FI109074B - Abonnentmultiplexeringsanordning - Google Patents

Abstract

A subscriber multiplexing device comprising a time-division user data bus (33) and a message-based signalling channel (34) between subscriber interface units (32) and a multiplexing unit (31), the signalling channel being common to all the subscriber interface units. A "message based" signalling channel means that signalling is transferred in discrete protocol data units (PDU), or messages, comprising at least a destination address and the actual signalling data. Each unit connected to the signalling channel receives the message and compares the destination address of the message to its own address. When the addresses match, the unit concerned identifies the message as being addressed to it. If there is no match, the unit rejects the message. Each unit sends a signalling message only when needed, on event basis, in response to an internal change in state or to a message received from another unit, for example. In other words, information about changes is only signalled further through the signalling channel (34).

Description

109074!

The invention relates to subscriber multiplexing devices which are used in subscriber access networks in telephone systems.

Although digital exchanges are nowadays commonly used in telephone networks, the subscriber lines from the exchange to the subscriber are typically analog dual-conductor subscriber lines. Therefore, in digital exchanges a special analog subscriber interface is needed which coordinates a digital exchange time division signal and an analog subscriber line, such as FIG. 1, a subscriber interface 11 of a switch 10 10 connected to a subscriber line 13 to a subscriber terminal 12. in a spaced multiplexing unit 14 connected by a digital cable 18 (e.g., 2 Mbit / s) to the exchange digital subscriber interface 19. Such a remote multiplexing unit 16 may also be connected to a digital multiplexer 20 (e.g., 2 Mbit / s) to another multiplexing device 21. located near the center. The analog subscriber interface 221 of this second multiplexing unit is then connected to a digital or analog exchange. to the analog subscriber connection 23. • · · ·. ' The use of the aforementioned devices allows longer distances between subscribers and the exchange than · purely analog subscriber lines between the exchange and the subscriber.

In addition, the multiplexing device can be located close to subscribers, whereby the star-shaped I! "Subscriber network can be implemented with short subscriber lines and thereby at a relatively low cabling cost.

The basic digital exchange subscriber interface is illustrated in FIG. 2. The analog subscriber line conductors a and b are connected to a subscriber line interface circuit 30 (SLIC). The audio frequencies on the wires a and b are routed to the SLIC ··· circuit 30, which sets the time impedance of the subscriber line and separates the transmission and reception direction signals. The uplink signal is fed through a low pass filter 31 to a codec 33 which converts the subscriber line. \ t 30 analog signals to a digital PCM encoded format and transmits the PCM - *;. V signal to the exchange. Similarly, the PCM encoded signal from the exchange is converted in codec 33 into an analog transmission direction signal, which is supplied through a low pass filter 32 and a SLIC circuit 30 to the subscriber line.

2 109074 The most important functions of the subscriber line interface SLIC are the subscriber line power supply, the call voltage supply, the subscriber loop activation indication (off-hook), etc. An active subscriber loop or off-hook mode refers to a case where the subscriber lifts his handset and b conductors to each other to form a direct current loop from the SLIC circuit through the subscriber line to the subscriber terminal and back. When the subscriber loop is activated, the SLIC detects the loop current and sends an off-hook status message to the exchange. When the handset is lowered (on-hook mode), the subscriber loop is broken and the loop power is lost. The SLIC circuit detects the lack of loop current 10 and reports the on-hook status to the exchange.

