JP2011071765A - Master station and method of communication control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform time slot allocation so that reception completion timing and transmission start timing are not changed in all slave stations by a master station in a communication system. <P>SOLUTION: The master station in the communication system for performing transmission and reception to/from a plurality of slave stations includes: a slot allocating means for allocating an outgoing slot and an incoming slot used to transmit and receive data to/from each of the plurality of slave stations to a transmission frame which has a fixed frame length and is transmitted and received in each fixed period, that is, a preset position of the transmission frame; a spare slot allocating means for allocating a spare outgoing slot and a spare incoming slot at a position different from the outgoing slot and the incoming slot of the transmission frame; and a transmitting means for transmitting and receiving information by the transmission frame allocated by the slot allocating means in each fixed period and transmitting and receiving additional information by the spare outgoing slot and the spare incoming slot in the case of transmitting and receiving the additional information in addition to the information. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a master station that determines time slot allocation of a transmission frame when performing periodic communication with a plurality of slave stations using the TDMA / TDD communication method, and communication between the master station and the slave stations. It relates to a control method.

  There is a TDMA / TDD communication method as an effective communication method when the master station communicates with a plurality of slave stations using one transmission path. In general, in the TDMA / TDD communication system, a transmission frame is divided into a downlink slot and an uplink slot. In the downlink slot, the master station transmits data to each slave station, and each slave station transmits data to the master station in the uplink slot. Send. In a frame with a small amount of data to be transmitted, the master station arranges an empty slot in the downlink or uplink slot so that the transmission frame length does not change.

  Japanese Patent Application Laid-Open No. H10-228707 discloses a means for collecting empty slots in a frame in a continuous time domain. Also, in Patent Document 2, the boundary between the downlink slot and the uplink slot is made variable so that an empty slot in the downlink slot and an empty slot in the uplink slot can be used for both downlink and uplink applications. Means are disclosed.

JP 2001-333038 A Japanese Patent Application Laid-Open No. 07-297829

  In the prior art, when the number of slots used in communication for a certain slave station changes, the position of the communication slot for another slave station changes in the transmission frame. That is, when the size of data transmitted from the master station to some slave stations temporarily increases, the timing at which other slave stations receive data from the master station changes. Therefore, for example, when each slave station needs to receive control data from the master station at a constant cycle as in a motor control system, if the size of control data for a certain slave station becomes larger than normal, the data of other slave stations Since there was a delay in the reception, there was a risk that accurate control could not be performed.

  Furthermore, in the case where each slave station in the system returns a result of processing based on the received data after receiving control data from the master station, each slave station returns from the completion of reception to the start of transmission. A certain processing time is required during the period. At this time, if the slave station's reception completion or transmission start timing changes due to the change of the slot position, this processing time cannot be secured, and a response cannot be returned in the upstream slot in the same transmission frame. It was.

  In view of the above problems, an object of the present invention is to provide a master station that performs time slot allocation so that reception completion timing and transmission start timing do not change in all slave stations.

  A downlink station used for transmission / reception of data to / from each of the plurality of slave stations in a transmission frame having a fixed frame length and transmitted / received at regular intervals in a communication system that transmits / receives to / from a plurality of slave stations Slot allocating means for allocating slots and uplink slots to preset positions of the transmission frame, and spare downlink slots and spare uplink slots at positions different from the downlink slots and uplink slots of the transmission frame. A spare slot allocating unit for allocating the information, and transmitting and receiving information by the transmission frame allocated by the slot allocating unit at regular intervals, and transmitting and receiving additional information in addition to the information. Transmission means for transmitting and receiving the additional information by a slot for use.

  When the present invention is applied, the reception completion timing and transmission start timing do not change in all the slave stations. Thereby, the constantness of the control cycle is maintained and accurate control can be performed.

A system connection diagram of robot control using communication between a master station and a slave station. Functional block diagram of a master station and a slave station. The slot allocation figure when not using a spare slot. The slot allocation figure in the case of using a spare slot. The figure showing the priority table of a slave station. Diagram showing spare slot allocation request table The figure showing the reserve slot allocation procedure. Functional block diagram of a master station and a slave station. The figure showing the internal format of control information and feedback information. The slot allocation figure allocated to two substations. The figure showing the modulation system of control information and feedback information. The functional block diagram of the transmission part and reception part corresponding to a some modulation system. The figure showing a modulation system table.

<Embodiment 1>
A communication system that controls communication of a robot to which the present invention is applied will be described. FIG. 1 is a connection diagram of a robot control communication system to which the present invention is applied.

