JP2013229661A - Communication system, communication method, base station apparatus, and mobile station apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system which can efficiently improve the throughput of a mobile station apparatus existing in a base station apparatus (especially a mobile station apparatus existing at a cell end) and a communication method, a base station apparatus, and a mobile station apparatus.SOLUTION: A high order layer 101 controls transmission power on the basis of propagation path information and determines whether its transmitted data has interferences suppressed by mutual cooperation between each base station apparatus. A weighting coefficient control unit 105 uses the propagation path information obtained from the high order layer 101 to calculate a transmission weighting coefficient Vby which signals transmitted by a master base station apparatus and a slave base station apparatus are to be multiplied and a reception weighting coefficient Uby which reception signals received by mobile station apparatuses connected to each base station apparatus are to be multiplied. In other words, the weighting coefficient control unit 105 uses the propagation path information of the entire system to calculate transmission and reception weighting coefficients. A precoding unit 104 multiplies the modulation symbol output by a modulation unit 103 by a transmission weighting coefficient V.

Description

  The present invention relates to a communication system, a communication method, a base station apparatus, and a mobile station apparatus.

  In wireless communication systems such as mobile phones and wireless LANs, a plurality of base station apparatuses (eNBs; eNodeBs) and the like are arranged in a cellular configuration in order to expand a communication area. A range (communication service area) in which each base station apparatus can be connected to a mobile station apparatus (UE; User Equipment) is called a cell.

  In recent years, with an increase in traffic volume due to an increase in large-capacity services and the like, it is required to increase the transmission rate, increase system throughput, and distribute traffic in a wireless communication system. As a method for these requests, a part or all of the range of the macro cell formed by the main base station apparatus (macro base station) and a small power base station (pico cell base station, femto cell base having a maximum transmission power smaller than that of the macro base station) It has been proposed to arrange a plurality of base station apparatuses so as to overlap the cell range of a station etc. (heterogeneous network, Non-Patent Document 1). A mobile station apparatus (UE; User Equipment) is connected to a base station apparatus in which received power and SINR (Signal to Interference and Noise Ratio) increase among these base station apparatuses, thereby increasing the transmission rate and system. Increased throughput and traffic distribution can be expected.

  On the other hand, in the downlink of a heterogeneous network, inter-cell interference becomes a problem due to a signal transmitted from a macro base station to a mobile station apparatus connected to a picocell base station. As a method of suppressing and reducing this inter-cell interference, a method of scheduling transmission frame allocation of transmission signals in cooperation between a plurality of base station apparatuses is disclosed (Non-Patent Document 2).

  Specifically, when the pico cell base station apparatus allocates information data of a mobile station apparatus connected to the own station to a transmission frame (subframe), the macro cell base station apparatus transmits in synchronization with a transmission frame in which no information data is arranged. Information data of the mobile station apparatus that receives inter-cell interference from the macro cell base station apparatus is assigned to the frame. Thereby, the picocell base station apparatus can reduce the inter-cell interference received from the macrocell base station apparatus. For this reason, in the heterogeneous network, it is possible to improve the throughput as viewed from the network side in the area covered by the macro cell.

3rd Generation Partnership Project; Technical Specification Group Radio Access Network; 3rd Generation Advances for E-UTRA Physical Layer. (2010-03) URL: http://www.3gpp.org/ftp/Specs/html-info/36814.htm R1-105442, 3GPP TSG RAN WG1 Meeting # 62bis

  However, in the method of suppressing and reducing inter-cell interference described in Non-Patent Document 2, the transmission frame to which the picocell base station apparatus is assigned a mobile station apparatus connected to the base station apparatus is limited. For this reason, there is a problem that the system throughput cannot be sufficiently improved. In addition, when inter-cell interference occurs between picocell base station apparatuses, the SINR of the mobile station apparatus connected to the base station apparatus decreases.

  The present invention has been made in view of the above circumstances, and a communication system capable of efficiently improving the throughput of a mobile station apparatus (particularly, a mobile station apparatus existing at a cell edge) existing in a base station apparatus, It is an object of the present invention to provide a communication method, a base station apparatus, and a mobile station apparatus.

  In order to solve the above-described problem, each configuration of a communication system, a communication method, a base station apparatus, and a mobile station apparatus according to the present invention is as follows.

The present invention comprises a plurality of base station devices and a mobile station device connected to at least one of the plurality of base station devices, wherein the plurality of base station devices are all within a connectable range of each base station device. Alternatively, it is a communication system that is arranged so that some overlap each other,
The plurality of base station devices include a master base station device and a slave base station device,
The main base station apparatus, a power control unit that controls transmission power of the plurality of base station apparatuses,
For transmission data transmitted by the plurality of base station apparatuses, a transmission mode for selecting a transmission mode including a cooperative mode in which the plurality of base station apparatuses and a mobile station apparatus connected to the base station apparatus cooperate to suppress interference is selected. A transmission weighting factor for multiplying transmission data transmitted by the plurality of base station devices in order for the determination unit, the plurality of base station devices and the mobile station device connected to the base station device to cooperate and suppress interference A weighting factor control unit for calculating,
The plurality of base station apparatuses include a precoding unit that multiplies the transmission data by the transmission weight coefficient.

  Further, in the communication system according to the present invention, the weight coefficient control unit is configured so that the plurality of base station apparatuses cooperate with each other and the mobile station apparatus connected to the base station apparatus to suppress interference. The mobile station apparatus that has received the transmission data to be transmitted calculates a reception weighting coefficient by which the received signal is multiplied, and the plurality of base station apparatuses obtain information data obtained by multiplying the transmission data by the transmission weighting coefficient. A transmission unit for transmitting to the mobile station device connected to each of the station devices, the mobile station device multiplying the reception weight coefficient by the reception signal, and an interference suppression unit for acquiring the information data It is characterized by providing.

  In the communication system of the present invention, the transmission mode determination unit selects the cooperative mode comprehensively for the plurality of base station apparatuses.

  In the communication system of the present invention, the main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and the power control unit is greater than a predetermined threshold among the propagation path state information. When there is a base station apparatus of propagation path state information, it is notified that the transmission power of a plurality of base station apparatuses that have acquired propagation path state information is increased, and when there is a notification that the transmission power is increased, Selecting a cooperative mode.

  In the communication system of the present invention, the main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and the power control unit is greater than a predetermined threshold among the propagation path state information. When there is a base station apparatus of propagation path state information, it is notified that the transmission power of the base station apparatus is increased, and when there is a notification that the transmission power is increased, the cooperative mode is selected. Features.

  In the communication system of the present invention, the transmission mode determination unit selects the cooperative mode when there is a base station apparatus in which the transmission power output from the power control unit is greater than a predetermined threshold. To do.

  Further, in the communication system of the present invention, the main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and when there is a case where the propagation path state information is larger than a predetermined threshold, the cooperation Selecting a mode.

  Further, in the communication system of the present invention, the transmission mode determination unit suppresses interference in cooperation with the plurality of base station apparatuses and the mobile station apparatus connected to the base station apparatus for each of the plurality of base station apparatuses. Selecting a cooperative mode.

  In the communication system of the present invention, the main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and the power control unit is greater than a predetermined threshold among the propagation path state information. When there is a base station apparatus of propagation path state information, it is notified that the transmission power of a plurality of base station apparatuses that have acquired propagation path state information is increased, and when there is a notification that the transmission power is increased, Selecting a cooperative mode.

  In the communication system of the present invention, the main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and the power control unit is greater than a predetermined threshold among the propagation path state information. When there is a base station apparatus of propagation path state information, it is notified that the transmission power of the base station apparatus is increased, and when there is a notification that the transmission power is increased, the cooperative mode is selected. Features.

  In the communication system of the present invention, the transmission mode determination unit selects the cooperative mode for the base station device when there is a base station device in which the transmission power output from the power control unit is greater than a predetermined threshold. It is characterized by doing.

  In the communication system of the present invention, the main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and when there is a case where the propagation path state information is greater than a predetermined threshold, Selecting the cooperative mode of the station device.

Further, the present invention includes a plurality of base station devices and a mobile station device connected to at least one of the plurality of base station devices, and the plurality of base station devices can be connected to each base station device. A communication method in a communication system arranged so that all or a part of each overlaps each other,
The plurality of base station devices include a master base station device and a slave base station device,
The main base station apparatus is connected to the plurality of base station apparatuses and the base station apparatus for a power control step for controlling transmission power of the plurality of base station apparatuses and transmission data transmitted by the plurality of base station apparatuses. A transmission mode determination step of selecting a transmission mode including a cooperative mode in which the mobile station apparatuses cooperatively suppress interference, and the plurality of base station apparatuses and the mobile station apparatus connected to the base station apparatus cooperate in interference. A weighting factor control step for calculating a transmission weighting factor for multiplying transmission data transmitted by the plurality of base station devices to suppress transmission, and
The plurality of base station apparatuses include a precoding step of multiplying the transmission data by the transmission weight coefficient.

