JP2018067871A - Radio communication device and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication device that can map transmission data to a plurality of frequency bands, adjust transmission timing, and transmit data when communication is performed simultaneously at the plurality of frequency bands separated from one another.SOLUTION: A transmission device 1000 uses a plurality of radio channels on which random access control is performed at each of a plurality of frequency bands separated from one another to transmit a signal. A channel utilization state prediction unit 1070 generates prediction information by predicting a channel utilization state after the elapse of a prescribed time according to observed utilization states of the radio channels. An access control unit 1000 controls a digital signal processing unit and a high-frequency processing unit, synchronizes each partial data as packets for the plurality of frequency bands, and transmits them at the same timing by the plurality of radio channels.SELECTED DRAWING: Figure 3

Description

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

  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.

  Furthermore, LTE-A (Long Term Evolution-Advanced), which is an advanced version of LTE, has a basic unit of bandwidth supported by LTE in order to achieve higher speed transmission while ensuring backward compatibility with LTE. The carrier aggregation (CA) technology that uses a plurality of component carriers (CC) bundled at the same time is adopted, and wideband transmission of 100 MHz width can be realized using 5 CC (100 MHz width) at the maximum. However, such carrier aggregation is transmission using different channels in adjacent frequency bands.

  Although speeding up as described above has been achieved, in recent years, the demand for mobile communication traffic has increased rapidly with the spread of highly functional mobile terminals such as smartphones.

  As a result, in addition to the expansion of the use of the conventional wireless LAN (Local Area Network), the offload to the wireless LAN has progressed due to the increase in mobile data traffic due to the spread of smartphones, and the unlicensed bandwidth (2.4 GHz band, 5 GHz band) ) Traffic has increased rapidly.

  In addition, due to the progress of IoT (Internet Of Things) / M2M (Machine to Machine) society, there are concerns about further tightening of the above frequency band and 920 MHz band, and improving the frequency utilization efficiency of these frequency bands is an urgent issue. Yes.

  Here, since the usage status of radio resources varies depending on time, place, frequency band, radio channel, and the like, a situation in which only some frequency bands (or radio channels) are congested may occur.

  However, existing private wireless systems (for example, IEEE 802.11 wireless LAN) use a single frequency band or perform communication after determining one band to be used in advance. For example, IEEE802.11n is used after setting which of 2.4 GHz band and 5 GHz band is used. For this reason, there is a possibility that congestion may occur even when there is a vacant radio resource in the existing private wireless system as a whole.

  Here, cognitive radio technology is attracting attention in order to effectively use radio communication resources. The cognitive radio technology means that a wireless terminal recognizes the usage situation of surrounding radio waves and changes the radio communication resource to be used according to the situation. The cognitive radio technology includes a heterogeneous type in which different radio communication standards are selected and used according to a situation, and a frequency sharing type in which a radio terminal searches for a vacant frequency and secures a necessary communication band.

  In the heterogeneous type, the cognitive radio recognizes a plurality of radio systems operating in the vicinity, obtains information on the usage and feasible transmission quality of each system, and connects to an appropriate radio system. In other words, the heterogeneous cognitive radio indirectly increases the utilization efficiency of frequency resources by increasing the utilization efficiency of wireless systems existing in the vicinity.

  On the other hand, in the frequency sharing type, the cognitive radio has a frequency resource (this is called white space) that is not used temporarily or locally in a frequency band in which another radio system is operated. Is detected and signal transmission is performed using this. That is, the frequency sharing type cognitive radio directly increases the utilization efficiency of frequency resources in a certain frequency band.

  As a technique for solving the problem of the increase in traffic in the license-free band as described above, a plurality of wireless LAN standards (for example, 2.4 GHz band wireless LAN standard and 5 GHz band wireless LAN standard) having different usage frequency bands are used. A heterogeneous cognitive radio approach that can be selected or used in parallel can be considered (for example, Patent Document 1 and Patent Document 2).

  However, in this heterogeneous cognitive radio approach, it is necessary to divide transmission data as appropriate and assign in advance which frequency band to transmit. As a result, depending on the degree of congestion of each frequency band, problems such as transmission delays greatly differing depending on the used frequency band and the order in which data arrives at the destination are newly generated.

  Therefore, it is desirable to realize cognitive wireless communication by sharing frequencies with existing systems in a plurality of frequency bands that are largely separated from each other, for example, 2.4 GHz band wireless LAN and 5 GHz band wireless LAN.

JP 2011-111433 A JP 2013-187561 A

  However, it is not always clear what data should be distributed and how the transmission timing should be determined when communicating in parallel in a plurality of mutually separated frequency bands.

  The present invention has been made to solve the above-described problems, and its object is to transmit data to a plurality of frequency bands when communicating in a plurality of frequency bands separated from each other simultaneously. To provide a wireless communication apparatus and a wireless communication method capable of mapping and adjusting transmission timing to perform data transmission.

  According to one aspect of the present invention, there is provided a wireless communication apparatus for transmitting a signal using a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other, wherein transmission data Is divided into a plurality of partial data corresponding to each of a plurality of frequency bands, and a digital signal processing unit for generating a transmission packet for each frequency band and a digital signal corresponding to each frequency band are provided. A plurality of high-frequency signal processing units for converting to a high-frequency signal for each frequency band; a local oscillator for generating a clock signal provided in common to the plurality of high-frequency processing units and used by the plurality of high-frequency processing units; A channel usage monitoring unit that monitors the usage status of multiple radio channels in multiple frequency bands, and a channel after a predetermined period of time depending on the observed usage status. A channel usage status prediction unit that predicts the channel usage status and generates prediction information, and controls the digital signal processing unit and the high frequency processing unit based on the prediction information. And an access control unit that transmits the packets for each band synchronously at the same timing.

  Preferably, the channel use state prediction unit predicts a first required time until a busy radio channel becomes idle.

  Preferably, the channel use state prediction unit predicts a second required time until a wireless channel in an idle state becomes busy.

