JP2004274292A - Method and device for information communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for enabling isochronous communication such as voice by using Bluetooth even in a use environment in which a problem caused by radio wave interference is present. <P>SOLUTION: Even when Bluetooth is used to perform isochronous communication of time series information such as voice information, an ACL (Asynchronous Connection Less) link is used for communication. A packet of prescribed packet type such as a DM3 (data medum 3) packet is used. In addition, the time series information for every prescribed information amount is transmitted at a prescribed transmission interval obtained by taking into consideration of a prescribed information amount and a packet retransmission time duration. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an information communication method suitable for application to, for example, a voice call between a base unit and a slave unit of a cordless telephone and an information communication apparatus using the method.
[0002]
[Prior art]
For example, Bluetooth is well known as an interface specification for short-range wireless communication of about 10 to 100 meters. Transmission of time-series information such as audio information and image information using the Bluetooth technology is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-101104 and Japanese Patent Application Laid-Open No. 2002-112135. ), Patent Document 3 (JP-A-2001-203997) and the like.
[0003]
[Patent Document 1]
JP-A-2002-101104
[Patent Document 2]
JP, 2002-112135, A
[Patent Document 3]
JP 2001-203997 A
[Problems to be solved by the invention]
When isochronous communication of audio information, moving image information, and the like is to be performed in real time, in Bluetooth, an SCO (Synchronous Connection Oriented) link dedicated to isochronous communication is generally used. It is.
[0007]
This SCO link performs communication by transmitting packets of the same size in the same cycle. In addition, because of isochronous priority, even if a packet error occurs, retransmission control is not performed. is there.
[0008]
Therefore, for example, when attempting to use Bluetooth for communication between a base unit and a child unit in a cordless telephone, it is generally conceivable to use an SCO link dedicated to isochronous communication. However, there is the following problem of radio interference.
[0009]
That is, the frequency band used by Bluetooth is the 2.4 GHz band (2.400 to 2.4835 GHz), the band of the electromagnetic wave radiated from the microwave oven, the frequency band used by the wireless LAN (Local Area Network) of the personal computer, and the like. The frequency band overlaps with a frequency band used by a mobile phone, and radio wave interference occurs between them.
[0010]
Also, as described in Patent Documents 1 to 3 above, Bluetooth may be used for short-range wireless communication between various devices, so that radio waves between other Bluetooth devices may be used. There is also the problem of interference.
[0011]
For example, FIG. 7 shows a state of radio wave interference when the radio wave interference source is a wireless LAN (Local Area Network). That is, the wireless LAN is spread and transmitted in a band of about 20 MHz because of the spread spectrum method. On the other hand, in Bluetooth, 79 channels (2.402 to 2.480 GHz) of radio channels are available in the 2.4 GHz band, so that the band of the interference wave by the wireless LAN is equivalent to 20 channels of the Bluetooth radio channel. Therefore, the interference wave from the wireless LAN collides with the Bluetooth wireless channel with a probability of about 1/4.
[0012]
When another Bluetooth device is a radio interference source, as shown in FIG. 8, the interference wave collides with the Bluetooth wireless channel with a probability of 1/79.
[0013]
If there is a collision between the interference wave and the Bluetooth wireless channel due to such radio wave interference, an error occurs in the transmission packet. If the error is an uncorrectable error, the packet is lost. If an error packet is retransmitted, the number of missing packets is reduced and the influence of radio interference is reduced. However, as described above, in the Bluetooth SCO link, priority is given to isochronous transmission. It is designed so that retransmission control of a packet when an error occurs is not performed.
[0014]
For this reason, even if an attempt is made to use Bluetooth for communication between the parent device and the child device in a cordless telephone, it is difficult to ensure voice quality due to the problem of radio wave interference. Conventionally, Bluetooth is used in a cordless telephone. It was difficult.
[0015]
For example, as shown in FIG. 9, when two Bluetooth communication devices 1A and 1B are arranged at a distance of 3 meters from each other, when a noise generation distance Ln by a wireless LAN or another Bluetooth device is measured, the other Bluetooth devices are found. In the case of the radio interference source, when the distance Ln was 3 meters, as shown in FIG. 9, noise generation was observed in the Bluetooth communication device 1B closer to the radio interference source.
[0016]
When the wireless LAN was the radio wave interference source, when the distance Ln was 6 meters, as shown in FIG. 9, noise generation was observed in the Bluetooth communication device 1B closer to the radio wave interference source.
[0017]
Here, when the reception levels of the signal wave and the interference wave became the same, it was determined that noise occurred.