Further, the present invention includes a plurality of base station devices and a mobile station device connected to at least one of the plurality of base station devices, and the plurality of base station devices can be connected to each base station device. A base station apparatus of a communication system arranged so that all or part of each overlaps each other,
The plurality of base station devices include a master base station device and a slave base station device,
The main base station device is connected to the plurality of base station devices and the base station device for a power control unit that controls transmission power of the plurality of base station devices, and transmission data transmitted by the plurality of base station devices. A transmission mode determining unit that selects a transmission mode including a cooperative mode in which the mobile station apparatuses cooperate to suppress interference, and the mobile station apparatuses connected to the plurality of base station apparatuses and the base station apparatus cooperate in interference. A weighting factor control unit that calculates a transmission weighting factor by which transmission data transmitted by the plurality of base station apparatuses is multiplied.

The present invention comprises a plurality of base station devices and a mobile station device connected to at least one of the plurality of base station devices, wherein the plurality of base station devices are all within a connectable range of each base station device. Alternatively, it is a mobile station device of a communication system that is arranged so that some of them overlap each other,
The mobile station apparatus connected to the base station apparatus is configured to multiply the received signal by the mobile station apparatus that has received transmission data transmitted by the plurality of base station apparatuses so that the base station apparatus cooperates to suppress interference. An interference suppression unit that obtains the information data by multiplying the reception signal by the reception weight coefficient when the reception weight coefficient is calculated and transmitted.

  According to the present invention, in a communication system including a plurality of base station devices and a mobile station device connected to at least one of the plurality of base station devices, the plurality of base station devices use the same frequency band. When communicating with the mobile station apparatus, the mobile station apparatus can receive signals with high received power, and a plurality of base station apparatuses and mobile station apparatuses can cooperate to suppress inter-cell interference. For this reason, the said communication system can have the outstanding effect that a system throughput can be improved.

It is the schematic which shows the cellular structure of the communication system 1 which concerns on the 1st Embodiment of this invention. It is the schematic which shows the connection condition and propagation path condition of the downlink of the communication system 1 which concern on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the master base station apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the one aspect | mode of transmission power control. It is a conceptual diagram which shows an example of the format of the control signal which a control signal generation part outputs. Weighting control unit is a flow chart showing an example of a process for calculating the transmission weight factor V _j and reception weighting factors U _k. It is a block diagram which shows the structure of the slave base station apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the mobile station apparatus which concerns on 1st Embodiment. FIG. 6 is a sequence diagram illustrating an operation example in which a master base station device of the communication system 1 calculates a transmission weight coefficient V _j and a reception weight coefficient U _k and notifies the slave base station device and a mobile station device. It is a flowchart which shows the one aspect | mode of transmission power control in the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment>
In the communication system 1 according to the first embodiment, an example in which the base station apparatus 100-j and the mobile station apparatus 200-k perform data transmission using an OFDM (Orthogonal Frequency Division Multiplexing) scheme. explain. The present embodiment is not limited to this, but other transmission schemes, for example, SC-FDMA (single carrier-frequency division multiple access; single carrier frequency division multiple access), DFT-s-OFDM (discrete Fourier transform-spread). A single carrier transmission scheme such as OFDM (Discrete Fourier Transform Spread OFDM) or a multicarrier transmission scheme such as MC-CDMA (Multiple Carrier-Code Division Multiple Access) may be used. Further, as examples of the communication system 1 according to the first embodiment, WCDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), LTE-I (E), and LTE-A (E), LTE-E (E) and LTE-E (E). Including, but not limited to, a wireless communication system such as WiMAX (World Wide Interoperability Access) by (The Institute of Electrical and Electronics Engineers).

  FIG. 1 is a schematic diagram showing a cellular configuration of a communication system 1 according to the first embodiment of the present invention. The communication system 1 according to the first embodiment includes a plurality of base station devices 100-j (j is an arbitrary positive integer, j = 1 to 3 in FIG. 1) and a plurality of mobile station devices 200. −k (k is an arbitrary positive integer, and k = 1 to 3 in FIG. 1).

  Each base station apparatus 100-j is arranged in such a configuration that its own cell (100-ja) overlaps the entire area or a part of a cell of another base station apparatus. The base station apparatuses 100-j are connected by backhaul lines 10-1, 10-2, 10-3 (for example, X2 interface) using optical fibers, Internet lines, radio lines, or the like. The communication system 1 uses so-called one-cell frequency repetition that uses the same frequency in all cells.

  FIG. 2 is a schematic diagram showing a downlink connection situation / propagation path situation of the communication system 1 according to the first embodiment of the present invention. The base station apparatus 100-j and the mobile station apparatus 200-k in FIG. 2 correspond to the base station apparatus 100-j and the mobile station apparatus 200-k in FIG.

A _space between the base station apparatus 100-j and the mobile station apparatus 200-k is represented by each propagation path H _kj (transfer function) (k and j are arbitrary positive integers. In FIG. 3 and j = 1 to 3). Here, the propagation path H _kj between the base station apparatus and the mobile station apparatus to be coordinated is called a propagation path of the entire system. In the communication system 1, the mobile station device 200-k is wirelessly connected to the base station device 100-j where k = j. That is, in the mobile station apparatus 200-k, a signal transmitted from the base station apparatus 100-j where k ≠ j is inter-cell interference.

For example, the mobile station device 200-1, transmission signal from the base station apparatus 100-1 which receives through the channel _{H 11} is the desired signal, received through the channel _{H 12} and the channel _{H 13} base Transmission signals from the station apparatus 100-2 and the base station apparatus 100-3 become inter-cell interference (undesired signal).

  As will be described in detail later, each base station apparatus 100-j controls the power of the transmission signal. And as for the said transmission signal power, the transmission power is set based on the interference suppression which the base station apparatus 100-j and the mobile station apparatus 200-k cooperated with each other.

When each base station apparatus 100-j is set to a mode in which interference is suppressed in cooperation with each other (cooperative mode), the base station apparatus 100-j and the mobile station apparatus 200-k are included in the transmission signal transmitted by itself. In cooperation, multiplication is performed by a transmission weight coefficient V _j that can suppress interference given to each other. Further, the mobile station apparatus 200-k, the base station apparatus 100-j and the mobile station apparatus 200-k is in concert, to multiply the received signal reception weighting coefficient U _k that can suppress interference with each other.

  Hereinafter, in the communication system 1 of FIG. 2, the base station device 100-1 is a main base station device (master base station device) that calculates a transmission weight coefficient and a reception weight coefficient, and the base station device 100-2 and the base station device. Reference numeral 100-3 denotes a slave base station device (slave base station device) that operates cooperatively according to an instruction from the master base station device.

  Next, the master base station apparatus (base station apparatus 100-1) according to the first embodiment will be described.

  As shown in FIG. 3, the master base station apparatus (base station apparatus 100-1) includes an upper layer 101, an encoding unit 102, a modulation unit 103, a precoding unit 104, a weight coefficient control unit 105, and a reference signal generation unit 106. , Control signal generation unit 107, power setting unit 108, resource mapping unit 109, power adjustment unit 110, IDFT unit 111, GI insertion unit 112, transmission unit 113, transmission antenna unit 114, reception antenna unit 121, reception unit 122, control A signal detection unit 123 is provided. When a part or all of the base station device 100-1 is formed into a chip to form an integrated circuit, a chip control circuit (not shown) for controlling each functional block is provided.

  The base station apparatus 100-1 receives a signal including a control signal such as propagation path information transmitted by the mobile station apparatus 200-1 via the uplink via the reception antenna unit 121. The control signal can include a parameter related to a parameter of a transmission signal transmitted by the base station apparatus, such as a transmission mode switching request. The transmission mode includes a mode determined by whether or not coordinated interference suppression control is performed, a mode defined by parameters such as the number of spatial multiplexing (rank number) of signals that can be received by the mobile terminal, and the number of antennas.

  Further, the signal received by base station apparatus 100-1 includes a reference signal. The reference signal may be LTE, LTE-A Sounding Reference signal, or the like.

  The receiving unit 122 down-converts (radio frequency conversion) the control signal or the like into a frequency band in which digital signal processing such as signal detection processing is possible, and further performs filtering processing to remove spurious signals, and the filtered signal is converted into an analog signal. To digital signal (Analog to Digital conversion).

  The control signal detection unit 123 performs demodulation processing, decoding processing, and the like on the signal output from the reception unit 122 to detect a control signal. The control signal is detected from an uplink control channel (PUCCH), an uplink shared channel (PUSCH), or the like.

  The upper layer 101 acquires channel state information (CSI: Channel State Information) included in the control signal input from the control signal detection unit 123. For example, as channel state information, a channel quality indicator (CQI: Channel Quality Indicator), explicit channel state information (Explicit CSI), or the like can be applied.

