JP2006067236A - Radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To conduct a radio communication having a high efficiency in a radio communication system controlling the set period of an adaptive modulation parameter in response to the travel speed of a mobile station device. <P>SOLUTION: A radio communication device adaptively changes a modulation system in response to the status of a propagation path. The radio communication device has an adaptive modulator (108) setting the adaptive modulation parameter on the basis of a propagation-path information received from another radio communication device as a communication opposite party and a speed estimator (104) outputting a speed estimating information by estimating the travel speed of another radio communication device on the basis of a signal received from another radio communication device. The radio communication device further has a set-period control unit (108) controlling a period setting the adaptive modulation parameter by the adaptive modulator on the basis of the speed estimating information. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radio communication system that performs modulation in accordance with propagation path conditions, and more particularly to a radio communication system that controls the setting cycle of adaptive modulation parameters in accordance with the moving speed of a mobile station apparatus.

2. Description of the Related Art Conventionally, with an increase in transmission speed in wireless communication, the frequency band used is also expanded. In addition, there is a great demand for expansion of transmission amount and improvement of transmission quality in mobile communication, and a communication method that takes into account disturbances that occur outside a stationary environment such as fading is desired. Further, since the frequency selectivity is lowered when the occupied frequency is widened, the influence of the decrease in the frequency selectivity cannot be ignored. In order to cope with various disturbances including a decrease in frequency selectivity, an adaptive modulation technique that performs modulation according to a propagation environment that changes every moment has been developed. As an example, a method of setting a modulation scheme for each subcarrier in a communication system using OFDM has been proposed.
Appendix Kan, Yoshio Karasawa “Fundamental Study on Throughput Characteristics of Orthogonal Frequency Division Multiple Access (OFDMA) in Multipath Environment”, IEICE Technical Report RCS2001-53 p. 17-24

  The adaptive modulation control as described above is performed at regular intervals. However, when the period of fading as a disturbance approaches the period of adaptive modulation control, adaptive modulation control may not be able to follow the fluctuation, and communication characteristics may deteriorate. This fading frequency usually increases as the moving speed of the mobile station apparatus increases.

  On the other hand, the amount of information necessary for performing adaptive modulation is a considerable amount. For example, in a system using 1024 subcarriers, when selecting from 8 types of subcarrier modulation schemes, information of 3072 bits = 384 bytes is required at a minimum. If each mobile station apparatus connected to the network exchanges this amount of information for each frame, it occupies a considerable proportion of the bandwidth that can be used in the entire system.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a wireless communication system capable of performing highly efficient wireless communication.

  (1) In order to achieve the above object, the present invention has taken the following measures. That is, the wireless communication apparatus according to the present invention is a wireless communication apparatus that adaptively changes the modulation scheme according to the state of the propagation path, and is based on propagation path information received from another wireless communication apparatus that is a communication partner. An adaptive modulation unit that sets an adaptive modulation parameter; a speed estimation unit that estimates a moving speed of the other wireless communication device based on a signal received from the other wireless communication device and outputs speed estimation information; A setting cycle control unit that controls a cycle in which the adaptive modulation unit sets an adaptive modulation parameter based on the speed estimation information.

  As described above, since the adaptive modulation unit controls the period for setting the adaptive modulation parameter based on the moving speed of the communication partner, it is possible to avoid deterioration of communication characteristics due to fading as disturbance, Therefore, it is possible to improve the communication efficiency by preventing the adaptive modulation.

  (2) In the wireless communication device according to the present invention, the speed estimation unit estimates a moving speed of the other wireless communication device by measuring a Doppler frequency from a signal received from the other wireless communication device. It is characterized by that.

  In this way, since the moving speed of the other wireless communication device is estimated by measuring the Doppler frequency having a relationship with the moving speed of the other wireless communication device, the other wireless communication is not required. It is possible to estimate the moving speed of the apparatus.

  (3) Further, in the wireless communication device according to the present invention, the setting cycle control unit is configured so that the cycle for setting the adaptive modulation parameter is proportional to the estimated moving speed of the other wireless communication device. It is characterized by controlling the modulation unit.

  As described above, the adaptive modulation unit is controlled so that the period for setting the adaptive modulation parameter is proportional to the estimated movement speed of the other wireless communication apparatus, so that the movement speed of the other wireless communication apparatus is increased. In this case, in order to make it less susceptible to fading as a disturbance, the period for setting the adaptive modulation parameter is shortened. Thereby, deterioration of communication characteristics can be prevented. On the other hand, when the moving speed of other wireless communication devices decreases, the amount of information necessary for performing adaptive modulation is not small. Therefore, by increasing the period for setting adaptive modulation parameters, redundant adaptive modulation can be performed. It is possible to improve the communication efficiency by preventing the communication.

  (4) In the wireless communication device according to the present invention, the set period control unit may operate the adaptive modulation unit when the estimated movement speed of the other wireless communication device exceeds a first value. Is stopped, and then the operation of the adaptive modulation section is resumed when the estimated moving speed of the other wireless communication apparatus becomes equal to or lower than a second value.

