JP6481233B2 - Wireless communication apparatus and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a wireless communication system.

  Conventional wireless communication systems such as LTE (Long Term Evolution) Release 8 (Rel-8), which is a wireless communication system standardized by 3GPP (3rd Generation Partnership Project), communicate using a bandwidth of up to 20 MHz. Can be done.

  In LTE-A (Long Term Evolution-Advanced), which is an advanced version of LTE, the bandwidth supported by LTE is a basic unit in order to realize further high-speed transmission while ensuring backward compatibility with LTE. Carrier Aggregation (CA: Carrier Aggregation) technology that uses multiple bundled component carriers (CC) at the same time is adopted, and wide bandwidth transmission of 100 MHz width can be realized using a maximum of 5 CC (20 × 5 MHz width). is there.

  Not only such LTE and LTE-A but also wireless communication systems such as IEEE 802.11n / ac, which is a wireless LAN standard, OFDM (Orthogonal Frequency Division Multiplexing) that is resistant to frequency selective fading. In addition, a multiple input-multiple output (MIMO) transmission technique is employed that realizes high-speed transmission without expanding the frequency band by using a plurality of transmission / reception antennas.

  In addition, a tunable antenna has been proposed in which broadband radio waves such as terrestrial digital broadcasting can be received by a mobile device such as a mobile phone (for example, see Patent Document 1). In the antenna matching circuit provided in the tunable antenna, the variable capacitance element and the inductance element are combined to make the frequency variable in the frequency band (470 MHz to 770 MHz) of the digital television broadcast signal, and match with the subsequent circuit to cause the signal loss. Is suppressed.

  FIG. 18 is a circuit configuration diagram of such an antenna matching circuit described in Patent Document 1. In FIG. An antenna matching circuit 3 is provided between the antenna element 1 and the transmission line 2. The antenna matching circuit 3 includes a first variable capacitance element 4 connected in series with the antenna element 1, a second variable capacitance element 5 connected in parallel with the antenna element 1, and a first variable connected in series with the antenna element 1. It has an inductor 6 and a second inductor 7 connected in parallel with the antenna element 1.

  In the antenna matching circuit configured as described above, the first variable capacitance element 4 makes the Q value of the antenna matching circuit 3 substantially constant regardless of the frequency, and the variable range of the resonance frequency by the second variable capacitance element 5 is increased. Expand. The second variable capacitance element 5 varies the resonance frequency of the antenna matching circuit 3. The first inductor 6 cancels the capacitive reactance and matches the load resistance of the transmission line 2 by a tap-down effect with the second inductor 7.

  Further, Patent Document 2 discloses an antenna matching circuit that can improve the Q value while maintaining the variable frequency range because the circuit loss in the antenna matching circuit greatly affects the antenna gain. .

  In other words, the tunable antenna is a technique that can control the resonance frequency of the antenna, and is effective in reducing the size of a wireless device that is compatible with a system that uses a plurality of frequency bands.

By the way, in recent years, the demand for mobile communication traffic has increased rapidly with the spread of highly functional portable terminals such as smartphones. In order to cope with such an increase in demand for mobile communication traffic, it is necessary to develop new frequency bands that have not been used so far, in addition to improving frequency utilization efficiency by new wireless communication methods.
For example, as one means for improving frequency utilization efficiency, there is an effective utilization of a frequency band that is not used spatially and temporally.

  In general, in a relatively low frequency band (for example, 3 GHz or less) suitable for mobile communication, it is very difficult to secure a continuous bandwidth that can newly accommodate high-speed wireless transmission.

  On the other hand, frequency bands that are not used are discretely present between the bands of the existing communication systems, although they vary temporally and geographically. If these many free frequency bands are bundled and used flexibly, there is a possibility that a wireless communication system capable of realizing high-speed wireless transmission can be accommodated.

  For this purpose, unlike existing communication systems, a communication technique that can flexibly cope with transmission band division and transmission in a plurality of frequency bands is required. As one of such communication technologies, Non-Patent Document 1 discloses a wideband discrete OFDM communication system.

  The broadband discrete OFDM communication system is based on OFDM that multiplexes and transmits information on a plurality of relatively narrow-band carriers (subcarriers) that are orthogonal to each other. In the transceiver, IFFT (Inverse Fast Fourier Transform) ) / FFT (Fast Fourier Transform: Fast Fourier Transform) is used to divide the transmission band by digital signal processing, place subcarriers in the free frequency bands that exist discretely as described above, By bundling and transmitting, the signal transmission using the plurality of discrete vacant frequency bands can be performed relatively easily.

  FIG. 19 is a diagram showing the basic concept of such discrete OFDM.

  In discrete OFDM (hereinafter referred to as NC-OFDM), it is possible to perform communication without affecting existing systems by arranging subcarriers so as not to interfere with signals of other existing communication systems. Become. As a result, a wireless communication system having a wide required transmission bandwidth can be accommodated by bundling and using discrete free frequencies even in a situation where a bandwidth cannot be secured in a specific frequency band.

Japanese Patent Application Laid-Open No. 2007-159083 JP 2009-44561 A

Keiji Takasaki, Goro Hasegawa, Tatsuo Shibata, "Study on Wideband Discrete OFDM Technology", IEICE Technical Report, vol. 113, no. 57, SR2013-16, pp. 83-89, May 2013

  Therefore, the NC-OFDM transmission technique is a transmission technique that secures a required bandwidth by enabling subcarriers to be arranged over a wide band and discretely activating subcarriers according to an empty frequency band. For this reason, there is an advantage that a wireless communication system having a wide required transmission bandwidth can be accommodated by bundling and using discrete vacant frequencies even in a situation where it is not possible to secure a bandwidth grouped in a specific frequency band.

  However, in the NC-OFDM transmission technology, the usable frequency band changes depending on the location and time, so it is originally necessary to have a wideband antenna that includes all the bands that can be candidates for use, but it is installed in a small wireless device. In order to do so, there is a problem that the antenna must be made small and the performance is sacrificed.

  On the other hand, the tunable antenna and its control method that can adjust the resonance frequency, which is a conventional technology for supporting a wide band with a small antenna, can provide services in specific multiple frequency bands such as digital terrestrial broadcasting and mobile phones. When performing the above, the resonance frequency is merely adjusted according to the frequency band to be used. For this reason, as in the NC-OFDM transmission technique, when the usable frequency band changes depending on time and place, a control method for controlling the tunable antenna to an appropriate resonance frequency is as follows. Conventionally, it has not been studied.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to appropriately control a tunable antenna provided in a wireless communication apparatus corresponding to discrete OFDM transmission and to improve transmission characteristics. To provide a wireless communication device and a wireless communication system that can be improved.

According to one aspect of the present invention, a radio communication system that performs communication by discrete orthogonal frequency division multiplex transmission in which subcarriers are arranged and transmitted in at least one of discrete free frequency bands that are not used in an existing radio system Wireless communication device in which the antenna unit, the variable impedance circuit capable of changing the resonance frequency of the antenna unit, and the frequency control for controlling the impedance value of the variable impedance circuit according to the frequency band used in the existing wireless system A transmission / reception processing unit for receiving a signal output from the variable impedance circuit and executing demodulation processing and decoding processing for orthogonal frequency division multiplex transmission with respect to subcarriers arranged in an empty frequency band, The antenna unit includes a plurality of antennas, and the variable impedance circuit includes each antenna. The resonant frequency of the Na changed individually, the corresponding frequency band to the resonance frequency of each antenna are partially overlapped while different from each other, the frequency control unit, depending on the frequency band used by existing wireless systems The variable impedance circuit is controlled, and the transmission / reception processing unit includes a baseband signal processing unit that performs baseband transmission / reception processing corresponding to single input and single output (SISO) transmission and multiple input-multiple output (MIMO) transmission. The signal processing unit performs transmission / reception processing corresponding to MIMO transmission on subcarriers with overlapping frequency bands of each antenna controlled by the frequency control unit in parallel with transmission / reception processing corresponding to SISO transmission on non-overlapping subcarriers. Do.

