JP2009290602A - Wireless communication system and base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system that prevents deterioration in communication quality due to multipath. <P>SOLUTION: The wireless communication system includes a first communication device comprising a signal power detecting means for detecting a basic wave power and a noise power of received signals by Fourier transform processing, a multipath determining means for determining a magnitude of the multipath effect based on the basic wave power and noise power, a communication switching instruction transmitting means for transmitting a multicarrier communication switching instruction or a single carrier communication switching instruction based on the determination results by the multipath determining means, a first communication switching means for switching communication with a second communication device to a multicarrier communication or a single carrier communication based on the switching instruction, and a second communication device comprising a second communication switching means which switches the communication to the multicarrier communication when the multicarrier communication switching instruction is received and which switches the communication to the single carrier communication when the single carrier communication switching instruction is received. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication system and a base station.

  2. Description of the Related Art Conventionally, in a wireless communication system having a portable terminal such as a mobile phone, a CDMA (Code Division Multiple Access) method, a TDMA (Time Division Multiple Access) method, or an FDMA (Frequency Division Multiple Access): Single carrier communication in which communication between a mobile terminal and a base station is performed by one carrier using a frequency division multiple access) or the like as a multiple access method. However, in recent years, multi-carrier communication such as OFDMA (Orthogonal Frequency Division Multiple Access) is attracting attention as a next-generation broadband wireless communication system.

And as what can change this single carrier communication and multicarrier communication dynamically, the following patent document 1 is disclosing the transmitter, the receiver, the mobile communication system, and the transmission control method. The transmission apparatus in Patent Document 1 described below performs switching means for switching to either a single-carrier communication or multi-carrier communication radio access method, and either fast Fourier transform or serial-parallel conversion according to the switched radio access method. Frequency domain signal generation means for generating frequency domain signals by allocating radio resources to the spread spread chip sequence, and transmission signals by performing fast inverse Fourier transform on the frequency domain signals Transmission signal generating means. In addition, the receiving device includes a wireless access method determining unit that determines a wireless access method used by the transmitting device according to a distance between the receiving device and the transmitting device or transmission power in the transmitting device.
JP 2007-151059 A

  By the way, the prior art is switched to either single carrier communication or multi-multicarrier communication according to the distance between the receiving device and the transmitting device or the transmission power in the transmitting device. However, single carrier communication has an advantage that power consumption can be suppressed, but has a problem that it is more susceptible to multipath than multicarrier communication and easily deteriorates communication quality. For this reason, when switching to single carrier communication or multicarrier communication without considering multipath as in the above prior art, communication quality may be deteriorated.

  The present invention has been made in view of the above-described circumstances, and provides a device capable of suppressing deterioration in communication quality due to multipath by dynamically switching to either multicarrier communication or single carrier communication in wireless communication. The purpose is to do.

  In order to achieve the above object, according to the present invention, as a first solving means related to a wireless communication system, a wireless communication system having a first communication device and a second communication device for transmitting and receiving signals, Signal power detection means for detecting fundamental wave power and noise power of the received signal by conversion processing; multipath determination means for judging the magnitude of multipath influence based on the fundamental wave power and noise power; and the multipath A communication switching instruction transmitting means for transmitting a multicarrier communication switching instruction that is a switching instruction to multicarrier communication or a single carrier communication switching instruction that is a switching instruction to single carrier communication based on a determination result of the determining means; Switching communication with the second communication device to multicarrier communication or single carrier communication based on the instruction When receiving the multi-carrier communication switching instruction and the first communication apparatus comprising one communication switching means, the communication with the first communication apparatus is switched to multi-carrier communication, and the single-carrier communication switching instruction is received. Then, a means of having the second communication device provided with the second communication switching means for switching the communication with the first communication device to the single carrier communication is adopted.

  In the present invention, as the second solving means relating to the wireless communication system, in the first solving means, the communication switching instruction transmitting means is configured such that the determination result of the multipath determining means is greater than a predetermined reference. A means of instructing switching to multi-carrier communication and instructing switching to single-carrier communication is adopted when the switching is smaller than a predetermined reference.