  In this way, the operation of the adaptive modulation unit is stopped when the moving speed of the other wireless communication device exceeds the first value. That is, when the moving speed of another wireless communication device increases and the fading frequency increases so that the adaptive modulation operation cannot follow, the operation of the adaptive modulation unit is stopped. A first value is defined as the threshold value of the moving speed. On the other hand, when the moving speed of the other wireless communication device becomes small and the adaptive modulation operation can follow, the adaptive modulation operation is resumed. A second value is set as the threshold value of the moving speed. As a result, it is possible to improve communication characteristics and communication efficiency.

  (5) In addition, the wireless communication device according to the present invention further includes a fluctuation period measuring unit that measures a fluctuation period of a received wave based on a signal received from the other wireless communication apparatus, and the setting period control unit includes: The adaptive modulation section controls the adaptive modulation parameter to be set at a period n times (n is a natural number) of the measured fluctuation period of the received wave.

  As described above, since the adaptive modulation unit is controlled so as to set the adaptive modulation parameter at a period of n times (n is a natural number) of the measured fluctuation period of the received wave, the communication characteristic is deteriorated due to the influence of the disturbance. It can be effectively prevented.

  (6) In addition, the wireless communication device according to the present invention further includes a fluctuation period measuring unit that measures a fluctuation period of a received wave based on a signal received from the other wireless communication apparatus, and the setting period control unit includes: The adaptive modulation section controls the adaptive modulation parameter to be set at a frame period closest to n times (n is a natural number) of the measured fluctuation period of the received wave.

  As described above, since the adaptive modulation unit controls the adaptive modulation parameter to be set in the frame period closest to n times the fluctuation period of the measured received wave (n is a natural number), the communication characteristics deteriorate due to the influence of disturbance. This can be effectively prevented.

  (7) Further, a base station apparatus according to the present invention is a base station apparatus that adaptively changes a modulation scheme in accordance with a state of a propagation path, and the radio station according to any one of claims 1 to 6 A communication device is provided.

  As described above, since the adaptive modulation unit controls the period for setting the adaptive modulation parameter based on the moving speed of the communication partner, it is possible to avoid deterioration of communication characteristics due to fading as disturbance, Therefore, it is possible to improve the communication efficiency by preventing the adaptive modulation.

  (8) Further, the mobile station apparatus according to the present invention is a mobile station apparatus that adaptively changes a modulation scheme according to a propagation path condition, and is based on a signal received from the base station apparatus according to claim 7. A propagation path estimation unit that estimates the propagation path and outputs propagation path estimation information; and a speed detection unit that detects the moving speed of the local station and outputs speed information, the propagation path estimation information and the speed Information is transmitted to the base station apparatus.

  In this way, since the mobile station apparatus detects its own speed information and transmits it to the base station apparatus, the base station apparatus sets a cycle for setting the adaptive modulation parameter based on the moving speed of the mobile station apparatus. It becomes possible to control. As a result, it is possible to avoid deterioration of communication characteristics due to fading as disturbance, while preventing redundant adaptive modulation and improving communication efficiency.

  (9) Further, in the mobile station apparatus according to the present invention, the speed detection unit includes a GPS signal receiving unit that receives a GPS signal, and detects the moving speed of the own station based on the received GPS signal. It is a feature.

  Thus, since the moving speed of the own station is detected based on the GPS signal, the moving speed can be accurately obtained.

  (10) A radio communication system according to the present invention is a radio communication system that adaptively changes a modulation scheme in accordance with a propagation path condition, and the base station apparatus according to claim 7, And a mobile station apparatus according to claim 9.

  In this way, since the mobile station apparatus detects its own speed information and transmits it to the base station apparatus, the base station apparatus sets a cycle for setting the adaptive modulation parameter based on the moving speed of the mobile station apparatus. It becomes possible to control. As a result, it is possible to avoid deterioration of communication characteristics due to fading as disturbance, while preventing redundant adaptive modulation and improving communication efficiency.

  (11) In addition, the wireless communication method according to the present invention is a wireless communication method that adaptively changes the modulation method according to the state of the propagation path, and is a propagation path received from another wireless communication apparatus that is a communication partner. Setting adaptive modulation parameters based on the information; estimating a moving speed of the other wireless communication device based on a signal received from the other wireless communication device; and outputting speed estimation information; And a step of controlling a period in which the adaptive modulation section sets an adaptive modulation parameter based on the speed estimation information.

  As described above, since the adaptive modulation unit controls the period for setting the adaptive modulation parameter based on the moving speed of the communication partner, it is possible to avoid deterioration of communication characteristics due to fading as disturbance, Therefore, it is possible to improve the communication efficiency by preventing the adaptive modulation.