  Preferably, the variable impedance circuit includes a variable capacitance circuit for making the impedance variable corresponding to each antenna, and the frequency control unit has a correspondence relationship between the capacitance value of the variable capacitance circuit and the frequency band that can be covered in each antenna. The frequency control unit further stores a frequency range storage unit, and the frequency control unit uses the total value of the number of subcarriers that can be used in a frequency band that is not used in the existing radio system in each antenna as a selection criterion. , The capacitance value that maximizes the selection criterion is selected, and the variable capacitance circuit is controlled to the selected capacitance value.

  Preferably, the variable impedance circuit includes a variable capacitance circuit for making the impedance variable corresponding to each antenna, and the frequency control unit is a sub-band that can be used in a frequency band that is not used in an existing wireless system for a plurality of antennas. The selection criterion is an evaluation amount defined based on the total number of carriers and the number of subcarriers corrected for performance degradation from ideal transmission characteristics due to MIMO transmission in the frequency bands overlapping with each antenna. Select the maximum capacitance value, and set the variable capacitance circuit to the selected capacitance value.

  Preferably, the frequency control unit includes a correction coefficient storage unit that stores a correspondence relationship between the frequency band and the correction coefficient for correcting the performance deterioration, and the selection criterion is maximized by referring to the correction coefficient storage unit. Select a capacitance value.

According to another aspect of the present invention, a radio communication system that performs communication by discrete orthogonal frequency division multiplex transmission in which subcarriers are arranged and transmitted in at least one of discrete free frequency bands that are not used in an existing radio system The first wireless communication apparatus includes a first antenna unit, a first variable impedance circuit capable of changing a resonance frequency of the antenna unit, and an existing wireless system. A first frequency control unit that controls the impedance value of the variable impedance circuit according to the frequency band being received, and a signal output from the variable impedance circuit, orthogonal to the subcarriers arranged in the vacant frequency band A first transmission / reception processing unit for performing encoding processing and modulation processing for frequency division multiplex transmission, and a second wireless communication device The second wireless communication apparatus includes a second antenna unit, a second variable impedance circuit capable of changing a resonance frequency of the second antenna unit, and a frequency band used in an existing wireless system. A second frequency control unit for controlling the impedance value of the variable impedance circuit, and a demodulation process for orthogonal frequency division multiplex transmission with respect to the subcarriers arranged in the vacant frequency band, receiving the signal output from the variable impedance circuit And a second transmission / reception processing unit for executing a decoding process, wherein the first and second antenna units each include a first plurality of antennas and a second plurality of antennas, respectively. 2 variable impedance circuits individually change the resonance frequency of the corresponding one of the first and second antennas, and Frequency band corresponding to the resonance frequency of one of the plurality of antennas are partially overlapped while different from each other, the corresponding frequency band to the resonance frequency of each of the second plurality of antennas are partially overlapped while different from each other The first and second frequency control units respectively control the first and second variable impedance circuits according to the frequency band used in the existing wireless system, and the first and second transmission / reception processing units are , Including first and second baseband signal processing units for performing baseband transmission / reception processing corresponding to single input and single output (SISO) transmission and multiple input-multiple output (MIMO) transmission, respectively. The baseband signal processing unit includes sub-bands having overlapping frequency bands of the first and second antennas controlled by the first and second frequency control units, respectively. A reception process corresponding to the MIMO transmission in Yaria, performed in parallel with reception process corresponding to SISO transmission in sub-carriers do not overlap.

  Preferably, any one of the first wireless communication device and the second wireless communication device further includes a frequency use state acquisition unit for acquiring information on a frequency band used in the existing wireless system, The other of the one wireless communication device and the second wireless communication device receives information specifying discrete vacant frequency bands that are not used in the existing wireless system via the control channel.

  According to the present invention, it is possible to appropriately control a tunable antenna provided in a wireless communication apparatus that supports discrete OFDM transmission and improve transmission characteristics.

  In addition, according to the present invention, it is possible to reduce the size of a radio device corresponding to a system that switches between a plurality of frequency bands such as the discrete OFDM method by changing the resonance frequency of the antenna to a corresponding frequency band. Can do.

It is a functional block diagram which shows the example of a structure of the radio | wireless communications system 1000 of this Embodiment. FIG. 2 is a schematic block diagram for explaining the configuration on the receiving side in the configuration of FIG. 1. 3 is a functional block diagram for explaining an example of a more detailed configuration of a radio communication device 2000 on the receiving side. FIG. 4 is a diagram illustrating an example of information stored in a configuration of a variable capacitance circuit 2010 and a frequency range storage unit 2018. FIG. It is a figure which shows the relationship between corresponding | compatible frequency band Fi and a subcarrier. 5 is a flowchart for explaining the operation of a frequency control unit 2016. 6 is a schematic block diagram for explaining a configuration of a wireless communication apparatus 2000 ′ according to a second embodiment. FIG. It is a figure which shows the example of the table which shows the correspondence of received power and an interference correction value. 10 is a flowchart for explaining an operation of a frequency control unit 2016 according to the second embodiment. FIG. 11 is a functional block diagram illustrating a configuration of a wireless communication apparatus 3000 that is a transmission configuration in the wireless communication system of the third embodiment. FIG. 11 is a functional block diagram illustrating a configuration of a wireless communication apparatus 2002 that is a reception configuration in the wireless communication system according to the third embodiment. It is a conceptual diagram which shows the relationship between the frequency range which each antenna covers, and the subcarrier of the empty frequency band used. It is a figure which shows the example of the information stored in the frequency range memory | storage part 1418 of FIG. 12 is a flowchart for explaining an operation of a frequency controller 1416 on the transmission side. FIG. 10 is a functional block diagram illustrating a configuration of a wireless communication device 2002 ′ that is a transmission configuration in the wireless communication system according to the fourth embodiment. 6 is a diagram illustrating a correction coefficient table stored in a MIMO deterioration correction coefficient storage unit 2019. FIG. 10 is a flowchart for explaining an operation of a frequency control unit 2016 according to the fourth embodiment. It is a circuit block diagram of an antenna matching circuit. It is a figure which shows the basic concept of discrete OFDM.

  Hereinafter, configurations of a wireless communication system and a wireless communication apparatus according to an embodiment of the present invention will be described. In the following embodiments, components and processing steps given the same reference numerals are the same or equivalent, and the description thereof will not be repeated unless necessary.

(Basic configuration of the embodiment)
FIG. 1 is a functional block diagram illustrating an example of a configuration of a wireless communication system 1000 according to the present embodiment.

  In the following configuration, although not particularly limited, each function related to transmission will be described as being based on the LTE standard.

  Referring to FIG. 1, in the wireless communication system 1000, since the frequency band that can be transmitted and received is extremely wide, the transmitting side and the receiving side are arranged with high frequency units corresponding to the respective frequencies. FIG. 1 shows a configuration in which four systems are arranged as an example. However, a configuration using a broadband high-frequency device that collectively covers the corresponding frequency band may be used.

  In addition, the downlink (downlink) band from the base station to the user terminal and the uplink (uplink) band from the user terminal to the base station are independently secured in a frequency band (FDD: frequency It is possible to employ a (division multiplexing) configuration or a configuration (TDD: time division multiplexing) used at different times. However, assuming that the vacant frequency band changes geographically and with time, the TDD configuration is more desirable because of the ease of frequency use.

