Wireless communication system, method for controlling a wireless communication system, and control program for a wireless communication system

Abstract

To provide a radio communication system capable of receiving audio data without trouble even if a radio base station is switched.SOLUTION: Each radio base station includes a ring buffer provided correspondingly to each radio terminal including a first radio terminal which is connected to the own station and a second radio terminal which is not connected to the own station, and comprises a buffer management section by which audio data included in a received audio packet are written in a region designated by a write index in the ring buffer provided correspondingly to the radio terminal of a destination to transmit the audio data and audio data written in a region designated by a read index in the ring buffer provided correspondingly to the first radio terminal are read out.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a wireless communication system, a control method for the wireless communication system, and a control program for the wireless communication system.

Background Art

[0002] As described in Patent Document 1, a wireless communication system called an intercom system is used in stores and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, it is conceivable to construct a wireless communication system using a communication standard for wireless LAN (IEEE802.11, etc.). In a wireless communication system that performs data communication using a predetermined communication standard not limited to wireless LAN, even if the wireless base station that is the connection destination of the wireless terminal is switched, it is required to be able to receive voice data without problems.

[0005] An object of the present invention is to provide a wireless communication system that can receive voice data without problems even when the wireless base station that is the connection destination of the wireless terminal is switched.

Means for Solving the Problems

[0006] A wireless communication system according to one aspect of the present invention includes a center device and a plurality of devices connected to the center device. ​​​​​​A number of radio base stations, and one or more radio base stations that are wirelessly connected to each radio base station in multiple radio base stations The center device is equipped with wireless terminals and other devices, and transmits voice data to the destination of the voice data. Includes multiple pairs of sequence numbers indicating the order of audio data transmitted to each wireless terminal. The voice packet is sent to all of the multiple radio base stations, and each radio base station is connected to its own station. Each wireless terminal, including the first wireless terminal and the second wireless terminal not connected to the station, is supported. It has a ring buffer provided for this purpose, and the audio data contained in the received audio packet The data is provided in a ring buffer corresponding to the destination wireless terminal to which the voice data is transmitted. Write to the area specified by the write index, and provided in accordance with the first wireless terminal. Audio data written to the area specified by the read index of the ring buffer. It has a buffer management unit that reads out the data.

[0007] Wireless communication, where the operation of a wireless communication system according to one aspect of the present invention is controlled by a computer. The system control method involves a central device controlling voice data and the destination radio to which the voice data is transmitted. A voice packet containing multiple pairs of sequence numbers indicating the order in which voice data is transmitted to each terminal. The steps include transmitting the data to all of the multiple wireless base stations connected to the center device, and each A wireless base station has a first wireless terminal connected to it and a second wireless terminal not connected to it. Each wireless terminal, including the wireless terminal itself, has a corresponding ring buffer, and receives The voice data contained in the voice packet is compatible with the wireless terminal to which the voice data is sent. The data is written to the area specified by the write index of the ring buffer provided therefor, and before The read index of the ring buffer provided for the first wireless terminal is specified. This includes the step of reading the audio data written in the specified area.

[0008] Wireless communication, where the operation of a wireless communication system according to one aspect of the present invention is controlled by a computer. The system's control program controls the central device, which receives audio data and the destination to which the audio data is sent. A sound containing multiple pairs of audio data and sequence numbers indicating the order of the audio data transmitted to each wireless terminal. Steps to transmit voice packets to all of the multiple wireless base stations connected to the central device. Each wireless base station then has a first wireless terminal connected to it and a second wireless terminal that is not connected to it. Each wireless terminal, including the second wireless terminal, has a corresponding ring buffer, The voice data contained in the transmitted voice packet is transmitted to the wireless terminal that is the destination of the voice data. Write to the area specified by the write index of the ring buffer provided in response to it. Furthermore, the read index of the ring buffer provided in relation to the first wireless terminal The process includes the step of reading audio data written to a specified area. [Effects of the Invention]

[0009] According to the wireless communication system of the present invention, the wireless base station to which the wireless terminal is connected is switched. Even if this happens, audio data can be received without any problems. [Brief explanation of the drawing]

[0010] [Figure 1] Block diagram showing an example of the overall configuration of a wireless communication system in one embodiment. [Figure 2] This is a block diagram showing an example of the configuration of a center device in a wireless communication system according to one embodiment. [Figure 3] This is a block diagram showing an example configuration of a wireless base station in one embodiment of a wireless communication system. [Figure 4] It is a block diagram showing a configuration example of a wireless terminal in a wireless communication system according to an embodiment. [Figure 5] It is a conceptual diagram showing a base station management table managed by the base station management unit of the center device. [Figure 6] It is a conceptual diagram showing a terminal information table managed by the wireless terminal management unit of the center device. [Figure 7] It is a sequence diagram showing a communication sequence when a wireless terminal connects to a wireless base station and the center device registers the wireless terminal. [Figure 8] It is a conceptual diagram showing a wireless terminal registration request transmitted by the wireless terminal to the center device. [Figure 9] It is a conceptual diagram showing terminal information of a wireless terminal transmitted by the center device to a wireless base station. [Figure 10] It is a conceptual diagram showing a wireless terminal information table managed by the wireless terminal management unit of the wireless base station. [Figure 11] It is a sequence diagram showing a registration process executed between the center device and the wireless base station. [Figure 12] It is a conceptual diagram showing a wireless base station registration response transmitted by the center device to the wireless base station. [Figure 13] It is a sequence diagram showing an example of a transmission / reception process of voice data executed among the center device, the wireless base station, and the wireless terminal. [Figure 14] It is a conceptual diagram showing a configuration example of a multicast voice packet transmitted by the center device to the wireless base station. [Figure 15] It is a conceptual diagram showing a configuration example of terminal voice data of one wireless terminal included in the aggregated voice data of the multicast voice packet shown in FIG. 14. [Figure 16] It is a conceptual diagram showing a ring buffer possessed by the buffer management unit of the wireless base station. [Figure 17] It is a conceptual diagram showing a configuration example of a voice packet transmitted by the wireless base station to the wireless terminal. [Figure 18] It is a diagram showing a configuration example of a flag included in the voice packet shown in FIG. 17. [Figure 19] This figure shows a specific example of an audio packet, as shown in Figure 17. [Figure 20] This diagram shows the reference timing for when the central device, wireless base station, and wireless terminal transmit voice packets. [Figure 21] This is a flowchart showing the transmission and reception process at a wireless base station. [Figure 22] Figure 21 shows a flowchart illustrating the reception process of multicast voice packets transmitted from the center device, as part of the transmission and reception process in step S212. [Figure 23] Figure 22 is a flowchart showing the detailed processing of step S222. [Figure 24] Figure 21 shows a flowchart illustrating the process of receiving voice packets transmitted from a wireless terminal, which is part of the transmission and reception process in step S212. [Figure 25] Figure 21 shows a flowchart illustrating the transmission process in step S212 of the transmission and reception process, specifically the transmission process that sends voice packets to the central device and wireless terminals. [Figure 26] Figure 25 is a flowchart showing the transmission process in step S252, where an audio packet is sent to the central device. [Figure 27A] This is a partial flowchart showing the transmission process in which a wireless base station sends a voice packet to a wireless terminal in step S252, as shown in Figure 25. [Figure 27B] Figure 27A is followed by a partial flowchart showing the transmission process in which a wireless base station sends a voice packet to a wireless terminal in step S252 shown in Figure 25. [Figure 27C] Figure 27A is followed by a partial flowchart showing the transmission process in which a wireless base station sends a voice packet to a wireless terminal in step S252 shown in Figure 25. [Figure 28] This flowchart shows how a wireless terminal that has switched to a different wireless base station via roaming can obtain the IP address of the newly connected wireless base station. [Modes for carrying out the invention]