One subscriber multiplexing device, such as the multiplexing devices 14, 16 and 21 in Figure 1, generally has a large number of subscriber connections. This is because the digital connection between the exchange and the multiplexer is usually at least 2 Mbit / s PCM (Pulse code modulation) !. This mer-15 limits the capacity of at least 30 subscriber channels and two signaling channels. A high speed PCM connection can be handled by a relatively simple multiplexing unit common to all subscriber interfaces. The problem with y. such a road trip multiplexer has how to arrange the internal:. transmission of useful information (speech or data), and in particular signaling multiplexing; 20 units and between each individual subscriber interface. One known solution is the · · * 'time division bus which connects the subscriber interface units and the multiplexing unit. There may also be custom time-sharing buses for the transmission of voice information and signaling. The bus is allocated one time slot for each of the forwarding lines to carry the call during the call. In addition, the multiplexing unit continuously scans the subscriber interface units coupled to the 25 (polling) buses to obtain signaling information (such as on-hook, off-hook) from the subscriber interface units to the multiplexing unit. This requires a very large number of time slots and a very fast bus, which makes bus scheduling very critical. Therefore, it is also difficult to centralize: '' ': a large number of subscriber connections to the same multiplexing unit.

; It is an object of the present invention to provide a subscriber multiplexer, wherein simpler and less time-critical signaling between a subscriber interface unit and a multiplexer unit is provided.

This is achieved by a telecommunications network subscriber multiplexing device comprising a multiplexing unit coupled to a multichannel time division digital cable 101074 for two-way transmission of user information and signaling information with another multiplexer and / or exchange; a plurality of subscriber interface units, each comprising a plurality of analog subscriber connections each having a subscriber line circuit for connection to a bidirectional two-wire subscriber line; a time division data bus for transferring user information between the multiplexing unit and the subscriber interface units; a message-based signaling channel for transmitting signaling between the multiplexing unit and the subscriber interface units; the subscriber interface unit comprising a communication means coupled to said signaling channel for transmitting and receiving event messages on a multiplex-10 call unit. The subscriber multiplexing device according to the invention is characterized in that the at least one subscriber interface unit comprises an internal signaling path for signaling between the subscriber line connections and the communication means; a bus interface means coupled to said time division data bus; an internal time division da-15 bus for data transmission between the subscriber line interfaces and the bus interface means; from each interrupt line of the interrupt line to the communication medium, the communication means being responsive to the interrupt signal on the interrupt line for reading the status of the corresponding subscriber line interface w and transmitting the status information to the signaling signal. 'Nom for the multiplexing unit ..

* · ·: 20 In the invention, between the subscriber access units and the multiplexing unit, *. * Is, in addition to a time-sharing user data bus, a message-based Signal Creation Channel common to all subscriber access units. A message-based signaling channel means that the signaling is transmitted in discrete protocol data units (PDUs), that is, messages comprising at least a destination address and actual signaling data. The message is received in all signaling channels; 'connected units that compare the message destination address to its own address. If the addresses match, the unit recognizes the message as being addressed to itself. Otherwise, the unit will reject the message. There are several transmission protocols suitable for use with the signaling channel according to the invention. In a preferred embodiment of the invention, the signaling channel protocol is a High Level Data Link Protocol (HDLC), wherein the protocol data unit or say ma is HDLC. frame.

Another significant feature of the invention is that each unit transmits a signaling message only on an event-by-event basis (on event base 109074 sis). For example, event-based means that a message is sent in response to an internal unit change in a unit that must be notified to another unit, or in response to a message received from another unit. In other words, only the change information is signaled forward through the signaling channel.

5 The message-based signaling channel and event-based message transmission avoid the high speed requirements and timing problems associated with the internal signaling of the prior art multiplexer. In particular, a slower and / or less efficient signal processor may be used in the multiplexing unit. In addition, the invention makes it possible to concentrate well 10 large number of subscriber interface units into one multiplexing unit.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which Figure 1 illustrates various implementations of a local area network in an analog or digital local exchange, Figure 2 is a block diagram of an analog subscriber interface, Figure 3 is a block diagram of a subscriber multiplexing apparatus. . Fig. 4 is a block diagram of a subscriber interface unit according to the invention,> · ·; . Figure 5 is a block diagram of a multiplexing unit according to the invention,. Figures 6 and 7 show HDLC frames transported on a signaling bus, and Fig. 8 is a state map illustrating the operation of the signaling interface circuit.

