Subscriber node of a digital data transmission system.

The invention relates to a subscriber node of a digital communications system for bidirectional transmission of communication signals according to the preamble of claim. 1

As subscriber nodes that unit of a digital communication system can be seen, in which the message signals, for example are coming from an exchange forth prepared, for transfers to the individual subscriber terminals in consideration of the existing network. Here are frequently on the directed to the subscriber terminals side of the subscriber access node connections are available, in which a plurality of terminals of a switch are summarized. Are now in the front-end facility less channels are required than is available to it, are occupied channels in the exchange in this way, the use by any subscriber who the.

From EP 0318331 A1 an optical communication system is known, wherein the message transmission between subscriber nodes and subscribers through a TDM-multiplexed in the downlink direction, ie from the central office to the subscribers, and a TDMA-multiplexed in the uplink direction, ie from the subscribers to the switching center , is carried out. The example to the exchange-looking time-multiplexed data signals from the participants herkommenden time division multiplexed digital signals to a subscriber node in otherwise shared processed, converted. This conversion takes place in the subscriber node. The message transmission between subscriber nodes and front-end facility is via glass fibers. An additional distribution of time-division multiplex signals are outside of the subscriber access node by optical couplers.

The invention is based on the object of realizing this transformation of time-division multiplexed signals and distributing these technically less complex and more flexible.

The object is solved by the features of claim 1.

Further embodiments of the invention are disclosed in the remaining claims and the rest of the description.

A particular advantage of the invention is that time slots can be connected in any assignment and order in time division for individual subscriber terminals between the subscriber terminals and the exchanges.

An embodiment is described below in reference to FIGS. 1 to 3 Show it:<ul><li>FIG. 1 is a block diagram of the subscriber access node according to the invention containing optical communication system,</li><li>Fig. 2 responsible for the transmission in the downlink direction latch, on the expiry of the conversion of the time-division multiplexed digital signal, and the switching of the connection, and</li><li>Fig. 3 responsible for the upstream transmission buffer on the conversion of the expiry of the time-division multiplexed digital signal, and the switching of the connection.</li></ul>

In Fig. 1, the embodiment of a digital optical Überragungssystems 301 visible to the subscriber node 300 according to the invention. In the center of the connection node 300 is surrounded with a chain line. On the left is a digital switching center VS1 with outputs and inputs for 2-Mbit / s time division multiplexed signals, a digital switching center VS2 with other outputs and inputs (instead of them, another, an analog switch could stand), a device D for Datexverbindung, a device F for a remote control connection and device FV for leased lines. The above example enumerated devices can be assembled in any other desired type.

The these devices facing terminals of the terminal node 300 form an interface for digital A 2Mbit / s time division multiplexed signals at a frame duration of 125 microseconds. For all of the above devices fulfill these interface condition, it is provided that between the digital switching center VS2 (analog switch), the Datexgerät D, the device F and the devices FV, ​​insofar as is necessary, an adaptation circuit 314 is mounted, the transmission, the bit rate of the compounds to the desired 2 MBit s adapted / and optionally, if analog signals are present, performs an analog-to-digital conversion. These adaptation circuits 314 are known as such.

On the right side of the front-end facility 324 is representative of a plurality of front-end equipment ready. At this, several Community ports, of which again only one common terminal is ready 311, angeschlsossen. The Community Connections 311 are connected via optical fiber 319 with the front-end facility 324th Each common terminal 311 are in turn associated with a plurality of subscriber terminals 313th Each front-end facility 324 is connected via an optical fiber 318 to the terminal node 300th The transmission bit rate on the optical waveguide 318 is net 12 Mbit / s. The same applies to the not shown front-end equipment, which are connected to terminal node 300, so that the terminals of the front-end equipment form an interface B of the connecting node 300 with a uniform transmission bit rate. The via connections at the interface B transmitted digital signals are each time-division multiplex signals with a frame clock period of one millisecond.

The terminal node 300 thus has two types of connections: a first type with 144 electrical 2 Mbit / s ports at the interface A and a second type with 24 optical 12-Mbit / s ports at the interface B.

To terminal node 300, the request is found that at the terminals 1 to 144 of A interface signals applied to the terminals 1 to 24 are switched through the interface B. The following should be noted: The incoming to the terminals 1 to 144 responses are time-multiplexed signals (TDM), which are assembled in time division multiplexing of a plurality of partial signals. The same applies to the appearing at the interface B at the terminals 1 to 24 output signals. This also applies in the reverse direction. In the embodiment of interface B are respectively input signals in the reverse direction in the terminals 1 to 24, which are composed in the time division multiple access (TDMA). The terminal node 300 now has the task of forming from the incoming time division multiplexed signals new time-division multiplex signals by composed any part signals of the incoming time-division multiplex signals in any controllable compilation and order to a new time-division multiplex signal, and this on the respective opposite output interface to existing connections there.

The request is determined by the particular configuration of latches 303, which consist of a first latch 304 and second latch 305, are met. In order to make the operation of the latch 303 easier to understand, the transmission in the downlink direction will be explained with reference to FIG. 2.