For example, as the propagation path status information, the upper layer 101 includes propagation path information H ₁₁ between the base station apparatus 100-1 and the mobile station apparatus 200-1 included in the control signal input from the control signal detection unit 123, the base station Propagation path information H ₁₂ between device 100-2 and mobile station apparatus 200-1 and propagation path information H ₁₃ between base station apparatus 100-3 and mobile station apparatus 200-1 are acquired.

  Further, as the propagation path status information, the upper layer 101 acquires direct or indirect information of the received field strength information and SINR information of the mobile station apparatus included in the control signal input from the control signal detection unit 123.

  Further, the upper layer 101 can also acquire information related to parameters of the transmission signal transmitted by the base station apparatus, such as a transmission mode switching request included in the control signal input from the control signal detection unit 123. Here, the upper layer is a layer of functions higher than the physical layer (physical layer) among the layers of communication functions defined in the OSI reference model, for example, a data link layer, a network layer, and the like.

  Further, the upper layer 101 transmits a channel state information (CSI) from the slave base station devices (base station device 100-2 and base station device 100-3) through the backhaul lines 10-1 and 10-2. To get.

For example, the upper layer 101, (information on the propagation path _{H 21)} channel quality indicator between the base station device 100-1 and the mobile station 200-2, and base station apparatus 100-2 between the mobile station device 200-2 channel quality indicator (information on channel _{H 22),} (information on channel _{H 23)} channel quality indicator between the mobile station apparatus 200-2 and base station apparatus 100-3, obtained through the backhaul 10-1 and, (information on channel _{H 31)} channel quality indicator between the mobile station apparatus 200-3 and base station apparatus 100-1, the channel quality indicator between the mobile station apparatus 200-3 and base station apparatus 100-2 ( Information on the propagation path H ₃₂ ) and a propagation path quality indicator (information on the propagation path H ₃₃ ) between the base station apparatus 100-3 and the mobile station apparatus 200-3 are acquired through the backhaul line 10-2.

  That is, the master base station apparatus estimates the propagation path fluctuation between the base station apparatus (master base station apparatus and slave base station apparatus) with which each mobile station apparatus 200-k performs cooperative control. Get a sign.

  Further, as the propagation path state information, the upper layer 101 acquires direct or indirect information of received field strength information and SINR information of the mobile station apparatus connected to the slave base station apparatus.

  Further, the upper layer 101 sends a transmission mode switching request, a modulation multi-level number from the slave base station devices (base station device 100-2 and base station device 100-3) through the backhaul lines 10-1 and 10-2. In addition, it is possible to acquire information relating to parameters of transmission signals transmitted by each base station apparatus, such as band information. The transmission signal parameters are those transmitted by the mobile station apparatus connected to the slave base station apparatus.

  Further, the upper layer 101 acquires the desired transmission power of the base station device from the slave base station devices (base station device 100-2 and base station device 100-3) through the backhaul lines 10-1 and 10-2. be able to.

  Further, the upper layer 101 inputs the propagation path information to the weight coefficient control unit 105. Here, the upper layer 101 may be configured to input the number of base station apparatuses and the number of mobile station apparatuses to cooperate to the weight coefficient control unit 105. Further, the upper layer 101 can also notify the weighting coefficient control unit 105 of a transmission mode based on a parameter related to a transmission signal transmitted by the base station apparatus, such as a request for switching the transmission mode, a switching flag thereof, and the like.

The upper layer 101 notifies the slave base station apparatus of the transmission weight coefficient or / and the reception weight coefficient calculated by the weight coefficient control unit 105 described later via the backhaul lines 10-1 and 10-2. The upper layer 101 of the base station apparatus 100-1, the transmission weight factor _{V 2} base station device 100-2 multiplies the transmission signal and / _or, the reception weights mobile station device 200-2 multiplies the reception signal and coefficient _{U 2,} and notifies the base station device 100-2 via the backhaul 10-1. The upper layer 101 of the base station 100-1, a transmission weight factor _{V 3} to the base station device 100-3 multiplies the transmission signal, the reception weighting factors _{U 3} to the mobile station device 200-3 multiplies the reception signal To the base station apparatus 100-3 via the backhaul line 10-2.

  The upper layer 101 controls transmission power based on the control signal output from the control signal detection unit 123 and / or the propagation path state information acquired through the backhaul line. Here, a part of the upper layer 101 that controls transmission power is referred to as a power control unit.

  FIG. 4 is a flowchart illustrating one aspect of transmission power control.

  The power control unit acquires the CSI of the mobile station device connected to the master base device or / and the slave base station device from each base station device (S010). Next, it is determined whether or not the CSI is larger than a predetermined threshold (S011). For example, when the CSI is the received SINR of the mobile station apparatus, it is determined whether the received SINR is greater than a predetermined received SINR. Next, when it is determined that the CSI is smaller than the predetermined threshold (No in S011), the flow is terminated in order to maintain the current transmission power. On the other hand, when it is determined that the CSI is larger than the predetermined threshold (Yes in S011), the power control unit notifies the weight coefficient control unit 105 and the power setting unit 108 that the transmission power is increased (S012). For example, as notification that the transmission power is increased, notification that the maximum transmission power is increased is performed. Further, the power control unit of the upper layer 101 notifies the slave base station apparatus of the notification that the transmission power is increased through the backhaul line.

  Further, the power control unit notifies the weight coefficient control unit 105, the power setting unit 108, and the slave base station device of the base station device that increases the transmission power in addition to the notification that the transmission power is increased. For example, as the notification of the base station apparatus that increases the transmission power, the ID of the base station apparatus is notified.

  Further, the power control unit can notify the weight coefficient control unit 105, the power setting unit 108, and the slave base station device of the transmission power of each base station device. The transmission power notification includes a transmission power value itself, a difference between the transmission power of the information data and the transmission power of the reference signal, and a ratio between the transmission power of the information data and the transmission power of the reference signal. As the notification of the transmission power, RNTP in LTE can be used.

  Further, the upper layer 101 can notify the weighting coefficient control unit 105, the power setting unit 108, and the slave base station apparatus of the transmission mode determined based on the transmission power determined by the power control unit.

  Also, the upper layer 101 determines whether to suppress interference in cooperation with each other for each base station apparatus. Here, a part of the upper layer 101 that determines whether to suppress interference in cooperation with each other is referred to as a transmission mode determination unit. A mode in which interference is suppressed in cooperation with each other is referred to as a cooperative mode.

  The transmission mode determination unit can also determine a mode determined from parameters such as the number of spatial multiplexing (rank number) of signals that can be received by the mobile terminal and the number of antennas.

  As a specific aspect, the transmission mode determination unit determines that the master base station apparatus determines that there is a case where the CSI is larger than the predetermined threshold in the determination of whether the CSI is larger than the predetermined threshold in S011 of FIG. It is determined that the cooperative mode is applied to the base station apparatus and mobile station apparatus that are the targets of the acquired CSI. That is, in addition to the base station apparatus that has determined that the CSI is greater than the predetermined threshold, it is determined that the cooperative mode is also applied to the base station apparatus that does not exceed the predetermined threshold.

  Thereby, the interference can be comprehensively suppressed for the base station apparatus that will be affected by the inter-cell interference. Therefore, the system throughput can be improved.

  As another aspect, the transmission mode determination unit determines whether the CSI is greater than the predetermined threshold in the determination of whether the CSI in S011 of FIG. 4 is greater than the predetermined threshold. It is determined that the cooperative mode is applied to the base station apparatus and mobile station apparatus that are determined to be larger than the threshold.

  Thereby, the range of the base station apparatus and mobile station apparatus which a cooperation mode applies can be restrict | limited by CSI. Therefore, it is possible to improve the system throughput while avoiding the complexity of calculating the transmission weight coefficient and the reception weight coefficient.

  As another aspect, the transmission mode determination unit determines that the cooperative mode is applied to the base station apparatus that notifies that the transmission power is to be increased and the mobile station apparatus that is connected thereto.

  Thereby, the range of the base station apparatus and mobile station apparatus which a cooperation mode applies can be restrict | limited by transmission power. Therefore, it is possible to improve the system throughput while avoiding the complexity of calculating the transmission weight coefficient and the reception weight coefficient.

  Furthermore, as another aspect, the transmission mode determination unit cooperates with the base station apparatus and the mobile station apparatus connected thereto when the transmission power set by notification that the transmission power is increased is larger than a predetermined threshold. It is determined that the mode is applied.

  Thereby, the range of the base station apparatus and mobile station apparatus which a cooperation mode applies can be restrict | limited by transmission power. Therefore, it is possible to improve the system throughput while avoiding the complexity of calculating the transmission weight coefficient and the reception weight coefficient.

  As another aspect, the transmission mode determination unit determines that the cooperative mode is applied when there are a predetermined number or more of base station apparatuses in which the transmission power output from the power control unit is greater than a predetermined threshold. .