[0018]
In addition, according to the standard, the resistance of the Bluetooth module to radio wave interference is as shown in FIG. That is, according to the standard, the level difference from the interference wave that compensates for the BER (Bit Error Rate) to be 0.1% or less is as follows when the interference wave has the same frequency.
Co-channel interference, C / I co-channel = 11 dB
If the interference wave is adjacent ± 1 MHz,
Adjacent (1 MHz) interference, C / I 1 _MHz = 0 dB
If the interference wave is adjacent ± 2 MHz,
Adjacent (2 MHz) interference, C / I 2 _MHz = −30 dB
Until it is allowed.
[0019]
From the above, it has been difficult to perform communication between a parent device and a child device in a cordless telephone using Bluetooth using an SCO link using Bluetooth in terms of call quality.
[0020]
It is an object of the present invention to provide a method and an apparatus for enabling isochronous communication of voice and the like using Bluetooth even in a use environment where there is a problem due to radio interference as described above.
[0021]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 is:
A method for performing isochronous communication of time-series information such as voice information using Bluetooth,
The communication uses a packet of a predetermined packet type of an ACL (Asynchronous Connection Less) link,
The transmission of the time-series information for each of the predetermined information amounts is performed at a predetermined transmission interval in consideration of the predetermined information amount and a packet retransmission duration.
[0022]
According to the invention of claim 2, in the information communication method of claim 1,
As the predetermined packet type, a DM3 (Data Medium 3) type or a DH3 (Data High 3) type is used, and the predetermined information amount of the time-series information and the transmission are set such that the number of retransmissions becomes two or more. The interval is determined.
[0023]
According to the invention of claim 3, in the information communication method according to claim 1, when a packet error occurs, if retransmission is not completed within the retransmission continuation time, transmission of the next packet is started. It is characterized by doing.
[0024]
[Action]
As a physical link defined by Bluetooth, there is an ACL (Asynchronous Connection Less) link in addition to the SCO link.
[0025]
The ACL link is for performing a packet-switching type connection, and is capable of asynchronously transmitting variable-size packets. The data to be transmitted is user data or control data. Then, in the ALC link, when a transmission error occurs, retransmission control is performed.
[0026]
That is, the ACL packet includes a CRC (Cyclic Redundancy Check) code except for a part of the packet, and the receiving side performs error detection using the CRC code, and returns an appropriate acknowledge when no error is detected. Stipulated in When the transmitting side does not receive this acknowledgment from the receiving side, it retransmits the ACL packet through another channel.
[0027]
In the first aspect of the present invention, the above-described Bluetooth ACL link is used even for isochronous communication of time-series information such as voice information. The transmission interval is a predetermined time interval in consideration of a predetermined amount of time-series information as a transmission unit and a packet retransmission continuation time.
[0028]
Therefore, according to the first aspect of the present invention, even if an error occurs in a transmission packet due to radio wave interference, packet retransmission can be performed, and communication quality that can withstand practical use can be secured.
[0029]
In the case of the invention of claim 2, in particular, the DM3 (Data Medium 3) type or the DH3 (Data High 3) type of the ACL link is used, and the time-series information is set so that the number of retransmissions is two or more. Is determined and the transmission interval is determined. Therefore, as will be described later, practically sufficient transmission quality can be ensured.
[0030]
According to the third aspect of the present invention, when retransmission is not completed within the packet retransmission continuation time, transmission of the next packet is started, so that isochronism can be ensured.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of an information communication method according to the present invention and an information communication apparatus using the method will be described with reference to the drawings. The embodiment described below is a case where the present invention is applied to a cordless telephone.
[0032]
FIG. 2 is a diagram showing an outline of the cordless telephone system, which includes a base unit 10 connected to a telephone network 30 and a slave unit 20 connected to the base unit 10 by a wireless channel using Bluetooth. You. A plurality of slave units 20 can be provided for the master unit 10.
[0033]
As a mode of the cordless telephone system, as shown in FIG. 2A, a handset 11 is connected to a base unit 10 by a curl cord 12, and the handset 11 is provided exclusively for the base unit 10. As shown in FIG. 2B, the handset 20 connected to the base unit 10 by a wireless channel may be placed on the handset mounting unit 13 of the base unit 10 like the handset of the base unit 10. Some types are possible. In the case of the type shown in FIG. 2B, in many cases, when the slave device 20 is placed on the handset mounting portion 13, the master device 10 is configured such that the slave device 20 is charged.
[0034]
The cordless telephone system to which the present invention is applied may be of any of the types shown in FIGS.
