a wideband frequency, it has been studied to use a high frequency such as a 3-30 GHz microwave (Super High Frequency: SHF) band as a frequency used for wireless access.

  When a high frequency is used, the wavelength is shortened, so that the amount of attenuation of the radio wave is large, and there is a problem that the propagation distance of the radio wave is shortened as compared with conventional communication systems. Furthermore, the influence of the Doppler shift becomes large, and the moving speed of the communication terminal may greatly affect the communication performance.

  In addition, since various communication terminals are accommodated in the 5G mobile communication system, as a radio access method, only ultra-low-speed data transmission such as sensors is supported from communication terminals compatible with high-speed data transmission such as 4K digital television. It is necessary to handle the communication terminals up to the same system.

  Therefore, since it is difficult for the conventional LTE communication system to satisfy the 5G requirement, a new system is being studied as a 5G wireless access system.

3GPP TS36.300 V11.7.0 3GPP TS36.211 V12.3.0 3GPP S1-083461 3GPP R2-082899 3GPP TR 36.814 V9.0.0 3GPP TR 36.912 V10.0.0 3GPP TR 36.819 V11.1.0 3GPP TS 36.141 V11.1.0 3GPP TS36.212 V12.2.0 IEEE Global Telecommunications Conference (GLOBECOM), Antenna Array Calibration Using Frequency Selection in OFDMA / TDD Systems pp.1-5, Nov.30-Dec.4 2008. 3GPP TR36.842 V0.2.0 "Scenarios, requirements and KPIs for 5G mobile and wireless system", [online], April 30, 2013, ICT-317669-METIS / D1.1, [March 30, 2015 search], Internet <https://www.metis2020.com/documents/deliverables/>

  There are items that cannot be satisfied when the above-mentioned requirements for the 5G mobile communication system are to be realized by the radio access scheme used in LTE.

  For example, when a high frequency is used, the influence of the Doppler shift becomes large and the communication performance is greatly deteriorated when moving at a high speed at 15 kHz which is the LTE subcarrier interval of the LTE specification. In addition, when a wide frequency band is processed, a fast Fourier transform (FFT) size for OFDM modulation / demodulation becomes large, which causes problems in terms of mounting such as circuit scale and software processing amount. Here, the FFT size refers to the number of sampling data in the time domain used when performing FFT.

  In addition, in the LTE specification, data is processed in units of subframes, for example, in units of 1 ms, so in order to satisfy the requirement of low delay of 1/10 (1/10) compared to the LTE system, The radio frame needs to be small.

  Moreover, since it is necessary to ensure a collective frequency for broadband communication, it becomes a region where the carrier frequency is high. In order to cope with this, improvement of a signal-to-noise ratio (abbreviation: SNR) by a multi-element antenna including a plurality of antenna elements has been studied.

  Therefore, it is impossible to apply the conventional LTE radio access scheme to the radio access scheme of the 5G mobile communication system without any ingenuity.

  An object of the present invention is to provide a communication system capable of performing communication with relatively high communication quality and throughput by using a multi-element antenna including a plurality of antenna elements.

The communication system of the present invention is a communication system including a base station apparatus and a communication terminal apparatus that transmit and receive signals using a multi-element antenna including a plurality of antenna elements, the base station apparatus and the communication The terminal device generates a codeword as a unit of processing of the signal, divides the generated codeword into a plurality of layers, maps and performs transmission / reception of the signal, and divides the codeword into a plurality of layers In this case, the number of layers into which the codeword is divided is determined based on the average communication quality of the beams output from the antenna elements.

  According to the communication system of the present invention, the communication system includes the base station device and the communication terminal device. The base station apparatus and the communication terminal apparatus transmit and receive signals using a multi-element antenna composed of a plurality of antenna elements. A code word is generated as a signal processing unit by the base station apparatus and the communication terminal apparatus, and the generated code word is divided into a plurality of layers and mapped, thereby transmitting and receiving signals. The number of layers into which the codeword is divided is determined based on the communication quality of the beam output from each antenna element. As a result, the codeword can be divided into layers so as to have a communicable level, so that throughput can be improved. Therefore, it is possible to realize a communication system capable of performing communication with relatively high communication quality and throughput by using a multi-element antenna including a plurality of antenna elements.

FIG. 2 is an explanatory diagram showing a configuration of a radio frame used in an LTE communication system. 1 is a block diagram showing an overall configuration of an LTE communication system 200 discussed in 3GPP. FIG. It is a block diagram which shows the structure of the mobile terminal 202 shown in FIG. 2 which is a communication terminal which concerns on this invention. It is a block diagram which shows the structure of the base station 203 shown in FIG. 2 which is a base station which concerns on this invention. It is a block diagram which shows the structure of MME which concerns on this invention. 3 is a flowchart illustrating an outline from a cell search to a standby operation performed by a communication terminal (UE) in an LTE communication system. It is a figure which shows the concept of a structure of a cell in case macro eNB and small eNB coexist. 3 is a block diagram illustrating a configuration of a signal processing unit of a base station apparatus in the communication system according to Embodiment 1. FIG. 3 is a block diagram illustrating a configuration of a signal processing unit of a base station apparatus in the communication system according to Embodiment 1. FIG. It is a figure which shows an example of a multi-element antenna. It is a figure which shows an example of the relationship between the frequency at the time of allocating a chirp signal to an OFDM signal, and time. It is a figure which shows an example of the relationship between the frequency at the time of putting null and time. It is a figure which shows the other example of the relationship between the frequency at the time of putting null and time. It is a figure which shows an example of the relationship between the frequency and time when it replaces with transmitting a PDSCH in the sub-frame of a specific time, and transmits the same signal as CRS as all the data. It is a figure which shows an example of a structure of a half sub-frame (HSF) when transmitting and transmitting a known signal with a downstream signal.