  The master station 100 transmits individual control information for operating the arm 104 of each slave station to each of the slave stations 101 to 103 for each control frame of 1 ms. The slave stations 101 to 103 control the arm 104 based on the control information received from the master station 100 and transmit feedback information to the master station 100.

  The robot arm 104 is controlled by the slave stations 101 to 103 and acts on the object 105. The object 105 is a target on which the arm 104 acts. In this system, the master station 100 performs control such that a plurality of arms 104 connected to the slave stations 101 to 103 cooperate with each other to act on the object 105.

  As an example of such control, there is control such that the object 105 is lifted by a hand (not shown) attached to the tip of the arm 104 and moved to a predetermined position. When the master station 100 transmits control information to the slave stations 101 to 103, the slave stations 101 to 103 perform processing based on the control information and return feedback information to the master station 100.

  Based on this feedback information, master station 100 corrects the control information in the next control frame. By repeating such exchange of control information at a control cycle of 1 ms, the cooperative operation of the arm 104 is performed.

  FIG. 9 is a diagram illustrating an internal format of control information and feedback information exchanged between the master station 100 and the slave stations 101 to 103. The master station 100 and the slave stations 101 to 103 exchange control information and feedback information in either the control information format 900 or the control information format 901.

  In the control information format 900, the master station 100 transmits torque control information that is a force with which the arm 104 presses the object 105. The slave station that has received the control information in the control information format 900 obtains a predicted pressure after 1 ms of the pressure applied between the arm 104 and the object 105 by calculation, and returns it to the master station 100 as feedback information.

  In the control information format 901, the master station 100 transmits torque control information that is a force by which the arm 104 presses the object 105 and angle control information for adjusting the angle of the arm 104. The slave station that has received the control information in the control information format 901 combines the angle control information received from the master station 100 for confirmation in addition to the predicted pressure, and returns it to the master station 100 as feedback information.

  Since the master station 100 and the slave stations 101 to 103 communicate with each other by the TDMA / TDD system, control information and feedback information are each transmitted using a fixed number of time slots. Here, the number of slots required for communication in the control information format 900 is one slot as control information and one slot as feedback information.

  When communication is performed in the control information format 901, three slots are required as control information and three slots as feedback information. In order to efficiently use the transmission band, the master station 100 normally transmits control information in the control information format 900, and transmits control information in the control information format 901 only when the angle of the arm 104 needs to be adjusted. .

  Next, the configuration of the master station 100 and the slave stations 101 to 103 in this system will be described. FIG. 2 is a diagram illustrating the configuration of the master station 100 and the slave station 101. The slave stations 102 and 103 have the same configuration as that of the slave station 101 although not shown.

  The torque control information generation unit 200 has a constant frame length, generates torque control information for controlling the torque of the motor 220 in the arm 104 of each of the slave stations 101 to 103 at a constant period of 1 ms, and transmits the transmission unit. To 205. The torque control information is corrected based on the feedback information received from the slave stations 101 to 103 last time.

  When the angle control information generating unit 201 analyzes the feedback information received last time and determines that it is necessary to change the angle of the motor 220 of a certain slave station, the angle control information generating unit 201 requests the spare slot allocating unit 202 to allocate a spare slot. If a notification of successful slot assignment is obtained, angle control information for the motor 220 is generated and transmitted to the transmission unit 205.

  When the spare slot allocation unit 202 receives a slot allocation request, the spare slot allocation unit 202 allocates an empty slot in the spare downlink slot and an empty slot in the spare uplink slot according to the request. If there are not enough empty slots for the requested number of slots, a spare slot allocation request for a slave station with a high priority is preferentially allocated according to the information stored in the priority storage unit 203. The success or failure of the assignment is returned to the request source, that is, the angle control information generation unit 201 in the case of the present embodiment. The procedure of the above operation is shown in FIG. 7, and details will be described later.

  The priority storage unit 203 holds a priority table having a format as shown in FIG. The priority table 500 holds an identifier of each slave station and priority information. The priority values 1, 2, and 3 are assumed to be lower in priority.

  The slot allocation unit 204 sets the transmission frame to 1 ms which is the same as the control period, allocates the communication slots performed by the master station 100 and the slave stations 101 to 103 in one transmission frame as shown in FIG. Is transmitted to the transmission unit 205. Details of FIG. 3 and allocation will be described later.

  When only the torque control information generated by the torque control information is received, the transmission unit 205 of the master station 100 generates and holds control information for each slave station in the control information format 900. When the angle control information generated by the angle control information generation unit 201 is also received, control information for each slave station is generated and held in the control information format 901. Further, the transmission unit 205 receives the slot allocation information from the slot allocation unit 204 and the spare slot allocation unit 202 and holds it. Then, the transmission unit 205 transmits the held data to the transmission path at a timing based on the synchronization signal input from the synchronization signal generation unit 207 and the slot assignment information.