  Thereby, the range of the base station apparatus and mobile station apparatus to which the cooperative mode is applied can be limited by the base station apparatus to which the transmission power and the cooperative mode are applied. Therefore, it is possible to improve the system throughput while avoiding the complexity of calculating the transmission weight coefficient and the reception weight coefficient.

  Further, the above-described cooperative mode may be set to a subdivided mode. For example, a mode in which interference is suppressed in cooperation with each other by multiplying a transmission weight coefficient (first cooperative mode) and a mode in which interference is suppressed in cooperation with each other by multiplying a transmission weight coefficient and a reception weight coefficient (second Cooperative mode) can be set.

  For example, the transmission mode determination unit sets the first cooperative mode when the number of base station apparatuses determined to have a CSI greater than a predetermined threshold is equal to or less than the number of transmission antennas of the base station apparatus. On the other hand, the second cooperative mode is set when the number of base station apparatuses determined to have a CSI larger than a predetermined threshold is greater than the number of transmission antennas of the base station apparatus.

  The upper layer 101 also acquires feedback information such as MCS information and the number of spatial multiplexing included in the control signal output by the control signal detection unit 123. Upper layer 101 outputs information data to encoding section 102 and outputs control data to control signal generation section 107 based on the feedback information.

  The upper layer 101 also notifies other parameters necessary for each part of the base station apparatus 100-1 to exhibit its function.

  The encoding unit 102 performs error correction encoding on the information data input from the upper layer 101. The information data is, for example, an audio signal accompanying a call, a still image or moving image signal representing a captured image, a character message, or the like. The encoding method used when the encoding unit 102 performs error correction encoding is, for example, turbo encoding, convolutional encoding, low density parity check encoding; LDPC).

  The encoding unit 102 performs rate matching processing on the encoded bit sequence in order to match the coding rate of the error correction encoded data sequence with the encoding rate corresponding to the data transmission rate. May be. Further, the encoding unit 102 may have a function of rearranging and interleaving the error correction encoded data series.

  Modulation section 103 modulates the signal input from encoding section 102 to generate a modulation symbol. The modulation processing performed by the modulation unit 103 includes, for example, BPSK (binary phase shift keying), QPSK (quadture phase shift keying), and M-QAM (M-quad quadrature amplitude value). Amplitude modulation, eg M = 16, 64, 256, 1024, 4096). Modulation section 103 may have a function of rearranging generated modulation symbols and interleaving them.

The weighting coefficient control unit 105 uses the propagation path information (propagation path estimated value) acquired from the upper layer 101 to multiply the signal transmitted by the master base station apparatus and the slave base station apparatus and the transmission weight coefficient V _j and each base. A reception weight coefficient U _k by which the mobile station apparatus connected to the station apparatus multiplies the reception signal is calculated. That is, the weight coefficient control unit 105 calculates a transmission weight coefficient and a reception weight coefficient using the propagation path information of the entire system.

  As an aspect, the weighting factor control section 105 sets the direction (vector) of the equivalent propagation path of interference signals arriving from a plurality of base station devices serving as interference sources to the reception weighting factor by which the received signal is multiplied in each mobile station device. The transmission weight coefficient is calculated so as to be orthogonal (formula (1)).

Here, H _kj is a propagation path matrix between the base station apparatus 100-j and the mobile station apparatus 200-k that is the target of cooperative control, and V _j is a vector of transmission weight coefficients of the base station apparatus 100-j. , U _k is a vector of reception weight coefficients of the mobile station apparatus 200-k, and d _k is the number of streams. ^H is a complex conjugate transpose.

  The weight coefficient control unit 105 can calculate the transmission weight coefficient and the reception weight coefficient in consideration of the notification of increasing the transmission power acquired from the upper layer 101.

  As an aspect, the weighting coefficient control unit 105 calculates a transmission weighting coefficient and a receiving weighting coefficient as in Expression (1-1).

ここで、Ｐは、送信電力により定められる係数である。また、Ｐは、前記協調モードを適否の判断に基づいて設定できる。

Here, P is a coefficient determined by transmission power. Moreover, P can set the said cooperation mode based on the judgment of suitability.

  The weighting factor control unit 105 can set whether to calculate the transmission weighting factor and the reception weighting factor based on the notification that the transmission power acquired from the upper layer 101 is increased.

  As one aspect, the weighting factor control unit 105 calculates a weighting factor by which the transmission signal or the reception signal is multiplied when receiving a notification to increase the transmission power, and does not calculate the weighting otherwise.

  Further, the weight coefficient control unit 105 can calculate a transmission weight coefficient and a reception weight coefficient in consideration of a transmission power value (described later) output from the power setting unit 108.

  In addition, the weight coefficient control unit 105 can calculate a transmission weight coefficient and a reception weight coefficient in consideration of a transmission power value for each mode described later.

  In addition, the transmission weight coefficient and the reception weight coefficient can be calculated in consideration of the desired transmission power of another base station apparatus output by the higher layer 101.

  The transmission power value, the transmission power value for each mode, and the desired transmission power are set in P of Expression (1-1).

Further, the weight coefficient control unit 105 notifies the upper layer 101 of the transmission weight coefficient V _j of the slave base station apparatus and the reception weight coefficient U _k of the mobile station apparatus connected to the slave base station apparatus.
Further, the weight coefficient control unit 105 outputs a transmission weight coefficient V ₁ to be multiplied to the transmission signal of the master base station apparatus (own station) to the precoding unit 104. Also, the weight coefficient control unit 105 outputs the reception weight coefficient U ₁ of the mobile station apparatus connected to the master base station apparatus (own station) to the control signal generation unit 107.

  In the above description, the case where the weight coefficient control unit 105 calculates the transmission weight coefficient and the reception weight coefficient has been described. However, only the transmission weight coefficient can be calculated.

Precoding section 104 multiplies the modulation symbol output from modulation section 103 by transmission weight coefficient V ₁ .

  The reference signal generation unit 106 generates a reference signal (pilot signal) and outputs the generated reference signal to the resource mapping unit 109. For example, the reference signal is a signal used to estimate the propagation characteristics from the transmitting antenna unit 114 of the base station device to the receiving antenna units 201-1 and 201-2 of each mobile station device. The estimated propagation characteristics are used for propagation path information for calculating transmission weight coefficients and reception weight coefficients, or propagation path compensation in the mobile station apparatus. The code sequence constituting the reference signal is preferably an orthogonal sequence, for example, a Hadamard code or a CAZAC (Constant Amplitude Zero Auto-Correlation) sequence.

The control signal generation unit 107 generates a control signal including the control data output from the upper layer 101 and the reception weight coefficient U ₁ (the reception weight coefficient of the mobile station apparatus connected to the own station) output from the weight coefficient control unit 105. . Here, a control signal generation unit that generates a control signal including a weight coefficient may be referred to as a weight coefficient information generation unit, and a control signal including the weight coefficient generated by the control signal generation unit may be referred to as weight coefficient information. The control signal may be subjected to error correction coding and modulation processing.

FIG. 5 is a conceptual diagram illustrating an example of a format of a control signal output from the control signal generation unit 107. The control signal has an area for storing the reception weight coefficient information of the mobile station apparatus connected to the own station. As shown in FIG. 5, the reception weighting factors U ₁ to the mobile station device 200-1 multiplies the reception signal and reception weight coefficient information, area for storing the information is provided. The transmission power information is vibration used for the base station apparatus to notify the mobile station apparatus of transmission power. The control signal may also include information on the transmission power difference between the reference signal and the data signal (for example, LTE-A PDSCH).
In addition, a cell information area such as a cell ID can be provided in the control signal.
The control signal generation unit 107 generates a synchronization signal for establishing and following synchronization such as symbol synchronization and frame synchronization, and a broadcast channel (for example, PBCH: Physical Broadcast Channel in LTE and LTE-A). As the synchronization signal, LTE, LTE-A PSS (Primary Synchronization Signal), or SSS (Secondary Synchronization Signal) can be used.

  Returning to FIG. 3, the power setting unit 108 determines the transmission power value of the transmission signal of the master base station apparatus 100-1. The power setting unit 108 sets the transmission power based on the presence / absence of notification to increase the transmission power input from the upper layer 101. Moreover, the power setting unit 108 can set transmission power based on the transmission mode. Further, the power setting unit 108 can set the transmission power based on the difference between the transmission power of the information data and the transmission power of the reference signal, and the ratio of the transmission power of the information data and the transmission power of the reference signal.

  Further, the power setting unit 108 can control the transmission power value based on the maximum transmission power value determined by the class (classification) of the base station apparatus input from the higher layer 101.

  For example, the maximum transmission power is set according to the classification of each base station device such as a macro base station device or a pico base station device.

  The power setting unit 108 holds a predetermined transmission power value determined based on the presence or absence of a notification to increase the transmission power and a predetermined transmission power value (transmission power value for each mode) determined for each transmission mode. You can also.