Embodiment 1 FIG.
FIG. 2 is a block diagram showing an overall configuration of an LTE communication system 200 discussed in 3GPP. With reference to FIG. The radio access network is referred to as E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 201. A mobile terminal device (hereinafter referred to as “user equipment (UE)”) 202 which is a communication terminal device is capable of wireless communication with a base station device (hereinafter referred to as “base station (E-UTRAN NodeB: eNB)”) 203. Yes, signals are transmitted and received by wireless communication.

  Here, the “communication terminal device” includes not only a mobile terminal device such as a movable mobile phone terminal device but also a non-moving device such as a sensor. In the following description, the “communication terminal device” may be simply referred to as “communication terminal”.

  Control protocols for the mobile terminal 202 such as RRC (Radio Resource Control) and user planes such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), PHY (Physical layer) If terminated at station 203, the E-UTRAN is composed of one or more base stations 203.

  A control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs broadcast, paging, RRC connection management, and the like. As states of the base station 203 and the mobile terminal 202 in RRC, there are RRC_IDLE and RRC_CONNECTED.

  In RRC_IDLE, PLMN (Public Land Mobile Network) selection, system information (System Information: SI) notification, paging, cell re-selection, mobility, and the like are performed. In RRC_CONNECTED, the mobile terminal has an RRC connection and can send and receive data to and from the network. In RRC_CONNECTED, handover (Handover: HO), measurement of neighbor cells (measurement), and the like are performed.

  The base station 203 is classified into an eNB 207 and a Home-eNB 206. The communication system 200 includes an eNB group 203-1 including a plurality of eNBs 207 and a Home-eNB group 203-2 including a plurality of Home-eNBs 206. A system composed of EPC (Evolved Packet Core) that is a core network and E-UTRAN 201 that is a radio access network is referred to as EPS (Evolved Packet System). The EPC that is the core network and the E-UTRAN 201 that is the radio access network may be collectively referred to as a “network”.

  The eNB 207 includes a mobility management entity (MME), an S-GW (Serving Gateway), or an MME / S-GW unit including the MME and S-GW (hereinafter also referred to as “MME unit”) 204. The control information is communicated between the eNB 207 and the MME unit 204 through the S1 interface. A plurality of MME units 204 may be connected to one eNB 207. The eNBs 207 are connected by the X2 interface, and control information is communicated between the eNBs 207.

  The Home-eNB 206 is connected to the MME unit 204 via the S1 interface, and control information is communicated between the Home-eNB 206 and the MME unit 204. A plurality of Home-eNBs 206 are connected to one MME unit 204. Alternatively, the Home-eNB 206 is connected to the MME unit 204 via a HeNBGW (Home-eNB GateWay) 205. Home-eNB 206 and HeNBGW 205 are connected via an S1 interface, and HeNBGW 205 and MME unit 204 are connected via an S1 interface.

  One or a plurality of Home-eNBs 206 are connected to one HeNBGW 205, and information is communicated through the S1 interface. The HeNBGW 205 is connected to one or a plurality of MME units 204, and information is communicated through the S1 interface.

  The MME unit 204 and the HeNBGW 205 are higher-level devices, specifically higher-level nodes, and control the connection between the eNB 207 and the Home-eNB 206, which are base stations, and the mobile terminal (UE) 202. The MME unit 204 constitutes an EPC that is a core network. The base station 203 and the HeNBGW 205 constitute an E-UTRAN 201.

  Further, 3GPP is considering the following configuration. The X2 interface between Home-eNB 206 is supported. That is, the Home-eNB 206 is connected by the X2 interface, and control information is communicated between the Home-eNB 206. From the MME unit 204, the HeNBGW 205 appears as a Home-eNB 206. From the Home-eNB 206, the HeNBGW 205 appears as the MME unit 204.

  In any case where the Home-eNB 206 is connected to the MME unit 204 via the HeNBGW 205 or directly connected to the MME unit 204, the interface between the Home-eNB 206 and the MME unit 204 is an S1 interface. The same.

  The base station 203 may constitute one cell or a plurality of cells. Each cell has a predetermined range as a coverage that is a range in which communication with the mobile terminal 202 is possible, and performs wireless communication with the mobile terminal 202 within the coverage. When one base station 203 forms a plurality of cells, each cell is configured to be able to communicate with the mobile terminal 202.

  FIG. 3 is a block diagram showing the configuration of the mobile terminal 202 shown in FIG. 2 which is a communication terminal according to the present invention. The transmission process of the mobile terminal 202 shown in FIG. 3 will be described. First, control data from the protocol processing unit 301 and user data from the application unit 302 are stored in the transmission data buffer unit 303. The data stored in the transmission data buffer unit 303 is transferred to the encoder unit 304 and subjected to encoding processing such as error correction. There may exist data that is directly output from the transmission data buffer unit 303 to the modulation unit 305 without performing the encoding process. The data encoded by the encoder unit 304 is modulated by the modulation unit 305. The modulated data is converted into a baseband signal, and then output to the frequency conversion unit 306, where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 307 to the base station 203.

  Moreover, the reception process of the mobile terminal 202 is performed as follows. A radio signal from the base station 203 is received by the antenna 307. The received signal is converted from a radio reception frequency to a baseband signal by the frequency converter 306, and demodulated by the demodulator 308. The demodulated data is transferred to the decoder unit 309 and subjected to decoding processing such as error correction. Of the decoded data, control data is passed to the protocol processing unit 301, and user data is passed to the application unit 302. A series of processing of the mobile terminal 202 is controlled by the control unit 310. Therefore, the control unit 310 is connected to the respective units 301 to 309, which are omitted in FIG.

  FIG. 4 is a block diagram showing a configuration of the base station 203 shown in FIG. 2, which is a base station according to the present invention. The transmission process of the base station 203 shown in FIG. 4 will be described. The EPC communication unit 401 transmits and receives data between the base station 203 and the EPC (such as the MME unit 204) and the HeNBGW 205. The other base station communication unit 402 transmits / receives data to / from other base stations. The EPC communication unit 401 and the other base station communication unit 402 exchange information with the protocol processing unit 403, respectively. Control data from the protocol processing unit 403 and user data and control data from the EPC communication unit 401 and the other base station communication unit 402 are stored in the transmission data buffer unit 404.

