JP2009077267A - Transmission and reception system and transmission and reception method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission and reception system and a transmission and reception method by which a suitable transmission scheme can be selected. <P>SOLUTION: The transmission and reception system 1 performs signal transmission and reception between a first transmission and reception device 100 and a second transmission and reception device 200 according to one transmission scheme selected from a plurality of transmission schemes. The second transmission and reception device 200 is provided with a transmission scheme determining part 231 which determines whether the transmission scheme should be switched to another transmission scheme out of the plurality of transmission schemes or not, according to received signals which are transmitted from the first transmission and reception device 100. Also, the first transmission and reception device 100 or the second transmission or reception device 200 is provided with a transmission scheme selecting part 232 which selects the next transmission scheme according to the result of determination by the transmission scheme determining part 231. Further, the transmission scheme determining part 231 changes the criterion value for determining whether the transmission scheme should be switched to another transmission scheme, according to varying conditions of the status of a propagation channel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission / reception system and a transmission / reception method.

  In recent years, third-generation mobile communication systems (3G) including a W-CDMA (Wideband-Code Division Multiplexing Access) system have become widespread worldwide. In order to realize higher-speed communication, next-generation mobile communication systems are being studied. As a next-generation mobile communication system, a fourth-generation mobile communication system (4G) in which a downlink communication speed is 100 Mbps to 1 Gbps is being studied. However, there is a big difference in system configuration between 3G and 4G. Therefore, in order to bridge the technical and time gap between 3G and 4G, and to achieve a smooth transition to 4G, the same frequency as 3G was used and 4G candidate technology was introduced. Thus, E-UTRA (Evolved Universal Terrestrial Radio Access) that realizes a downlink communication speed of about 100 Mbps is actively discussed in 3GPP (3rd Generation Partnership Project).

  In E-UTRA, which is a next-generation mobile communication system, an OFDMA (Orthogonal Frequency Multiplexing Access) system is adopted as a downlink. Further, E-UTRA employs a technique called AMC (Adaptive Modulation and Coding) that adaptively changes a plurality of modulation schemes and coding rates. . Further, in E-UTRA, a MIMO (Multiple Input Multiple Output) transmission method in which a plurality of antennas are provided on both the transmission side and the reception side and data is transmitted and received using these antennas. Is adopted.

  The MIMO transmission scheme is a technique using Spatial Multiplexing (hereinafter referred to as SM), Beamforming (hereinafter referred to as BF), and Single-stream transmission diversity mode (hereinafter referred to as SD). The transmission system is considered, and switching between these three transmission systems has been proposed (see Non-Patent Document 1).

This is because the characteristics differ depending on the transmission method, and stable communication can be performed by selecting an appropriate transmission method according to the propagation path situation at that time.
3GPP R1-060774, “Evaluation of Downlink MIMO Transmission Mode Selection”

  However, in the conventional transmission / reception system, it becomes impossible to select an appropriate transmission method from the plurality of transmission methods as described above. For example, when the propagation path condition is bad, a transmission method with a low connection quality is selected. There was a possibility. For example, when the terminal is stationary or moving at a low speed, or when the terminal is present in an environment where there is little shielding such as in the suburbs, the propagation path condition tends to change gradually. On the other hand, when the terminal is moving at high speed or when the terminal is present in an environment where there are many shielding objects such as urban areas, the propagation path condition tends to fluctuate drastically. When the propagation path condition fluctuates drastically, the appropriate transmission method will change drastically. Therefore, if the transmission / reception system cannot follow this drastic change, an appropriate transmission method cannot be selected. In particular, when the propagation path conditions fluctuate drastically, when the propagation path conditions are poor, a transmission method with a low connection quality may be selected. In such a case, communication may be disconnected. possible.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a transmission / reception system and a transmission / reception method capable of selecting an appropriate transmission method.

(1) The transmission / reception system of the present invention performs signal transmission / reception between a first transmission / reception device and a second transmission / reception device based on one transmission method selected from among a plurality of transmission methods. In this transmission / reception system, the second transmission / reception device determines whether to switch from the currently selected transmission method to another transmission method based on the signal transmitted from the first transmission / reception device. Department. In addition, the first transmission / reception device or the second transmission / reception device includes a transmission method selection unit that selects a future transmission method based on the determination result by the transmission method determination unit. Further, the transmission method determination unit has a function of changing a determination reference value for determining whether or not to switch to another transmission method based on a fluctuation condition of the propagation path condition.

  According to this transmission / reception system, the second transmission / reception device receives a signal transmitted from the first transmission / reception device. Then, based on the received signal, the transmission method determination unit determines whether or not to switch from the currently selected transmission method to another transmission method. In response to this determination result, the transmission method selection unit selects a future transmission method. Further, the transmission method determination unit changes a determination reference value for determining whether to switch to another transmission method based on the fluctuation condition of the propagation path condition.

  As described above, in the transmission / reception system, the determination reference value for determining whether or not to switch to another transmission method is changed according to the fluctuation condition of the propagation path condition. For this reason, even when the propagation path conditions fluctuate drastically, it is possible to select a transmission method by setting a judgment reference value corresponding to this, and even though the propagation path conditions are poor, the connection quality is improved. A situation where a transmission method that is not so high is selected is suppressed. Therefore, an appropriate transmission method can be selected.

(2) Moreover, in the transmission / reception system of this invention, it is preferable that a transmission system determination part changes a determination reference value by making into a fluctuation condition the frequency which a 1st transmission / reception apparatus and a 2nd transmission / reception apparatus use for transmission / reception of a signal. .

Here, the signals transmitted and received by the first transmission / reception device and the second transmission / reception device vary in propagation path conditions due to multipath fading during communication, but the propagation path conditions tend to vary when the frequency used is high. When the frequency is low, the propagation path condition tends not to fluctuate.
For this reason, it is possible to estimate the ease of fluctuation of the propagation path condition by setting the frequency used for transmission / reception of the signals by both transmission / reception devices, and according to the estimated ease of fluctuation of the propagation path condition. Can be set. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(3) Further, the transmission method determination unit changes the determination reference value so that when the frequency is higher than the predetermined frequency, it is easily determined that the transmission method with the highest connection quality among the plurality of transmission methods should be switched. It is preferable.

  As a result, when the propagation path condition is likely to fluctuate due to multipath fading or the like, the transmission method with the highest connection quality is easily selected. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(4) Moreover, it is preferable that a transmission system determination part changes a determination reference value by making relative movement speed of a 1st transmitter / receiver and a 2nd transmitter / receiver into a fluctuation condition.

