WO2010122749A1 - Communication system, communication apparatus and communication method - Google Patents

Communication system, communication apparatus and communication method Download PDF

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Publication number
WO2010122749A1
WO2010122749A1 PCT/JP2010/002748 JP2010002748W WO2010122749A1 WO 2010122749 A1 WO2010122749 A1 WO 2010122749A1 JP 2010002748 W JP2010002748 W JP 2010002748W WO 2010122749 A1 WO2010122749 A1 WO 2010122749A1
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Prior art keywords
reference symbol
feedback information
transmission
base station
symbol sequence
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PCT/JP2010/002748
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French (fr)
Japanese (ja)
Inventor
示沢寿之
野上智造
山田昇平
平川功
加藤恭之
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シャープ株式会社
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Priority to JP2009-106250 priority Critical
Priority to JP2009106250 priority
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Publication of WO2010122749A1 publication Critical patent/WO2010122749A1/en

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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04JMULTIPLEX COMMUNICATION
    • H04J13/00Code division multiplex systems
    • H04J13/0007Code type
    • H04J13/0022PN, e.g. Kronecker
    • H04J13/0025M-sequences
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04JMULTIPLEX COMMUNICATION
    • H04J11/00Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J11/0023Interference mitigation or co-ordination
    • H04J11/005Interference mitigation or co-ordination of intercell interference
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/26Systems using multi-frequency codes
    • H04L27/2601Multicarrier modulation systems
    • H04L27/2602Signal structure
    • H04L27/261Details of reference signals
    • H04L27/2613Structure of the reference signals per se
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/0001Arrangements for dividing the transmission path
    • H04L5/0014Three-dimensional division
    • H04L5/0023Time-frequency-space
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0032Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0032Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
    • H04L5/0035Resource allocation in a cooperative multipoint environment
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048Allocation of pilot signals, i.e. of signals known to the receiver
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; Arrangements for supplying electrical power along data transmission lines
    • H04L25/0202Channel estimation
    • H04L25/0204Channel estimation of multiple channels
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; Arrangements for supplying electrical power along data transmission lines
    • H04L25/0202Channel estimation
    • H04L25/022Channel estimation of frequency response
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; Arrangements for supplying electrical power along data transmission lines
    • H04L25/0202Channel estimation
    • H04L25/0224Channel estimation using sounding signals
    • H04L25/0226Channel estimation using sounding signals sounding signals per se
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058Allocation criteria
    • H04L5/006Quality of the received signal, e.g. BER, SNR, water filling

Abstract

In a wireless communication system, a communication apparatus at a transmission end comprises a reference signal generating unit that generates, as reference symbols to be transmitted together with transmitted data, a sequence of reference symbols based on a pseudo noise sequence. A communication apparatus at a reception end can use the sequence of reference symbols, which were generated by the reference signal generating unit, to determine a signal reception status with the interference with the reference signal suppressed or reduced.

Description

COMMUNICATION SYSTEM, COMMUNICATION DEVICE, AND COMMUNICATION METHOD

The present invention relates to a communication system, a communication apparatus, and a communication method.
This application claims priority based on Japanese Patent Application No. 2009-106250 filed in Japan on April 24, 2009, the contents of which are incorporated herein by reference.

In mobile radio communication systems such as WCDMA, LTE (Long Term Evolution), LTE-Advanced, and WiMAX, a cellular (cell) in which a plurality of areas covered by a base station (transmitting station, transmitting device, eNodeB) are arranged in a cell (Cell) By adopting a (Cellular) configuration, the communication area can be expanded. In addition, by using different frequencies between adjacent cells or sectors, even mobile terminals (receiving station, mobile station, receiving device, UE; User Equipment) in the cell edge (cell edge) area or sector edge area, Although communication can be performed without receiving interference of transmission signals from a plurality of base station apparatuses, there has been a problem that frequency utilization efficiency is low. On the other hand, the frequency utilization efficiency can be improved by using the same frequency between adjacent cells or sectors, but it is necessary to take measures against interference to the mobile terminal in the cell edge region.
As a countermeasure against this interference, a method of reducing or suppressing interference with a mobile terminal in a cell edge region by performing inter-cell cooperative communication between neighboring cells is studied. Non-Patent Document 1 discloses a CoMP (Cooperative Multipoint) transmission system as such a system. In addition, as coordinated communication between cells, joint processing (Joint Processing) and joint transmission (Joint Transmission) that coordinately transmit the same or different data between cells, coordinated and coordinated scheduling and control between cells Scheduling (Coordinated Scheduling), beamforming (Beamforming), etc. are shown.

Also, depending on the transmission path status between the base station and the mobile terminal, the modulation scheme and coding rate (MCS; Modulation Coding Scheme), spatial multiplexing number (layer, rank), precoding weight (precoding matrix) By controlling adaptively, etc., more efficient data transmission can be realized. Non-Patent Document 2 shows a method of performing these controls.

FIG. 22 is a diagram illustrating an example in which the mobile terminal 1050 transmits the feedback information IFB to the base station 1001 using the reference signal RS transmitted from the base station 1001. In the figure, a reference signal RS is transmitted from the base station 1001 to the mobile terminal 1050, and the mobile terminal 1050 transmits feedback information IFB generated based on the reference signal RS to the base station 1001. In the case of a downlink (downlink) that performs data transmission from the base station 1001 to the mobile terminal 1050, in order to perform the above-described adaptive control, as shown in the figure, a reference signal (RS; Based on Reference Signal, pilot signal, known signal) RS, the mobile terminal 1050 estimates the transmission path condition of the downlink, and the uplink (uplink) that performs data transmission from the mobile terminal 1050 to the base station 1001 It is conceivable to transmit (feedback) the estimated transmission path condition or the like to the base station 1001.

FIG. 23 is a diagram illustrating an example of a reference signal (reference symbol) RS transmitted by the base station 1001. In the figure, the horizontal axis indicates the time direction, the vertical axis indicates the frequency direction, each square indicates a resource element, and the shaded square indicates a resource element to which the reference signal RS is mapped. When a multicarrier transmission method such as an OFDM (Orthogonal Frequency Division Multiplexing) method or an OFDMA (Orthogonal Frequency Division Multiple Access) method is used as a transmission method, the reference signal RS is: As shown in the figure, a reference signal scattered (scattered) in resource elements in the frequency direction and the time direction can be used. As information (feedback information IFB) generated based on this reference signal RS and fed back to the base station 1001, recommended transmission format information (CQI (Channel Quality Indicator), RI (Rank Indicator), PMI (Precoding Matrix Index) )) Etc. can be used.

3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Further Advancements-E-UTRA Physical Layer Aspects (Release X), January 2009, 3GPP TR 36.814 V0.3.2 (2009-01) 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures (Release 8), December 2008, 3GPP TS 36.213 V8.5.0 (2008-12)

However, in the conventional communication method, it is difficult to efficiently obtain appropriate feedback information in a communication system capable of performing cooperative communication, which is a factor that hinders improvement in transmission efficiency.

The present invention has been made in view of the above problems, and an object thereof is a communication system, a communication apparatus, and a communication method capable of efficiently obtaining appropriate feedback information in a communication system capable of performing cooperative communication. Is to provide.

[1] The present invention has been made to solve the above-described problem, and a communication system according to an aspect of the present invention generates a reference signal sequence for generating a transmission side reference symbol sequence that is a sequence of reference symbols based on a pseudo-noise sequence. A generation unit, a resource element mapping unit that maps transmission data and the transmission-side reference symbol sequence to one or a plurality of resource elements for each one or a plurality of symbols, and shows the transmission data and the transmission-side reference symbol sequence A first wireless transmission unit that generates and transmits a transmission signal of a wireless signal according to the mapping, a first wireless reception unit that receives feedback information based on a signal reception state of the reference symbol, and a mode of transmission of the transmission data A first communication device including a feedback information processing unit that controls based on the feedback information; A second radio reception unit that receives the radio signal; and a signal reception state from the first communication device is measured based on a reference symbol sequence extracted from the received radio signal, and the signal reception state is measured according to the measured signal reception state A second communication device including a feedback information generation unit that generates feedback information and a second wireless transmission unit that transmits the feedback information;
Here, the transmission mode refers to a coding rate for encoding transmission data, a modulation scheme, a spatial multiplexing number (number of layers), a precoding matrix for precoding, and mapping information for mapping.
Since this communication system uses reference symbol sequences to suppress or reduce interference from other first communication devices and uses feedback information generated based on reference symbols in which this interference is suppressed or reduced, transmission data The transmission method can be appropriately controlled.

[2] A communication system according to an aspect of the present invention is the communication system described above, and is included in a third radio reception unit that receives the transmission signal, and a despread reference symbol sequence extracted from the transmission signal. A feedback information generating unit that measures a signal reception state from the first communication device based on a reference symbol to be generated, generates feedback information according to the measured signal reception state, and a third wireless transmission unit that transmits the feedback information; A third communication device including:
In this communication system, the second communication device that despreads the reference symbol sequence before despreading and generates feedback information is the same as the third communication device that generates feedback information based on each reference symbol without despreading. Since the reference symbol is referred to, both communication apparatuses can be mixed without increasing the resource overhead due to the reference symbol.

[3] A communication system according to an aspect of the present invention is the communication system described above, and includes a plurality of the first communication devices, and resource element mapping units of the plurality of first communication devices are the same resource elements. The transmission side reference symbol sequence is mapped for each symbol.
In this communication system, since reference symbols are mapped to the same resource elements between adjacent first communication devices, the second communication device despreads the reference symbol sequence before despreading, so that the other first communication devices Interference due to the reference signal can be suppressed or reduced.

[4] A communication system according to an aspect of the present invention is the communication system described above, wherein the transmission-side reference symbol sequence generated by the reference signal generation unit is a transmission-side reference symbol sequence of another first communication device. Orthogonal to
Here, a code sequence orthogonal to each other from an orthogonal code sequence such as a Walsh code, an OVSF code, and a Hadamard code can be used as a transmission-side reference symbol sequence orthogonal to the transmission-side reference symbol sequence of another first communication apparatus. However, it is not limited to this.
In this communication system, since the orthogonal reference symbol sequence is used in the first communication device, the cross-correlation is excellent, and the second communication device despreads the reference symbol sequence before despreading from other first communication devices. The effect of suppressing or reducing interference is great.

[5] A communication system according to an aspect of the present invention is the communication system described above, and includes a plurality of the first communication devices, and the transmission side generated by a reference signal generation unit of the plurality of first communication devices. The reference symbol series are cyclically shifted from each other.
In this communication system, since the transmission side reference symbol sequence shifted cyclically between the first communication devices is used, when the second communication device despreads the reference symbol sequence before despreading, due to the autocorrelation of the sequence The effect of suppressing or reducing interference from other first communication devices can be obtained.

[6] A communication system according to an aspect of the present invention is the communication system described above, and includes a plurality of the first communication devices, and resource element mapping units of the plurality of first communication devices have different resource elements. Map the reference symbols.
In this communication system, reference symbols are mapped to resource elements that are different from each other between adjacent first communication devices. Therefore, when the second communication device despreads the reference symbol sequence before despreading, Interference due to transmission data can be suppressed or reduced.

[7] A communication apparatus according to an aspect of the present invention includes a reference signal generation unit that generates a transmission-side reference symbol sequence that is a sequence of reference symbols based on a pseudo-noise sequence, transmission data, and the transmission-side reference symbol sequence, A resource element mapping unit that maps one to a plurality of resource elements for each one or a plurality of symbols, and a radio transmission unit that generates and transmits a radio signal indicating the transmission data and the transmission side reference symbol sequence according to the mapping And a first wireless reception unit that receives feedback information based on a signal reception state of the reference symbol, and a feedback information processing unit that controls a transmission method of the transmission data based on the feedback information.
Since this communication device transmits a radio signal indicating a reference symbol sequence based on a pseudo-noise sequence, feedback information obtained by despreading this reference symbol sequence and suppressing or reducing interference from other communication devices is used. Therefore, appropriate control can be performed.

[8] A communication apparatus according to an aspect of the present invention includes a radio reception unit that receives a radio signal indicating a transmission-side reference symbol sequence via a propagation path, and a reference symbol sequence extracted from the received radio signal. A feedback information generation unit that measures a signal reception state based on the signal reception state and generates the feedback information according to the measured signal reception state, and a wireless transmission unit that transmits the feedback information.
The communication apparatus can suppress or reduce interference from a communication apparatus other than the desired communication apparatus using the reference symbol sequence, and generate more appropriate feedback information.

[9] Further, in the communication method according to one aspect of the present invention, in the communication system in which the first communication device and the second communication device perform wireless communication, the first communication device is a reference symbol sequence based on a pseudo-noise sequence. A reference signal generation process for generating a certain reference symbol sequence on the transmission side, and a resource element in which the first communication device maps transmission data and the reference symbol sequence on the transmission side to one or more resource elements for each one or more symbols A mapping process; a first radio transmission process in which the first communication apparatus generates and transmits a radio signal indicating the transmission data and the transmission-side reference symbol sequence according to the mapping; and the first communication apparatus transmits the reference symbol. A first wireless reception process of receiving feedback information based on a signal reception state of the first communication device, and the first communication device transmitting the transmission data Extracted from the feedback information processing process for controlling the transmission method based on the feedback information, the second radio reception process for the second communication apparatus to receive the radio signal, and the radio signal received by the second communication apparatus. A feedback information generation process of measuring a signal reception state from the first communication device based on a reference symbol sequence and generating the feedback information according to the measured signal reception state; and the second communication device transmits the feedback information A second wireless transmission process.
Since this communication method uses feedback information measured based on a reference symbol sequence and in accordance with a state in which interference from another first communication apparatus is suppressed or reduced, the transmission method of transmission data is appropriately controlled. be able to.