  Preferably, the access control unit predicts the timing when the amount of data that can be transmitted by the radio channel in the idle state is the maximum value based on the predicted first required time and second required time When the maximum value satisfies a predetermined condition, transmission data is transmitted at the timing when the maximum value is reached.

Preferably, the channel usage state prediction unit calculates an occurrence probability distribution of the duration of the idle state of the radio channel based on the observation result of the channel usage state observation unit,
The access control unit transmits the transmission data for the predetermined transmission data at a timing that minimizes the time until transmission is completed.

  Preferably, the channel usage state prediction unit predicts the occurrence probability distribution of the idle state duration as a Pareto distribution.

  Preferably, when it is determined that the idle state and the busy state are periodic, the channel usage state prediction unit predicts the occurrence probability distribution of the duration as a step function.

  Preferably, the channel usage state prediction unit predicts the duration of the busy state by decoding the frame length described in the physical header of the arriving packet and the NAV value described in the MAC frame.

  Preferably, the access control unit does not wait for the transmission timing based on the prediction result of the channel usage state prediction unit when determining that the predetermined communication quality can be achieved by performing transmission on the radio channel that has obtained the transmission opportunity. Control of immediate wireless transmission.

  Preferably, the access control unit determines a transmission rate of a radio channel used in a plurality of frequency bands and transmission power of the radio channel.

  According to another aspect of the present invention, there is provided a radio communication method for transmitting a signal using a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other, wherein transmission data Is divided into a plurality of partial data corresponding to each of a plurality of frequency bands, a transmission packet is generated for each frequency band, and a digital signal is converted into a high-frequency signal for each corresponding frequency band for each frequency band. A step of converting, a step of generating a clock signal for processing to be converted into a high-frequency signal by a local oscillator provided in common in a plurality of frequency bands, and observing use states of a plurality of radio channels in the plurality of frequency bands A step of generating prediction information by predicting a channel usage status after a lapse of a predetermined time according to the observed usage status; Based on the prediction information, a plurality of radio channels, each partial data as packets for a plurality of frequency bands, and transmitting at the same timing in synchronization.

  According to the present invention, transmission data can be mapped to a plurality of frequency bands, and data transmission can be performed by adjusting transmission timing.

It is a conceptual diagram for demonstrating the structure of the radio | wireless communications system of this Embodiment. It is a figure for demonstrating the specific example for mapping and transmitting transmission data to a several zone | band, and receiving and unifying collectively by the receiving side. It is a functional block diagram for demonstrating the structure of the transmitter 1000 of this Embodiment. It is a functional block diagram for demonstrating the example of a more detailed structure of the transmitter 1000. FIG. It is a functional block diagram for demonstrating the structure of transmission apparatus 1000 '. It is a functional block diagram for demonstrating the example of a more detailed structure of transmitter 1000 '. 10 is a timing chart for explaining operations of a channel usage status observation unit 1060, a channel usage status prediction unit 1070, and an access control unit 1080. It is a functional block diagram for demonstrating the structure of the receiver 2000 of embodiment. 3 is a functional block diagram for explaining an example of a more detailed configuration of receiving apparatus 2000. FIG. It is a functional block diagram for demonstrating the structure of receiver 2000 '. It is a functional block diagram for demonstrating the example of a more detailed structure of receiver 2000 '. 10 is a flowchart for explaining operations of a channel usage status observation unit 1060, a channel usage status prediction unit 1070, and an access control unit 1080 of the transmission apparatus 1000.

  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.

  In the following, as an example for explaining the receiving apparatus of the present invention, a plurality of existing unlicensed bands (for example, 920 MHz band used for IoT etc., 2 used for wireless LAN, which are largely separated from each other as described above). (.4 GHz band and 5 GHz band) will be described with reference to an example of a transmission apparatus in a wireless communication system capable of performing cognitive wireless communication by sharing a frequency with an existing system.

  However, the wireless communication apparatus of the present invention is not necessarily limited to such a case, and more generally, using a plurality of frequency bands separated from each other at the same time in synchronization with the same wireless method. It is possible to apply to a receiving apparatus that performs communication. In addition, as will be described later, the wireless communication device of the present invention may be applied to a receiving device that performs communication in parallel at a timing synchronized by different wireless systems using a plurality of frequency bands separated from each other. Is possible.

  FIG. 1 is a conceptual diagram for explaining the configuration of the wireless communication system of the present embodiment.

  Referring to FIG. 1, on the assumption that the transmission side uses three frequency bands of 920 MHz band, 2.4 GHz band, and 5 GHz band, a transmission frame is assumed to use one radio channel in each band. Configure.

  In addition, although it is good also as using several channels in each frequency band, below, it demonstrates as what uses one channel for every frequency band.

  In this embodiment, radio access control having the following characteristics is performed.

  That is, first, on the transmission side, the usage status (such as availability of each radio channel) of a plurality of frequency bands is observed by a method described later.

  Subsequently, the transmitting side transmits wireless packets (frames) at the same time using one or more unused frequency bands / radio channels. At this time, transmission data is mapped to a plurality of bands and transmitted.

  On the other hand, the receiving side collectively receives data from a plurality of bands and integrates the data.

  In such a transmission / reception, such a configuration can ensure a transmission opportunity even if there is a bias in the congestion situation between bands, so that it can be expected to improve frequency utilization efficiency and reduce transmission delay, and the data arrival order may be switched. There is no problem.

  FIG. 2 is a diagram for explaining a specific example for mapping transmission data to a plurality of bands and transmitting them, and collectively receiving and integrating them on the receiving side.

  As shown in FIG. 2, transmission data is divided by the number of symbols proportional to the transmission rate Ri of each band using the transmission sequence, and assigned to each band by serial / parallel conversion.

