JP2004207964A - Voatm communication system, voice coding decoding apparatus used for the same, and control method for selecting voice coding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a VoATM communication system capable of maintaining present communication to the utmost by reducing or avoiding an abnormality state of transfer of ATM cells of voice information. <P>SOLUTION: In each of a subscriber terminal and an in-station line concentrator connected opposite to each other via an ATM transmission path, a coding section codes voice information on the basis of a high rate code rule, and a voice information division section assembles the coded voice information into ATM cells together with code rule information and transmits the resulting cells to an opposite apparatus. A voice information reassembling section extracts the voice information and its code rule from the ATM cells received from the opposite apparatus. When a decoding section detects that the opposite apparatus uses a low rate code rule and detects that the arrival interval of the ATM cells from the opposite apparatus exceeds a prescribed time consecutively for a prescribed number of times through interval monitoring, the decoding section revises the code rule used by the coding section into a low rate code rule. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a VoATM communication system that encodes audio information using one of a plurality of encoding rules, assembles and communicates with ATM cells, an audio encoding / decoding device used therefor, and a method for controlling the selection of audio encoding. And about.
[0002]
[Prior art]
In an ATM (Asynchronous Transfer Mode) communication system, user information (multimedia information) to be transmitted is divided into cells (ATM cells) having a fixed octet length (1 octet = 8 bits (1 byte)). The network is being transferred. When transmitting voice information, the voice information is encoded according to a predetermined coding rule, then converted into ATM cells and transferred to an ATM network, and is sometimes referred to as a VoATM communication system.
[0003]
In this VoATM communication system, in the ATM device which is a constituent element of the ATM network, voice ATM cells coexist (compete) with other ATM cells. Therefore, depending on the use state, a congestion state is caused and the ATM cells cannot be transferred normally. (Cell discard) may occur. In this case, a phenomenon such as instantaneous interruption or disconnection of communication may occur in the entire ATM network, and the ATM network may fall into an unusable state. In addition, the communication system may use an ATM transmission line whose transmission band may be limited depending on installation environment conditions such as xDSL, for example. Normal transfer may not be performed. In order to cope with such a case, a technology that can reduce the number of ATM cells generated by switching a speech coding rule to a lower rate when an ATM cell transfer delay occurs due to congestion, thereby reducing the number of discarded cells. Has been proposed. (For example, refer to Patent Document 1.)
[Patent Document 1]
JP-A-5-56064 (page 2, FIG. 3)
[0004]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide means and a method for determining that an ATM cell transfer state is not normal due to congestion of an ATM network or band limitation of an ATM transmission line, and changing voice coding to a lower rate (reducing the number of generated ATM cells). By using means and a method different from the above-described conventional technology (the technology described in Patent Document 1), it is possible to reduce or avoid the abnormal state of the ATM cell transfer and maintain the current communication as much as possible. An object of the present invention is to provide a VoATM communication system, a voice coding / decoding device used for the same, and a voice coding selection control method.
[0005]
[Means for Solving the Problems]
The speech encoding / decoding apparatus according to claim 1 of the present invention is capable of converting speech information input from the outside into at least one of a first rate coding rule and a second rate coding rule lower than the first rate coding rule. Encoding means for encoding, and audio information encoded by the encoding means are divided into predetermined amounts, inserted into ATM cells together with the corresponding coding rule information, and sequentially transmitted to the opposite device via an ATM transmission line. An audio information dividing means for transmitting, and an ATM cell sequentially received from an opposite device via the ATM transmission line, wherein at least the first rate code rule and a second rate code rule lower than the first rate code rule are received. Voice information reassembly means for extracting voice information encoded by any of the above, and temporarily storing the voice information together with the corresponding coding rule information; and encoded voice information stored in the voice information reassembly means. Sequentially read, decode based on the corresponding coding rule information and output to the outside, and when the corresponding coding rule has a lower rate than the coding rule coded by the coding unit, A decoding means for instructing to perform encoding according to the rule, and an arrival time interval of ATM cells from a device opposed via the ATM transmission path received by the voice information reassembly means are monitored, and a predetermined number of consecutive times are taken. It is determined whether or not a predetermined time obtained from a specified interval time according to a coding rule to be performed and an allowable fluctuation time is exceeded. Interval monitoring means for instructing encoding with a lower rate coding rule.