[10] In the communication method according to one aspect of the present invention, in the communication system in which the second communication device communicates with the first communication device, and the third communication device communicates with the first communication device. A reference signal generation process in which the first communication device generates a transmission-side reference symbol sequence that is a sequence of reference symbols based on a pseudo-noise sequence, and the first communication device sets transmission data and the transmission-side reference symbol sequence to 1 to 1 A resource element mapping process for mapping to one or a plurality of resource elements for each of a plurality of symbols, and the first communication apparatus generates and transmits a radio signal indicating the transmission data and the transmission side reference symbol sequence according to the mapping A first wireless transmission process, and the first communication device receives feedback information based on a signal reception state of the reference symbol. A first wireless reception process, a feedback information processing process in which the first communication device controls a transmission method of the transmission data based on the feedback information, and a second wireless reception in which the second communication device receives the wireless signal. Measuring a signal reception state from the first communication device based on a process and a reference symbol sequence extracted from the radio signal received by the second communication device, and generating the feedback information according to the measured signal reception state A feedback information generation process, a second radio transmission process in which the second communication apparatus transmits the feedback information, a third radio reception process in which the third communication apparatus receives the transmission signal, and the third communication apparatus The signal received from the first communication device is measured based on a reference symbol extracted from the transmission signal, and the measured signal A feedback information generating step of generating feedback information in accordance with signal state, the third communication device and a third wireless transmission step of transmitting the feedback information.
In this communication method, by using the reference symbol sequence, the second communication device and the third communication device can refer to the same reference symbol, and both communication devices can be mixed without increasing the resource overhead due to the reference symbol. it can.

[11] A communication method according to an aspect of the present invention includes a reference signal generation process in which a communication apparatus generates a transmission-side reference symbol sequence that is a sequence of reference symbols based on a pseudo-noise sequence, transmission data, and the transmission-side reference. A resource element mapping process for mapping a symbol sequence to one or a plurality of resource elements for each one or a plurality of symbols, and generating and transmitting a radio signal indicating the transmission data and the transmission side reference symbol sequence according to the mapping A wireless transmission process; a wireless reception process for receiving feedback information based on a signal reception state of the reference symbol; and a feedback information processing process for controlling a transmission method of the transmission data based on the feedback information.
In this communication method, since a radio signal indicating a reference symbol sequence based on a pseudo-noise sequence is transmitted, feedback information obtained by despreading the reference symbol sequence, in which interference from other communication devices is suppressed or reduced, is transmitted. Appropriate control can be performed by using and controlling.

[12] A communication method according to an aspect of the present invention includes a wireless reception process in which a communication device receives a wireless signal indicating a transmission-side reference symbol sequence via a propagation path, and the wireless signal received by the communication device. A feedback information generating step of measuring a signal reception state based on a reference symbol sequence extracted from the signal and generating the feedback information according to the measured signal reception state; and a wireless transmission step of transmitting the feedback information by the communication device; including.
In this communication method, it is possible to suppress or reduce interference from a communication apparatus other than a desired communication apparatus using a reference symbol sequence, and generate more appropriate feedback information.

According to the present invention, appropriate feedback information can be obtained efficiently in a communication system capable of performing cooperative communication.

It is a schematic block diagram which shows the structure of the communication system in the 1st Embodiment of this invention. It is a schematic block diagram which shows the structural example of the communication system which does not include the mobile terminal device which performs the cooperative communication in the embodiment. It is a schematic block diagram which shows the structural example of the communication system which does not include the mobile terminal device which does not perform cooperative communication in the embodiment. It is a schematic block diagram which shows the structure of the base station apparatus 100 in the embodiment. 4 is a conceptual diagram showing an example in which resource element mapping units 301 to 30T map reference symbol sequences for four antenna ports in the same embodiment. FIG. It is a schematic block diagram which shows the structure of the mobile terminal device 150 in the embodiment. It is a flowchart which shows the procedure in which the base station apparatus 100 produces | generates and maps a reference symbol series in the same embodiment. It is a flowchart which shows the procedure in which the feedback information generation part 61 of the mobile terminal device 150 produces | generates feedback information in the same embodiment. It is a flowchart which shows the procedure in which the feedback information processing part 23 of the base station apparatus 100 determines the encoding rate etc. of transmission data based on feedback information in the embodiment. 4 is a conceptual diagram illustrating an example of a reference symbol sequence used by the base station apparatus 100 for an antenna port 1 in the embodiment. FIG. FIG. 10B is a conceptual diagram showing an example in which the base station apparatus 100 maps the reference symbol sequence of FIG. 10A in the same embodiment. FIG. 10B is a conceptual diagram showing an example in which the base station device 101 maps the reference symbol sequence obtained by cyclically shifting the reference symbol sequence of FIG. 10A to the same resource element as the base station device 100 in the embodiment. FIG. 10 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps reference symbol sequences in the same embodiment as in FIG. 10B. In the embodiment, the base station apparatus 101 is a conceptual diagram showing an example in which a reference symbol sequence is mapped to resource elements shifted by one subcarrier in the frequency direction from the position shown in FIG. 10C. In the 2nd Embodiment of this invention, the base station apparatus 100 is a conceptual diagram which shows the example which mapped the reference symbol series of the added antenna port. In the embodiment, the base station apparatus 100 is a conceptual diagram showing another example in which a reference symbol sequence of an added antenna port is mapped. FIG. 3 is a conceptual diagram illustrating an example of a 4-chip reference symbol sequence assigned to the antenna port 5 by the base station apparatus 100 in the embodiment. FIG. 13B is a conceptual diagram showing an example in which the base station apparatus 100 maps the reference symbol sequence of FIG. 13A in the same embodiment. FIG. 13B is a conceptual diagram illustrating an example in which the base station device 101 maps the reference symbol sequence obtained by cyclically shifting the reference symbol sequence of FIG. 13A to the same resource element as the base station device 100 in the embodiment. FIG. 14 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps reference symbol sequences in the same embodiment as in FIG. 13B. In the embodiment, the base station apparatus 101 is a conceptual diagram showing an example in which a reference symbol sequence is mapped to a resource element shifted by one subcarrier in the frequency direction from the position shown in FIG. 13C. In the 3rd Embodiment of this invention, it is a conceptual diagram which shows the example of the reference symbol series of 4 chips | tips which the base station apparatus 100 allocates to the antenna port 5. FIG. In the embodiment, it is a conceptual diagram which shows the example which the base station apparatus 100 mapped the reference symbol series. In the embodiment, the base station apparatus 101 maps the reference symbols of the antenna ports 1 to 4 by shifting in the frequency direction with respect to the mapping of the base station apparatus 100, and the reference symbol sequence of the antenna port 5 is the base station apparatus 100. It is a conceptual diagram which shows the example mapped to the resource element of the same position as this mapping. In the 4th Embodiment of this invention, it is a conceptual diagram which shows the example which mapped the reference symbol series of the antenna port 5 among the examples in which the base station apparatus 100 mapped the reference symbol series of a different antenna port for every sub-frame. . 4 is a conceptual diagram illustrating an example in which a base station apparatus 100 maps a reference symbol sequence of an antenna port 6 in the embodiment. FIG. 4 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps a reference symbol sequence of an antenna port 7 in the embodiment. FIG. 4 is a conceptual diagram illustrating an example in which a base station apparatus 100 maps a reference symbol sequence of an antenna port 8 in the embodiment. FIG. In the 5th Embodiment of this invention, it is a conceptual diagram which shows the example which mapped the reference symbol series of the antenna port 5 among the examples in which the base station apparatus 100 mapped the reference symbol series of a different antenna port for every resource block. . 4 is a conceptual diagram illustrating an example in which a base station apparatus 100 maps a reference symbol sequence of an antenna port 6 in the embodiment. FIG. 4 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps a reference symbol sequence of an antenna port 7 in the embodiment. FIG. 4 is a conceptual diagram illustrating an example in which a base station apparatus 100 maps a reference symbol sequence of an antenna port 8 in the embodiment. FIG. It is a conceptual diagram which shows the example which the base station apparatus 100 mapped the reference symbol series for 1 series to the some resource block in the frequency direction in the 6th Embodiment of this invention. It is a conceptual diagram which shows the example which the base station apparatus 100 mapped the reference symbol sequence for 1 sequence to the some resource block in the time direction in the 7th Embodiment of this invention. It is a conceptual diagram which shows the example which the base station apparatus 100 mapped the reference symbol sequence for 1 series to the some antenna port in the 8th Embodiment of this invention. In the 9th Embodiment of this invention, it is a conceptual diagram which shows the example of the reference symbol series based on the orthogonal code series which the base station apparatuses 100 and 101 use with respect to the antenna port 1. FIG. 4 is a conceptual diagram illustrating an example of a reference symbol sequence based on an orthogonal code sequence used by the base station apparatuses 100 and 101 for the antenna port 2 in the embodiment. FIG. In the embodiment, it is a conceptual diagram which shows the example which the base station apparatus 100 mapped the reference symbol series. In the embodiment, it is a conceptual diagram which shows the example which the base station apparatus 101 mapped the reference symbol series. It is a figure which shows the example which a mobile terminal transmits feedback information to a base station apparatus using the reference signal reference-transmitted from a base station. It is a figure which shows the example of the reference signal which a base station transmits.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a configuration of a communication system 900 according to the first embodiment of the present invention. The communication system 900 in FIG. 1 includes base station devices (communication device, first communication device, transmission device, cell, transmission point, transmission antenna group) 100 and 101 and mobile terminal devices (reception device, reception terminal) 150 and 151. Consists of including. Base station apparatus 100 and base station apparatus 101 are base stations adjacent to each other, and some of the cells overlap. The mobile terminal device 150 (communication device, second communication device) is located at the cell edge between the base station device 100 and the base station device 101, and performs cooperative communication with both base station devices 100 and 101. The mobile terminal apparatus 151 (third communication apparatus) is located near the cell center of the base station apparatus 100 and communicates with the base station apparatus 100 without performing cooperative communication. In addition, this invention includes the case where only either one of the mobile terminal apparatus 150 which performs cooperative communication, and the mobile terminal apparatus 151 which does not perform cooperative communication is included.

FIG. 2 is a schematic configuration diagram illustrating a configuration example of a communication system 900 when a mobile terminal device that performs cooperative communication is not included. In the figure, one mobile terminal apparatus 151 is located near the cell center of the base station apparatus 100 and communicates with the base station apparatus 100 without performing cooperative communication. The other mobile terminal apparatus 151 is located near the cell center of the base station apparatus 101, and communicates with the base station apparatus 101 without performing cooperative communication.

FIG. 3 is a schematic configuration diagram illustrating a configuration example of the communication system 900 when a mobile terminal device that does not perform cooperative communication is not included. In the figure, two mobile terminal apparatuses 150 are both located at the cell edges of the base station apparatus 100 and the base station apparatus 101, and perform cooperative communication with both base station apparatuses 100 and 101. In this way, there are a case where mobile terminal devices that perform cooperative communication and mobile terminal devices that do not perform cooperative communication coexist, a case where all mobile terminal devices do not perform cooperative communication, and a case where all mobile terminal devices perform cooperative communication. In any case, the communication devices (base station device and mobile terminal device) of the communication system 900 of the present embodiment can communicate. The same applies to the second and subsequent embodiments.

FIG. 4 is a schematic block diagram showing the configuration of the base station apparatus 100 according to the first embodiment of the present invention. In the figure, base station apparatus 100 includes encoding sections 241 to 24L, scrambling sections 251 to 25L, modulation sections 261 to 26L, layer mapping section 27, precoding section 28, resource element mapping sections 301 to 30T, and OFDM signal generation section 311. To 31T, wireless transmission units 321 to 32T, a reference signal generation unit 29, a wireless reception unit 21, a reception signal processing unit 22, and a feedback information processing unit 23. Here, L represents the number of codewords input to the encoding units 241 to 24L, and T represents the number of radio transmission units 321 to 32T (the number of antenna ports and the number of transmission antennas).

The radio reception unit 21 receives signals transmitted from the mobile terminal devices 150 and 151 through the uplink. The signals from the mobile terminal devices 150 and 151 received by the wireless reception unit 21 include feedback information and data signals. As will be described later, the feedback information is information based on the signal reception state (signal amplitude or the like) of the reference symbol (reference signal). That is, the wireless reception unit 21 (first wireless reception unit) receives feedback information based on the signal reception state of the reference symbol.
The reception signal processing unit 22 performs reception processing for transmission processing performed for transmission by the mobile terminal devices 150 and 151 such as OFDM demodulation processing, demodulation processing, and decoding processing on the signal received by the wireless reception unit 21. The feedback information is extracted from the received data signal and output to the feedback information processing unit 23. The base station apparatus 100 receives a plurality of mobile terminal apparatuses that have been subjected to user multiplexing using SC-FDMA (Single Carrier-frequency Division Multiple Access) as an uplink (that is, signal transmission from the mobile terminal apparatus to the base station apparatus). Are distinguished from each other. Note that the base station apparatus 100 may perform user multiplexing using other multiple access schemes such as OFDMA, time division multiple access, and code division multiple access.

Also, the base station apparatus 100 specifies resources (elements for signal transmission divided by time, frequency, code, spatial domain, etc.) for each mobile terminal apparatus to transmit feedback information, and the mobile terminal apparatus is specified. Send feedback information on the resource Thereby, the base station apparatus 100 distinguishes feedback information from each mobile terminal apparatus. Note that the base station apparatus 100 may distinguish the feedback information from each mobile terminal apparatus by another method, such as the mobile terminal apparatus adding a unique identification number for each mobile terminal apparatus to the feedback information. .

The feedback information processing unit 23 generates control signals for performing various adaptive controls on the data signals transmitted to the mobile terminal devices 150 and 151 based on the feedback information such as CQI, PMI, and RI. The feedback information processing unit 23 outputs the generated control signals to the encoding units 241 to 24L, the modulation units 261 to 26L, the layer mapping unit 27, the precoding unit 28, and the resource element mapping units 301 to 30T.
Here, the adaptive control performed by the feedback information processing unit 23 will be described. The mobile terminal apparatuses 150 and 151 transmit recommended transmission format information (CQI, RI, and PMI) to the base station apparatus 100 as feedback information.
The feedback information is obtained by indexing a transmission format known to both the base station apparatus 100 and the mobile terminal apparatuses 150 and 151, and indicates a transmission scheme (transmission format) recommended by the mobile terminal apparatuses 150 and 151 by an index. Recommended transmission format information. The base station apparatus 100 performs transmission using the transmission method indicated by the recommended transmission format information. Here, the index indicating the coding rate and the modulation scheme is called CQI, the index showing the precoding matrix is called PMI, and the index showing the number of layers (the number of spatial multiplexing, the number of ranks) Y is called RI. The feedback information processing unit 23 controls the encoding units 241 to 24L and the modulation units 261 to 26L according to CQI, controls the precoding unit 28 according to PMI, and controls the layer mapping unit 27 according to RI. That is, the feedback information processing unit 23 controls the transmission method of transmission data based on the feedback information.