  On the other hand, since the target frequency is different for each high-frequency unit, the quality of the communication path such as propagation attenuation and Doppler frequency is greatly different.

  On the transmission side of the wireless communication system 1000, link adaptation is used in which the modulation scheme and coding rate are changed according to the quality of the communication channel in order to increase the frequency utilization efficiency. The channel encoder 110 performs coding at a corresponding coding rate by error correction coding such as a Turbo code, and executes interleaving processing of the output bit sequence.

  The signal after processing by the channel encoder 110 is provided to the modulation unit 112. Modulation section 112 includes subcarrier mapper 120 and modulator 1124.

  In wireless communication system 1000, IFFT / FFT processing is used to perform signal mapping and demapping to orthogonal subcarriers. By assigning the number of IFFT / FFT points to one high-frequency unit covering a predetermined band, each IFFT / FFT point corresponds to a subcarrier having a predetermined bandwidth. In addition, the structure which performs the division | segmentation of the subcarrier straddling a some RF unit using the IFFT / FFT process collectively may be sufficient.

  Subcarrier mapper 120 arranges a bit sequence corresponding to an IFFT point corresponding to a subcarrier to be transmitted among subcarriers of a high frequency unit on the transmission side (for example, base station apparatus), and modulator 1124 uses a predetermined signal point. To map. For example, QPSK, 16QAM, 64QAM, and the like can be used, and mapping is performed with a modulation multi-level number corresponding to link adaptation.

  Thereafter, the IFFT units 130-1 to 130-4 execute IFFT processing for each high-frequency unit, and the D / A converters 132-1 to 132-4 respectively convert the digital signals into analog signals.

  The outputs of the D / A converters 132-1 to 132-4 are mixed with the IF signal from the IF oscillator 133 and the mixers 134-1 to 134-4, and the local oscillators 140-1 to 140-1 corresponding to each frequency band are mixed. The output of 140-4 is mixed by the mixers 136-1 to 136-4.

  In the radio communication system 1000, the target radio frequency (RF) is, for example, 170 MHz to 1 GHz, and an intermediate frequency (IF) that is usually set lower than the RF frequency can be ensured due to the configuration of the radio transceiver. Have difficulty. Therefore, in FIG. 1, the IF frequency higher than RF is used. A direct conversion method that does not use IF may be employed.

  The functional block 142 is a functional block that executes a function as an FDD duplexer when the FDD is mounted, and executes a function as a TDD switch when the TDD is mounted.

  The signal from block 142 is transmitted from antenna 150 via antenna matching unit 144. The configuration of the antenna matching unit 144 will be described later.

  On the other hand, on the receiving side, a signal received by the antenna 200 is transmitted to the functional block 202 via the antenna matching unit 201. After the function block 202 executes a function as an FDD duplexer or a TDD switch, the output of the function block 202 includes the outputs of the local oscillators 204-1 to 204-4 corresponding to the respective frequency bands and the mixers 210-1 to 210. -4 to mix.

  Further, the outputs of the mixers 210-1 to 210-4 are mixed with the IF signal from the IF oscillator 211 and the mixers 212-1 to 212-4, and are converted into analog / digital by the A / D converters 214-1 to 214-4. (A / D conversion) and FFT processing, which is the inverse processing of IFFT processing, is executed in the FFT units 220-1 to 220-4.

  Signals separated for each subcarrier from FFT sections 220-1 to 220-4 are provided to demodulation section 240.

  Demodulator 240 includes demodulator 2402 and subcarrier demapper 230.

  The demodulator 2402 executes a demodulation process which is an inverse process of the process of the modulator 1124 and a soft decision value generation process.

  For the signal from the demodulator 2402, the subcarrier demapper 230 extracts the data of the corresponding FFT point by the inverse processing of the subcarrier mapper 120. Further, the channel decoder 250 performs deinterleaving processing and error correction decoding processing on the 230 soft decision sequences.

  In the configuration on the transmission side, the channel decoder 110 to the FFT units 130-1 to 130-4 are called the baseband signal processing unit 131, and the mixers 134-1 to 134-4 and the mixers 136-1 to 136-4 are called. Is referred to as an RF unit 133.

  In the configuration on the receiving side, the mixers 210-1 to 210-4 and the mixers 212-1 to 212-4 are referred to as an RF unit 206, and the FFT units 220-1 to 220-4 to the channel decoder 250 are basebands. It will be called a signal processing unit 218.

  In other words, the RF unit is a functional part that performs high-frequency signal processing, and the baseband signal processing unit is a part that performs baseband signal processing, as described below. A structural variation is assumed.

  The configuration on the uplink side is basically the same as the configuration on the downlink side, but the illustration is simplified in FIG.

The feedback channel modulation encoder 280 modulates a control signal that feeds back the reception status of the receiving side (for example, mobile station apparatus) to the base station side in order to perform control such as link adaptation, and the feedback channel demodulation decoder 180 Such a feedback control signal is demodulated.
(Embodiment 1)
FIG. 2 is a schematic block diagram for explaining the configuration of the receiving side in the configuration of FIG.

  When only the configuration on the receiving side in FIG. 1 is extracted and described, it is hereinafter referred to as a wireless communication device 2000.

  In FIG. 2, the functional block 202 is not shown and four systems are collectively shown as one.

  Referring to FIG. 2, antenna matching unit 201 coupled to antenna 200 includes a variable capacitance circuit 2010 provided between antenna 200 and RF unit 206, and a frequency control unit for controlling the impedance of variable capacitance circuit 2010. 2016. The frequency control unit 2016 stores a corresponding frequency band for which the resonance frequency of the antenna 200 is to be adjusted based on the information on the frequency usage status of the existing wireless system from the frequency usage status acquisition unit 2406. including. Based on the information stored in the frequency range storage unit 2018, the frequency control unit 2016 sets the impedance of the variable capacitance circuit 2010 so that the resonance frequency of the antenna 200 corresponds to an empty frequency band. Such an impedance setting process will be described in detail later.

  The configuration of the antenna matching unit 144 is basically the same as the configuration of the antenna matching unit 201.

  In FIG. 2, the frequency control unit 2016 is described as a dedicated circuit for controlling the variable capacitance circuit 2010. However, the circuit is not limited to such a configuration. For example, the operation of the wireless communication device 2000 is performed. The frequency control unit 2016 may be implemented as one function of the control unit that controls the whole.

  FIG. 3 is a functional block diagram for explaining an example of a more detailed configuration of radio communication apparatus 2000 on the receiving side.

  In FIG. 3, the configuration on the receiving side of the configuration of the wireless communication system shown in FIG. 1 is shown in more detail than FIG. 2 with particular attention paid to the processing of the baseband signal.

  For example, also in FIG. 3, the configuration divided into four systems in the configuration of FIG. 1 is shown as one.

  Note that, in the wireless communication apparatus 2000 of the present embodiment, the configuration for performing decoding with soft decision values as described below is merely an example, and another decoding method may be used.

  Referring to FIG. 3, radio communication apparatus 2000 includes antenna matching unit 201 for making the resonant frequency of antenna 200 variable, RF unit 206 that performs high-frequency signal processing of a signal received by antenna 200, and RF unit 206. And an A / D converter 214 for converting an analog signal from the digital signal into a digital signal.

  The FFT unit 220 performs a GI removal unit 2202 for removing the guard interval GI from the digitally converted OFDM symbol, and performs an FFT process on the OFDM symbol from which the guard interval has been removed, thereby converting the time domain signal into a frequency domain signal. An FFT processing unit 2204 for conversion.

  Channel estimation section 2401 performs channel estimation based on the received signal and the pilot signal after FFT.