  According to the present invention, since the adaptive modulation unit controls the period for setting the adaptive modulation parameter based on the moving speed of the communication partner, it is possible to avoid deterioration of communication characteristics due to fading as disturbance. Therefore, it is possible to improve communication efficiency by preventing redundant adaptive modulation. In addition, since the moving speed of the other wireless communication device is estimated by measuring the Doppler frequency having a relationship with the moving speed of the other wireless communication device, the other wireless communication device does not require complicated processing. It is possible to estimate the moving speed.

  In addition, since the adaptive modulation unit is controlled so that the period for setting the adaptive modulation parameter is proportional to the estimated moving speed of the other wireless communication device, when the moving speed of the other wireless communication device increases. In order to reduce the influence of fading as a disturbance, the period for setting the adaptive modulation parameter is shortened. Thereby, deterioration of communication characteristics can be prevented. On the other hand, when the moving speed of other wireless communication devices decreases, the amount of information necessary for performing adaptive modulation is not small. Therefore, by increasing the period for setting adaptive modulation parameters, redundant adaptive modulation can be performed. It is possible to improve the communication efficiency by preventing the communication.

  Further, when the moving speed of the other wireless communication device exceeds the first value, the operation of the adaptive modulation unit is stopped. That is, when the moving speed of another wireless communication device increases and the fading frequency increases so that the adaptive modulation operation cannot follow, the operation of the adaptive modulation unit is stopped. A first value is defined as the threshold value of the moving speed. On the other hand, when the moving speed of the other wireless communication device becomes small and the adaptive modulation operation can follow, the adaptive modulation operation is resumed. A second value is set as the threshold value of the moving speed. As a result, it is possible to improve communication characteristics and communication efficiency.

  In addition, since the adaptive modulation unit is controlled so as to set the adaptive modulation parameter at a period n times (n is a natural number) of the measured fluctuation period of the received wave, it is effective that the communication characteristics deteriorate due to the influence of disturbance. Can be prevented. Furthermore, since the adaptive modulation unit controls the adaptive modulation parameter to be set in the frame period closest to n times the fluctuation period of the measured received wave (n is a natural number), the communication characteristics deteriorate due to the influence of disturbance. Can be effectively prevented.

  Further, since the mobile station apparatus detects the speed information of the own station and transmits it to the base station apparatus, the base station apparatus controls the cycle for setting the adaptive modulation parameter based on the moving speed of the mobile station apparatus. It becomes possible. As a result, it is possible to avoid deterioration of communication characteristics due to fading as disturbance, while preventing redundant adaptive modulation and improving communication efficiency. Moreover, since the moving speed of the own station is detected based on the GPS signal, the moving speed can be accurately obtained.

  In this embodiment, as an example, wireless communication is performed by an adaptive modulation scheme that changes a modulation scheme in units of subcarriers using orthogonal frequency division multiplexing (hereinafter referred to as “OFDM”). A communication system will be described.

(First embodiment)
FIG. 1 is a block diagram illustrating a schematic configuration of a base station apparatus (BS) according to the first embodiment. The base station apparatus 100 receives a radio signal by the reception antenna 101 and outputs a reception signal, and the reception filter 102 removes an unnecessary signal from the signal of the reception antenna. The reception signal from which unnecessary signals are removed is input to the reception data processing unit 103, and the reception data processing unit 103 performs processing for extracting target data from the reception signal.

  The Doppler frequency measuring unit 104 measures the Doppler frequency of the received wave in conjunction with the received data processing unit 103. The frame counter 105 manages the current frame number. The MAC frame processing unit 106 performs reception data / transmission data processing in conjunction with the frame counter 105 and exchanges data with the network I / F 107. A network I / F 107 connects the MAC frame processing unit 106 and a backbone network. The adaptive modulation parameter creation unit 108 determines an adaptive modulation parameter in conjunction with the Doppler frequency measurement unit 104 and the MAC frame processing unit 106.

  The transmission data processing unit 109 performs signal processing on the transmission data from the MAC frame processing unit 106 to obtain a transmission signal. The RF amplifier 110 amplifies the transmission signal to a sufficient output. Then, unnecessary signals are removed by the transmission filter 111 and a radio signal is transmitted from the transmission antenna 112.

  FIG. 2 is a block diagram showing a schematic configuration of the mobile station apparatus (MS) according to the first embodiment. This mobile station apparatus 200 receives a radio signal by the reception antenna 201 and outputs a reception signal, and a reception filter 202 removes an unnecessary signal from the signal of the reception antenna. The reception signal from which unnecessary signals are removed is input to the reception data processing unit 203, and the reception data processing unit 203 performs processing for extracting target data from the reception signal.

  The frame counter 204 manages the current frame number. The MAC frame processing unit 205 processes received data and transmitted data in conjunction with the frame counter 204 and exchanges data with the network I / F 206. A network I / F 206 connects the MAC frame processing unit 205 and the backbone network. Adaptive modulation parameter setting section 207 uses the data obtained by MAC frame processing section 205 to set an adaptive modulation parameter for each block.