  For example, if (5 GHz band transmission rate: 2.4 GHz band transmission rate: 920 MHz band transmission rate) = (R1: R2: R3) = (3: 2: 1), the transmission data series is divided every 6 symbols, Three symbols, two symbols, and one symbol are allocated to the 5 GHz band (ch1), 2.4 GHz band (ch2), and 920 MHz band (ch3). Note that dividing and allocating a transmission sequence is not limited to such a case, and more generally, when m frequency bands are used, the ratio of frequency band transmission rates is set to (R1: R2). : ...: Rm) (assuming that the ratio is expressed as irreducible), the transmission sequence is divided into (R1 + R2 + ... + Rm) × n (m, n: natural number) symbols. R1 × n) symbols, (R2 × n) symbols,..., (Rm × n) symbols may be assigned.

  After such assignment, for each band, a physical header is attached to the transmission symbol to form a packet, and these packets are transmitted simultaneously and in parallel at the same timing.

  The number of symbols assigned to each band on the transmission side is stored as information in this physical header.

On the receiving side, synchronization and demodulation processing are performed using a physical header on each band. The demodulated sequences are combined by parallel / serial conversion in the reverse process of the transmission side, and the frame is decoded.
[Configuration of transmitter]
FIG. 3 is a functional block diagram for explaining the configuration of transmitting apparatus 1000 according to the present embodiment.

  Referring to FIG. 3, transmission apparatus 1000 includes a serial / parallel conversion (hereinafter referred to as S / P conversion) unit 1010 for performing a process of assigning a transmission sequence to each frequency band as described in FIG. For the data after P conversion, a radio frame (packet) for communication by a predetermined radio communication method such as addition of a physical header, addition of an error correction code, interleave processing, etc. is formed for each frequency band. Digital frame conversion unit 1020.1 to 1020.3 for executing digital processing and digital analog conversion processing and predetermined modulation method for digital signals from radio frame generation units 1020.1 to 1020.3, respectively To perform modulation processing (for example, orthogonal modulation processing for a predetermined multi-level modulation system), up-conversion processing, power amplification processing, etc. Including wave processing unit and the (RF unit) 1040.1 to 1040.3, and an antenna 1050.1 to 1050.3 for delivering respectively a high frequency signal RF unit 1040.1 to 1040.3. The operations of the RF units 1040.1 to 1040.3 are controlled based on a clock from a local oscillator 1030 provided in common to these units.

  Furthermore, the transmission apparatus 1000 includes a channel usage status monitoring unit 1060 that monitors usage statuses (such as availability of each radio channel) of each frequency band (one or more radio channels in each frequency band), and a channel usage status. Based on the observation of the observation unit 1060, the channel usage status prediction unit 1070 that predicts the channel usage status at a predetermined timing, the processing timing of the radio frame generation units 1020.1 to 1020.3, and the transmission timing of the RF unit And an access control unit 1080 that controls to simultaneously transmit wireless packets in unused frequency bands and wireless channels for a predetermined period at the same controlled transmission timing.

  As described with reference to FIG. 1, the transmission apparatus 1000 configured as described above maps and transmits data to a plurality of bands, and the receiving side collectively receives the plurality of bands and integrates the data.

  FIG. 4 is a functional block diagram for explaining an example of a more detailed configuration of the transmission apparatus 1000.

  The functional block diagram shown in FIG. 4 shows, as an example, the configuration of a transmission device that conforms to a wireless communication scheme similar to the wireless communication standard 802.11a.

  That is, although the wireless communication standard 802.11a is a wireless LAN communication system of 5 GHz band, in FIG. 4, only the frequency band is different in the 2.4 GHz and 920 MHz bands. It shall be assumed that a receiver conforming to is used.

  Therefore, in each frequency band, the configuration of the preamble portion of the packet is common to a plurality of frequency bands.

  However, it is not always necessary that the wireless communication system of each frequency band has the same configuration, even if the wireless communication system (signal format, symbol length, subcarrier interval, etc.) differs for each frequency band. Good. In this case, at least a single transmission sequence is divided into each band and transmitted at the same time, and the configuration of the RF section is basically the same except that the frequency bands are different, and the configuration of the preamble portion of the packet (Preamble length, etc.) may be different for each of a plurality of frequency bands.

  FIG. 4 exemplarily shows a configuration related to transmission in the 5 GHz band. Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, a signal to be transmitted is subjected to OFDM (Orthogonal Frequency Division Multiplexing) modulation.

  Referring to FIG. 4, radio frame generation section 1020.3 receives transmission data distributed from S / P conversion section 1010, and performs error correction coding for error correction coding section 1110 and error correction code. An interleaving / mapping unit 1120 for executing interleaving processing and mapping processing on the output of the converting unit 1110, an IFFT unit 1130 for executing inverse Fourier transform processing, and a GI adding unit for adding a guard interval part 1140 and a digital-to-analog converter (DAC) 1150 for converting the digital signal into analog signals of I component and Q component.

  The high frequency processing unit 1040.3 includes a quadrature modulator 1210 for modulating a signal from the DAC 1150 into a predetermined multilevel modulation signal, an upconverter 1220 for upconverting the output of the quadrature modulator 1210, and an output of the upconverter 1220. And a power amplifier 1230 for amplifying and transmitting the signal from the antenna 1050.3.

  As a result, the baseband OFDM signal is converted into a carrier band OFDM signal by the RF unit 1040.3.

  Further, the high frequency processing unit 1040.3 is based on a clock frequency conversion unit 1310 for converting a reference frequency signal from the local oscillator 1030 into a reference clock signal in a corresponding frequency band, and a reference clock from the clock frequency conversion unit 1310. Based on the reference clock from the clock frequency conversion unit 1310 and the clock generation unit 1320 that generates the clock used for the modulation processing in the quadrature demodulator 1210, the clock used for the up-conversion processing in the up-converter 1220 is generated. Clock generation unit 1340.

That is, the reference frequency signal from the local oscillator 1030 is used as a clock signal in the conversion from the baseband OFDM signal to the carrier band OFDM signal. More generally, even when the wireless communication systems are different, the reference frequency signal from the local oscillator 1030 is basically used as a clock signal in the conversion from the baseband signal to the carrier band signal.
[Other configuration of transmitting device]
3 and 4, an example of the configuration of the transmission apparatus 1000 has been described.