  In the present invention, as a third solving means relating to the radio communication system, in the first or second solving means, the signal power detection means is the fundamental wave power of the first signal obtained by removing the guard interval from the received signal. The multipath determination means employs a means for determining the magnitude of the influence of the multipath based on the fundamental wave power and noise power of the first signal.

  In the present invention, as a fourth solving means relating to a radio communication system, in the first or second solving means, the signal power detection means is configured to perform fundamental transform power and noise power of a guard interval of a received signal by Fourier transform processing. The multipath determination means employs means for determining the magnitude of the influence of the multipath based on the fundamental wave power and noise power of the guard interval.

  In the present invention, as a fifth solving means relating to the wireless communication system, in the third solving means, the signal power detecting means detects the fundamental wave power and noise power of the first signal and also receives the received signal. Detecting the fundamental wave power and noise power of the second signal without removing the guard interval from the multipath determination means, wherein the multipath determining means detects the fundamental wave power and noise power of the first signal and the fundamental wave of the second signal. A means is adopted in which the magnitude of the influence of the multipath is determined by comparing the power and the noise power.

  In the present invention, as a sixth solving means relating to a radio communication system, in any one of the first to fifth solving means, the multipath determining means includes the fundamental power detected by the signal power detecting means and Means for calculating the average value of the noise power and determining the magnitude of the influence of multipath based on the average value are adopted.

  In the present invention, as a seventh solving means relating to the radio communication system, in any one of the first to sixth solving means, the second communication device includes the signal power detection means and the multipath determination means. And the second communication switching means switches to multicarrier communication when the influence of multipath is large based on the determination result of the multipath determination means included in the second communication device, When the influence of the path is small, a means of switching to single carrier communication is adopted.

  In the present invention, as an eighth solving means relating to the radio communication system, in any one of the first to seventh solving means, the first communication device is a base station, and the second communication device is portable. A means of being a terminal is adopted.

  Further, in the present invention, as a first solving means related to the base station, a base station that transmits / receives a signal to / from a mobile terminal, the signal power detecting means for detecting the fundamental wave power and noise power of the received signal by Fourier transform processing Multipath determination means for determining the magnitude of the influence of multipath based on the fundamental wave power and the noise power, and multicarrier that is an instruction to switch to multicarrier communication based on the determination result of the multipath determination means A communication switching instruction transmitting unit that transmits a communication switching instruction or a single carrier communication switching instruction that is a switching instruction to single carrier communication, and a first communication switching unit that switches communication with a mobile terminal to multicarrier communication or single carrier communication The method of comprising is adopted.

  According to the present invention, the wireless communication system detects the fundamental wave power and the noise power of the received signal by Fourier transform processing, and the magnitude of the influence of multipath based on the fundamental wave power and the noise power. Multi-path determination means for determining a multi-carrier communication based on a determination result of the multi-path determination means, a multi-carrier communication switching instruction that is a switching instruction to multi-carrier communication, or a single carrier communication switching that is a switching instruction to single-carrier communication The first communication comprising: a communication switching instruction transmitting unit that transmits an instruction; and a first communication switching unit that switches communication with the second communication device to multicarrier communication or single carrier communication based on the switching instruction. When the device and the multicarrier communication switching instruction are received, the communication with the first communication device By switching to carrier communication and receiving the single carrier communication switching instruction, the second communication device comprising a second communication switching means for switching communication with the first communication device to single carrier communication, The second communication apparatus switches to multi-carrier communication having strong resistance against multipath when the influence of multipath is large, and when the influence of multipath is small, the resistance to multipath is weak but power consumption can be suppressed. Since switching to single carrier communication, deterioration of communication quality due to multipath can be suppressed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a wireless communication system having a mobile terminal and a base station that communicates with the mobile terminal.
FIG. 1 is a system configuration diagram of a wireless communication system A according to the present embodiment.
As shown in FIG. 1, the wireless communication system A includes a mobile terminal A1 and a base station A2.