  Here, when the relative movement speed is high, the fluctuation of the propagation path condition is likely to become severe, and when the relative movement speed is low, the fluctuation of the propagation path condition tends to be difficult. For this reason, it is possible to estimate the easiness of fluctuation of the propagation path condition by setting the relative movement speed between the transmitting and receiving apparatuses as a fluctuation condition, and a determination reference value corresponding to the easiness of fluctuation of the estimated propagation path condition. Can be set. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(5) Further, the transmission method determination unit sets the determination reference value so that it is easily determined that the transmission method with the highest connection quality among the plurality of transmission methods should be switched when the relative movement speed is higher than the predetermined speed. It is preferable to change.

  As a result, when the relative movement speed is high and the propagation path condition is likely to fluctuate, the transmission method with the highest connection quality is easily selected. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(6) Moreover, it is preferable that a transmission system determination part changes a determination reference value by making the call classification attached in the case of transmission / reception of the signal of a 1st transmitter / receiver and a 2nd transmitter / receiver into a fluctuation condition.

  Here, when the call type is high in real-time characteristics such as those related to voice communication, it is highly necessary to maintain communication even if the propagation path condition fluctuates and deteriorates. On the other hand, if the call type is low, such as for packet communication, the necessity of maintaining communication is not so high even if the propagation path condition fluctuates and deteriorates. For this reason, by setting the call type as a change condition, it is possible to determine whether or not communication with the current transmission method may be performed when the propagation path state changes. Accordingly, it is possible to select an appropriate transmission method in consideration of the case where the propagation path condition fluctuates.

(7) Further, when the call type is a predetermined high-real-time property, the transmission method determination unit can easily determine that the transmission method should be switched to the transmission method with the highest connection quality among the plurality of transmission methods. It is preferable to change the determination reference value.

  This makes it easy to select the transmission method with the highest connection quality when the call type is high in real-time, such as for voice communication, and there is a high need to maintain communication even if the channel conditions fluctuate and deteriorate. . Accordingly, it is possible to select an appropriate transmission method in consideration of the case where the propagation path condition fluctuates.

(8) Moreover, it is preferable that a 1st transmission / reception apparatus is a fixed station, Comprising: The transmission system determination part changes a determination reference value by using the electromagnetic wave environment around a fixed station as a fluctuation condition.

  Here, when there are many shields around the fixed station and the radio wave environment is bad, the fluctuation of the propagation path condition is likely to become severe, and when there are few shields around the fixed station and the radio wave environment is good, the fluctuation of the propagation path condition is difficult to become severe. Tend. For this reason, it is possible to estimate the ease of fluctuation of the propagation path condition by setting the radio wave environment as a fluctuation condition, and set a determination reference value according to the ease of fluctuation of the estimated propagation path condition. be able to. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(9) In addition, the transmission method determination unit may easily determine that the transmission method with the highest connection quality among the plurality of transmission methods should be switched when the radio wave environment is worse than a predetermined radio wave environment. It is preferable to change the determination reference value.

  As a result, when the radio wave environment is poor and the propagation path condition is likely to fluctuate, the transmission method with the highest connection quality is easily selected. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(10) The transmission / reception system of the present invention is a transmission / reception system including a fixed station device and a mobile station device, wherein the fixed station device includes one or a plurality of antennas, and the mobile station device includes: One or a plurality of antennas are provided, the fixed station apparatus transmits the same or different signals from the one or a plurality of antennas to the mobile station apparatus, and the mobile station apparatus is configured to transmit the one or a plurality of antennas. It is possible to selectively adopt one of a plurality of transmission schemes related to signal transmission in which the signal is received by the antenna of the mobile station apparatus, and the mobile station apparatus performs transmission by evaluating the signal received from the fixed station apparatus. A transmission method determination unit for determining whether to change the determination criterion for switching the method, and to determine the transmission method depending on whether the reception quality of the received signal satisfies the determination criterion Also comprises the transmission mode selection unit that determines whether to switch to those.

(11) Further, the transmission / reception method of the present invention is a method of performing signal transmission / reception between the first transmission / reception device and the second transmission / reception device based on one transmission method determined from among a plurality of transmission methods. In this transmission / reception method, a transmission method determination for determining whether or not to switch from the currently selected transmission method to another transmission method based on a signal transmitted from the first transmission / reception device and received by the second transmission / reception device. And a transmission method determination step for determining a future transmission method based on the determination result in the transmission method determination step. Furthermore, in the transmission method determination step, a determination reference value for determining whether or not to switch to another transmission method is changed according to the propagation condition of the propagation path.

  In this transmission / reception system, a transmission method determination step is executed based on a signal transmitted from the first transmission / reception device and received by the second transmission / reception device, so that the currently selected transmission method is switched to another transmission method. It is determined whether or not. Next, a transmission method determination step is executed, and a future transmission method is determined based on the determination result in the transmission method determination step. Further, in the transmission method determination step, a determination reference value for determining whether or not to switch to another transmission method is changed based on the fluctuation condition of the propagation path condition.

  As described above, in the transmission / reception method, the determination reference value for determining whether to switch to another transmission method is changed according to the propagation condition of the propagation path condition. For this reason, even when the propagation path conditions fluctuate drastically, it is possible to select a transmission method by setting a judgment reference value corresponding to this, and even though the propagation path conditions are poor, the connection quality is improved. A situation where a transmission method that is not so high is selected is suppressed. Therefore, an appropriate transmission method can be selected.

  According to the present invention, it is possible to suppress a situation in which a transmission method with low connection quality is selected even though the propagation path condition is bad, and an appropriate transmission method can be selected.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. In the following drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is a configuration diagram showing a transmission / reception system according to the first embodiment of the present invention. The transmission / reception system 1 shown in FIG. 1 selects a transmission method according to a change in propagation path condition from two transmission methods of SM and SD.

  Here, SM is a transmission method in which different data is transmitted from a plurality of antennas on the transmission side, and different data is received by the plurality of antennas on the reception side. According to this transmission method, since the receiving side receives mixed data from each antenna on the transmitting side, signal separation is performed by estimating a matrix representing a propagation path. Further, according to this transmission method, it is possible to obtain a throughput that is at most as many as the number of antennas as compared with the case of transmitting and receiving signals with a single antenna. For example, when the number of antennas is two, the maximum throughput can be doubled.