  The receiving unit 206 of the master station 100 demodulates a signal transmitted from the slave stations 101 to 103 to the master station 100 and sends the demodulated signal to the torque control information generation unit 200 and the angle control information generation unit 201.

  The synchronization signal generation unit 207 of the master station 100 generates a signal for the master station 100 and the slave stations 101 to 103 to synchronize slots and sends the signal to the transmission unit 205. The motor control unit 210 of the slave station 101 is based on the control information received from the master station 100, that is, the control information generated by the torque control information generation unit 200 and the angle control information generation unit 201 of the master station 100. The motor 220 of the arm 104 is controlled.

  The computing unit 211 of the slave station 101 obtains a predicted pressure value after 1 ms based on the current pressure information between the arm 104 and the object 105 acquired from the pressure sensor 221 and the control information received from the master station 100. Then, it is transmitted to the transmission unit 213 as feedback information. In addition, when angle information is included in the received control information, the calculation unit 211 includes the angle control information in feedback information for confirmation. The calculation unit 211 requires calculation time for two slots until it receives control information and transmits feedback information.

  The receiving unit 212 of the slave station 101 extracts control information addressed to itself from the signal on the transmission path, and sends it to the motor control unit 210 and the calculation unit 211.

  The transmission unit 213 of the slave station 101 transmits the feedback information received from the calculation unit 211 to the transmission path at a timing based on an instruction from the slot control unit 214.

  The slot control unit 214 of the slave station 101 extracts the slot synchronization signal and the slot allocation information from the signal received by the reception unit 212, and controls the transmission unit 213 to transmit the slot allocation instructed by the master station 100. To do. For example, the slot control unit 214 performs control so that the transmission unit 213 transmits data in the slot allocated for the slave station 101 in the uplink slot and the backup uplink slot.

  The motor 220 of the robot arm 104 generates the torque designated by the motor control unit 210 at the angle designated by the motor control unit 210. The pressure sensor 221 of the arm 104 measures the pressure applied between the arm 104 and the object 105 and transmits it to the calculation unit 211 of the slave station 101.

  Here, a slot allocation method by the slot allocation unit 204 of the master station 100 will be described. FIG. 3 is a diagram illustrating slot allocation by the slot allocation unit 204. As shown in the figure, spare downlink slots and spare uplink slots are arranged at positions other than downlink slots and uplink slots arranged at fixed positions for constant use.

  The slot allocation unit 204 arranges the notification slot 300 at the head of the frame. In the notification slot 300, slot assignment information and a slot synchronization signal are broadcast from the master station 100 to the slave stations 101-103. The slot allocation unit 204 allocates one slot to the notification slot 300.

  The slot allocation unit 204 arranges the spare downlink slot 301 in front of the downlink slot 302 and allocates two slots to the spare downlink slot 301. The slot allocation unit 204 arranges the downlink slot 302 in front of the uplink slot 303, and transmits the control information transmitted from the master station 100 to the slave stations 101 to 103 in each slot in the downlink slot 302 for each slave station. A total of 3 slots are assigned to each slot.

  The slot allocation unit 204 arranges the upstream slot 303 behind the downstream slot 302. Further, the slot allocation unit 204 allocates a total of 3 slots to each slot in the uplink slot 303, one slot for each slave station for transmission of feedback information transmitted from the slave stations 101 to 103 to the master station 100.

  The slot allocation unit 204 arranges the spare uplink slot 304 behind the uplink slot 303. The slot allocation unit 204 allocates two slots to the spare uplink slot 304.

  Control information addressed from the master station 100 to the slave station 101 is transmitted using the downlink slot 310 for the slave station 101. Further, feedback information addressed from the slave station 101 to the master station 100 is transmitted using the uplink slot 311 for the slave station 101.

  The slot allocation unit 204 allocates each slot in the downlink slot 302 in the order of the slave station 101, the slave station 102, and the slave station 103 as shown in FIG. Similarly, each slot in the upstream slot 303 is assigned in the order of the slave station 101, the slave station 102, and the slave station 103. By assigning in this way, two slots are secured for the slave station 101 to perform operations between the downlink slot 310 for the slave station 101 and the uplink slot 311 for the slave station 101. Similar slot allocation is performed for the slave station 102 and the slave station 103.

