JP5647538B2 - COMMUNICATION METHOD, MEDIA GATEWAY, AND ATM TERMINAL DEVICE - Google Patents

Description

  The present invention relates to an ATM (Asynchronous Transfer Mode) system, and in particular, a communication method in an ATM cell transmission system that converts communication data such as voice data into ATM cells and sends it to an ATM network, and a media gateway used in the method. And an ATM terminator.

  Conventionally, ISDN (Integrated Services Digital Network) services have been provided (see, for example, Non-Patent Documents 1 and 2). ISDN is a digital communication network that is standardized by the International Telecommunications Union (Telecommunications Sector) (ITU-T) and handles telephones, faxes, and data communications in an integrated manner. In order for a telecommunications carrier to provide an ISDN (voice) service that is a high-quality voice band communication using an existing telephone line, it is necessary to have many facilities such as a subscriber exchange. A conventional transmission system using such an existing telephone line will be described with reference to FIG.

  FIG. 8 shows a connection configuration in a conventional apparatus when providing an ISDN (voice) service. Hereinafter, a technique using the transmission system 800 illustrated in FIG. As shown in FIG. 8, in the user's home H, a terminal called a terminal adapter (TA) 809 is connected in addition to the line terminating device 803, and a telephone, G4 FAX or personal computer is further connected to the TA 809 for use. Is done. In FIG. 8, an analog telephone 810 is connected to TA 809 as an example.

In this example, a plurality of subscriber stations (three in FIG. 1) are opened in a plurality of subscriber station buildings MB, respectively, and a large number of users are accommodated by one subscriber switch 804. In addition, in FIG. 8, a mode that one user was accommodated was illustrated.
A subscriber exchange 804 in the subscriber station building MB that accommodates the user's home H and a line terminating device 803 in the user's home H are connected by a subscriber line ML. The user home H is connected to another user home H via a relay station. Here, a relay station is established in the relay station building IB, and the relay switch 801 of the relay station building IB and the subscriber switch 804 of the subscriber station building MB are connected by a relay line IL.

FIG. 9 is a protocol stack of a control unit for providing an ISDN (voice) service (see Non-Patent Document 1).
Protocols between the TA 809 and the line termination device 803 are RJ45 and ISDN user / network interface 102 denoted by reference numeral 101 from the lower layer.
Protocols between the line terminating device 803 and the subscriber exchange 804 are the TCM transmission 103 and the ISDN user / network interface 102 from the lower layer. Note that TCM (Time Compression Modulation) transmission is a so-called ping-pong method.
Protocols between the subscriber exchange 804 and the relay exchange 801 are the SDH 104, the message transfer unit (user transfer unit) 105, and the ISDN user unit 106 from the lower layer. SDH (Sinchronous Digital Hierarchy) 104 is a synchronous digital high arch.

FIG. 10 is a call connection sequence in the apparatus of the transmission system 800 of the prior art A.
Here, for example, suppose that user A makes a call with user B as the other party, and analog telephones 810 respectively used by user A and user B are arranged on the left and right sides in FIG. When the number dialed from the analog telephone 810 on the left side of FIG. 10 is input to the terminal adapter (TA) 809 by the call from the user A (201), the TA 809 at the user A's home is connected to the user via the line terminating device 803. Call setting processing is performed on the subscriber exchange 804 accommodating A (202). The subscriber exchange 804 sends an address notification to the subscriber exchange 804 that accommodates the user B via the relay exchange 801 (203). Then, the subscriber exchange 804 performs call setting processing for the TA 809 via the line terminating device 803 at the user B home (204). The TA 809 makes a call on the analog telephone 810 at the user B's home and notifies the analog telephone 810 at the user A's home that the call is being made (205). When user B responds normally with analog telephone 810, a response signal is notified to analog telephone 810 at user A's home (206). As a result, the user A and the user B can talk (207). Thereafter, when the call is disconnected from the user A, the analog telephone 810 at the user B's home is notified (208). At this time, the subscriber exchange 804 that accommodates the user A issues an instruction to release the call to the TA 809 via the line terminating device 803 of the user A home (209), whereas the TA 809 of the user A home releases the call. Completion is returned (210). On the other hand, TA 809 in user B's home gives an instruction to release the call to subscriber exchange 804 that accommodates user B via line terminating device 803 (209), and subscriber exchange 804 completes the release. Reply (210).

  Here, in order to make an end-to-end ISDN connection using the method of the prior art A, a relay exchange 801 is required for the relay station, and a subscriber exchange 804 is required for the subscriber station, and the subscriber exchange of the subscriber station is also required. Since there are areas where the number of users accommodated in 804 is small, accommodation efficiency is poor and high equipment costs are required. Therefore, in order to provide an ISDN (voice) service at a lower cost by using an existing ATM network, a telecommunications carrier implements a method according to Patent Document 1 (hereinafter referred to as Conventional Technology B). Was introduced.

  Prior art B is not an accommodation form in which the subscriber switch 804 is installed in the subscriber station building MB as in the prior art A, but an ATM network in a part of the communication path as in the ATM cell transmission system 900 shown in FIG. 905 is used. As shown in FIG. 11, this ATM cell transmission system 900 is a media gateway (switch connection type) that can be connected to an existing telephone network (a subscriber switch 904 connected by a switch interface and a public telephone network (not shown)). Media gateway) 902 and an ATM termination device 903 that terminates the ATM network 905 in accordance with the protocol of the exchange-connected media gateway 902.

  The exchange-connected media gateway 902 uses an AAL type 2 (hereinafter simply referred to as AAL2 or type 2) in an ATM adaptation layer (hereinafter referred to as an AAL layer or simply referred to as AAL). There is also a device that executes the protocol processing. This is illustrated as an exchange-connected media gateway (AAL2). AAL type 2 is an ITU-T recommendation I.D. It is defined in 363.2. As shown in FIG. 11, the exchange-connected media gateway 902 includes an exchange interface unit 906, an ATM interface unit 907, and a voice processing unit 908.

  The exchange interface unit 906 terminates the SDH and performs voice processing on the B channel, D channel, and control signal (SG channel) included in the ISDN basic group (BRI) interface sent from the subscriber exchange 904. Output to the unit 908.