  Further, the power setting unit 108 can control the transmission power value of the transmission signal based on the occupied band of the transmission signal input from the upper layer 101. For example, the occupied band corresponds to the system band of the base station apparatus, the number of resource blocks in LTE-A, and the like.

  The power setting unit 108 controls the transmission power value of the transmission signal based on the desired reception power level (target reception power level) of the mobile station apparatus connected to the base station apparatus input from the higher layer 101. be able to.

  For example, the target received power level is determined based on the type of signal that each base station apparatus transmits to the mobile station apparatus. For example, the types of signals that each base station device transmits to mobile station devices include Semi-persistent data when performing voice communication such as VoIP, dynamic scheduling data for performing data communication, random access data such as synchronization signals, etc. A predetermined target received power level is set in each section.

  Further, the power setting unit 108 can control the transmission power value based on information related to transmission signals such as MCS information and the number of spatial multiplexing input from the upper layer 101. The power setting unit 108 can also hold MCS information and a predetermined transmission power value determined for each spatial multiplexing number.

  Further, the power setting unit 108 can control transmission power based on the path loss between each base station apparatus and mobile station apparatus input from the higher layer 101. The path loss can also be calculated from the propagation path information.

  Further, the power setting unit 108 outputs the transmission power value to the power adjustment unit 110. Further, the power setting unit 108 outputs the transmission power value to the transmission unit 113. Further, the power setting unit 108 can output the transmission power value to the weighting coefficient control unit 105. Further, the power setting unit 108 can output the transmission power value to the control signal generation unit 107.

  The resource mapping unit 109 maps modulation symbols, reference signals, and control signals to resource elements based on scheduling information notified from the upper layer 101 (hereinafter referred to as resource mapping). This is the minimum unit for arranging a signal consisting of a carrier and one OFDM symbol.

  The power adjustment unit 110 sets the power of the signal input from the resource mapping unit 109 based on the transmission power value.

  The IDFT unit 111 performs inverse discrete Fourier transform (IDFT) on the frequency domain signal input from the power adjustment unit 110 to convert it into a time domain signal. The IDFT unit 111 may use another processing method (for example, inverse fast Fourier transform [IFFT, inverse fast Fourier transform]) instead of the IDFT as long as the frequency domain signal can be converted into a time domain signal.

  The GI insertion unit 112 adds an GI (Guard Interval; also referred to as a guard interval or guard interval) to the time domain signal (referred to as an effective symbol) input from the IDFT unit 111 to generate an OFDM symbol. The GI is a section added for the purpose of preventing the OFDM symbols of the preceding and succeeding times from interfering with each other. For example, the GI insertion unit 112 places a copy (copy) of a part of the latter half of the effective symbol as a GI and prepends the effective symbol. Therefore, an effective symbol preceded by GI is an OFDM symbol.

  The transmission unit 113 performs D / A (digital-to-analog) conversion on the OFDM symbol input from the GI insertion unit 112 to generate an analog signal. The transmission unit 113 includes an amplification unit that adjusts transmission power. The amplification unit can adjust the power of the OFDM symbol input from the GI insertion unit 112 based on the transmission power setting value.

  In addition, the transmission unit 113 generates a band limited signal by performing band limitation on the generated analog signal by filtering processing. The transmission unit 113 up-converts the generated band-limited signal into a radio frequency band and outputs it to the transmission antenna unit 114.

Next, a process of calculating the transmission weight coefficient V _j and the reception weight coefficient U _k in the communication system 1 will be described. FIG. 6 is a flowchart illustrating an example of processing in which the weight control unit 105 calculates the transmission weight coefficient V _j and the reception weight coefficient U _k .

  In the calculation method of FIG. 5, the complex conjugate transpose of the propagation path matrix from the base station apparatus to the mobile station apparatus becomes the propagation path matrix from the mobile station apparatus to the base station apparatus (propagation reciprocity). Thus, the process of obtaining the weighting coefficient that minimizes the influence of interference is repeated while switching the roles of transmission and reception.

First, when the weighting factor control unit 105 acquires the propagation path information, the weighting factor control unit 105 sets an arbitrary transmission weighting factor V _j (S100).

Next, the weighting factor control unit 105 calculates the total interference Q _{k, i} received by the mobile station apparatus 200-k based on the equation (2) (S101). Here, Q is a covariance matrix of the received interference signal. Further, P is transmission power, and K is the number of mobile station apparatuses that are targets of cooperative control. ^H represents complex conjugate transposition.

Next, the weighting coefficient control section 105, the sum _{Q k} of the calculated _{interference, i} and singular value decomposition, the sum _{Q k} of the _{interference,} the receiving weight coefficients _{U k} for suppressing _i, it calculates a _i (S102). In step S102 and step S103, the reception weight coefficient U _k is calculated when the mobile station device 200-k receives the transmission signal of the base station device 100-j.

Next, the roles of transmission and reception of the base station device 100-j and the mobile station device 200-k are switched (S103). That is, the mobile station apparatus 200-k are coefficients _{U k,} the case where the transmission signal a base station apparatus 100-j obtained by multiplying the _i receives, calculates a reception weighting factors _U ^{k ~} of the base station apparatus 100-j . The reception weight coefficient U _k ^˜ corresponds to the transmission weight coefficient V _k of the base station apparatus 100-j.

Regarding the calculation of the reception weight coefficient U _k ^˜ , first, the total interference Q _{j, i} ^˜ received by the base station apparatus 100-j is calculated based on the equation (3) (S104). Here, H _jk ^˜ = H _kj ^H , V _k ^˜ = U _k , P ^˜ is transmission power.

Then, the total sum _{Q j} of the _{interference,} and singular value decomposition of the ^{i ~,} the sum of the interference _{Q j,} receives the weight coefficient _{U k} for suppressing ^{i _~,} calculates the ^{i ~} (S105). Again, the roles of transmission and reception of the base station device 100-j and the mobile station device 200-k are switched (S106). In other _words, substituting _{V k, i = U k,} i ~ a.

  The counter for counting the number of processes is incremented by 1 (S107), and the processes in steps S101 to S106 are repeated until the predetermined number I is reached (N in S108). If the predetermined number of times I has been reached (S108, Y), the process is terminated.

As described above, the reception weight coefficients (U _k , U _k ^˜ ) that repeatedly reduce the interference power are updated repeatedly while switching the roles of transmission and reception of the base station device 100-j and the mobile station device 200-k. As a result, a reception weighting coefficient that allows the base station apparatus 100-j and the mobile station apparatus 200-k to suppress the influence of interference is obtained.

k = j and reception weighting factors _U ^{k ~} a made a transmission weight factor _{V j} of the base station apparatus 100-j, a reception weighting coefficient _{U k} by the receiving weighting factors _{U k} of the mobile station apparatus 200-k, a plurality The base station apparatuses 100-j can suppress the influence of interference in cooperation. This calculation method is an example, and the present invention is not limited to this. Other calculation methods may be used.

  Next, the slave base station devices (base station device 100-2 and base station device 100-3) in the first embodiment will be described. FIG. 7 is a schematic diagram illustrating the configuration of slave base station devices (base station device 100-2 and base station device 100-3) according to the first embodiment. Hereinafter, although it demonstrates as a structure of base station apparatus 100-2, base station apparatus 100-3 also has the same structure.

  The base station apparatus 100-2 includes an upper layer 151, an encoding unit 102, a modulation unit 103, a precoding unit 154, a reference signal generation unit 106, a control signal generation unit 157, a power setting unit 158, a resource mapping unit 109, and power adjustment. Unit 110, IDFT unit 111, GI insertion unit 112, transmission unit 113, transmission antenna unit 114, reception antenna unit 121, reception unit 122, and control signal detection unit 123. In addition, when part or all of the base station apparatus 100-2 is formed into a chip to form an integrated circuit, a chip control circuit (not shown) that controls each functional block is provided.

  Compared with base station apparatus 100-1, operations in higher layer 151, precoding section 154, control signal generation section 157, and power setting section 158 in base station apparatus 100-2 are different. Hereinafter, mainly different parts will be described.

  The upper layer 151 acquires propagation path information included in the control signal input from the control signal detection unit 123.

Specifically, the higher layer 151 includes propagation path state information (propagation path information H ₂₁ between the base station apparatus 100-1 and the mobile station apparatus 200-2, The propagation path information H ₂₂ between the base station apparatus 100-2 and the mobile station apparatus 200-2 and the propagation path information H ₂₃ between the base station apparatus 100-3 and the mobile station apparatus 200-2) are acquired.

    The propagation path state information can also include direct or indirect information of received field strength information and SINR information of the mobile station apparatus.

  Also, the upper layer 151 notifies the propagation path information to the master base station apparatus 100-1 that calculates the weighting factor via the backhaul line 10-1.

  Further, the upper layer 151 sends, to the master base station apparatus 100-1, the parameters related to the transmission signal transmitted by each base station apparatus, such as a transmission mode switching request and the modulation multi-level number, via the backhaul line 10-1. You can be notified.

