DE3624334A1 - MEDIATION DEVICE - Google Patents

Description

The invention relates to a switching device for Switching of channels in time division multiplex the preamble of the main claim, the so-called statistical multiplexing is used.

With statistical multiplexing, the transmission speed is of the time division multiplex signal less than that Sum of the transmission speeds of each this signal summarized partial signals (input channels). This is possible because of the traffic is of a statistical nature (according to the formula of Erlang). It follows that a given input channel a predetermined position within the multiplex structure (Time frame). This is in contrast to which is common in conventional multiplexing.

Since the channel assignment is not fixed, statistical Multiplexing constantly signals the current distribution of the channels will. This signaling information can Data added as a package or transmitted separately. The term "statistical multiplexing" is sometimes used this way used that included the two choices are. In the present invention, however, only the considered separate signaling.  

By an intermediary according to the teaching of The main claim is the signaling task solved. Advantageous configurations are See subclaims.

The invention is described below using an exemplary embodiment with the help of the attached drawing explained in more detail.

Fig. 1 shows a highly simplified block diagram of a switching device according to the invention.

Fig. 2 and 3 show timing charts.

Modern telecommunications systems require a large number of services. To cope with this is a high degree flexibility required. These services include both Voice and broadband services like video, as well fast and slow data transfer. Here are Systems with variable transmission speed (bit rate) he wishes.

The system to be described here uses time division multiplexing, with statistical multiplexing. In doing so different levels of the multiplex hierarchy are used. A lower level works with 2048 kbit / s (also as 2 Mbit / s), while a higher level with 34 Mbits / s or more works. Lower levels can be in higher levels can be fitted.

In the lower stage there is a frame repetition frequency of 8 kHz (125 µs). The frames have to be framed summarized at 250 Hz (4 ms). The bandwidth  one channel corresponds to 8 kbit / s. Now, for example 8 channels can be used to form a voice channel. However, it can also generate any whole multiple of 8 kbit / s will. An 8 kbit / s channel can also be divided will.

The signaling takes place by means of bit cards, whereby the Information is transmitted in bundles, for which a signaling frame is used. This will make the recipient of the bit stream communicated how the individual channels within of the superframe are arranged. Preferably such a signaling bundle once per superframe Posted. It is also possible, albeit in general less advantageous, more or less than once per overframe to signal. The following is a signaling per superframe, assuming nothing other is indicated.

In the lower multiplex stage there is the possibility to work both in packets and not in packets. Packets are transmitted transparently. For the internal Signaling becomes, for example, the signaling method used according to CCITT No. 7.

The frame frequency and the repetition frequency of the superframe are the same in the higher multiplex stage as in the lower level. The bandwidth of a channel corresponds 64 kbit / s, for example. It can be done in multiples of 64 kbit / s can be increased. Several such 64 kbit / s Channels are jointly assigned to the lower level. It the same bundle signaling is used, as with the lower level, the lower level being transparent is. Again, as in the lower level to be worked in packages or not in packages.  

With such a system, speech and video become without Do not transmit delay in packets. Asynchronous data and those that only synronize to another network are transmitted in packets. Stand in this system quick signaling options available, which there are excellent opportunities at changing traffic to change the bandwidth and to congestion to react. It also exists in a simple way the possibility of speaking with conventional networks to work together.

If the traffic requires it, the bandwidth can be split are between statistically multiplexed traffic and parcel traffic, the division within one Fixed framework or can vary as required. Packets can be fragmented to one Reach over the frame, for example, according to Rules of X.25 are worked.

At this point, reference is made to Fig. 1, which shows a switching device which is constructed as mentioned above, but operates in the higher stage of the multiplex with 140 Mbit / s. The higher level is referred to here as the broadband part and the lower level as the narrowband part. This switching device contains the following elements:

TS1 (time switch 1), available twice, is a time Coupling stage that process 2000 channels with 64 kbit / s each can, the word width is 8 bits.

TS2 (time switch 2), available twice, is a time coupling stage for 2000 channels with 8 kbit / s each, with one 1 bit depth.  

SS1 (space switch 1), is a space coupling stage with 128 × 128 crosspoints, each designed for 8 bits.

SS2 (space switch 2) is also a space coupling stage with 128 × 128 crosspoints, but with 1 bit per Crosspoint.

HLDM (high level demultiplexer) is a demultiplexer at the higher level of the multiplex level, the Input data stream of 140 Mbit / s for switching purposes divided into channels of 64 kbit / s. As will be shown at least one such channel goes to the one below written assembly LLDM.

LLDM (low level demultiplexer) is a demultiplexer the lower level, which has both a data stream of 2 Mbit / s as well as the data stream with 64 kbit / s from the HLDM divided into channels with 8 kbit / s, which are then in the lower Level.

HLM (high level multiplexer) is a multiplexer on the higher level, the individual 64 kbit / s channels again forms a data stream of 140 Mbit / s. The channels with 64 kbit / s come on the one hand from the coupling network TS1- SS1-TS1 and on the other hand from that described below Multiplexer LLM.

LLM (low level multiplexer) is a multiplexer on the lower level, the one from channels with 8 kbit / s again Data stream of 2 Mbit / s forms. The channels with 8 kbit / s come from the network TS2-SS2-TS2.

Such a switching device can have multiple data streams with 2 Mbit / s and also several data streams with 140 Mbit / s to process. Instead of the specified transmission speeds  can also be used without basically changes about.

Within the system, for example to establish a connection and dismantling, messages exchanged, as in the Publication EP-A-O 1 25 744. On the Connection line, however, the channel division in the form periodically repeated bit cards that transmit the respective status of all possible participants included. An algorithm for channel assignment is used for this, that builds on this status. The receiving end then responds to status changes based on the ongoing transmitted bit cards can be recognized.