Specifically, the feedback information processing unit 23 stores therein a lookup table in which CQI is associated with a coding rate and a modulation scheme, and the coding rate and modulation scheme corresponding to the input CQI are Is obtained from the lookup table. The feedback information processing unit 23 controls the encoding units 241 to 24L to perform encoding at the acquired encoding rate, and controls the modulation units 261 to 26L to perform modulation using the acquired modulation scheme. Similarly, the feedback information processing unit 23 stores therein a lookup table in which the PMI and the precoding matrix are associated with each other, and acquires the precoding matrix corresponding to the input PMI from the lookup table. The feedback information processing unit 23 controls the precoding unit 28 to perform precoding according to the acquired precoding matrix. Further, the feedback information processing unit 23 stores therein a lookup table in which RI and the number of layers Y are associated with each other, and acquires the number of layers Y corresponding to the input RI from the lookup table. The feedback information processing unit 23 controls the layer mapping unit 27 to perform mapping according to the acquired layer number Y.
The feedback information processing unit 23 may control an upper layer (not shown) that generates a code word in accordance with RI.

Note that the mobile terminal apparatus 150 may transmit feedback information regarding mapping to resources. The feedback information processing unit 23 controls the resource element mapping units 301 to 30T to perform mapping corresponding to the transmitted feedback information.
Note that SINR may be received as feedback information. In this case, the feedback information processing unit 23 stores therein a lookup table in which SINR and code rate are associated with each other.
Note that information indicating the channel condition (CSI; Channel State Information) is received as feedback information, and the precoding matrix, coding rate, modulation scheme, and number of layers Y that maximize the power received by the mobile terminal apparatus 150 are fed back. The information processing unit 23 may determine the information. A known method can be used as the determination method. The feedback information processing unit 23 controls the precoding unit 28 to perform precoding based on the determined precoding matrix, and controls the code units 241 to 24L to perform encoding at the determined coding rate, thereby determining the determined modulation. The modulation units 261 to 26L are controlled so as to perform modulation according to the method, and the layer mapping unit 27 is controlled to perform layer mapping with the determined number of layers Y.

The encoding units 241 to 24L are turbo codes or convolutional codes for a codeword (transmission data, information data signal) of a desired signal to be transmitted input from an upper layer processing unit (not shown) of the base station apparatus 100. Encoding is performed using an error correction code such as an LDPC (Low Density Parity Check) code, and the result is output to scramblers 251 to 25L. The code units 241 to 24L receive codeword input. It should be noted that the number of code words received by the encoding units 241 to 24L may be one or more. Note that the encoding units 241 to 24L may receive an input as a codeword, which is a processing unit that performs retransmission control such as HARQ (Hybrid Automatic Repeat reQuest) or a processing unit that performs error correction coding.
The scramblers 251 to 25L generate different scramble codes for each base station, and perform scramble processing based on the scramble codes on the encoded signals from the encoders 241 to 24L.

Modulators 261 to 26L perform BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation, orthogonal) on the scrambled signal. Modulation processing is performed using a modulation method such as amplitude modulation.
The layer mapping unit 27 maps the signals output from the modulation units 261 to 26L to a layer (rank) that performs spatial multiplexing such as MIMO (Multi-Input Multi-Output). When the number of codewords is 2 and the number of layers Y is 4, the layer mapping unit 27 converts the codewords into two parallel signals, thereby setting the number of layers Y to 4. Note that the layer mapping unit 27 may perform mapping using another conversion method. The number of code words input to the layer mapping unit 27 may be the same as the number of code words L input to the encoding units 241 to 24L, and is not limited to two. Further, the number Y of layers to which the layer mapping unit 27 performs mapping changes according to a control signal from the feedback information processing unit 23.

The precoding unit 28 performs precoding processing on the signal output from the layer mapping unit 27 (controls the phase and amplitude of the signal), and converts it into a parallel signal having the number T of antenna ports (transmitting antennas). The precoding unit 28 performs precoding processing according to a predetermined precoding matrix input from the feedback information processing unit 23. Note that the precoding unit 28 performs CDD (Cyclic Delay Delay Diversity), transmission diversity (SFBC (Spatial Frequency Block) Code), STBC (Spatial Time Block Block Code), TSTD (Time Switched Transmission Transmission Diversity) or FSTD (Frequency Switched Transmission). The precoding process may be performed using another method such as a process using the. In this case, the feedback information processing unit 23 outputs control information corresponding to the precoding process.

The reference signal generation unit 29 generates a sequence of reference symbols known to each other (transmission side reference symbol sequence) between the base station and the mobile terminal, and outputs it to the resource element mapping units 301 to 30T. Hereinafter, the reference symbol sequence generated by the reference signal generation unit 29 is referred to as a reference symbol sequence when attention is paid to the sequence, and is referred to as a reference symbol when attention is paid to individual reference symbols. This is referred to as a reference signal. Further, the reference signal generation unit 29 generates a reference symbol from a random number based on the cell ID. The reference signal generation unit 29 generates a reference symbol sequence based on an M (Maximum-length) sequence that is a pseudo noise sequence (pseudo random sequence, spreading code, PN (Pseudo Noise) sequence).
Note that the sequence used by the reference signal generation unit 29 may be an arbitrary sequence (signal) as long as both the base station apparatus and the mobile terminal apparatus are known. The reference signal generator 29 is a pseudo noise sequence other than M (Maximum-length) sequence such as Gold code, orthogonal Gold code, Barker code, orthogonal code sequence (Walsh code, OVSF (Orthogonal Variable Spreading Factor) code, Hadamard code, etc.) The reference symbol sequence may be generated based on the above, or a sequence obtained by cyclically shifting these sequences or a sequence expanded cyclically may be used. Based on the orthogonal code sequence, the reference signal generation unit 29 generates a reference symbol sequence that is orthogonal to a reference symbol sequence of another base station apparatus. Alternatively, the reference signal generation unit 29 may use a computer or the like to generate a sequence having excellent autocorrelation characteristics and cross-correlation characteristics, and use a reference symbol sequence based on this sequence. Details of the reference symbol sequence generated by the reference signal generation unit 29 will be described later.

The resource element mapping units 301 to 30T map the transmission data signal output from the precoding unit 28 and the reference symbol sequence output from the reference signal generation unit 29 to the resource element of each antenna port for each symbol. Hereinafter, mapping a reference symbol sequence to a resource element for each symbol is also simply referred to as mapping (assigning) a reference symbol sequence (to a resource element). FIG. 5 is a conceptual diagram illustrating an example in which the resource element mapping units 301 to 30T map reference symbol sequences for four antenna ports. In the figure, one resource block (subframe) is composed of 12 subcarriers in the frequency direction and 14 OFDM symbols in the time direction. Each subcarrier in one OFDM symbol is also called a resource element RE. The front and rear OFDM symbols obtained by dividing the subframe into two in the time direction are also called slots. The length of the OFDM symbol in the time direction is called OFDM symbol length LOFDS, the length of the slot in the time direction is called slot length LSL, and the length of the subframe in the time direction is called subframe length LSF. The length (bandwidth) of the subcarrier in the frequency direction is called a subcarrier interval WSC, and the length of the resource block in the frequency direction is called a resource block width WRB.

Numerals attached to resource elements RE in the figure represent reference symbols transmitted from antenna ports 1 to 4, respectively. In the resource elements RE in which the reference symbols are mapped to the respective antenna ports, no signal is assigned to the resource elements RE in the other antenna ports and zero is set so that the resource element mapping units 301 to 30T have the antennas. Signals between ports are orthogonalized. Note that the number of OFDM symbols of the resource block to which the resource element mapping units 301 to 30T perform mapping may be variable. For example, when adding a long guard interval, the resource element mapping sections 301 to 30T perform mapping by setting the number of OFDM symbols in one slot to six.

Here, the resource element mapping units 301 to 30T may change the number of resource blocks in the frequency direction according to the frequency bandwidth (system bandwidth) used by the communication system. For example, the resource element mapping units 301 to 30T can use 6 to 110 resource blocks, and can further increase the total system bandwidth to 110 or more by frequency aggregation. For example, one component carrier is composed of 100 physical resource blocks, and by setting five component carriers with a guard band between component carriers, the total system bandwidth is composed of 500 physical resource blocks, and resource The element mapping units 301 to 30T may perform mapping for each resource block. For example, one component carrier has a bandwidth of 20 MHz, and the total system bandwidth can be 100 MHz with five component carriers with a guard band between the component carriers. The resource element mapping units 301 to 30T may perform mapping for all resource blocks in the entire system bandwidth, or may perform mapping for some resource blocks. Further, mapping may be performed on some resource elements RE in the resource block.

Resource element mapping sections 301 to 30T assign reference symbols based on pseudo-noise sequences as reference symbols in at least one antenna port, and assign reference symbols generated from random numbers based on cell IDs as reference symbols in the remaining antenna ports. . Details will be described later. Further, different types of transmission data are mapped to resource elements other than the resource element to which the reference symbol is assigned.
The OFDM signal generators 311 to 31T perform frequency-time transform processing on the frequency domain signals output from the resource element mapping units 301 to 30T by inverse fast Fourier transform (IFFT), and thereby the time domain signals. Convert to Furthermore, the OFDM signal generators 311 to 31T add a guard interval (GI; Guard Interval; also referred to as CP) by cyclically expanding a part of each OFDM symbol converted into a time domain signal. .

Each of the wireless transmission units 321 to 32T includes one transmission antenna. The radio transmission units 321 to 32T perform frequency conversion from the baseband to the radio frequency on the signal output from the OFDM signal generation unit, and transmit the signal from the transmission antenna. As described above, the signals input from the OFDM signal generators 311 to 31T are signals indicating the transmission data mapped by the resource element mapping units 301 to 30T and the reference symbol sequence. That is, radio transmission sections 321 to 32T (first radio transmission sections) generate and transmit radio signals indicating transmission data and reference symbol sequences according to the mapping performed by mapping sections 301 to 30T.
Also in the base station apparatus 101, the configuration and the function of each unit are the same as those of the base station apparatus 100. However, as described later, the reference symbol sequence generated by the reference signal generation unit 29 of the base station apparatus 101 or the position where the resource element mapping units 301 to 30T map the reference symbols is different from the base station apparatus 100.

FIG. 6 is a schematic block diagram illustrating a configuration of the mobile terminal device 150 in the present embodiment. In FIG. 6, a mobile terminal apparatus 150 includes radio reception units 511 to 51R, OFDM signal demodulation units 521 to 52R, resource element demapping units 531 to 53R, a filter unit 55, a layer demapping unit 57, a deprecoding unit 56, and a demodulation. Units 581 to 58L, descrambling units 591 to 59L, decoding units 601 to 60L, a propagation path estimation unit 54, a feedback information generation unit (transmission path state measurement unit) 61, a transmission signal generation unit 62, and a wireless transmission unit 63. Composed. Here, the number of radio receiving units 511 to 51R (the number of receiving antennas) is denoted by R.
The mobile terminal apparatus 150 includes R reception antennas, and one radio reception unit corresponds to one antenna. The radio reception units 511 to 51R (second radio reception units) receive radio signals transmitted from the base station apparatus and passed through the transmission path (propagation path, channel), conversion processing from radio frequency to baseband signal, etc. I do.
The OFDM signal demodulation units 521 to 52R remove guard intervals, perform time frequency conversion processing by Fast Fourier Transform (FFT), etc., and convert the signals into frequency domain signals. Here, the received signal R (k) in the kth subcarrier is expressed as shown in Equation (1).

Figure JPOXMLDOC01-appb-M000001

However, N T is the number of transmit antennas, N R is the number of receive antennas, R (k) received signal corresponding to each receive antenna, the transmission signal S (k) is corresponding to each transmitting antenna, N (k) is the Noise corresponding to the receiving antenna, H (k) represents a frequency response corresponding to each receiving antenna and each transmitting antenna, and T represents a transposed matrix.
Resource element demapping sections 531 to 53R demap (separate and extract) the data signal mapped by base station apparatuses 100 and 101 and the reference symbol sequence, feed the data signal to filter section 55, and feed back the reference symbol sequence to feedback information. It outputs to the production | generation part 61 and the propagation path estimation part 54. FIG. The resource element demapping units 531 to 53R store therein mapping information performed by the base station apparatuses 100 and 101, and perform demapping based on this information.

The propagation path estimation unit 54 performs propagation path estimation by estimating amplitude and phase fluctuations (frequency response, transfer function) in each resource element based on the input reference symbols. For resource elements to which reference symbols are not mapped, propagation path estimation is performed by interpolating propagation path estimation values in the frequency direction and time direction based on the resource elements to which reference symbols are mapped. As an interpolation method, the propagation path estimation unit 54 uses linear interpolation. Note that other interpolation methods such as parabolic interpolation, polynomial interpolation, Lagrangian interpolation, spline interpolation, FFT interpolation, and minimum mean square error (Minimum Mean Square Error; MMSE) interpolation may be used. The propagation path estimation unit 54 performs propagation path estimation for each reception antenna with respect to each transmission antenna.

The filter unit 55 performs channel compensation on the data signal for each reception antenna output from the resource element demapping units 531 to 53R, using the channel estimation value output from the channel estimation unit 54, and transmits the transmission signal. Estimate S (k). The filter unit 55 estimates the transmission signal S (k) based on the ZF (Zero Forcing) criterion using the weighting coefficient M ZF of Expression (2).