  The ATM interface unit 907 terminates the ATM, and voices the B channel, D channel, and control signals (ATM terminator control, BRI control) included in the ISDN basic group (BRI) interface sent from the ATM terminator 903. The data is output to the processing unit 908.

  The voice processing unit 908 performs processing by separating the B channel, D channel, and control signal (BRI control, SG channel) output from the exchange interface unit 906, and performs processing on the B channel, D channel, and control signal (ATM terminator). Control, BRI control) to the ATM interface unit 907.

  Also, the voice processing unit 908 separates the B channel, D channel, and control signals (ATM terminator control, BRI control) output from the ATM interface unit 907, and processes the B channel, D channel, and control signal. (SG channel) is output to the exchange interface unit 906.

The audio processing unit 908 includes a Bch processing unit (B channel processing unit) 911, a Dch processing unit (D channel processing unit) 912, and a control signal processing unit 913 as control units.
The Bch processing unit 911 may include an EC processing unit (echo cancellation processing unit) 914 as an echo canceller function (for the subscriber side / exchange side). In this case, the EC processing unit 914 removes the echo of the Bch sound according to the conditions such as the communication distance and the processing content of the Dch processing unit 912 (echo cancellation processing).

  The ATM terminator 903 is installed in the user's home H, and superimposes the ISDN basic group (BRI) interface on the ATM by the control signal from the exchange-connected media gateway 902 to terminate the ATM network 905.

  FIG. 12 shows a protocol stack of the control unit in the exchange-connected media gateway 902. The exchange-connected media gateway 902 has a function conforming to the CO-IWF (Central Office Interworking Function) of “Loop Emulation Service Using AAL2 (LES)” defined by the ATM Forum. Connected to the subscriber exchange 904.

  The protocol between the ATM terminator 903 and the terminal adapter 909 is the same as that of the prior art A, so that the telephone, FAX, TA, etc. in the user's home H can be used as they are.

  The protocol between the subscriber switch 904 and the ATM terminating device 903 is not changed in the ISDN user / network interface 102, and the lower layers are ATM 110, ATM adaptation layer type 2 indicated by reference numeral 111, and circuit emulation from the bottom. The service protocol 112 is obtained.

  Next, a connection configuration using the conventional technique B will be described with reference to FIG. 13 (refer to FIG. 8 as appropriate) while comparing with the conventional technique A. In the user's home H, an ATM terminator 903 is installed instead of the line terminator 803 (FIG. 8). Only by this change, the user's home H can be connected to the ATM network 905. A dark fiber F is used to connect between the user's home H and the ATM network 905 of the subscriber station building MB. Here, no exchange is installed in the subscriber station building MB. Instead, the subscriber switch 904 is installed only in the relay station building IB, and the users of the plurality of subscriber station buildings MB are accommodated in the subscriber switch 904 of the relay station building IB. Containment can be realized. In the relay station building IB, an exchange-connected media gateway 902 (hereinafter, sometimes referred to as an exchange-connected MG or simply MG) is installed by connecting to the subscriber exchange 904. As a result, it is possible to accommodate users in the subscriber exchange 904 of the relay station building IB, and it is possible to provide an ISDN (voice) service at a lower cost than the prior art A.

  FIG. 14 is a call connection sequence of each device in the ATM cell transmission system 900 of the prior art B. For example, an analog telephone 910 used by the user C is arranged on the left side in FIG. 14 assuming that the user C who installed the ATM terminating device 903 makes a call with the user B who installed the line terminating device 803 as the other party. Assume that the analog telephone 810 used by the user B is arranged on the right side in FIG. In this case, when a number dialed from the analog telephone 910 is input to the terminal adapter (TA) 909 by a call from the user C (201), the TA 909 of the user C's home is connected to the exchange connection type via the ATM terminator 903. Call setting processing is performed on the MG 902 (202). This exchange-connected MG 902 notifies the address to the subscriber exchange 904 that accommodates the users B and C (203). Hereinafter, the processes 204 to 207 are the same as those in FIG. Thereafter, when the call is disconnected from the user C, the analog telephone 810 of the user B's home is notified (208). At this time, the subscriber exchange 904 that accommodates the users B and C issues an instruction to release the call to the TA 909 via the exchange-connected MG 902 and the ATM terminating device 903 in the user C home (209). TA909 of user C's home returns a release completion reply (210). On the other hand, TA 809 in user B's home issues an instruction to release the call to subscriber exchange 904 that accommodates users B and C via line terminating device 803 (209), and subscriber exchange 904 releases it. Completion is returned (210). Note that a call connection process can be performed in a similar sequence for a call between users who have installed the ATM terminating device 903.

JP 2003-152790 A

"INS Net Service Interface", Volume 1-6, [online], March 28, 2008, NTT West, [Search January 20, 2011], Internet <URL: http: // www .ntt-west.co.jp / denwa / support / tech / tech_1.html> “IP Communication Network Service Interface-FLET'S Series”, 1st volume, 11th edition, [online], July 1, 2010, NTT East, [Search January 20, 2011], Internet <URL : http: //flets.com/pdf/ip-int-flets-1.pdf>

  The ATM cell transmission system 900 of the prior art B can reduce the cost as the number of facilities by consolidating the subscriber switch 904 in the relay station building IB as shown in FIG. However, since the exchange-connected media gateway 902 used in the ATM cell transmission system 900 uses the ATM adaptation layer type 2 when mapping ISDN onto the ATM, it requires a high protocol processing capability.

  In ATM adaptation layer type 2 (AAL2), unlike variable type 1 (AAL1), variable speed speech coding (VBR: Variable Bit Rate) is considered. For this reason, AAL2 performs variable length short packetization on voice data and multiplexes packets of a plurality of channels into one cell. Specifically, the exchange-connected media gateway 902 uses the ISDN user / network interface 102 to transmit B-channel communication data, D-channel communication data included in the basic (BRI) interface output from the subscriber exchange 904, and When the control signal is received, as shown in FIG. 15, in the ATM adaptation layer type 2 denoted by reference numeral 121, the information received for each user in the upper layer is converted into the B channel voice packet (Bch 116) and the D channel communication. Separation processing 111-2 that separates the packet (Dch 117) and the control signal 118 is performed. Further, in AAL2, a cell that multiplexes voice packets (Bch 113, 114, 115) of each B channel of a plurality of (three in the example of FIG. 15) users received in the upper layer into a payload of one ATM cell. Multiplexing processing 111-1 is performed. In this case, three CPS (Common Part Sublayer) packets of variable length corresponding to three users are stored in the 48-byte payload.