  The transmission data processing unit 208 performs signal processing on the transmission data from the MAC frame processing unit 205 to obtain a transmission signal. The RF amplifier 209 amplifies the transmission signal to a sufficient output. Then, unnecessary signals are removed by the transmission filter 210 and a radio signal is transmitted from the transmission antenna 211.

  FIG. 3 is a diagram illustrating a communication topology of the wireless communication system according to the first embodiment. A plurality of mobile station apparatuses 200 a to 200 c are linked to the base station apparatus (BS) 200, and a star type in which all communication passes through the base station apparatus 100 is configured. Here, FDD using another frequency is adopted for uplink / downlink of communication. “Uplink” means communication from the mobile station apparatus (MS) to the base station apparatus (BS), and “Downlink” means communication from the base station apparatus (BS) to the mobile station apparatus (MS). To do.

  The MAC protocol uses fixed-length frames. The slot has a variable length, and slot allocation information is added to the head of the downlink. In adaptive modulation, a modulation method can be selected from BPSK, QPSK, and 16QAM for each subcarrier. Any number of OFDM parameters, such as the number of subcarriers, may be used. In the first embodiment, except for the modulation scheme, it is assumed to be fixed. All parameters of adaptive modulation, including uplink and downlink, are instructed from the base station apparatus. Communication packets are arranged in the slots, and a preamble is added to the head of all communication packets. Using this preamble, data necessary for demodulating the packet is acquired and the propagation path is estimated. A data part follows immediately after the preamble.

  FIG. 4 is a diagram illustrating an example of a frame configuration used in the wireless communication system according to the first embodiment, and FIG. 5 is a diagram illustrating an example of a slot configuration. Moreover, FIG. 6 is a figure which shows an example of alerting | reporting information, and FIG. 7 is a figure which shows an example of the structure of a data packet.

  As shown in FIG. 4, broadcast information is arranged at the head of the downstream frame. The broadcast information includes a base station ID, a frame counter, uplink / downlink slot allocation information, and the like. An example of the notification information is shown in FIG. A downlink slot is arranged behind the broadcast information according to the content of the broadcast information. An upstream random slot is arranged at the head of the upstream frame. This random slot is used for the mobile station apparatus to freely transmit small data to the base station apparatus without receiving slot allocation. For example, it is used for slot allocation requests and connection control. However, since other mobile station apparatuses may also use random slots, if the random slots are used at the same time, communication may not be successful. An uplink slot is arranged behind the random slot according to the content of the broadcast information.

  Data packets are arranged in the up / down slots. An example of the structure of the data packet is shown in FIG. In the header part of the packet, all subcarriers are transmitted by BPSK, and the payload part is adaptively modulated and transmitted.

  In the first embodiment, it is assumed that a connection is formed for communication. However, for connection control, for example, a procedure such as ARIB-STD T70 can be used. However, the present invention is not limited to such a procedure.

  Next, adaptive control in the wireless communication system according to the first embodiment will be described. All subcarriers are assumed to be in the BPSK state as initial values of modulation parameters. This state is assigned to modulation parameter sequence number 0. If 0 is specified for the modulation parameter sequence number in the packet, all subcarriers in the payload portion are also BPSK. BPSK is a modulation method with the highest energy per information bit, and there is a high possibility of successful communication even when the propagation path state is bad. Therefore, in the first embodiment, when data such as ACK fails, data that greatly affects performance is communicated by BPSK.

  In order to start adaptive modulation, the mobile station apparatus first starts by analyzing a preamble attached to the head of broadcast information of the base station apparatus and estimating a downlink propagation path. As shown in FIG. 8, the mobile station apparatus transmits the estimated downlink propagation path information (step S1). Here, various kinds of propagation path information can be used, but in the first embodiment, the propagation path is estimated using “average received power per subcarrier per unit time”. .

  The base station apparatus sets an adaptive modulation parameter for the downlink using the downlink propagation path information received from the mobile station apparatus. A modulation scheme with a large amount of subcarrier information is selected in proportion to the magnitude of received power. Also, the uplink propagation path and the Doppler frequency are estimated from the preamble added to the downlink propagation path information, the adaptive modulation parameter for the uplink is set from the estimated propagation path information, and the mobile station apparatus moves from the estimated Doppler frequency. The speed is estimated, and the update timing of the adaptive modulation parameter is set.

  This update timing is set to the frame period closest to twice the fluctuation period of the received wave estimated from the Doppler frequency. However, when this fluctuation period becomes a period of every frame or less, the adaptive modulation control is temporarily stopped. In this case, the control period is set to 5 frame periods, the adaptive modulation parameters are all set to BPSK, and the state with the best error resistance is maintained for 5 frames.