  SD is a transmission method in which the same data is transmitted from a plurality of antennas on the transmission side. According to this transmission method, the receiving side can increase the accuracy by synthesizing a plurality of received data. For this reason, this transmission method is effective when the signal power is weaker than that of the SM.

  As shown in FIG. 1, the transmission / reception system 1 includes a first transmission / reception device 100 and a second transmission / reception device 200, and the first transmission / reception device 100 is based on one transmission method determined from among a plurality of transmission methods. Signal transmission / reception with the second transmission / reception device 200 is performed. Here, the transmitted / received signal includes control data and user data (for example, audio data).

  More specifically, in the present embodiment, the communication method of signals transmitted from the first transmission / reception device 100 to the second transmission / reception device 200 is OFDMA. That is, the signal is transmitted from the first transmission / reception device 100 to the second transmission / reception device 200 by the OFDMA communication method and the transmission method of either SM or SD. The communication method from the second transmission / reception device 200 to the first transmission / reception device 100 is SC-FDMA (Single Carrier-Frequency Division Multiplexing Access). Note that SC-FDMA, which is a communication method from the second transmission / reception device 200 to the first transmission / reception device 100, does not depend on OFDMA, which is a communication method from the first transmission / reception device 100 to the second transmission / reception device 200. In addition, the communication method is not limited to the above, and other methods such as CDMA (Code Division Multiple Access) may be used.

  Next, details of the first transmission / reception device 100 and the second transmission / reception device 200 will be described. The first transmission / reception device 100 includes an antenna unit 110, a reception unit 120, a control unit 130, and a transmission unit 140. The antenna unit 110 includes a plurality of antennas 111 and 112, and performs signal transmission and signal reception. The antenna unit 110 has a function of transmitting a received signal to the receiving unit 120 and a function of receiving a signal to be transmitted from the transmitting unit 140. In the first embodiment, the plurality of antennas 111 and 112 are two. However, the present invention is not limited to this, and the antenna unit 110 may be configured by three or more antennas.

  The receiving unit 120 performs reception processing on a signal received via the antenna unit 110. The receiving unit 120 has a function of demodulating the signal transferred from the antenna unit 110 to obtain a received data string. In addition, the reception unit 120 includes a data string separation unit 121. The data string separator 121 separates user data and control data from the received data string obtained by demodulation. Furthermore, the receiving unit 120 has a function of transferring the separated user data to the outside and transmitting control data to the control unit 130.

  The control unit 130 controls the entire first transmitting / receiving device 100 and stores information on whether the currently used transmission method is SM or SD.

  The transmission unit 140 performs transmission processing for transmitting a signal via the antenna unit 110. The transmission unit 140 includes a transmission method switching unit 141 and a transmission data string generation unit 142. The transmission system switching unit 141 switches one transmission system currently used for communication to another transmission system. That is, the transmission system switching unit 141 has a function of switching to the SD transmission system when performing communication by SM, and vice versa. The transmission data string generation unit 142 generates a transmission data string according to the transmission method currently in use. The transmission data string is generated by multiplexing control data transmitted from the control unit 130 and user data input from the outside. Note that the information on the transmission method is transmitted from the control unit 130 to the second transmitting / receiving device 200.

  On the other hand, the second transmission / reception device 200 includes an antenna unit 210, a reception unit 220, a control unit 230, and a transmission unit 240, similar to the first transmission / reception device 100. The antenna unit 210 includes a plurality of antennas 211 and 212, and performs signal transmission and signal reception. The antenna unit 210 has a function of transmitting a received signal to the receiving unit 220 and a function of receiving a signal to be transmitted from the transmitting unit 240. In the first embodiment, the plurality of antennas 211 and 212 are two. However, the present invention is not limited to this, and the antenna unit 110 may be configured by three or more antennas. Further, the number of antennas of the first transmission / reception device 100 and the number of antennas of the second transmission / reception device 200 may or may not be the same.

  The receiving unit 220 performs reception processing on a signal received via the antenna unit 210. The receiving unit 220 has a function of demodulating the signal transmitted from the antenna unit 210 to obtain a received data string. Demodulation is performed based on the transmission method information transmitted from the control unit 230. The receiving unit 220 includes a data string separating unit 221 and a transmission method switching unit 222. The data string separator 221 separates user data and control data from the received data string obtained by demodulation. The transmission method switching unit 222 switches the transmission method used for communication to another transmission method. The receiving unit 220 has a function of transmitting the user data separated by the data string separating unit 221 to the outside and transferring the control data to the control unit 230.

  The control unit 230 controls the entire second transmission / reception device 200, and stores information on whether the currently used transmission method is SM or SD. The control unit 230 has a function of transferring transmission method information to the reception unit 220.

  Further, the control unit 230 includes a transmission method determination unit 231 and a transmission method selection unit 232. The transmission method determination unit 231 determines whether to switch from the currently used transmission method to another transmission method. In this determination, the transmission method determination unit 231 uses a signal transmitted and received from the first transmission / reception device 100 and a determination reference value for determining whether to switch to another transmission method. Specifically, when the SN ratio of the received signal is equal to or less than the determination reference value, the transmission method determination unit 231 determines that the transmission method should be switched to SD if the currently used transmission method is SM. In addition, when the SN ratio of the received signal exceeds the determination reference value, the transmission method determination unit 231 determines that switching to SM should be performed if the transmission method currently in use is SD.

  The transmission method selection unit 232 selects a future transmission method based on the determination result by the transmission method determination unit 231. For example, when it is determined by the transmission method determination unit 231 that switching from SD to SM is to be performed, the transmission method selection unit 232 stores information on the changed transmission method and executes processing for switching to SM. In response to this processing, the transmission method switching unit 222 of the reception unit 220 switches the transmission method.

  The transmission unit 240 performs transmission processing for transmitting a signal via the antenna unit 210. The transmission unit 240 includes a transmission data string generation unit 241. The transmission data string generation unit 241 generates a transmission data string. The transmission data string is generated by multiplexing control data transmitted from the control unit 230 and user data input from the outside. Information about whether the future transmission method is SM or SD is transferred from the control unit 230.

  Furthermore, in the transmission / reception system according to the present embodiment, the transmission method determination unit 231 can change the determination reference value based on the fluctuation condition of the propagation path condition. Here, the fluctuation condition of the propagation path condition is a condition defined for estimating the ease of fluctuation of the propagation path condition.