[0011] The following describes a wireless communication system according to one embodiment, a control method for the wireless communication system, and a buffer tube. The method will be explained with reference to the attached drawings. As shown in Figure 1, the wireless communication system Center equipment 10, wireless base stations 20A, 20B, 20C, wireless terminals 30A, 30B, 30 It includes C and 30D. The illustration does not specify which of the wireless base stations 20A to 20C is included. Any wireless base station, including other wireless base stations that are not currently operating, shall be referred to as wireless base station 20. Without specifying one of the wireless terminals 30A to 30D, use other wireless terminals not shown in the diagram. This shall be referred to as wireless terminal 30.

[0012] The number of wireless base stations 20 and wireless terminals 30 shown in Figure 1 is merely an example. The number of zeros and the number of wireless terminals (30) are not limited.

[0013] The center device 10 and the wireless base stations 20A~20C are connected by a wired network 15N. The wireless base station 20 may be directly connected to the center device 10, or it may be connected to other wireless devices. It may also be connected to the center device 10 via the base station 20. The method of connecting to the linear base station 20 is not limited. The center device 10 connects to wireless base stations 20A~2 The central device 10 manages wireless base stations 20A to 2 The audio data received from wireless terminals 30A to 30D via 0C is mixed, and the group Create audio data for phone calls.

[0014] Wireless communication ranges 40A, 40B, and 40C are defined as follows: Wireless terminal 30 is connected to wireless base station 20A, This shows the range in which communication is possible when connected to 20B and 20C. In Figure 1, the wireless terminal 30A is not It is located within the line communication range 40A and connected to the wireless base station 20A. The wireless terminal 30B is Located within wireless communication range 40B and connected to wireless base station 20B. Wireless terminal 30C And 30D is located within the wireless communication range 40C and is connected to the wireless base station 20C. Linear communication ranges 40A, 40B, and 40C constitute a wireless network.

[0015] Wireless communication between wireless base stations 20A-20C and wireless terminals 30A-30D is a wireless LAN. It complies with the IEEE 802.11 communication standard.

[0016] As shown in Figure 2, the center device 10 consists of a receiving unit 11, a received data processing unit 12, and a base station pipe. Control Unit 13, Voice Data Processing Unit 14, Wireless Terminal Management Unit 15, Transmission Cycle Management Unit 16, Transmission Data It comprises a data creation unit 17 and a transmission unit 18. A solid arrow line is shown to the receiving unit 11 and from the transmission unit 18. The solid arrow line corresponds to the wired network 15N connected to the wireless base station 20. The station management unit 13 manages the base station management table 130, and the wireless terminal management unit 15 manages the terminal information table Manage the Bull 150.

[0017] As shown in Figure 3, the wireless base station 20 includes a receiving unit 21, a received data processing unit 22, and a synchronization management unit. Unit 23, Buffer Management Unit 24, Wireless Terminal Management Unit 25, Transmission Cycle Management Unit 26, Transmission Data Production Unit It comprises a receiver 27 and a transmitter 28. A solid arrow line is shown to the receiver 21 and a solid arrow line is shown from the transmitter 28. The arrow line corresponds to the wired network 15N connected to the wireless base station 20. Receiver 2 The dashed arrow line to 1 and the dashed arrow line from the transmitting unit 28 indicate wireless communication with the wireless terminal 30. This corresponds to a linear network. The buffer management unit 24 has a buffer 240. Wireless terminal tube The science department 25 manages the wireless terminal information table 250.

[0018] As shown in Figure 4, the wireless terminal 30 consists of a receiving unit 31, a received data processing unit 32, and a synchronization management unit. 33, Buffer Management Unit 34, Transmission Cycle Management Unit 35, Transmission Data Creation Unit 36, Transmission Unit 37 Prepare. The dashed-dotted arrow lines to the receiving unit 31 and the dashed-dotted arrow lines from the transmitting unit 37 are not This corresponds to a wireless network with the base station 20. The buffer management unit 34 is a playback buffer 34. It contains 0.

[0019] The general operation of the center device 10, wireless base station 20, and wireless terminal 30 will be explained. (See Figure 2) The receiving unit 11 then receives data from the wired network 15N. Received data processing unit 12 processes the data received by the receiving unit 11. The receiving unit 11 receives data from the wireless base station 20 as described below. When a wireless base station registration request is received, the base station management unit 13 processes the received data processing unit 1 2 receives a wireless base station registration request. The base station management unit 13 receives the wireless base station 20 I The base station ID is assigned to the P address. As shown in Figure 5, the base station management unit 13 is the base station The base station ID and IP address are stored as pairs in management table 130.

[0020] When the receiving unit 11 receives a wireless terminal registration request from the wireless base station 20, the wireless The terminal management unit 15 receives a wireless terminal registration request from the received data processing unit 12. The end-management unit 15 assigns a terminal ID to the IP address of the wireless terminal 30. As shown in Figure 6. The wireless terminal management unit 15 then receives the terminal ID, IP address, MAC address of the wireless terminal 30, The buffer size of the playback buffer 340 is then stored in the terminal information table 150 as a set. The wireless terminal management unit 15 will, for each wireless terminal 30 to which it will transmit voice data, make the following sound It manages sequence numbers that indicate the order of voice data.