  3 and 4, the transmission data is distributed to each frequency band by the S / P converter 1010, and then the error correction coding process and the interleave process are performed.

  However, the configuration of the transmission apparatus 1000 is not limited to such a case.

  FIG. 5 is a functional block diagram for explaining the configuration of the transmitting apparatus 1000 ′ having such another configuration.

  The transmission apparatus 1000 ′ in FIG. 5 has a configuration in which transmission data is subjected to error correction coding processing and interleaving processing and then distributed to each frequency band by the S / P conversion unit 1010. The radio frame generation units 1020.1 to 1020.3 perform mapping processing, IFFT processing, addition of guard intervals, and digital / analog conversion processing.

  FIG. 6 is a functional block diagram for explaining an example of a more detailed configuration of such a transmission apparatus 1000 ′. The configuration in FIG. 6 corresponds to the configuration in FIG.

  The functional block diagram shown in FIG. 6 also shows the configuration of a transmission apparatus according to the same wireless communication scheme as the wireless communication standard 802.11a as an example.

  As shown in FIG. 6, after error correction coding processing by the error correction coding processing unit 1110 and interleaving processing by the interleaving unit 1112, the S / P conversion unit 1010 distributes the frequency bands to each frequency band. The frequency diversity effect can be obtained more powerfully.

  FIG. 7 is a timing chart for explaining operations of the channel usage status monitoring unit 1060, the channel usage status prediction unit 1070, and the access control unit 1080.

  Referring to FIG. 7, channel usage status monitoring section 1060 monitors the usage status of each frequency band (for example, the availability status and busy probability of each radio channel), and channel usage status prediction section 1070 The most recent usage situation is predicted, and from the result, the access control unit 1080 determines transmission parameters such as a transmission timing, a used frequency band and a radio channel so that good communication can be performed.

  That is, as will be described in detail later, for example, when performing communication using three frequency bands, the channel usage state prediction unit 1070 uses two bands at the time t2, for example, based on the current time. If it is time t3, it is predicted that three bands can be used. In order to perform efficient transmission, the access control unit 1080 determines the transmission start timing and the used frequency band based on the use state prediction result.

  For example, in conventional random access control in a wireless LAN or the like, transmission is performed immediately when a transmission opportunity is obtained by CSMA / CA and random backoff described later.

On the other hand, the access control unit 1080 according to the present embodiment waits for transmission until a plurality of frequency bands / wireless channels can be used simultaneously even if a transmission opportunity is obtained on some of the wireless channels as necessary. Control is performed.
[Receiver configuration]
Below, the structure of the receiver used in the radio | wireless communications system which was demonstrated in FIG. 1 is demonstrated.

  FIG. 8 is a functional block diagram for explaining the configuration of receiving apparatus 2000 of the embodiment.

  Referring to FIG. 8, receiving apparatus 2000 includes antennas 201. 1 to 200.3 and antennas 201. 1 for receiving signals in a plurality of frequency bands (920 MHz band, 2.4 GHz band, and 5 GHz band), respectively. Common to the receiving units 2100.1 to 2100.3 and the receiving units 2100.1 to 2100.3 for executing reception processing such as down-conversion processing, demodulation / decoding processing, etc. A local oscillator 2020 that generates a reference frequency signal that is a clock serving as a reference for the operation of the receiving units 2100.1 to 2100.3, and each sequence of signals from the receiving units 2100.1 to 2100.3 as a transmitting side. In the reverse process, a parallel / serial conversion unit 2700 for coupling by parallel / serial conversion is included. The output of the integrated frame from the parallel / serial (P / S) conversion unit 2700 is passed to the upper layer.

  The receiving device 2000 detects the frequency offset of the local oscillator 2020 from the received preamble signal, generates a signal (oscillation frequency control signal) for controlling the oscillation frequency of the local oscillator 2020, and performs carrier frequency synchronization processing. And a synchronization processing unit 2600 that generates a signal (synchronization timing signal) for timing synchronization in digital signal processing from the received signal.

  Receiving section 2100.1 receives the signal from antenna 2010.1, and performs low-noise amplification processing, down-conversion processing, demodulation processing for a predetermined modulation scheme (for example, orthogonal demodulation processing for a predetermined multilevel modulation scheme), analog A high-frequency processing unit (RF unit) 2400.1 for executing digital conversion processing and the like, and a baseband for executing baseband processing such as demodulation / decoding processing on the digital signal from the RF unit 2400.1 A processing unit 2500.1 is included.

  The receiving unit 2100.2 also includes a high frequency processing unit (RF unit) 2400.2 and a baseband processing unit 2500.2 for performing similar processing for the corresponding frequency band. The receiving unit 2100.3 also includes a high frequency processing unit (RF unit) 2400.3 and a baseband processing unit 2500.3 for performing similar processing for the corresponding frequency band.

  The baseband processing units 2500.1 to 2500.3 and the parallel / serial (P / S) conversion unit 2700 are collectively referred to as a digital signal processing unit 2800.

  FIG. 9 is a functional block diagram for explaining an example of a more detailed configuration of receiving apparatus 2000 shown in FIG.

  The functional block diagram shown in FIG. 9 also shows, as an example, the configuration of a receiving device that conforms to a wireless communication scheme similar to the wireless communication standard 802.11a.

  Therefore, the configuration of the receiving apparatus corresponds to the configuration of the transmitting apparatus shown in FIG.

  FIG. 9 also exemplarily shows the configuration of the reception unit 2100.3 in the 5 GHz band.

  Referring to FIG. 9, RF section 2400.3 of receiving section 2100.3 performs low-frequency amplifier 3010 for amplifying the received signal from antenna 2010.3 and frequency conversion of the output of low-noise amplifier 3010. Down converter 3020, automatic gain controller 3030 for controlling the output of down converter 3020 to have a predetermined amplitude, quadrature demodulator 3040 for demodulating a predetermined multilevel modulation signal, and quadrature demodulator And an analog-digital converter (ADC) 3050 for converting the I component output and the Q component output of 3040 into digital signals.