Figure JPOXMLDOC01-appb-M000002

Here, H ′ (k) represents an estimated frequency response in cooperative communication, H ′ H (k) represents a complex conjugate transpose matrix of H ′ (k), and −1 represents an inverse matrix.
Note that the filter unit 55 may estimate the transmission signal S (k) based on the MMSE criterion using the weighting factor M MMSE of Equation (3), or may use another criterion.
In addition to the method of using the reference signal mapped for each transmission antenna port as already described as a method of estimating the estimated frequency response in the cooperative communication used in the filter unit 55, a reference signal for signal demodulation (UE -A method of further mapping the reference signal for each layer as specific RS, user-specific reference signal, Demodulation RS) can be used. Even when this method is used, the feedback information is preferably generated based on the reference signal mapped for each transmission antenna port as described above.

Figure JPOXMLDOC01-appb-M000003

However, H ′ (k), H ′ H (k) and −1 are as described above. Furthermore, sigma '2 is noise power, the I NR represents a unit matrix of N R × N R.
The filter unit 55 calculates an estimated value S ′ (k) of the transmission signal S (k) using Expression (4).

Figure JPOXMLDOC01-appb-M000004

However, M (k) represents a weighting coefficient (such as MZF or MMMSE ).

The deprecoding unit 56 performs processing for returning the precoding processing performed by the base station apparatuses 100 and 101 to the data signal detected by the filter unit 55. Note that precoding processing using CDD or transmission diversity does not require deprecoding processing on the receiving side. Therefore, when precoding processing using CDD or transmission diversity is performed in the base station apparatus, the deprecoding unit 56 does not perform processing for CDD or transmission diversity.
The layer demapping unit 57 demaps the signal for each layer to each codeword. Demodulating sections 581 to 58L demodulate the signal from layer demapping section 57 based on the modulation scheme used by base station apparatuses 100 and 101. The descrambling units 591 to 59L perform descrambling processing on the signals from the demodulation units 581 to 58L based on the scramble code used by the base station apparatuses 100 and 101. Decoding sections 601 to 60L perform error correction decoding processing on the signals from demodulation sections 581 to 58L based on the encoding method used by base station apparatuses 100 and 101, and perform upper layer processing of mobile terminal apparatus 150. Part (not shown).

The feedback information generation unit 61 generates feedback information based on the reference symbol sequence output from the resource element demapping units 531 to 53R. The feedback information generation unit 61 measures the received signal power to interference plus noise power ratio (SINR) using the input reference symbol sequence to generate feedback information. Details will be described later. Note that the feedback information generation unit 61 measures the received signal power to interference power ratio (SIR), the received signal power to noise power ratio (SNR), the path loss, or the like to provide feedback information. May be generated.
The unit for generating the feedback information includes the frequency direction (for example, for each subcarrier, for each resource element, for each resource block, for each subband composed of a plurality of resource blocks), for example, for the time direction (for example, for each OFDM symbol, For each frame, each slot, each radio frame, etc.), spatial direction (for example, each antenna port, each transmission antenna, each reception antenna, etc.), and the like can be used.

The feedback information generation unit 61 of the mobile terminal apparatus 150 that performs cooperative communication performs despreading processing on the reference symbol sequence extracted from the transmission signal. Hereinafter, the feedback information generation unit 61 of the mobile terminal device 150 is also referred to as a second feedback information generation unit (second transmission path condition measurement unit). On the other hand, the feedback information generation unit 61 of the mobile terminal device 151 that does not perform cooperative communication uses each reference symbol independently without despreading the reference symbol sequence. That is, feedback information generating section 61 of mobile terminal apparatus 151 measures the signal reception state (SINR) from the base station apparatus based on the reference symbols included in the reference symbol sequence, and generates feedback information according to the measured signal reception state. To do. Hereinafter, the feedback information generation unit 61 of the mobile terminal device 151 is also referred to as a first feedback information generation unit (first transmission path condition measurement unit). Details will be described later.

Here, the despreading process is an autocorrelation between a reference symbol sequence extracted by the resource element demapping units 531 to 53R from a radio signal received by the mobile terminal device and a known reference symbol sequence used in transmission by the base station device. It means taking. By taking autocorrelation, it is possible to extract reference symbols from the desired base station apparatus while suppressing or reducing interference from other base station apparatuses. That is, the feedback information generation unit 61 despreads the reference symbol sequence extracted from the received radio signal based on the reference symbol sequence transmitted by the base station apparatus (takes autocorrelation between them), and the reference symbol after despreading Further, feedback information is generated based on the despread reference symbols extracted as described above. The mobile terminal apparatus 150 can perform despreading processing by obtaining an autocorrelation value for an arbitrary reference symbol sequence (for example, a reference symbol sequence generated by a random number or the like). Here, if the reference symbol sequence to be correlated is a reference symbol sequence generated based on the pseudo noise sequence, the autocorrelation value is further improved. The unit for generating feedback information and the unit for performing despreading processing may be different.
The mobile terminal device 150 uses, as feedback information, precoding matrix information (PMI) used by the precoding units 28 of the base station devices 100 and 101, and coding processing and modulation performed by the coding units and modulation units of the base station devices 100 and 101. MCS (Modulation and Code Scheme) information (CQI) used in processing, information on the number of layers Y mapped by the layer mapping unit of the base station apparatus (RI), and the like are transmitted. In addition, information (CSI or the like) of transmission path conditions measured by the mobile terminal device 150 may be transmitted.

The transmission signal generation unit 62 performs encoding processing, modulation processing, OFDM signal generation processing, and the like to transmit (feedback) the feedback information output from the feedback information generation unit 61 to the base station apparatuses 100 and 101. Is generated.
The radio transmission unit 63 (second radio transmission unit) up-converts a transmission signal including feedback information generated by the transmission signal generation unit 62 to a radio frequency, and then transmits the radio signal to the base station apparatuses 100 and 101 through the uplink.
Also in the mobile terminal device 151, the configuration and functions of each unit are the same as those of the mobile terminal device 150. However, mobile terminal apparatus 151 is different from mobile terminal apparatus 150 in that it communicates only with base station apparatus 100 and feedback information generating section 61 does not despread the reference symbol sequence.

FIG. 7 is a flowchart illustrating a procedure in which the base station apparatus 100 generates and maps a reference symbol sequence.
In step S1, the reference signal generation unit 29 generates a reference symbol sequence for each antenna port based on the sequence stored therein, and outputs the reference symbol sequence to the resource element mapping units 301 to 30T. In step S2, the resource element mapping units 301 to 30T map the reference symbol sequence input from the reference signal generation unit 29 and the transmission data signal input from the precoding unit 28 for each symbol according to the mapping information stored therein. And output to the OFDM signal generators 311 to 31T. Thus, the base station apparatus 100 ends the reference symbol sequence generation and mapping process. Thereafter, the mapped signal is wirelessly transmitted via the OFDM signal generators 311 to 31T and the wireless transmitters 321 to 32T.
The procedure for generating and mapping the reference symbol sequence by the base station apparatus 101 is the same.

FIG. 8 is a flowchart showing a procedure in which the feedback information generation unit 61 of the mobile terminal device 150 generates feedback information. Feedback information generation unit 61 receives reference symbol sequences from resource element demapping units 531 to 53R and starts generating feedback information.
In step S21, the feedback information generation unit 61 performs despreading on the input reference symbol sequence, and based on the obtained reference symbol, information on the signal reception state from the base station apparatus 100 and the signal from the base station apparatus 101 And reception status information. In step S <b> 22, the feedback information generation unit 61 generates a PMI to be notified to each base station apparatus based on the signal reception state information from the base station apparatus 100 and the signal reception state information from the base station apparatus 101. In step S <b> 23, feedback information generation section 61 generates CQIs to be notified to each base station apparatus based on the signal reception state information from base station apparatus 100 and the signal reception state information from base station apparatus 101. In step S <b> 24, the feedback information generation unit 61 generates RI to be notified to each base station apparatus based on the signal reception state information from the base station apparatus 100 and the signal reception state information from the base station apparatus 101. The feedback information generation unit 61 ends the feedback information generation process. Thereafter, the generated CQI, PMI, and RI are wirelessly transmitted as feedback information via the transmission signal generation unit 62 and the wireless transmission unit 63.
The procedure for the feedback information generating unit 61 of the mobile terminal device 151 to generate feedback information is the same. However, in the case of the mobile terminal apparatus 151, the feedback information generation unit 61 does not perform despreading in step S21, but generates information on the signal reception state from the base station apparatus 100 using each of the input reference symbols as it is. In the following steps, the feedback information generation unit 61 generates only feedback information to be notified to the base station apparatus 100.
In addition, as a signal reception state information, a frequency response or a transfer function in a propagation path between the base station device and the mobile terminal device can be used.
The order of generating feedback information is not limited to the above.

FIG. 9 is a flowchart illustrating a procedure in which the feedback information processing unit 23 of the base station apparatus 100 determines the coding rate of the data signal based on the feedback information. The feedback information processing unit 23 receives the feedback information from the received signal processing unit and starts processing.
In step S 31, the feedback information processing unit 23 extracts feedback information (CQI, PMI, and RI) from the mobile terminal device 150 and feedback information from the mobile terminal device 151 from the signal input from the received signal processing unit 22. In step S32, the feedback information processing unit 23 refers to the lookup table stored therein, determines the coding rate based on the CQI from the mobile terminal devices 150 and 151, and notifies the coding units 241 to 24L. The encoding units 241 to 24L perform encoding by changing the encoding rate to the notified encoding rate. In step S33, the feedback information processing unit 23 determines a modulation scheme change based on the CQI from the mobile terminal apparatuses 150 and 151 with reference to a lookup table stored therein, and notifies the modulation units 261 to 26L. The modulation units 261 to 26L perform modulation according to the notified modulation method. In step S <b> 34, the feedback information processing unit 23 determines a change in the number of layers based on the CQI from the mobile terminal devices 150 and 151 with reference to a lookup table stored therein, and notifies the layer mapping unit 27 of the change. The layer mapping unit 27 performs mapping according to the notified number of layers. In step 35, the feedback information processing unit 23 determines a precoding matrix change based on the PMI from the mobile terminal devices 150 and 151 with reference to a lookup table stored therein, and notifies the precoding unit 28 of the change. The precoding unit 28 performs precoding according to the notified precoding matrix. Thus, the feedback information processing unit 23 ends the determination process such as the coding rate.
The procedure in which the feedback information processing unit 23 of the base station apparatus 101 determines the coding rate and the like is the same. However, in the case of the base station apparatus 101, the feedback information processing unit 23 extracts only feedback information from the mobile terminal apparatus 150 in step S31, and encodes based on the feedback information from the mobile terminal apparatus 150 in the following steps as well. Determine rates, etc.

Next, the mapping of the reference symbol sequence generated by the reference signal generation unit 29 of the base station apparatuses 100 and 101 based on the pseudo noise sequence and the reference symbol sequence performed by the resource element mapping units 301 to 30T used in the present embodiment. explain.
First, a case where base station apparatuses 100 and 101 map a reference symbol sequence generated from a cyclically shifted sequence to the same resource element will be described.
FIG. 10A is a conceptual diagram illustrating an example of a reference symbol sequence used by base station apparatus 100 for antenna port 1. The reference symbol sequences a to h in the figure are generated based on an M sequence that is a pseudo-noise sequence of 8 chips (bits).
The series in the figure is a series based on the M series. The M-sequence has excellent autocorrelation characteristics (that is, when despreading is performed, a sharp (high) correlation value (peak value) is obtained when the sequence is synchronized, and low when the sequence is out of synchronization. A pseudo-noise sequence from which a correlation value is obtained. The 8-chip sequence a to h provides a sharp correlation value at the position a, that is, a sharp correlation value is obtained when the correlation is obtained without shifting the sequence. Note that the reference symbol sequence generated by the reference signal generation unit 29 is not limited to the M sequence, and reference symbols of other sequences may be generated.

FIG. 10B is a conceptual diagram illustrating an example in which the base station apparatus 100 maps the reference symbol sequence in FIG. 10A. FIG. 10C is a conceptual diagram illustrating an example in which the base station device 101 maps the reference symbol sequence obtained by cyclically shifting the reference symbol sequence in FIG. 10A to the same resource element as the base station device 100. 10B and 10C, among the reference symbol sequences shown in FIG. 5, the reference symbol sequences for antenna port 1 are indicated by a to h, and the reference symbol sequences for antenna ports 2 to 4 are indicated by shading.

10C, the reference symbol sequence used by base station apparatus 101 is a cyclic shift of the series used by base station apparatus 100 in FIG. 10B. By shifting cyclically, the position where a sharp correlation value is obtained can be varied. Base station apparatus 100 and base station apparatus 101 map reference symbol sequences to the same resource elements for each symbol. The reference signal generation unit 29 of the base station apparatus 100 generates a signal based on a 0-chip shifted pseudo noise sequence, that is, a sequence that is not shifted, as a reference symbol sequence for the antenna port 1. Resource element mapping sections 301 to 30T of base station apparatus 100 map the generated reference symbol sequence as shown in FIG. 10B. Further, the reference signal generation unit 29 of the base station 101 generates a signal based on a one-chip shifted pseudo noise sequence as a reference symbol sequence for the antenna port 1. That is, the reference symbol sequence generated by the reference signal generation unit 29 is a cyclic shift of the reference symbol sequence of another base station apparatus. Resource element mapping sections 301 to 30T of base station 101 map generated reference symbol sequences as shown in FIG. 10C.

Next, the effect obtained by mapping the reference symbol sequence as shown in FIGS. 10B and 10C will be described. First, a case will be described where mobile terminal apparatus 150 that performs cooperative communication between base station 100 and base station 101 estimates feedback information for each base station apparatus. When estimation is performed using reference symbols independently from each of base station apparatuses 100 and 101 (that is, without performing despreading), transmission signals between adjacent cells interfere with each other, and mobile terminal apparatus 150 in particular When in the area, the mobile terminal apparatus 150 estimates feedback information in a situation where inter-cell interference is large. On the other hand, in the data transmission with respect to the mobile terminal apparatus 150 performing the cooperative communication, the inter-cell interference is suppressed or reduced. For this reason, the situation in which inter-cell interference with which feedback information is estimated is large and the situation in which cooperative communication is actually performed are significantly different. Therefore, it is necessary to estimate optimal feedback information (feedback information in a state where inter-cell interference is suppressed or reduced) for performing cooperative communication. Furthermore, depending on the method of cooperative communication performed by the mobile terminal apparatus 150 in the cell edge region, it is necessary to transmit feedback information to each of the base station apparatuses 100 and 101 that are going to perform the cooperative communication.