The present invention is applicable to various subscriber multiplexers in telecommunication systems. One typical application is remote:. Multiplexing devices such as devices 14, 16, and 21 in Figure 1. The preferred embodiment of the invention will now be described as being implemented in a remote multiplexing device.

Figure 3 illustrates a preferred embodiment of the invention. 30-way Subscriber Multiplexer. It comprises a multiplexing unit 31 and N-subscriber access units (SUB) 321 ... 32N. Each subscriber access unit> t SUB 32 may connect to one or more access lines 13. | ... 13 (g. N and M may be any positive integer. The MCU31 multiplex calling unit is connected to a digital high speed transmission line 5 109074 18 or 20 which is for example, a 2 Mbit / s or higher PCM cable The other end of the PCM cable 18 or 20 may have, for example, a digital exchange (such as center 10 in Figure 1) or another subscriber multiplexer (such as a multiplexer 21 in Figure 1).

The multiplexing device comprises at least one internal data bus 33 and a signaling bus 34 to which the subscriber interface units 321 to 32N and the multiplexing unit MCU31 are connected. According to the principles of the invention, the data bus 33 is a time division bus from which each subscriber interface unit SUB32 is fixedly allocated or can be dynamically allocated a time slot for transferring user information between the MCU31 and the SUB32. User information generally refers to speech or data transmitted through a subscriber line. On the data bus 33, user information is typically in the form of PCM samples. The scheduling and control of the data bus 33 is performed by the MCU31 in the preferred embodiment of the invention. In some cases, it may be advantageous to use multiple parallel data buses 33 to which the SUBs 32V..32N and MCU31 can selectively connect. The use of multiple data buses may be advantageous, for example, when the number of subscriber connection units • ·: * V SUB32 is very large and a large amount of bus capacity is required.

However, the implementation of the time division data bus 33 is not, however, within the scope of the invention. · · Relevant, so it is not described here in more detail.

The signaling bus 34 according to the invention is a message-based bus through which the units 32 and 31 transmit messages only on an event-specific basis. In the preferred embodiment of the invention, the message-based signaling channel is implemented as a separate bus, but it can also be implemented in one time slot of a time-sharing data bus. In a preferred embodiment of the invention, the signaling bus 34 protocol is High Level Data (Link Protocol) HDLC, a commonly known data link control protocol. other

»I I

corresponding protocols are ADCCP (Advance Data Communication Control ·; · Procedures), LAP-B (Link Access Procedure, Balanced) and SDLC

· (Synchronous Data Link Control). These protocols are described, for example, in Data and Computer Communications, Williams Stallings, Macmillan Publishing Company, 1994, especially pages 187-197. However, the invention is not limited to these protocols, but any message-based communication can be applied to the signaling bus 34. Also, in this context, a message is any protocol data unit, that is, a message, packet, or 6109074 frame, which in the use of the invention comprises at least the destination address and the actual signaling data.

In a preferred embodiment of the invention, where the signaling channel protocol is HDLC, the protocol data unit or message is an HDLC frame. Figures 6 and 7 illustrate two HDLC frames that can be used on signaling bus 34. Figure 6 illustrates a frame transmitted by the MCU31 to a SUB32. Figure 7 shows a frame transmitted by the SUB32 to the MCU31. Each frame comprises a start flag and an end flag, which are 01111110 according to the HDLC protocol. In addition, each frame comprises a destination address field DEST 10 ADDR, a source address field SOURCE ADDR, a device type field DEVICE TYPE, a data field GEN. DATA and error checking fields CRC1 and CRC2 (Cyclic Redundance Check). The frame of Fig. 6 further includes a BYTE COUNT field which indicates a data field GEN. DATA length, which can be 0-8 bytes. Furthermore, the frame of Fig. 6 comprises a COMMAND instruction field in which various instructions can be issued to SUB32. The destination address DEST ADDR and the source address SOURCE ADDR are the bus addresses assigned to the interfaces 32 ^ .. 32N and the multiplexer 31 by the signaling bus 34. The DEVICE TYPE field, in turn, can be used to indicate a particular device such as a subscriber interface or bus. ·· Buffer inside SUB32. In the frame transmitted by the SUB32 (Figure 7) ;; · 20 DEVICE TYPE field indicates which subscriber line connection in the data field GEN.