  Data stored in the transmission data buffer unit 404 is transferred to the encoder unit 405 and subjected to encoding processing such as error correction. There may exist data directly output from the transmission data buffer unit 404 to the modulation unit 406 without performing the encoding process. The encoded data is subjected to modulation processing by the modulation unit 406. The modulated data is converted into a baseband signal and then output to the frequency conversion unit 407 where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 408 to one or a plurality of mobile terminals 202.

  Further, the reception process of the base station 203 is executed as follows. Radio signals from one or more mobile terminals 202 are received by an antenna 408. The received signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulated by the demodulation unit 409. The demodulated data is transferred to the decoder unit 410 and subjected to decoding processing such as error correction. Of the decoded data, control data is passed to the protocol processing unit 403 or EPC communication unit 401 and other base station communication unit 402, and user data is passed to the EPC communication unit 401 and other base station communication unit 402. A series of processing of the base station 203 is controlled by the control unit 411. Therefore, the control unit 411 is connected to the respective units 401 to 410, which are omitted in FIG.

  FIG. 5 is a block diagram showing the configuration of the MME according to the present invention. FIG. 5 shows the configuration of the MME 204a included in the MME unit 204 shown in FIG. The PDN GW communication unit 501 performs data transmission / reception between the MME 204a and the PDN GW. The base station communication unit 502 performs data transmission / reception between the MME 204a and the base station 203 using the S1 interface. If the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 501 to the base station communication unit 502 via the user plane communication unit 503 and to one or more base stations 203. Sent. When the data received from the base station 203 is user data, the user data is transferred from the base station communication unit 502 to the PDN GW communication unit 501 via the user plane communication unit 503 and transmitted to the PDN GW.

  When the data received from the PDN GW is control data, the control data is transferred from the PDN GW communication unit 501 to the control plane control unit 505. When the data received from the base station 203 is control data, the control data is transferred from the base station communication unit 502 to the control plane control unit 505.

  The HeNBGW communication unit 504 is provided when the HeNBGW 205 exists, and performs data transmission / reception through an interface (IF) between the MME 204a and the HeNBGW 205 depending on the information type. The control data received from the HeNBGW communication unit 504 is passed from the HeNBGW communication unit 504 to the control plane control unit 505. The result of the processing in the control plane control unit 505 is transmitted to the PDN GW via the PDN GW communication unit 501. In addition, the result processed by the control plane control unit 505 is transmitted to one or more base stations 203 via the S1 interface via the base station communication unit 502, and to one or more HeNBGWs 205 via the HeNBGW communication unit 504. Sent.

  The control plane control unit 505 includes a NAS security unit 505-1, an SAE bearer control unit 505-2, an idle state mobility management unit 505-3, and the like, and performs overall processing for the control plane. The NAS security unit 505-1 performs security of a NAS (Non-Access Stratum) message. The SAE bearer control unit 505-2 performs management of SAE (System Architecture Evolution) bearers and the like. The idle state mobility management unit 505-3 performs mobility management in a standby state (Idle State; also referred to as LTE-IDLE state or simply idle), generation and control of a paging signal in the standby state, The tracking area of one or a plurality of mobile terminals 202 is added, deleted, updated, searched, and tracking area list is managed.

  The MME 204a distributes the paging signal to one or a plurality of base stations 203. In addition, the MME 204a performs mobility control (Mobility control) in a standby state (Idle State). The MME 204a manages a tracking area list when the mobile terminal is in a standby state and in an active state (Active State). The MME 204a starts a paging protocol by transmitting a paging message to a cell belonging to a tracking area (tracking area) in which the UE is registered. The idle state mobility management unit 505-3 may perform CSG management, CSG-ID management, and white list management of the Home-eNB 206 connected to the MME 204a.

  Next, an example of a cell search method in the communication system is shown. FIG. 6 is a flowchart illustrating an outline from a cell search to a standby operation performed by a communication terminal (UE) in an LTE communication system. When the communication terminal starts the cell search, in step ST601, the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from the neighboring base stations are used to generate the slot timing, the frame, Synchronize timing.

  The P-SS and S-SS are collectively referred to as a synchronization signal (SS). In the synchronization signal (SS), a synchronization code corresponding to one-to-one is assigned to the PCI assigned to each cell. As for the number of PCIs, 504 patterns are under consideration. Synchronization is performed using the 504 PCIs, and the PCI of the synchronized cell is detected (specified).

  Next, in step ST602, a cell-specific reference signal (CRS) that is a reference signal (reference signal: RS) transmitted from the base station to each cell is detected for the synchronized cell. Measure the RS Received Power (Reference Signal Received Power: RSRP). For the reference signal (RS), a code corresponding to PCI one to one is used. By correlating with that code, it can be separated from other cells. By deriving the RS code of the cell from the PCI specified in step ST1, it becomes possible to detect the RS and measure the received power of the RS.

  Next, in step ST603, the cell with the best RS reception quality, for example, the cell with the highest RS reception power, that is, the best cell is selected from one or more cells detected up to step ST602.

  Next, in step ST604, PBCH of the best cell is received, and BCCH that is broadcast information is obtained. A MIB (Master Information Block) including cell configuration information is mapped to the BCCH on the PBCH. Therefore, the MIB is obtained by receiving the PBCH and obtaining the BCCH. The MIB information includes, for example, DL (downlink) system bandwidth (also called transmission bandwidth configuration (dl-bandwidth)), the number of transmission antennas, SFN (System Frame Number), and the like.

  Next, in step ST605, DL-SCH of the cell is received based on the MIB cell configuration information, and SIB (System Information Block) 1 in broadcast information BCCH is obtained. SIB1 includes information related to access to the cell, information related to cell selection, and scheduling information of other SIBs (SIBk; an integer of k ≧ 2). The SIB1 includes a tracking area code (TAC).