By mapping the reference symbol sequence as shown in FIG. 10B and FIG. 10C, when the mobile terminal apparatus 150 performs despreading, the positions of the autocorrelation peak values for the base station apparatuses 100 and 101 are different from each other. . For this reason, the feedback information generation unit 61 of the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station apparatus 100 and the base station apparatus 101 and performs cooperative communication suppresses interference from neighboring cells by performing despreading or The optimum feedback information for performing cooperative communication can be estimated. For example, when the base station apparatus 100 and the base station apparatus 101 transmit the same data signal in synchronization (for example, the base station apparatus 100 and the base station apparatus 101 exchange synchronization information with priority or wirelessly, For the reference symbols, the base station apparatuses 100 and 101 transmit different reference symbols using the same resource element, so that the reference symbols are transmitted. The mobile terminal apparatus 150 can generate and transmit feedback information for each base station apparatus without an increase in overhead due to the above. In particular, it is desirable to determine the precoding matrix according to the signal reception state from each base station apparatus in the mobile terminal apparatus. The mobile terminal apparatus 150 determines, for each base station apparatus, a precoding matrix (specifically, a PMI) corresponding to a signal reception state from each base station apparatus (each of the base station apparatuses 100 and 101), or individually. The base station apparatus (each of the base station apparatuses 100 and 101) can determine and transmit a common precoding matrix (specifically, PMI) between the base station apparatuses in accordance with the signal reception state.

In addition, the mobile terminal apparatus 150 can generate feedback information by extracting reference symbols for each base station apparatus by correlating the reference symbol sequences of the base station apparatuses 100 and 101 with the received reference symbol series. it can. By using a pseudo-noise sequence having excellent autocorrelation characteristics as a sequence that is a basis for generating a reference symbol sequence, the effect of suppressing or reducing interference can be obtained more greatly. Furthermore, the effect of suppressing or reducing interference can be further increased by using an M sequence having excellent autocorrelation characteristics.
On the other hand, the mobile terminal apparatus 151 that does not perform the cooperative communication independently uses the reference symbol sequence without performing despreading in the feedback information generation unit 61 even if the reference symbol sequence is based on the pseudo-noise sequence. By using this, it is possible to estimate optimal feedback information in consideration of interference power from neighboring cells without increasing the number of processes for despreading. Further, for the mobile terminal apparatus 151 that does not perform cooperative communication, the base station apparatus 101 does not need to newly notify the mobile terminal apparatus of control information or the like.
In addition, a communication system in which mobile terminal apparatuses 150 that perform cooperative communication and mobile terminal apparatuses that do not perform cooperative communication can be realized without increasing the ratio (overhead) of reference symbols to the entire resource.

Here, the effect of suppressing or reducing interference is increased by orthogonalizing reference symbol sequences based on pseudo noise sequences between adjacent cells. Therefore, the sequences used by the base station device 100 and the base station device 101 are assigned by a control station located above these base station devices so that their reference symbol sequences are orthogonal to each other. It should be noted that a method of cooperating with each other through a line such as X2 or radio where the base stations communicate control signals or a method generated by each base station device using a parameter such as a cell ID is used. It may be.
Base station apparatuses 100 and 101 notify mobile terminal apparatus 150 of the used pseudo-noise sequence, the used reference symbol, the number of shifts, the index (number) of a predefined reference symbol sequence, and the like. Note that the mobile terminal apparatus 150 may specify the pseudo noise sequence and the number of shifts using parameters such as the cell ID notified from the base station apparatuses 100 and 101.
Even when the mobile terminal device 150 performs cooperative communication, the base station device that transmits the control information signal to the mobile terminal device 150 and the base station device that the mobile terminal device 150 transmits feedback information The base station apparatus is not limited to one of the base station apparatuses, and may be any one of base station apparatuses performing cooperative communication such as an anchor cell. Even when the mobile terminal device 150 performs cooperative communication, the base station device that transmits the control information signal to the mobile terminal device 150 and the base station device that transmits the feedback information to the mobile terminal device 150 perform cooperative communication. All the base station apparatuses currently performing may be sufficient.

Next, a case where the position of the resource element to which the base station apparatus 100 maps the reference symbol and the position of the resource element to which the base station apparatus 101 maps the reference symbol will be described. In FIG. 10B and FIG. 10C, the case where the resource elements for mapping the reference symbols (sequences) in the base station apparatus 100 and the base station apparatus 101 are the same has been described, but the reference symbols in the base station apparatus 100 and the base station apparatus 101 are the same. The same effect can be obtained even when the resource element to be mapped is shifted by a parameter such as a cell ID.

FIG. 11A is a conceptual diagram illustrating an example in which the base station apparatus 100 maps reference symbol sequences in the same manner as in FIG. 10B. FIG. 11B is a conceptual diagram illustrating an example in which the base station apparatus 101 maps the reference symbol sequence to a resource element shifted by one subcarrier in the frequency direction from the position illustrated in FIG. 10C. 11A and 11B, as in FIGS. 10B and 10C, the reference symbol sequences of antenna port 1 are indicated by a to h, and the reference symbol sequences of antenna ports 2 to 4 are indicated by shading.
11A and 11B, the base station apparatus 100 and the base station apparatus 101 perform mapping in the same manner as described with reference to FIGS. 10B and 10C. However, in FIG. 11B, the mapping performed by base station apparatus 101 is shifted in the frequency direction by one subcarrier higher in the frequency direction (upward) than in the case of FIG. 10C. That is, resource element mapping sections 301 to 30T of base station apparatuses 100 and 101 map reference symbols to resource elements different from each other between adjacent base station apparatuses.

In the example illustrated in FIGS. 11A and 11B, the reference symbol sequence of the base station apparatus 100 received by the mobile terminal apparatus and the arrangement of the data signals of the base station apparatus 101 are mapped to the same resource element. Although the reference symbol sequence from base station apparatus 100 and the symbol series (data signal sequence) from base station apparatus 101 are not orthogonal to each other, reference signal generation unit 29 uses an M sequence having sharp autocorrelation characteristics. By generating a reference symbol sequence and performing despreading by the mobile terminal apparatus 150, interference from other cells can be greatly reduced, and optimal feedback information for performing cooperative communication can be estimated. . Note that the sequence used by the reference signal generation unit 29 may be a sequence having excellent autocorrelation characteristics, and is not limited to the M sequence.
In the above description, the reference symbol sequence based on the pseudo noise sequence is used for all reference symbols of all antenna ports. However, the resource element mapping units 301 to 30T use the pseudo noise sequence only for a part of them. The reference symbol sequence that has been stored may be mapped. For example, a reference symbol sequence based on a pseudo noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports. .

In addition, although the case where the number of antenna ports of the base station apparatuses 100 and 101 is four has been described above, the number of antenna ports is not limited to four and may be one or more antenna ports. 11A and 11B, a case has been described in which a resource element that maps a reference symbol sequence is shifted between adjacent cells based on a parameter such as a cell ID. However, cooperative communication such as between all cells or Active CoMP set is performed. The resource elements to which reference symbols are mapped in advance may be determined among the plurality of cells that perform the above, and the resource elements determined by the resource element mapping units 301 to 30T may be stored.
Although the case where reference symbol sequences are arranged in all resource blocks has been described above, the source element mapping units 301 to 30T may be arranged in only some resource blocks. A base station such as RRE (Remote Radio Equipment), RRH (Remote Radio Head), or an independent antenna is controlled through a wire such as an optical fiber as a unit for orthogonalizing reference symbol sequences based on a pseudo noise sequence between cells. A unit, a unit controlled by a base station such as a relay, or a unit configured by a plurality of base stations performing cooperative communication such as Active CoMP set, or a unit of a resource element that maps a reference symbol is used. It may be.

The base station apparatus 100 determines the type of pseudo-noise sequence, the position where the peak of the autocorrelation characteristic is obtained, etc. based on the identification information and control information notified to the mobile terminal apparatus 150, and the base station apparatus 100 determines the mobile terminal apparatus. 150 may be notified of identification information and control information at the same time by notifying 150 the type of pseudo noise sequence, the position where the peak of the autocorrelation characteristic is obtained, and the like.
Note that the sequence length of the pseudo-noise sequence used by the base station apparatus may be different from the sequence length that the mobile terminal apparatus performs despreading processing on. In the above description, the mobile terminal apparatus 150 performs the despreading process on the reference symbol sequence in order to generate feedback information. However, the mobile terminal apparatus 150 performs the despreading process when estimating the propagation path for demodulating the information data signal. May be.

In addition, although the case where cooperative communication is performed between a plurality of base station devices and at least one mobile terminal device has been described above, cooperative communication according to another aspect may be used. Collaborative communication between physically independent base station apparatuses, or cooperative communication between sectors in one base station apparatus having a sector configuration, or a transmission apparatus (RRE) connected to the base station apparatus by wire such as an optical fiber Or RRH), or a cooperative communication between a base station apparatus and a transmission apparatus (such as a relay station or a repeater station) connected wirelessly using relay technology. Also good. Furthermore, it may be a case where cooperative communication is performed by combining them. Moreover, when these transmission apparatuses have a plurality of transmission antennas (antenna ports), cooperative communication may be performed using some of the transmission antennas. Moreover, you may communicate with at least 1 mobile terminal device in cooperation between several antenna ports among these transmitters.
In the above, a mobile terminal apparatus that performs cooperative communication with a plurality of base station apparatuses performs despreading processing, and performs communication with one base station apparatus without performing cooperative communication. Although the case where no despreading processing is performed has been described, the present invention is not limited to this. For example, a mobile terminal that performs cooperative communication may perform despreading processing, and a mobile terminal that performs MIMO (Multi Input Multi Output) communication may generate feedback information without performing despreading processing.

Feedback information generating section 29 of mobile terminal apparatus 150 that receives transmission signals from a plurality of base station apparatuses 100 and 101 simultaneously and performs cooperative communication performs despreading on reference symbol sequences from the respective base station apparatuses. Thus, the signal power (signal amplitude) obtained from each base station apparatus is measured while suppressing interference from adjacent cells. The feedback information generation unit 29 estimates SINR from the signal power (signal amplitude) obtained from each base station apparatus, acquires CQI, PMI, and RI corresponding to the SINR estimated from the lookup table, and feeds them back to the feedback information. And That is, the feedback information is information based on the signal reception state (signal amplitude) of the reference symbol.
As will be described later, a combination of SINRs in a base station apparatus that performs cooperative communication as SINR (total SINR) may be estimated, or SINRs in respective base stations may be estimated.
Note that the mobile terminal apparatus 151 that does not perform cooperative communication may also despread the reference symbol sequence. The mobile terminal device 151 receives the reference symbol sequence transmitted from the communicating base station device (own base station, own cell, serving cell) 100, and correlates the reference symbol sequence transmitted by the base station device. Thus, the signal power (signal amplitude) obtained by this base station can be measured while suppressing interference from adjacent cells. In addition, since each reference symbol sequence chip includes an interference component from an adjacent base station, the reference symbol amplitude and received signal from the own base station are referred to by referring to the resource element to which the reference symbol is mapped. By calculating the square norm of the difference, average interference signal power can be obtained, and optimum feedback information (CQI, PMI, etc. based on SINR or SINR) can be estimated.

In the above, a case where one base station apparatus and at least one mobile terminal apparatus communicate with each other and a plurality of base station apparatuses cooperate with each other to communicate with at least one mobile terminal apparatus has been described. There is no need to communicate at the same time. That is, only one base station apparatus and at least one mobile terminal apparatus communicate in a certain time zone, and in another certain time zone, a plurality of base station apparatuses cooperate with each other to at least one mobile terminal apparatus. Communication may be performed.
Mobile terminal apparatus 150 may perform despreading processing beyond the sequence length used by base station apparatus 100, or may perform despreading processing for a length less than the sequence length.

Next, a detailed procedure for generating feedback information by the feedback information generation unit 61 of the mobile terminal apparatus 150 that performs despreading processing will be described.
Base station apparatus 100 or 101 notifies mobile terminal apparatus 150 of a set of cells on which despreading processing is to be performed. The cell set information includes the number of cells, each cell ID, and the pseudo noise sequence of each cell. Note that the pseudo-noise sequence of a cell may be determined by a cell ID or the like. The base station apparatus 100 or 101 receives a measurement report (Measurement Report) from the mobile terminal apparatus 150, and determines a set of cells in which cooperative communication is to be performed using the measurement report. When the mobile terminal apparatus 150 is notified of the set of cells to be despread, the mobile terminal apparatus 150 performs despread processing on the reference symbol sequence transmitted from each cell.
As described above, feedback information generation section 61 performs despreading on the received reference symbol sequence to obtain a reference symbol in which interference from other base stations is suppressed or reduced. The feedback information generation unit 61 measures signal power (signal amplitude) from a reference symbol whose interference is suppressed or reduced. The feedback information generation unit 61 estimates SINR from the measured signal power, acquires CQI, PMI, and RI corresponding to the SINR estimated from the lookup table, and uses these as feedback information.

CQI, PMI, and RI are preset as a plurality of types of patterns (indexed), and the pattern closest to the pattern is selected. The feedback information generation unit 61 stores therein a lookup table in which SINR and CQI satisfying required quality are associated with each other in advance. The feedback information generation unit 61 uses the SINR estimated as described above to obtain a CQI by referring to a lookup table. Also for PMI, the feedback information generation unit 61 stores a lookup table in advance, refers to the lookup table using SINR, and acquires a precoding matrix that maximizes received power. Also for the RI, the feedback information generation unit 61 stores a lookup table in advance, and acquires the RI by referring to the lookup table using SINR.
Note that the feedback information generation unit 61 may generate CSI as feedback information. In this case, CSI in the receiving antenna port for each transmitting antenna port is generated from the result of performing the despreading process. Note that the feedback information generation unit 61 may compress the feedback information based on the CSI to reduce the amount of feedback information. A difference between transmission path conditions continuous in the time direction or the frequency direction may be used as feedback information. Further, the feedback information may be generated for each subband.