  Demodulator 240 includes demodulator 2402 and subcarrier demapper 230. Demodulator 2402 includes a plurality of demappers that perform demodulation processing on the output from FFT processing section 2204 for each subcarrier and obtain a soft decision value. Each demapper performs demapping on the corresponding subcarrier signal to generate a bit soft decision value. The demapper outputs a soft decision value of each subcarrier bit based on the estimation result of the channel estimation unit 2401.

  The frequency utilization status acquisition unit 2406 acquires own system subcarrier information used for NC-OFDM transmission and subcarrier information corresponding to a frequency used in an existing radio system. Here, for such “subcarrier information”, for example, corresponding information is acquired by decoding a cognitive pilot channel or a cognitive control channel. Here, the cognitive pilot channel (CPC) is a channel that transmits frequency use information of a specific part of a band in a certain region. A CPC may be placed in that particular band or in an internationally determined frequency band outside that band. For example, the following documents disclose CPC.

Reference: ITU-R M.2225: Introduction to Cognitive Radio Systems in the Land Mobile Service (Section 4.1.1.2)
The subcarrier demapper 230 includes a used subcarrier extraction unit 2404.

  The used subcarrier extraction unit 2404 softens the demodulated signal corresponding to the own system subcarrier used for NC-OFDM transmission acquired from the frequency utilization status acquisition unit 2406 out of the demodulated soft decision values output from the demapper. Only the judgment value is extracted.

  Note that the demapper may be configured such that only the one corresponding to the own system subcarrier used for NC-OFDM transmission operates.

The channel decoder 250 receives a deinterleaver 2502 that performs deinterleave processing that is reverse processing of interleave on the bit signal output from the used subcarrier extraction unit 2404, and receives the deinterleaved signal and the soft decision value as inputs. It includes an error correction decoder 2504 that outputs a hard decision decoding bit, and a CRC decoder 2506 that decodes a CRC (cyclic redundancy check) code and detects an error.
(Control of variable capacitance circuit 2010)
Hereinafter, the configuration of the variable capacitance circuit 2010 and the control of the frequency control unit 2016 will be described.

  FIG. 4 is a diagram illustrating an example of information stored in the configuration of the variable capacitance circuit 2010 and the frequency range storage unit 2018.

  As shown in FIG. 4A, the variable capacitance circuit 2010 includes a variable capacitance C1 and an inductor 2012 provided in series from the antenna side in the direction of the RF section, and a junction node n11 between one end of the variable capacitance C1 and the inductor 2012. A variable capacitor C2 provided between the inductor 2012 and the inductor 2014 provided between the other end ground of the inductor 2012 is included.

  Note that the configuration of the variable capacitance circuit 2010 is not limited to the case where the capacitance is variable as shown in FIG. 4A, and other configurations may be used as long as the impedance of the antenna can be converted.

  In other words, the variable capacitance circuit 2010 can change the resonance frequency of the antenna by switching the capacitance values (C1, C2) of the series-connected and shunt-connected capacitors according to the control information from the frequency control unit 2016 with a switch. it can.

  The frequency control unit 2016 determines a frequency band corresponding to the antenna according to the vacant frequency information acquired from the frequency usage status acquisition unit 2406 and controls each capacitance value of the variable capacitance circuit 2010. As shown in FIG. 4B, the correspondence relationship between the corresponding frequency band and the capacitance value (control bit) of the variable capacitance circuit is stored in advance in the frequency range storage unit 2018 as a table.

  In the configuration of the variable capacitance circuit 2010 in FIG. 4A, four types of capacitance values can be switched and used in each of the variable capacitances C1 and C2. In the table in FIG. The case where the corresponding frequency band is memorize | stored with respect to each is illustrated.

  Note that each frequency band in FIG. 4B may be set to partially overlap.

  FIG. 5 is a diagram illustrating the relationship between the corresponding frequency band Fi and the subcarriers.

  FIG. 5 illustrates a possible frequency band Fi (i = 1 to M) and a corresponding subcarrier and a used frequency band of an existing wireless system, where M is a possible combination of capacitance values of the variable capacitance circuit. Yes.

  As will be described below, the frequency control unit 2016 determines, based on the information obtained from the frequency usage status acquisition unit, the capacitance value of the variable capacitance circuit that includes the most usable subcarriers in the corresponding frequency band. Based on the selection criterion “select”, the corresponding frequency band Fi is selected, and each capacitance value of the variable capacitance circuit is set so as to be such a frequency band Fi.

  FIG. 6 is a flowchart for explaining the operation of the frequency control unit 2016.

  Referring to FIG. 6, frequency control unit 2016 acquires usable subcarrier information from frequency usage status acquisition unit 2406 (S100), and initially sets variables m and N (m) used for processing as follows. (S102).

Here, m (1 ≦ m ≦ M) is a variable for specifying the corresponding frequency band Fi, and N (m) is the number of subcarriers that can be used in the corresponding frequency band Fm. M represents the number of possible combinations of capacitance values of the variable capacitance circuit as described above.

  Subsequently, the frequency control unit 2016 uses the number of subcarriers N (m) that can be used (not corresponding to the used frequency band of the existing wireless system) included in the frequency band Fm based on the information from the frequency usage status acquisition unit 2406. Is counted (S104).

  If the variable m is smaller than M (No in S106), the value of m is incremented by 1, and the process returns to Step S104.

  On the other hand, if the variable m is greater than or equal to M (Yes in S106), the frequency control unit 2016 sets the m tilde (hereinafter referred to as “−” to the head of m) that is the value of the variable m that maximizes N (m). The extracted symbol is referred to as “m tilde”) (S110).

Through the above processing, the frequency control unit 2016 controls each capacitance value of the variable capacitance circuit 2010 to be in a frequency band corresponding to m tilde (S112).

By adopting such a configuration, by using a tunable antenna, the resonance frequency of the antenna can be changed to the corresponding frequency band, thereby realizing a reduction in the size of the corresponding wireless device, and a plurality of such as the NC-OFDM method. It is possible to secure a usable bandwidth in a system that switches between discrete frequency bands.
(Embodiment 2)
In the first embodiment, the configuration of “selecting the capacitance value of the variable capacitance circuit in which the most usable subcarriers are included in the corresponding frequency band” has been described on the premise of the existence of the existing wireless system.

  In the second embodiment, a radio communication apparatus that selects the corresponding frequency in consideration of the interference effect received from the existing system in the selection of the corresponding frequency band of the first embodiment will be described.

  That is, the radio communication apparatus according to the second embodiment obtains received power in the corresponding frequency band prior to communication, and performs frequency control by selecting the corresponding frequency in consideration of the interference effect received from the existing system. It is.

  FIG. 7 is a schematic block diagram for explaining a configuration of radio communication apparatus 2000 ′ according to the second embodiment. FIG. 7 explains the configuration of the second embodiment in comparison with FIG. 2 of the first embodiment.

  Therefore, below, a different point from the structure of FIG. 2 is demonstrated, and description is not repeated by attaching | subjecting a common code | symbol to a common part.

  Referring to FIG. 7, in addition to the configuration of FIG. 2, radio communication apparatus 2000 ′ receives reception for acquiring received power in each corresponding frequency band in a frequency region covered by a tunable antenna prior to communication. A signal power acquisition unit 2407 is further provided. In addition to the frequency range storage unit 2018, the frequency control unit 2016 stores an interference correction value determined according to the received power acquired by the received signal power acquisition unit 2407 for each corresponding frequency band. An interference correction value storage unit 2017 is included.

The reception signal power acquisition unit 2407 is not particularly limited. For example, as shown in FIG. 5, the frequency control unit 2016 sequentially switches the frequency bands F _{1 to} F _M before starting communication, Measure the received power in the corresponding frequency band.

  FIG. 8 is a diagram illustrating an example of a table indicating a correspondence relationship between the received power and the interference correction value.