  Specifically, in the first embodiment, the fluctuation condition refers to the frequency used when transmitting a signal from the first transmission / reception device 100 to the second transmission / reception device 200. Here, when the frequency of the signal transmitted from the first transmission / reception device 100 to the second transmission / reception device 200 is high, the propagation path condition tends to fluctuate easily due to multipath fading during communication. On the other hand, when the frequency of the signal is low, the propagation path condition tends to hardly change. For this reason, the transmission method determination unit 231 sets a determination reference value according to the ease of fluctuation of the propagation path condition by setting the frequency level used by the transmission / reception device 100 for signal transmission as a variation condition. It becomes.

Next, a transmission / reception method by the transmission / reception system according to the first embodiment will be described. FIG. 2 is a flowchart illustrating the transmission / reception method according to the first embodiment. 2 is repeatedly executed as long as the communication connection between the first transmission / reception device 100 and the second transmission / reception device 200 is maintained.
In addition, the transmission data string is transmitted in a time series divided every specific time (hereinafter referred to as a slot), and transmitted in the same transmission method in the same slot.
The first transmission method is determined in advance, and the first transmission / reception device 100 and the second transmission / reception device 200 use the same method.

  First, the receiving unit 220 reads information on the currently used transmission method from the control unit 230 (step S1). The antenna unit 210 of the second transmission / reception device 200 receives a signal from the first transmission / reception device 100 (step S2). Then, the received signal is sent to the receiving unit 220. Next, the receiving unit 220 performs demodulation processing based on the transmission method information read in step S1 (step S3). Thereby, a received data string is obtained.

  Next, the data string separation unit 221 separates the received data string obtained by the demodulation process into user data and control data (step S4). Thereafter, the reception unit 220 transmits the separated user data as reception data to the outside, and the control data is transmitted to the control unit 230.

  Next, the control unit 230 executes a transmission method determination process (step S5). By this processing, the determination reference value is changed and the transmission method is determined. And the control part 230 determines whether it was determined by the transmission system determination process in step S5 that the transmission system should be changed (step S6). When it is determined that the transmission method should be changed (step S6: YES), the transmission method selection unit 231 of the control unit 230 stores information on the transmission method changed from the next slot in the control unit 230 (step S7). ).

Next, the transmission data string generation unit 241 generates a transmission data string based on external transmission data (step S8). This transmission data includes control data. At this time, the transmission data sequence generation unit 241 includes the first transmission / reception device 100 including the transmission method information of the next slot, generates a transmission data sequence, and then changes from the next slot of the control unit 230. The information on the transmission method is overwritten on the information on the current transmission method (step S10).
The second transmission / reception device 200 transmits the signal to the first transmission / reception device via the antenna unit 210 (step S14). Then, the process proceeds to step S15.

  On the other hand, when it is determined that the transmission method should not be changed (step S6: NO), the transmission unit 240 reads information on the current transmission method (step S11). Next, the transmission data string generation unit 241 generates a transmission data string (step S12). And the transmission part 240 performs a modulation process (step S13). Thereafter, the second transmission / reception device 200 transmits a signal (step S14). Then, the process proceeds to step S15.

  In step S <b> 15, the antenna unit 110 of the first transmission / reception device 100 receives a signal from the second transmission / reception device 200. Thereafter, the receiving unit 120 performs demodulation processing (step S16), and the data string separation unit 121 separates the received data string obtained by the demodulation processing into user data and control data (step S17). Thereafter, the receiving unit 220 transmits the separated user data to the outside as received data, and transmits control data to the control unit 230.

  Next, the control unit 130 stores transmission mode information from the demodulated control data (step S18), and based on the transmission mode information, the transmission mode switching unit 141 performs the first transmission / reception device in slot units. 100 transmission methods are switched (step S19).

  Next, the transmission data string generation unit 142 generates a transmission data string (step S20). And the transmission part 140 performs a modulation process based on the information of the transmission system of step S18 (step S21), and the 1st transmission / reception apparatus 200 transmits a signal after that (step S22). Thus, the process illustrated in FIG. 2 ends.

  FIG. 3 is a flowchart showing details of the transmission method determination process (step S5) shown in FIG. As shown in FIG. 3, first, the transmission method determination unit 231 determines whether the frequency of the received signal is higher than a predetermined frequency (step S30). When the frequency of the received signal is higher than the predetermined frequency (step S30: YES), the transmission method determination unit 231 sets the determination reference value to a high value A (step S31). This makes it easy for the transmission method determination unit 231 to determine that switching should be made to SD, which is the transmission method with the highest connection quality of the two transmission methods. That is, the transmission method determination unit 231 makes it easy to switch to SD with high connection quality when the reception frequency is high and the propagation path condition is likely to fluctuate violently. Thereafter, the process proceeds to step S33.

  On the other hand, when the frequency of the received signal is not higher than the predetermined frequency (step S30: NO), the transmission method determination unit 231 sets the determination reference value to a low value B (step S32). As a result, the transmission method determination unit 231 can easily determine that the transmission method should be switched to the SM that has the highest communication speed of the two transmission methods. That is, the transmission method determination unit 231 makes it easy to switch to the SM having a high communication speed when the reception frequency is low and the propagation path condition is not likely to change drastically. Thereafter, the process proceeds to step S33.

Next, the transmission method determination unit 231 detects the SN ratio of the received signal. The signal-to-noise ratio is
It is calculated by the SN ratio = a ² / (x−a) ² (hereinafter referred to as equation (1)).

Here, x is pilot symbol phase information output from the receiving unit 220. When the transmission / reception system 1 according to the present embodiment uses a known data symbol pattern such as a preamble, x is corrected as if the data modulation component was removed and all were modulated with the same symbol. is there. Further, a is a value obtained by averaging the phase information to some extent. The transmission method determination unit 231 obtains average signal power by performing a square process on a. Note that the time averaging process is generally determined from the measurement accuracy and the maximum fading speed because it becomes impossible to follow the fading if averaging is performed for a long period with respect to fading fluctuations. The transmission method determination unit 231 obtains the variance by obtaining (x−a) ² using the above x and a to obtain the noise power. The transmission method determination unit 231 also averages noise power for the purpose of improving accuracy.

  After detecting the S / N ratio, the transmission method determination unit 231 determines whether or not the S / N ratio is equal to or less than the determination reference value (step S34). When the S / N ratio is equal to or less than the determination reference value (step S34: YES), the transmission method determination unit 231 determines that the transmission method should be switched to the SD that has the highest connection quality among the two transmission methods (step S35). . And a process transfers to step S6 of FIG.