[0006]
The speech encoding / decoding device according to claim 2 of the present invention is configured to convert speech information input from the outside according to at least one of a first rate coding rule and a second rate coding rule lower than the first rate coding rule. Encoding means for encoding, and audio information encoded by the encoding means are divided into predetermined amounts, inserted into ATM cells together with the corresponding coding rule information, and sequentially transmitted to the opposite device via an ATM transmission line. An audio information dividing means for transmitting, and an ATM cell sequentially received from an opposite device via the ATM transmission line, wherein at least the first rate code rule and a second rate code rule lower than the first rate code rule are received. Voice information reassembly means for extracting voice information encoded by any of the above, and temporarily storing the voice information together with the corresponding coding rule information; and encoded voice information stored in the voice information reassembly means. Sequentially read, decode based on the corresponding coding rule information and output to the outside, and when the corresponding coding rule has a lower rate than the coding rule coded by the coding unit, Decoding means for instructing to perform encoding according to the rule, and monitoring the accumulated amount of audio information temporarily accumulated in the audio information reassembly means, determines whether or not it is equal to or greater than a predetermined amount. A storage amount monitoring unit that instructs the coding unit to perform coding according to a coding rule having a lower rate than the current coding rule.
[0007]
According to a third aspect of the present invention, there is provided a VoATM communication system, comprising the voice encoding / decoding device according to the first or second aspect, and a subscriber premises apparatus for transmitting / receiving voice information to / from a housed telephone terminal. Item 1 or 2, comprising an intra-station terminating device for transmitting and receiving voice information to and from a housed circuit switch, and an ATM device, wherein the subscriber premises device and the An ATM transmission path for connecting the intra-station terminating devices and mutually transferring ATM cells.
[0008]
According to a fourth aspect of the present invention, there is provided a method of controlling voice encoding selection in a VoATM communication system in which two voice encoding / decoding devices according to the first aspect are oppositely connected via an ATM transmission line. In the control method, at the start of communication, both of the two audio encoding / decoding devices encode audio information according to the highest-rate encoding rule, and one of the audio encoding / decoding devices performs the other audio encoding and decoding. When it is detected that the inter-arrival time of the ATM cell from the encoding / decoding device has exceeded the predetermined time for a predetermined number of times in succession, the coding rule of the own device is set to a coding rule having a lower rate than the current coding rule, and When the speech encoding / decoding device detects that the coding rule of the one speech encoding / decoding device has a lower rate coding rule than the current coding rule, the coding rule of the device itself is changed to the corresponding low-rate code. Process A.
[0009]
According to a fifth aspect of the present invention, there is provided a method for controlling voice coding selection in a VoATM communication system in which two voice coding / decoding devices according to the second aspect are oppositely connected via an ATM transmission line. In the control method, at the start of communication, both of the two audio encoding / decoding devices encode audio information according to the highest-rate encoding rule, and one of the audio encoding / decoding devices performs the other audio encoding and decoding. When detecting that the temporary storage amount of audio information extracted from the ATM cell from the encoding / decoding device is less than a predetermined amount, the coding rule of the own device is set to a coding rule of a lower rate than the current coding rule, and When detecting that the coding rule of the one voice coding / decoding device has a lower rate coding rule than the current coding rule, the coding rule of the own device is set to the corresponding low rate. Sign rule I have a degree.