  As shown in FIG. 8, uplink / downlink adaptive modulation parameters are transmitted from the base station apparatus to the mobile station apparatus (step S2). The base station apparatus must transmit this adaptive modulation parameter in the next frame after receiving the propagation path information from the mobile station apparatus. At this time, a modulation parameter sequence number and a parameter valid time (TTL) are added. The initial value of this parameter valid time uses the set update timing. The modulation parameter sequence number is assumed to be 1 to a certain numerical value, for example, 65535, and is used by simply increasing from 1, and when it reaches a certain numerical value (for example, 65535), it returns to 1 again. The base station apparatus performs slot allocation for the mobile station apparatus to transmit the adaptive modulation parameter ACK when transmitting the adaptive modulation parameter.

  As shown in FIG. 9, when the mobile station apparatus confirms that the modulation parameter data with the modulation parameter sequence number transmitted from the base station apparatus has been normally received, the mobile station apparatus adds the received modulation parameter sequence number to the adaptive modulation parameter. ACK is transmitted to the base station apparatus (step S3). Thereafter, the mobile station apparatus can use the indicated adaptive modulation parameter by indicating the received value in the modulation parameter sequence number for the number of frames indicated in the TTL.

  The mobile station apparatus analyzes the preamble attached to the head of the broadcast information of the base station apparatus again, estimates the propagation path, and moves the downlink propagation path information immediately before the validity period indicated by TTL expires. Send to station device.

  The base station apparatus that has received the new propagation path information estimates the propagation path, estimates the moving speed of the mobile station apparatus from the Doppler frequency, sets up / down adaptive modulation parameters and TTL again, and updates the modulation parameter sequence number. And transmit to the mobile station apparatus. By repeating these operations, adaptive modulation control is performed at intervals according to the moving speed of the mobile station apparatus.

  Note that base station apparatus 100 may include a fluctuation period measurement unit that measures the fluctuation period of the received wave based on the signal received from mobile station apparatus 200. In this case, the adaptive modulation parameter creation unit 108 can set the adaptive modulation parameter in a cycle that is n times (n is a natural number) the fluctuation period of the received wave measured by the fluctuation period measurement unit. On the other hand, the adaptive modulation parameter creation unit 108 can also set the adaptive modulation parameter with a frame period closest to n times (n is a natural number) the fluctuation period of the received wave measured by the fluctuation period measurement unit. Thereby, it can prevent effectively that a communication characteristic deteriorates by the influence of disturbance.

  Next, a recovery method when an error occurs and information transmission is not performed normally will be described. First, the propagation path information transmitted from the mobile station apparatus to the base station apparatus is incorrect. In this case, the mobile station apparatus transmits the adaptive modulation parameter from the base station apparatus in the next frame after transmitting the propagation path information. If it is determined whether it is received or not, the mobile station apparatus operates assuming that the propagation path information is incorrect. In this case, the mobile station apparatus immediately transmits the propagation path information again.

  Next, when the adaptive modulation parameter transmitted from the base station apparatus to the mobile station apparatus is incorrect, the mobile station apparatus cannot distinguish from the case where the propagation path information is incorrect, so the mobile station apparatus will not be able to distinguish from the mobile station apparatus in the next frame. The propagation path information is transmitted again. In this case, the base station apparatus may evaluate the propagation information again and transmit the adaptive modulation parameter. Regardless of which error the mobile station apparatus has, if the propagation path information is newly evaluated and the adaptive modulation parameter is transmitted, the mobile station apparatus operates without any problems.

  Next, in the case where the adaptive modulation parameter ACK transmitted from the mobile station apparatus to the base station apparatus is incorrect, the mobile station apparatus immediately tries to retransmit the adaptive modulation parameter. As shown in FIG. 10, the TTL in the adaptive modulation parameter to be transmitted is changed to a value obtained by reducing the time taken for retransmission. At this time, the mobile station apparatus performs assignment for transmitting the adaptive modulation parameter ACK. If the retransmitted adaptive modulation parameter is correctly received, the mobile station apparatus performs processing according to the adaptive modulation parameter and transmits an adaptive modulation parameter ACK. As described above, even if an error occurs, appropriate communication can be realized.

  As described above, according to the wireless communication system according to the first embodiment, since the cycle for setting the adaptive modulation parameter is controlled based on the moving speed of the mobile station apparatus, the communication characteristics due to fading as disturbances are controlled. While deterioration can be avoided, it is possible to prevent redundant adaptive modulation and improve communication efficiency. In addition, since the moving speed of the mobile station apparatus is estimated by measuring the Doppler frequency that is related to the moving speed of the mobile station apparatus, the moving speed of the mobile station apparatus is estimated without requiring complicated processing. Is possible.

(Second Embodiment)
Next, a mode in which the mobile station apparatus detects the moving speed of the local station based on the GPS signal will be described. FIG. 11 is a block diagram showing a schematic configuration of a base station apparatus (BS) according to the second embodiment. The base station apparatus 300 receives a radio signal by the reception antenna 301 and outputs a reception signal, and a reception filter 302 removes an unnecessary signal from the signal of the reception antenna. The reception signal from which unnecessary signals are removed is input to the reception data processing unit 303, and the reception data processing unit 303 performs processing for extracting target data from the reception signal.