  The RF unit 2400.3 is further based on a clock frequency conversion unit 3060 for converting the reference frequency signal from the local oscillator 2020 into a reference clock signal in a corresponding frequency band, and a reference clock from the clock frequency conversion unit 3060. Based on the reference clock from the clock frequency conversion unit 3060 and the clock generation unit 3070 for generating the clock used for the down-conversion processing in the down converter 3020, the clock used for the demodulation processing in the quadrature demodulator 3040 is generated. A clock generation unit 3080.

  Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, the transmitted signal is subjected to OFDM (Orthogonal Frequency Division Multiplexing) modulation. As a result, the RF band 2400.3 converts the carrier band OFDM signal into a baseband OFDM signal.

  The reference frequency signal from the local oscillator 2020 is used for carrier frequency synchronization in the conversion from the carrier band OFDM signal to the baseband OFDM signal. More generally, even when the wireless communication systems are different, the reference frequency signal from the local oscillator 2020 is basically used for carrier frequency synchronization in conversion from a carrier band signal to a baseband signal.

  Referring back to FIG. 9 again, the baseband processing unit 2500.3 receives the signal from the ADC 3050, and with respect to the GI removal unit 4010 for removing the guard interval part and the signal from which the guard interval has been removed, An FFT unit 4020 for executing fast Fourier transform, a demapping / deinterleaving unit 4030 for executing demapping and deinterleaving processing on the output of the FFT unit 4020, and an error correction unit 4040 are included.

  Here, the synchronization timing signal output from the synchronization processing unit 2600 is used for symbol timing synchronization for detecting the start of an OFDM symbol.

More generally, the synchronization timing signal output from the synchronization processing unit 2600 is basically used as the synchronization signal in the baseband processing even when the wireless communication systems are different.
[Other configuration of receiving apparatus]
8 and 9, an example of the configuration of the receiving device 2000 has been described.

  In the configurations of FIGS. 8 and 9, corresponding to the configuration of the transmitting side of FIGS. 3 and 4, the demapping / interleave processing and error correction processing are performed on the received data, and then the P / S conversion unit 2700 is performed. Thus, the signal from each frequency band is combined.

  However, the configuration of receiving apparatus 2000 is not limited to such a case.

  FIG. 10 is a functional block diagram for explaining the configuration of the receiving apparatus 2000 ′ having such another configuration.

  The receiving apparatus 2000 ′ in FIG. 10 is configured to perform deinterleaving processing and error correction processing on the received data after combining the signals of each frequency band by the P / S conversion unit 2700. Baseband processing units 2500.1 to 2500.3 perform guard interval removal, FFT processing, and demapping processing.

  Accordingly, the receiving device 2000 ′ in FIG. 10 corresponds to reception of a signal from the transmitting device 1000 ′ in FIG.

  FIG. 11 is a functional block diagram for explaining an example of a more detailed configuration of such a receiving apparatus 2000 ′. The configuration in FIG. 11 corresponds to the configuration in FIG.

  The functional block diagram shown in FIG. 11 also shows a configuration of a transmission device according to a wireless communication scheme similar to the wireless communication standard 802.11a as an example.

  As shown in FIG. 11, for each frequency band, after the guard interval removal by the guard interval removal unit 4010, the FFT processing by the FFT unit 4020, and the demapping processing by the demapping unit 4032, the P / S conversion unit 2700 Combine the band signals. After combining by the P / S conversion unit 2700, deinterleaving processing by the deinterleaving unit 4042 and error correction processing by the error correction unit 4040 are executed.

  FIG. 12 is a flowchart for explaining the operations of the channel usage status observation unit 1060, the channel usage status prediction unit 1070, and the access control unit 1080 of the transmission device 1000 described in FIG. 3 or the transmission device 1000 ′ described in FIG. is there.

  Referring to FIG. 12, first, the channel usage status observation unit 1060 performs carrier sense in a plurality of bands, and updates usage status information stored in a storage device (not shown) (S100).

  That is, the channel usage state monitoring unit 1060 measures the busy / idle state of each radio channel scheduled to be used in a plurality of frequency bands, and measures the durations thereof.

  Here, items to be observed and measured by the channel use state observation unit 1060 include the following.

i) State of each radio channel (busy or idle state: this is a physical carrier sense result)
ii) Busy duration of each radio channel iii) Frame length described in the physical header of the frame being received iv) NAV value (virtual carrier sense result) described in the MAC header of the frame being received )
Here, NAV is a Network Allocation Vector (transmission prohibited period).

  Hereinafter, a general method for avoiding transmission collision from each terminal in a wireless LAN will be briefly described for explanation of terms.

  A wireless LAN channel employs a method called “CSMA (Carrier Sense Multiple Access)” because packets cannot collide and efficient communication cannot be established unless they wait for transmission from each other.

  In the case of wireless, it is not known whether or not a collision will occur just by monitoring the intensity of radio waves. This is because radio waves are greatly attenuated depending on the distance, so that there is a possibility that the radio waves cannot be detected if the opponent causing the collision is far away.

  Therefore, a “waiting time (DIFS: Distributed access Inter Frame Space)” is always provided before transmission, and transmission is performed after confirming that there is no other transmission signal. Such a method is called “CA (Collision Avoidance)”.

  And after transmission, it always waits for "ACK (ACKnowledgement, arrival confirmation response)", and when ACK does not return, it judges that a collision etc. have occurred and retransmits.

  In addition to this, there is “RTS / CTS (Request to Send / Clear to Send)” devised for countermeasures against hidden terminals, for example, as a wireless LAN-specific access control mechanism. Here, the hidden terminal is a terminal that is out of the radio range from itself but is in the radio range of the communication partner. Although it cannot be known directly, it causes interference.

  Assuming that the reach of radio waves is Lm, consider a situation in which the communication partner B (access point) of the wireless terminal A is Lm ahead, and another wireless terminal C is further Lm ahead.