  Here, an operation when the master station 100 and the slave stations 101 to 103 communicate in the control information format 900 will be described. In the control information format 900, control information transmitted from the master station 100 to the slave station 101 and feedback information transmitted from each slave station to the master station 100 can be transmitted in one slot.

  Therefore, when the master station 100 and the slave stations 101 to 103 communicate in the control information format 900, all the control information addressed to the slave station 101 is transmitted in the slot 310 of FIG. Similarly, all feedback information from the slave station 101 is transmitted in the slot 311. Since the same applies to the slave stations 102 and 103, the slot allocation is as shown in FIG. At this time, each of the slave stations 101 to 103 has a processing time of two slots from the completion of reception to the start of transmission. Therefore, the master station 100 and the slave stations 101 to 103 can exchange control information and feedback information in the control information format 900 every control cycle of 1 ms using the downlink slot 302 and the uplink slot 303.

  Next, an operation when the master station 100 and some slave stations communicate in the control information format 901 will be described. First, feedback information from the slave station is analyzed in the master station, and as a result, it is determined that it is necessary to transmit information for angle control in addition to the torque control information. The situation where communication is performed in the control information format 901 occurs when the angle control information generation unit 201 for the angle control generates angle control information. Here, an operation when the angle control information generation unit 201 generates angle control information for the slave station 101 and the slave station 102 will be described as an example.

  First, the angle control information generation unit 201 issues a spare slot allocation request for the slave station 101 and the slave station 102 to the spare slot allocation unit 202. The spare slot allocation unit 202 receives three parameters for each request (slave station identifier, downlink request spare slot number, uplink request spare slot number).

  Here, in the control information format 901, three slots are required to transmit control information and feedback information, but only one slot is assigned to each slave station in the downlink and uplink slots. Therefore, the number of downlink request spare slots and the number of uplink request spare slots requested by the angle control information generation unit 201 to send additional angle information are two for each of the slave station 101 and the slave station 102. The identifiers of the slave stations are determined in advance when the master station 100 and each slave station are connected. Now, the identifiers of the slave stations 101, 102, and 103 are 101, 102, and 103, respectively. Suppose there is. The spare slot allocation request issued by the angle control information generation unit 201 includes (slave station identifier: 101, downlink request spare slot number: 2, uplink request spare slot number: 2) and (slave station identifier: 102, downlink request). The number of requested spare slots is 2, and the number of requested spare slots for uplink is 2).

  FIG. 6 is a diagram illustrating a configuration of a request table for holding a spare slot assignment request in the spare slot assignment unit 202. The spare slot allocation unit 202 holds the received request in the request table 600. The request table 600 has a format that can store, for each request, three parameters: a slave station identifier, the number of downlink request spare slots, and the number of downlink request spare slots. Furthermore, the request table 600 holds a processed flag and an assignment enable / disable flag for each request as work parameters for priority assignment processing. The spare slot allocation unit 202 sets the processed flag and the allocation enable / disable flag to FALSE when the request is received.

  When all the requests for one frame are received, the spare slot assigning unit 202 determines the priority order of the requests and assigns spare slots in order. FIG. 7 is a diagram illustrating a spare slot assignment procedure in the spare slot assignment unit 202.

  In step S1, the spare slot allocation unit 202 refers to the request table 600 and checks whether there is an unprocessed request. Here, there are requests for the slave station 101 and the slave station 102, both of which are still unprocessed, the process proceeds to step S2.

  In step S <b> 2, the spare slot allocation unit 202 refers to the priority table 500, and sets the highest priority among the slave stations having unprocessed requests as allocation candidates. In the priority table 500, since the slave station 102 and the slave station 102 have high priority, the slave station 102 becomes an assignment candidate, and the process proceeds to step S3.

  In step S3, the spare slot allocation unit 202 determines whether or not the number of slots necessary for communication with the slave station 102 that has become an allocation candidate falls in an empty slot in the spare downlink slot 301 and the spare uplink slot 304. To check. Here, according to the request table 600, the number of slots required for the slave station 102 is two for the reserved downlink slot 301 and two for the reserved uplink slot 304. Since no spare slot has yet been assigned to other slave stations, there are two free slots in the spare downlink slot 301 and the spare uplink slot 304 as shown in FIG. Therefore, it is determined that there are enough empty slots, and the process proceeds to step S4.

  In step S <b> 4, the spare slot assigning unit 202 assigns the slot for the slave station 102 that has been an assignment candidate to the spare downlink slot 301 and the spare uplink slot 304. Then, the allocation propriety flag of the slave station that has been an allocation candidate is set to TRUE, and the process proceeds to step S5.

  In step S5, the spare slot allocation unit 202 sets the processed flag to TRUE for the slave station 102 in the request table 600, and returns to step S1.