[0021] The audio data processing unit 14 processes the audio data received by the receiving unit 11 to create transmission data. It supplies power to unit 17. The transmission cycle management unit 16 transmits multicast voice packets, which will be described later. It manages the timing. The transmission data creation unit 17 receives data supplied from the voice data processing unit 14. The transmission data creation unit 17 generates transmission data based on the voice data. The transmission data creation unit 17 generates transmission data for multiple wireless terminals 3 It is possible to create multicast voice packets by combining voice data transmitted from 0. The transmitting unit 18 transmits multicast voice packets to the wired network 15N.

[0022] An example of a multicast voice packet created by the voice data processing unit 14 is shown. There are multiple wireless terminals 30, and there are 6 wireless terminals 30A to 30F. Of these, wireless terminals 30A to 30C belong to the group 1 call group, and wireless terminal 30D Let's assume that ~30F belongs to the call group in Group 2.

[0023] The voice data processing unit 14 mixes the voice data received from the wireless terminals 30B and 30C. This creates voice data addressed to wireless terminal 30A. This voice data is shown in Figure 15 below. This will be the audio data included in the audio data processing unit 14. The received audio data is mixed to create audio data to be sent to the wireless terminal 30B. The data processing unit 14 mixes the audio data received from the wireless terminals 30A and 30B. Then, create voice data to be sent to wireless terminal 30C.

[0024] The aggregated voice data in Figure 14, described later, includes messages addressed to wireless terminal 30A, wireless terminal 30B, and wireless terminal 3 When including voice data addressed to 0C, the terminal ID, sequence number, and voice data combination shown in Figure 15 This will be aggregated audio data containing three of these elements.

[0025] The transmission data creation unit 17 receives voice data from the voice data processing unit 14 addressed to each wireless terminal 30. The data is used to create the multicast audio packet shown in Figure 14. Voice packets are not group-dependent; for example, they can be sent to wireless terminal 30C belonging to a different group. Voice data destined for wireless terminal 30D may be included in a single multicast voice packet.

[0026] In Figure 3, the receiving unit 21 receives multicast voice packets from the wired network 15N. The receiver unit 21 receives a voice packet from the wireless network. The data processing unit 22 processes the data received by the receiving unit 21. As will be described later, the received data The processing unit 22 may analyze or determine the data received by the receiving unit 21. Synchronization management Unit 23 generates a reference timing for the transmission unit 28 to transmit voice packets, and transmits the transmission period tube It will be supplied to the 26th irrigation unit.

[0027] The buffer management unit 24 saves audio data to the buffer 240, or the buffer 240 It reads out audio data and manages various types of data, which will be described later. The wireless terminal management unit 25 , information from the wireless terminal 30 transmitted from the center device 10, and wireless terminal connected to the station The information of terminal 30 is stored in the wireless terminal information table 250 to manage the wireless terminal 30.

[0028] The transmission cycle management unit 26 manages the transmission timer (described later) and generates the transmission trigger (described later). The transmission data creation unit 27 creates the transmission data and supplies it to the transmission unit 28. It transmits data to a wired network 15N or a wireless network.

[0029] In Figure 4, the receiving unit 31 receives data from the wireless network. Received data processing The processing unit 32 processes the data received by the receiving unit 31. The synchronization management unit 33 controls the transmission unit 37. It generates a reference timing for transmitting voice packets and supplies it to the transmission cycle management unit 35. The buffer management unit 34 manages the playback buffer 340 that stores audio data. The logic unit 35 manages the timing of voice packet transmission. The transmission data creation unit 36 ​​transmits The data is created. The transmission unit 37 wirelessly transmits the transmission data created by the transmission data creation unit 36. Send data to the network.

[0030] Figure 7 shows that the wireless terminal 30A is connected to the wireless base station 20A, and the central device 10 is connected to the wireless terminal 30 This shows the communication sequence when registering A. In step S71, the wireless terminal 30A connects A connection request is sent to the wireless base station 20A, and the wireless base station 20A responds in step S72. The answer is sent to the wireless terminal 30A. This connects the wireless terminal 30A to the wireless base station 20A. Steps S71 and S72 are performed at the wireless base station 20A and the wireless terminal 30A. This is the connection process.

[0031] In step S73, the wireless terminal 30A sends a wireless terminal registration request R to the central device 10. Send 73. As shown in Figure 8, the wireless terminal 30A sends the center device 1 in step S73. The wireless terminal registration request R73 to be sent to 0 contains the MAC address of wireless terminal 30A and Includes the buffer size of the regeneration buffer 340 provided by the line terminal 30A. Wireless terminal registration request Upon receiving signal R73, the center device 10, in step S74, transmits the signal via the wireless base station 20A. Then, the wireless terminal registration response is sent to the wireless terminal 30A. At this time, the center device 10, A terminal ID is assigned to the wireless terminal 30A. As a result, the central device 10 assigns a terminal ID to the wireless terminal 30A. Register it.

[0032] Steps S73 and S74 are performed between the center device 10 and the wireless terminal 30A. This is a pre-registration process.

[0033] In steps S75, S76, and S77, the center device 10 receives terminal information of the wireless terminal 30A. I30A is transmitted to wireless base stations 20A, 20B, and 20C, respectively. As shown in Figure 9. Terminal information I30A is the terminal ID of the wireless terminal 30A assigned by the center device 10, wireless terminal Includes the IP address, MAC address, and buffer size of the last 30A. Wireless terminal 30A The MAC address and buffer size are included in the received wireless terminal registration request R73. The IP address of wireless terminal 30A is obtained from the center device 10 in the wireless terminal registration request R. It can be obtained when 73 is received.

[0034] Figure 10 shows the wireless terminal information table 25 managed by the wireless terminal management unit 25 of the wireless base station 20. It shows 0. The receiving unit 21 of wireless base stations 20A~20C receives terminal information I30A as shown in Figure 9. Upon receiving the data, the received data processing unit 22 supplies the terminal information I30A to the wireless terminal management unit 25. The wireless terminal management unit 25 records the terminal ID and IP address of the wireless terminal 30A in the wireless terminal information table 250. Stores address, MAC address, buffer size, and reception time. (Radio base station 20) If the receiving unit 21 of A~20C similarly receives terminal information I30 from another wireless terminal 30, The terminal information table 250 contains the terminal ID, IP address, MAC address, etc. of multiple wireless terminals 30. The dress code, buffer size, and reception time are saved.