  At this time, since the radio wave of the terminal C does not reach the terminal A, the terminal C does not know the existence of the terminal C even if the terminal A checks whether another terminal is transmitting a signal (even if carrier sense is performed). It becomes a hidden terminal of terminal A. If no measures are taken, even if terminal C is transmitting to access point B, terminal A will also transmit data to access point B. This causes a collision at the access point B and causes a reduction in throughput.

  RTS / CTS is a mechanism in which all wireless devices send out an “RTS (transmission request)” packet before transmission and respond with “CTS (receivable)” if the receiving side can also receive the packet. In the above example, terminal C first transmits RTS to access point B. However, this RTS does not reach the terminal A.

  The access point B notifies the terminal C that it can be received by transmitting a CTS. Since this CTS also reaches the terminal A, the terminal A senses that communication will be performed, and postpones transmission. In the RTS / CTS packet, the channel occupation period is written, and communication is suspended during that time. This period is called “NAV (Network Allocation Vector)”.

  The usage status statistics of each radio channel calculated and predicted by the channel usage status prediction unit 1070 based on the observation / measurement results by the channel usage status observation unit 1060 include the following.

a) Probability of becoming busy (time utilization rate)
b) Probability distribution of duration between busy and idle states c) Duration of idle / busy state duration relative to previous busy / idle state duration Occurrence probability distribution (for example, probability density function (PDF) or cumulative distribution function (CDF))
d) Occurrence pattern of busy state and idle state (period and duty ratio: when background traffic is periodic)
Below, the specific example of the prediction information which the channel utilization condition prediction part 1070 calculates among the above is demonstrated.

1) Method of calculating “idle state duration occurrence probability distribution” The probability density function (PDF) p (τ) of the frame arrival interval τ of the wireless LAN is a Pareto represented by the following equation (1): It is known that it generally follows the (Pareto) distribution (see Document 1 below).

  Reference 1: Dashdorj Yamkhin and Youjip Won, “Modeling and analysis of wireless LAN traffic,” Journal of Information Science and Engineering, vol. 25, no. 6, pp. 1783-1801, Nov. 2009.

Here, a is a coefficient for determining the distribution shape, and τ _m is the minimum frame arrival interval.

When a and τ _m are given, the average μ and the variance σ ² of τ are given by the following equations (2) and (3).

For example, in the case of the IEEE 802.11 DCF standard, since the minimum arrival interval of the data frame is the above-described DIFS, τ _m = DIFS is set. If the duration of the idle state is the frame arrival interval and μ and σ ² are measured from the carrier sense result, the channel usage state prediction unit 1070 can estimate the value of a using the above formula.

  If the value of a is obtained, the channel usage state prediction unit 1070 obtains an occurrence probability distribution represented by the following equation as a probability C (τ) that the idle state continues for τ time or longer.

When a radio channel scheduled to be used is in an idle state, the probability that the idle state continues from that point until t can be obtained from C (τ).

  2) As a result of the carrier sense, when the idle duration and the busy duration are almost the same each time, and the channel usage state prediction unit 1070 determines that the traffic is periodic, the idle ( As an occurrence probability distribution of the duration of the idle state, for example, idle (idle) from the start of the idle state to the average value of the idle state duration (which may be a median or minimum value) ) It may be a step function in which the continuation probability is 100% and thereafter is 0%.

  3) On the other hand, when the wireless channel to be used is busy, the frame length described in the physical header of the incoming packet (frame) and the NAV value described in the MAC frame are decoded. Thus, the channel usage state prediction unit 1070 can obtain the busy state duration and predict the busy state duration.

  Returning to FIG. 8 again, the access control unit 1080 determines whether there is data to be transmitted (S102). If there is no data to be transmitted yet (N in S102), the process returns to S100.

  On the other hand, if there is data to be transmitted (Y in S102), the access control unit 1080 first determines whether the “immediate transmission condition” as described below is satisfied for the wireless channel from which the transmission opportunity is obtained. .

  That is, originally, the access control unit 1080 determines whether or not the transmission timing has arrived based on the prediction result of the channel usage state prediction unit 1070, but in reality it is in a busy / idle state. For example, if it is determined that a combination of the following conditions is satisfied for a radio channel for which a transmission opportunity has been ensured, an error may occur in the prediction of the occurrence of a transmission opportunity and an expected transmission opportunity may not be obtained. Then, control is started to start transmission immediately (S104). That is, in this case, if the access control unit 1080 determines that the predetermined communication quality can be achieved by performing transmission using the radio channel that has obtained the transmission opportunity, the access control unit 1080 immediately does not wait for the transmission timing based on the prediction result. To perform wireless transmission.

a1) The total transmission rate is greater than or equal to a predetermined value a2) When transmission is started immediately, the transmission delay of transmission data is less than a predetermined value a3) When transmission is started immediately, the throughput increases by a predetermined amount or more a4) A transmission opportunity is secured When transmission is performed on a wireless channel, the variance and / or average of the usage rate between the wireless channels is reduced. A5) When transmission is performed on a wireless channel where a transmission opportunity is secured, the energy consumption required for transmission is less than a predetermined amount. A6) A transmission opportunity is obtained on a predetermined radio channel a7) When loss of transmission opportunity is not allowed Any one of the above conditions a1) to a7) is satisfied, or conditions a1) to a7 ) Is established (a combination of two or more conditions), the access control unit 1080 immediately transmits using a radio channel for which a transmission opportunity is secured. Start. That is, the access control unit 1080 performs transmission parameter determination and transmission data mapping (S108), and controls the S / P conversion unit 1010 and the radio frame generation units 1020.1 to 1020.3 to select the selected frequency. The frame is transmitted on the band and the wireless channel (S110), and the process returns to step S100.

  Here, “transmission parameters” include “band used and radio channel used”, “transmission rate used in each radio channel”, “transmission power of each radio channel (or each subcarrier in the case of OFDM)”, etc. There is.