[0010]
According to a sixth aspect of the present invention, there is provided a method for controlling voice coding selection, wherein the first voice coding and decoding apparatus according to claim 1 and the second voice coding and decoding apparatus according to claim 2 perform ATM transmission. In the method for controlling the voice coding of a VoATM communication system which is oppositely connected via a path, when the communication is started, both the first and second voice coding / decoding devices code the voice information according to the highest rate coding rule. When the first voice encoding / decoding device detects that the arrival interval time of ATM cells from the second voice encoding / decoding device exceeds a predetermined time continuously for a predetermined number of times, The coding rule of the own device is set to a coding rule of a lower rate than the current coding rule, and the coding rule of the first voice coding / decoding device is lower than the current coding rule in the second voice coding / decoding device. When it detects that the code rule of the rate has been reached, The second coding and decoding device sets the temporary storage amount of the voice information extracted from the ATM cells from the first coding and decoding device to a certain value. When it is detected that the value is less than the fixed amount, the coding rule of the own device is set to a coding rule having a lower rate than the current coding rule, and the first voice coding / decoding device outputs the second voice coding / decoding device. When it is detected that the coding rule of (1) becomes a coding rule of a lower rate than the current coding rule, a step of setting the coding rule of the own device to the coding rule of the lower rate is included.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the outline of the present invention will be described. The present invention provides a VoATM communication system, which is a communication system for converting voice information into ATM cells and transferring the information, by always checking whether or not the ATM cell transfer state of a certain voice transfer path is normal, and congesting the ATM network or the bandwidth of the ATM transmission path. When the restriction determines that it is not normal, reduce the number of ATM cells generated by changing the voice coding to a lower rate to reduce or avoid abnormal conditions and maintain current communications as much as possible. It is possible to do.
[0012]
This will be described more specifically. In a VoATM communication system to which the present invention is applied, an intra-office terminal device accommodated in a circuit switch via a TDM transmission line, and a subscriber premises device accommodating a telephone terminal via a TDM transmission line include an ATM including an ATM device. They are connected to each other via a transmission line, and perform ATM cell conversion of voice information and its inverse conversion. A speech coding rule can be selected at the time of the conversion, and in a normal case, a high rate is used to give priority to speech quality. Using the fact that ATM cells of voice information are generated at regular intervals and transmitted to the opposing device, the receiving side also monitors the arrival intervals, thereby confirming that congestion in the ATM device or band limitation in the ATM transmission line has occurred. It is possible to detect. At this time, by switching the voice coding rule to a low rate, it is expected that the number of generated ATM cells for voice information is reduced, and congestion is reduced or band limitation is avoided.
[0013]
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a system configuration diagram showing an embodiment of a VoATM communication system according to the present invention, and shows only parts related to the present invention.
[0015]
In FIG. 1, a VoATM communication system of the present embodiment uses a circuit switch 50, a telephone terminal 10, and a TDM transmission line 70, which are conventional telephone communication systems, as they are, and provides an intra-office terminating device 40 on the station side, and a subscriber side. , The customer premises equipment 20 is additionally installed, and these are connected via the ATM transmission line 60. The intermediate ATM device 30 is a relay transmission device. The in-station terminating device 40 and the subscriber premises device 20 both store voice information transferred from the TDM transmission line 70, convert it to ATM cells using common means, and send it to the ATM transmission line 60; It has these reverse functions.
[0016]
FIG. 2 is a block diagram showing a detailed configuration example (first embodiment) of the intra-office terminal device 40 and the subscriber premises device 20. The intra-station terminating device 40 and the subscriber premises device 20 respectively include coding sections 41 and 21, voice information dividing sections 42 and 22, voice information reassembling sections 43 and 23, decoding sections 44 and 24, and interval monitoring. Parts 45 and 25 are provided. The basic configuration and operation principle are the same for both the intra-office terminal device 40 and the customer premises device 20, and therefore the intra-office terminal device 40 will be described as an example. Regarding the customer premises equipment 20, the code number of each functional block and the transmission direction of the transmission / reception signal with the outside may be read.
[0017]
In the intra-office terminal device 40, the information transferred in the down direction from the circuit switch 50 to the telephone terminal 10 is encoded by the encoding unit 41 of the voice information received from the TDM transmission line 70. The coded voice information is accumulated in a fixed amount, converted into ATM cells by the voice information dividing unit 42 at a fixed interval, and transmitted to the ATM transmission line 60.
[0018]
As for the information transferred from the telephone terminal 10 to the circuit switch 50 in the upward direction, the voice information reassembly unit 43 extracts voice information from the ATM cells received from the ATM transmission line 60. The ATM cell contains information indicating the audio coding rule of the audio information, and the decoding unit 44 returns the original audio information to the TDM transmission line 70 based on the information. . In parallel with the above operation, the arrival interval of ATM cells is observed by the interval monitoring unit 45.