  On the other hand, when the SN ratio exceeds the determination reference value (step S34: NO), the transmission method determination unit 231 determines that the transmission method should be switched to the SM that has the highest communication speed of the two transmission methods (step S35). ). And a process transfers to step S6 of FIG. As for a transmission method determination method, other documents (for example, 3GPP TSG-Ran Working Group 1 Meeting # 44, R1-060647, DL Adapting STTD / SM Performance Evaluation for E-UTRA.pw. org / ftp / tsg_ran / WG1_RL1 / TSGR1_44 / Docs / R1-060647.zip), SNR-based (based on signal-to-noise ratio), matrix-based, capacity-based, etc. There are various methods. For this reason, in this embodiment, not only the transmission method determination method shown in FIG. 3 but also other transmission method determination methods may be used.

  As described above, according to the transmission / reception system 1 and the transmission / reception method according to the first embodiment, the determination reference value for determining whether or not to switch to another transmission method is changed according to the fluctuation condition of the propagation path condition. To do. For this reason, even when the propagation path conditions fluctuate drastically, it is possible to select a transmission method by setting a judgment reference value corresponding to this, and even though the propagation path conditions are poor, the connection quality is improved. A situation where a transmission method that is not so high is selected is suppressed. Therefore, an appropriate transmission method can be selected.

  In addition, the transmission method determination unit 231 changes the determination reference value using a frequency used when transmitting a signal from the first transmission / reception device 100 to the second transmission / reception device 200 as a variation condition. Here, when the frequency used for signal transmission / reception between the first transmission / reception device 100 and the second transmission / reception device 200 is high, the channel condition tends to fluctuate easily due to multipath fading during communication. On the other hand, when the frequency of the signal is low, the propagation path condition tends to hardly change. For this reason, it is possible to estimate the ease of fluctuation of the propagation path condition by setting the frequency used by the transmission / reception apparatus 100 for signal transmission as a variation condition, and according to the estimated ease of fluctuation of the propagation path condition. A judgment reference value can be set. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

  In addition, when the frequency is higher than the predetermined frequency, the transmission method determination unit 231 changes the determination reference value so that it is easily determined that the transmission method should have the highest connection quality among the plurality of transmission methods. As a result, when the propagation path condition is likely to fluctuate due to multipath fading or the like, the transmission method with the highest connection quality is easily selected. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The transmission / reception system 2 according to the second embodiment is the same as that of the first embodiment, but the configuration and processing contents are partially different. Hereinafter, differences from the first embodiment will be described.

  FIG. 4 is a configuration diagram showing a transmission / reception system 2 according to the second embodiment of the present invention. As illustrated in FIG. 4, the second transmission / reception device 300 according to the second embodiment newly includes a moving speed detection unit 350 in addition to the first embodiment. The moving speed detector 350 detects a relative moving speed between the first transmitting / receiving device 100 and the second transmitting / receiving device 300. That is, when the first transmission / reception device 100 is a fixed station and the second transmission / reception device 300 is a mobile station, the movement speed detection unit 350 detects the relative movement speed between the two.

  Specifically, the moving speed detector 350 detects the relative moving speed as follows. First, the reception unit 320 transmits phase information (more specifically, multi-value data including phase information) included in a signal transmitted from the first transmission / reception device 100 to the movement speed detection unit 350. The moving speed detection unit 350 extracts known data such as pilot symbols from the multi-value data received from the reception unit 320, and obtains phase fluctuation. Then, the moving speed detection unit 350 obtains a frequency distribution from the phase fluctuation and obtains a maximum Doppler frequency from the frequency distribution. Next, the moving speed detection unit 350 detects the moving speed by combining the obtained maximum Doppler frequency and the frequency used for communication. Note that a method for calculating the maximum Doppler frequency is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-198651, and thus detailed description thereof is omitted.

  In the second embodiment, the transmission method determination unit 331 of the control unit 330 is configured to change the determination reference value using the relative movement speed detected by the movement speed detection unit 350 as a variation condition. Here, when the relative movement speed is high, the fluctuation of the propagation path condition is likely to become severe, and when the relative movement speed is low, the fluctuation of the propagation path condition tends to be difficult. For this reason, the transmission method determination unit 331 can estimate the ease of fluctuation of the propagation path condition by setting the relative moving speed between the transmission / reception devices 100 and 300 as a fluctuation condition, and the fluctuation of the estimated propagation path condition can be estimated. The determination reference value corresponding to the ease of setting is set.

  Next, a transmission / reception method by the transmission / reception system 2 according to the second embodiment will be described. FIG. 5 is a flowchart showing a transmission / reception method according to the second embodiment. As illustrated in FIG. 5, the receiving unit 320 of the second transmission / reception device 300 reads information on the currently used transmission method from the control unit 330 (step S <b> 1). Thereafter, the same processing as steps S2 to S4 shown in FIG. 2 is executed, and the processing reaches step S40.

  In step S40, the moving speed detector 350 detects the relative moving speed between the first transmission / reception device 100 and the second transmission / reception device 300 (step S40). As described above, the relative movement speed is detected by obtaining the maximum Doppler frequency and combining the maximum Doppler frequency and the frequency used for communication. Next, transmission method determination processing is executed (step S5). And the process similar to step S6-S22 shown in FIG. 2 is performed, and the process shown in FIG. 4 is complete | finished.

  FIG. 6 is a flowchart showing details of the transmission method determination process (step S5) shown in FIG. As shown in FIG. 6, the transmission method determination unit 331 first determines whether or not the relative movement speed detected by the movement speed detection unit 350 is higher than a predetermined speed (step S50). When the relative movement speed is higher than the predetermined speed (step S50: YES), the transmission method determination unit 331 sets the determination reference value to a high value A (step S31). This makes it easy for the transmission method determination unit 331 to determine that switching should be made to SD, which is the transmission method with the highest connection quality of the two transmission methods. That is, the transmission method determination unit 331 facilitates switching to SD with high connection quality when the relative movement speed is high and the propagation path condition is likely to fluctuate violently. Thereafter, the process proceeds to step S33.

  On the other hand, when the relative movement speed is not higher than the predetermined speed (step S50: NO), the transmission method determination unit 331 sets the determination reference value to a low value B (step S32). As a result, the transmission method determination unit 331 can easily determine that the transmission method should be switched to the SM that has the highest communication speed of the two transmission methods. That is, the transmission method determination unit 331 makes it easy to switch to the SM having a high communication speed when the relative movement speed is low and the propagation path state is difficult to change drastically. Thereafter, the process proceeds to step S33.