  In step S1, since the processed flag of the slave station 101 in the request table 600 is still FALSE, the process proceeds to step S2.

  In step S2, since only the slave station 101 has the processed flag in the request table 600 set to FALSE, the allocation candidate is set as the slave station 101 and the process proceeds to step S3.

  In step S3, two empty slots respectively in the spare downlink slot and the spare uplink slot are allotted to the slot for the slave station 102 in step S4 and no longer remain. Therefore, the spare slot for the slave station 101 is not allocated and the process proceeds to step S5.

  In step S5, the processed flag of the slave station 101 in the request table 600 is TRUE, and the process returns to step S1.

  In step S1, since there is no child station whose processed flag in the request table 600 is FALSE, the process proceeds to step S6.

  In step S6, the request table 600 is initialized after the contents of the allocation permission flag for each request are returned to the request source, and the spare slot allocation process for one frame is completed.

  According to the above procedure, two slots are allocated to the spare downlink slot and the spare uplink slot for communication with the slave station 102, respectively. FIG. 4 is a diagram showing slot assignment at this time.

  Slots 402 and 400 in FIG. 4 are allocated for communication with the slave station 102. The angle control information generation unit 201 is notified from the spare slot allocation unit 202 that a spare slot for communication with the child station 102 has been secured, and therefore generates angle control information for the child station 102 in the next frame. To the transmission unit 205. Note that the angle control information for the slave station 101 is generated again when a spare slot allocation request is made again after the next frame and a slot is secured.

  The transmitting unit 205 of the master station 100 combines the received angle control information for the slave station 102 with the torque control information for the slave station 102 to generate control information in the control information format 901, and the slot 402 in FIG. And the slot 400 are used to transmit control information for the slave station 102. From FIG. 4, it can be seen that each of the slave stations 101 to 103 has a processing time of two slots from the completion of reception to the start of transmission.

  In FIG. 4, the slave station 102 completes the reception of the control information when the reception of the slot 400 is completed. This is the case for slot number 4. The slave station 102 starts transmitting feedback information at the start of transmission of the slot 401 in FIG. This is the case for slot number 7.

  On the other hand, when the slave station 102 and the master station 100 communicate in the control information format 900, the slot assignment as shown in FIG. Even in this case, the slave station 102 completes the reception of the control information when the slot number is 4, and the slave station 102 starts transmitting the feedback information when the slot number is 7.

  That is, the slave station 102 always completes reception of control information in the same slot and transmits feedback information in the same slot, even when communicating with the master station 100 in either the control information format 900 or the control information format 901. Start.

  3 and 4, similarly for the slave stations 101 and 103, when the slave station 102 and the master station 100 communicate in either the control information format 900 or 901, control information is always received in the same slot. It can be seen that the transmission of feedback information is started in the same slot.

  When viewed from each slave station, it is possible to obtain all control information accurately every 1 ms regardless of the presence or absence of angle information in the control information of the local station or other slave stations, and feedback is always performed at the same timing. Information can be returned.

  As a result, in a system in which the master station and the slave station exchange control information and feedback information at a constant cycle, even when the size of the control information and the feedback information changes, the control cycle is constant. The accuracy of the control can be increased. Further, since the angle information is not transmitted every time, the transmission band can be used effectively.

  In the first embodiment, the angle control information received by the slave station is included in the feedback information in the control information format 901. However, if the received angle control information is not included in the feedback information of the control information format 901, the slot allocation unit 204 does not have to allocate the spare uplink slot 304. An example of such slot allocation is shown in FIG. Even in this case, since the reception completion timing and transmission start timing of each slave station are also kept constant, in the system in which the master station and the slave station exchange control information and feedback information at a constant cycle, The same effect can be obtained.

<Embodiment 2>
In the second embodiment, parts different from the contents described in the first embodiment will be described. FIG. 11 is a diagram illustrating a modulation scheme used for communication between the master station 100 and the slave stations 101 to 103 in the second embodiment. In the second embodiment, in order to reliably transmit data to a slave station whose transmission path is deteriorated, information is redundantly transmitted using a spare slot, and the modulation method is less likely to cause data errors. Switch to method.

  Communication between the master station 100 and the slave stations 101 to 103 is performed using either the first modulation scheme 1100 or the second modulation scheme 1101. The difference between the first modulation scheme 1100 and the second modulation scheme 1101 is only that the multi-value number is different. In general, if the multi-value number of the modulation scheme is reduced, transmission errors are less likely to occur, but the number of slots required for transmission / reception increases. The number of slots required for communication in the first modulation scheme 1100 is one slot each for control information and feedback information, whereas in the second modulation scheme 1101 there are three slots each. For example, the master station 100 and the slave stations 101 to 103 normally communicate using the first modulation scheme 1100 of 64QAM, and the QPSK second modulation scheme 1101 is used only when the state of the transmission path deteriorates, that is, when interference increases. Communicate.