[0035] Figure 11 shows the registration process performed between the center device 10 and the wireless base station 20A. The wireless base station 20A sends a wireless base station registration request to the center device 10 in step S111. Send Est R111. As described above, the receiving unit 11 of the center device 10 registers the wireless base station. Upon receiving recording request R111, the base station management unit 13 uses the base station management table shown in Figure 5. The base station ID and IP address are stored in pairs in 130. Transmitter 18 of center device 10 In step S112, the wireless base station registration response R112 is sent to the wireless base station 20A. I believe.

[0036] As shown in Figure 12, the radio base station registration response R112 is assigned to radio base station 20. The base station ID, wireless terminal connected to the center device 10 via the wireless base station 20. The number of connected terminals is 30, and the terminal information I30 of the connected wireless terminals is as follows: Includes connected terminal information. Wireless terminals 30A, 30B, and one or more other wireless terminals. Assume that terminal 30 is connected to the central device 10. In this case, the connected terminal information is: Terminal information I30A of line terminal 30A, terminal information I30B of wireless terminal 30B, and other 1 This includes terminal information I30 of the wireless terminal 30 or more.

[0037] Using Figure 13, the following is performed between the center device 10, the wireless base station 20, and the wireless terminal 30. An example of audio data transmission and reception processing will be explained. In step S1301, the center device 10 performs Multicast voice packets containing voice data destined for line terminal 30A and wireless terminal 30B are not The data will be transmitted via multicast to base stations 20A-20C.

[0038] In step S1302, the center device 10 receives voice messages addressed to wireless terminal 30C and wireless terminal 30D. Multicast voice packets containing data are sent to wireless base stations 20A-20C. Send it.

[0039] In this way, voice data destined for multiple wireless terminals 30 is multicast to each wireless base station 20 It will be sent to [destination].

[0040] In step S1303, the wireless base station 20A receives data from the wireless terminal 30A and buffers it. The voice data being recorded is transmitted as a voice packet to the center device 10. Wireless base station 20 In step S1304, A receives a multicast voice packet from the center device 10 in step S1301. Voice data addressed to wireless terminal 30A, which is receiving and buffering the packet, is now being processed as voice packets. This is then transmitted to the wireless terminal 30A.

[0041] Wireless base station 20B, in step S1305 which is simultaneous with step S1304, in step S1301 The wireless terminal receives and buffers multicast voice packets from the terminal device 10. Voice data addressed to terminal 30B is transmitted to the wireless terminal 30B as a voice packet.

[0042] In step S1306, the wireless base station 20B receives from the wireless terminal 30B and buffers The voice data being recorded is transmitted as a voice packet to the center device 10. Wireless base station 20 In steps S1307 and S1308, C receives data from wireless terminals 30C and 30D, respectively. The voice data being filtered is transmitted to the center device 10 as voice packets.

[0043] In step S1309, the wireless terminal 30A sends voice data as voice packets to the wireless base station. The data is sent to 20A. In step S1310, the wireless terminal 30B sends the voice data as a voice packet. This is then transmitted to the wireless base station 20B.

[0044] The center device 10, wireless base stations 20A and 20B, and wireless terminals 30A and 30B are step Steps S1311 to S1320 are performed in the same manner as steps S1301 to S1310.

[0045] Figure 14 shows the transmissions to wireless base stations 20A-20C in steps S1301, S1302, S1311, and S1312. This shows an example of the configuration of a multicast voice packet. Multicast voice packets are wireless A synchronization flag indicating that the packet is the one that base station 20 will use as the reference for transmission timing, packet The number of terminals that include the number of terminal voice data, and the addressed to multiple wireless terminals 30. This includes aggregated voice data. The aggregated voice data is generated from 30 wireless terminals, indicated by the number of terminals. Contains several minutes of audio data. If the number of terminals is 0, the multicast audio packet will be aggregated. Does not include data.

[0046] Figure 15 shows the structure of terminal voice data for one wireless terminal 30 included in the aggregated voice data. An example is shown. Terminal voice data is the destination of the voice data included in aggregated voice data. The terminal ID of the wireless terminal 30, and the sequence of voice data managed for each wireless terminal 30. It consists of a quense number and one cycle of audio data. One multicast audio packet The number of terminal voice data to include in the package is set to a size that prevents fragmentation during IP communication. It may be limited to this.

[0047] As shown in Figure 16, buffer 240 has a ring buffer 240R. Although only one ring buffer 240R is shown, buffer 240 is used for wireless terminals 30. It has a ring buffer 240R. The ring buffer 240R is a buffer index It has four regions that can be selected by S0-3, and four sets of sequence numbers and sounds Voice data can be stored. The four areas of the ring buffer 240R are for the latest transmission. Area for writing audio data from the current period up to a predetermined period prior (in this case, 3 periods prior). That is the case.

[0048] The buffer management unit 24 cycles through buffer indices 0 to 3 based on the write index. By specifying it, you can specify the area where the sequence number and audio data will be written. This is possible. The buffer management unit 24 uses the read index to determine the buffer index 0 By specifying ~3 cyclically, the area from which the sequence number and audio data are read is specified. It can be specified. The buffer management unit 24 controls the write index and the read index. This manages updates to the index. Note that the write index and read index are not synchronized.

[0049] When the wireless base station 20 receives a multicast voice packet from the center device 10, The management unit 24 is a ring buffer 24 corresponding to the terminal ID of the wireless terminal 30 shown in Figure 15. Select 0R and save the sequence number and audio data. Figure 16 shows the write index. Since it is 2, the buffer management unit 24 puts the sequence number in the area of ​​buffer index 2. Write down the serial number and audio data.

[0050] The wireless terminal management unit 25 has the synchronization flag set for multicast as shown in Figure 14. The time when the voice packet was received is recorded in the terminal ID of the wireless terminal information table 250 shown in Figure 10. Save this as the corresponding reception time.

[0051] In Figure 16, the read index is 1, so the wireless base station 20 is the ring buffer 240 When transmitting audio data stored in R to the wireless terminal 30, the buffer management unit 24 This reads the sequence number and audio data from the area at buffer index 1.