  Next, in step ST606, the communication terminal compares the TAC of SIB1 received in step ST605 with the TAC part of the tracking area identifier (Tracking Area Identity: TAI) in the tracking area list already held by the communication terminal. . The tracking area list is also referred to as a TAI list. The TAI is identification information for identifying a tracking area, and includes a mobile country code (MCC), a mobile network code (MNC), and a tracking area code (TAC). MCC is a country code. MNC is a network code. TAC is the code number of the tracking area.

  As a result of the comparison in step ST606, if the TAC received in step ST605 is the same as the TAC included in the tracking area list, the communication terminal enters a standby operation in the cell. In comparison, if the TAC received in step ST605 is not included in the tracking area list, the communication terminal transmits a TAU (Tracking Area Update) to the core network (Core Network, EPC) including the MME and the like through the cell. Request tracking area change to do

  A device constituting the core network (hereinafter sometimes referred to as “core network side device”) performs tracking based on the identification number (UE-ID or the like) of the communication terminal sent from the communication terminal together with the TAU request signal. Update the area list. The core network side device transmits the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) the TAC list held by the communication terminal based on the received tracking area list. Thereafter, the communication terminal enters a standby operation in the cell.

  With the widespread use of smartphones and tablet-type terminal devices, traffic due to cellular wireless communication has increased explosively, and there is a concern about the shortage of wireless resources around the world. Correspondingly, in order to increase the frequency utilization efficiency, it has been studied to reduce the cell size and advance the spatial separation.

  In the conventional cell configuration, a cell configured by an eNB has a relatively wide range of coverage. Conventionally, a cell is configured to cover a certain area with a relatively wide range of coverage of a plurality of cells configured by a plurality of eNBs.

  When the cell size is reduced, the cell configured by the eNB has a coverage that is narrower than the coverage of the cell configured by the conventional eNB. Therefore, in the same way as in the past, in order to cover a certain area, a larger number of eNBs having a smaller cell size are required as compared with the conventional eNB.

  In the following description, a cell having a relatively large coverage, such as a cell configured by a conventional eNB, is referred to as a “macro cell”, and an eNB configuring the macro cell is referred to as a “macro eNB”. In addition, a cell having a relatively small coverage, such as a small cell, is referred to as a “small cell”, and an eNB configuring the small cell is referred to as a “small eNB”.

  The macro eNB may be, for example, a “Wide Area Base Station” described in Non-Patent Document 8.

  The small eNB may be, for example, a low power node, a local area node, a hot spot, or the like. The small eNB is a pico eNB constituting a pico cell, a femto eNB constituting a femto cell, a HeNB, an RRH (Remote Radio Head), an RRU (Remote Radio Unit), an RRE (Remote Radio Equipment), or an RN (Relay Node). There may be. Further, the small eNB may be a “Local Area Base Station” or “Home Base Station” described in Non-Patent Document 8.

  FIG. 7 is a diagram illustrating a concept of a cell configuration when a macro eNB and a small eNB coexist. A macro cell configured by a macro eNB has a relatively wide range of coverage 701. A small cell configured by a small eNB has a coverage 702 having a smaller range than a coverage 701 of a macro eNB (macro cell).

  When a plurality of eNBs coexist, the coverage of a cell configured by a certain eNB may be included in the coverage of a cell configured by another eNB. In the cell configuration shown in FIG. 7, as indicated by reference numerals “704” or “705”, the small cell coverage 702 configured by the small eNB is included in the macro cell coverage 701 configured by the macro eNB. May be.

  In addition, as indicated by reference numeral “705”, a plurality of, for example, two small cell coverages 702 may be included in one macro cell coverage 701. A mobile terminal (UE) 703 is included in, for example, a small cell coverage 702 and performs communication via the small cell.

  Further, in the cell configuration illustrated in FIG. 7, as indicated by the reference numeral “706”, the macro cell coverage 701 configured by the macro eNB and the small cell coverage 702 configured by the small eNB overlap in a complicated manner. Cases arise.

  Also, as indicated by reference numeral “707”, there may be a case where the coverage 701 of the macro cell configured by the macro eNB does not overlap with the coverage 702 of the small cell configured by the small eNB.

  Furthermore, as indicated by reference numeral “708”, a plurality of small cell coverages 702 configured by a plurality of small eNBs are configured in one macro cell coverage 701 configured by one macro eNB. Sometimes it happens.

  In the above configuration, when using a multi-element antenna required in the fifth generation mobile communication system, there are the following two problems (1) and (2).

  (1) Single user-multiple input multiple output (abbreviation: SU-MIMO) that transmits and receives different data with a plurality of antennas to one communication terminal or eNB to improve user throughput. Technology is known. However, when performing SU-MIMO, in the case of a line of sight (abbreviation: LOS) among multipaths that appear to be reflected or diffracted, the received power of the main wave and the signal to noise ratio (Signal to Noise Ratio). ; Abbreviation: SNR) is large, the level of other multipaths is low, and the throughput is not increased.

  (2) In the current 3GPP, the number of layers (corresponding to a beam formed by each antenna element in the case of a multi-element antenna) that can divide a codeword that is one block for error correction is limited And cannot be transmitted in other layers (beams). In addition, codewords are assigned an equal number to each layer. For example, in downlink, when the number of layers (hereinafter sometimes referred to as “number of layers”) is 4, there are up to two layers per codeword (Non-Patent Document 2, Table 6.3.3.2). -1). Here, the code word is a processing unit for processing a signal.

  In the present embodiment, a method is disclosed in which one codeword can be freely divided into a plurality of layers and transmitted. 8 and 9 are block diagrams illustrating the configuration of the signal processing unit of the base station apparatus in the communication system according to the first embodiment. FIG. 8 is a block diagram showing a configuration of a part (hereinafter also referred to as “codeword generation unit”) that generates a codeword in the preceding stage of the signal processing unit.

  The codeword generation unit constituting the front stage of the signal processing unit of the base station apparatus includes a transport block (abbreviation: TB) CRC adding unit 801, a code block (code brock: abbreviation: CB) division / CB CRC adding unit 802, a channel coding unit 803, a rate matching unit 804, and a CB concatenation unit 805.