  For this reason, both the exchange-connected media gateway 902 and the ATM terminating device 903 need to use components (processors or the like) with high processing capability, and the cost of the entire device is high for each device.

  Therefore, the present invention has been made in view of the above circumstances, and provides a communication method, a media gateway, and an ATM termination device that can reduce the cost of each device constituting an ATM cell transmission system. Let it be an issue.

In order to solve the above-mentioned problems, a communication method according to the present invention includes an ATM terminating device that terminates an ATM network and is installed at a user's home, a subscriber exchange connected to a public telephone network, and an SDH (Synchronous Digital Hierarchy). And a media gateway that terminates the ATM network and is communicably connected to the subscriber exchange and the ATM network, and converts communication data into ATM cells and transmits the ATM data to the ATM network. A method in which the media gateway is configured such that, for each ATM terminating device , the BDN communication data included in the basic (BRI) interface output from the subscriber exchange at the ISDN user / network interface, In the reception step of receiving communication data and control signals as BRI information, For each ATM terminator, and performing protocol processing by AAL type 1, and the adaptation layer processing step of adapting the BRI information thus received to the ATM layer, in the upper layer than the AAL layer, for each of the ATM terminator A separation step of separating the received BRI information into the communication data of the B channel, the communication data of the D channel, and the control signal, and the separation for each ATM terminating device in a layer higher than the AAL layer. A mapping step for superimposing communication data and control signals on the payload of an ATM cell using a mapping protocol predetermined for the basic interface, and the BRI information is superimposed for each ATM terminating device in the ATM layer. An ATM cell creation step for creating the ATM cell by adding an ATM header to the payload. And-up, for each of said ATM terminating unit, the created ATM cell running and an output step of outputting to the ATM network, the ATM termination device, via the ATM network from the media gateway, The method includes performing a reception step of receiving an ATM cell on which the BRI information is superimposed.

  According to such a procedure, the communication method is such that, in the exchange-connected media gateway constituting the ATM cell transmission system, the protocol processing between the subscriber exchange and the ATM network is replaced with the conventional AAL type 2, and the processing load is reduced. In order to compensate for the fact that ISDN cannot be mapped onto ATM with only AAL type 1, the BRI information is superimposed on the ATM cell payload by the basic interface mapping protocol. As a result, the ATM cell transmission system can use a component with a small protocol processing capacity for its component device, and can have a facility configuration with reduced costs.

  In the communication method according to the present invention, it is preferable that the media gateway further performs echo cancellation processing on the separated B channel communication data between the separation step and the mapping step.

  According to such a procedure, the communication method performs echo cancellation processing on communication data of the B channel after separating the BRI information into communication data and control signals of each channel and before mapping to the cell. A quality ISDN (voice) service can be provided.

  In the communication method according to the present invention, in the mapping step, the media gateway is configured such that, in the mapping step, B1 consisting of 8 bits in the first B channel, B2 consisting of 8 bits in the second B channel, and D channel The ATM cell is configured in accordance with the mapping protocol for the basic interface, with each frame configured from a bit string including a total of 2 bits D corresponding to the two B channels. For a payload consisting of 48 bytes, an AAL1 header consisting of 1 byte, a BRI control header including a control signal consisting of 2 bytes, B1, B2 and D for the first to fourth frames consisting of 9 bytes, B1, B2 and D for the fifth to eighth frames consisting of 9 bytes and 9 bytes B1, B2, and D for the ninth to twelfth frames, B1, B2, and D for the thirteenth to sixteenth frames consisting of 9 bytes, and B1, B2, and the nineteenth to twentieth frames consisting of 9 bytes D, and B1, B2, and D for the four frames, when n is 1, 5, 9, 13, or 17, n bytes B1 and B2 of the 2nd byte and 2 B1 and B2 of the (n + 1) th frame consisting of bytes, B1 and B2 of the (n + 2) th frame consisting of 2 bytes, B1 and B2 of the (n + 3) th frame consisting of 2 bytes, and the nth to (n + 1) th It is preferable to provide 1-byte data obtained by concatenating D of the frame 2 bits at a time.

  According to this procedure, the communication method stores four frames of B1, B2, and D packets as one unit in the ATM cell payload, so the 48 bytes defined by the ATM cell payload standard are effectively used. can do.

Also, the media gateway according to the present invention terminates an ATM network and terminates an ATM termination device disposed at a user's home, a subscriber exchange connected to a public telephone network, and an SDH (Synchronous Digital Hierarchy), and the ATM. A media gateway that terminates a network and is communicably connected to the subscriber exchange and the ATM network, and executes the communication method in an ATM cell transmission system that converts communication data into ATM cells and sends the ATM data to the ATM network. An exchange interface means for receiving B-channel communication data, D-channel communication data and control signals included in the basic interface output from the subscriber exchange as BRI information, and a gateway for each ATM terminator Execute protocol processing by AAL type 1 at the AAL layer And a separation process for separating the received BRI information into the B channel communication data, the D channel communication data, and the control signal in a layer higher than the AAL layer. In an upper layer, communication data processing means for superimposing the separated communication data and control signal on an ATM cell by a mapping protocol predetermined for the basic interface; and an ATM cell on which the BRI information is superimposed ATM interface means for outputting to the ATM network.

  According to such a configuration, the media gateway executes protocol processing between the subscriber exchange and the ATM network by AAL type 1, and superimposes BRI information on the payload of the ATM cell by the mapping protocol for the basic interface. As a result, the media gateway does not require multiplexing processing when using AAL2 that has been adopted in the prior art, and the processing load is reduced. Therefore, it is possible to use a part having a small protocol processing capacity for the media gateway, thereby reducing the manufacturing cost.

  In the media gateway according to the present invention, the communication data processing means includes a B channel processing means for superimposing the B channel communication data on the payload of the ATM cell, and a D channel communication data as the payload of the ATM cell. D channel processing means for superimposing the control signal on the ATM cell payload and control signal processing means for superimposing the control signal on the payload of the ATM cell, wherein the B channel processing means performs echo cancellation processing on the B channel communication data. To the payload of the ATM cell.