[0052] Figure 17 shows the sound that the wireless base station 20A transmits to the wireless terminal 30A in steps S1304 and S1314. Voice packets, sound transmitted by the wireless base station 20B to the wireless terminal 30B in steps S1305 and S1315. This shows an example of a voice packet configuration.

[0053] The voice packet contains the communication ID assigned by the wireless base station 20 to the wireless terminal 30, and the read index. The sequence number stored in the area specified by the buffer index indicated by the 'ks' includes Hmm. Voice packets start from the time when the wireless base station 20 begins transmitting voice packets, as shown in Figure 10. The value obtained by subtracting the reception time corresponding to the terminal ID in the wireless terminal information table 250 shown is the D The log includes the time and flags indicating information about the included audio data. The audio packet is also read out. Audio data stored in the area specified by the buffer index indicated by the index. Includes multiplexed audio data. Multiplexed audio data can contain multiple audio data. ru.

[0054] Figure 18 shows an example of the configuration of flags included in the audio packet shown in Figure 17. As shown in 18, the flag consists of 8 bits of data. The bit labeled N is the most The least significant bit is the bit labeled N-7. This is the audio data of the sequence number contained in the audio packet (buffer index in Figure 16). Indicates whether the audio data of X1 is included in the multiplexed audio data within the audio packet. The second bit, labeled N-1, is the sequence included in the audio packet. Is the audio data for the sequence number one cycle prior to the current sequence number included in the multiplexed audio data? To indicate whether or not.

[0055] Similarly, the 3rd to 7th bits, denoted as N-2 to N-6, are respectively 2 to This indicates whether the audio data from the sequence number six steps prior is included in the multiplexed audio data. The most significant bit contains audio data from the sequence number 7 cycles prior, which is included in the multiplexed audio data. Indicates whether or not it is present. If the audio data is included in the multiplexed audio data, the value of each bit is If it is 1 and the audio data is not included in the multiplexed audio data, the value of each bit is 0. "That is the case."

[0056] For example, if the flag is "11110111", it will play the sound of the sequence number from three cycles ago. The voice data is not included in the multiplexed audio data, and the audio data is from a different sequence number. This means that it is included in the multiplexed audio data.

[0057] The multiplexed audio data contained in the audio packet shown in Figure 17 is the audio data indicated by the flag. This is a concatenation of the 'Ta's in reverse chronological order. The flag is not limited to 8 bits; other sizes are also possible. That's fine.

[0058] Figure 19 shows a specific example of the voice packet shown in Figure 17. As shown in Figure 19, Signal ID is 10, Sequence number is 3000, Delay time is 5, Flag is 0000010 It is 1. Since the flag is 00000101, the multiplexed audio data is sequence number 3000 audio data and the audio data of sequence number 2998, which is the sequence from two cycles ago. It includes the data. The audio packet shown in Figure 19 contains the audio data and sequence number 3000. This includes multiplexed audio data concatenated in this order with audio data of Instance No. 2998.

[0059] Figure 20 shows the transmission of voice packets by the center device 10, wireless base station 20, and wireless terminal 30. This indicates the reference timing. The center device 10 is the first reference timing of the transmission cycle P1. CT1, CT2, etc. begin transmitting multicast voice packets to wireless base station 20. When the first reference timing CT1, CT2, etc. arrives, the terminal device 10 will perform the operation as shown in Figure 14. Set the synchronization flag at the beginning and send it to all wireless terminals 30, the number of terminals indicated by the terminal count. The aggregated voice data is transmitted via multicast.

[0060] The wireless base station 20 uses the second reference timing AT1, AT2, etc. of the transmission cycle P1 as a reference. The radio base station 20 transmits voice packets to the center device 10 and the wireless terminal 30. Offset time d1 from the time a multicast voice packet with the flag set is received. The point in time after that period is designated as the second reference timing, AT1, AT2, etc.

[0061] In detail, the wireless base station 20 sets the base station ID to the second reference timing AT1, AT2… At the added time, a voice packet is sent to the center device 10. This allows each wireless base station 2 The timing of when 0 sends voice packets to the center device 10 can be shifted. Add a value different for each of the 20 wireless base stations, other than the base station ID, to the reference timing AT1, AT2, etc. The timing of sending voice packets to the central device 10 may be adjusted accordingly.

[0062] The timing of when multiple wireless base stations 20 transmit voice packets to the central device 10 is staggered. This makes it possible to avoid collisions of voice packets on the wired network 15N, and sound There is virtually no data loss in the voice data.

[0063] The wireless base station 20 sends voice packets to the wireless terminal 30 at the second reference timing AT1, AT2, etc. The transmission of the signal begins. That is, all wireless base stations 20 transmit the signal to each other at the same time. Send a voice packet at the end of 30.

[0064] The wireless terminal 30 communicates with the wireless base station at the third reference timing ST1, ST2… of the transmission cycle P1. Sending voice packets to 20 begins. The third reference timing ST1, ST2… is the second This is the time elapsed by an offset time d2 from the reference timing AT1, AT2, etc. The line terminal 30 receives the voice packet transmitted from the wireless base station 20, as shown in Figure 17. Subtract the delay time included in the audio packet and add the offset times d1 and d2. The point in time when this occurs will be designated as the third reference timing, ST1, ST2, etc.

[0065] Next, even if the wireless terminal 30 switches wireless base station 20, it will always receive the latest voice data. This document explains the method and how to reduce audio interruptions during roaming. Connect to the center device 10. The wireless base stations 20A to 20C are receiving multicast voice transmitted by the center device 10. Receive a packet.

[0066] Each radio base station 20 sends voice messages to the radio terminal 30 (first radio terminal) connected to it. The data is transmitted to the ring battery provided for the wireless terminal 30 connected to the station. It is stored in 240R (first ring buffer). Each radio base station 20 is connected to its own station. Voice data addressed to wireless terminal 30 (second wireless terminal) that is not connected to its own station is sent via a device connected to its own station. A ring buffer 240R (second ring buffer) is provided to accommodate the wireless terminal 30 which does not have a wireless terminal 30. Save it to (Fa).

[0067] The wireless base station 20 communicates to the wireless terminal 30 connected to it via the ring buffer 240R. To transmit the stored audio data as audio packets at transmission cycle P1, connect to your own station. The read index of the ring buffer 240R provided in accordance with the wireless terminal 30 is The system is updated every transmission cycle P1. The wireless base station 20 receives wireless signals that are not connected to its own station. Since there is no need to send voice packets to terminal 30, wireless terminal 3 which is not connected to the station The read index of ring buffer 240R, which is set up to correspond to 0, will not be updated. This is a possible explanation.