[0019]
Although not shown, the interval monitoring unit 45 detects the input of the ATM cell to the voice information reassembly unit 43 and the unit for measuring the interval time from the previous input time of the ATM cell to the present input time. Means for determining whether or not the interval time has exceeded a predetermined time; means for counting the number of times the interval time has continuously exceeded the predetermined time; and determining whether or not the counted number has exceeded a predetermined number of times. Means for determining that the state of the ATM cell transfer is not normal when the number exceeds the limit.
[0020]
The selection of the encoding rule in the encoding unit 41 is performed based on the observation result of the arrival interval of the ATM cell in the interval monitoring unit 45 and the information of the speech encoding rule included in the ATM cell in the decoding unit 44. Is determined.
[0021]
In the VoATM communication system according to the present invention, it is assumed that the voice coding rule of a certain voice channel is operated in accordance with the uplink and downlink directions, and the coding rule selected by the coding unit 41 is used by the decoding unit 44. In principle, it follows the specified speech coding rules.
[0022]
FIG. 6 shows a configuration example of an ATM cell corresponding to the speech coding rule. The figure (A) is 64 kb / S-PCM (hereinafter sometimes abbreviated as 64 kPCM or simply PCM, PCM: Pulse Code Modulation), and the figure (B) is 32 kb / S-ADPCM (hereinafter referred to as 32 kADPCM). A cell structure of ADPCM (Adaptive Difference Pulse Code Modulation (adaptive difference PCM)) (only a part related to the present invention), which may be abbreviated, is shown.
[0023]
The ATM cell has a fixed length of 53 octets (1 octet = 8 bits (1 byte)), and is composed of a 5-octet ATM header and a 48-octet payload (user information). The coding rate can be identified by a value of UUI (User-to-User Indication: display between users (5 bits)) set over a two-octet area. For example, ITU-TI. If the Profile 13 defined in 366.2 is used, it can be recognized as 64 kPCM when UUI = 0 to 7 and 32 kADPCM when UUI = 8 to 15.
[0024]
In the case of 64 kPCM (partial diagram (A)), PCM data 1 to 40 in 8-bit units are arranged in octets.
[0025]
In the case of 32k ADPCM (split diagram (B)), each of the ADPCM data 1 to 80 in 4-bit units is arranged two by two in octets.
[0026]
Next, the operation of the present embodiment will be described with reference to FIG. 3 together with FIGS. 1, 2, and 6 described above. FIG. 3 is a diagram showing an operation flow of the intra-office terminal device 40 and the subscriber premises device 20. Both the intra-office terminal device 40 and the subscriber premises device 20 operate according to the same flow. Since it is not known whether there is a factor in which the transfer of the ATM cell cannot be performed normally in the up direction or the down direction, both the intra-office terminal device 40 and the subscriber premises device 20 need to use FIG. Deploy the operation functions shown.
[0027]
When a certain voice transfer path is set and communication is started (step S100 in FIG. 3), the coding unit 41 of the intra-station terminal device 40 always selects a high-rate (64 kPCM) voice coding rule to code voice information. I do. In accordance with this, the decoding unit 24 of the subscriber premises device 20 detects that it is a high-rate speech coding rule, and the coding unit 21 also selects the high rate. Normally, in this state, a high rate is used in both the upstream and downstream directions until the end of communication (step S101).
[0028]
In this example, the audio information signal on the TDM transmission line 70 which is input to and output from the encoders 41 and 21 and the decoders 44 and 24 is a signal encoded according to the audio code rule of 64 kPCM. If the audio information signal transferred on the ATM transmission line 60 has this high-rate (64 kPCM) audio coding rule, the coding units 41 and 21 and the decoding units 44 and 24 do not convert the coding rule, and Pass through. Of course, the audio information signal on the TDM transmission line 70 may be other than 64 kPCM. In that case, the encoding units 41 and 21 and the decoding units 44 and 24 perform appropriate conversion of the coding rule even when using a high-rate (64 kPCM) voice coding rule for the ATM transmission line 60.
[0029]
ATM cells transferred through the ATM device 30 and the ATM transmission line 60 are transferred at regular intervals. For example, ITU-TG. When using the PCM defined in ITU-T G.711, According to 366.2, transfer of ATM cells occurs every 5 ms.