The following two methods are conceivable as a method of measuring the channel state from which the feedback information generating unit 61 generates feedback information. The first method is a method for obtaining CQI and PMI based on total SINR or total SINR. The feedback information generation unit 61 combines reference symbols of each cell obtained by performing the despreading process, measures a channel state based on one combined reference symbol, and feedback information based on the measured channel state Is generated. On the other hand, the second method is a method of obtaining CQI and PMI based on SINR in each base station and SINR in each base station. The feedback information generation unit 61 measures the channel state for each reference symbol of each cell obtained by performing the despreading process, and generates feedback information for necessary cells based on the measured channel state. The feedback information generation unit 61 generates feedback information by the first method. Note that feedback information may be generated by the second method, or both the first method and the second method may be provided, and feedback may be performed by a method designated by the base station. .

<Second Embodiment>
Next, a second embodiment of the present invention will be described. In the present embodiment, the resource element mapping units 301 to 30T map one series of reference symbol sequences for each resource block unit.
The communication system in the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to those in the communication system in the first embodiment, but 100 and 101 are antennas included in the first embodiment. In addition to ports 1 to 4, antenna ports 5 to 8 are further included. In this embodiment, the mapping method of the resource element mapping unit is different from that of the first embodiment. Below, it demonstrates centering on a different part from 1st Embodiment.

First, a case will be described in which base station apparatuses 100 and 101 map reference symbol sequences to the same resource element.
FIG. 12A shows an example where base station apparatus 100 maps reference symbol sequences of antenna ports 5 to 8 to resource elements. FIG. 12B shows another example in which the base station apparatus 100 maps the reference symbol sequences of the antenna ports 5 to 8 to resource elements. Numbers 5 to 8 attached to resource elements in FIGS. 12A and 12B indicate reference symbol sequences of antenna ports 5 to 8, respectively.
In the resource elements of the reference symbols mapped to the respective antenna ports, the antenna ports are orthogonalized by assigning no signal to the resource elements in other antenna ports and setting them to zero (null). In the present embodiment, antenna ports 1 to 4 are reference symbols generated based on random numbers using cell IDs, and these reference symbols are shown in shades in FIGS. 12A and 12B. Base station apparatus 100 assigns reference symbol sequences of antenna ports 5 to 8 as shown in FIG. 12A. Note that base station apparatus 100 may allocate reference symbol sequences of antenna ports 5 to 8 as shown in FIG. 12B, or may perform other allocations.

FIG. 13A is a conceptual diagram illustrating an example of a 4-chip reference symbol sequence allocated to antenna port 5 among four newly added antenna ports illustrated in FIG. 12A by base station apparatus 100. This reference symbol sequence is a reference symbol sequence based on a pseudo noise sequence. FIG. 13B is a conceptual diagram illustrating an example in which the base station apparatus 100 maps the reference symbol sequence in FIG. 13A. FIG. 13C is a conceptual diagram illustrating an example in which the base station device 101 maps the reference symbol sequence obtained by cyclically shifting the reference symbol sequence in FIG. 13A to the same resource element as the base station device 100. In FIG. 13B and FIG. 13C, among the reference symbol sequences shown in FIG. 12A, the reference symbol sequences for antenna port 5 are indicated by a to d, and the reference symbols for antenna ports 1 to 4 are indicated by shading. Here, only the reference symbol sequence of antenna port 5 is shown, and the reference symbol sequences of antenna ports 6 to 8 shown in FIG. 12A are not shown. The reference signal generation unit 29 uses a sequence having excellent autocorrelation characteristics such as an M sequence as a pseudo noise sequence. In the 4-chip series a to d, a sharp peak is obtained at the position a. Base station apparatus 100 and base station apparatus 101 map the reference symbol sequence at the same position of the resource element. In addition, base station apparatus 101 uses, as a reference symbol series, a series of base station apparatus 100 that is cyclically shifted by one chip.

The reference signal generation unit 29 of the base station apparatus 100 generates a reference symbol sequence based on a pseudo noise sequence shifted (ie, not shifted) by 0 chips as a reference symbol sequence for the antenna port 5. The resource element mapping unit of base station apparatus 100 maps the generated reference symbol sequence as shown in FIG. 13B. In addition, the reference signal generation unit 29 of the base station apparatus 101 generates a reference symbol sequence based on a pseudo noise sequence shifted by one chip as a reference symbol sequence for the antenna port 5. The resource element mapping unit of the base station 2 maps the generated reference symbol sequence as shown in FIG. 13C.
The base station device 100 maps the reference symbol sequence as shown in FIG. 13B, and the base station device 101 maps the reference symbol sequence as shown in FIG. 13C, so that the reference symbol sequence and the base station device transmitted by the base station device 100 are mapped. The reference symbol sequence transmitted by 101 is orthogonal to each other at different peak positions. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated.

Next, a case will be described where the position of the resource element to which the base station apparatus 100 maps the reference symbol and the position of the resource element to which the base station apparatus 101 maps the reference symbol are different from each other.
FIG. 14A is a conceptual diagram illustrating an example in which the base station apparatus 100 maps reference symbol sequences in the same manner as in FIG. 13B. FIG. 14B is a conceptual diagram illustrating an example in which the base station apparatus 101 maps the reference symbol sequence to resource elements shifted by one subcarrier in the frequency direction from the position illustrated in FIG. 13C. 14A and 14B, as in FIGS. 13B and 13C, the reference symbol series of antenna port 5 is indicated by a to d, and the reference symbols of antenna ports 1 to 4 are indicated by shading.

In FIG. 13B and FIG. 13C, the case where the resource elements for mapping reference symbols (sequences) in the base station apparatus 100 and the base station apparatus 101 are the same has been described, but as shown in FIG. 14A and FIG. The same effect can be obtained even when resource elements that map reference symbols in 100 and the base station 101 shift according to parameters such as a cell ID. 14A and 14B, the base station apparatus 100 and the base station apparatus 101 perform mapping in the same manner as described with reference to FIGS. 13B and 13C. However, in FIG. 14B, the mapping performed by the base station apparatus 101 is shifted in the frequency direction (upward) by one subcarrier in the frequency direction compared to the case of FIG. 13C. 14A and 14B, as described in FIGS. 11A and 11B, the reference symbol sequence received from the base station device 100 and the symbol sequence received from the base station device 101 received by the mobile terminal device are orthogonal to each other. Although there is no M-sequence with sharp autocorrelation characteristics and the mobile terminal apparatus 150 performs despreading, it is possible to significantly reduce other cell interference with each other and estimate optimum feedback information for cooperative communication can do.
In addition, although the case where the reference symbol sequence based on the pseudo noise sequence is used for all the reference symbols of all the antenna ports has been described above, only a part of them may be used. For example, a reference symbol sequence based on a pseudo noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports. .

In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four and may be one or more antenna ports. .
In the above description, four antenna ports are further added to the four antenna ports 1 to 4. However, the present invention is not limited to this, and one or more antenna ports are provided for one or more antenna ports. Any port may be added. For example, six new antenna ports may be added to the two antenna ports 1 and 2. Alternatively, eight antenna ports may be newly added.
In the above description, the resource element that maps the reference symbol sequence is shifted between adjacent cells based on a parameter such as a cell ID. However, all the cells or a plurality of cooperative communication such as Active CoMP set are performed. Resource elements for mapping reference symbol sequences may be determined in advance between cells.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. In the present embodiment, the resource element mapping units 301 to 30T map one sequence of reference symbol sequences in one resource block, and perform this for each resource block.
The communication system in the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system in the first embodiment, but the mapping method of the resource element mapping unit is different. Below, it demonstrates centering on a different part from 1st Embodiment.
Base station apparatuses 100 and 101 of the present embodiment further include antenna ports 5 to 8 in addition to antenna ports 1 to 4 included in the first embodiment.

FIG. 15A shows a 4-symbol reference symbol sequence assigned to antenna port 5 among four newly added antenna ports. This reference symbol sequence is a conceptual diagram showing an example of a reference symbol sequence based on a pseudo noise sequence. FIG. 15B is a conceptual diagram illustrating an example in which the base station apparatus 100 maps a reference symbol sequence. 15C, the base station apparatus 101 maps the reference symbols of the antenna ports 1 to 4 while shifting the mapping of the base station apparatus 100 in the frequency direction, and the reference symbol sequence of the antenna port 5 is the base station apparatus. It is a conceptual diagram which shows the example mapped to the resource element of the same position as 100 mapping. In FIG. 15B and FIG. 15C, the reference symbol series of antenna port 5 is indicated by a to d, and the reference symbols of antenna ports 1 to 4 are indicated by shading. Here, only the reference symbol sequence of antenna port 5 is shown, and the reference symbol sequences of antenna ports 6 to 8 are not shown.

The reference signal generation unit 29 uses a sequence having excellent autocorrelation characteristics such as an M sequence as a pseudo noise sequence. In the 4-chip series a to d, a sharp peak is obtained at the position a. Base station apparatus 100 and base station apparatus 101 map the reference symbol sequence to the same position of the resource element. Also, base station apparatus 101 uses a series of base station apparatus 100 that is cyclically shifted by one chip as a reference symbol series.
The reference signal generation unit 29 of the base station apparatus 100 generates a reference symbol sequence based on a 0-chip shifted pseudo noise sequence as a reference symbol sequence for the antenna port 5. The resource element mapping unit of base station apparatus 100 maps the generated reference symbol sequence as shown in FIG. 15B. In addition, the reference signal generation unit 29 of the base station apparatus 101 generates a reference symbol sequence based on a one-chip shifted pseudo noise sequence as a reference symbol sequence for the antenna port 5. The resource element mapping unit of the base station 2 maps the generated reference symbol sequence as shown in FIG. 15C.

By mapping the reference symbol sequence as shown in FIG. 15B and FIG. 15C, the reference symbol sequence transmitted by the base station apparatus 100 and the reference symbol sequence transmitted by the base station apparatus 101 are different from each other in the sequence peak position and orthogonal to each other. ing. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated.
In addition, although the case where the reference symbol sequence based on the pseudo noise sequence is used for all the reference symbols of all the antenna ports has been described above, only a part of them may be used. For example, a reference symbol sequence based on a pseudo noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports. .

In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four and may be one or more antenna ports. . In the above description, the case where there are four antenna ports 1 to 4 reference symbols has been described. In addition, although the case where the reference symbol series is arranged in all resource blocks has been described above, it may be arranged only in some resource blocks.
In the above description, four antenna ports are further added to the four antenna ports 1 to 4. However, the present invention is not limited to this, and one or more antenna ports are provided for one or more antenna ports. Any port may be added. For example, six antenna ports may be newly added to the two antenna ports 1 and 2.
Note that the method described in this embodiment and the method described in the second embodiment may be used in combination.

<Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described.
FIGS. 16A to 16D are conceptual diagrams illustrating an example in which the base station apparatus 100 maps reference symbol sequences of different antenna ports for each subframe. Specifically, in FIG. 16A to FIG. 16D, the base station apparatus 100 performs the nth subframe SF (n), the (n + 1) th subframe SF (n + 1), and the (n + 2) th subframe SF (n + 2), respectively. An example in which the reference symbol sequences of antenna port 5 to antenna port 8 are mapped to the (n + 3) th subframe SF (n + 3) is shown. In FIG. 16A to FIG. 16D, reference symbol sequences of antenna ports 5 to 8 are indicated by 5 to 8, respectively, and reference symbols of antenna ports 1 to 4 are indicated by shading. The communication system in the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system in the first embodiment, but the mapping method of the resource element mapping unit is different. Below, it demonstrates centering on a different part from 1st Embodiment.

Base station apparatuses 100 and 101 of the present embodiment further include antenna ports 5 to 8 in addition to antenna ports 1 to 4 included in the first embodiment. In the present embodiment, the resource element mapping units 301 to 30T map one sequence of reference symbol sequences in one resource block, and perform this for each resource block.
The reference signal generation unit 29 generates a 4-chip reference symbol sequence to be assigned to the newly added antenna ports 5 to 8 based on the pseudo noise sequence, and the resource element mapping units 301 to 30T respectively generate the nth reference symbol sequences. To (n + 3) subframes SF (n) to SF (n + 3). The reference signal generation unit 29 uses a sequence having excellent autocorrelation characteristics such as an M sequence as a pseudo noise sequence. Also, base station apparatus 101 uses a series of base station apparatus 100 that is cyclically shifted by one chip as a reference symbol series. Further, the resource element that maps the reference symbol sequence may be shifted between adjacent cells based on the cell ID or the like.

By mapping the reference symbol sequence as shown in FIGS. 16A to 16D, the reference symbol sequence transmitted by the base station apparatus 100 and the reference symbol sequence transmitted by the base station apparatus 101 are different from each other in the sequence peak position and orthogonal to each other. ing. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated. Furthermore, even when an antenna port is newly added, the resource overhead due to the reference symbol can be reduced.
In the above description, the reference symbol sequence based on the pseudo noise sequence is used for all reference symbols of all newly added antenna ports. However, only a part of them may be used. For example, a reference symbol sequence based on a pseudo noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports. . In addition, although the case where the reference symbol sequence based on the pseudo noise sequence is used for all the resource elements that map the reference symbols of the respective antenna ports has been described above, the reference symbols based on the pseudo noise sequence are only part of them. A series may be used.

In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four and may be one or more antenna ports. . Although the case where there are reference symbols for the antenna ports 1 to 4 has been described above, these may not be necessary. In addition, although the case where the reference symbol series is arranged in all the resource blocks has been described above, the reference symbol series may be arranged in only some resource blocks. In the above description, four antenna ports are further added to the four antenna ports 1 to 4. However, the present invention is not limited to this, and one or more antenna ports are provided for one or more antenna ports. Any port may be added. For example, six new antenna ports may be added to the two antenna ports 1 and 2. Alternatively, eight antenna ports may be newly added. Note that the method described in this embodiment may be applied in combination with the method described in the second to third embodiments.