  Thereafter, processing similar to steps S33 to S36 shown in FIG. 3 is executed, and the processing shifts to step S6 shown in FIG.

  As described above, according to the transmission / reception system 2 and the transmission / reception method according to the second embodiment, an appropriate transmission method can be selected as in the first embodiment.

  In addition, the transmission method determination unit 331 changes the determination reference value using the relative movement speed between the first transmission / reception device 100 and the second transmission / reception device 300 as a fluctuation condition. Here, when the relative movement speed is high, the fluctuation of the propagation path condition is likely to become severe, and when the relative movement speed is low, the fluctuation of the propagation path condition tends to be difficult. For this reason, by setting the relative movement speed between the transmission / reception devices 100 and 300 as a fluctuation condition, it is possible to estimate the easiness of fluctuation of the propagation path condition, and the determination according to the estimated easiness of the fluctuation of the propagation path condition. A reference value can be set. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

  In addition, when the relative movement speed is higher than the predetermined speed, the transmission method determination unit 331 changes the determination reference value so that it is easily determined that the transmission method with the highest connection quality among the plurality of transmission methods should be switched. . As a result, when the relative movement speed is high and the propagation path condition is likely to fluctuate, the transmission method with the highest connection quality is easily selected. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

  In the second embodiment, the moving speed detection unit 350 detects the relative moving speed based on the multi-value data included in the signal from the first transmission / reception device 100. One or both of the first and second transmission / reception devices 100 and 300 incorporate a GPS (Global Positioning System), thereby detecting their own position and determining the relative movement speed from the time change of their own position. It may be detected. Further, when one or both of the first and second transmission / reception devices 100 and 300 are mounted on a vehicle or the like having a speedometer such as an automobile, the relative movement speed may be detected based on information from the speedometer. good.

(Third embodiment)
Next, a third embodiment of the present invention will be described. The transmission / reception system 3 according to the third embodiment is the same as that of the first embodiment, but the configuration and processing contents are partially different. Hereinafter, differences from the first embodiment will be described.

  FIG. 7 is a configuration diagram showing a transmission / reception system 3 according to the third embodiment of the present invention. In the transmission / reception system 3 according to the third embodiment, the transmission method determination unit 431 of the control unit 430 determines whether or not to switch to another transmission method based on the fluctuation condition of the propagation path state, as in the first embodiment. It is possible to change the judgment reference value for judging the above. However, in the third embodiment, the condition for changing the propagation path condition is different from the first embodiment in order to determine whether the current transmission method may be used when the propagation path condition changes. Refers to the conditions stipulated in. That is, the transmission method determination unit 431 according to the third embodiment determines a future transmission method based on the condition that communication may be performed using the current transmission method when the propagation path condition changes. It has become.

  Specifically, in the third embodiment, the variation condition refers to a call type assigned when signals are transmitted / received between the first transmission / reception device 100 and the second transmission / reception device 400. Here, when the call type is high in real-time characteristics such as those related to voice communication, it is highly necessary to maintain communication even if the propagation path condition fluctuates and deteriorates. On the other hand, if the call type is low, such as for packet communication, the necessity of maintaining communication is not so high even if the propagation path condition fluctuates and deteriorates. For this reason, the transmission method determination unit 431 sets a determination reference value based on whether the current transmission method may be used when the propagation path condition changes by setting the call type as a variable condition. It will be.

  In addition, since the transmission method determination unit 431 sets the determination reference value based on the call type, the reception unit 420 has a function of extracting call type information from the received signal and transmitting the information to the control unit 430. .

  Next, a transmission / reception method by the transmission / reception system 3 according to the third embodiment will be described. FIG. 8 is a flowchart showing a transmission / reception method according to the third embodiment, and is a flowchart showing details of the transmission method determination process (step S5) shown in FIG. As shown in FIG. 8, the transmission method determination unit 431 first determines whether or not the call type transmitted from the reception unit 420 has a predetermined high real-time property (step S60). When the call type is predetermined and has high real-time characteristics, for example, when the call type is related to voice communication (step S60: YES), the transmission method determination unit 431 sets the determination reference value to a high value A. (Step S31). This makes it easy for the transmission method determination unit 431 to determine that switching should be made to SD, which is the transmission method with the highest connection quality of the two transmission methods. That is, the transmission method determination unit 431 indicates that the call type is related to voice communication, and facilitates switching to SD with high connection quality so that communication is not disconnected even when the propagation path condition is deteriorated. Thereafter, the process proceeds to step S33.

  On the other hand, when the call type is not a predetermined high real-time property, for example, when the call type is related to packet communication (step S60: NO), the transmission method determination unit 431 sets the determination reference value to a low value B. Set (step S32). As a result, the transmission method determination unit 431 can easily determine that the transmission method should be switched to the SM that has the highest communication speed of the two transmission methods. That is, the transmission method determination unit 431 makes it easy to switch to an SM having a high communication speed when the call type indicates that related to packet communication and there is little influence even if communication is disconnected when the propagation path state deteriorates. Thereafter, the process proceeds to step S33.

  Thereafter, the same processing as steps S33 to S36 shown in FIG. 3 is executed, and the processing shifts to step S6 shown in FIG.

  As described above, according to the transmission / reception system 3 and the transmission / reception method according to the third embodiment, an appropriate transmission method can be selected as in the first embodiment.

  In addition, the transmission method determination unit 431 changes the determination reference value using a call type attached when signals are transmitted / received between the first transmission / reception device 100 and the second transmission / reception device 400 as a variation condition. Here, when the call type is high in real-time characteristics such as those related to voice communication, it is highly necessary to maintain communication even if the propagation path condition fluctuates and deteriorates. On the other hand, if the call type is low, such as for packet communication, the necessity of maintaining communication is not so high even if the propagation path condition fluctuates and deteriorates. For this reason, by setting the call type as a change condition, it is possible to determine whether or not communication with the current transmission method may be performed when the propagation path state changes. Accordingly, it is possible to select an appropriate transmission method in consideration of the case where the propagation path condition fluctuates.