[0030]
However, when the transfer of the ATM cells is not normally performed due to the congestion of the ATM device 30 or the band limitation of the ATM transmission line 60, for example, when the transfer of the ATM cells is not normally performed in the upstream direction, this is determined in the station. The interval monitoring unit 45 provided in the terminal device 40 detects that the arrival interval of the ATM cells to the voice information reassembly unit 43 is not constant (as determined by a predetermined value) (steps S102 and S103).
[0031]
Here, a specific example of the ATM cell interval monitoring by the interval monitoring unit 45 will be described. The case where the prescribed transfer interval of the ATM cell is 5 ms and the allowable burst time is 0.72 ms will be described as an example. The interval monitoring unit 45 monitors the ATM cells arriving at the voice information reassembly unit 43 and measures the arrival intervals. Until the result of the time measurement is a predetermined threshold value, that is, 5 ms + 0.72 ms = 5.72 ms, it is determined to be OK (good). If the number exceeds a predetermined threshold value (5.72 ms), the number of times that the number of times continuously exceeds is counted. If the number of times exceeds a predetermined number of times (for example, three times), ATM cell transfer is normally performed. It is determined that it is gone.
[0032]
The predetermined number of times (the number of times exceeding the threshold) should be set so that the amount of audio information stored in the burst absorption buffer (detailed description will be given later) of the audio information reassembly unit 43 does not exceed its capacity. Is desirable. Otherwise, the sound missing time of the call may be long, and there is a sense of discomfort in the service. Of course, if you do not consider the service, you can set a longer (larger number).
[0033]
In response to this result, the encoding unit 41 of the intra-station terminating device 40 switches the speech coding rule from the high rate up to the low rate (32 kADPCM). Then, the decoding unit 24 of the subscriber premises apparatus 20 detects that the speech coding rule is a low-rate speech coding rule (step S102), and also switches the coding unit 21 to the low-rate. As a result of this operation, a low rate is selected in both the up direction and the down direction (step S104).
[0034]
For example, PCM (64kPCM) has been used so far, and when it is detected that the transfer of the ATM cell is not normal, the switching to the low rate is performed according to ITU-TG. If the user selects the 32k ADPCM defined by ITU-T G.726. According to 366.2, transfer of ATM cells occurs every 10 ms. This result indicates that the number of generated ATM cells has been reduced (halved).
[0035]
As a result of the above operation, the interval monitoring unit 45 of the intra-station terminating device 40 detects that the transfer of the ATM cell is not normally performed in the upstream direction. As a result, a low-rate speech coding rule is selected in both the upstream and downstream directions. Therefore, the number of generated ATM cells is reduced. As a result, it is possible to reduce the congestion state in the ATM device 30 or to avoid the band limitation in the ATM transmission line 60, and to maintain the current communication as much as possible.
[0036]
Contrary to the case described above, when the interval monitoring unit 25 of the subscriber premises apparatus 20 detects that the transfer of the ATM cell is not normally performed in the downstream direction, the same operation as described above is performed. A low-rate speech coding rule is selected in the downlink direction, and it is possible to reduce the congestion state in the ATM device 30 or to avoid the band limitation in the ATM transmission line 60, and to maintain the current communication as much as possible. Will be possible.
[0037]
In this way, once the time reaches 32 kADPCM (= 10 ms interval), the state is maintained until the call ends. Thereafter, once the call is hung up and redialed, as shown in FIG. 3, the call is started again at 64 kPCM (= 5 ms interval).
[0038]
Next, another embodiment of the present invention will be described.
[0039]
FIG. 4 is a block diagram showing a detailed configuration example (second embodiment) of the intra-office terminal device 40 and the subscriber premises device 20. The intra-station terminating device 40 and the subscriber premises device 20 include coding units 41 and 21, voice information dividing units 42 and 22, voice information reassembling units 43 and 23, and buffer monitoring units 46 and 26, respectively. ing. The difference between the intra-office terminal device 40 and the subscriber premises device 20 shown in FIG. 4 from the intra-office termination device 40 and the subscriber premises device 20 shown in FIG. 2 is that an interval monitoring unit is used as means for monitoring the arrival interval of ATM cells. The point is that buffer monitoring units 46 and 26 are provided instead of 45 and 25.