The first latch 304 consists of a number of sub-memories 11, 21, 31, 41, ...; 12, 13, 14, ..., which are arranged in matrix form in 24 rows and 24 columns. He has 24 inputs E1 to E24 and 24 outputs A1 to A24. The inputs of the in each case to one line of sub-memories are connected in parallel with one of the inputs E1 to E24, for example, the inputs to the memory part 11, 21, 31, 41, ... to the input E1 of the intermediate store. From 24 outputs A1 to A24 each one is connected to the outputs of horizontal in a column part storing, eg A2 has the outputs of the partial memories 21, 22, 23, 24, .... In addition to the data input and the data output of each partial memory an input RA for read addresses and an input WA for write addresses. By caching the content at the inputs E1 to E24 incoming frame of the time division multiplexed signals, in other words, the part signals contained in these, the desired possibility is created to transmit the sub-signals within the frame from the port B in a different order further than in the order in which they occur at the interface A in any frame from there incoming time division multiplexed signals. All signals, ie data words or part signals an example at the input E1 adjacent frame are ... enrolled in each of the 24 part memory 11, 21, 31, 41, each partial signal, a separate memory (not shown), the own read address RA is and own write address WA is provided, assigned. The individual memory locations (not shown) are as so-called FIFO (first in first out) is formed wherein the first written data are read out again as the first. The writing and reading of data in the buffer memory 303 is done simultaneously. The inputs for the write address WA of all sub-memories are connected to a counter 307th The inputs for the read addresses RA of all the sub-memories are connected to a table memory 308, which is implemented as memory of a microprocessor μP1 and connected to the counter 307th The reading of the memory part erfolgf delayed by a frame clock period with respect to the writing, since it appears that in a frame rear part lying signal must be read before a front of it part signal.

In the following the function of the responsible for the downlink direction the first latch 304 will be explained. the context of the incoming message signals are applied to the inputs E1 to E24. Each part of a frame signal is written into each memory part, for example does not use the sub-signals in an incoming E1 frame in the memory part 11, 21, 31, 41, .... The preambles of the frames are continued. Each part has a memory the number of time slots of a frame, that is, sub-signals of a frame according to the number of addressable storage locations. The storage capacity of a memory location is eight bits, since each of the part signals contained in a frame is a data word of 8 bits. Read address inputs RA of all the sub-memory 11, ..., 12, ..., 13, ..., 14, ... are connected to the counter 307, the clock period is equal to the length of a time slot of the frame. The write address inputs WA of all sub-memories are connected to the table memory 308, which is connected to the microprocessor μP1. The counter 307 determines the timing in which the table memory 308 outputs the read addresses.

With the aid of the microprocessor μP1, the table memory 308 and the counter 307, it is possible to read from each of the 24 input signals any part of signal to each of the outputs A1 to A24, and this in any order. The prerequisite is created by the beschriehbenen memory structure which ensures that connected each output of the memory with outputs of partial memories that store the partial signals of all the frames received at the inputs E1 to E24, so that each output of all the content of all frames received access Has.

To sum up the outgoing at an output sub-signals to a frame, the output of another part of the memory 10, 20, 30, 40 is connected to each output A1 to A24, ... connected, which contains a plurality of addressable memory locations and as the other part of memory 11, 12 , 13, 14, ... one connected to the counter 307 read address input RA and a memory 308 connected to the write address input WA has and receives its data to form the preambles of a microprocessor μP0.

In Fig. 3 the charge of message transmission in the uplink second latch 305 is ready. He has, as the first latch 304, 24 signal inputs E1 to E24 and 24 signal outputs A1 to A24 which contained each with 24 in a column or row, arranged in a matrix sub-memories are connected in parallel. Inputs E1 to E24 are connected to the inputs of the sub-memory and the outputs A1 to A24 with the outputs of the memory part. The operation of the matrix-shaped arrangement forming part of the memory corresponding to the description of the first part 304 (Fig. 2). The main difference lies in the arrangement of the additional partial memories 10, 20, 30, 40, whose inputs are connected to the inputs E1 to E24. The additional partial memories 10, 20, 30, 40, ... are in the buffer 305 for receiving the preambles of the inputs E to E24 and for forwarding the preambles respectively to one related to its output microprocessor μPA1, μPA2, ... connected ,

About this microprocessors μPA1, μPA2, ... in conjunction with a central microprocessor μP0 (Fig. 1), the evaluation of the received TDMA frame and the received TDMA preamble and the formation of the TDM frame and TDM preamble for which takes place further upstream transmission. The scope of the TDM signals to be transmitted from the terminal node 300 in the upward direction, ... formed with the help of sub-memories 251, 252, 253, 254, whose outputs are connected to the outputs A1 to A24 of the latch 305 and the inputs the central microprocessor μP0 connected.

