DE2659533A1 - Signal transmission system with several subscriber stations - has calling station which finds two free time channels, transmits call and later passes message through first channel - Google Patents

Abstract

Signals are transmitted in a communication system with a number of subscriber stations and a clock pulse generator, all connected to a common TDM line loop. The clock pulse generator periodically transmits synchronisation blocks to which the subscriber stations are synchronised. The spacing between them is divided in a number N of time channels. The loop propagation time a is an integral multiple of the duration of a time channel. In order to establish a connection a subscriber station automatically finds two free time channels i and i + a, and transmits over the i-th channel the receiving station code, and its message over the same channel after connection is established.

Description

Method for message transmission in a time multiplex-

system with transmission means arranged in a loop. The invention relates to a time division multiplex messaging system in which all participants can interact with one another at will can be connected, all participants to a looped arranged transmission means connected and their messages using the multiple access method on the transmission medium or received from it.

A number of proposals have become known, such as these Time division multiplex messaging systems with multiple access and closed loops Time multiple transmission path ke can be realized. There is agreement in each case the arrangement shown in FIG. 1 and the subscriber stations in the TS and TG represent a central clock generator. In order to avoid, that sent messages circulate continuously on the loop, are in each case the messages at their destination from the receiving subscriber station from the time-division multiplexed message stream.

For addressing the messages, i.e. the identification of the receiving Subscriber station, there are two options: 1. Each message block is assigned a Address block prefixed.

This is described in detail in DT-OS 2 151 016, for example. The transmission of the message blocks from the individual subscriber stations is included only to a given time channel grid, but not to a specific one Time channel bound within a time division multiplex frame on the transmission medium.

2. The message blocks of a single message link between two subscriber stations are each on precisely defined time channels within of the time division multiplex frame of the transmission medium, as in the DT-AS 1 804 624. The serial number of the time channel used for the transmission is therefore, when a connection is established, at the same time the destination address and a separate one Address block is not necessary.

However, both methods have disadvantages: In the first method Icann there is mutual blocking of the.

Transmission route come when there is no statistical assignment of news sources and sinks are present (cf. 13. Aviltzhak "lieavy traffic characteristics of a circular data network, Bell Syst. techn. J. 50 (1971), pp. 2521-2549).

As a result of this state, there are sometimes considerable temporary stores necessary in the subscriber stations. In the case of the one described in DT-OS 2,332,599 Execution, the loop runtime is constantly changing. This is in both cases a sequence of equidistant message blocks from the message source no longer occur equidistantly at the receiving subscriber station. This leads at high transmission speeds to considerable difficulties with Demultiplexing the blocks from the time-division multiplexed message flow. Through the attached In addition, the address becomes the proportion that can be used for message transmission Transmission capacity reduced considerably.

The aforementioned difficulties become complete with the second method overcome. However, for reasons of time channel synchronization, the loop runtime must be here be a whole multiple of the frame duration. This will, as suggested in the DT-AS 1 804 624, achieved by adding a buffer memory.

The use of buffer storage tanks according to DT-AS 1 80 / l 62lt is b (.i 'ic: loop systems with medium transfer rates and ioidit too large numbers of Time channels per frame a useful option. However, the transfer rate increases over 10 Mhz and thus the number of PCm time channels in the range over 150, the The effort for the buffer storage and the control required for it is considerable.

The task leading to the invention was to reduce the effort for the Significantly reduce caching.

The object is achieved as described in claim 1.

The reduction in memory requirements is achieved in that the Loop runtime no longer applies to whole areas of a time division multiplex frame Buffer memory is added, but only to whole multiples of a time channel. In the simplest case, for example, the runtime compensation is only the fraction of a time channel. As in the DT-AS 1 804 624 proposed to take place in the clock generator TG. Since news blocks that were transmitted in a time channel x after passing through the end of the loop occur in the time channel x + a, where a is the loop runtime (including runtime compensation) is an integral multiple of the time channel determined himself Regulations for establishing a connection within a loop system according to of the invention, which are given in the following I3 ('. writing of the system.

The method according to the invention will now be explained in more detail below.

The clock generator TG sends equidistant synchronization blocks to,, which each mark the beginning of the time division multiplex frame. Synchronizing blocks, which have circulated once in the loop are suppressed by the clock generator TG.

Jcd subscriber station TS synchronizes itself to these synchronization blocks. In addition to the synchronization blocks, the clock generator can generate further clock pulses sent out, for example at the beginning of each time channel (see K.D. Schenkel "An integrated 300 Mbit / s time division multiplex messaging system with decentralized switching Communications Z. 27 (1974) pp. 283-291), about the recovery of the transmission clock to facilitate in each subscriber station. With the help of the synchronization blocks and of the transmission clock, each subscriber station can convert the time division multiplex frame into a Subdivide the specified number of equal time channels and these time channels Mark within a frame counting.

For example, a frame contains N time cantiles with the order number 1 ... N, with the synchronization block being transmitted in time channel 1, and the entire Loop runtime including runtime compensation is a time channels.