  In addition, when the call type is a predetermined high real-time property, the transmission method determination unit 431 determines so that it is easy to determine that it should be switched to the transmission method with the highest connection quality among a plurality of transmission methods. Change the reference value. This makes it easy to select the transmission method with the highest connection quality when the call type is high in real-time, such as for voice communication, and there is a high need to maintain communication even if the channel conditions fluctuate and deteriorate. . Accordingly, it is possible to select an appropriate transmission method in consideration of the case where the propagation path condition fluctuates.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. The transmission / reception system 4 according to the fourth embodiment is the same as that of the first embodiment, but part of the processing content is different. Hereinafter, differences from the first embodiment will be described.

  FIG. 9 is a configuration diagram showing a transmission / reception system 4 according to the fourth embodiment of the present invention. In the transmission / reception system 4 according to the fourth embodiment, the first transmission / reception device 500 is a fixed station. The second transmission / reception device 600 is a mobile station.

  Furthermore, the control unit 530 of the first transmission / reception device 500 stores information on the radio wave environment around the fixed station. The radio wave environment around the fixed station is stored in advance based on the number of shielding objects such as buildings around the fixed station. In addition, the transmission unit 530 of the first transmission / reception device 500 has a function of transmitting the signal transmitted to the second transmission / reception device 600 including information on the radio wave environment.

  Further, the reception unit 620 of the second transmission / reception device 600 has a function of transmitting the received radio wave environment information to the control unit 630. Also, the transmission method determination unit 631 of the control unit 630 changes the determination reference value using the radio wave environment around the fixed station as a fluctuation condition. Here, when there are many shields around the fixed station and the radio wave environment is bad, the fluctuation of the propagation path condition is likely to become severe, and when there are few shields around the fixed station and the radio wave environment is good, the fluctuation of the propagation path condition is difficult to become severe. Tend. For this reason, the transmission method determination unit 631 can estimate the easiness of fluctuation of the propagation path condition by setting the radio wave environment as a fluctuation condition, and according to the estimated easiness of fluctuation of the propagation path condition. The determination reference value is set.

Next, a transmission / reception method by the transmission / reception system 4 according to the fourth embodiment will be described. FIG. 10 is a flowchart showing a transmission / reception method according to the fourth embodiment, and is a flowchart showing details of the transmission method determination process (step S5) shown in FIG. As shown in FIG. 10, the transmission method determination unit 631 first determines whether or not the radio wave environment around the fixed station is worse than a predetermined radio wave environment set in advance (step S70). For example, a transmission signal transmitted from each fixed station is received in advance at a plurality of points around the fixed station, and received power is detected. The variance of the received power is obtained. Variance is
Dispersion = [(x1-a) ² + (x2-a) ² +... + (Xn-a) ² ] / n
(Hereinafter referred to as equation (2)).
Here, x1, x2,..., Xn are measured values of received power in time series, n is the number of measured values of received power, and a is a value obtained by averaging the measured values of received power in time series.
This variance is obtained at a plurality of points and averaged (hereinafter referred to as a variance average value). This variance average value is stored in advance.
If the dispersion average value is large, the propagation path condition varies greatly, and the radio wave environment around the fixed station is bad.
It is determined whether or not the radio wave environment is worse than a predetermined radio wave environment based on whether or not the variance average value is larger than a predetermined threshold value.
When the radio wave environment is worse than the predetermined radio wave environment (step S70: YES), the transmission method determination unit 631 sets the determination reference value to a high value A (step S31). This makes it easy for the transmission method determination unit 331 to determine that switching should be made to SD, which is the transmission method with the highest connection quality of the two transmission methods. That is, the transmission method determination unit 631 makes it easy to switch to SD with high connection quality when the radio wave environment is bad and the propagation path condition is likely to fluctuate violently. Thereafter, the process proceeds to step S33.

  On the other hand, when the radio wave environment is not worse than the predetermined radio wave environment (step S70: NO), the transmission method determination unit 631 sets the determination reference value to a low value B (step S32). This makes it easy for the transmission method determination unit 631 to determine that it should switch to SM, which is the transmission method with the highest communication speed of the two transmission methods. In other words, the transmission method determination unit 631 makes it easy to switch to the SM having a high communication speed when the radio wave environment is good and the propagation path condition is difficult to change drastically. Thereafter, the process proceeds to step S33.

  Thereafter, the same processing as steps S33 to S36 shown in FIG. 3 is executed, and the processing shifts to step S6 shown in FIG.

  As described above, according to the transmission / reception system 4 and the transmission / reception method according to the fourth embodiment, an appropriate transmission method can be selected as in the first embodiment.

  Also, the transmission method determination unit 631 changes the determination reference value using the radio wave environment around the fixed station as a fluctuation condition. Here, when the radio wave environment around the fixed station is bad, the fluctuation of the propagation path condition is likely to become severe, and when the radio wave environment around the fixed station is good, the fluctuation of the propagation path condition tends to be difficult. For this reason, it is possible to estimate the ease of fluctuation of the propagation path condition by setting the radio wave environment as a fluctuation condition, and set a determination reference value according to the ease of fluctuation of the estimated propagation path condition. be able to. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

  In addition, when the radio wave environment is worse than a predetermined radio wave environment, the transmission method determination unit 631 can easily determine that a transmission method with the highest connection quality among a plurality of transmission methods should be switched. , Change the criterion value. As a result, when the radio wave environment is poor and the propagation path condition is likely to fluctuate, the transmission method with the highest connection quality is easily selected. Therefore, an appropriate transmission method can be selected according to the ease of fluctuation of the propagation path condition.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to the said embodiment, You may add a change in the range which does not deviate from the meaning of this invention, and combines each embodiment. Also good.

  For example, in the above-described embodiment, an example in which two transmission methods of SM and SD are switched based on the determination reference value has been described. However, the present invention is not limited to this, and in addition to SM and SD, three or more including BF and the like are included. The transmission method may be switched. BF is a transmission method for efficiently transmitting data by controlling the radiation direction of radio waves.

Moreover, in the said embodiment, the 2nd transmission / reception apparatus demonstrated and demonstrated as an example the structure which selects a transmission system and switches the transmission system of a 1st transmission / reception apparatus. For example, the transmission method selection unit 232 is provided in the second transmission / reception devices 200, 300, 400, and 600, and the transmission method switching unit 141 is provided in the first transmission / reception device. However, the configuration is limited to such a configuration. Instead, the transmission method selection unit 232 may be provided in the first transmission / reception device 100. That is, the first transmission / reception device may have a transmission method selection unit, select a transmission method, and change the transmission method of the first transmission / reception device.
Most preferably, each of the first transmission / reception device and the second transmission / reception device includes a transmission method determination unit, a transmission method selection unit, and a transmission method switching unit, so that each transmission method or the other according to the selection result of each transmission method selection unit. The transmission system may be switched, and the configuration may be appropriately determined according to the system requirements.