  FIG. 8 is a diagram illustrating functional blocks of a master station and a slave station according to the second embodiment of the present invention. Hereinafter, functional blocks different from the blocks described in FIG. 2 of the first embodiment will be described.

  The transmission path quality monitoring unit 800 of the master station 100 inspects the quality information of the transmission path in the master station 100 and generated by the transmission path quality information generation unit 810 of the slave stations 101 to 103. When it is detected that the quality information value is equal to or lower than the predetermined threshold value and the quality of the transmission paths of some of the slave stations is deteriorated, the slave station identifier is notified to the modulation scheme determining unit 801. The value of the quality information of the transmission path here means, for example, the reception level of the transmission signal from the master station in each slave station.

  When the modulation scheme determining unit 801 of the master station 100 is notified by the transmission channel quality monitoring unit 800 that the quality information of the transmission channels with some of the slave stations has deteriorated, the spare slot allocation unit 202 is notified. Request allocation of spare slots. When the notification of successful slot allocation is obtained, the modulation scheme determining unit 801 communicates with the second modulation scheme 1101 in the communication slot for the slave station that has been notified of the transmission path deterioration in the next frame. Information is stored in the modulation scheme storage unit 804.

  The transmission unit 802 of the master station 100 is obtained by adding a function of performing modulation using the modulation method instructed from the modulation method storage unit 804 to the transmission unit 205 of FIG. The transmission unit 802 has a function of transmitting information indicating which modulation method is used for transmission in the broadcast slot 300 during transmission.

  The reception unit 803 of the master station 100 is obtained by adding a function of demodulating with a demodulation method corresponding to the modulation method instructed from the modulation method storage unit 804 to the reception unit 206 of FIG. The modulation method storage unit 804 of the master station 100 has a modulation method table 1300 as shown in FIG. 13 and holds the modulation method of communication with each slave station determined by the modulation method determination unit 801. Note that a slave station that is not particularly notified by the modulation scheme determination unit holds the modulation scheme as 1100.

  Also, the modulation scheme storage unit 804 of the master station 100 determines the timing for switching the modulation scheme from the slot allocation information output by the slot allocation unit 204 and the synchronization signal generated by the synchronization signal generation unit 207. To do. Then, modulation scheme information is output to the transmission unit 802 and the reception unit 803 at a timing such that the modulation scheme in communication with each slave station matches the content held in the modulation scheme table 1300.

  The transmission path quality information generation unit 810 is in the slave stations 101 to 103, acquires the bit error rate of the received data in the reception unit 212, combines it with the feedback information as transmission path quality information, and transmits it to the transmission unit 213. To do.

  The modulation scheme control unit 811 of the slave stations 101 to 103 extracts information on the modulation scheme of the own station from the information transmitted by the master station 100 and transmits the modulation scheme to the reception unit 812 and the transmission unit 813. The receiving units 812 of the slave stations 101 to 103 are obtained by adding a function of demodulating in the demodulation method corresponding to the modulation method notified from the modulation method control unit 811 to the receiving unit 212 of FIG. Further, the transmission units 813 of the slave stations 101 to 103 are obtained by adding a function of performing modulation using the modulation scheme notified from the modulation scheme control unit 811 to the transmission unit 213 of FIG.

  12 shows the internal configuration of the transmitter 802 of the master station 100 and the modulator of the transmitter 813 of the slave stations 101 to 103, and the demodulator of the receiver 803 of the master station 100 and the receiver 812 of the slave stations 101 to 103. FIG.

  The modulation scheme switching unit 1200 of the master station 100 controls the switch 1201 according to the instructed modulation scheme. The switch 1201 is controlled by the modulation scheme switching unit 1200, and enables the modulation processing of either the 64QAM modulation unit 1202 or the QPSK modulation unit 1203.

  The 64QAM modulation unit 1202 of the master station 100 performs 64QAM modulation on the input data and outputs it to the transmission line. The QPSK modulator 1203 performs QPSK modulation on the input data and outputs the result to the transmission path. Then, the transmission buffer 1204 sends the held data to the modulation unit based on the slot allocation information.