  The mobile terminal A1 and the base station A2 use multicarrier communication based on orthogonal frequency division multiple access (OFDMA) in the downlink direction, and multicarrier communication and frequency division multiple access in the uplink direction based on OFDMA ( It is a communication apparatus that communicates with each other by dynamically switching single carrier communication by FDMA (Frequency Division Multiple Access) system. The base station A2 is discretely arranged with a predetermined interval from other base stations (not shown), and communicates with the mobile terminal A1 in the cell assigned to each base station A2.

  As is well known, the OFDMA system means that the mobile terminal A1 and other mobile terminals (not shown) share all subcarriers in an orthogonal relationship, and a group of a plurality of subcarriers is positioned as one group. It is a technology that realizes multiple access by assigning to a network. The FDMA scheme is a technique for realizing multiple access by dividing the entire frequency band into a plurality of bands and assigning each band to the mobile terminal A1 and other mobile terminals as carriers. And in the radio | wireless communications system A, one carrier is allocated to portable terminal A1 in a FDMA system.

  Next, functional configurations of the mobile terminal A1 and the base station A2 will be described with reference to FIGS. FIG. 2 is a functional block diagram illustrating a functional configuration of the mobile terminal A1 of the wireless communication system A according to the present embodiment, and FIG. 3 illustrates a functional configuration of the base station A2 of the wireless communication system A according to the present embodiment. It is a functional block diagram. As shown in FIG. 2, the mobile terminal A <b> 1 includes a communication unit 1, an operation unit 2, a display unit 3, and a control unit 4.

Under the control of the communication unit 1 and the control unit 4, the base station A2 transmits and receives various signals such as voice signals, data signals, and control signals.
The operation unit 2 includes various operation keys such as a power key, a numeric keypad, and various function keys, and outputs user operation instructions for these operation keys to the control unit 4.
The display unit 3 is, for example, a liquid crystal monitor or an organic EL monitor, and displays various screens composed of images and characters based on signals input from the control unit 4.

  The control unit 4 inputs and outputs signals to and from the internal memory composed of a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), and the communication unit 1, the operation unit 2, and the display unit 3. Each interface circuit is configured to control the entire operation of the portable terminal A1 based on a control program stored in the ROM, a signal received by the communication unit 1, and an operation instruction received by the operation unit 2.

  The control program stored in the ROM includes an OFDMA / FDMA switching program, and the control unit 4 uses the OFDMA / FDMA switching program in uplink communication based on the OFDMA / FDMA switching program. The OFDM / FDMA switching process is performed. The details of the OFDMA / FDMA switching process executed by the control unit 4 will be described below as the operation of the mobile terminal A1.

And base station A2 is comprised from the receiving part 11, the transmission part 12, and the control part 13, as shown in FIG. The reception unit 11 includes a radio signal reception unit 11a, a GI (Guard interval) removal demodulation processing unit 11b, and a GI-containing demodulation processing unit 11c.
The radio signal receiving unit 11a converts a multiplexed signal (OFDM signal) input from the mobile terminal A1 via an antenna from an RF frequency band signal to an IF frequency band signal, and converts the IF frequency band OFDM signal to a low-noise amplifier. The amplified OFDM signal is converted from an analog signal to a digital signal by an A / D converter, and the OFDM signal is output to the GI removal demodulation processing unit 11b and the GI-containing demodulation processing unit 11c.

The GI removal demodulation processing unit 11b includes a GI removal unit 11b-1, a first fast Fourier transform unit 11b-2, a first subcarrier demodulation unit 11b-3, and a first P / S (Parallel Serial) conversion unit 11b-. It is composed of four.
The GI removal unit 11b-1 removes the guard interval from the OFDM signal input from the radio signal reception unit 11a and outputs the guard interval to the first fast Fourier transform unit 11b-2.