  If predetermined conditions are satisfied, it may be possible to perform transmission using only a part of radio channels instead of radio channels in all usable frequency bands.

  For determining the transmission rate and the transmission power, an existing method as described in Document 2 shown below can be used.

Reference 2: Tomoaki Yoshinori, Seiichi Sampei, Norihiko Morinaga, “OFDM adaptive modulation using multi-level transmission power control for high-speed data transmission,” IEICE Transactions (B), J84-B, 7 1141-1150, July 2001 The propagation path information necessary for determining the transmission rate and transmission power can be obtained by the following method, for example.

  -Use the propagation path estimation result performed when receiving a frame received in reverse communication.

  -Use the channel feedback method defined by IEEE 802.11 wireless LAN.

Subsequently, when the “immediate transmission condition” is not satisfied (N in S104), the access control unit 1080 determines whether or not the transmission timing has arrived based on the prediction result of the channel usage state prediction unit 1070 as described above. Determine (S106)
For the determination of the transmission start timing, prediction information based on usage status information is used as follows.

b1) Prediction of time required for a wireless channel in a busy state to enter an idle state (prediction of “how long should I wait?”)
For this, the following information can be used to predict “how long should I wait?”.

b1-1) Length of frame or NAV that is busy (if already known)
b1-2) Presence / absence of busy state of each radio channel after an arbitrary time (For periodic background traffic, from busy state and idle state period and duty) Predictable)
b1-3) Idle occurrence probability with respect to future waiting time based on the busy duration so far (calculated from CDF in busy and idle states)
b2) Prediction of the time required for an idle radio channel to become busy (Prediction of "How long can I wait?")
b2-1) Presence / absence of busy state of each radio channel after an arbitrary time (If it is periodic background traffic, it can be predicted from the period and duty of busy state and idle state)
b2-2) Busy occurrence probability with respect to future waiting time based on past idle duration (calculated from busy and idle CDFs)
The access control unit 1080, as described above, “prediction of the time required for a radio channel in a busy state to become an idle state” and “an idle radio channel is busy. By combining with the “prediction of required time to become”, the transmission timing “maximum expected value of transmission rate” is calculated.

  That is, the access control unit 1080 combines the above two predictions so that the transmission rate of each radio channel has a predetermined value, and the idle state at each time timing within a predetermined time range from the present time. The maximum value of the amount of data that can be transmitted through the wireless channel can be predicted. When such predicted data amount (transmission rate) that can be transmitted exceeds a value corresponding to a predetermined transmission rate, data is transmitted at the transmission timing.

  That is, if the access control unit 1080 determines that such transmission timing has arrived (Y in S106), the access control unit 1080 determines transmission parameters and maps transmission data (S108), and performs S / P conversion. The unit 1010 and the radio frame generation units 1020.1 to 1020.3 are controlled to transmit a frame using the selected frequency band and radio channel (S110), and the process returns to step S100.

  When the access control unit 1080 determines in step S106 that the predicted transmittable data amount (transmission rate) does not exceed the value corresponding to the predetermined transmission rate, the access control unit 1080 waits for transmission to increase the current amount. Assuming that there is a possibility that a transmission opportunity may be obtained by the number of wireless channels, the transmission waits (N in step S106), and the process returns to step S100. This is because such a standby operation is considered to achieve improvement in frequency utilization efficiency, reduction in transmission delay, and the like.

  Note that the access control unit 1080 may adopt the following as a reference for determining whether or not the transmission timing has arrived.

c1) Minimize the time until transmission of transmission data is completed (since transmission can be completed early, many frames can be transmitted and less resources are wasted)
c2) Minimize the amount of free resources generated until the completion of transmission c3) Maximize the amount of data that can be transmitted within a predetermined time c4) Minimize the variance and average of the usage rate of each radio channel (Effective use of radio resources) While eliminating extremely crowded channels.)
c5) Minimize the required transmission energy under the condition that transmission of transmission data is completed within a certain period of time c6) The probability of transmission outage (transmission failure / transmission opportunity loss) is below a predetermined value c7) Use of a specific radio channel by itself Rate is less than the specified value (In order to keep the time utilization rate of the frequency band within the limit in a frequency band with a transmission time limit such as the 920 MHz band.)
Here, as a specific example, c1) a method for minimizing the time until transmission data transmission is completed will be further described.

  For example, radio channels ch1, ch2, and ch3 are assumed as radio channels scheduled to be used, and the usable transmission rates there are R1, R2, and R3 [b / s]. Also, let the estimated idle duration probability of radio channel i be Ci (τ). The amount of data to be transmitted from now on is assumed to be I [b / s].

  i) When a transmission opportunity is obtained in a certain radio channel (ch1 is assumed), the following is calculated.

    i-1) The time required to transmit data using only channel ch1 is as follows.

i-2) Next, a wireless channel from which a transmission opportunity is obtained is assumed to be ch2, and a time τ ₂ (for example, busy duration + DIFS) necessary to obtain the transmission opportunity is calculated there.

i-3) The expected probability that ch1 can be used after waiting for τ ₂ is C ₁ (τ ₂ ). Therefore, when channel ch2 is to be used, it is simultaneously used with channel ch1 with the probability of C ₁ (τ ₂ ). it can. When transmission is started after τ _2, the expected value T ₂ of the time until data transmission ends is as follows.

i-4) Similarly, assuming that the time until the channel ch3 becomes available is τ ₃ , when transmission is started after τ ₃ , the expected value T ₃ of the time until data transmission ends is as follows: Become.

Based on the above calculation, the times T ₁ , T ₂ , and T ₃ are compared. If the time T ₂ is the minimum, the transmission is performed after τ ₂ waiting, and if the time T ₃ is the minimum, the transmission is performed after τ ₃ waiting. Otherwise, it is transmitted when a transmission opportunity of channel ch1 is obtained.

  With the configuration as described above, each transmission data can be mapped to a plurality of frequency bands, and data transmission can be performed by adjusting the transmission timing.

  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.