  Further, the upper layer 151 relates to parameters of transmission signals transmitted by each base station device such as the number of modulation multi-values and occupied bands via the backhaul line 10-1, requests for switching transmission modes, The master base station apparatus 100-1 can be notified of the desired transmission power, the path loss between the base station apparatus and the mobile station apparatus connected to the base station apparatus, and the like.

Further, the upper layer 151 transmits the transmission weight coefficient V ₂ by which the transmission signal of the own station is multiplied through the backhaul line 10-1 and the reception weight coefficient U ₂ of the mobile station apparatus 200-2 connected to the own station. Is acquired from the master base station apparatus.

  Further, the upper layer 151 can acquire a notification that the transmission power is increased for a signal transmitted by the base station apparatus via the backhaul line 10-1. Further, the upper layer 151 can acquire the transmission power value of the signal transmitted by the base station apparatus via the backhaul line 10-1.

The upper layer 151 inputs the transmission weight coefficient V ₂ to the precoding unit 154. Further, the upper layer 151 inputs the reception weight coefficient U ₂ to the control signal generation unit 157.

  Further, the upper layer 151 transmits the MCS information of the transmission signal, the number of spatial multiplexing, the transmission power, the transmission power difference between the reference signal and the data signal (for example, LTE-A PDSCH), etc. to the mobile station apparatus. Can be entered.

Precoding section 154 multiplies the transmission weight factor V ₂ to a modulation symbol modulation unit 103 is output.

The control signal generation unit 157 generates a control signal including the control data output from the higher layer 151 and the reception weight coefficient U ₂ (the reception weight coefficient of the mobile station device 200-2 connected to the own station). Similarly, the format shown in FIG. 5 is applied as the format of the control signal. That is, it has an area for storing the reception weight coefficient information U ₂ and transmission power information of the mobile station apparatus 200-2 connected to the own station. The control signal may also include information on the transmission power difference between the reference signal and the data signal (for example, LTE-A PDSCH).

  The power setting unit 158 controls the power of the transmission signal based on the transmission power value of the signal transmitted from the higher layer 151 and transmitted by the base station apparatus.

  The power setting unit 158 can control the power of the transmission signal based on the transmission mode input from the higher layer 151, the switching flag thereof, and the like. Also, the power setting unit 158 can set the transmission power based on the difference between the transmission power of the information data and the transmission power of the reference signal and the ratio of the transmission power of the information data and the transmission power of the reference signal.

  Further, the power setting unit 158 outputs the set transmission power value to the power adjustment unit 110 and the transmission unit 113.

  Next, the mobile station device 200-k in the first embodiment will be described. FIG. 8 is a schematic diagram illustrating a configuration of the mobile station apparatus 200-k according to the first embodiment.

  The mobile station apparatus 200-k includes a plurality of reception antenna units 201-e, a plurality of reception units 202-e, a propagation path estimation unit 203, a plurality of GI removal units 204-e, a plurality of DFT units 205-e, and interference suppression. Unit 206, propagation path compensation unit 207, demodulation unit 208, decoding unit 209, control signal detection unit 210 and higher layer 211, control signal generation unit 221, transmission unit 222, and transmission antenna unit 223. In addition, in FIG. 8, although the example in case the mobile station apparatus 200-k has two (e = 2) receiving antennas is shown, it is not restricted to this and you may provide how many antennas. Moreover, although it is one transmission antenna, not only this but a several transmission antenna may be provided, and it is good also as a structure which shares a transmission antenna and a reception antenna. In addition, when a part or all of the mobile station device 200-k is formed into a chip to form an integrated circuit, a chip control circuit (not shown) that controls each functional block is provided.

  The mobile station device 200-k receives the transmission signal of the base station device 100-j via the reception antenna unit 201-e. Here, when the mobile station device 200-m (a set of mεk) is connected to the base station device 100-m, transmission signals other than the base station device 100-m cause inter-cell interference.

  The receiving unit 202-e down-converts the radio frequency signal input from the receiving antenna unit 201-e into a frequency band in which digital signal processing is possible, and further performs filtering processing on the down-converted signal to remove unnecessary components (spurious; (Spurious) is suppressed. The receiving unit 202-e converts the filtered signal from an analog signal to a digital signal (A / D; Analog-to-Digital), and the converted digital signal is a propagation path estimation unit 203 and a GI removal unit. 204-e and the control signal detection unit 210.

  The GI removal unit 204-e removes the guard interval GI from the signal output from the reception unit 202-e in order to avoid distortion due to the delayed wave, and outputs the removed signal to the DFT unit 205-e.

  The DFT unit 205-e performs Discrete Fourier Transform (DFT) that converts the signal from which the guard interval GI input from the GI removal unit 204-e is removed from a time domain signal to a frequency domain signal, and performs interference. Output to the suppression unit 206. Note that the DFT unit 205-e is not limited to the DFT as long as it can convert the signal from the time domain to the frequency domain, and may perform other methods, for example, Fast Fourier Transform (FFT).

  The propagation path estimation unit 203 performs propagation path estimation using the reference signal included in the signal output from the reception unit 202-e. The propagation path estimated value is, for example, a transfer function or an impulse response.

  Then, the propagation path estimation unit 203 notifies the propagation path estimation value to the propagation path compensation unit 207, the control signal generation unit 221, and the upper layer 211.

  Moreover, the propagation path estimation part 203 estimates reception power and SINR using the reference signal contained in the signal which the receiving part 202-e output. Then, the propagation path estimation unit 203 notifies the control signal generation unit 221 and the upper layer 211 of the received power and the like.

  The control signal detection unit 210 detects a control signal included in the signal output from the reception unit 202-e. Then, when the control signal detection unit 210 extracts the reception weight coefficient information (see FIG. 5) included in the control signal, the control signal detection unit 210 inputs the information to the interference suppression unit 206. In addition, when the control signal detection unit 210 extracts MCS, information on the number of layers, and transmission power information applied to information data included in the control signal, the control signal detection unit 210 notifies the demodulation unit 208 and the decoding unit 209 of the extracted MCS.

  The interference suppression unit 206 multiplies the frequency domain signal input from the DFT unit 205-e by the reception weight coefficient U input from the control signal detection unit 210.

  The propagation path compensation unit 207, based on the propagation path estimation value input from the propagation path estimation unit 203, performs ZF (Zero Forcing) equalization, MMSE (Minimum Mean Square Error) equalization, etc. Using a method, a weighting factor for correcting propagation path distortion due to fading is calculated. The propagation path compensation unit 207 performs propagation path compensation by multiplying the signal input from the interference suppression unit 206 by this weight coefficient.

  Demodulation section 208 performs demodulation processing on the signal (data modulation symbol) after propagation path compensation input from propagation path compensation section 207. The demodulation process may be either a hard decision (calculation of a coded bit sequence) or a soft decision (calculation of a coded bit LLR).

  The decoding unit 209 performs error correction decoding processing on the encoded bit sequence (or encoded bit LLR) after demodulation output from the demodulation unit 208, calculates information data transmitted to itself, 211 is output. This error correction decoding processing method is a method corresponding to error correction coding such as turbo coding and convolution coding performed by the connected base station apparatus 100-m. Either a hard decision or a soft decision can be applied to the error correction decoding process.

  When the base station apparatus 100-j transmits interleaved data modulation symbols, the decoding unit 209 performs deinterleaving corresponding to the interleaved input encoded bit sequence before performing error correction decoding processing. Process. Then, the decoding unit 209 performs error correction decoding processing on the signal that has been subjected to deinterleaving processing.

The control signal generation unit 221 generates a control signal including propagation path information between the own station and the base station device 100-j. For example, in the communication system 1 in FIG. 1, the control signal of the mobile station device 200-1 includes the propagation path H ₁₁ between the mobile station device 200-1 and the base station device 100-1 that cooperates with the mobile station device 200-1. Includes propagation path information of propagation path H ₁₂ between base station apparatus 100-2 cooperating with 200-1 and propagation path H ₁₃ between base station apparatus 100-3 cooperating with mobile station apparatus 200-1. It is.

  In addition, the control signal generation unit 221 generates a control signal for transmitting information for requesting switching / setting of the transmission mode to the base station apparatus.

  Further, the control signal generation unit 221 generates a control signal for transmitting feedback information (including CQI, RI, and PMI) to the base station apparatus. The feedback information is determined by the upper layer 211 based on the channel estimation value calculated by the channel estimation unit 203.

  The control signal generation unit 221 generates a control signal by performing error correction coding and modulation mapping on the control signal. The signal including the control signal output from the control signal generation unit 221 is up-converted by the transmission unit 222 before the frequency band that can be transmitted in the downlink, and is connected via the transmission antenna unit 223 to the base station apparatus 100- sent to j.