  The frame counter 304 manages the current frame number. The MAC frame processing unit 305 processes received data and transmitted data in conjunction with the frame counter 304 and exchanges data with the network I / F 306. A network I / F 306 connects the MAC frame processing unit 305 and the backbone network. The adaptive modulation parameter creation unit 307 determines an adaptive modulation parameter in conjunction with the MAC frame processing unit 305.

  The transmission data processing unit 308 performs signal processing on the transmission data from the MAC frame processing unit 305 to generate a transmission signal. The RF amplifier 309 amplifies the transmission signal to a sufficient output. Then, unnecessary signals are removed by the transmission filter 310 and a radio signal is transmitted from the transmission antenna 311.

  FIG. 12 is a block diagram showing a schematic configuration of a mobile station apparatus (MS) according to the second embodiment. The mobile station apparatus 400 receives a radio signal by the reception antenna 401 and outputs the reception signal, and the reception filter 402 removes an unnecessary signal from the signal of the reception antenna. The reception signal from which unnecessary signals are removed is input to the reception data processing unit 403, and the reception data processing unit 403 performs processing for extracting target data from the reception signal.

  The frame counter 404 manages the current frame number. The MAC frame processing unit 405 performs reception data / transmission data processing in conjunction with the frame counter 404 and exchanges data with the network I / F 406. The network I / F 406 connects the MAC frame processing unit 405 and the backbone network. The adaptive modulation parameter setting unit 407 sets an adaptive modulation parameter for each block using the data obtained by the MAC frame processing unit 405.

  The GPS measurement unit 408 measures the moving speed of the mobile station device 400 using radio waves from GPS satellites. The transmission data processing unit 409 performs signal processing on the transmission data from the MAC frame processing unit 205 to generate a transmission signal. This transmission signal also includes the moving speed information of the mobile station device 400 measured by the GPS measuring unit 408. The RF amplifier 410 amplifies the transmission signal to a sufficient output. Then, unnecessary signals are removed by the transmission filter 411 and a radio signal is transmitted from the transmission antenna 412.

  Similar to the first embodiment, the communication topology in the second embodiment is configured as shown in FIG. That is, a plurality of mobile station apparatuses 200 a to 200 c are linked to the base station apparatus (BS) 200, and a star type in which all communication passes through the base station apparatus 100 is configured. Here, FDD using another frequency is adopted for uplink / downlink of communication. “Uplink” means communication from the mobile station apparatus (MS) to the base station apparatus (BS), and “Downlink” means communication from the base station apparatus (BS) to the mobile station apparatus (MS). To do.

  The MAC protocol uses fixed-length frames. The slot has a variable length, and slot allocation information is added to the head of the downlink. In adaptive modulation, a modulation method can be selected from BPSK, QPSK, and 16QAM for each subcarrier. Any number of OFDM parameters, such as the number of subcarriers, may be used. In the second embodiment, except for the modulation scheme, it is assumed to be fixed. All parameters of adaptive modulation, including uplink and downlink, are instructed from the base station apparatus. Communication packets are arranged in the slots, and a preamble is added to the head of all communication packets. Using this preamble, data necessary for demodulating the packet is acquired and the propagation path is estimated. A data part follows immediately after the preamble.

  FIG. 4 is a diagram illustrating an example of a frame configuration used in the wireless communication system according to the second embodiment, and FIG. 5 is a diagram illustrating an exemplary slot configuration. Moreover, FIG. 6 is a figure which shows an example of alerting | reporting information, and FIG. 7 is a figure which shows an example of the structure of a data packet.

  As shown in FIG. 4, broadcast information is arranged at the head of the downstream frame. The broadcast information includes a base station ID, a frame counter, uplink / downlink slot allocation information, and the like. An example of the notification information is shown in FIG. A downlink slot is arranged behind the broadcast information according to the content of the broadcast information. An upstream random slot is arranged at the head of the upstream frame. This random slot is used for the mobile station apparatus to freely transmit small data to the base station apparatus without receiving slot allocation. For example, it is used for slot allocation requests and connection control. However, since other mobile station apparatuses may also use random slots, if the random slots are used at the same time, communication may not be successful. An uplink slot is arranged behind the random slot according to the content of the broadcast information.

  Data packets are arranged in the up / down slots. An example of the structure of the data packet is shown in FIG. In the header part of the packet, all subcarriers are transmitted by BPSK, and the payload part is adaptively modulated and transmitted.

  In the second embodiment, it is assumed that a connection is formed for communication. However, for connection control, for example, a procedure such as ARIB-STD T70 can be used. However, the present invention is not limited to such a procedure.

  Next, adaptive control in the wireless communication system according to the second embodiment will be described. All subcarriers are assumed to be in the BPSK state as initial values of modulation parameters. This state is assigned to modulation parameter sequence number 0. If 0 is specified for the modulation parameter sequence number in the packet, all subcarriers in the payload portion are also BPSK. BPSK is a modulation method with the highest energy per information bit, and there is a high possibility of successful communication even when the propagation path state is bad. For this reason, in the first embodiment, when data such as ACK fails, data that greatly affects performance is communicated by BPSK.