  The first fast Fourier transform unit 11b-2 converts the OFDM signal input from the guard interval removal unit 2b into a modulated signal for each subcarrier by Fourier transform processing, and each modulated signal is demodulated for each sub first subcarrier demodulation. To the unit 11b-3. Further, the first fast Fourier transform unit 11b-2 detects the power of each subcarrier and the power of noise by Fourier transform processing, and inputs the power of each subcarrier and the power of noise to the control unit 13.

The first subcarrier demodulating units 11b-3 are provided in the same number as the subcarriers. The modulated signals are phase-corrected / frequency-corrected / power-corrected and digitally demodulated based on the subcarriers to be converted into data signals. The data signal is output to the first P / S converter 11b-4.
The first P / S conversion unit 11b-4 combines a plurality of data signals input from the first subcarrier demodulation units 11b-3 into one data signal and outputs the data signal to the control unit 13.

  Further, the GI-containing demodulation processing unit 11c includes a second fast Fourier transform unit 11c-1, a second subcarrier demodulation unit 11c-2, and a second P / S conversion unit 11c-3. The first fast Fourier transform unit 11b-2, the second fast Fourier transform unit 11c-1, the first subcarrier demodulation unit 11b-3, the second subcarrier demodulation unit 11c-2, and the first P / S conversion unit 11b- 4 and the second P / S converter 11c-3 have the same function.

The transmission unit 12 transmits the OFDM signal generated by executing serial / parallel conversion processing, subcarrier modulation processing, inverse fast Fourier transform processing, and the like to the data signal under the control of the control unit 13 to the mobile terminal A1. To do.
The control unit 13 includes an internal memory composed of a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM), and an interface circuit that inputs and outputs signals to and from the reception unit 11 and the transmission unit 12. Etc., and controls the overall operation of the base station A2 based on a control program stored in the ROM and a signal received by the receiving unit 11.

  The control program stored in the ROM includes a multipath determination program, and the control unit 13 executes a multipath determination process based on the multipath determination program and a signal received from the mobile terminal A1. The details of the multipath determination process executed by the control unit 13 will be described below as the operation of the base station A2.

Next, operations of the mobile terminal A1 and the base station A2 in the wireless communication system A configured as described above will be described with reference to the sequence diagram of FIG. FIG. 4 is a sequence diagram showing operations of the mobile terminal A1 and the base station A2 of the wireless communication system A according to the present embodiment.
First, when the mobile terminal A1 is communicating in the uplink direction by the OFDMA method, the control unit 4 of the mobile terminal A1 causes the base station A2 to transmit the OFDM signal to the communication unit 1. (Step S1)
Then, in the base station A2, when the OFDM signal from the mobile terminal A1 is input to the radio signal receiving unit 11a via the antenna, the radio signal receiving unit 11a performs frequency conversion processing and analog / digital conversion to the OFDM signal. Conversion processing and the like are performed, and this OFDM signal is output to the GI removal demodulation processing unit 11b and the GI-containing demodulation processing unit 11c.

In the GI removal demodulation processing unit 11b, the GI removal unit 11b-1 removes the guard interval from the OFDM signal input from the radio signal reception unit 11a, and the OFDM signal (first OFDM signal) from which the guard interval is removed is first. The result is output to the fast Fourier transform unit 11b-2.
The first fast Fourier transform unit 11b-2 converts the first OFDM signal input from the GI removal unit 11b-1 into a modulation signal for each subcarrier by Fourier transform processing, and converts each modulation signal to each first subcarrier. The result is output to the demodulator 11b-3. The first fast Fourier transform unit 11b-2 detects the power of each subcarrier and the noise power from the first OFDM signal by Fourier transform processing, and outputs the power of each subcarrier and the noise power to the control unit 13. To do.

  The first subcarrier demodulator 11b-3 performs phase correction / frequency correction / power correction on the modulated signal and digitally demodulates the signal based on the subcarrier to convert it into a data signal of received data. The data is output to the S converter 11b-4. The first P / S conversion unit 11b-4 combines a plurality of data signals input from the first subcarrier demodulation units 11b-3 into one data signal and outputs the data signal to the control unit 13.