  The TB CRC adding unit 801 assigns a CRC (Cyclic Redundancy Check) to a transport block input from a MAC layer (not shown). The TB CRC giving unit 801 gives the transport block to which the CRC is given to the CB division / CB CRC giving unit 802.

  The CB division / CB CRC assigning unit 802 divides the transport block given from the TB CRC assigning unit 801 into units called code blocks and assigns CRC to each code block. The CB division / CB CRC adding unit 802 gives the code block to which the CRC is added to the channel coding unit 803.

  The channel coding unit 803 performs channel coding processing such as turbo coding or convolutional coding on the code block given from the CB division / CB CRC adding unit 802. Channel coding section 803 gives the code block subjected to the channel coding processing to rate matching section 804.

  The rate matching unit 804 performs rate matching processing on the code block given from the channel coding unit 803 and adjusts the code block to the number of transmission bits of the radio frame. The rate matching unit 804 gives the code block subjected to the rate matching process to the CB concatenation unit 805.

  The CB concatenation unit 805 concatenates code blocks given from the rate matching unit 804.

  Data in units called codewords is generated by the processing by the TB CRC adding unit 801, the CB division / CB CRC adding unit 802, the channel coding unit 803, the rate matching unit 804, and the CB concatenating unit 805.

  It is determined how many layers the generated codeword is divided based on the communication quality for each beam of the known sequence signal measured by the communication terminal or the eNB. Here, the known sequence signal may be known to the communication terminal or eNB. The known sequence signal is, for example, a cell-specific reference signal (CRS) in the case of downlink, a channel state information reference signal (CSI-RS) for each antenna element, an MBSFN reference signal ( MBSFN Reference Signal) or UE-specific Reference Signal. The known sequence signal is, for example, a data demodulation reference signal (DM-RS) or a sounding signal in the case of uplink. The communication quality of each beam is represented by, for example, the SNR calculated as noise corresponding to the deviation of the known series signal from the ideal signal.

  FIG. 9 is a block diagram showing a configuration of a part for processing a code word in the subsequent stage of the signal processing unit (hereinafter also referred to as “code word processing unit”). The codeword processing unit constituting the subsequent stage of the signal processing unit of the base station apparatus includes a scrambling unit 811, a modulation mapping unit 812, a layer mapping unit 813, a precoding unit 814, a resource element mapping unit 815, and an OFDM signal generation unit 816. It is configured with.

  FIG. 9 shows an example when it is determined that the generated codeword is transmitted in six layers. Therefore, six resource element mapping units 815 and six OFDM signal generation units 816 are provided.

  The code word generated as described above is given to the scrambling unit 811. The scrambling unit 811 scrambles the given code word. The scrambling unit 811 gives the scrambled codeword to the modulation mapping unit 812.

  The modulation mapping unit 812 maps the codeword given from the scrambling unit 811 to the modulation format. The modulation mapping unit 812 gives the code word mapped to the modulation format to the layer mapping unit 813.

  The layer mapping unit 813 divides the codeword given from the modulation mapping unit 812 into a plurality of layers, specifically six layers, and maps the codewords to each layer. The layer mapping unit 813 gives the codeword mapped to each layer to the precoding unit 814.

  The precoding unit 814 performs precoding of the codeword given from the layer mapping unit 813. The precoding unit 814 gives the precoded codeword to each resource element mapping unit 815.

  Each resource element mapping unit 815 assigns the codeword given from the precoding unit 814 to the frequency / time resource. Each resource element mapping unit 815 gives the codeword assigned to the frequency / time resource to the corresponding OFDM signal generation unit 816.

  Each OFDM signal generation unit 816 performs OFDM processing on the codeword given from the resource element mapping unit 815 to generate an OFDM signal. Each OFDM signal generation unit 816 gives the generated OFDM signal to a corresponding antenna element among a plurality of antenna elements constituting the multi-element antenna.

  For example, when the SNR of the layer 1 beam is 23 dB and the SNR of the layer 2 to layer 6 beams is 9 dB, the average SNR is 16 dB, and six layers communicate with 16 QAM (Quadrature Amplitude Modulation). It becomes possible level and throughput is improved.

  Thus, in the present embodiment, the number of layers into which the codeword is divided is determined based on the communication quality of the beam output from each antenna element. As a result, the codeword can be divided into layers so as to have a communicable level, so that throughput can be improved. Therefore, it is possible to realize a communication system capable of performing communication with relatively high communication quality and throughput by using a multi-element antenna including a plurality of antenna elements.

  Moreover, in this Embodiment, the communication quality of the beam output from each antenna element is measured using the known series signal of each beam by eNB which is a base station apparatus, or a communication terminal. Thereby, the communication quality of each beam can be easily measured.

  As described above, in the present embodiment, the communication terminal or eNB measures the communication quality using the known sequence signal of each beam, and shows the configuration for transmitting the measured value to the opposite eNB or communication terminal. However, it is not limited to such a configuration.

  For example, the measured communication quality may be represented by an index provided in multiple stages. By expressing the communication quality with an index provided in multiple stages, the amount of information transmitted and received between the communication terminal and the eNB can be reduced.

  The communication quality index is divided into, for example, eight stages as follows. The first stage is less than 0 dB, the second stage is from 0 dB to less than 4 dB, the third stage is from 4 dB to less than 8 dB, the fourth stage is from 8 dB to less than 12 dB, the fifth stage is from 12 dB to less than 16 dB, and the sixth stage is from 16 dB to less than 20 dB. Less than, the seventh stage is 20 dB or more and less than 24 dB, and the eighth stage is 24 dB or more.

  The communication quality transmitted to the communication terminal may be a value for each beam, an average value of all the beams, or both. When the value for each beam is transmitted, the transmission data amount can be determined with high accuracy. When the average value of all the beams is transmitted, the calculation in the opposite device can be omitted.