[0068] However, this means that the wireless terminal 30 will roam to other wireless base stations 20 (other When the wireless base station 20 switches from the station to its own station, the wireless terminal 30 receives the latest voice data You cannot send data.

[0069] Therefore, the buffer management unit 24 of each wireless base station 20 controls the wireless terminal 3 connected to it. The read index of the ring buffer 240R, which is set to correspond to 0, is transmitted during the transmission period P1. In addition to updating each time, wireless terminals that are not connected to their own station (but are connected to other stations) The read index of the ring buffer 240R, which is provided in accordance with 30, is transmitted during the transmission period P. Update every 1.

[0070] After updating the read index of the ring buffer 240R, the buffer management unit 24 then... The ring buffer 240R is provided to accommodate the wireless terminal 30 that is not connected to the station. Clear the sequence number pointed to by the read index.

[0071] Clearing the sequence number means setting the sequence number to an invalid value, such as "-1". This is to disable it. The read index is the voice data to be transmitted in the next transmission cycle P1. This shows the buffer index of ring buffer 240R, which includes the tag.

[0072] As described above, each wireless base station 20 allows the wireless terminal 30 to roam with other wireless stations. When switching from base station 20 to the local station, the latest information is sent to the wireless terminal 30. It can transmit audio data.

[0073] Furthermore, the arrival of voice data transmitted from the center device 10 to the wireless base station 20 is delayed. Audio data has not been written to the buffer index area pointed to by the read index. Sometimes, by clearing the sequence number, the buffer pointed to by the read index... It is possible to determine whether or not audio data has been written to the index area.

[0074] A second reference timing that serves as the basis for determining when the wireless base station 20 transmits voice packets. AT1, AT2, etc. are the same for all 20 radio base stations. Therefore, for each transmission cycle P1 The read index of the ring buffer 240R provided for each wireless terminal 30 is By updating, the voice data transmitted between the wireless base stations 20 to the wireless terminal 30 can be synchronized. It is possible.

[0075] The flowchart shown in Figure 21 illustrates the transmission and reception process at the wireless base station 20. Once initiated, the wireless base station 20 performs timing synchronization processing in step S211. In step S212, the send / receive process is executed, and the process is terminated.

[0076] Specifically, the receiving unit 21 receives a marker that has been set to the synchronization flag transmitted from the center device 10. When a cast voice packet is received, in step S211, the received data processing unit 22 The synchronization management unit 23 analyzes the received data and sets the second reference timings AT1, AT2, etc. It is generated and supplied to the transmission cycle management unit 26. The transmission cycle management unit 26 starts the transmission timer. The transmission timer is a timer that expires with each transmission cycle P1. The receiving unit 21 and the transmitting unit 28 are In step S212, multicast voice packets transmitted from the center device 10 are The center device 10 and the wireless terminal receive the voice packets transmitted from the wireless terminal 30. Send a voice packet to terminal 30.

[0077] The flowchart shown in Figure 22 shows the transmission and reception processing of step S212 shown in Figure 21, This shows the receiving process for multicast voice packets transmitted from the center device 10. When processing begins, the receiving unit 21 receives the transmission from the center device 10 in step S221. The buffer management unit 24 receives multicast voice packets in step S222. Then, the audio data of the received multicast audio packet is saved to buffer 240.

[0078] The flowchart shown in Figure 23 illustrates the detailed processing of step S222 shown in Figure 22. When processing begins, the received data processing unit 22, in step S231, processes the unprocessed data. Determine whether the number of voice data points is 1 or more. (This is done for each of the 30 wireless terminals indicated by the number of terminals.) If processing of all audio data has not been completed, the number of unprocessed audio data files is 1 or more. If the number of unprocessed audio data is 1 or more (YES), the buffer management unit 24 proceeds to step S2 In step 32, select the ring buffer 240R corresponding to the terminal ID of the wireless terminal 30.

[0079] In step S233, the buffer management unit 24 outputs sound to the selected ring buffer 240R. The voice data is saved. In step S234, the buffer management unit 24 receives the sequence number. The data is stored in the ring buffer 240R. In step S235, the buffer management unit 24 performs the following operation. Unsent data stored in buffer 240R that has not yet been sent to wireless terminal 30 The data count is updated to increment by 1. The received data processing unit 22 performs step S23 In step 6, the number of unprocessed audio data is updated to decrement by 1, and processing is performed in step S2. Return to 31.

[0080] If the number of unprocessed audio data in step S231 is not 1 or more (NO), the number of terminals will be indicated. This means that the processing of all voice data for all 30 wireless terminals has been completed, and the wireless terminals Local station 20 will terminate processing.

[0081] The flowchart shown in Figure 24 shows the transmission and reception processing of step S212 shown in Figure 21, This shows the process of receiving voice packets transmitted from the wireless terminal 30. When processing begins... In step S241, the receiving unit 21 receives the voice packets transmitted from the wireless terminal 30. I believe. In step S242, the buffer management unit 24 processes the audio data of the received audio packet. The data is stored in the ring buffer 240R. The received data processing unit 22 performs step S243 The number of unsent data to the center device 10 is updated to increment by 1, and the process is performed. Terminate the process.

[0082] The flowchart shown in Figure 25 shows the transmission and reception processing of step S212 shown in Figure 21, This shows the transmission process for sending voice packets to the center device 10 and the wireless terminal 30. When this is started, the transmission cycle management unit 26 receives a reference timing from the synchronization management unit 23, In step S251, the transmit timer is started, and when the transmit timer expires, a transmit trigger is issued. The transmission timer expires, and a transmission trigger is generated. The transmission unit 28 performs the following steps: In step 2, voice packets are sent to the center device 10 and the wireless terminal 30 to terminate the process. .

[0083] The flowchart shown in Figure 26 shows the sound of the center device 10 in step S252 shown in Figure 25. This shows the transmission process for sending voice packets. When the process starts, the buffer management unit 24 In step S261, it is determined whether the number of unsent data is 1 or more. If the number of data is 1 or more (YES), the transmission data creation unit 27, in step S262, The transmitter unit 28 creates the voice packet to be transmitted in step S263. The data is sent to the center device 10. In step S264, the buffer management unit 24 does not The number of data to be sent is updated to increment by 1, and the process returns to step S261.

[0084] If the number of untransmitted data in step S261 is not 1 or more (NO), the wireless base station 20 will process End the discussion.