  Note that such a table itself is also stored in advance in the interference correction value storage unit 2017.

  Here, it is assumed that the interference correction value is a non-negative integer that increases as the received power increases.

  FIG. 9 is a flowchart for explaining the operation of the frequency control unit 2016 according to the second embodiment.

  Referring to FIG. 9, frequency control unit 2016 acquires usable subcarrier information from frequency usage status acquisition unit 2406 (S200), and uses variables m, N (m), and K (m) used for processing. Initialization is performed as follows (S202).

Here, m (1 ≦ m ≦ M) is a variable for specifying the corresponding frequency band Fi, N (m) is the number of subcarriers that can be used in the corresponding frequency band Fm, and K (m ) Is an interference correction value of the corresponding frequency band Fm. M represents the number of possible combinations of capacitance values of the variable capacitance circuit as described above.

  Subsequently, the frequency control unit 2016 sets each capacitance value in the variable capacitance circuit 2010 to a capacitance value corresponding to the corresponding frequency band Fm (S204).

The reception signal power acquisition unit 2407 acquires the reception power of the set corresponding frequency band Fm based on, for example, an average value of the square of the complex amplitude value of the reception signal, and the frequency control unit 2016 Based on the table stored in the value storage unit 2017, a correction value K (m) corresponding to the received power is acquired (S206).
Subsequently, the frequency control unit 2016 uses the number of subcarriers N (m) that can be used (not corresponding to the used frequency band of the existing wireless system) included in the frequency band Fm based on the information from the frequency usage status acquisition unit 2406. Is counted (S208).

  If the variable m is smaller than M (No in S210), the value of m is incremented by 1, and the process returns to step S204.

  On the other hand, if the variable m is equal to or greater than M (Yes in S210), the frequency control unit 2016 calculates m tilde that is the value of the variable m that maximizes the evaluation amount (N (m) −K (m)). Extraction is performed according to the following equation (S214).

Through the above processing, the frequency control unit 2016 sets and fixes each capacitance value of the variable capacitance circuit 2010 to be a frequency band corresponding to m tilde (S216).

Even with such a configuration, by using a tunable antenna, the resonance frequency of the antenna can be changed to the corresponding frequency band, so that it can be used for a system that switches between a plurality of discrete frequency bands such as the NC-OFDM system. It is possible to reduce the size of the wireless device. In addition, since communication is performed by preferentially selecting subcarriers in a region where the received power from the existing system is smaller, it is possible to maintain higher communication quality.
(Embodiment 3)
In the first embodiment and the second embodiment, the configuration of basically one tunable antenna has been described.

  In Embodiment 3, a configuration in the case where there are a plurality of tunable antennas will be described. In the following, a case where there are two tunable antennas will be described as a plurality of examples, but the number of tunable antennas may be larger.

  FIG. 10 is a functional block diagram illustrating the configuration of radio communication apparatus 3000 that is the configuration on the transmission side in the radio communication system according to the third embodiment.

The characteristics of the wireless communication system of the third embodiment can be summarized as follows:
i) The wireless communication device is provided with a plurality of antennas, and the corresponding frequency band is changed by switching the capacitance value of the variable capacitance circuit connected to each antenna.

  ii) Generally, the set frequency range is different for each antenna, but partially overlaps.

  iii) The frequency control unit simultaneously controls the capacitance value of the variable capacitance circuit connected to each antenna according to the usable subcarrier information acquired by the frequency usage status acquisition unit.

  iv) As a result of selecting the capacity value by the frequency control unit, the baseband signal processing unit supports MIMO (multiple-input and multiple-output) transmission in a subcarrier corresponding to a band in which frequency bands corresponding to each antenna overlap. The transmission / reception processing corresponding to SISO (single input and single output) transmission is performed on the non-overlapping subcarriers.

  Referring to FIG. 10, baseband signal processing section 131 includes a channel encoder 110, a subcarrier demapper 120, and a modulator 1124.

  As described in Embodiment 1, the channel encoder 110 performs processing such as error correction coding such as a Turbo code and interleaving.

  The frequency utilization status acquisition unit 1406 acquires the own system subcarrier information used for NC-OFDM transmission and the subcarrier information corresponding to the frequency used in the existing radio system, as in the first embodiment.

  Based on the information from the frequency usage status acquisition unit 1406, the subcarrier mapper 120 allocates transmission symbols to subcarriers corresponding to bands where frequency bands corresponding to each antenna overlap and subcarriers not overlapping.

  The modulator 1124 includes a MIMO modulation unit 1124.1 that performs modulation on subcarriers corresponding to bands in which frequency bands corresponding to each antenna overlap, and SISO modulation that performs modulation on subcarriers corresponding to bands in which frequency bands do not overlap. Part 1124.2. In the MIMO modulation unit 1124.1 and the SISO modulation unit 1124.2, the modulation scheme (for example, the multi-level number) may be set independently.

  The baseband signal processing unit 131 further includes a weighting processing unit 124 for performing weight matrix multiplication processing for the MIMO communication scheme on the output from the MIMO modulation unit 1124.1, and the weighting processing unit 124. The IFFT unit 130.1 and the IFFT unit 130.2 for executing IFFT processing are included in the signal. Note that weighting in MIMO communication can be performed by a well-known method, and a description thereof will be omitted. For example, in LTE, this corresponds to a process of weight combining a modulated signal with a designated precoding matrix.

  The modulation signal from the SISO modulation unit 1124.2 is supplied to, for example, one of the IFFT unit 130.1 and the IFFT unit 130.2. It may be configured to switch which of the modulation signals from the SISO modulation unit 1124.2 is given depending on the reception situation.

  The output of IFFT unit 130.1 is given to variable capacitance circuit 1410.1 via D / A converter 132.1 and RF unit 133.1, and the output of IFFT unit 130.2 is supplied to D / A converter 132. .2 and the RF section 133.2, and is supplied to the variable capacitance circuit 1410.2.

  Based on the information from the frequency usage status acquisition unit 1406 and the table stored in the frequency range storage unit 1418, the frequency control unit 1416 performs variable capacitance circuit 1410.1 and variable capacitance circuit 1410. Set the impedance of 2.

  Antenna 150.1 and antenna 150.2 send signals from variable capacitance circuit 1410.1 and variable capacitance circuit 1410.2, respectively.

  FIG. 11 is a functional block diagram illustrating a configuration of radio communication apparatus 2002 that is a reception configuration in the radio communication system according to the third embodiment.

  Referring to FIG. 11, radio communication apparatus 2002 includes two antennas 200.1 and 200.1 for receiving signals, and signals from antenna 200.1 and antenna 200.2 are: These are applied to variable capacitance circuit 2011.1 and variable capacitance circuit 2010.2, respectively.

  Based on the information from the frequency usage status acquisition unit 2016 and the table stored in the frequency range storage unit 2018, the frequency control unit 2016 is similar to the frequency control unit 1416 and includes the variable capacitance circuit 2010.1 and the variable capacitance circuit. Set the impedance of 2012.2.

  On the receiving side, the frequency usage status acquisition unit 2406 may acquire information on frequency usage status in the same manner as the frequency usage status acquisition unit 1406, or, for example, a control channel may be obtained from the transmission side. On the basis of the control information transmitted via the network, information regarding subcarriers currently used for communication can be obtained. In the following description, it is assumed that the frequency usage status acquisition unit 2406 acquires information from the transmission side through the control channel.

  The signal from the variable capacitance circuit 2010.1 is given to the FFT unit 220.2 via the RF unit 206.1 and the A / D converter 214.1, and the signal from the variable capacitance circuit 2010.2 is RF This is provided to FFT unit 220.2 via unit 206.2 and A / D converter 214.2.