<Fifth Embodiment>
Next, a fifth embodiment of the present invention will be described.
FIGS. 17A to 17D are conceptual diagrams illustrating examples in which the base station apparatus 100 maps reference symbol sequences of different antenna ports for each resource block. Specifically, in FIG. 17A to FIG. 17D, the base station apparatus 100 has the m-th resource block RB (m), the (m + 1) -th resource block RB (m + 1), the (m + 2) -th resource block RB (m + 2), An example in which the reference symbol sequences of antenna port 5 to antenna port 8 are mapped to the (m + 3) th resource block RB (m + 3) is shown. In FIGS. 17A to 17D, reference symbol sequences of antenna ports 5 to 8 are indicated by 5 to 8, respectively, and reference symbols of antenna ports 1 to 4 are indicated by shading. The communication system in the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system in the first embodiment, but the mapping method of the resource element mapping unit is different. Below, it demonstrates centering on a different part from 1st Embodiment.
Base station apparatuses 100 and 101 of the present embodiment further include antenna ports 5 to 8 in addition to antenna ports 1 to 4 included in the first embodiment.
In the present embodiment, the resource element mapping units 301 to 30T map one sequence of reference symbol sequences in one resource block, and perform this for each resource block. In particular, in the present embodiment, one of the reference symbol sequences of antenna ports 5 to 8 is arranged in one subframe, and the antenna ports are periodically arranged in the frequency direction (for each resource block).

The reference signal generator 29 generates a 4-chip reference symbol sequence to be assigned to the newly added antenna ports 5 to 8 based on the pseudo noise sequence, and the resource element mapping units 301 to 30T respectively generate the mth reference symbol sequences. To (m + 3) resource blocks RB (m) to RB (m + 3). The reference signal generation unit 29 uses a sequence having excellent autocorrelation characteristics such as an M sequence as a pseudo noise sequence. Also, base station apparatus 101 uses a series of base station apparatus 100 that is cyclically shifted by one chip as a reference symbol series. Further, the resource element that maps the reference symbol may be shifted between adjacent cells based on the cell ID or the like.
By mapping the reference symbol sequence as shown in FIGS. 17A to 17D, the reference symbol sequence transmitted by the base station apparatus 100 and the reference symbol sequence transmitted by the base station apparatus 101 are different from each other in the sequence peak positions and orthogonal to each other. ing. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated. Furthermore, even when an antenna port is added, resource overhead due to reference symbols can be prevented from increasing.

In addition, although the case where the reference symbol sequence based on the pseudo noise sequence is used for all the reference symbols of all the antenna ports has been described above, only a part of them may be used. For example, a reference symbol sequence based on a pseudo noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports. . In addition, although the case where the reference symbol sequence based on the pseudo noise sequence is used for all the resource elements that map the reference symbols of the respective antenna ports has been described above, it may be used only for some resource elements.
In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four and may be one or more antenna ports. . Although the case where there are reference symbols for the antenna ports 1 to 4 has been described above, these may not be necessary. In the above description, four antenna ports are further added to the four antenna ports 1 to 4. However, the present invention is not limited to this, and one or more antenna ports are provided for one or more antenna ports. Any port may be added. For example, six antenna ports may be newly added to the two antenna ports 1 and 2. Note that the method described in this embodiment may be applied in combination with the methods described in the second to fourth embodiments.

<Sixth Embodiment>
Next, a sixth embodiment of the present invention will be described. FIG. 18 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps reference symbol sequences for one sequence to a plurality of resource blocks in the frequency direction of the nth subframe. In the mth to (m + 3) resource blocks RB (m) to RB (m + 3) in the figure, the reference symbol sequences of the antenna ports 5 to 8 are indicated by 5 to 8, respectively, and the reference symbols of the antenna ports 1 to 4 are the network symbols. Shown with a hanger. The communication system in the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system in the first embodiment, but the mapping method of the resource element mapping unit is different. Below, it demonstrates centering on a different part from 1st Embodiment.
Base station apparatuses 100 and 101 of the present embodiment further include antenna ports 5 to 8 in addition to antenna ports 1 to 4 included in the first embodiment.

FIG. 18 illustrates mapping of reference symbol sequences performed by the base station apparatus 100. The reference signal generation unit 29 generates a reference symbol sequence based on the pseudo noise sequence, and the resource element mapping units 301 to 30T map the reference symbol sequence generated for each subband unit composed of a plurality of resource blocks in the frequency direction. To do. Here, the subband is a resource unit for creating feedback information, and is determined in advance based on the system band or the like. FIG. 18 shows the k-th subband SB (k) including m-th to (m + 3) resource blocks RB (m) to RB (m + 3).
In FIG. 18, the reference signal generation unit 29 generates an 8-chip reference symbol sequence to be assigned to the newly added antenna ports 5 to 8 over four resource blocks based on the pseudo noise sequence. The reference signal generation unit 29 generates a reference symbol sequence using a pseudo noise sequence having excellent autocorrelation characteristics such as an M sequence. Also, base station apparatus 101 uses a series of base station apparatus 100 that is cyclically shifted by one chip as a reference symbol series. Further, the resource element that maps the reference symbol sequence may be shifted between adjacent cells based on the cell ID or the like.

As shown in FIG. 18, by mapping the reference symbol sequence, the reference symbol sequence transmitted from the base station apparatus 100 and the reference symbol sequence transmitted from the base station apparatus 101 are different from each other and orthogonal to each other. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated. Furthermore, even when an antenna port is newly added, the gain due to despreading can be increased without increasing the resource overhead due to the reference symbol. Furthermore, even when a new antenna port is added, the resource overhead due to the reference symbol can be prevented from increasing without reducing the gain due to despreading.

In the above description, the case where the generation and mapping of the reference symbol sequence based on the pseudo noise sequence is performed in subband units composed of a plurality of resource blocks continuous in the frequency direction has been described. The resource block may be included.
In the above description, the case where the generation and mapping of the reference symbol sequence based on the pseudo-noise sequence is performed using four resource blocks in the frequency direction as a unit has been described, but two or more resource blocks may be used as a unit. The mapping may be performed over the carrier element (component carrier) unit or the entire system band. Here, the carrier element has a narrower frequency band (in this embodiment, a bandwidth of 20 MHz) that constitutes a system band (a wideband frequency band having a bandwidth of 100 MHz in this embodiment). Narrow frequency band). Alternatively, a unit in which a specific physical channel (for example, PDCCH (Physical downlink control channel), PUCCH (Physical uplink control channel), etc.) is configured may be used as a carrier element.
In the above description, a case has been described in which a reference symbol sequence is mapped based on a pseudo-noise sequence for a unit composed of a plurality of resource blocks in the frequency direction. Any unit may be used.

In the above description, the reference symbol sequence based on the pseudo noise sequence is used for all reference symbols of the antenna port to be newly added, but only a part of them may be used. A reference symbol sequence based on a pseudo-noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports.
In the above, the case where the reference symbol sequence based on the pseudo noise sequence is used for all the reference symbols for all antenna ports has been described. However, only the reference symbols based on the pseudo noise sequence are used for some reference symbols. Also good. In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four and may be one or more antenna ports. . Although the case where there are reference symbols for the antenna ports 1 to 4 has been described above, these may not be necessary. Although the case where the reference symbol series is arranged in all the resource blocks has been described above, the reference symbol series may be arranged only in some resource blocks.
In the above description, four antenna ports are further added to the four antenna ports 1 to 4. However, the present invention is not limited to this, and one or more antenna ports are provided for one or more antenna ports. Any port may be added. For example, six new antenna ports may be added to the two antenna ports 1 and 2. Note that the method described in this embodiment may be applied in combination with the methods described in the second to fifth embodiments.

<Seventh Embodiment>
Next, a seventh embodiment of the present invention will be described. FIG. 19 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps one sequence of reference symbol sequences to a plurality of resource blocks in the time direction. In the nth to (n + 3) subframes SF (n to SF (n + 3) in the figure, the reference symbol sequences of the antenna ports 5 to 8 are indicated by 5 to 8, respectively, and the reference symbols of the antenna ports 1 to 4 are shaded. The communication system according to the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system according to the first embodiment, but the mapping method of the resource element mapping unit In the following, the description will focus on parts that are different from the first embodiment.
Base station apparatuses 100 and 101 of the present embodiment further include antenna ports 5 to 8 in addition to antenna ports 1 to 4 included in the first embodiment.
The reference signal generation unit 29 generates an 8-chip reference symbol sequence based on the pseudo noise sequence, and the resource element mapping units 301 to 30T map the reference symbol sequence for each of a plurality of resource block units in the time direction.
In FIG. 19, the reference signal generation unit 29 generates an 8-chip reference symbol sequence to be assigned to newly added antenna ports 5 to 8 over four resource blocks based on the pseudo noise sequence. The reference signal generation unit 29 generates a reference symbol sequence using a pseudo noise sequence having excellent autocorrelation characteristics such as an M sequence. Also, base station apparatus 101 uses a series of base station apparatus 100 that is cyclically shifted by one chip as a reference symbol series. Further, the resource element that maps the reference symbol may be shifted between adjacent cells based on the cell ID or the like.

As shown in FIG. 19, by mapping the reference symbol sequence, the reference symbol sequence transmitted by the base station apparatus 100 and the reference symbol sequence transmitted by the base station apparatus 101 are different from each other and orthogonal to each other. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated. Furthermore, even when an antenna port is newly added, the gain due to despreading can be increased without increasing the resource overhead due to the reference symbol. Furthermore, even when a new antenna port is added, the resource overhead due to the reference symbol can be prevented from increasing without reducing the gain due to despreading.

In the above description, the case where the generation and mapping of the reference symbol sequence based on the pseudo-noise sequence is performed in units composed of a plurality of resource blocks continuous in the time direction has been described. Blocks may be included.
In the above description, the case where the generation and mapping of the reference symbol sequence based on the pseudo-noise sequence is performed in units of four resource blocks in the time direction has been described, but two or more resource blocks may be used as a unit. For example, a radio frame (10 subframes) unit composed of 10 milliseconds, or a unit in which a specific physical channel (broadcast information channel (BCH; Broadcast channel), synchronization signal (synchronization channel), etc.) is configured or assigned May be used.
In the above description, the case where the reference symbol sequence is mapped based on the pseudo-noise sequence to the unit configured by a plurality of resource blocks in the time direction has been described. However, one or more OFDM symbols in the time direction have been described. Any unit may be used.

In the above description, the reference symbol sequence based on the pseudo noise sequence is used for all reference symbols of the antenna port to be newly added, but only a part of them may be used. A reference symbol sequence based on a pseudo-noise sequence may be assigned to a reference symbol in one antenna port, and a reference symbol generated from a random number based on a cell ID may be assigned to reference symbols in the remaining antenna ports.
In the above description, the reference symbol sequence based on the pseudo noise sequence is used for all the reference symbols for all antenna ports. However, only the reference symbol sequence based on the pseudo noise sequence is used for some reference symbols. May be.
In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four and may be one or more antenna ports. . Although the case where there are reference symbols for the antenna ports 1 to 4 has been described above, these may not be necessary. Although the case where the reference symbol series is arranged in all the resource blocks has been described above, the reference symbol series may be arranged only in some resource blocks. In the above description, four antenna ports are further added to the four antenna ports 1 to 4. However, the present invention is not limited to this, and one or more antenna ports are provided for one or more antenna ports. Any port may be added. For example, six new antenna ports may be added to the two antenna ports 1 and 2. Note that the method described in this embodiment may be applied in combination with the methods described in the second to sixth embodiments.

<Eighth Embodiment>
Next, an eighth embodiment of the present invention will be described. FIG. 20 is a conceptual diagram illustrating an example in which the base station apparatus 100 maps one series of reference symbol sequences to a plurality of antenna ports. In the figure, reference symbol sequences of antenna ports 5 to 8 are indicated by 5 to 8, respectively, and reference symbols of antenna ports 1 to 4 are indicated by shading. The communication system in the present embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system in the first embodiment, but the mapping method of the resource element mapping unit is different. Below, it demonstrates centering on a different part from 1st Embodiment.
Base station apparatuses 100 and 101 of the present embodiment further include antenna ports 5 to 8 in addition to antenna ports 1 to 4 included in the first embodiment.
The reference signal generation unit 29 generates an 8-chip reference symbol sequence based on the pseudo noise sequence, and the resource element mapping units 301 to 30T reference within the same resource block over the four antenna ports of the antenna ports 5 to 8. A symbol series is assigned and this is repeated for each resource block.
In FIG. 20, the reference signal generation unit 29 generates an 8-chip reference symbol sequence to be allocated over the four newly added antenna ports 5 to 8 based on the pseudo noise sequence. The reference signal generation unit 29 generates a reference symbol sequence using a pseudo noise sequence having excellent autocorrelation characteristics such as an M sequence. Also, base station apparatus 101 uses a series of base station apparatus 100 that is cyclically shifted by one chip as a reference symbol series. Further, the resource element that maps the reference symbol may be shifted between adjacent cells based on the cell ID or the like.

As shown in FIG. 20, by mapping the reference symbol sequence, the reference symbol sequence transmitted by the base station device 100 and the reference symbol sequence transmitted by the base station device 101 are different from each other and orthogonal to each other. Thereby, the mobile terminal apparatus 150 that simultaneously receives transmission signals from the base station 100 and the base station 101 and performs cooperative communication can suppress interference from adjacent cells by performing despreading, and perform cooperative communication. It is possible to estimate the optimum feedback information for performing. Also, the mobile terminal device 151 that does not perform cooperative communication increases new processing by using each chip independently without performing despreading processing, even if the reference symbol sequence is based on a pseudo-noise sequence. And optimal feedback information can be estimated. Furthermore, even when an antenna port is newly added, the gain due to despreading can be increased without increasing the resource overhead due to the reference symbol. Furthermore, even when a new antenna port is added, the resource overhead due to the reference symbol can be prevented from increasing without reducing the gain due to despreading.