  In the GI-containing demodulation processing unit 11c, the second fast Fourier transform unit 11c-1 modulates the OFDM signal (second OFDM signal) input from the radio signal receiving unit 11a by a Fourier transform process for each subcarrier. And each modulated signal is output to each second subcarrier demodulator 11c-2. Further, the second fast Fourier transform unit 11c-1 detects the power of each subcarrier and the power of noise from the second OFDM signal by Fourier transform processing, and outputs the power of each subcarrier and the power of noise to the control unit 13. To do.

The second subcarrier demodulator 11c-2 performs phase correction / frequency correction / power correction on the modulated signal and digitally demodulates it based on the subcarrier to convert it into a data signal of received data. The data is output to the S converter 11c-3.
The second P / S conversion unit 11c-3 combines a plurality of data signals input from the second subcarrier demodulation units 11c-2 into one data signal and outputs the data signal to the control unit 13.

  The control unit 13 calculates an SNR (Signal to Noise ratio) of the first OHDM signal based on the power and noise of each subcarrier of the first OHDM signal input from the first high-speed Fourier transform unit 11b-2. The SNR (Signal to Noise ratio) of the second OHDM signal is calculated based on the power and noise of each subcarrier of the second OHDM signal input from the high speed Fourier transform unit 11c-1. Then, the control unit 13 compares the SNR of the first OFDM signal and the SNR of the second OFDM signal, and determines whether there is a difference equal to or greater than a predetermined threshold value between the SNRs of the first OFDM signal and the second OFDM signal ( Step S2).

  If it is determined “NO” in step S2, that is, if there is no difference greater than a predetermined threshold value between the SNRs of the first OFDM signal and the second OFDM signal, the control unit 13 carries the FDMA system switching instruction. When transmitting to the terminal A1 to the transmission unit 12 (step S3) and determining “YES” in step S2, that is, when the SNR between the first OFDM signal and the second OFDM signal is greater than a predetermined threshold value In this case, the transmitting unit 12 is caused to transmit the OFDMA system switching instruction to the portable terminal A1 (step S4). Further, the control unit 13 executes various processes based on the data signal input from the GI removal demodulation processing unit 11b.

Here, the relationship between the SNR difference between the first OFDM signal and the second OFDM signal and the multipath will be described.
When the multipath occurs, the base station A2 receives the direct wave and the reflected wave at the same time, and the signal actually received by the base station A2 is a composite wave of the direct wave and the reflected wave. At this time, a portion where the previous symbol and the subsequent symbol overlap in the signal becomes noise. For this reason, by providing a guard interval so as to leave a space between the preceding and following symbols, the overlapping portion of the preceding and following symbols is ignored, and the generation of noise is suppressed. The card interval is generated based on the subsequent symbols.

  Then, by removing the guard interval from the combined wave of the direct wave and the reflected wave, a first OFDM signal composed of symbols from which noise has been removed is generated. In addition, when the guard interval is not removed, a second OFDM signal including overlapping of front and rear symbols, that is, noise is generated. When the number of reflected waves increases due to multipath, the proportion of noise included in the second OFDM signal increases, and a large difference occurs in the SNR between the first OFDM signal and the second OFDM signal.

The control unit 4 of the portable terminal A1 determines whether or not the communication unit 1 has received an FDMA system switching instruction or an OFDMA system switching instruction from the base station A2 (step S5), and has received the FDMA system switching instruction in step S5. If it is determined, the uplink communication method is switched from the OFDMA method to the FDMA method (step S6). If it is determined in step S5 that an OFDMA method switching instruction is received, the uplink communication is continued. Is executed by the OFDMA method (step S7). In addition, if the control unit 4 has already performed uplink communication by the FDMA scheme, when receiving the FDMA scheme switching instruction, the control unit 4 continuously performs the uplink communication by the FDMA scheme and performs the OFDMA scheme switching instruction. Is switched from the FDMA system to the OFDMA system.
Then, the control unit of the base station A2 switches the uplink communication to the OFDMA method or the FDMA method based on the response signal received by the receiving unit 11 from the mobile terminal A1.