  To start adaptive modulation, first, the mobile station apparatus analyzes the preamble attached to the head of the broadcast information of the base station apparatus and estimates the downlink propagation path. In addition, the mobile station device detects its own moving speed using the GPS measurement unit (408). As shown in FIG. 8, the mobile station apparatus transmits the estimated downlink propagation path information to the base station apparatus (step S1). At this time, speed information indicating the moving speed of the mobile station apparatus is transmitted together with the propagation path information. Although various types of propagation path information can be used, the second embodiment uses the average received power for each subcarrier per unit time.

  The base station apparatus sets an adaptive modulation parameter for the downlink using the downlink propagation path information received from the mobile station apparatus. A modulation scheme with a large amount of subcarrier information is selected in proportion to the magnitude of received power. In addition, the uplink propagation path is estimated from the preamble added to the downlink propagation path information, the adaptive modulation parameter for the uplink is set from the estimated propagation path information, and the mobile station apparatus added to the downlink propagation path information The update timing of the adaptive modulation parameter is set from the moving speed.

  This update timing is set to a frame period closest to twice the fluctuation period of the received wave estimated from the moving speed of the mobile station apparatus. However, when this fluctuation period is every frame period or a period less than this, the adaptive modulation control is temporarily stopped. In this case, the control period is set to 5 frame periods, the adaptive modulation parameters are all set to BPSK, and the state with the best error resistance is maintained for 5 frames.

  Next, as shown in FIG. 8, uplink / downlink adaptive modulation parameters are transmitted from the base station apparatus to the mobile station apparatus (step S2). Further, as shown in FIG. 9, when the mobile station apparatus confirms that the modulation parameter data with the modulation parameter sequence number transmitted from the base station apparatus has been normally received, the mobile station apparatus adds the received modulation parameter sequence number and adapts. A modulation parameter ACK is transmitted to the base station apparatus (step S3). Thereafter, the mobile station apparatus can use the adaptive modulation parameter indicated by indicating the received value in the modulation parameter sequence number for the number of frames indicated in the TTL.

  The mobile station apparatus re-analyzes the preamble attached to the head of the broadcast information of the base station apparatus again immediately before the validity period indicated by TTL expires, estimates the propagation path, and uses the downlink propagation path information as the base station apparatus Send to.

  The base station apparatus that has received the new propagation path information estimates the propagation path, and again determines the uplink / downlink adaptive modulation parameters and TTL based on the moving speed information of the mobile station apparatus obtained from the GPS measurement unit (408). Set, update the modulation parameter sequence number, and transmit to the mobile station apparatus.

  By repeating such operations, adaptive modulation control is performed at intervals corresponding to the moving speed of the mobile station apparatus.

  Next, a recovery method when an error occurs and information transmission is not performed normally will be described. First, the propagation path information transmitted from the mobile station apparatus to the base station apparatus is incorrect. In this case, the mobile station apparatus transmits the adaptive modulation parameter from the base station apparatus in the next frame after transmitting the propagation path information. If it is determined whether it is received or not, the mobile station apparatus operates assuming that the propagation path information is incorrect. In this case, the mobile station apparatus immediately transmits the propagation path information again.

  Next, when the adaptive modulation parameter transmitted from the base station apparatus to the mobile station apparatus is incorrect, the mobile station apparatus cannot distinguish from the case where the propagation path information is incorrect. Again transmits the propagation path information. In this case, the base station apparatus may evaluate the propagation information again and transmit the adaptive modulation parameter. Regardless of which error the mobile station apparatus has, if the propagation path information is newly evaluated and the adaptive modulation parameter is transmitted, the mobile station apparatus operates without any problems.

  Next, in the case where the adaptive modulation parameter ACK transmitted from the mobile station apparatus to the base station apparatus is incorrect, the mobile station apparatus immediately tries to retransmit the adaptive modulation parameter. As shown in FIG. 10, the TTL in the adaptive modulation parameter to be transmitted is changed to a value obtained by reducing the time taken for retransmission. At this time, the mobile station apparatus performs allocation for transmitting the adaptive modulation parameter ACK. If the retransmitted adaptive modulation parameter is correctly received, the mobile station apparatus performs processing according to the adaptive modulation parameter and transmits an adaptive modulation parameter ACK. As described above, even if an error occurs, appropriate communication can be realized.

  As described above, according to the wireless communication system according to the second embodiment, since the cycle for setting the adaptive modulation parameter is controlled based on the moving speed of the mobile station apparatus, the communication characteristics due to fading as disturbances are controlled. While deterioration can be avoided, it is possible to prevent redundant adaptive modulation and improve communication efficiency. Moreover, since the moving speed of the own station is detected based on the GPS signal, the moving speed can be accurately obtained.