  1000 Transmitter, 1010 S / P converter, 1020.1 to 1020.3 Radio frame generator, 1030 Local oscillator, 1040.1 to 1040.3 RF unit, 1050.1 to 1050.3 Antenna, 1060 channel usage status Observation unit, 1070 channel utilization status prediction unit, 1080 access control unit, 2000 receiver, 2011-2010.3 antenna, 2020 local oscillator, 2100.1-2100.3 receiver, 2400.1-2400.3 RF Part, 2500.1-2500.3 baseband processing part, 2700 P / S conversion part, 2600 synchronization processing part, 2800 digital signal processing part.

According to one aspect of the present invention, there is provided a wireless communication apparatus for transmitting a signal using a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other, wherein transmission data Is divided into a plurality of partial data corresponding to each of a plurality of frequency bands, a digital signal processing unit for generating a transmission packet for each frequency band, and a digital signal of the transmission packet provided for each frequency band and a plurality of high-frequency Namisho processing section for converting high-frequency signals for each corresponding frequency band is provided in common to a plurality of high frequency processing unit, for generating a clock signal used by a plurality of high frequency processing unit Local oscillator, a channel usage monitoring unit that monitors the usage status of multiple radio channels in multiple frequency bands, and a predetermined time depending on the observed usage status A channel usage status prediction unit that predicts the channel usage status after generation and generates prediction information, and controls the digital signal processing unit and the high frequency processing unit based on the prediction information. And an access control unit that transmits the packets in a plurality of frequency bands synchronously at the same timing.

Preferably, the channel usage prediction unit, an idle state and the busy state if it is determined that the periodic, predict the occurrence probability distribution of duration as a step function.

According to another aspect of the present invention, there is provided a radio communication method for transmitting a signal using a plurality of radio channels performing random access control in each of a plurality of frequency bands separated from each other, wherein transmission data Is divided into a plurality of partial data corresponding to each of a plurality of frequency bands, a transmission packet is generated for each frequency band, and a digital signal of the transmission packet is generated for each frequency band for each frequency band. A step of converting to a high-frequency signal; a step of generating a clock signal for processing to be converted to a high-frequency signal by a local oscillator provided in common in a plurality of frequency bands; and a use situation of a plurality of radio channels in the plurality of frequency bands And generate prediction information by predicting the channel usage status after a lapse of a predetermined time according to the observed usage status A step that, based on the prediction information, a plurality of radio channels, each partial data as packets for a plurality of frequency bands, and transmitting at the same timing in synchronization. ?

Claims (11)

A wireless communication device for transmitting a signal using a plurality of wireless channels performing random access control in each of a plurality of frequency bands separated from each other,
A digital signal processing unit for dividing transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands, and generating a transmission packet for each of the frequency bands;
A plurality of high-frequency signal processing units provided for each of the frequency bands, for converting the digital signal into a corresponding high-frequency signal for each frequency band;
A local oscillator for generating a clock signal provided in common to the plurality of high frequency processing units and used in the plurality of high frequency processing units;
A channel usage monitoring unit that monitors usage of the plurality of radio channels in the plurality of frequency bands;
According to the observed usage status, a channel usage status prediction unit that predicts the channel usage status after a predetermined time and generates prediction information;
Based on the prediction information, the digital signal processing unit and the high-frequency processing unit are controlled, and the partial data is synchronized with the plurality of radio channels as packets for the plurality of frequency bands at the same timing. A wireless communication device comprising: an access control unit for transmission.   The wireless communication apparatus according to claim 1, wherein the channel usage state prediction unit predicts a first required time until a busy wireless channel becomes idle.   The wireless communication apparatus according to claim 2, wherein the channel usage state prediction unit predicts a second required time until a wireless channel in an idle state becomes busy.   The access control unit predicts and predicts a timing at which the amount of data that can be transmitted through the idle radio channel is maximum based on the predicted first required time and the second required time. 4. The wireless communication apparatus according to claim 3, wherein when the maximum value satisfies a predetermined condition, transmission data is transmitted at a timing at which the maximum value is reached. The channel usage status prediction unit calculates an occurrence probability distribution of the duration of the idle state of the radio channel based on the observation result of the channel usage status monitoring unit,
The wireless communication apparatus according to claim 1, wherein the access control unit transmits the transmission data for the predetermined transmission data at a timing that minimizes a time until transmission is completed.   The radio communication apparatus according to claim 5, wherein the channel usage state prediction unit predicts the occurrence probability distribution of the duration of the idle state as a Pareto distribution.   The wireless communication apparatus according to claim 5, wherein the channel usage state prediction unit predicts an occurrence probability distribution of a duration as a step function when determining that the idle state and the busy state are periodic.   The channel usage state prediction unit predicts a busy state duration by decoding a frame length described in a physical header of an incoming packet and a NAV value described in a MAC frame. 2. The wireless communication device according to 2.   If the access control unit determines that a predetermined communication quality can be achieved by performing transmission on the radio channel from which a transmission opportunity has been obtained, the access control unit does not wait for a transmission timing based on a prediction result of the channel usage state prediction unit. The wireless communication apparatus according to claim 1, wherein immediate wireless transmission control is performed.   The radio communication apparatus according to claim 1, wherein the access control unit determines a transmission rate of a radio channel to be used in the plurality of frequency bands and transmission power of the radio channel. A wireless communication method for transmitting a signal using a plurality of wireless channels performing random access control in each of a plurality of frequency bands separated from each other,
Dividing transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands, and generating a transmission packet for each of the frequency bands;
For each frequency band, converting the digital signal into a corresponding high frequency signal for each frequency band;
Generating a clock signal for processing to be converted into the high-frequency signal by a local oscillator provided in common in the plurality of frequency bands;
Observing usage of the plurality of radio channels in the plurality of frequency bands;
In accordance with the observed usage status, predicting the channel usage status after a predetermined time, and generating prediction information;
And a step of transmitting each partial data as a packet for each of the plurality of frequency bands synchronously and at the same timing based on the prediction information using the plurality of wireless channels.