If a subscriber station, for example TSi in FIG. 2, wants to use, iir other subscriber station TS2 set up a communication link, so it searches two free time channels i and i + a and occupied within the time division multiplex frame the time channel i through a call block which contains the address of the partial emitter station TS2 contains. All subscriber stations, including those on another communication link are involved, check the call block circulating in time channel i. The participant station TS2 recognizes the call, removes the call block from the time channel and adds to it Set a response block that can either contain a busy signal (if TS2 is already involved in another communication link) or a free signal (if TS2 is free). This response block runs in time channel i up to the Enc'e der Loop, runs through the clock generator TG and now appears unchanged in one Time channel to which the serial number i + a is assigned. The subscriber station TS1 thus takes the response block from the time channel i + a. For subsequent subscriber stations the time channel i + a is thus available for further connections. Is the connection built up, then i resp.

i + n transfer the message blocks (without additional addressing). When the connection is terminated, there are no message blocks in the time channels i and i + a are transmitted more and thus these time channels can be used for other purposes free. To distinguish between call and control blocks on the one hand and message blocks on the other hand, visualization characters can be used at an agreed point within the time channel (see above article by K.D. Schenkel in Nachrichtenentechn. Z. 27 (1974) pp. 283-291l by sending out a block of information in a time channel x and the removal of a block in the time channel x + a by the end of the connection Subscriber station (resp.

Removal of a block and transmission of a block in the time channel x the called subscriber station) are mutilated even during the transmission Blocks taken out from the subscriber station involved in a transmission itself.

Because of the running time a, the last time channels (N -a + 1, N - a + 3, ... N) of the time division multiplex frame not for the transmission of information between Subscriber stations are used, otherwise a disruptive overlay with the Contents of the time channels 1 ... a would occur. However, these time channels can for general "messages to all subscriber stations, the ones from Clock generator sent out1 can be used.

The transit time initially unknown to the individual subscriber stations a is determined by the clock generator TG and this value is then converted into an agreed Time channel (preferably in one of the time channels N - a + t ... N) to the individual Transfer subscriber stations.

The measurement of the transit time a is based on de. shown in Fig. 3a exemplary circuit and the pulse schedule of Fig. 3b explained.

The synchronous generator SyncG generates the synchronization block and if necessary further clock pulses to support the transmission clock recovery in the individual Subscriber stations. By means of the SYN signal, which identifies time channel 1 and resets the counters Zl and Z2, both counters are reset at the end of the first time channel started. Counter Zl emits a signal I1 at its output when a time channel is over. The time channel counter Z2 is incremented with this signal 11.

If the from the synchronous generator SyncG via the multiplexer M to the Transmission line L given synchronization block at the end of the transmission loop completely into the shift register chain S1 has arrived there the synchronizing block detection circuit Ul from a pulse I2, which the instant Reads the count of the counters Z1 and Z2 into the memories S2 and S3. The meter reading of Z2 now represents the running time a, whereas the counter reading of Zi is used, in order to control one of the gates U2 ..; Uk via a decoding device D known per se and thus to shorten the loop runtime to a whole multiple of a time channel. During each time frame, the content of the memory S3, which is the loop runtime a contains, transmitted to the subscriber station and in turn the new loop runtime measured. The circuit has the advantage that disrupted synchronization blocks do not lead to a falsification of the running time, since the previous value in S2 and S3 is retained.

Switch A is controlled by a counter, not shown, so that it is open during the time channels 1 ... a, around the time at the exit to keep time channels N - a + 1 .. N pending from oil away from the start of the loop.

The design of the subscriber station is not the subject of the invention. Its basic structure can be that described in DT-AS 1 804 624, for example Follow participant station.

Messages of different bandwidths can be in an inventive Telecommunication system using the method described in DT-OS 2 262 933 danii is particularly easy to transfer if the loop runtime a is a whole multiple the subframe length specified in DT-OS 2 262 933.

L e r s e i t e

Claims (3)

P a t e n t a n s p r ü c h e 1. Method for message transmission in a telecommunications system with a large number of subscriber stations and a clock generator, whereby the subscriber stations and the Takgeneratoran a loop-shaped closed gcfleinsame time division is connected and the clock generator periodically Synchronization blocks to which the subscriber stations synchronize and subdivide their time interval into a number N of time channels, thereby marked that the loop transit time a is an integer multiple of the time Length of a time channel is chosen that a subscriber station to establish a connection automatically searches for two not otherwise occupied time channels i and i + a on which i-th time channel sends out a call identifying the receiving station and after Establishing the connection instead of the call in the same time channel that is to be transmitted Sends out message. 2. The method according to claim 1, characterized in that the time channels N - a + 1 to N not for individual connections between subscriber stations, but can be used for the transmission of distribution information. 3. The method according to claim 1, characterized in that the Measurement of the loop runtime carried out by the clock generator and the value found a is communicated to the subscriber stations in an agreed time channel. 4, method according to claim 1 to 3, characterized in that all subscriber stations connected to the loop constantly the entire time multiplex frame monitor for a call addressed to them.