The signaling information on the DATA applies. In the frame sent by the MCU: The T: DEVICE TYPE field tells which interface or circuit the COMMAND field operation or the data field GEN. The signaling information contained in DATA should be targeted. In a preferred embodiment of the invention, the BYTE COUNT field ··. The 25 most significant bit MSB is the read-write bit RAN, which tells you if you want to «· *

. ·. The MCU writes to a device (R / W = 0) or read from a device (RAN

• · · *; ./ = 1) · In a preferred embodiment of the invention, one bit of the SOURCE ADDRESS - • “·; · * field is an IRD / NORM bit. If this bit is “1”, the message is due to · an interruption by the subscriber line connection. Otherwise (IRD / NORM = "0"), the message is either an acknowledgment message from a previous write message or a response to a read request message. This allows the MCU to isolate the cause of the message directly from the message. It should be noted that Figures 6 and 7 show only one possible HDLC frame structure without limiting the invention thereto.

7 109074

Fig. 4 is a more detailed block diagram of a subscriber interface unit SUB32 according to a preferred embodiment of the invention. SUB32 comprises M subscriber connections, each of which is connected to a corresponding subscriber line 131 ... 13 ^. Each subscriber interface comprises a subscriber line interface circuit j SLIC41T ... 41M and a codec and control circuit 42, ... 42, ^ (CODEC & CONTROL).

The SLIC41 isolates the analog signal from the subscriber line 13 and supplies it as a signal to the IN codec and control circuit 42, which converts the signal to a PCM signal and supplies it to the local PCM bus 45. Similarly, the codec and control circuit 42 converts the received PCM signal signal OUT, which is supplied through SLIC41 to the subscriber line 13. In addition, various control and status signals CONTROL are transmitted between the codec and control circuit 42 and the SLIC41. Typical control signals include ON / OFF status information, ground key status information, polarity reversal control, ring voltage switching control, etc.

A local time division PCM bus 45 is coupled to each of the size deck and control circuits 42, ... 42N and the bus select circuit 43 (bus select). Way-; the selection circuit switches a specific time slot from the local PCM bus 45 to a time division; '·· for the data bus 33. The bus selection circuit 43 is controlled by the signaling interface circuit SIGNIF 44. /. i via control bus 47.

The signaling interface circuit SIGNIF signals with the MCU31 multiplexer via a message based signaling bus 34 using HDLC frames. The SIGNIF 44 is coupled to the local serial bus 46 to the codec and control circuits 42, ... 42 ^ so that it can read their status information, set their status, or: perform various operations on it according to the information transmitted by the MCU31.

• ·. ··. In its simplest form, the signaling interface circuit SIGNIF 44 can convert the information from the serial bus 46 into HDLCs · · frames transmitted on the data bus 34 to be transmitted to the MCU31. In the second transmission direction, SIGNIF 44 converts received HDLC frames into serial bus 46 into information to be transmitted. In addition, an interrupt signal INT, ... INTM is connected to each of the codec and control circuits 42, ... 42M to the signal circuit 30, SIGNIF 44. When line interface circuit state I | f changes, for example the ON-HOOK mode is activated, the corresponding codec and control circuit 42 transmits an interrupt INT1 ... M to the SIGNIF 44. The SIGNIF 44 then reads the status of that line interface circuit via the serial bus 46 and transmits the status change in the HDLC frame to the MCU31. signaling bus 34 8 109074. In the HDLC frame, the DECIVE TYPE field indicates from which codec and control circuit 42 the status information originates, and the IRD / NORM bit indicates the reason for the message. In the receiving direction, the DEVICE TYPE field in the HDLC frame indicates which codec and control circuit 42 is subject to the signaling message. SIGNIF will target op-5s to the circuit indicated by the DEVICE TYPE field. Some of the received HDLC frames may be addressed to the bus selection circuit 43. For example, in the hardware configuration step, the MCU31 may determine, by means of messages transmitted through the signaling bus 34, to which data bus 33 time slot the signal of each subscriber line should be connected. The MCU31 can do the same control dynamically for an already-10 call.