  As described above, when the base station A2 receives the signal from the portable terminal A1, the base station A2 generates a signal from which the guard interval is removed and a signal from which the guard interval is not removed, and performs a Fourier transform process on both signals. The power of the wave and noise is detected, and the control unit 13 calculates the SNR of both signals based on the fundamental wave and noise power of both signals, and there is a difference greater than a predetermined threshold value between the two SNRs. If the influence of multipath is large, that is, if the influence of the multipath is large, an OFDMA system switching instruction is transmitted to the mobile terminal A1, and if there is no difference greater than a predetermined threshold value between the two SNRs, that is, multipath When the influence of the multipath is small, the portable terminal A1 transmits the FDMA scheme switching instruction to the portable terminal A1, so that the portable terminal A1 Run the multi-carrier communication system, when the influence of multi-path is small also, in order to perform a single-carrier communication of the FDMA system, the mobile terminal A1 can suppress the deterioration of the communication quality due to the influence of the multi-path. In addition, when the influence of multipath is small, the mobile terminal A1 performs FDMA single carrier communication and does not always perform communication using the OFDMA method with high power consumption, so that power consumption can be suppressed.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the influence of multipath is determined by comparing the SNRs of the first OFDM signal and the second OFDM signal, but the present invention is not limited to this.
For example, the power of the fundamental wave and noise is detected by performing Fourier transform processing on each guard interval included in the signal, and the influence of the multipath is determined based on the SNR calculated from the power of the fundamental wave and noise. It may be. As described above, the guard interval is generated based on the subsequent symbol, and when the influence of multipath is small, the guard interval includes the signal of the subsequent symbol as it is. However, when the influence of multipath increases, a lot of noise other than the signal of the subsequent symbol is included. Therefore, the influence of the current multipath can be determined by comparing the SNR of the latest guard interval and the past card interval. Further, the influence of multipath may be determined by detecting the subcarrier and noise power of the symbol of the first OFDM signal, and comparing the fundamental wave and noise power with a predetermined threshold value. When determining the influence of multipath, a temporal average value of the fundamental wave and noise of the signal may be calculated, and the determination may be made based on the average value.

(2) In the above embodiment, the base station A2 determines the influence of multipath, and the mobile terminal A1 uses the OFDMA scheme switching instruction received from the base station A2 or the OFDMA scheme switching instruction based on the FDMA scheme switching instruction. Although the communication and the single carrier communication by the FDMA system are switched, the present invention is not limited to this.
For example, rather than determining the influence of multipath by the base station A2, the mobile terminal A1 itself determines the influence of multipath, and based on the result, performs multicarrier communication by OFDMA and single carrier communication by FDMA. You may make it switch.

(3) In the above embodiment, the control unit 13 calculates the SNR based on the power of each carrier and noise power of the first OFDM signal and the second OFDM signal, and compares the SNR between the first OFDM signal and the second OFDM signal. Thus, although the influence of multipath is determined, the present invention is not limited to this.
For example, multipath using other communication quality information other than SNR such as EVN (Error Vector Magnitude), CIR (Carrier to Interference power Ratio), CNR (Carrier to Noise Ratio), and SINR (Signal to Interference and Noise Ratio). You may make it judge the influence of.

1 is a system configuration diagram of a wireless communication system A according to an embodiment of the present invention. It is a functional block diagram which shows the function structure of portable terminal A1 of the radio | wireless communications system A which concerns on one Embodiment of this invention. It is a functional block diagram which shows the function structure of base station A2 of the radio | wireless communications system A which concerns on one Embodiment of this invention. It is a sequence diagram which shows operation | movement of portable terminal A1 and base station A2 of the radio | wireless communications system A which concerns on one Embodiment of this invention.