[0040]
FIG. 5 shows a configuration example of the audio information reassembly units 43 and 23 monitored by the buffer monitoring units 46 and 26. The voice information reassembly units 43 and 23 respectively include interface units 431 and 231 for controlling the interface with the ATM transmission line 60, reassembly units 432 and 232 for extracting voice information from ATM cells, and bursts for temporarily storing voice information. It has absorption buffers 433 and 233.
[0041]
Since the basic configuration and operation principle of the voice information reassembly unit 43 and the voice information reassembly unit 23 are the same, the voice information reassembly unit 43 of the intra-office terminal device 40 will be described as an example. Regarding the voice information reassembly unit 23 of the customer premises equipment 20, the code numbers of the respective functional blocks are shown in parentheses, so that they may be replaced.
[0042]
The voice information reassembly unit 43 (23) receives the ATM cell input from the ATM device 30 via the interface unit 431 (231), extracts the original information by the reassembly unit 432 (232), and At 433 (233), original voice information and encoded information (PCM / ADPCM identification information) are simultaneously stored. When two cells (= 80 bytes) are accumulated in a burst absorption buffer (hereinafter sometimes abbreviated as a buffer), one byte is read from the buffer at a time.
[0043]
When the encoding rule is 64 kPCM, the input ATM cell is at 5 ms intervals, writing to the buffer is 40 bytes / 5 ms, and reading is 1 byte / 125 μs.
[0044]
When the coding rule is 32 kADPCM, the input ATM cells are at intervals of 10 ms, and the writing to the buffer is changed to 40 bytes / 10 ms, and the reading is changed to 1 byte / 250 μs.
[0045]
This is because the amount of information required by the decoding unit 440 (240) is 8 bits / 125 μs for 64 kPCM and 4 bits / 125 μs for 32 kADPCM.
[0046]
As another configuration example, a 32 k ADPCM → 64 kPCM conversion unit is provided at the next stage of the reassembly unit 432 (232), and all the information is unified to 64 kPCM and accumulated in the burst absorption buffer 433 (233). There are ways. In this case, only 8-bit audio information is stored in the buffer, and reading can be unified at 8 bits / 125 μs.
[0047]
Next, the operation of the buffer monitoring units 46 and 26 will be described. Since the basic configurations and operating principles of the buffer monitoring unit 46 and the buffer monitoring unit 26 are the same, the buffer monitoring unit 46 of the intra-station terminating device 40 will be described here as an example. Regarding the customer premises equipment 20, the code numbers of the respective functional blocks are shown in parentheses, so that they may be replaced.
[0048]
The voice information reassembly unit 43 (23) extracts voice information from the ATM cell input from the ATM transmission line 60, and as a result, the information corresponding to the extracted voice information is stored in the burst absorption buffer 433 (233). The information is sequentially passed to the decoding unit 44 (24). Since the next ATM cell should arrive so that the accumulated amount falls within a certain range of the buffer, the accumulated amount is observed (monitored) by the buffer monitoring unit 46 (26), so that the ATM device 30 or the ATM transmission is performed. It is possible to detect that the path 60 has not been able to normally transfer the ATM cell.
[0049]
Here, a specific example of monitoring the storage amount by the buffer monitoring unit 46 (26) will be described. The burst absorption buffer 433 (233) sets a state where voice information (80 bytes) for two ATM cells is always stored as a standard (normal) state. If the storage amount is smaller than this, the burst tolerance becomes worse (for example, when the ATM cell transmission interval is 5 ms, the prescribed allowable burst time is 0.72 ms). If the storage amount is larger than this, the delay between End and End is reduced. Becomes undesirably large in terms of service.
[0050]
The buffer monitoring unit 46 (26) monitors the accumulated amount of audio information in the burst absorption buffer 433 (233) of the audio information reassembly unit 43 (23), and when the remaining audio information becomes about 10 bytes, the ATM cell Is not transferred normally, and instructs the encoding unit 42 (22) to perform encoding according to a low-rate encoding rule.
[0051]
Note that the other blocks (encoding unit, decoding unit, and the like) and the overall operation of the intra-office terminal device 40 and the subscriber premises device 20 in the second embodiment are the same as those in the first embodiment (FIG. 1 to 3), detailed description is omitted.