  According to such a configuration, the media gateway performs echo cancellation processing on the B-channel communication data and then maps it to the ATM cell, so that it is possible to provide a high-quality ISDN (voice) service.

The ATM terminator according to the present invention terminates an ATM network and is located at a user's home, a subscriber exchange connected to a public telephone network, and an SDH (Synchronous Digital Hierarchy). A protocol according to the AAL type 1 executed by the media gateway, the ATM termination device in an ATM cell transmission system comprising: a media gateway that terminates an ATM network and is communicably connected to the subscriber exchange and the ATM network. A control unit corresponding to the processing and the mapping protocol is provided, and an ATM cell on which the BRI information is superimposed is received from the media gateway.

  According to such a configuration, the ATM terminator is necessary when receiving ATM cells using the conventional AAL2 because the ATM cells to be received are superimposed with BRI information by AAL type 1 protocol processing and mapping protocol. There is no need to install a special software unit in the control unit, and the manufacturing cost can be reduced.

  According to the present invention, since the protocol for mapping ISDN on ATM is changed to a protocol with a lower load than before, the processing capacity required for the protocol processing of each device constituting the ATM cell transmission system is reduced. be able to. As a result, the cost of each device can be reduced.

It is a figure which shows the protocol stack in each apparatus of the ATM cell transmission system which concerns on embodiment of this invention. It is a block diagram which shows the structure of the exchange connection type media gateway which concerns on embodiment of this invention. It is a block diagram which shows the connection in each apparatus of the ATM cell transmission system containing the exchange connection type | mold media gateway which concerns on embodiment of this invention. It is a figure which shows the outline of the protocol process in the exchange connection type media gateway which concerns on embodiment of this invention. It is a figure which shows the specific example of the ISDN mapping in the exchange connection type media gateway which concerns on embodiment of this invention. It is a figure which shows the specific example of the IAD cell which the exchange connection type media gateway which concerns on embodiment of this invention produces. It is a sequence diagram which shows the communication method in the exchange connection type media gateway and ATM terminal device which concern on embodiment of this invention. It is a block diagram which shows the connection in each apparatus which comprises the system of the prior art A. It is a figure which shows the protocol stack in each apparatus which comprises the system of the prior art A. It is a figure which shows the call connection sequence in each apparatus which comprises the system of the prior art A. It is a block diagram which shows the structure of the exchange connection type media gateway of the prior art B. It is a figure which shows the protocol stack in each apparatus of the ATM cell transmission system containing the exchange connection type media gateway of the prior art B. It is a block diagram which shows the connection in each apparatus which comprises the ATM cell transmission system of the prior art B. It is a figure which shows the call connection sequence in each apparatus which comprises the ATM cell transmission system of the prior art B. It is a figure which shows the outline of the protocol process in the exchange connection type media gateway of the prior art B.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments (hereinafter referred to as “embodiments”) for carrying out a communication method, a media gateway, and an ATM terminating device of the present invention will be described in detail below with reference to the drawings.

[Outline of communication method]
An outline of a communication method according to an embodiment of the present invention will be described with reference to FIG. 1 (see FIGS. 2 and 3 as appropriate). The communication method according to the embodiment of the present invention is a communication method in the ATM cell transmission system 1 shown in FIGS. An ATM cell transmission system 1 includes an exchange-connected media gateway 2 that can be connected to an existing telephone network (a subscriber exchange 4 connected by an exchange interface and a public telephone network (not shown)), and this exchange-connected media gateway. And an ATM termination device 3 that terminates the ATM network 5 in accordance with the protocol No. 2. As shown in FIGS. 2 and 3, the ATM cell transmission system 1 is configured by similarly connecting devices having the same configuration as the ATM cell transmission system 900 of the prior art B described above. However, in the communication method according to the embodiment of the present invention, the AAL type 1 is used when the ISDN is mapped onto the ATM in the exchange-connected media gateway 2. As a result, the ATM cell transmission system 1 can have a configuration in which the cost is lower than that of the ATM cell transmission system 900 of the prior art B by using a component having a smaller protocol processing capacity for the component device.

FIG. 1 shows a protocol stack of the control unit in the exchange-connected media gateway 2. The exchange connection type media gateway 2 is connected to the ATM network 5 and the subscriber exchange 4. The difference from the prior art B (see FIG. 12) is the protocol between the subscriber exchange 4 and the ATM terminating device 3.
There is no change in the ISDN user / network interface 102 and the ATM 110 in the protocol between the subscriber switch 4 and the ATM terminating device 3, but the upper layer of the ATM 110 is an ATM adaptation layer type 1 denoted by reference numeral 121, and It becomes ISDN mapping 122 (ISDN mapping method).

  In ATM adaptation layer type 2 (see FIG. 12), ISDN can be mapped to ATM, whereas in ATM adaptation layer type 1, ISDN can be mapped onto ATM as it is. It is not possible. Therefore, in addition to the ATM adaptation layer type 1 indicated by reference numeral 121 in FIG. 1, ISDN mapping 122 is used to map ISDN on ATM. Specific examples of mapping will be described later.

[Media Gateway Configuration]
The configuration of the exchange-connected media gateway (AAL1) 2 will be described with reference to FIG.
The exchange-connected media gateway 2 is a device that executes protocol processing according to AAL type 1. This is illustrated as an exchange-connected media gateway (AAL1).
AAL type 1 (AAL1) is an ITU-T recommendation I.D. It is defined in 363.1.
The exchange-connected media gateway 2 is realized by, for example, an arithmetic device such as a CPU (Central Processing Unit), a storage device such as a memory or a hard disk, and an interface device that transmits and receives various types of information to and from the outside. As shown in FIG. 2, an exchange interface unit 6, an ATM interface unit 7, and a voice processing unit 8 are provided.

The exchange interface unit (exchange interface means) 6 terminates the SDH, and transmits the B channel, D channel, and control signal (SG channel) included in the ISDN basic group (BRI) interface sent from the subscriber exchange 4 as audio. Output to the processing unit 8.
Hereinafter, B channel communication data, D channel communication data, and control signals included in the basic interface are referred to as BRI information.
Note that the B channel is used to transmit user information such as voice data, the D channel is used to transmit call control signal information for controlling incoming and outgoing calls, and the SG channel is Used to monitor the line status.