  The baseband signal processing unit 218 includes an FFT unit 220.1 and an FFT unit 220. for performing FFT processing on the signals from the A / D converter 214.1 and the A / D converter 214.2, respectively. 2 and a weighting processing unit 224 for performing weight matrix multiplication processing for the MIMO communication scheme on the signal from the FFT unit 220.1.

  The demodulator 2402 receives the signal from a predetermined one of the MIMO demodulator 2402.1 and the FFT unit 220.1 or 220.2 for performing demodulation on the signal from the weighting processor 124. And a SISO demodulator 2402.2 for performing demodulation processing. In the MIMO demodulator 1124.1 and the SISO demodulator 1124.2, as described above, the modulation scheme (for example, multi-value number) of the signal to be processed may be set independently. In this case, information on the set modulation scheme is notified from the transmission side to the reception side via the control channel.

  Based on the information from the frequency usage status acquisition unit 2406, the subcarrier demapper 230 corresponds to the received subcarrier to the band in which the frequency band corresponding to each antenna overlaps and in which MIMO communication is performed. A subcarrier is divided into a non-overlapping band and a subcarrier performing SISO communication.

  The channel decoder 250 performs deinterleaving processing and error correction decoding processing.

  In the above description, the frequency usage status acquisition unit 2406 on the reception side acquires information on subcarriers and subcarrier communication schemes (MIMO or SISO) used by the control channel from the transmission side. It is assumed that the information on the modulation scheme is also transmitted from the transmission side to the reception side through the control channel. However, for example, the reception side frequency usage status acquisition unit 2406 acquires the own system subcarrier information used for NC-OFDM transmission and the subcarrier information corresponding to the frequency used in the existing radio system, and the transmission side frequency. Based on the control information transmitted from the receiving side via the control channel, the usage status acquisition unit 1406 acquires information on the subcarrier and communication method currently used for communication, and information on the modulation method also It is good also as a structure notified to the transmission side by the control channel from the reception side.

  10 and FIG. 11, the transmitting side and the receiving side are described as separate wireless communication devices. However, as a configuration for executing transmission processing and reception processing in one wireless communication device, one wireless communication device is used. The structure mounted in a communication apparatus may be sufficient.

  FIG. 12 is a conceptual diagram showing the relationship between the frequency range covered by each antenna and the subcarriers in the unused frequency band used.

  Referring to FIG. 12, antenna 200.1 covers the low frequency side frequency range as the operating frequency band, and antenna 200.2 covers the high frequency side frequency range as the operating frequency band. , There shall be overlap.

  The radio communication system of the present embodiment performs MIMO communication in a subcarrier corresponding to an empty frequency band of an existing radio system that is an overlapping region of the operating frequency bands of the antenna 200.1 and the antenna 200.2. In the subcarrier corresponding to the vacant frequency band of the existing radio system in which the operating frequency band of the antenna 200.1 and the operating frequency band of the antenna 200.2 do not overlap, the radio communication system of the present embodiment performs SISO communication. Do.

  FIG. 13 is a diagram illustrating an example of information stored in the frequency range storage unit 1418 of FIG. It is assumed that similar information is also stored in the frequency range storage unit 2018 in FIG.

  Further, the configurations of the variable capacitance circuits 1410.1, 1410.2, 2010.1 and 2010.2 of the present embodiment are basically the same as those shown in FIG. .

  The frequency control unit 1416 determines a frequency band corresponding to the antenna according to the vacant frequency information acquired from the frequency usage status acquisition unit 1406, and controls the capacitance values of the variable capacitance circuits 1410.1 and 1410.2. As shown in FIG. 13, the correspondence relationship between the corresponding frequency band and the capacitance values (control bits) of the variable capacitance circuits 1410.1 and 1410.2 is stored in advance in the frequency range storage unit 1418 as a table.

  Note that it is desirable that the characteristics of the antenna and the capacity variable circuit are set so that the control bit and the corresponding frequency band of the antenna have the same correspondence relationship on the transmission side and the reception side.

  FIG. 14 is a flowchart for explaining the operation of the frequency controller 1416 on the transmission side. Here, as an example, on the transmission side, the subcarrier to be used and the communication method of subcarrier MIMO communication or SISO communication are determined.

Referring to FIG. 14, frequency control unit 1416 obtains usable subcarrier information from the frequency utilization state obtaining unit (S300), and variables m ₁ and N ₁ (m ₁ ) used for processing for the variable capacitance circuit. Is initialized as follows (S302).

Here, m ₁ (1 ≦ m ₁ ≦ M ₁ ) is a variable for specifying the corresponding frequency band Fi of the antenna 150.1, and N ₁ (m ₁ ) can be used in the corresponding frequency band Fm. The number of subcarriers. M ₁ indicates the number of possible combinations of capacitance values of the variable capacitance circuit.

Subsequently, the frequency control unit 1416 uses the number of usable subcarriers N ₁ (not corresponding to the used frequency band of the existing wireless system) included in the frequency band Fm ₁ based on the information from the frequency usage status acquisition unit 1406 ( m ₁ ) is counted (S304).

On the other hand, the frequency control unit 1416 initializes variables m ₂ and N ₂ (m ₂ ) used for processing for the variable capacitance circuit 1410.2 as follows (S306).

m ₂ (1 ≦ m ₂ ≦ M ₂ ) is a variable for specifying the corresponding frequency band F′m ₂ of the antenna 150.2, and N ₂ (m ₂ ) is the corresponding frequency band F′m ₂ . The number of usable subcarriers. M ₂ represents the number of possible combinations of capacitance values of the variable capacitance circuit.

Subsequently, the frequency control unit 1416 uses the number N of subcarriers that can be used (not corresponding to the use frequency band of the existing wireless system) included in the frequency band F′m ₂ based on the information from the frequency use state acquisition unit 1406. ₂ (m ₂ ) is counted (S308).

The frequency control unit 1416 extracts subcarriers that overlap between the antennas (S310), and calculates an evaluation amount G (m ₁ , m ₂ ) according to the following mathematical formula (S412).

Next, if the variable m ₂ is smaller than M ₂ (No in S314), the frequency control unit 1416 increments the value of m ₂ by 1 (S316), returns the processing to Step S308, and sets the variable m _{If 2} is equal to or greater than M ₂ (Yes in S314), the process proceeds to step S318.

Furthermore, if the variable m ₁ is smaller than M ₁ (No in S318), the frequency control unit 1416 increments the value of m ₁ by 1 (S320), and returns the process to step S304.

On the other hand, if the variable m ₁ is equal to or greater than M ₁ (Yes in S318), the frequency control unit 1416 determines that the m ₁ tilde that is the value of the variable m ₁ that maximizes the evaluation amount G (m ₁ , m ₂ ) and The m ₂ tilde which is the value of the variable m ₂ is extracted according to the following formula (S322).

When there are a plurality of variables m ₁ and m ₂ that maximize the evaluation amount at each antenna in the above-described processing, the number of multiplexed subcarriers by MIMO with high frequency utilization efficiency is used from the viewpoint of effective use of frequency resources. Are selected so that the variable m ₁ tilde and the variable m ₂ tilde are maximized (S324).

With the above processing, the frequency control unit 1416 controls each capacitance value of the variable capacitance circuit 1410.1 to be a frequency band corresponding to m ₁ tilde, and each capacitance value of the variable capacitance circuit 1410.2 is Control is performed so that the frequency band corresponds to m ₂ tilde (S326).

  When there is an overlap in the operating frequency bands of the antennas 200.1 and 200.2 set in this way, as shown in FIG. 12, the frequency control unit 2016 uses the subcarrier demapper 230 in the overlapped frequency band. On the other hand, an instruction is given to perform MIMO communication for the corresponding subcarrier and perform SISO communication in the non-overlapping frequency band.