  In the above description, as a method for measuring the moving speed of the mobile station apparatus, the case where the Doppler frequency is used (first embodiment) and the case where the GPS signal is used (second embodiment) are shown. However, the present invention is not limited to these. For example, in the case of a wireless communication device mounted on an automobile as the mobile station apparatus, the moving speed of the automobile may be measured by an axle sensor. Moreover, you may make it measure an acceleration using an acceleration sensor. Furthermore, it is also possible to detect the moving speed of the mobile station device using, for example, an ultrasonic sensor, a laser sensor, and an airspeed meter mounted on the automobile.

It is a block diagram which shows schematic structure of the base station apparatus which concerns on 1st Embodiment. It is a block diagram which shows schematic structure of the mobile station apparatus which concerns on 1st Embodiment. It is a figure which shows the topology of communication. It is a figure which shows the structural example of a flame | frame. It is a figure which shows the structural example of a slot. It is a figure which shows an example of alerting | reporting information. It is a figure which shows an example of the structure of a data packet. It is a sequence chart in the case of performing adaptive modulation control. It is a figure which shows the structural example of a flame | frame. It is a figure which shows the structural example of a flame | frame. It is a block diagram which shows schematic structure of the base station apparatus which concerns on 2nd Embodiment. It is a block diagram which shows schematic structure of the mobile station apparatus which concerns on 2nd Embodiment.

Explanation of symbols

100 base station device 104 Doppler frequency measurement unit 106 MAC frame processing unit 108 adaptive modulation parameter creation unit 200 mobile station device 300 base station device 305 MAC frame processing unit 307 adaptive modulation parameter creation unit 400 mobile station device 405 MAC frame processing unit 407 adaptation Modulation parameter setting unit 408 GPS measurement unit

Claims (11)

A wireless communication device that adaptively changes a modulation scheme according to the state of a propagation path,
An adaptive modulation unit that sets an adaptive modulation parameter based on propagation path information received from another wireless communication device that is a communication partner;
Based on a signal received from the other wireless communication device, a speed estimation unit that estimates a moving speed of the other wireless communication device and outputs speed estimation information;
A wireless communication apparatus comprising: a setting cycle control unit that controls a cycle in which the adaptive modulation unit sets an adaptive modulation parameter based on the speed estimation information.   The wireless communication apparatus according to claim 1, wherein the speed estimation unit estimates a moving speed of the other wireless communication apparatus by measuring a Doppler frequency from a signal received from the other wireless communication apparatus.   2. The setting period control unit controls the adaptive modulation unit so that a period in which the adaptive modulation parameter is set is proportional to the estimated movement speed of the other wireless communication device. Wireless communication device.   The set period control unit stops the operation of the adaptive modulation unit when the estimated moving speed of the other wireless communication device exceeds a first value, and then the estimated other wireless communication 2. The wireless communication apparatus according to claim 1, wherein when the moving speed of the apparatus becomes equal to or less than a second value, the operation of the adaptive modulation unit is resumed. Based on a signal received from the other wireless communication device, further comprises a fluctuation period measurement unit that measures the fluctuation period of the received wave,
2. The setting period control unit controls the adaptive modulation unit to set an adaptive modulation parameter at a period of n times (n is a natural number) of the measured fluctuation period of the received wave. The wireless communication device described. Based on a signal received from the other wireless communication device, further comprises a fluctuation period measurement unit that measures the fluctuation period of the received wave,
The setting period control unit controls the adaptive modulation unit to set an adaptive modulation parameter at a frame period closest to n times (n is a natural number) of the measured fluctuation period of the received wave. The wireless communication apparatus according to claim 1. A base station apparatus that adaptively changes a modulation scheme according to a propagation path state,
A base station apparatus comprising the wireless communication apparatus according to claim 1. A mobile station apparatus that adaptively changes a modulation scheme according to a propagation path state,
A propagation path estimation unit that estimates a propagation path based on a signal received from the base station apparatus according to claim 7 and outputs propagation path estimation information;
A speed detection unit that detects the moving speed of the local station and outputs speed information;
A mobile station apparatus that transmits the propagation path estimation information and the speed information to the base station apparatus. The speed detector
A GPS signal receiver for receiving GPS signals;
9. The mobile station apparatus according to claim 8, wherein a moving speed of the own station is detected based on the received GPS signal. A wireless communication system that adaptively changes a modulation scheme according to a propagation path state,
A base station apparatus according to claim 7;
A wireless communication system comprising: the mobile station apparatus according to claim 8 or 9. A wireless communication method that adaptively changes a modulation scheme according to the state of a propagation path,
Setting adaptive modulation parameters based on propagation path information received from another wireless communication device that is a communication partner;
Based on a signal received from the other wireless communication device, estimating a moving speed of the other wireless communication device and outputting speed estimation information;
And a step of controlling a period at which the adaptive modulation section sets an adaptive modulation parameter based on the speed estimation information.

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