[0035]
FIG. 1 is a block diagram illustrating a configuration example of the slave unit 20. The configuration of master device 10 is different from that of slave device 20 only in that voice information transmitted and received by Bluetooth communication is voice from a telephone network and voice to be transmitted to a telephone network. Are the same, and a description of the configuration will be omitted.
[0036]
In FIG. 1, an audio signal from a microphone 201 that collects a transmission audio is supplied to an A / D converter 203 through an amplifier 202, is converted into a digital audio signal, and is then supplied to a codec unit 204. An encoding process is performed to obtain a transmission signal.
[0037]
Further, the digital audio signal from the other party obtained by performing the decoding process in the codec section 204 is supplied to the D / A converter 205 and returned to an analog audio signal, and is supplied to the speaker 207 through the amplifier 206. Sound is reproduced. The codec unit 204 is connected to the audio data processing unit 210.
[0038]
The audio data processing unit 210 is connected to the Bluetooth wireless module 220 by a UART (Universal Asynchronous Receiver / Transmitter).
[0039]
In the audio data processing section 210, the transmission digital audio signal from the codec section 204 is converted into parallel data by the serial-parallel conversion section 211 and is taken into the transmission buffer 212. The transmission buffer 212 sends the digital audio signal to the packet assembling unit 213 for each predetermined data amount. In this example, the transmission buffer 212 stores the 120-byte digital audio signal in the packet assembling unit every time the digital audio signal is accumulated by 120 bytes (when the audio signal is encoded according to the PCM coding rule of 64 kbps; the same applies hereinafter). 213.
[0040]
The packet assembler 213 adds a 5-byte header to the received 120-byte digital audio signal to generate an audio data packet. The audio data packet from the packet assembling unit 213 is converted into serial data by the parallel-serial conversion unit 214 and sent to the wireless module 220 for Bluetooth.
[0041]
In the audio data processing unit 210, the serial data received from the wireless module 220 is converted into parallel data by the serial-parallel conversion unit 215, supplied to the packet disassembly unit 216, decomposed into packets, and received. The data is supplied to the buffer 217. Then, the digital audio signals are sequentially output from the reception buffer 217 so as to be continuously reproduced while maintaining isochronism.
[0042]
That is, in this example, when 120 bytes of the received data are accumulated, a digital audio signal is output from the reception buffer 217 and is used for reproduction. In this example, the reception buffer 217 has a capacity capable of storing, for example, 1 Kbyte of reception data.
[0043]
The digital audio signal from the reception buffer 217 is converted into serial data by the parallel-serial conversion unit 218, and then supplied to the codec unit 204 to be decoded. Then, the codec unit 204 outputs the decoded digital audio signal to the D / A converter 205 as described above.
[0044]
In this example, the audio data processing unit 210 is configured using, for example, an FPGA (Field Programmable Gate Array). However, the audio data processing unit 210 can also be realized by software processing.
[0045]
The wireless module 220 of this example includes a baseband signal processing unit for Bluetooth communication and an RF signal processing unit. The baseband signal processing unit performs a process of a link controller for establishing a wireless link with another device, and a process of a link manager for managing after establishing the link. These processes include a process for performing communication using either the physical link of the SCO link and the ACL link, a process of assembling and disassembling a packet used for communication, and a process for receiving data if there is an error. This includes processing for requesting retransmission from the transmitting side and, when receiving a request for retransmission, processing for retransmitting data using a channel different from the channel in which the error occurred.
[0046]
In addition, the RF signal processing unit of the wireless module 220 selects one of the 79 channels and transmits the packetized data received from the baseband signal processing unit. A process of passing the packetized data received on the wireless channel to the baseband signal processing unit is performed.
[0047]
The codec unit 204, the packet processing unit 210, and the wireless module 220 are controlled by the control unit 230.
[0048]
In this embodiment, in the wireless module 220, communication of the digital audio signal from the audio data processing unit 210 is configured to use an ACL link as a physical link.
[0049]
In this example, the digital audio data from the audio data processing unit 210 is configured to use a DM3 packet as a packet type in the ACL link. Upon receiving the digital audio signal from the audio data processing unit 210, the wireless module 220 includes the digital audio signal as user data (payload) of a DM3 packet.
[0050]
Since the payload of the DM3 packet is 123 bytes including the 2-byte payload header, the digital audio signal of every 120 bytes described above can be included in one of the DM3 packets. A 16-bit CRC code is added to the payload of the DM3 packet to check whether a transmission error has occurred.
[0051]
As a result of the configuration of the wireless module 220 as described above, transmission of audio data is performed in a state as shown in FIG.