  Note that the frequency controller 2016 on the receiving side uses the information notified via the control channel from the transmitting side so that the subcarriers subjected to MIMO communication overlap the operating frequency bands of the two antennas. For the subcarriers that are subjected to SISO communication, the capacitance values of the variable capacitance circuits 2010.1 and 2010.2 are set so as to fall within the operating frequency band of at least one antenna. Further, the frequency control unit 2016 notifies the subcarrier demapper 230 of subcarriers for MIMO communication and subcarriers for SISO communication.

  By adopting such a configuration, the tunable antenna can be used to switch between multiple discrete frequency bands such as the NC-OFDM system by changing the resonance frequency of the antenna to the corresponding frequency band. It is possible to reduce the size of the wireless device.

In addition, with such a configuration, the MIMO transmission can be performed for some subcarriers, so that it is possible to realize high-speed transmission without widening the frequency band using a plurality of transmission / reception antennas.
(Embodiment 4)
In the third embodiment, there are a plurality of tunable antennas and a region where the operating frequency bands of the plurality of antennas overlap, and a subcarrier corresponding to a free frequency of an existing wireless system is configured to perform MIMO communication. explained.

  However, even when performing MIMO transmission, it is generally difficult to obtain a throughput that is several times the number of antennas corresponding to the same frequency as ideally assumed, and the amount of degradation depends on the frequency. That is, under the condition where the distance between antennas is the same, the lower the frequency band, the higher the correlation between the antennas, and at the same time, radiation efficiency deterioration due to coupling between elements occurs, and the characteristics are likely to deteriorate.

  Therefore, in the fourth embodiment, the configuration of the third embodiment is modified, and an evaluation amount in which a correction coefficient corresponding to the subcarrier position where the corresponding frequency band of each antenna overlaps is introduced from the MIMO degradation correction coefficient table, A configuration for performing appropriate control by controlling the frequency of each antenna will be described.

  FIG. 15 is a functional block diagram illustrating a configuration of radio communication apparatus 2002 ′ that is a transmission configuration in the radio communication system according to the fourth embodiment. FIG. 15 corresponds to FIG. 11 of the third embodiment.

  Therefore, in radio communication apparatus 2002 ′ of Embodiment 4 described below, frequency utilization status acquisition section 2406 on the receiving side uses its own system subcarrier information used for NC-OFDM transmission and the frequency used in the existing radio system. The frequency usage status acquisition unit 1406 (not shown) on the transmission side is currently used for communication based on control information transmitted from the reception side via the control channel. In the following description, it is assumed that the information on the subcarriers and communication schemes being acquired and the information on the modulation schemes are also notified from the reception side to the transmission side through the control channel. However, as in the third embodiment, a configuration in which the roles of the reception side and the transmission side are interchanged may be used.

  The frequency control unit 2016 on the receiving side sets the capacitance values of the capacitance variable circuits 2010.1 and 2010.2 according to the procedure described later. If the operating frequency bands of the two antennas overlap, the frequency is overlapped. The subcarriers for MIMO communication and the subcarriers for SISO communication are subcarrier demappers so that MIMO communication is performed on subcarriers in the operating frequency band and SISO communication is performed on subcarriers where the operating frequency bands do not overlap. 230 is notified.

  Referring to FIG. 15, radio communication apparatus 2002 ′ is different from the configuration of radio communication apparatus 2002 in that frequency control unit 2016 is provided with a MIMO deterioration correction coefficient storage unit 2019 as described in detail later. The configuration is such that the set value of the capacitance of the variable capacitance circuit corresponding to the antenna is calculated based on the evaluation amount corrected with the MIMO deterioration correction coefficient. Since the other points are the same as the configuration of wireless communication apparatus 2002 described in FIG. 11, the same parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 16 is a diagram illustrating a correction coefficient table stored in the MIMO deterioration correction coefficient storage unit 2019.

  As shown in FIG. 16, values acquired in advance through experiments or the like are stored as a table so that the value of the correction coefficient αq decreases as the frequency of the frequency band F ″ Q decreases.

In the following, for simplicity of explanation, as an example, it is assumed that the corresponding frequency bands of two antennas corresponding to the same control bit are set to be the same, and correction for each common frequency band is performed. It is assumed that the coefficient αq is set as shown in the table of FIG. Therefore, in the following description, it is assumed that M ₁ = M ₂ = Q (= 16). However, there is no limitation in such a case as long as the frequency range covered as a whole is common.

  FIG. 17 is a flowchart for explaining the operation of the frequency control unit 2016 according to the fourth embodiment.

Referring to FIG. 17, frequency control unit 2016 acquires usable subcarrier information from frequency usage status acquisition unit 2406 (S400), and uses variables m ₁ and N ₁ used for processing for variable capacitance circuit 2010.1. (M ₁ ) is initialized as follows (S402).

Here, m ₁ (1 ≦ m ₁ ≦ M ₁ ) is a variable for specifying the corresponding frequency band Fm ₁ of the antenna 200.1, and N ₁ (m ₁ ) is used in the corresponding frequency band Fm ₁ . The number of possible subcarriers. M ₁ indicates the number of possible combinations of capacitance values of the variable capacitance circuit.

Subsequently, the frequency control unit 2016 uses the number of usable subcarriers N ₁ (not corresponding to the used frequency band of the existing radio system) included in the frequency band Fm ₁ based on the information from the frequency usage status acquisition unit 2406 ( m ₁ ) is counted (S404).

On the other hand, the frequency control unit 2016 initializes the variables m ₂ and N ₂ (m ₂ ) used for processing for the variable capacitance circuit 2010. ₂ as follows (S406).

m ₂ (1 ≦ m ₂ ≦ M ₂ ) is a variable for specifying the corresponding frequency band F′m ₂ of the antenna 200.2, and N ₂ (m ₂ ) is the corresponding frequency band F′m ₂ . The number of usable subcarriers. M ₂ represents the number of possible combinations of capacitance values of the variable capacitance circuit.

Subsequently, the frequency control unit 2016 uses the number N of subcarriers that can be used (not corresponding to the used frequency band of the existing wireless system) included in the frequency band F′m ₂ based on the information from the frequency usage status acquisition unit 1406. ₂ (m ₂ ) is counted (S408).

The frequency control unit 1416 extracts subcarriers that overlap between the antennas (S410), and calculates an evaluation amount G (m ₁ , m ₂ ) according to the following formula (S412).

Next, if the variable m ₂ is smaller than M ₂ (No in S414), the frequency control unit 2016 increments the value of m ₂ by 1 (S416), returns the process to Step S408, and sets the variable m _{If 2} is equal to or greater than M ₂ (Yes in S414), the process proceeds to step S418.

Furthermore, if the variable m ₁ is smaller than M ₁ (No in S418), the frequency control unit 2016 increments the value of m ₁ by 1 (S420), and returns the process to step S404.

On the other hand, if the variable m ₁ is equal to or greater than M ₁ (Yes in S418), the frequency control unit 2016 includes the m ₁ tilde that is the value of the variable m ₁ for which the evaluation amount G (m ₁ , m ₂ ) is maximum, and The m ₂ tilde, which is the value of the variable m ₂ , is extracted according to the following formula (S422).

With the above processing, the frequency control unit 2016 controls each capacitance value of the variable capacitance circuit 2011. ₁ to be a frequency band corresponding to m ₁ tilde, and each capacitance value of the variable capacitance circuit 2010. 2 is Control is performed so that the frequency band corresponds to m ₂ tilde (S424).

  When there is an overlap in the operating frequency bands of the antennas 200.1 and 200.2 set in this way, as shown in FIG. 12, the frequency control unit 2016 uses the subcarrier demapper 230 in the overlapped frequency band. On the other hand, an instruction is given to perform MIMO communication for the corresponding subcarrier and perform SISO communication in the non-overlapping frequency band.