  Also, identification information such as a beam ID (Identifier) may be transmitted, for example, information that identifies an average value of all beams and a beam having communication quality equal to or higher than a predetermined threshold. Thereby, the information amount transmitted / received between a communication terminal and eNB can be reduced.

  Further, instead of the communication quality measured by the communication terminal or eNB using the known sequence signal of each beam, the communication terminal or eNB may transmit the number of data bits that can be received for each beam, or may be received by all the beams. The total number of data bits that can be transmitted may be transmitted. Further, information for identifying a beam having a communication quality equal to or higher than a predetermined threshold and a total value of all beams, for example, identification information such as a beam ID may be transmitted.

  In the case of Time Division Duplex (abbreviation: TDD), the communication quality may be measured using the received signal in the opposite device.

  Another example of the method for dividing the code word is shown below. In the case of downlink, the generated codeword includes the communication quality of each beam measured by a communication terminal using a known sequence signal, for example, a cell-specific reference signal (CRS), and other communication terminals. The number of layers is determined based on the communication status. In addition to this, it is determined how much data is transmitted, specifically, any one of modulation schemes such as QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64 QAM.

  For example, when the SNR of the beam of layer 1 is 23 dB and the SNR of the beams of layer 2 to layer 6 is 9 dB, the average SNR is 16 dB, and six layers can communicate with 16 QAM. If a specific communication terminal uses all of Layer 1 to Layer 6, it may be necessary to wait for the transmission of many users at Layers 5 and 6. Even in such a case, if data transmission for 50% of the other layers is possible in layers 5 and 6, it is effective because it is not necessary to wait for user transmission.

  As described above, when dividing the data amount for each layer, it is possible to divide the data amount into any one of 100%, 75%, 50%, 25%, or 100%, 50%. By limiting the possible steps, processing such as rate matching may be simplified. As a result, when it is necessary to notify information relating to the amount of data transmitted this time as control information to the communication terminal, the number of bits of the information can be reduced.

  The communication status with other communication terminals may be whether or not the buffer amount of the transmission waiting buffer for the other communication terminals in the beam has reached a specific amount. For example, an appropriate threshold value and an emergency response threshold value are provided for buffer management for each beam. If it is below the appropriate threshold, no special processing such as data transmission is performed immediately. If the emergency response threshold is exceeded, data is transmitted immediately. When the emergency response threshold is exceeded, the data transmission amount for the SU-MIMO communication that can be transmitted by other beams is set to 50% of the equal division. When buffer overflow occurs, the data transmission amount is set to 0%.

  The communication status with other communication terminals may be the presence or absence of a communication terminal whose transmission waiting time in the beam exceeds a specific threshold, or the number of communication terminals. This threshold value is, for example, a timer value corresponding to a processing delay (latency) allowable time set for each bearer. The threshold may be notified from the communication terminal by an RRC, for example, an RRC connection setup message, an RRC connection reconfiguration message, or a separate message.

  The communication status with other communication terminals may be, for example, a timer value set as an allowable processing delay time when setting the link of the S1 interface and the X2 interface. When there is a communication terminal whose transmission waiting time in the beam exceeds a specific threshold, the amount of data communication for SU-MIMO communication that can be transmitted by another beam is not transmitted as an equally divided data amount to all layers. The following may be used. For example, 75%, 50%, 25%, and 0% may be selected and transmitted so that the amount of data whose transmission waiting time exceeds a specific threshold can be transmitted simultaneously.

  Still another example of the method for dividing the codeword will be described below. When the generated codeword is divided into several layers, both vertical polarization V and horizontal polarization H are used in the case of MIMO communication in which different data is transmitted between vertical polarization V and horizontal polarization H. . When both the eNB and the communication terminal transmit the vertical polarization V and the horizontal polarization H by the same antenna, the communication quality of each beam is not reported, but either the vertical polarization V or the horizontal polarization H is reported. The communication quality may be reported.

  In this way, when reporting the communication quality of either the vertical polarization V or the horizontal polarization H, the eNB or the communication terminal transmits the vertical polarization V transmitted from the same antenna that can be set when using the polarization. RRC connection setup / RRC connection reconfiguration message indicating whether or not there is horizontal polarization H and which is a set, RRC connection setup (RRC Connection Setup) or RRC connection reconfiguration (RRC Connection Reconfiguration), It may be notified in a RRC connection setup / RRC connection reconfiguration completion message indicating RRC connection setup or RRC connection reconfiguration complete, or a separate message. Specifically, a parameter may be added to “AntennaInfo” of the message.

  Further, even when vertical polarization and V horizontal polarization H are transmitted using the same antenna, it is possible to transmit with different directivities. Therefore, a set of vertical polarization V and horizontal polarization H is transmitted in the same direction every time using DCI (DL Control Information) of PDCCH for downlink and UCI (UL Control Information) of PUCCH for uplink. You may be notified if it is. As a result, when the vertical polarization V and the horizontal polarization H have the same directivity, either the vertical polarization V or the horizontal polarization H can be reported.

  In the case of notifying information indicating a set, that is, transmission of vertical polarization V and horizontal polarization H by the same antenna, in order to reduce the bits of information specifying the set, an ID for identifying the beam is an even number, for example It is better to divide it like odd numbers. For example, if beam ID is set to 0 and beam ID is set to 1, beam ID is set to 2 and beam ID is set to 3, beam ID is set to 4 and beam ID is set to 5, and so on. Good.

Embodiment 2. FIG.
There are the following two problems (1) and (2) in order to improve the throughput of the multi-element antenna required for the fifth generation mobile communication.

  (1) If the phase difference and amplitude difference between the antenna elements are not matched, (a) the beam directivity cannot be controlled in the desired direction, (b) Equivalent Isotropic Radiated Power (abbreviation) : EIRP) and the like, and (c) sidelobe power increases and interference with other users increases.

  (2) The phase difference and amplitude difference between the antenna elements need to eliminate variations in temperature change and secular change. However, since broadband communication is performed and the frequency bandwidth is increased, there is a problem that the amount of change due to temperature change and secular change is greatly affected by amplifiers and filters.