[0085] As shown in Figure 26, the wireless base station 20 buffers the data in buffer 240. The audio data received from each wireless terminal 30 is transmitted to the central device 10.

[0086] The flowcharts shown in Figures 27A to 27C show that the wireless base station 20 is located at the steps shown in Figure 25. This shows the transmission process in step S252, where a voice packet is sent to the wireless terminal 30.

[0087] In Figure 27A, when processing begins, the buffer management unit 24 performs the following in step S2701: The system determines whether the number of untransmitted wireless terminals 30 (hereinafter referred to as untransmitted terminals) is 1 or more. If the number of transmitting terminals is 1 or more (YES), the buffer management unit 24, in step S2702, Select the wireless terminal 30 (transmitting terminal) to send voice packets. The buffer management unit 24 selects the wireless terminal 30 (transmitting terminal) to send voice packets. In step S2703, the number of unsent data addressed to the wireless terminal 30 selected in step S2702 is 1 or more. Determine whether or not it is true.

[0088] If the number of unsent data in step S2703 is 1 or more (YES), the buffer management unit 24 will: In step S2704, it is determined whether or not this is the first transmission after connecting the wireless terminal 30. In other words, the buffer management unit 24 determines that the voice packet to be transmitted is the wireless terminal 30 is wireless In the first voice packet that the radio base station 20 transmits to the radio terminal 30 after connecting to the local station 20, Determine whether it exists or not.

[0089] If it is the first transmission in step S2704 (YES), the transmission data creation unit 27 will perform step S2 In 705, the latest read index stored in ring buffer 240R is Audio data including sequence number audio data and sequence number audio data older than the latest sequence Create a ket. The wireless base station 20 proceeds from step S2705 to step S2707. To make them do it.

[0090] However, the size of the audio data for sequence numbers prior to the latest one is the playback buffer of the wireless terminal 30. If the buffer size is larger than 340, the buffer size of the playback buffer 340 will be used. The audio data exceeding the limit cannot be played back. Therefore, the transmission data creation unit 27 The size of the audio data for the sequence number prior to the new one is the playback buffer 340 of the wireless terminal 30. If the buffer size is less than or equal to the current number, it will contain all audio data including all sequence numbers prior to the latest one. Create a voice packet.

[0091] The transmission data creation unit 27 determines the size of the audio data for a sequence number prior to the latest one at the wireless terminal. If the buffer size of the playback buffer 340 is exceeded, the playback buffer 340 will Create an audio packet containing audio data smaller than or equal to the ff size. At this time, create the transmission data. The adult section 27 selects audio data with a newer sequence number and plays it in the playback buffer 340. You just need to create audio packets that are smaller than or equal to the buffer size.

[0092] The transmission data creation unit 27 executes the process in step S2705, which enables roaming This can reduce audio interruptions. The connected wireless terminal 30 (third wireless terminal) is provided in accordance with the third wireless terminal. At least the following is written to the ring buffer 240R (third ring buffer). It can receive some voice data. The third wireless terminal can connect to other wireless base stations 20 (the During the process of switching to base station 2, audio data that could not be received is played back in the playback buffer. It can be received as valid audio data within the buffer size range of 340. .

[0093] If it is not the first transmission in step S2704 (NO), the transmission data creation unit 27 performs step S In 2706, the latest read index stored in ring buffer 240R is Create a voice packet containing voice data of the quence number. The wireless base station 20 steps The process proceeds from step S2706 to step S2707.

[0094] In step S2707, the transmitting unit 28 transmits the audio packet generated in step S2705 or S2706. The message is sent to the wireless terminal 30, and the process proceeds to step S2708 in Figure 27B.

[0095] On the other hand, if the number of unsent data in step S2703 is not 1 or more (NO), then the unsent voice data Since there is no data, the wireless base station 20 moves the process to step S2708 in Figure 27B. To make them do it.

[0096] In Figure 27B, the buffer management unit 24, in step S2708, reads the index The value is updated. In step S2709, the buffer management unit 24 decrements the number of unsent data by 1. Update the number of unsent data entries.

[0097] In step S2710, the buffer management unit 24 determines whether the number of unsent data is 0 or less. Determine. If the number of unsent data is 0 or less (YES), the buffer management unit 24 performs step S. At 2711, the sequence number of ring buffer 240R pointed to by the read index is cleared. Then, the process moves to step S2712. If the number of unsent data is not 0 or less (NO), The buffer management unit 24 moves the process to step S2712. In step S2712, the number of unsent terminals is decremented by 1 and updated, and the process is shown in Figure 2. Return to step S2701 of 7A.

[0098] Thus, the buffer management unit 24, in step S2703, if the number of unsent data is 1 or more, At that time, the read index and the number of unsent data are updated, and the sequence number is cleared. As a result, the wireless base station 20 receives multicast voice packets transmitted from the center device 10. Even if packet loss occurs, the data that the wireless base station 20 transmits to the wireless terminal 30, and other data It can synchronize with the data transmitted from the wireless base station 20 to the wireless terminal 30.

[0099] In step S2701 of Figure 27A, if the number of unsent terminals is not 1 or more (NO), buffer In step S2713 of Figure 27C, the management unit 24 determines whether the number of unconnected terminals is 1 or more. Determined as follows: The number of unconnected terminals is the number of wireless terminals 30 that are not connected to the wireless base station 20.

[0100] If the number of unconnected terminals in step S2713 is 1 or more (YES), the buffer management unit 24 will In step S2714, select the unconnected terminal, and then in step S2715, select the unconnected terminal. The value of the read index of the last ring buffer is updated. The buffer management unit 24 steps In S2716, the number of unsent data is decremented by 1 and updated.

[0101] In step S2717, the buffer management unit 24 determines whether the number of unsent data is 0 or less. Determine. If the number of unsent data is 0 or less (YES), the buffer management unit 24 performs step S. At 2718, the sequence number of ring buffer 240R pointed to by the read index is cleared. Then, the process moves to step S2719. If the number of unsent data is not 0 or less (NO), The buffer management unit 24 moves the process to step S2719. In step S2719, the number of disconnected devices is decremented by 1 and updated, and the process is stopped. Return to S2713.

[0102] If the number of unconnected terminals in step S2713 is 1 or more, the buffer management unit 24 reads The index and number of unsent data are updated, and the sequence number is cleared. Data transmitted by base station 20 to wireless terminal 30, and data transmitted by other wireless base stations 20 to other wireless base stations It can synchronize with the data transmitted to the wireless terminal 30 connected to 20.