  Note that the frequency control unit 1416 on the transmission side uses the information notified via the control channel from the reception side so that the subcarriers subjected to MIMO communication overlap the operating frequency bands of the two antennas. As for the subcarriers that are subjected to SISO communication, the capacitance values of the capacitance variable circuits 1410.1 and 1410.2 are set so as to fall within the operating frequency band of at least one antenna. Moreover, the frequency control unit 1416 instructs the subcarrier mapper 120 to perform subcarriers for MIMO communication and subcarriers for SISO communication.

  With such a configuration, the tunable antenna allows the antenna resonance frequency to be changed to the corresponding frequency band, thereby enabling a radio apparatus compatible with a system that switches between a plurality of frequency bands such as the NC-OFDM system. Downsizing can be realized.

  In addition, with such a configuration, the MIMO transmission can be performed for some subcarriers, so that it is possible to realize high-speed transmission without widening the frequency band using a plurality of transmission / reception antennas.

  With the configuration as described above, it is possible to appropriately control the tunable antenna provided in the wireless communication apparatus that supports discrete OFDM transmission, and to improve the transmission characteristics.

  Embodiment disclosed this time is an illustration of the structure for implementing this invention concretely, Comprising: The technical scope of this invention is not restrict | limited. The technical scope of the present invention is shown not by the description of the embodiment but by the scope of the claims, and includes modifications within the wording and equivalent meanings of the scope of the claims. Is intended.

  110 channel encoder, 112 modulation unit, 120 subcarrier mapper, 130-1 to 130-4 IFFT unit, 132-1 to 132-4 D / A converter, 133, 211 IF oscillator, 134-1 to 134-4, 136-1 to 136-4, 210-1 to 210-4, 212-1 to 212-4 Mixer, 140-1 to 140-4, 204-1 to 204-4 Local oscillator, 150, 200 Antenna, 180 Feedback Channel demodulation decoder, 214-1 to 214-4 A / D converter, 220-1 to 220-4 FFT unit, 230 subcarrier demapper, 240 demodulator, 250 channel decoder, 280 feedback channel modulation encoder, 1000 wireless communication System, 2000, 20002, 2002 ', 3000 Wireless communication Location.

Claims (6)

A wireless communication apparatus in a wireless communication system that performs communication by discrete orthogonal frequency division multiplex transmission in which subcarriers are arranged and transmitted in at least one of discrete free frequency bands that are not used in an existing wireless system,
An antenna section;
A variable impedance circuit capable of changing a resonance frequency of the antenna unit;
A frequency control unit for controlling the impedance value of the variable impedance circuit according to the frequency band used in the existing wireless system;
A transmission / reception processing unit for receiving a signal output from the variable impedance circuit and executing demodulation processing and decoding processing for orthogonal frequency division multiplex transmission on subcarriers arranged in the vacant frequency band;
The antenna unit includes a plurality of antennas,
The variable impedance circuit individually changes the resonance frequency of each antenna, and the frequency bands corresponding to the resonance frequency of each of the antennas are different from each other and partially overlap,
The frequency control unit controls the variable impedance circuit according to a frequency band used in the existing wireless system,
The transmission / reception processing unit includes a baseband signal processing unit that performs baseband transmission / reception processing corresponding to SISO (single input and single output) transmission and MIMO (Multiple Input-Multiple Output) transmission,
The baseband signal processing unit includes transmission / reception processing corresponding to MIMO transmission on subcarriers with overlapping frequency bands of each antenna controlled by the frequency control unit, and transmission / reception processing corresponding to SISO transmission on non-overlapping subcarriers. A wireless communication device that performs in parallel. The variable impedance circuit includes a variable capacitance circuit for making the impedance variable corresponding to each of the antennas,
The frequency control unit further includes a frequency range storage unit that stores a correspondence relationship between a capacitance value of the variable capacitance circuit and a frequency band that can be covered in each antenna.
The frequency control unit refers to the information in the frequency range storage unit with reference to the information in the frequency range storage unit, using a total value of the number of subcarriers that can be used in a frequency band that is not used in the existing radio system in each antenna as a selection criterion. The radio communication apparatus according to claim 1, wherein a capacitance value that maximizes a reference is selected, and the variable capacitance circuit is controlled to the selected capacitance value. The variable impedance circuit includes a variable capacitance circuit for making the impedance variable corresponding to each of the antennas,
The frequency control unit includes a total number of subcarriers that can be used in a frequency band that is not used in the existing radio system in the plurality of antennas, and ideal transmission characteristics by MIMO transmission in frequency bands that overlap each of the antennas. The evaluation amount defined on the basis of the number of subcarriers corrected for performance degradation from is used as a selection criterion, a capacitance value that maximizes the selection criterion is selected, and the variable capacitance circuit is set to the selected capacitance value The wireless communication apparatus according to claim 1.   The frequency control unit includes a correction coefficient storage unit that stores a correspondence relationship between a frequency band and correction coefficients for correcting performance degradation, and the selection criterion is maximized by referring to the correction coefficient storage unit. The wireless communication apparatus according to claim 3, wherein a capacity value is selected. A wireless communication system that performs communication by discrete orthogonal frequency division multiplex transmission in which subcarriers are arranged and transmitted in at least one of discrete free frequency bands that are not used in an existing wireless system,
A first wireless communication device, wherein the first wireless communication device comprises:
A first antenna unit;
A first variable impedance circuit capable of changing a resonance frequency of the antenna unit;
A first frequency control unit that controls an impedance value of the variable impedance circuit according to a frequency band used in the existing wireless system;
A first transmission / reception processing unit for receiving a signal output from the variable impedance circuit and executing encoding processing and modulation processing for orthogonal frequency division multiplex transmission on subcarriers arranged in the vacant frequency band; Including
A second wireless communication device, wherein the second wireless communication device comprises:
A second antenna section;
A second variable impedance circuit capable of changing a resonance frequency of the second antenna unit;
A second frequency control unit for controlling the impedance value of the variable impedance circuit according to the frequency band used in the existing wireless system;
A second transmission / reception processing unit for receiving a signal output from the variable impedance circuit and executing demodulation processing and decoding processing for orthogonal frequency division multiplex transmission on subcarriers arranged in the vacant frequency band; Including
Each of the first and second antenna units includes a first plurality of antennas and a second plurality of antennas,
The first and second variable impedance circuits individually change the resonance frequencies of corresponding antennas of the first and second antennas, and the resonance frequencies of the respective first antennas. corresponding frequency band is partially overlapped with different from each other, frequency band corresponding to the resonance frequency of each of said second plurality of antennas are partially overlapped while different from each other,
The first and second frequency control units control the first and second variable impedance circuits, respectively, according to a frequency band used in the existing wireless system,
The first and second transmission / reception processing units perform first and second baseband signal processing for performing baseband transmission / reception processing corresponding to single input and single output (SISO) transmission and multiple input-multiple output (MIMO) transmission. Each part
The first and second baseband signal processing units support MIMO transmission on subcarriers with overlapping frequency bands of the first and second antennas controlled by the first and second frequency control units, respectively. A wireless communication system that performs in parallel the transmission / reception processing and the transmission / reception processing corresponding to SISO transmission on non-overlapping subcarriers. Either one of the first wireless communication device and the second wireless communication device further includes a frequency usage status acquisition unit for acquiring information on a frequency band used in an existing wireless system,
The other of said 1st radio | wireless communication apparatus and said 2nd radio | wireless communication apparatus receives the information which specifies the discrete vacant frequency band which is not used with the existing radio | wireless system via a control channel. 5. The wireless communication system according to 5.