  Next, the process in the interference suppression unit 206 of the mobile station device 200-k will be specifically described. The following is an example when the mobile station has two antennas (e = 2).

In mobile station apparatus 200-k, a signal input from DFT section 205-1 and DFT section 205-2 to interference suppression section 206 can be expressed as follows using equation (4), with vector R _k being used. it can.

Here, R _{k and e} are signals input from the DFT unit 205- _e of the mobile station apparatus k, H _{kj and e} are transmission signals of the base station apparatus 100-j (j = 1 to 3), and the mobile station apparatus 200. channel when -k is received through the reception antenna unit 201-e (transfer function), up to V _j is the transmission weight factor that is multiplied to the transmission signal of the base station apparatus 100-j (each base station apparatus S _j is a data modulation symbol of base station apparatus 100-j.

When the interference suppression unit 206 multiplies the above R _k by the reception weight coefficient U _k as Y _k , it can be expressed as Equation (5). Here, U _{k and e} are reception weighting factors by which a signal input from the DFT unit 205- _e of the mobile station apparatus 200-k is multiplied.

  Next, a procedure between the base station apparatus and the mobile station apparatus in the communication system 1 will be described.

In FIG. 9, the master base station apparatus (base station apparatus 100-1) of the communication system 1 calculates the transmission weight coefficient V _j and the reception weight coefficient U _k , and the slave base station apparatuses (base station apparatuses 100-2 and 100-). It is a sequence diagram which shows the operation example notified to 3) and the mobile station apparatus 200-k.

  The master base station apparatus makes a channel quality measurement request to the slave base station apparatus (S201). The propagation path quality measurement request may be periodic or non-periodic.

  Each slave base station apparatus requests the channel quality measurement from the mobile station apparatus connected to the own station (S202). The propagation path quality measurement request may be periodic or non-periodic.

  On the other hand, the mobile station apparatus 200-1 connected to the master base station apparatus receives the channel quality measurement request directly from the master base station apparatus.

  Next, the mobile station apparatus 200-k that has received the channel quality measurement request measures the channel quality (S203), and notifies the slave base station apparatus or master base station apparatus of the propagation quality information (S204). The propagation quality information is propagation path state information.

  Then, the slave base station apparatus that has received the notification of the propagation path quality information notifies the master base station apparatus of the notification of the propagation path quality information (S205).

  Next, the master base station apparatus determines whether or not the propagation path quality information satisfies a predetermined threshold value, and determines the base station apparatus to cooperate and determine the transmission power of each base station apparatus (S206). .

  Then, the master base station apparatus requests a propagation path state notification to the slave base station apparatus determined as the cooperating base station apparatus (S207).

  As one aspect, in the determination of whether or not the propagation path quality information satisfies a predetermined threshold, if there is the propagation path quality information that satisfies a requirement, a transmission source of the propagation path quality information received by the master base station apparatus A request for a propagation path state notification is made to a slave base station apparatus (S207).

  As another aspect, when the propagation path quality information satisfying the requirement exists in determining whether or not the propagation path quality indicator satisfies a predetermined threshold, the slave that is a transmission source of the propagation path quality information satisfying the requirement A request for a propagation path state notification is made to the base station apparatus (S207).

Next, the slave base station apparatus that has received the request for the propagation path state notification requests the mobile station apparatus for a propagation path state notification (S208). And the mobile station apparatus which received the request | requirement of the propagation path state notification performs propagation path estimation (S209). In the communication system 1, the mobile station device 200-k estimates the propagation path H _k1 , the propagation paths H _k2 and H _k3 . Propagation path estimation is performed using the reference signal which each base station apparatus 200-j transmits, for example.

  Next, the mobile station apparatus notifies the result of propagation path estimation (propagation path state information) to the slave base station apparatus that is the request source of the propagation path state notification (S210). And the slave base station apparatus which received propagation path state information notification (S210) notifies propagation path state information to a master base station apparatus (S211).

  In addition, the mobile station apparatus connected to the master base station apparatus directly performs the propagation path state information request and the propagation path state information notification with the master base station apparatus.

Next, the master base station apparatus calculates a transmission weight coefficient V _j and a reception weight coefficient U _k based on the propagation path state information obtained in step S211 (S212).

Then, the master base station apparatus notifies the calculated transmission weight coefficient V _j to the slave base station apparatus 100-j using the backhaul line (S213).

Further, the master base station apparatus notifies the reception weight coefficient U _k of each mobile station apparatus via the base station apparatus to which each mobile station apparatus is connected (S213, S214). For example, the mobile station device 200-2 that are connected to the slave base station device 100-2 via the slave base station device 100-2, to obtain the receive weighting factors _{U 2} from the master base station device 100-1 become.
At this time, the transmission power information of the own station or slave base station apparatus can also be notified (S213, S214).

The master base station apparatus, the reception weighting factors U ₁ of the mobile station device 200-1 that are connected to the local station to directly notify the mobile station apparatus (S215).

Then, the master base station device and the slave base station device multiply the information data transmitted to the mobile station devices connected to each by the transmission weight coefficient V _j (S216, S217), and transmit (S218, S219).

As described above, in the first embodiment, in a communication system in which cells of a plurality of base station apparatuses are arranged so that all or some of them overlap, the plurality of base station apparatuses cooperate with each other. A signal multiplied by a weighting coefficient for performing interference suppression is transmitted. Further, the weighting factor may include a weighting factor that a mobile station device connected to the base station device multiplies the received signal.
Then, the master base station apparatus controls the transmission power of the master base station apparatus / slave base station apparatus in consideration of the presence / absence of transmission mode settings in which interference suppression is performed in cooperation with each other. At that time, the transmission power is controlled for each base station. The master base station apparatus increases the transmission power of the master base station apparatus / slave base station apparatus when the own station or / and the slave base station apparatus satisfy a predetermined reception status.
Specifically, when the transmission mode for performing interference suppression in cooperation is set, the base station apparatus performs control to increase the transmission power only for the base station apparatus that performs the transmission mode. Alternatively, when the transmission mode in which the base station apparatus cooperatively performs interference suppression is set, control for increasing the transmission power is performed on all base station apparatuses that have transmitted CSI to the master base station.

  As a result, the mobile station apparatus can receive signals with high received power, and a plurality of base station apparatuses can suppress inter-cell interference in cooperation, thereby improving system throughput.

<Second Embodiment>
In the second embodiment, in the communication system 1 in which a plurality of base station apparatuses 100-j described in the first embodiment cooperate to suppress inter-cell interference, transmission power control and transmission mode control It is.

  FIG. 10 is a flowchart illustrating one aspect of transmission power control in the present embodiment.

  In the upper layer 101, the power control unit acquires the CSI of the mobile station device connected to the master base device or / and the slave base station device from each base station device (S301). N is the number of acquired CSI. Next, it is determined for each acquired CSI whether or not this CSI is larger than a predetermined threshold (S302).

  For example, when the CSI is the received SINR of the mobile station apparatus, it is determined whether the received SINR is greater than a predetermined received SINR. Next, when it is determined that the CSI is larger than the predetermined threshold (Yes in S302), the power control unit receives the master base station device (weight coefficient control unit 105 and power setting unit 108) from which the master base station device has received CSI. ) And the slave base station apparatus are notified that the transmission power is to be increased (S303).

  Next, when it is determined that the CSI is smaller than the predetermined threshold (No in S302), it is determined whether there is a base station apparatus that is determined that another CSI is larger than the predetermined threshold (S302, S304). This process is performed when there is CSI exceeding a predetermined threshold or until the determination for the acquired CSI (N) is completed (S305). Then, when there is no other base station apparatus for which CSI is determined to be greater than the predetermined threshold (No in S305), the flow is terminated in order to maintain the current transmission power.

  As a result, when at least one CQI exceeding a predetermined threshold exists in the master base station apparatus and slave base station apparatus that have received CSI, all of the master base station apparatus and slave base station apparatus that have received the CSI The transmission power can be increased.

  Next, in the higher layer 101, the transmission mode determination unit determines whether each base station apparatus is appropriate for a mode (cooperative mode) in which interference is suppressed in cooperation with each other.

  In the present embodiment, the transmission mode determination unit applies the cooperative mode to all of the master base station apparatus and slave base station apparatus that have received the CSI when notified of increasing the transmission power in S303 of FIG. Judge that. Then, the selected mode is notified to the weight coefficient control unit 105, the power setting unit 108, and the slave base station apparatus.

As described above, in the second embodiment, in the communication system in which the cells of the plurality of base station apparatuses are arranged so that all or some of them overlap, the plurality of base station apparatuses cooperate with each other. A signal multiplied by a weighting coefficient for performing interference suppression is transmitted. Further, the weighting factor may include a weighting factor that a mobile station device connected to the base station device multiplies the received signal.
Then, the master base station apparatus controls the transmission power of the master base station apparatus / slave base station apparatus in consideration of the presence / absence of transmission mode settings in which interference suppression is performed in cooperation with each other. At that time, if there is a master base station apparatus satisfying a predetermined reception condition in either the own station or the plurality of slave base station apparatuses, the master base station apparatus increases the transmission power of the master base station apparatus and the plurality of slave base station apparatuses. .
Specifically, when the transmission mode in which interference suppression is performed cooperatively is set, the base station apparatus is configured to control the transmission power to all base station apparatuses that have transmitted CSI to the master base station. Done.