[0052]
In the first and second embodiments described above, the same means, ie, the same interval, is used as the means for monitoring the arrival intervals of ATM cells between the intra-office terminal device 40 and the subscriber premises device 20. Only one of the monitoring units 45 and 25 and the buffer monitoring units 46 and 26 is employed. However, the present invention is not limited to this, and different means can be adopted between the intra-office terminal device 40 and the subscriber premises device 20. That is, the interval monitoring unit 45 is provided in the intra-office terminal device 40 and the buffer monitoring unit 26 is provided in the subscriber premises device 20, or the buffer monitoring unit 46 is provided in the intra-office termination device 40 and the interval monitoring is provided in the subscriber premises device 20. A part 25 can be provided.
[0053]
Although only two types of coding rules, that is, a high-rate 64 kPCM and a low-rate 32 kADPCM, have been described as the coding rules processed by the coding units 41 and 21 and the decoding units 44 and 24, the present invention is not limited to this. Without using three or more different coding rules with different rates. For example, a coding rule called CS-ACELP defined in ITU-T I366.2 is a coding rule with a lower rate than 32 kADPCM. When this is used, the ATM cell interval becomes 20 ms, and the number of transferred ATM cells can be reduced more efficiently than 32 kADPCM.
[0054]
【The invention's effect】
According to the present invention, when congestion or band limitation occurs in an ATM transmission section, control by human intervention by a maintenance person or the like becomes unnecessary, and reduction or avoidance of the trouble can be expected. As a result, even if a problem occurs in the ATM transmission section, it is possible to try to maintain the current communication as much as possible without immediately turning off the line. At this time, no special hardware is required because only the arrival interval of the ATM cells is measured using the speech code rule information contained in the ATM cells input from the ATM transmission line as an expected value.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing one embodiment of a VoATM communication system of the present invention.
FIG. 2 is a block diagram showing a first embodiment of an intra-office terminal device and a subscriber premises device of the present invention.
FIG. 3 is an operation flowchart of an in-station terminal device and a subscriber premises device.
FIG. 4 is a block diagram showing a second embodiment of the intra-station terminating device and the subscriber premises device of the present invention.
FIG. 5 is a block diagram showing a configuration example of a voice information reassembly unit.
FIG. 6 is a diagram illustrating a configuration example of an ATM cell corresponding to a speech coding rule.
[Explanation of symbols]
10 telephone terminals
20 subscriber premises equipment
30 ATM equipment
40 station termination equipment
50 circuit exchange
21, 41 encoding unit
22, 42 voice information division unit
23, 43 Voice information reassembly unit
24,44 decoding unit
25, 45 interval monitoring unit
26, 46 Buffer monitoring unit
233,433 burst absorption buffer

Claims (6)

Coding means for coding audio information input from the outside according to at least one of a first rate coding rule and a second rate coding rule lower than the first rate coding rule;
Voice information dividing means for dividing the voice information coded by the coding means into predetermined amount units, inserting it into ATM cells together with the corresponding coding rule information, and sequentially transmitting the same to an opposing device via an ATM transmission line;
ATM cells are sequentially received from an opposite device via the ATM transmission line, and are coded according to one of the at least first rate coding rule and a lower rate second rate coding rule. Voice information reassembly means for extracting voice information and temporarily storing it together with the corresponding coding rule information;
The encoded audio information stored in the audio information reassembly unit is sequentially read, decoded and output to the outside based on the corresponding encoding rule information, and a code whose corresponding encoding rule is encoded by the encoding unit. A decoding unit that instructs the encoding unit to perform encoding according to a corresponding encoding rule when the rate is lower than the encoding rule;
The voice information reassembly unit monitors the arrival interval time of ATM cells from the opposite device via the ATM transmission path received by the voice information reassembly means, and allows the specified interval time according to the corresponding coding rule for a predetermined number of times. It is determined whether or not a predetermined time obtained from the fluctuation time is exceeded, and when the predetermined time is continuously exceeded a predetermined number of times, the coding means is instructed to perform coding with a coding rule of a lower rate than the current coding rule. A speech encoding / decoding device comprising: an interval monitoring unit. Coding means for coding audio information input from the outside according to at least one of a first rate coding rule and a second rate coding rule lower than the first rate coding rule;
Voice information dividing means for dividing the voice information coded by the coding means into predetermined amount units, inserting it into ATM cells together with the corresponding coding rule information, and sequentially transmitting the same to an opposing device via an ATM transmission line;