In the above, the case where the reference symbol sequence based on the pseudo noise sequence is used for all the resource elements that map the reference symbols across all antenna ports has been shown, but the pseudo noise sequence is applied only to some of the reference symbols. A reference symbol sequence based on the above may be used.
In addition, although the case where the number of antenna ports to be newly added is four in the base station apparatuses 100 and 101 has been described above, the number of antenna ports to be added is not limited to four, and may be two or more antenna ports. . Although the case where there are reference symbols for the antenna ports 1 to 4 has been described above, these may not be necessary. Although the case where the reference symbol series is arranged in all the resource blocks has been described above, the reference symbol series may be arranged only in some resource blocks. Although the case where four antenna ports are added to the four antenna ports 1 to 4 has been described above, the present invention is not limited to this. For example, six new antenna ports may be added to the two antenna ports 1 and 2. Note that the method described in this embodiment may be applied in combination with the methods described in the second to seventh embodiments.

<Ninth Embodiment>
Next, a ninth embodiment of the present invention will be described. In the present embodiment, base station apparatuses 100 and 101 map reference symbol sequences based on orthogonal code sequences.
FIG. 21A is a conceptual diagram illustrating an example of a reference symbol sequence based on an orthogonal code sequence used by the base station apparatuses 100 and 101 for the antenna port 1. The code C1 in the figure is a reference symbol sequence used by the base station apparatus 100 for the antenna port 1, and the code C2 is a reference symbol series used by the base station apparatus 101 for the antenna port 1.
FIG. 21B is a conceptual diagram illustrating an example of a reference symbol sequence based on an orthogonal code sequence used by the base station apparatuses 100 and 101 for the antenna port 2. The reference symbol C1 ′ in the figure is a reference symbol sequence used by the base station device 100 for the antenna port 2, and the reference symbol C2 ′ is a reference symbol sequence used by the base station device 101 for the antenna port 2.

FIG. 21C is a conceptual diagram illustrating an example in which the base station apparatus 100 maps a reference symbol sequence. In the figure, reference symbol sequences of antenna ports 1 and 2 of base station apparatus 100 are indicated by a to d and i to l, respectively. FIG. 21D is a conceptual diagram illustrating an example in which the base station apparatus 101 maps reference symbol sequences. In the figure, reference symbol sequences of antenna ports 1 and 2 of the base station apparatus 101 are indicated by e to h and m to p, respectively.
The communication system according to the ninth embodiment includes base station apparatuses 100 and 101 and mobile terminal apparatuses 150 and 151 similar to the communication system according to the first embodiment, but performs mapping with the mapping method of the resource element mapping unit. The series is different. Below, it demonstrates centering on a different part from 1st Embodiment. In this embodiment, antenna ports 1 and 2 are used.

In FIG. 21C and FIG. 21D, reference symbol sequences (4 chips) assigned to newly added antenna ports 1 to 2 across four resource blocks are orthogonal code sequences (cross-correlation characteristics) such as OVSF (OrthogonalthoVariable Spreading Factor) codes. This is a case where it is generated on the basis of an excellent series. Base station apparatuses 100 and 101 use abcd (orthogonal code C1) and efgh (orthogonal code C2) orthogonal to each other as orthogonal codes used for antenna port 1, and ijkl (orthogonal to each other) as orthogonal codes used for antenna port 2. Orthogonal code C1 ′) and mnop (orthogonal code C2 ′) are used. The same code set may be used as the set of orthogonal codes C1 and 2 and the set of orthogonal codes C1 'and 2'. Specifically, a set of orthogonal codes C1 and 2 and a set of orthogonal codes C1 ′ and 2 ′ are set from the 4-chip OVSF sequences 1111, 11-1-1, 1-1-11, and 1-11-1. You may do it. Sequences orthogonal to each other are used between adjacent base station apparatuses (cells). Further, the orthogonal relationship can be maintained by making the resource elements for mapping the reference symbol sequence the same between adjacent cells. At this time, the power (or amplitude) of the reference symbol mapped to each resource element is preferably the same as the power (or amplitude) of the data symbol mapped to the resource element of the data part.

By mapping reference symbol sequences as shown in FIG. 21C and FIG. 21D, mobile terminal apparatuses 150 that simultaneously receive transmission signals from base station 100 and base station 101 and perform coordinated communication perform despreading, respectively. Signal power (signal amplitude) from each base station can be measured while eliminating interference from neighboring cells, and optimal feedback for cooperative communication from the signal power (signal amplitude) obtained by each base station Information (CQI and PMI based on total SINR and total SINR, SINR in each base station, CQI and PMI based on SINR in each base station, and the like) can be estimated.
In addition, the mobile terminal device 151 that does not perform cooperative communication refers to the reference symbol sequence transmitted from the base station device (own base station, own cell, serving cell) 100 that performs communication, and receives the received reference symbol sequence. By performing despreading, the signal power (signal amplitude) obtained from the base station apparatus 100 can be measured while removing interference from adjacent cells. Further, since each reference symbol sequence chip includes an interference component from an adjacent base station, the reference symbol sequence is mapped to the resource element to which the reference symbol sequence is mapped (the amplitude and reception of the reference signal from the own base station). The average interference signal power can be obtained by calculating the square norm of the signal and the difference, and optimum feedback information (such as CNR and PMI based on SINR and SINR) can be estimated.

Thus, a communication system in which one base station apparatus 100 and at least one mobile terminal apparatus 151 communicate with each other, and a plurality of base station apparatuses 100 and 101 communicate with each other in cooperation with at least one mobile terminal apparatus 150. The base station apparatus 100 generates a reference symbol sequence shared by both the mobile terminal apparatus 150 that performs cooperative communication and the mobile terminal apparatus 151 that does not perform cooperative communication, and maps the reference symbol to one of the resource elements. Base station apparatuses 100 and 101 use sequences orthogonal between base station apparatuses as reference symbol sequences, and map reference symbol sequences to the same resource elements between base station apparatuses. The mobile terminal device 151 that communicates with one base station device 100 uses the reference symbol sequence transmitted by the communication partner base station device 100 to measure the state of the transmission path for notifying the communication partner base station device 100. . Further, mobile terminal apparatus 150 that communicates in cooperation with a plurality of base station apparatuses 100 and 101 notifies each of base station apparatuses 100 and 101 from a reference symbol sequence transmitted by each of a plurality of base station apparatuses 100 and 101. Measure the transmission path conditions for As a result, the mobile terminal device 150 that performs cooperative communication and the mobile terminal device 151 that does not perform cooperative communication use the same reference symbol sequence, and the mobile terminal device 150 that performs cooperative communication transmits signals from the base station devices 100 and 101. The mobile terminal apparatus 151 that can accurately grasp the transmission signal power and does not perform cooperative communication accurately grasps the transmission signal power from the own base station apparatus 100 and also averages the interference signal from the adjacent base station apparatus 101. Electric power can be obtained. Accordingly, the mobile terminal apparatus 100 that performs cooperative communication and the mobile terminal apparatus 101 that does not perform cooperative communication can generate optimal feedback information while sharing the reference symbol sequence and suppressing overhead.

A program for realizing the functions of all or part of base station apparatus 100 in FIG. 4 and all or part of mobile station apparatus 150 in FIG. 6 is recorded on a computer-readable recording medium. Processing of each unit may be performed by causing a computer system to read and execute a program recorded on a recording medium. The “computer system” here includes an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM or a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

The present invention is suitable for use in a wireless communication system, a wireless communication apparatus, and a wireless communication method.

21, 511 to 51 R ... wireless receiver 22 ... received signal processor 23 ... feedback information processor 241 to 24L ... encoder 251 to 25L ... scrambler 261 to 26L ... modulator 27 ... layer mapping part 28 ... precoding part 29 ... reference signal generators 301 to 30T ... resource element mapping units 311 to 31T ... OFDM signal generators 321 to 32T, 63 ... radio transmitters 521 to 52R ... OFDM signal demodulators 531 to 53R ... resource element demapping unit 54 ... propagation Path estimation unit 55 ... filter unit 56 ... deprecoding unit 57 ... layer demapping units 581 to 58L ... demodulation units 591 to 59L ... descrambling units 601 to 60L ... decoding unit 61 ... feedback information generation unit 62 ... transmission signal generation unit 63 ... wireless transmitters 100, 101 ... Chikyoku device 150 and 151 ... mobile terminal device 900 ... communication system

Claims (12)

  1. A reference signal generation unit that generates a reference symbol sequence on the transmission side that is a sequence of reference symbols based on a pseudo-noise sequence;
    A resource element mapping unit that maps transmission data and the transmission side reference symbol sequence to one or more resource elements for each of one or more symbols;
    A first radio transmission unit that generates and transmits a transmission signal of a radio signal indicating the transmission data and the transmission-side reference symbol sequence according to the mapping;
    A first radio reception unit that receives feedback information based on a signal reception state of the reference symbol;
    A first communication device comprising: a feedback information processing unit that controls a transmission mode of the transmission data based on the feedback information;
    A second wireless receiver for receiving the wireless signal;
    A feedback information generator for measuring a signal reception state from the first communication device based on a reference symbol sequence extracted from the received radio signal, and generating the feedback information according to the measured signal reception state;
    A second communication device including: a second wireless transmission unit that transmits the feedback information.
  2. A third wireless receiver for receiving the transmission signal;
    Feedback information generation for measuring a signal reception state from the first communication device based on a reference symbol included in a de-spread reference symbol sequence extracted from the transmission signal, and generating feedback information according to the measured signal reception state And
    The communication system according to claim 1, further comprising: a third communication device including a third wireless transmission unit that transmits the feedback information.
  3. A plurality of the first communication devices;
    2. The communication system according to claim 1, wherein resource element mapping units of the plurality of first communication devices map a transmission-side reference symbol sequence to the same resource element for each symbol.
  4. The communication system according to claim 3, wherein the transmission side reference symbol sequence generated by the reference signal generation unit is orthogonal to a transmission side reference symbol sequence of another first communication apparatus.
  5. A plurality of the first communication devices;
    The communication system according to claim 1, wherein the transmission side reference symbol sequences generated by the reference signal generation units of the plurality of first communication devices are cyclically shifted from each other.
  6. A plurality of the first communication devices;
    The communication system according to claim 1, wherein resource element mapping units of the plurality of first communication devices map the reference symbols to different resource elements.
  7. A reference signal generation unit that generates a reference symbol sequence on the transmission side that is a sequence of reference symbols based on a pseudo-noise sequence;
    A resource element mapping unit that maps transmission data and the transmission side reference symbol sequence to one or more resource elements for each of one or more symbols;
    A radio transmission unit that generates and transmits a radio signal indicating the transmission data and the transmission-side reference symbol sequence according to the mapping;
    A first radio reception unit that receives feedback information based on a signal reception state of the reference symbol;
    A feedback information processing unit that controls a transmission method of the transmission data based on the feedback information.
  8. A radio reception unit that receives a radio signal indicating a transmission-side reference symbol sequence via a propagation path;
    A feedback information generation unit that measures a signal reception state based on a reference symbol sequence extracted from the received radio signal, and generates the feedback information according to the measured signal reception state;
    And a wireless transmission unit that transmits the feedback information.
  9. In the communication system in which the first communication device and the second communication device perform wireless communication,
    A reference signal generating step in which the first communication device generates a transmitting-side reference symbol sequence that is a sequence of reference symbols based on a pseudo-noise sequence;
    A resource element mapping process in which the first communication device maps transmission data and the transmission side reference symbol sequence to one or more resource elements for each of one or more symbols;
    A first radio transmission process in which the first communication device generates and transmits a radio signal indicating the transmission data and the reference symbol sequence on the transmission side according to the mapping;
    A first wireless reception process in which the first communication device receives feedback information based on a signal reception state of the reference symbol;
    A feedback information processing process in which the first communication apparatus controls a transmission method of the transmission data based on the feedback information; a second radio reception process in which the second communication apparatus receives the radio signal;
    Feedback information for measuring a signal reception state from the first communication device based on a reference symbol sequence extracted from the radio signal received by the second communication device, and generating the feedback information according to the measured signal reception state Generation process,
    A second wireless transmission process in which the second communication device transmits the feedback information.
  10. In the communication system in which the second communication device communicates with the first communication device, and the third communication device communicates with the first communication device,
    A reference signal generating step in which the first communication device generates a transmitting-side reference symbol sequence that is a sequence of reference symbols based on a pseudo-noise sequence;
    A resource element mapping process in which the first communication device maps transmission data and the transmission side reference symbol sequence to one or more resource elements for each of one or more symbols;
    A first radio transmission process in which the first communication device generates and transmits a radio signal indicating the transmission data and the reference symbol sequence on the transmission side according to the mapping;
    A first wireless reception process in which the first communication device receives feedback information based on a signal reception state of the reference symbol;
    A feedback information processing process in which the first communication apparatus controls a transmission method of the transmission data based on the feedback information; a second radio reception process in which the second communication apparatus receives the radio signal;
    Feedback information for measuring a signal reception state from the first communication device based on a reference symbol sequence extracted from the radio signal received by the second communication device, and generating the feedback information according to the measured signal reception state Generation process,
    A second wireless transmission process in which the second communication device transmits the feedback information; and a third wireless reception process in which the third communication device receives the transmission signal;
    A feedback information generating step in which the third communication device measures a signal reception state from the first communication device based on a reference symbol extracted from the transmission signal, and generates feedback information according to the measured signal reception state;
    A third wireless transmission process in which the third communication device transmits the feedback information.
  11. A reference signal generation process in which the communication device generates a reference symbol sequence on the transmission side that is a sequence of reference symbols based on a pseudo-noise sequence;
    A resource element mapping process of mapping transmission data and the transmission side reference symbol sequence to one or more resource elements for each of one or more symbols;
    A radio transmission process of generating and transmitting a radio signal indicating the transmission data and the transmission side reference symbol sequence according to the mapping;
    A radio reception process for receiving feedback information based on a signal reception state of the reference symbol;
    A feedback information processing step for controlling a transmission method of the transmission data based on the feedback information.
  12. A radio reception process in which a communication device receives a radio signal indicating a transmission-side reference symbol sequence via a propagation path;
    A feedback information generation step of measuring a signal reception state based on a reference symbol sequence extracted from the radio signal received by the communication device, and generating the feedback information according to the measured signal reception state;
    A wireless transmission process in which the communication device transmits the feedback information.
PCT/JP2010/002748 2009-04-24 2010-04-15 Communication system, communication apparatus and communication method WO2010122749A1 (en)

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