  The demodulation method switching unit 1210 of the slave stations 101 to 103 controls the switch 1211 according to the demodulation method corresponding to the instructed modulation method. The switch 1211 is controlled by the demodulation method switching unit 1210, and enables the demodulation process of either the 64QAM demodulation unit 1212 or the QPSK demodulation unit 1213.

  The 64QAM demodulation unit 1212 of the slave stations 101 to 103 demodulates the input signal by 64QAM and outputs it. The QPSK demodulator 1213 performs QPSK modulation on the input signal and outputs it.

  With the above configuration, the transmission unit 802 of the master station 100 and the transmission unit 813 of the slave stations 101 to 103, the reception unit 803 of the master station 100, and the reception unit 812 of the slave stations 101 to 103 switch a plurality of modulation schemes. Can do.

  Here, an operation in the case where the master station 100 and the slave stations 101 to 103 communicate using the first modulation scheme 1100 will be described. In the first modulation scheme 1100, control information transmitted from the master station 100 to the slave station 101 and feedback information transmitted from each slave station to the master station 100 can be transmitted in one slot. Therefore, when the master station 100 and the slave stations 101 to 103 communicate with each other using the first modulation scheme 1100, all control information addressed to the slave station 101 is transmitted in the slot 310 of FIG. Similarly, all feedback information from the slave station 101 is transmitted in the slot 311. Since the same applies to the slave stations 102 and 103, the slot assignment is as shown in FIG. At this time, each of the slave stations 101 to 103 has a processing time of two slots from the completion of reception to the start of transmission. Therefore, the master station 100 and the slave stations 101 to 103 can exchange control information and feedback information using the first modulation scheme 1100 for each control period of 1 ms using the downlink slot 302 and the uplink slot 303.

  Next, the operation when the master station 100 and some slave stations communicate using the second modulation scheme 1101 will be described. The situation in which communication is performed using the second modulation scheme 1101 occurs when the transmission path quality monitoring unit 800 of the master station 100 detects deterioration of the transmission path condition with some slave stations. Here, a case where the transmission path state between the master station 100 and the slave station 101 and between the master station 100 and the slave station 102 deteriorates will be described as an example.

  First, in the transmission path quality monitoring unit 800 of the master station 100, the master station 100 and the slave station 102 and the master station 100 and the slave station are determined from the transmission path quality information generated by the transmission path quality information generation unit 810 of the slave stations 101 and 102. It is detected that the quality of the transmission path to the station 102 has deteriorated. Then, the information is transmitted to the modulation scheme determining unit 801. The modulation scheme determining unit 801 of the master station 100 issues a spare slot allocation request for the slave station 101 and the slave station 102 to the spare slot allocation unit 202.

  Here, in the second modulation scheme 1101, three slots are required for transmission of control information and feedback information, but only one slot is allocated to each of the slave stations in the downlink and uplink slots. Accordingly, the number of downlink request spare slots and the number of uplink request spare slots requested by the modulation scheme determining unit 801 are two for each of the slave station 101 and the slave station 102.

  The parameters received by the spare slot allocation unit 202 of the master station 100 are three for each request (slave station identifier, downlink request spare slot number, uplink request spare slot number). Therefore, the spare slot allocation request issued by the modulation scheme determining unit 801 of the master station 100 includes (slave station identifier: 101, downlink request spare slot number: 2, uplink request spare slot number: 2) and (slave station identifier). : 102, downlink request spare slot number: 2, uplink request spare slot number: 2).

  As a result, two slots are allocated to each of the spare downlink slot and the spare uplink slot for communication with the slave station 102, resulting in slot allocation as shown in FIG. The process of slot assignment is the same as that in the first embodiment when the angle control information generation unit 201 of the master station 100 generates angle control information for the slave station 101 and the slave station 102. Omitted.

  The modulation scheme determining unit 801 of the master station 100 is notified from the spare slot allocating unit 202 that a spare slot for communication with the slave station 102 has been secured. Therefore, in the next frame, for modulation with the slave station 102 Information for setting the second modulation scheme 1101 to be the second modulation scheme 1101 is stored in the modulation scheme storage unit 804.

  As a result, the modulation scheme table 1300 stored in the modulation scheme storage unit 804 of the master station 100 has the contents shown in FIG. The modulation scheme storage unit 804 instructs the transmission unit 802 and the reception unit 803 to perform modulation / demodulation using the second modulation scheme 1101 at the timing of the communication slot with the slave station 102.

  When an instruction to change the modulation method to the second modulation method 1101 is input to the transmission unit 802, the modulation method switching unit 1200 in FIG. 12 controls the switch 1201 so that the modulation path by the QPSK modulation unit 1203 becomes valid. To.