  In the above embodiment, an example in which the transmission method selection unit 232 is provided in the second transmission / reception devices 200, 300, 400, and 600 has been described. May be provided.

  In the above embodiment, only the fourth embodiment is described in which the first transmission / reception device 500 is a fixed station and the second transmission / reception device 600 is a mobile station. The first transmission / reception device 100 and the second transmission / reception devices 200, 300, and 400 according to the third embodiment may also be configured as a fixed station and a mobile station as appropriate.

  Moreover, although the said embodiment demonstrated the transmission / reception systems 1-4 provided with the function to change a judgment reference value previously, this invention is not limited to these. For example, even a transmission / reception apparatus that cannot execute the transmission / reception method may be a transmission / reception apparatus that can execute the transmission / reception method by programming the contents described in the above embodiments and taking in the program. The program can be imported by, for example, a configuration in which the program is directly imported into the transmission / reception device via a recording medium such as a memory card, or the program is stored in a CD-ROM, and the program recorded on the CD-ROM is transmitted / received. A configuration in which data is written in the transmission / reception device by a PC connected to the device may be used. Furthermore, the transmission / reception apparatus may be configured to download the program via a network.

It is a block diagram which shows the transmission / reception system which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the transmission / reception method which concerns on 1st Embodiment. 3 is a flowchart showing details of a transmission method determination process (step S5) shown in FIG. It is a block diagram which shows the transmission / reception system which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the transmission / reception method which concerns on 2nd Embodiment. 6 is a flowchart showing details of a transmission method determination process (step S5) shown in FIG. It is a block diagram which shows the transmission / reception system which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows the transmission / reception method which concerns on 3rd Embodiment, Comprising: It is a flowchart which shows the detail of the transmission system determination process (step S5) shown in FIG. It is a block diagram which shows the transmission / reception system which concerns on the 4th Embodiment of this invention. It is a flowchart which shows the transmission / reception method which concerns on 4th Embodiment, Comprising: It is a flowchart which shows the detail of the transmission system determination process (step S5) shown in FIG.

Explanation of symbols

1 to 4 ... transmission / reception system, 100, 500 ... first transmission / reception device, 200, 300, 400, 600 ... second transmission / reception device, 110, 210 ... antenna unit, 111, 112, 211, 212 ... Antenna, 120, 220, 320, 420, 620 ... Reception unit, 121, 221 ... Data string separation unit, 130, 230, 330, 430, 530, 630 ... Control unit, 140 , 240, 540... Transmission unit, 141, 222... Transmission method switching unit, 142, 241... Transmission data string generation unit, 231, 331, 431, 631. ..Transmission method selection unit, 350 ... Movement speed detection unit

Claims (11)

A transmission / reception system that performs signal transmission / reception between a first transmission / reception device and a second transmission / reception device based on one transmission method selected from among a plurality of transmission methods,
The second transmission / reception device determines whether to switch from the first transmission method to another transmission method among a plurality of transmission methods based on a signal transmitted from the first transmission / reception device. It has a method determination unit,
The first transmission / reception device or the second transmission / reception device includes a transmission method selection unit that selects a future transmission method based on a determination result by the transmission method determination unit,
The transmission / reception system, wherein the transmission method determination unit changes a determination reference value for determining whether or not to switch to the other transmission method based on a propagation path condition variation condition. The said transmission system determination part changes the said determination reference value by making into a fluctuation condition the frequency which a said 1st transmission / reception apparatus and a said 2nd transmission / reception apparatus use for the transmission / reception of a signal. Sending and receiving system. The transmission method determination unit changes the determination reference value so that it is easily determined that the transmission method having the highest connection quality among the plurality of transmission methods should be switched when the frequency is higher than a predetermined frequency. The transmission / reception system according to claim 2. The transmission method determination unit changes the determination reference value using a relative movement speed between the first transmission / reception device and the second transmission / reception device as the variation condition. The transmission / reception system according to any one of the items. The transmission method determination unit changes the determination reference value so that when the relative moving speed is higher than a predetermined speed, it is easy to determine that the transmission method with the highest connection quality among the plurality of transmission methods should be switched. The transmission / reception system according to claim 4. The transmission method determination unit changes the determination reference value by using a call type attached at the time of signal transmission / reception between the first transmission / reception device and the second transmission / reception device as the variation condition. The transmission / reception system according to any one of claims 1 to 5. The transmission method determination unit, when the call type is a predetermined high real-time property, so that it is easy to determine that it should be switched to the transmission method with the highest connection quality among the plurality of transmission methods, The transmission / reception system according to claim 6, wherein the determination reference value is changed. The first transceiver is a fixed station,
The transmission / reception system according to any one of claims 1 to 7, wherein the transmission method determination unit changes the determination reference value using a radio wave environment around the fixed station as the variation condition. . When the radio wave environment is worse than a predetermined radio wave environment, the transmission method determination unit may easily determine that the transmission method should be switched to the transmission method with the highest connection quality among the plurality of transmission methods. The transmission / reception system according to claim 8, wherein the determination reference value is changed. A transmission / reception system comprising a fixed station device and a mobile station device,
The fixed station device includes one or more antennas,
The mobile station device includes one or more antennas,
The fixed station device transmits the same or different signals from the one or more antennas to the mobile station device,
The mobile station apparatus can selectively adopt one of a plurality of transmission schemes related to signal transmission in which the signal is received by the one or more antennas,
The mobile station device includes a transmission method determination unit that determines whether to change a determination criterion of whether to switch the transmission method by evaluating a signal received from the fixed station device,
A transmission / reception system comprising a transmission method selection unit that determines whether or not to switch a transmission method to another depending on whether or not reception quality of a received signal satisfies the determination criterion. A transmission / reception method for performing signal transmission / reception between a first transmission / reception device and a second transmission / reception device based on one transmission method determined among a plurality of transmission methods,
Transmission for determining whether to switch from the first transmission scheme to another transmission scheme among a plurality of transmission schemes based on a signal transmitted from the first transmission / reception device and received by the second transmission / reception device. A method determination step;
A transmission method determination step for determining a future transmission method based on the determination result in the transmission method determination step;
In the transmission method determination step, a determination reference value for determining whether or not to switch to the other transmission method is changed according to a propagation condition of a propagation path condition.

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