ATM cells are sequentially received from an opposite device via the ATM transmission line, and are coded according to one of the at least first rate coding rule and a lower rate second rate coding rule. Voice information reassembly means for extracting voice information and temporarily storing it together with the corresponding coding rule information;
The encoded audio information stored in the audio information reassembly unit is sequentially read, decoded and output to the outside based on the corresponding encoding rule information, and a code whose corresponding encoding rule is encoded by the encoding unit. A decoding unit that instructs the encoding unit to perform encoding according to a corresponding encoding rule when the rate is lower than the encoding rule;
The audio information reassembly means monitors the amount of audio information temporarily stored, determines whether the amount is equal to or more than a predetermined amount, and when the amount is less than the predetermined amount, the encoding means has a lower rate than the current coding rule. And a storage amount monitoring unit that instructs to perform encoding in accordance with the following coding rule. A subscriber premises device configured with the voice encoding / decoding device according to claim 1 or 2, and transmitting / receiving voice information to / from a housed telephone terminal;
An intra-station terminating device which is constituted by the voice encoding / decoding device according to claim 1 or 2, and transmits / receives voice information to / from a housed circuit exchange,
A VoATM communication system comprising an ATM device, comprising: an ATM transmission path for connecting the subscriber premises device and the intra-office terminal device and mutually transferring ATM cells. 2. A method for controlling voice coding selection in a VoATM communication system in which two voice coding / decoding devices according to claim 1 are oppositely connected via an ATM transmission line.
At the start of communication, both of the two audio encoding / decoding devices encode audio information according to the highest rate coding rule,
When one of the voice encoding / decoding devices detects that the arrival interval time of the ATM cell from the opposite voice encoding / decoding device exceeds a predetermined time continuously for a predetermined number of times, the code of its own device is detected. Let the rule be a lower rate code rule than the current one,
When the other speech coding / decoding device detects that the coding rule of the one speech coding / decoding device has a lower rate than the current coding rule, the coding rule of the own device is set to the corresponding low coding rule. A method for controlling speech coding selection, characterized by a rate coding rule. A method for controlling voice coding selection in a VoATM communication system in which two voice coding / decoding devices according to claim 2 are connected to each other via an ATM transmission line.
At the start of communication, both of the two audio encoding / decoding devices encode audio information according to the highest rate coding rule,
When one of the voice encoding / decoding devices detects that the temporary storage amount of the voice information extracted from the ATM cell from the opposite voice encoding / decoding device is less than a predetermined amount, the device determines its own device. The coding rule is a lower rate coding rule than the current coding rule,
When the other speech coding / decoding device detects that the coding rule of the one speech coding / decoding device has a lower rate than the current coding rule, the coding rule of the own device is set to the corresponding low coding rule. A method for controlling speech coding selection, characterized by a rate coding rule. A first voice coding / decoding device according to claim 1 and a second voice coding / decoding device according to claim 2 are connected to each other via an ATM transmission line to select a voice coding in a VoATM communication system. In the control method,
At the start of communication, both the first and second speech encoding / decoding devices encode speech information according to the highest rate coding rule,
When the first voice encoding / decoding device detects that the arrival interval time of ATM cells from the second voice encoding / decoding device exceeds a predetermined time continuously for a predetermined number of times, the code of its own device is detected. The rule is a coding rule having a lower rate than the current coding rule, and the coding rule of the first voice coding and decoding device is a coding rule having a lower rate than the current coding rule. Is detected, the coding rule of the own device is set as the corresponding low-rate coding rule,
When the second audio encoding / decoding device detects that the temporary storage amount of the audio information extracted from the ATM cell from the first audio encoding / decoding device is less than a predetermined amount, The coding rule is a coding rule having a lower rate than the current coding rule, and the first speech coding / decoding device has a coding rule of a rate lower than the current coding rule in the second speech coding / decoding device. A method for controlling speech coding selection, characterized in that when a rule is detected, the coding rule of the own device is set to the corresponding low-rate coding rule.

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