  When an instruction to change the modulation method to the second modulation method 1101 is input to the reception unit 803, the demodulation method switching unit 1210 in FIG. 12 controls the switch 1211 so that the demodulation path by the QPSK demodulation unit 1213 becomes valid. To.

  With the above operation, the master station 100 and the slave station 102 communicate using the second modulation scheme 1101. At this time, control information from the master station 100 to the slave station 102 is transmitted in the slot 402 and the slot 400 of FIG. Feedback information from the slave station 102 to the master station 100 is transmitted in the slots 401 and 403 in FIG. On the other hand, communication with the slave station 101 and the slave station 103 is performed by the first modulation method 1100.

  From FIG. 4, it can be seen that each of the slave stations 101 to 103 has a processing time of two slots from the completion of reception to the start of transmission. In FIG. 4, the slave station 102 completes the reception of the control information when the reception of the slot 400 is completed. This is the case for slot number 4. The slave station 102 starts transmitting feedback information at the start of transmission of the slot 401 in FIG. This is the case for slot number 7.

  On the other hand, when the slave station 102 and the master station 100 communicate with each other by the second modulation method 1101, the slot assignment as shown in FIG. Even in this case, the slave station 102 completes the reception of the control information when the slot number is 4, and the slave station 102 starts transmitting the feedback information when the slot number is 7.

  That is, the slave station 102 always completes reception of control information in the same slot and communicates feedback information in the same slot when communicating with the master station 100 using either the first modulation scheme 1100 or the second modulation scheme 1101. Start sending. 3 and 4, similarly, the slave station 101 and the slave station 103 are always in the same slot regardless of whether the slave station 102 and the master station 100 are the first modulation scheme 1100 or the second modulation scheme 1101. It can be seen that the reception of the control information is completed and the transmission of feedback information is started in the same slot.

  When viewed from each slave station, all control information is obtained accurately every 1 ms regardless of whether the modulation scheme of the local station or other slave stations is the first modulation scheme 1100 or the second modulation scheme 1101. And feedback information can always be returned at the same timing. As a result, in a system in which the master station and the slave station exchange control information and feedback information at a constant cycle, even when the size of the control information and the feedback information changes, the control cycle is constant. The accuracy of the control can be increased. Further, since the modulation method can be changed depending on the state of the transmission path, the reliability of the system can be improved.

  In the second embodiment, the modulation scheme is switched. However, the encoding scheme may be switched instead of the modulation scheme. In this case, it is possible to improve the reliability of the system by changing the encoding system according to the state of the transmission path without changing the transmission / reception timing in each slave station.

Claims (5)

A master station in a communication system that transmits / receives to / from a plurality of slave stations,
A transmission frame having a certain frame length and transmitted / received at regular intervals has a downlink slot and an uplink slot used for transmitting / receiving data to / from each of the plurality of slave stations set in advance in the transmission frame. Slot assignment means for assigning to the position;
Spare slot allocating means for allocating a spare downlink slot and a spare uplink slot at a position different from the downlink slot and the uplink slot in the transmission frame;
Information is transmitted and received by the transmission frame allocated by the slot allocation unit at regular intervals, and when the additional information is transmitted and received in addition to the information, the additional information is transmitted and received by the spare downlink slot and the spare uplink slot. And a transmission means. And a priority storage means for storing priorities of the plurality of slave stations,
The transmission means transmits the additional information using the spare downlink slot and the spare uplink slot in order from a slave station having a higher priority according to the stored priority. 1. The master station described in 1. Further, the transmission means includes
Receiving a reception level of a signal transmitted by the master station from each of the plurality of slave stations;
Sending and receiving the information by a first modulation scheme to a slave station having a reception level higher than a predetermined threshold,
2. The master station according to claim 1, wherein the information and the additional information are transmitted and received by a second modulation method to a slave station having the reception level equal to or less than the predetermined threshold. The master station according to claim 3, wherein the additional information is redundant information of the information. In a communication system comprising a master station and a plurality of slave stations, a communication control method between the master station and the plurality of slave stations,
The slot allocating means assigns a downlink slot and an uplink slot to be used for transmission / reception of data to / from each of the plurality of slave stations to a transmission frame having a constant frame length and transmitted / received at regular intervals. A slot assignment step to assign to a fixed position of
A spare slot allocating unit allocates a spare downlink slot and a spare uplink slot to a position different from the downlink slot and the uplink slot in the transmission frame, and A transmission step of transmitting and receiving additional information through the reserved downlink slot and the reserved uplink slot when information is transmitted / received by the transmission frame allocated by the slot allocation unit and additional information is transmitted / received in addition to the information. A method characterized by.

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