[0052]
That is, in this embodiment, as described above, in the audio data processing unit 210, the buffering size of the audio data to be transmitted is set to 120 bytes, and from the audio data processing unit 210, in this example, 15 milliseconds ( The audio packet data is sent to the wireless module 220 every time (equivalent to the time period when the 120-byte audio data is converted back to the analog audio signal).
[0053]
For this reason, as shown in FIGS. 3A and 3B, the transmission interval Tp of the audio data is 15 milliseconds. This is equivalent to 24 time slots since one time slot period of the Bluetooth standard is 625 μsec. The use packet is a DM3 packet and includes 120 bytes of audio data, and thus occupies a period of about three time slots. Therefore, considering the reception of audio packet data from the slave device side, a period corresponding to 24-6 = 18 time slots can be set as the retransmission continuation period RTY.
[0054]
Now, consider the case where both the transmission data from the master side and the transmission data from the slave side cause an error due to radio wave interference, as shown in FIG. Both allow three retransmissions.
[0055]
Considering a case where one of the transmission data from the master side and the transmission data from the slave side has an error due to radio wave interference, as shown in FIG. Up to four times.
[0056]
However, in the retransmission continuation period RTY as shown in FIG. 3, even when retransmission is performed, correct audio data may not be transmitted to the receiving side. In that case, retransmission is continued in the normal use mode of the ACL link. In this embodiment, retransmission is performed only within the retransmission duration RTY, and if the retransmission is correct within the retransmission duration RTY. If the voice data is not transmitted to the receiving side, the retransmission is stopped and the next transmission packet is transmitted. This ensures isochronousity during communication of audio data.
[0057]
Next, in this embodiment, a description will be given of the transmission unit information amount for audio data and the reason and effect of determining the packet type as described above.
[0058]
In the ACL link, there are six types of packets with retransmission control, as shown in the table of FIG. In this case, each packet has an asymmetric type, but in this embodiment, since it is used for voice communication, only a symmetric type is used in this embodiment.
[0059]
In FIG. 4, the DM of the DM1, DM3, and DM5 packets indicates a data-medium rate. The payload of the DM1 packet is composed of information of a maximum of 18 bytes (including a payload header of 1 byte) and a 16-bit CRC code, and the DM1 packet occupies one time slot at the maximum.
[0060]
The DM3 packet is obtained by adding an extended payload to the DM1 packet and occupies a maximum of three time slots. The payload of the DM3 packet is composed of information of a maximum of 123 bytes (including a 2-byte payload header) and a 16-bit CRC code.
[0061]
The DM5 packet is obtained by adding an extended payload to the DM1 packet and occupies a maximum of 5 time slots. The payload of the DM5 packet is composed of information of a maximum of 226 bytes (including a 2-byte payload header) and a 16-bit CRC code.
[0062]
The DH of the DH1, DH3, and DH5 packets indicates a data-high rate. The DH1, DH3, and DH5 packets are almost the same as the DM1, DM3, and DM5 packets except that no error correction code is added to the payload information.
[0063]
The results of calculating the error tolerance against radio interference waves for the main packets of the respective packet types shown in FIG. 4 are as shown in the table of FIG. Here, the DM5 packet and the DH5 packet are not used in this example because the packet size is large and the delay of the audio signal becomes large. In the table of FIG. 5, in consideration of the worst value, when the radio wave interference source is another Bluetooth device, three channels are crushed by the interference wave, and when the radio wave interference source is the wireless LAN, It was assumed that 20 channels were crushed by the interference wave.
[0064]
In the table of FIG. 5, for example, in the case of the DH1 packet, when the radio wave interference source is another Bluetooth device, the probability (worst value) that retransmission cannot be made due to the interference wave is:
(3/79) ² · (1 / 2.5 ms) = 1 / 1.73 sec
Is required.
[0065]
Similarly, for each case in the table of FIG. 5, a probability (worst value) that retransmission cannot be made due to an interference wave is obtained.
[0066]
From the table of FIG. 5, it is practically preferable that the audio buffering size is 120 bytes (15 milliseconds), the packet used is DM3, and the number of retransmissions is three, as in this embodiment. I understand.
[0067]
The evaluation in actual use in the case of this embodiment was as follows. That is, as shown in FIG. 9, when two Bluetooth devices 1A and 1B are arranged at a distance of 3 meters and the distance to the source of the interference wave is Ln, the two Bluetooth devices 1A and 1B are connected to the two Bluetooth devices 1A and 1B. When the information communication method of the above-described embodiment was adopted, the distance Ln at which noise was generated in the Bluetooth device 1B was measured.