  The ATM interface unit (ATM interface means) 7 terminates the ATM and is sent from the ATM terminator 3 and includes the B channel, the D channel and the control signal (ATM terminator control, included in the ISDN basic group (BRI) interface). BRI control) is output to the voice processing unit 8.

  The voice processing unit (communication data processing means) 8 separates the B channel, D channel, and control signal (BRI control, SG channel) output from the exchange interface unit 6 and performs processing. Control signals (ATM terminator control, BRI control) are output to the ATM interface unit 7.

  The voice processing unit 8 separates and processes the B channel, D channel, and control signals (ATM terminator control, BRI control) output from the ATM interface unit 7, and performs processing on the B channel, D channel, and control signal. (SG channel) is output to the exchange interface unit 6.

  The audio processing unit 8 includes a Bch processing unit (B channel processing unit) 11, a Dch processing unit (D channel processing unit) 12, and a control signal processing unit (control signal processing unit) 13 as control units.

The Bch processing unit 11 superimposes the B channel communication data on the payload of the ATM cell.
The Bch processing unit 11 includes an EC processing unit (echo cancellation processing unit) 14 as an echo canceller function (for the subscriber side and the exchange side). The EC processing unit 14 removes the echo of the Bch sound according to the conditions such as the communication distance and the processing content of the Dch processing unit 12 (echo cancellation processing).
In the present embodiment, the Bch processing unit 11 performs echo cancellation processing on communication data of the B channel and then superimposes it on the payload of the ATM cell.
The Dch processing unit 12 superimposes the D channel communication data on the payload of the ATM cell.
The control signal processing unit 13 superimposes the control signal on the payload of the ATM cell.

  Although details will be described later, the voice processing unit 8 executes the protocol processing according to the ATM adaptation layer type 1 indicated by reference numeral 121 in FIG. 1 and converts the received BRI information into the BRI information by the ISDN mapping 122 higher than the AAL layer. Separation processing for separating the channel communication data, the D channel communication data, and the control signal is executed, and the ISDN mapping 122 converts the separated communication data and the control signal into an ATM using a mapping protocol predetermined for the basic interface. Superimpose on the cell.

The ATM terminator 3 is installed in the user's home H (see FIG. 3), and superimposes the ISDN basic group (BRI) interface on the ATM by the control signal from the exchange-connected media gateway 2 to terminate the ATM network 5. To do.
The ATM termination device 3 includes a control unit corresponding to the protocol processing by the AAL type 1 executed by the exchange-connected media gateway 2 and the mapping protocol, and receives ATM cells on which BRI information is superimposed from the exchange-connected media gateway 2. Receive.

[Connection in each device of ATM cell transmission system]
Next, the connection in each device of the ATM cell transmission system 1 will be described with reference to FIG. From the user's home H to the ATM network 5 of the subscriber station building MB, it is connected using the dark fiber F, and the subscriber exchange 4 is installed only in the relay station building IB. The point accommodated in the subscriber exchange 4 of the relay station building IB is the same as the ATM cell transmission system 900 of the prior art B.
However, instead of the ATM terminator 903 (AAL2), the ATM terminator 3 (AAL1 + ISDN mapping) is installed in the user's home H, and in the relay station building IB, the exchange-connected MG902 (AAL2) is exchanged. It differs from the prior art B in that the connection type media gateway 2 (AAL1) is installed.

[MG protocol processing]
Next, protocol processing by the exchange-connected media gateway 2 according to the embodiment of the present invention will be described in comparison with the exchange-connected MG (AAL2) of the prior art B.
The ATM adaptation layer type 1 (AAL1) assumes a CBR (Constant Bit Rate) service, unlike the type 2 (AAL2) which assumes a VBR (Variable Bit Rate) service.

  Although not shown, the type 2 (AAL2) sub-layers are CPS (Common Part Sublayer) and SSCS (Service Specific Convergence Sublayer) from the lower level, whereas type 1 (AAL1) The sublayers are SAR (Segregation And Reassembly Sublayer) and CS (Convergence Sublayer) from the bottom. Among these, the CS performs data segment identification, error detection, recovery processing, and the like. The SAR performs, for example, assembly / disassembly processing between upper layer data and ATM cells.

  And while type 2 (AAL2) performs cell multiplexing processing 111-1 (see FIG. 15) for multiplexing B-channel voice packets of multiple users into one cell, type 1 (AAL1) The cell multiplexing process is not performed (see FIG. 4).

This type 1 (AAL1) performs cell assembly / disassembly into a specific VCI (Virtual Channel Identifier) for each channel (for each user). For this reason, processing associated with the port of the ATM terminal device 3 of the user on a one-to-one basis is possible.
Specifically, the exchange-connected media gateway 2 uses the ISDN user / network interface 102 to transmit B channel communication data, D channel communication data included in the basic (BRI) interface output from the subscriber exchange 4, and When the control signal is received, as shown in FIG. 4, the information received for each user in the upper layer in ISDN mapping 122, the B channel voice packet (Bch 126), the D channel communication packet (Dch 127), Separation processing 122-1 for separation into the control signal 128 is performed, and an ATM cell is assembled using the ATM adaptation layer type 1 denoted by reference numeral 121. In AAL1, cell multiplexing processing is not performed.

  For this reason, AAL1 requires lighter processing than AAL2. As a result, by using this protocol, it is not necessary to place a special software unit on the ATM terminating device 3, and it is not necessary to prepare a high-performance processor or the like in the exchange-connected media gateway 2. Therefore, the cost of the exchange-connected media gateway 2 and the ATM terminating device 3 can be made lower than that of each device constituting the ATM cell transmission system 900 of the prior art B.