[0103] The buffer management unit 24, in step S2713, if the number of unconnected terminals is not 1 or more, (NO) Terminate the process.

[0104] Using the sequence diagram shown in Figure 28, the wireless base station 20 connected via roaming is switched off. This explains how the replaced wireless terminal 30 obtains the IP address of the newly connected wireless base station 20. To clarify, Figure 28 shows the wireless base station 20 to which the wireless terminal 30A is connected, and the wireless base station 20 is connected to wireless base station 20A. This shows the sequence diagram for switching to base station 20B.

[0105] Wireless base stations 20A and 20B have a second reference timing AT281, AT282, AT 283... transmits voice packets to the center device 10 and the wireless terminal 30. Wireless base station 2 In step S281, 0A transmits voice data to wireless terminal 30A. Wireless terminal 30 In step S282, A transmits voice data to the wireless base station 20A. Wireless terminal 30 A disconnects the connection with the wireless base station 20A by the disconnection process in step S283.

[0106] The wireless terminal 30A connects with the wireless base station 20B through the connection process in step S284. The wireless base station 20B transmits voice data to the wireless terminal 30A in step S285. The wireless terminal 30A receives voice data transmitted from the wireless base station 20B. Then, obtain the IP address, communication ID, and delay time of wireless base station 20B. The address can be obtained from the IP header of the IP packet.

[0107] The wireless terminal 30A receives the IP address, communication ID, and directory of the wireless base station 20B. Step S28 uses the time to determine the transmission timing assigned to the wireless terminal 30A. In step 6, voice data is transmitted to the wireless base station 20B.

[0108] As described above, according to the wireless communication system of this embodiment, the wireless LAN communication standard is With this configuration, even if the wireless base station to which the wireless terminal is connected is switched, the sound will not malfunction. It can receive voice data.

[0109] The present invention is not limited to the embodiments described above, and will not depart from the spirit of the present invention. Various changes are possible within a certain range. [Explanation of Symbols]

[0110] 10 Center device 20,20A,20B,20C Wireless base station 30, 30A, 30B, 30C, 30D Wireless Terminals 11,21,31 Receiving section 12,22 Received data processing unit 13 Base station management department 14. Audio Data Processing Unit 15,25 Wireless Terminal Management Department 16,26,35 Transmission cycle management section 17,27,36 Transmission Data Creation Section 18,28,37 Transmitter 23,33 Synchronization management section 24,34 Buffer Management Section 130 Base Station Management Table 150 Terminal Information Table 240 buffers 240R Ring Buffer 250 Wireless Terminal Information Table 340 playback buffer

Claims

1. Center device and, Multiple wireless base stations connected to the aforementioned center device, One or more wireless connections between each wireless base station in the aforementioned plurality of wireless base stations Line terminal and, Equipped with, The aforementioned center device transmits voice data and to each wireless terminal that is the destination to which the voice data is transmitted. The audio packets include multiple pairs of audio data and sequence numbers indicating the order of the audio data. Transmit to all wireless base stations, Each wireless base station is A first ring buffer provided in accordance with the first wireless terminal connected to the station , and a second ring bar provided for a second wireless terminal not connected to the station It has a ffa, The voice data contained in the received voice packet is transmitted to the destination radio of the voice data transmission destination. Write to the area specified by the write index of the ring buffer provided for the terminal. Read, read from the first ring buffer provided in correspondence with the first wireless terminal. Buffer management unit that reads audio data written to the area specified by the index. and, It has, The aforementioned buffer management unit, At each transmission cycle of the wireless base station, audio data is read from the first ring buffer. The read index that specifies the region is updated, and is provided in accordance with the second wireless terminal. A read index specifies the area from which to read audio data from the second ring buffer. After updating the index, write to the area specified by the read index of the second ring buffer. Clear the entered sequence numbers to invalid values. Wireless communication system.

2. The operation of the wireless communication system is controlled by the central equipment and wireless base station that constitute the wireless communication system. A method for controlling a wireless communication system controlled by a computer between a wireless terminal and a wireless terminal, The central device transmits the voice data to each wireless terminal that is the destination to which the voice data is sent. The center unit stores multiple audio packets containing a sequence number indicating the order of the audio data. The steps include transmitting to all of the multiple wireless base stations connected to the device, Each wireless base station is A first ring buffer provided in accordance with the first wireless terminal connected to the station , and a second ring bar provided for a second wireless terminal not connected to the station It has a ffa, The voice data contained in the received voice packet is transmitted to the destination radio of the voice data transmission destination. Write to the area specified by the write index of the ring buffer provided for the terminal. Read, read from the first ring buffer provided in correspondence with the first wireless terminal. The steps include: reading the audio data written to the area specified by the index, At each transmission cycle of the wireless base station, audio data is read from the first ring buffer. The read index that specifies the region is updated, and is provided in accordance with the second wireless terminal. A read index specifies the area from which to read audio data from the second ring buffer. After updating the index, write to the area specified by the read index of the second ring buffer. The steps include clearing the entered sequence numbers to invalid values, including A method for controlling a wireless communication system.

3. The operation of the wireless communication system is controlled by the central equipment and wireless base station that constitute the wireless communication system. A control program for a wireless communication system controlled by a computer between a wireless terminal and a wireless terminal. 、 The central device transmits the voice data to each wireless terminal that is the destination to which the voice data is sent. The center unit stores multiple audio packets containing a sequence number indicating the order of the audio data. The steps include transmitting to all of the multiple wireless base stations connected to the device, Each wireless base station is A first ring buffer provided in accordance with the first wireless terminal connected to the station , and a second ring bar provided for a second wireless terminal not connected to the station It has a ffa, The voice data contained in the received voice packet is transmitted to the destination radio of the voice data transmission destination. Write to the area specified by the write index of the ring buffer provided for the terminal. Read, read from the first ring buffer provided in correspondence with the first wireless terminal. The steps include: reading the audio data written to the area specified by the index, At each transmission cycle of the wireless base station, audio data is read from the first ring buffer. The read index that specifies the region is updated, and is provided in accordance with the second wireless terminal. A read index specifies the area from which to read audio data from the second ring buffer. After updating the index, write to the area specified by the read index of the second ring buffer. The steps include clearing the entered sequence numbers to invalid values, including A control program for a wireless communication system.

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