Explanation of symbols

A ... wireless communication system, A1 ... mobile terminal, A2 ... base station, 1 ... communication unit, 2 ... operation unit, 3 ... display unit, 4 ... control unit, 11 ... receiving unit, 11a ... wireless signal receiving unit, 11b ... GI removal demodulation processing unit, 11b-1 ... GI removal unit, 11b-2 ... first fast Fourier transform unit, 11b-3 ... first subcarrier demodulation unit, 11b-4 ... first P / S conversion unit, 11c ... GI Content demodulation processing unit, 11c-1 ... second fast Fourier transform unit, 11c-2 ... second subcarrier demodulation unit, 11c-3 ... second P / S conversion unit, 12 ... transmission unit, 13 ... control unit

Claims (9)

A wireless communication system having a first communication device and a second communication device for transmitting and receiving signals,
Signal power detection means for detecting the fundamental wave power and noise power of the received signal by Fourier transform processing;
Multipath determination means for determining the magnitude of the influence of multipath based on the fundamental wave power and the noise power;
A communication switching instruction transmitting unit that transmits a multicarrier communication switching instruction that is a switching instruction to multicarrier communication or a single carrier communication switching instruction that is a switching instruction to single carrier communication based on a determination result of the multipath determining unit; ,
The first communication device comprising: first communication switching means for switching communication with the second communication device to multicarrier communication or single carrier communication based on the switching instruction;
When the multicarrier communication switching instruction is received, the communication with the first communication apparatus is switched to multicarrier communication. When the single carrier communication switching instruction is received, the communication with the first communication apparatus is switched to single carrier communication. And a second communication device comprising two communication switching means.   The communication switching instruction transmitting means instructs switching to multicarrier communication when the determination result of the multipath determining means is larger than a predetermined reference, and when the determination result is smaller than the predetermined reference, the communication switching instruction transmitting means 2. The wireless communication system according to claim 1, wherein switching is instructed. The signal power detection means detects the fundamental wave power and noise power of the first signal obtained by removing the guard interval from the received signal. The multipath determination means is based on the fundamental wave power and noise power of the first signal. The wireless communication system according to claim 1, wherein the magnitude of the influence of the multipath is determined. The signal power detection means detects the fundamental wave power and noise power of the guard interval of the received signal by Fourier transform processing,
The wireless communication system according to claim 1, wherein the multipath determination unit determines the magnitude of the influence of the multipath based on the fundamental wave power and noise power of the guard interval. The signal power detection means detects the fundamental wave power and noise power of the second signal that detects the fundamental wave power and noise power of the first signal and does not remove the guard interval from the received signal,
The multipath determination means determines the magnitude of the influence of multipath by comparing the fundamental wave power and noise power of the first signal with the fundamental wave power and noise power of the second signal. The wireless communication system according to claim 3.   The multipath determination unit calculates a temporal average value of the fundamental wave power and the noise power detected by the signal power detection unit, and determines the magnitude of the influence of the multipath based on the average value. The wireless communication system according to any one of claims 1 to 5. The second communication device includes the signal power detection means and the multipath determination means,
In the second communication switching unit, when the influence of the multipath is large based on the determination result of the multipath determination unit included in the second communication device, the switching to the multicarrier communication is performed and the influence of the multipath is small. In the case, it switches to single carrier communication, The radio | wireless communications system as described in any one of Claims 1-6 characterized by the above-mentioned.   The wireless communication system according to claim 1, wherein the first communication device is a base station, and the second communication device is a mobile terminal. A base station that transmits and receives signals to and from a mobile terminal,
Signal power detection means for detecting the fundamental wave power and noise power of the received signal by Fourier transform processing;
Multipath determination means for determining the magnitude of the influence of multipath based on the fundamental wave power and the noise power;
A communication switching instruction transmitting unit that transmits a multicarrier communication switching instruction that is a switching instruction to multicarrier communication or a single carrier communication switching instruction that is a switching instruction to single carrier communication based on a determination result of the multipath determining unit; ,
A base station comprising first communication switching means for switching communication with a portable terminal to multicarrier communication or single carrier communication.

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