In a preferred embodiment of the invention, the SIGNIF 44 can perform essentially only one main operation at a time, with the sole exception of writing simultaneously through a serial bus and transmitting an acknowledgment message to the MCU31. Thus, the states of the SIGNIF 44 interface circuit can be clearly represented in a single state transition diagram, and in theory all SIGNIF 44 state machines could be connected to a single state machine. However, such a combined state machine • · would be too complex to be implemented economically. The states of the SIGNIF 44 • '·· are illustrated in Figure 8.

The SIGNIF 44 can be changed by three main external controls:; · 20 events: hardware reset, trigger frame reception and sig-

interrupt coding and control circuit 42. These events may trigger a process that is performed until SIGNIF 44 again reaches idle state. Referring to Figure 8, the hardware reset HW-RESET sets SIGNIF

: 44 to LOST mode, where it waits for a silent line, i.e. a pause sig- »<. ···. 25. In the case of the HDLC bus, "silent line" may mean, for example, eight or more consecutive "1" bit sequences. When the silent line is '·' reached, SIGNIF 44 enters IDLE mode where it waits for two other nor; · 'Painted a possible external event When SIGNIF 44 is in IDLE mode: it naturally goes back to LOST mode if HW-RESET occurs.

However, normally only two other events, i.e. receiving the HDLC flag from bus 34 (received FLAG) or receiving an interrupt from one of the interrupt lines INT1 ... INTn (INTERRUPT), will cause the SIGNIF 44 to be active.

9 109074

If SIGNIF 44 receives an HDLC flag (received), SIGNIF enters the receiving state and begins receiving serial data from bus 34. First, SIGNIF 44 checks the destination address DEST ADDR of the HDLC frame and compares it to its own address. If the addresses match, the 5 reception will continue. If the addresses do not match, it means that the message is not intended for this subscriber interface unit SUB32 and SIGNIF 44 goes into LOST mode where it waits for the incoming HDLC frame to expire.

If the addresses are matched, the CRC fields are checked at the end of the frame reception. If a CRC error is detected, SIGNIF 44 returns to 10 LOST modes. Otherwise, the decision to continue the process is made according to the status of the received R / W bit. If R / W = 0, which means a write message, then SIGNIF enters the acknowledgment transmission mode (TRANSM.ACK mode), where a write instruction acknowledgment message is sent to the MCU31. At the same time, writing is made to the circuit 42, ... 42, ^, or 43 indicated by the device type field, or possibly to the internal function register of the signaling circuit SIGNIF 44 of the signaling-15. When the acknowledgment and write operations are completed, SIGNIF 44 enters LOST mode.

If R / W = 1, then the received HDLC frame is a read request, then enter * * ·· read mode (READ). This READ mode reads, depending on the DEVICE TYPE field of the received frame, either the internal register of the SIGNIF 44 or any of the following: · 20 codec and control circuits 42. When the reading is completed (READ DONE), the transmission mode (TRANSMIT) is entered, in which the HDLC frame containing the read data is transmitted. After TRANSMIT mode, you will return to IDLE mode. If the upload fails (ARBITRATION LOST), a retransmission will be performed.