  As a result, mobile station devices connected to a plurality of base station devices can receive signals with high received power, and can comprehensively suppress the interference with respect to base station devices that will be affected by inter-cell interference. , System throughput can be improved.

  In addition, the base station apparatus and mobile station apparatus in 2nd Embodiment are the structure and function similar to base station apparatus 100-j and mobile station apparatus 200-k in 1st Embodiment except the structure and function mentioned above. Have

  The program that operates in the base station apparatus and the mobile station apparatus according to the present invention is a program that controls the CPU and the like (a program that causes a computer to function) so as to realize the functions of the above-described embodiments related to the present invention. Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

  In the case of distribution in the market, the program can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the mobile station apparatus and base station apparatus in embodiment mentioned above as LSI which is typically an integrated circuit. Each functional block of the receiving apparatus may be individually formed as a chip, or a part or all of them may be integrated into a chip. When each functional block is integrated, an integrated circuit controller for controlling them is added.

  Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

  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 the design and the like within the scope not departing from the gist of the present invention are also claimed. Included in the range.

DESCRIPTION OF SYMBOLS 1 Communication system 100-1 Master base station apparatus 100-2, 100-3 Slave base station apparatus 101 Upper layer 102 Encoding part 103 Modulation part 104 Precoding part 105 Weight coefficient control part 106 Reference signal generation part 107 Control signal generation part 108 power setting unit 109 resource mapping unit 110 power adjustment unit 111 IDFT unit 112 GI insertion unit 113 transmission unit 114 transmission antenna unit 121 reception antenna unit 122 reception unit 123 control signal detection unit 151 upper layer 154 precoding unit 157 control signal generation unit 158 Power setting unit 200 Mobile station device 201 Reception antenna unit 202 Reception unit 203 Channel estimation unit 204 GI removal unit 205 DFT unit 206 Interference suppression unit 207 Channel compensation unit 208 Demodulation unit 209 Decoding unit 210 Control signal detection unit 211 Ear 221 control signal generating unit 222 transmitting unit 223 transmitting antenna unit

Claims (15)

A plurality of base station devices, and a mobile station device connected to at least one of the plurality of base station devices, wherein the plurality of base station devices have a total range or a part of a connectable range of each base station device. A communication system arranged to overlap each other,
The plurality of base station devices include a master base station device and a slave base station device,
The main base station apparatus is
A power control unit that controls transmission power of the plurality of base station devices;
For transmission data transmitted by the plurality of base station apparatuses, a transmission mode for selecting a transmission mode including a cooperative mode in which the plurality of base station apparatuses and a mobile station apparatus connected to the base station apparatus cooperate to suppress interference is selected. A decision unit;
Weight coefficient for calculating a transmission weight coefficient for multiplying transmission data transmitted by the plurality of base station apparatuses so that the plurality of base station apparatuses and mobile station apparatuses connected to the base station apparatus cooperate to suppress interference A control unit;
With
The plurality of base station devices are:
A communication system comprising: a precoding unit that multiplies the transmission data by the transmission weight coefficient. The weight coefficient control unit is a mobile station that has received transmission data transmitted by the plurality of base station apparatuses so that the plurality of base station apparatuses and a mobile station apparatus connected to the base station apparatus cooperate to suppress interference. Calculating a reception weight coefficient by which the device multiplies the received signal;
The plurality of base station apparatuses include a transmission unit that transmits information data obtained by multiplying the transmission data by the transmission weight coefficient to the mobile station apparatus connected to each of the plurality of base station apparatuses,
The communication system according to claim 1, wherein the mobile station apparatus includes an interference suppression unit that multiplies the reception signal by the reception weight coefficient to acquire the information data.   The communication mode according to claim 1 or 2, wherein the transmission mode determination unit selects the cooperative mode comprehensively for the plurality of base station apparatuses. The main base station apparatus acquires propagation path state information from the plurality of base station apparatuses,
The power control unit increases the transmission power of a plurality of base station apparatuses that have acquired the propagation path state information when there is a base station apparatus with propagation path state information that is greater than a predetermined threshold among the propagation path state information. Notice
The communication system according to claim 3, wherein the cooperative mode is selected when notified that the transmission power is to be increased. The main base station apparatus acquires propagation path state information from the plurality of base station apparatuses,
The power control unit notifies that the transmission power of the base station apparatus is increased when there is a base station apparatus having propagation path state information larger than a predetermined threshold among the propagation path state information, and The communication system according to claim 3, wherein the cooperation mode is selected when notified of an increase.   4. The communication system according to claim 3, wherein the transmission mode determination unit selects the cooperative mode when there is a base station apparatus in which the transmission power output from the power control unit is greater than a predetermined threshold. .   The main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and selects the cooperative mode when there is a case where the propagation path state information is larger than a predetermined threshold. The communication system according to claim 3.   The transmission mode determining unit selects, for each of the plurality of base station devices, a cooperative mode in which the plurality of base station devices and a mobile station device connected to the base station device cooperate to suppress interference. The communication system according to claim 1 or 2. The main base station apparatus acquires propagation path state information from the plurality of base station apparatuses,
The power control unit increases the transmission power of a plurality of base station apparatuses that have acquired the propagation path state information when there is a base station apparatus with propagation path state information that is greater than a predetermined threshold among the propagation path state information. The communication system according to claim 8, wherein the cooperative mode is selected when there is a notification that the transmission power is to be increased. The main base station apparatus acquires propagation path state information from the plurality of base station apparatuses,
The power control unit notifies that the transmission power of the base station apparatus is increased when there is a base station apparatus having propagation path state information larger than a predetermined threshold among the propagation path state information, and The communication system according to claim 8, wherein the cooperation mode is selected when there is a notification of the increase.   9. The transmission mode determination unit, when there is a base station device whose transmission power output from the power control unit is larger than a predetermined threshold, selects the cooperative mode for the base station device. The communication system according to 1.   The main base station apparatus acquires propagation path state information from the plurality of base station apparatuses, and selects the cooperative mode of the base station apparatus when there is a case where the propagation path state information is larger than a predetermined threshold. The communication system according to claim 8. A plurality of base station devices, and a mobile station device connected to at least one of the plurality of base station devices, wherein the plurality of base station devices have a total range or a part of a connectable range of each base station device. A communication method in a communication system arranged to overlap each other,
The plurality of base station devices include a master base station device and a slave base station device,
The main base station apparatus, a power control step for controlling transmission power of the plurality of base station apparatuses,
For transmission data transmitted by the plurality of base station apparatuses, a transmission mode for selecting a transmission mode including a cooperative mode in which the plurality of base station apparatuses and a mobile station apparatus connected to the base station apparatus cooperate to suppress interference is selected. A decision step;
Weight coefficient for calculating a transmission weight coefficient for multiplying transmission data transmitted by the plurality of base station apparatuses so that the plurality of base station apparatuses and mobile station apparatuses connected to the base station apparatus cooperate to suppress interference Control steps;
Have
The plurality of base station devices are:
And a precoding step of multiplying the transmission data by the transmission weighting factor. A plurality of base station devices, and a mobile station device connected to at least one of the plurality of base station devices, wherein the plurality of base station devices have a total range or a part of a connectable range of each base station device. A base station apparatus of a communication system arranged to overlap each other,
The plurality of base station devices include a master base station device and a slave base station device,
The main base station apparatus, a power control unit that controls transmission power of the plurality of base station apparatuses,
For transmission data transmitted by the plurality of base station apparatuses, a transmission mode for selecting a transmission mode including a cooperative mode in which the plurality of base station apparatuses and a mobile station apparatus connected to the base station apparatus cooperate to suppress interference is selected. A decision unit;
Weight coefficient for calculating a transmission weight coefficient for multiplying transmission data transmitted by the plurality of base station apparatuses so that the plurality of base station apparatuses and mobile station apparatuses connected to the base station apparatus cooperate to suppress interference A control unit;
A base station apparatus comprising: A plurality of base station devices, and a mobile station device connected to at least one of the plurality of base station devices, wherein the plurality of base station devices have a total range or a part of a connectable range of each base station device. A mobile station apparatus of a communication system arranged to overlap each other,
The mobile station device connected to the base station device is
When the base station apparatus calculates and transmits a reception weight coefficient by which a mobile station apparatus that has received transmission data transmitted by the plurality of base station apparatuses in order to cooperatively suppress interference and multiplies the received signal A mobile station apparatus comprising: an interference suppression unit that multiplies the reception signal by the reception weight coefficient to acquire the information data.

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