[Example of specific mapping]
A specific example of the ISDN mapping 122 shown in FIGS. 1 and 4 will be described with reference to FIG. Hereinafter, the ISDN basic group (BRI) stream data (first B channel, second B channel, and D channel) converted into ATM cells is referred to as a BRI cell. Here, the transmission rate of the BRI cell is, for example, 400 cells / second. Also, for the sake of explanation, when it is necessary to distinguish where the BRI cell was sent from, the BRI cell sent from the exchange-connected media gateway 2 side to the ATM terminating device 3 side is described as MG, and conversely The BRI cell sent from the ATM terminating device 3 side to the exchange-connected media gateway 2 side is distinguished from the device origin.
<Frame configuration>
Here, the frames allocated to one user are B1 consisting of 8 bits in the first B channel, B2 consisting of 8 bits in the second B channel, and 2 bits in the D channel. It is assumed that it is composed of a bit string including a total of 2 bits D corresponding to each of the B channels. Here, the symbol “B1” of double-byte characters indicates a bit string of 8 bits (= 1 byte), and the first to twentieth frames are superimposed on one ATM cell (BRI cell).

For example, a bit in the first B channel is represented by a single-byte character symbol “B1”, similarly, a bit in the second B channel is represented as “B2”, and similarly, a bit in the D channel is represented by “B2”. When expressed as “D”, each presupposed frame includes a bit string in the following “”. In this case, the total number of bits of 2B + D constituting the frame is 18.
First frame: “B1 B1 B1 B1 B1 B1 B1 B1 D B2 B2 B2 B2 B2 B2 B2 B2 D”
Second frame: “B1 B1 B1 B1 B1 B1 B1 B1 D B2 B2 B2 B2 B2 B2 B2 B2 D”
...
20th frame: “B1 B1 B1 B1 B1 B1 B1 B1 D B2 B2 B2 B2 B2 B2 B2 B2 D”

  As shown in FIG. 5, the BRI cell 20 created by the exchange-connected media gateway 2 is obtained by adding a 5-byte ATM header 20 </ b> H to a 48-byte payload 20 </ b> P.

  In the ATM header (ATM cell header) 20H, different standards for a known NNI (Network-Network Interface) and UNI (User-Network Interface) are defined. Here, for example, VPI (Virtual Path Identifier), VCI (Virtual Channel Identifier), etc. are set.

  The payload 20P includes an AAL1 header 21 composed of 1 byte, a BRI control header 22 including a control signal composed of 2 bytes, main signal information (formally divided packet groups 23 to 27) composed of 45 bytes, and It has. Here, the part combining the BRI control header 22 and the main signal information is a 47-byte AAL1 SAR PDU (Protocol Data Unit). In FIG. 5, (2B) indicates 2 bytes.

  The AAL1 header 21 has a known SN (Sequence Number) field and a SNP (Sequence Number Protection) field. The SN includes a CSI bit and a 3-bit sequence count, and the SNP includes a 3-bit CRC (Cyclic Redundancy Check) and P (parity bit).

  The BRI control header 22 includes a 1-bit BRI / IAD control identifier 221, a 3-bit BRI identification 222, an 8-bit BRI control 223, and a 4-bit CRC 224. In FIG. 5, (1b) indicates 1 bit.

The BRI / IAD control identifier 221 indicates information for identifying whether the ATM cell is a BRI cell or an IAD (Integrated Access Device) cell described later. Here, the bit is represented by “0” in the case of the BRI cell, and is represented by “1” in the case of the IAD cell. The IAD cell is an ATM cell for controlling the operation of the ATM termination device 3.
The BRI identification 222 is information for identifying the ISDN basic group (BRI). For example, BRI0 is represented by “000”, BRI2 is represented by “001”, and BRI7 is represented by “111”. In this case, the ISDN basic group indicates, for example, eight types of ISDN basic interfaces.
The BRI control 223 is information indicating a BRI setting instruction when the MG is issued. This setting instruction indicates, for example, a loop 2 test instruction, a channel call state notification, an S / T point activation instruction, and the like with a total of 8 bits or less. Here, the S point and the T point are ISDN user / network interface points defined in JTC-I411. The loop 2 test is a loop back 2 test, and is performed on each channel (first B channel, second B channel, and D channel).
The BRI control 223 indicates information for notifying the state of the BRI when the apparatus originates. This status notification includes, for example, loop 2 test status notification, S / T point device failure notification, S / T point power supply failure notification, S / T point link status notification, S / T point activation status notification within a total of 8 bits. Indicated by the bit.
Since CRC 224 is different from the CRC of the AAL1 header 21, it is represented as CRC4.

The main signal information (packet groups 23 to 27) is TDM (Time Division Multiplex) stream data (first B channel, second B channel, D channel), and the main signal information of 4 frames × 5 for a total of 20 frames. Stores signal data.
More specifically, the packet group 23 consists of 9 bytes, and for the first to fourth frames, each consists of B1 consisting of 8 bits in the first B channel and 8 bits in the second B channel. And B, which is a bit in the D channel and corresponding to two B channels, each consisting of a total of 2 bits. The packet order will be described later.

The packet group 24 is the same as the packet group 23, but includes packets for the fifth to eighth frames.
The packet group 25 is the same as the packet group 23, but includes packets for the ninth to twelfth frames.
The packet group 26 is the same as the packet group 23, but includes packets for the 13th to 16th frames.
The packet group 27 is the same as the packet group 23, but includes packets for the 17th to 20th frames.

In the packet groups 23 to 27, the packets are connected in a predetermined alignment order.
As an example, the packet group 26 includes octets 261 to 268 and 30. The octet indicates 8 bits as in the byte.
The structure of the packet group 26 will be generalized to all the packet groups 23 to 27.
Here, n represents 1, 5, 9, 13 or 17.
At this time, the octet 261 is B1 of the nth frame (frame n), and the octet 262 is B2 of the nth frame (frame n).
Octet 263 is B1 of the (n + 1) th frame (frame n + 1), and octet 264 is B2 of the (n + 1) th frame (frame n + 1).
Octet 265 is B1 of the (n + 2) th frame (frame n + 2), and octet 266 is B2 of the (n + 2) th frame (frame n + 2).
Octet 267 is B1 of the (n + 3) th frame (frame n + 3), and octet 268 is B2 of the (n + 3) th frame (frame n + 3).

Octet 30 is obtained by concatenating D in frame n, D in frame n + 1, D in frame n + 2, and D in frame n + 3.
D in frame n is a concatenation of bit 31 corresponding to the first B channel for frame n and bit 32 corresponding to the second B channel for frame n.
D in frame n + 1 is a concatenation of bit 33 corresponding to the first B channel for frame n + 1 and bit 34 corresponding to the second B channel for frame n + 1.
D in frame n + 2 is a concatenation of bit 35 corresponding to the first B channel for frame n + 2 and bit 36 corresponding to the second B channel for frame n + 2.
D in frame n + 3 is a concatenation of bit 37 corresponding to the first B channel for frame n + 3 and bit 38 corresponding to the second B channel for frame n + 3.