  In the present embodiment, a method for accurately performing calibration for matching a phase difference and an amplitude difference between antenna elements of a multi-element antenna is disclosed.

  Self-calibration is one of the known methods for calibrating multi-element antennas, and is a method for performing calibration using its own antenna elements without providing a special antenna. By performing self-calibration, a physically remote device is not required. For example, the communication terminal is unnecessary when the eNB is calibrated, and the eNB is unnecessary when the communication terminal is calibrated. Therefore, since self-calibration can be used during operation at a relatively low cost, it has been studied as a method applicable to temperature changes and aging changes.

  FIG. 10 is a diagram illustrating an example of a multi-element antenna. FIG. 10 shows a multi-element antenna in which 64 antenna elements are mounted on the same plane as an example. As shown in FIG. 10, in a multi-element antenna in which a plurality of antenna elements are mounted on the same plane, the directivity of each antenna element is not oriented in the horizontal direction. Therefore, when transmitting from one antenna element 901 and receiving by another antenna element 902, there is a problem that the SNR becomes low and the calibration accuracy does not increase.

  As a first method for improving the SNR, a method of transmitting a known signal by reducing the time and frequency resources of the PDSCH will be disclosed below.

  Each of the eNB and the communication terminal notifies the opposite device of activation of the calibration mode. In other words, the start of the calibration mode is notified to the communication terminal if it is an eNB, and to the eNB if it is a communication terminal.

  Notification of activation of the calibration mode is, for example, an RRC connection setup / RRC connection reconfiguration message, or an RRC connection setup / RRC connection reconfiguration completion (RRC connection). Reconfiguration Complete) message is used to specify the calibration mode during operation.

  As one of the calibration modes, there is a calibration mode of “adjusting coding parameters to reduce the number of PDSCH transmission bits and transmitting a known signal instead”. By specifying this calibration mode, the total number of bits that can be transmitted in one transport block in the rate matching described in Chapter 5.1.4 of Non-Patent Document 9 is G, and it is spread across beams like diversity. When the number of beams when transmitting the same data is NL and the order of multilevel modulation is Qm (Qm = 2: QPSK, Qm = 4: 16QAM, Qm = 6: 64QAM, Qm = 8: 256QAM), G Symbols having a value of / (NL × Qm) are reduced.

  The eNB or the communication terminal that has received the signal with the G / (NL × Qm) value reduced symbol assigns known data to the reduced symbol. For example, a chirp signal is transmitted as a signal from which symbols having a value of G / (NL × Qm) are reduced. The chirp signal is a signal whose frequency continuously changes from a low frequency to a high frequency, or from a high frequency to a low frequency, and is a signal in which frequency components are uniformly transmitted to form a constant envelope. Therefore, since the chirp signal has a lower linearity requirement for the amplifier than a normally transmitted signal such as PDSCH, the transmission power can be increased, that is, boosted by transmitting the chirp signal.

  FIG. 11 is a diagram illustrating an example of the relationship between frequency and time when a chirp signal is assigned to an OFDM signal. In FIG. 11, the horizontal axis represents frequency f, and the vertical axis represents time t. Each square in FIG. 11 represents a subcarrier of a certain OFDM signal. An OFDM symbol can be assigned to the corresponding frequency and time cell. For example, a reference signal (abbreviation: RS) is assigned to a location indicated by reference numeral “1002”.

  In addition, a chirp signal is allocated to a portion surrounded by a broken line denoted by reference numeral “1001”. An example is shown in which all data transmitted in this time zone becomes a chirp signal for calibration. In this case, the opposite apparatus does not have to perform the reception process at the time indicated by the reference symbol “1001”.

  Further, if the frequency is divided into several parts and transmitted by different single antenna elements, calibration can be efficiently performed. It is also effective to insert a null in accordance with the filter on the receiving side. FIG. 12 is a diagram illustrating an example of the relationship between frequency and time when a null is interposed. In FIG. 12, the horizontal axis represents the frequency f, and the vertical axis represents the time t. In the example shown in FIG. 12, a reference signal (RS) is assigned to a location indicated by reference numeral “1002”, for example, as in the example shown in FIG.

  A hatched portion with a downward slanting line indicated by reference numeral “1101” indicates time and frequency transmitted from the first antenna element. The hatched portion of the lower left diagonal line indicated by reference numeral “1102” indicates the time and frequency transmitted from the second antenna element.

  In the example shown in FIG. 12, a dashed line with a lower right side denoted by reference numeral “1103” so that a signal transmitted from the first antenna element and a signal transmitted from the second antenna element can be separated by a filter. A null signal with an amplitude of zero (0) is assigned to the hatched portion.

  FIG. 13 is a diagram illustrating another example of the relationship between frequency and time when a null is interposed. In FIG. 13, the horizontal axis represents the frequency f, and the vertical axis represents the time t. In the example illustrated in FIG. 13, as in the example illustrated in FIG. 11, for example, a reference signal (RS) is allocated to a location indicated by reference numeral “1002”.

  A hatched portion with a downward slanting line indicated by reference numeral “1201” indicates a time and frequency transmitted from the first antenna element. A hatched portion with a left-downward slanting line indicated by reference numeral “1202” indicates a time and frequency transmitted from the second antenna element. A null signal having an amplitude of zero (0) is assigned to a hatched portion indicated by a reference sign “1203” with a downward slanting dashed line.

  In order to further improve the SNR, a plurality of symbols may be allocated in the time (t) direction as indicated by reference numerals “1201”, “1202”, and “1203” in FIG. In this case, the chirp signal may not be a repeated signal for each OFDM symbol, but may be continuous and uniform for 3 symbols as shown in FIG.

  The eNB or communication terminal sequentially switches its own station transmitting element, which is an antenna element used for transmission in its own device, and sequentially switches its own station receiving element, which is an antenna element used for reception, in its own device. The phase difference and the amplitude difference between the antenna elements can be measured.