[0068]
Then, when the radio wave interference source is another Bluetooth device, there is no effect on the call between the devices 1A and 1B up to Ln = 0.3 m, and when the radio wave interference source is a wireless LAN, Ln It was confirmed that there was no effect on the communication between the devices 1A and 1B up to 0.5 meters.
[0069]
Also, as shown in FIG. 6, when the information communication method of this embodiment is adopted for the two Bluetooth devices 1A and 1B, when the distance between the Bluetooth device 1B and the radio wave interference source is fixed to 1 meter. When the distance Ls between the two Bluetooth devices 1A and 1B capable of performing a call without being affected by interference noise was measured, the following results were obtained.
[0070]
That is, it has been confirmed that, even when the radio wave interference source is any other Bluetooth device or wireless LAN, the communication between the devices 1A and 1B is not affected up to Ls = 25 meters. Then, at this time, it was confirmed by the Bluetooth protocol analyzer that retransmission was completed within the retransmission period when a packet error occurred.
[0071]
In the above embodiment, the DM3 packet is used and the audio buffering size is set to 120 bytes. However, as shown in the table of FIG. 5, other types of packets in the ACL link and the audio buffering size are used. Even if there is a difference in effect, it goes without saying that a better voice call can be realized as compared with the conventional voice data transmission using the SCO link.
[0072]
In the above embodiment, the case of a cordless telephone using time-series information as audio information has been described. However, the present invention is of course applicable to the case of isochronous communication of moving image information.
[0073]
【The invention's effect】
As described above, according to the present invention, the isochronous communication of time-series information such as voice information can be realized using Bluetooth even in a usage environment having a problem of radio wave interference. .
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of an information communication device according to the present invention.
FIG. 2 is a diagram illustrating an example of a system in which the information communication apparatus according to the embodiment is used.
FIG. 3 is a diagram for explaining a communication situation by the information communication apparatus of the embodiment.
FIG. 4 is a diagram for explaining a packet type used in a Bluetooth ACL link.
FIG. 5 is a diagram for describing the information communication device according to the embodiment.
FIG. 6 is a diagram for describing an effect of the information communication device according to the embodiment.
FIG. 7 is a diagram illustrating an example of radio wave interference in Bluetooth communication.
FIG. 8 is a diagram illustrating an example of radio wave interference in Bluetooth communication.
FIG. 9 is a diagram for explaining the influence of radio wave interference in Bluetooth communication when an SCO link is used.
FIG. 10 is a diagram for explaining the resistance of the Bluetooth module to radio wave interference.
[Explanation of symbols]
210 Audio Data Processing Unit 220 Wireless Module for Bluetooth

Claims (6)

A method for performing isochronous communication of time-series information such as voice information using Bluetooth,
The communication uses a packet of a predetermined packet type of an ACL (Asynchronous Connection Less) link,
An information communication method, comprising transmitting the time-series information for each of the predetermined information amounts at a predetermined transmission interval in consideration of the predetermined information amount and a packet retransmission duration. The information communication method according to claim 1,
As the predetermined packet type, a DM3 (Data Medium 3) type or a DH3 (Data High 3) type is used, and the predetermined information amount of the time-series information and the transmission are set such that the number of retransmissions becomes two or more. An information communication method, wherein an interval is determined. The information communication method according to claim 1,
When a packet error occurs, if retransmission is not completed within the retransmission continuation time, retransmission of the packet is stopped and transmission of the next packet is started. A transmission buffer for temporarily storing a predetermined amount of time-series information such as audio information for transmission,
For each time-series information of the predetermined amount of information from the transmission buffer, a packet of a predetermined packet type of a Bluetooth ACL (Asynchronous Connection Less) link is generated and transmitted to a wireless line, and transmitted through a wireless line. A wireless module for Bluetooth that receives incoming packets;
A reception buffer for receiving the time-series information of the predetermined amount of information included in the packet received by the wireless module, and temporarily storing the same for reproduction;
With
The information communication device, wherein the wireless module transmits the time-series information for each of the predetermined information amounts at a predetermined transmission interval in consideration of the predetermined information amount and a packet retransmission duration. The information communication device according to claim 4,
As the predetermined packet type, a DM3 (Data Medium 3) type or a DH3 (Data High 3) type is used, and the predetermined information amount of the time-series information and the transmission are set such that the number of retransmissions becomes two or more. An information communication device, wherein an interval is determined. The information communication device according to claim 4,
When the packet error occurs, if the retransmission is not completed within the retransmission continuation time, the control unit stops the retransmission of the packet and starts transmission of the next packet. apparatus.

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