Next, the IAD cell will be described with reference to FIG. 6 (see FIG. 5 as appropriate). The transmission rate of the IAD cell is, for example, 100 cells / second.
As shown in FIG. 6, the IAD cell 40 includes a 5-byte ATM header 41, a 1-byte AAL1 header 42, and a 47-byte AAL1 SAR PDU 43.
The ATM header 41 and the AAL1 header 42 are the same as the ATM header 20H and the AAL1 header 21 shown in FIG.
The AAL1 SAR PDU 43 includes an IAD control channel 44, an IAD control link 45, and a CRC indicated by reference numeral 46. Since CRC is 4 bytes (32 bits), it is described as CRC32.

The IAD control channel 44 includes a BRI / IAD control identifier 441, padding 442, IAD control 443, used BRI control 444, device identifier 445, temperature information 446, and RESERVE 447.
The BRI / IAD control identifier 441 consists of 1 bit and is the same as the BRI / IAD control identifier 221 shown in FIG.
The padding 442 is a 7-bit string that is all “0”.
The IAD control 443 is composed of 8 bits, and is information indicating a setting instruction such as a display in the ATM terminating device 3 in the case of MG. This setting instruction indicates, for example, an LED control instruction such as lighting, blinking, and stopping of an LED lamp indicating a device state in the ATM terminal device 3 and a restart instruction of the ATM terminal device 3 by a total of 8 bits or less. Note that a plurality of LED lamps are provided, for example, to display power ON, alarm, etc. in different colors. The device state that requires an alarm indicates, for example, a state in which the device temperature is abnormally rising or a state in which some other failure has occurred in the device.
The IAD control 443 indicates information for notifying the apparatus state when the apparatus originates. This device status notification indicates, for example, the LED lamp status, the device status at the time of alarm, or the like by a total of 8 bits or less.
The used BRI control 444 has 8 bits and is information indicating which one of BRI0 to BRI7 is used.

The device identifier 445 consists of 16 bytes, and is “0” padding when originating from the MG, and indicates identification information such as a serial number of the device when originating from the device.
The temperature information 446 is made up of 2 bytes, and is “0” padding when originating from the MG, and indicates internal temperature information of the device when originating from the apparatus.
RESERVE 447 is spare information consisting of 14 bytes.
The IAD control link 45 includes a CTL 451, an ADR 452, and a DATA 453.
The CTL 451 is composed of 8 bits and indicates a write request or a read request to a memory or the like inside the ATM terminator 3 when it is originated from the MG, and a completion notification when it originates from the apparatus.
The ADR 452 is composed of 24 bits and indicates an address of a memory or the like inside the ATM terminator 3. The DATA 453 is composed of 32 bits and indicates data to be written or read.

  The exchange-connected media gateway 2 sets the BRI cell 20 in accordance with ISDN mapping 122 (mapping protocol for the basic interface) predetermined for creating the BRI cell 20 shown in FIG. The B channel communication data, the D channel communication data, and the control signal included in the basic interface are superimposed on the payload 20P to be configured.

[Call connection sequence of each device in ATM cell transmission system]
The call connection sequence of each device in the ATM cell transmission system 1 is the same as the call connection sequence of each device in the ATM cell transmission system 900 of the prior art B described with reference to FIG.

[Protocol conversion operation of exchange-connected media gateway]
Next, the protocol conversion operation of the exchange-connected media gateway 2 will be described with reference to FIG. 7 (refer to FIGS. 1 to 5 as appropriate).
The exchange-connected media gateway 2 receives the BRI data (BRI information) sent from the subscriber exchange 4 by the exchange interface unit 6 (reception step: step S1), and an ATM adaptation layer denoted by reference numeral 121 in FIG. Protocol processing according to type 1 (AAL1) is performed to divide the frame into 48 bytes (adaptation layer processing step: step S2). Then, the exchange-connected media gateway 2 performs the separation process 122-1 shown in FIG. 4 by the ISDN mapping 122 (separation step: step S3). Then, the exchange-connected media gateway 2 executes echo cancellation processing by the EC processing unit 14 (step S4).

  Subsequently, the exchange-connected media gateway 2 maps the ISDN to the payload 20P of the BRI cell 20 by the ISDN mapping 122 (mapping step: step S5). Then, the exchange-connected media gateway 2 creates the BRI cell 20 by adding the ATM header 20H to the payload 20P in the ATM layer denoted by reference numeral 110 in FIG. 1 (ATM cell creation step: step S6). Then, the exchange-connected media gateway 2 outputs the ATM cell (BRI cell 20) to the ATM network 5 by the ATM interface unit 7 (output step: step S7). Thereby, the ATM termination device 3 receives the ATM cell from the exchange-connected media gateway 2 via the ATM network 5 (reception step: step S8), and performs a predetermined process.

  On the other hand, the ATM terminating device 3 transmits an ATM cell to the exchange-connected media gateway 2 connected to the subscriber exchange 4 that accommodates the user based on the voice input of the analog telephone 10 of the user (step S9). . Then, the exchange-connected media gateway 2 receives the ATM cell by the ATM interface unit 7 (step S10), and performs the separation process 122-1 shown in FIG. 4 by the ISDN mapping 122 (step S11). Then, the exchange-connected media gateway 2 executes echo cancellation processing by the EC processing unit 14 (step S12). Subsequently, the exchange-connected media gateway 2 performs protocol processing according to AAL type 1 to assemble a frame (step S13). Then, the exchange connection type media gateway 2 outputs the BRI data to the subscriber exchange 4 through the exchange interface unit 6 (step S14). As a result, the subscriber exchange 4 receives the BRI data and performs a predetermined process.

  According to the communication method of the present embodiment, the protocol for mapping ISDN on ATM has been changed to a protocol with a lower load than before, so that it is necessary for the protocol processing of each device constituting the ATM cell transmission system 1. Processing capacity can be reduced. As a result, the cost of each device can be reduced. Therefore, the cost of the entire ATM cell transmission system can be reduced. As a result, an ISDN voice service using the ATM network 5 can be provided at a low cost.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can implement in the range which does not change the meaning. For example, the exchange-connected media gateway 2 has been described as a mode in which the Bch processing unit 11 includes the EC processing unit 14, but may be configured not to include the EC processing unit 14. In this case, the cost of the exchange-connected media gateway 2 can be further reduced.