  Moreover, eNB or a communication terminal may measure the phase difference and amplitude difference between antenna elements for every temperature beforehand, and may memorize | store it in a non-volatile memory etc. Further, the eNB or the communication terminal may be equipped with a semiconductor capable of measuring temperature so that the temperature can be measured.

  With the above configuration, the eNB or the communication terminal controls the phase and amplitude of each antenna element so as to be the same as the phase difference and amplitude difference between the antenna elements measured in advance, corresponding to the temperature during operation. be able to. Thereby, the directivity and gain of the beam can be improved, so that the throughput can be improved.

  As described above, in the present embodiment, the eNB that is the base station apparatus and the communication terminal are known using the reduced symbols by reducing the number of symbols used for transmission of the physical downlink shared channel (PDSCH). Send the signal. As a result, the SNR during calibration can be improved.

  Another example of a method for improving the SNR at the time of calibration is shown below. In the example shown in FIG. 12 and FIG. 13 described above, the case where a chirp signal is transmitted is shown. However, instead of the chirp signal, CRS or CSI-RS is used for downlink, DM-RS or sounding is used for uplink. ) A method of transmitting the same signal as the known sequence signal used in the signal may be used. In this case, similar to the chirp signal, the known sequence signal may be transmitted to a part of the PDSCH.

  FIG. 14 is a diagram illustrating an example of a relationship between frequency and time when the same signal as CRS is transmitted as all data instead of transmitting PDSCH in a subframe of a specific time. In FIG. 14, the horizontal axis represents the frequency f, and the vertical axis represents the time t. In the example shown in FIG. 14, a reference signal (RS) is allocated to a location indicated by reference numeral “1002”, for example, as in the example shown in FIG.

  Instead of transmitting the PDSCH in a subframe of a specific time as described above, as shown in FIG. 14, the same signal as the CRS, for example, RS may be transmitted as all data.

  The same signal as CRS is a constant envelope. Therefore, the peak power to average power ratio (abbreviation: PAPR) of the same signal as the CRS is about 6 to 7 dB lower than the PASCH of the PDSCH. The transmission power is increased, that is, boosted accordingly. Here, PAPR represents the ratio of peak signal power to average signal power.

  For example, eNB which is a base station apparatus notifies the transmission timing information of the same signal as CRS by broadcast information such as RRC, for example, SIB. As a result, the cell search of the communication terminal can be facilitated, so that the power consumption can be reduced by increasing the sleep time interval.

  Moreover, eNB notifies the transmission timing information of the same signal as CSI-RS by RRC, for example, alerting | reporting information or a RRC connection setup (RRC Connection Setup) / RRC connection reconfiguration message. As a result, the measurement accuracy of the communication quality of each beam can be improved, so that the accuracy of precoding can be improved.

  Moreover, eNB notifies the transmission timing information of the same signal as CRS or CSI-RS by RRC. As a result, the communication terminal can receive a signal with a relatively high SNR, so that the accuracy of ranging such as AoA (Angle of Arrival) can be improved.

  The eNB or the communication terminal can measure the phase difference and the amplitude difference between the antenna elements by sequentially switching the local station transmitting elements and sequentially switching the corresponding local station receiving elements. Moreover, eNB or a communication terminal measures the phase difference and amplitude difference between antenna elements beforehand for every temperature, and memorize | stores the measured value in a non-volatile memory etc. Also, the eNB or the communication terminal is equipped with a semiconductor capable of measuring temperature so that the temperature can be measured.

  By doing as described above, the eNB or the communication terminal sets the phase and amplitude of each antenna element to be the same as the phase difference and amplitude difference between the antenna elements measured in advance corresponding to the temperature during operation. Can be controlled. Thereby, the directivity and gain of the beam can be improved, and the throughput can be improved.

  Still another example of a method for improving the SNR at the time of calibration is shown below. In the case of TDD, by using the special subframe SSF, it is possible to suppress a reduction in the number of bits that can be transmitted by transmitting a known signal.

  FIG. 15 is a diagram illustrating an example of a configuration of a half subframe (HSF) when calibration is performed by transmitting a known signal as a downlink signal. A half subframe (HSF) is a frame that is half the size of a subframe.

  A calibration known sequence signal (abbreviation: cal-TSS) is assigned to the symbol SB immediately before the gap (gap) of the special subframe SSF starts. As a result, the communication terminal does not need to receive a downlink signal transmitting a known signal, and thus can start processing for switching between uplink and downlink of TDD. Therefore, allocation can be performed without reducing the number of transmission bits of PDSCH.

  Regarding the examples of the RRC setting and completion messages described in the first embodiment and the second embodiment, the RRC setting and completion messages can be used when a known signal is stopped. .

  Each above-mentioned embodiment and its modification are only illustrations of the present invention, and each embodiment and its modification can be combined freely within the scope of the present invention. Moreover, the arbitrary components of each embodiment and its modifications can be changed or omitted as appropriate.

  801 TB CRC adding section, 802 CB division / CB CRC adding section, 803 channel coding section, 804 rate matching section, 805 CB concatenation section, 811 scrambling section, 812 modulation mapping section, 813 layer mapping section, 814 precoding section, 815 Resource element mapping unit, 816 OFDM signal generation unit.

Claims (3)

A communication system comprising a base station apparatus and a communication terminal apparatus for transmitting and receiving signals using a multi-element antenna composed of a plurality of antenna elements,
The base station device and the communication terminal device are:
A code word is generated as a unit of processing of the signal, and the generated code word is divided into a plurality of layers and mapped to perform transmission / reception of the signal,
When the codeword is divided into a plurality of layers, the number of layers into which the codeword is divided is determined based on the average communication quality of the beams output from the antenna elements.   The communication quality according to claim 1, wherein the communication quality of the beam is measured by using the known sequence signal of each beam by the base station apparatus or the communication terminal apparatus.   The base station apparatus and the communication terminal apparatus reduce the number of symbols used for transmission of a physical downlink shared channel (PDSCH), and transmit a known signal using the reduced symbols. The communication system according to claim 1 or 2.

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