The interaction of the individual microprocessors μP0, μP1, μP2, μPA1, μPA2, ... in conjunction with the entire digital communications system controlling unit, which is referred to herein as network management 320, is presented below. It is assumed that the network management 320 the best connectivity between the terminals of the interface A and those of the interface B thanks to information about the availability of the terminals 1 to 144 of the interface A, the allocation of the related institutions VS1, VS2, D, F and FV, the assignment of the ports 1 to 24 of the interface B, the assignment of the associated front-end equipment 324, the type and number of the connected community connections 311 and know their availability. Based on this information, the network management 320 is able to determine the best connection between the terminals 1 to 144 of interface A and the terminals 1 to 24 of the interface B, which it strives to ports 1 through 144 of the interface A fully as possible to prove what is necessary particularly when individual connections are 1 to 24 at the interface B not fully occupied. This may occur when a front-end facility 324 is set in a sparsely populated area with only a few participants.

The cheapest way divides the network management 320 via the microprocessor μP0 microprocessor uP1 for transmission in the downlink and the microprocessor μP2 for upstream transmission with. The transmission paths in upward and downward directions do not need to, but may be the same.

The network management 320 is known, the position of the time slots for a subscriber under during transmission in up and down direction at both ports A and B, according to it divides the microprocessors μP1 and μP2 via the microprocessor μP0 with the order in which sub-signals for the formation of the corresponding frame to be read out from the buffer memory.

The Network Management 320 are also known, the structure of each frame. It tells the microprocessor μP0 which the structure to be transmitted in the uplink frame at the interface B has. Likewise, it tells the microprocessor μP1, what kind of structure to be transmitted in the downlink frame on the interface. Microprocessors μPA1, μPA2 ... get their information each from the preamble of the incoming at the interface B in the uplink communication signals, which may contain for example information about the access of a new participant. Microprocessors μPA1, μPA2 ... share their information with the central microprocessor μP0, who possibly also, for example, when a participant joins or is deleted, the network management 320 communicates this information in the formation of the preamble of each frame into account and.

The interface of the A subscriber node 300 has 144 electrical connections with a transmission bit rate of 2 Mbit / s, interface B, however, 24 optical connections with a transmission bit rate of 12 Mbit / s. The adjustment takes place firstly through multiplexer / demultiplexer 309, each six connections with a transmission bit rate of 2 Mbit / s summed to a terminal at a transmission bit rate of 12 Mbit / s. Each of the 12-Mbit / s ports of a multiplexer / demultiplexer is coupled to one of the inputs E1 to E24 of the first latch 304 and one of the outputs A1 to A24 of the second latch 305th Between each one of the terminals of the interface A and the multiplexer 309, a coder / decoder device 321, for example, is converted HDB3-coded signals into binary signals a switching center or vice versa. The interface corresponds to the interface A G.703 of CCITT Recommendations. The recommendation is a transmission bit rate of an integral multiple of 64 kbit / s.

Inputs E1 to E24 of the second latch 305 and the outputs A1 to A24 of the first Zwiwschenspeichers 304 are each connected to a multiplexer / demultiplexer 322, the / s or the "net" -Übertragungs bit rate of 12 Mbps in a higher transmission bit rate . a lower transmission bit rate converts, since the effective transmission bit rate between the terminal node 300 and the common terminal 311 due to the connected to the TDM / TDMA system protection periods between bursts of data and the type of communication method used here, in which periodically alternate in downward - is transmitted and upward direction, higher than 12 Mbit / s to about 30 Mbit / s. Between the multiplexers / demultiplexers 322 and the optical connectors 1 to 24 of the B interface electrical-optical converter 323 are arranged.

Each terminal between the latches 303 and a multiplexer 322, ... connected to one of the microprocessors UPA1, UPA2. Microprocessors UPA1, UPA2, ... are connected in parallel with the central microprocessor UP0. Microprocessor UP0 is, as described above, connected to the latches 303, the microprocessors and uP1 uP2 and the network management 320th

The terminal node according to the invention 300 is present in a slightly different kind, not only for a communication system 301 but, if instead of the electrical-optical converter 323, a transmitting and receiving device of a radio link or satellite transmission system is arranged and at the subscriber end corresponding base units and relay stations or satellites are also applicable for such communication systems. Further, the communication signals between the connection nodes and the subscribers can be transmitted via electrical leads.

The invention can also be used in connection nodes where between the two ports A and B there is no conversion of the transmission bit rate, or no electrical-to-optical conversion.

Since, in the embodiment, the communication takes place alternately in the two directions periodically on an optical carrier, a coupled via a fiber coupling to the optical fiber 318 wideband signal can also be transmitted to the subscribers 313th

At the interface A of the terminal node 300 need not necessarily a signal having a transmission bit rate of 2 Mbit / s or 1.5 Mbit / s (SONET) rest, it can also be a message signal with a higher transmission bit rate, for example, a wideband signal with a transmission bit rate of 140 Mbit / s are present.

Functions, such as monitoring and control function of a communication system are well known and are therefore not explained in detail. You can, as the operation of a TDM / TDMA system, for example the document EP 0318331 A1 are taken. Instead of the TDM / TDMA system can also use other time-division multiplexing systems, as for example, be a bi-directional TDM system used.