: Figure 5 is a block diagram of a principled • ·. ···, 25, multiplexing unit MCU31. The multiplexing section 53 is connected on one side to a digital transmission line 18 or 20, which is, for example, a 2 Mbit / s PCM cable. The other side of the multiplexer »/ / ring portion 53, comprising, for example, 64 kbit / s PCM signals, is connected to a bus interface circuit 52 (BUS IF). The bus interface circuit 52 couples 64 kbit / s PCM signals to specific time slots on the data bus 33. The operation of the bus interface circuit and the multiplexing section 53 is controlled by the control circuit 51. The control circuit 51 is further coupled to the signaling bus 34 through which it transmits according to the invention.

Preferred embodiments of the invention have been described above. It will be appreciated that alternative solutions and modifications will be apparent to those skilled in the art and may be practiced without departing from the spirit and scope of the appended claims.

• · • · »· · * * · • • * *» »*

Claims (9)

11 109074 Patent Claims A telecommunications network subscriber multiplexing device (16,14), comprising! a plurality of subscriber interface units (32), each of a multiplexing unit (14,16,21) coupled to a multichannel time divisional digital line (18, 20) for bidirectionally transmitting user information and signaling information with the second multiplexing device (21) and the AAI (10). a plurality of analog subscriber connections each having a subscriber line circuit (41) for coupling to a bidirectional two-wire subscriber line, 10 time-division data bus (33) for transmitting user information between the multiplexing unit and the subscriber interface units, the message-based comprising a communication means (44) coupled to said signaling channel (34) to send and receive signaling messages to the multiplexing unit. nucleus-based, * *; characterized in that the at least one subscriber interface unit (32) comprises * ·. : for signaling between the subscriber line connections (41) of the internal signaling bus (46) and the communication device (44), »1 t · 20 bus interface means (43) connected to said time division» · «1 ·: ·. the data bus (33), * # · the internal time-sharing data bus (45), the subscriber line connections (41), and. . for data transmission between the bus interface means (43), the I * _ interrupt line (INT1 ... INTM) from each subscriber line interface (41) to the communication *: * 25 to the telecommunication means (44), status * · · ... · to send information in a signaling message to the multiplexing unit. A subscriber multiplexing device according to claim 1, characterized in that the signaling channel is a separate signaling path (34). »♦ The subscriber multiplexing device according to claim 1, characterized in that the signaling channel is a single time slot of a time division data bus. The subscriber multiplexing device according to claim 1, 2 or 3, characterized in that each subscriber interface unit (32) is arranged to send signaling messages to the multiplexing unit (MCU) 512 to 109074 only in response to internal state changes or a message from the multiplexing unit. The subscriber multiplexing device according to claim 4, characterized in that the internal state changes include at least a transition from on-hook to off-hook and a transition from off-hook to on-hook. The subscriber multiplexing device according to claim 1, characterized in that the communication means (44) is arranged to control the bus interface means (43) in response to signaling messages transmitted by the multiplexing unit (MCU). The subscriber multiplexing device according to claim 1 or 6, characterized in that the communication means (44) is arranged to read the state of the subscriber line interface (41, 42) in response to a read message sent by the multiplexing unit (MCU) and transmit the read state information in the signaling message to the multiplexing unit (MCU). A subscriber multiplexer according to any one of the preceding claims, characterized in that the multiplexing unit (MCU) and each of the wide access units (32) have their own signaling channel (34) addresses and signaling :. the message is a protocol data unit comprising at least a destination address and signaling information. »1;: · 20 A subscriber multiplex according to any one of the preceding claims. a ringing device, characterized in that the protocol used on the signaling channel (34) is: T: one of the following: High Level Data Link Protocol (HDLC), commonly known as Advance Data Communication: Control Procedures (ADCCP), LAP- B (Link Access Procedure, Balanced) and SDLC>. ·. 25 (Synchro-nous Data Link Control). I t f * · * 1 # i · •>! I I '1 I <1 <«f I 1 109074