  Although a specific example using the ISDN mapping 122 is shown in FIG. 5, the format for mapping ISDN to ATM is not limited to the example of FIG. 5 as long as the corresponding standard can be satisfied.

1,900 ATM cell transmission system 2,902 exchange-connected media gateway 3,903 ATM terminator 4,904 subscriber exchange 5,905 ATM network 6,906 exchange interface unit (exchange interface means)
7,907 ATM interface (ATM interface means)
8,908 Audio processing unit (communication data processing means)
9,909 Terminal adapter (TA)
10,910 Analog phone 11,911 Bch processing unit (B channel processing means)
12,912 Dch processing unit (D channel processing means)
13,913 Control signal processing unit (control signal processing means)
14,914 EC processing unit (echo cancellation processing unit)
800 Transmission System 801 Relay Switch 803 Line Terminator 804 Subscriber Switch 809 Terminal Adapter (TA)
810 Analog phone F Dark fiber IB Relay station building MB Subscriber station building H User's house IL Relay line ML Subscriber line

Claims (6)

An ATM terminating device that terminates the ATM network and is located at the user's home, a subscriber exchange connected to the public telephone network, an SDH (Synchronous Digital Hierarchy), and terminates the ATM network to terminate the subscriber exchange and A communication method in an ATM cell transmission system comprising a media gateway that is communicably connected to an ATM network, wherein communication data is converted into ATM cells and sent to the ATM network.
The media gateway is
For each ATM terminator , the ISDN user / network interface receives B channel communication data, D channel communication data and control signals included in the basic (BRI) interface output from the subscriber exchange as BRI information. Receiving step to
A matching layer processing step for performing protocol processing according to AAL type 1 for each ATM terminator in the AAL layer and adapting the received BRI information to the ATM layer;
A separation step of separating the BRI information received for each ATM terminator into the communication data of the B channel, the communication data of the D channel, and the control signal in a layer higher than the AAL layer;
A mapping step of superimposing the separated communication data and control signal on the ATM cell payload in a layer higher than the AAL layer by a mapping protocol predetermined for the basic interface for each ATM termination device ;
In the ATM layer, for each ATM terminator, an ATM cell creating step of creating the ATM cell by adding an ATM header to a payload on which the BRI information is superimposed;
An output step of outputting the created ATM cell to the ATM network for each ATM termination device ;
The ATM terminator is
A communication method including a reception step of receiving an ATM cell on which the BRI information is superimposed from the media gateway via the ATM network. The media gateway is
Between the separation step and the mapping step,
2. The communication method according to claim 1, further comprising performing echo cancellation processing on the separated communication data of the B channel. The media gateway is
In the mapping step,
B1 consisting of 8 bits in the first B channel, B2 consisting of 8 bits in the second B channel, and 2 bits in the D channel corresponding to the two B channels respectively. Each frame composed of a bit string including D, according to the mapping protocol for the basic interface, for a payload consisting of 48 bytes constituting the ATM cell,
An AAL1 header consisting of 1 byte;
A BRI control header containing a 2-byte control signal;
B1, B2 and D for the first to fourth frames consisting of 9 bytes;
B1, B2 and D for the fifth to eighth frames of 9 bytes;
B1, B2 and D for 9th to 12th frames of 9 bytes;
B1, B2 and D for the 13th to 16th frames consisting of 9 bytes,
B1, B2, and D for the 17th to 20th frames of 9 bytes are stored in order,
B1, B2, and D for the four frames are
When n is 1, 5, 9, 13 or 17,
B1 and B2 of the nth frame consisting of 2 bytes,
B1 and B2 of the (n + 1) th frame consisting of 2 bytes,
B1 and B2 of the (n + 2) th frame consisting of 2 bytes,
B1 and B2 of the (n + 3) th frame consisting of 2 bytes,
3. The communication method according to claim 1, further comprising: 1-byte data obtained by concatenating D of the nth to (n + 1) th frames by 2 bits each. An ATM terminating device that terminates the ATM network and is located at the user's home, a subscriber exchange connected to the public telephone network, an SDH (Synchronous Digital Hierarchy), and terminates the ATM network to terminate the subscriber exchange and 4. A communication method according to claim 1, further comprising: a media gateway that is communicably connected to an ATM network, wherein the communication data is converted into ATM cells and transmitted to the ATM network. 5. Said media gateway executing:
Exchange interface means for receiving B channel communication data, D channel communication data and control signals included in the basic interface output from the subscriber exchange as BRI information;
For each ATM terminator, protocol processing according to AAL type 1 is executed in the AAL layer, and the received BRI information is transmitted to the B channel communication data and the D channel communication in a layer higher than the AAL layer. Separation processing for separating data and the control signal is executed, and the separated communication data and control signal are transmitted on the ATM cell by a mapping protocol predetermined for the basic interface in a layer higher than the AAL layer. Communication data processing means to be superimposed on,
ATM interface means for outputting the ATM cell on which the BRI information is superimposed to the ATM network;
A media gateway comprising: The communication data processing means includes
B channel processing means for superimposing the B channel communication data on the payload of the ATM cell;
D channel processing means for superimposing the D channel communication data on the payload of the ATM cell;
Control signal processing means for superimposing the control signal on the payload of the ATM cell,
5. The media gateway according to claim 4, wherein the B channel processing means performs echo cancellation processing on the communication data of the B channel and then superimposes it on the payload of the ATM cell. An ATM terminating device that terminates the ATM network and is arranged at the user's home, a subscriber exchange connected to a public telephone network, an SDH (Synchronous Digital Hierarchy) and an ATM network that terminates the ATM network and the subscriber exchange A ATM gateway in an ATM cell transmission system comprising a media gateway that is communicably connected to an ATM network,
A control unit corresponding to the protocol processing by the AAL type 1 executed by the media gateway according to claim 4 or 5 and the mapping protocol,
An ATM terminating device, wherein the ATM cell on which the BRI information is superimposed is received from the media gateway.

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