If a connection is now to be set up, the subscriber is assigned a certain number of bits in the bit card. This corresponds to a certain bandwidth, according to its maximum need for channels. In this way, the far end is informed that subscriber A is assigned bits 5-12 on the bit card and that its destination address is B. Ideally, the bit card is transmitted as the head of a frame. However, it has been shown that it is necessary to send the bit card in the previous superframe in order to be able to trigger the required processes in good time.

Fig. 2 shows an example in which each bit represents a channel. Bit 1 has been assigned to subscriber G and is active. Bits 2-4 assign three channels to subscriber H. He is currently not active. Subscriber A is currently using 4 of 8 possible channels. Under this condition, G receives channel 1, A receives channels 2-5 and H remains without channel. If H now becomes active and requires all 3 channels to which it is entitled, A is switched to channels 5-8. The ratio of the number of bits in the bit card to the number of channels, including any subdivided channels, is the signal interpolation gain (SI). It is determined on the basis of the expected traffic behavior. This results in some loss or delay.

The signaling does not necessarily have to be exactly once per Frame. It can be done more or less often if this is the on-off behavior of the language required.

If part of a channel is required, during the Connection establishment specified a subchannel. The distant Ende notes this subchannel in the superframe and processes it only the information contained in the affected Frame of the super frame is included. In this case, too activity is indicated by a bit in the bit map signals.

The occurrence of overload is considered below be, assuming that the product the number of users with their maximum Data rate is limited. If this limit is reached, then new calls are rejected. This is done across the board through the whole network by all switching facilities reject new calls even if they are not are overloaded. Tries a higher priority service a connection establishment, so in case of overload a connection of a lower priority service canceled with the same bandwidth. With such a System overload occurs randomly and is short Duration.  

However, in a preferred technique, they are packaged transmitted data stopped in the event of an overload and delayed, thereby temporarily adding additional bandwidth to provide for the language. Fast data, which are synchronous to the network should not be delayed to give priority to language. With language can if necessary, the transmission quality, for example omitting bits may deteriorate in the short term, however, language delay should generally not done.

There are moving picture transmission methods with variable Transmission speed work and at those rapid changes in the image content a larger amount of data have as a consequence. A way to prevent overload in this case would be at the starting point to delay the changes. At a switching center in the course of such a transmission link in this case information may perish.

Network participants operating over broadband connection lines connected with narrowband services can also reach those participants who only have Narrow band connection lines are connected. The 2 Mbit / s structure is therefore in the broadband structure included, either as a whole or by channel. in the The first case is a 2 Mbit / s complex as a fixed one Channel viewed in broadband structure while in second case, the 2 Mbit / s in the channels forming it split and nested with broadband channels.

However, a compromise solution was chosen in which the services with less than 2 Mbit / s a number of Is assigned to channels in broadband multiplex. This sets assumes that broadband channels are narrower than 2 Mbit / s.  

Such channels become an integral part of the overall framework assigned. The signaling can then either be outside of this band take place in a separate central channel or it can in the case of slower services within of the band within the allocated bandwidth.

Building on the previous one is now an example statistical multiplexing with frame and signaling Structures described.

At a transmission speed of 2048 kbit / s on the lower level, channel 0 of the synchronization serve while channel 16 are used as needed can. A base channel is designed for 8 kbit / s, so that Channel 0 contains eight such basic channels. So there are voice transmissions possible with 64 kbit / s. In the lowest Hierarchy is the transfer rate 250 bit / s, an overframe then takes 4 ms. In such a subchannel with 250 bit / s can handle data in packet form with 75 bit / s and 150 bit / s can be transmitted. The signaling frame duration is also 4 ms. This is reasonable Reaction to bundles that occur is possible. A frame duration is 125 µs. This makes speech a sample without delay transmitted for sample value and so can be done without difficulty switch to a conventional network.

A disadvantage of the low bandwidth in the lower hierarchy level is that speech, which is coded with 8 bits in PCM, requires 8 such channels. If the signaling method with bit cards is used here, the signaling is complex. If there are 8-bit speech channels, it may be advantageous to use a 4-bit word for each speech channel as shown in Fig. 3, assuming that these channels are occupied according to a predetermined algorithm. One bit represents the status of this overall channel, the other three indicate how many channels are used, apart from one. With an active connection with 8 channels, all 4 bits are set. Subchannels are each identified by 1 bit. The entire channels take up the signaling frame from the beginning, the subchannels from the end. In the middle or near the middle there is usually an unused empty space. If 45 voice connections and a further 15 connections are allowed at the same time, 212 bits per superframe or 7 bits per frame are required. This requires 7 of the 248 channels available.

The signaling for establishing and clearing the connection takes place via messages stating one or more for this Associate assigned channels, each capable of are up to 8 channels on a statistical basis expand to respond to peaks in demand.

In this example, the signaling information transmitted every 4 ms. As already indicated, it will the bit card is preferably sent in that superframe, that precedes that to whom the information is assigned is. This provides the time which is required to make the necessary settings to do.

At the higher level, 64 kbit / s channels are used. Up to 31 channels of the lower level are the assigned higher level. The signaling of the lower Level is included. Those channels that reserved for the lower level within the higher level are semi-permanently active,  d. that is, they are at the higher level as a kind of dedicated line considered.

Now the synchronization should be considered if a number of statistically multiplexed connection paths be used together. Is only a connecting path affected, so change at different times Conditions. This is made more difficult when two or more Connection paths are shared because here different kinds of delays meet. This is done at the receiving end by additional Delays to a full frame or even too two extra frames added.

Now a slightly higher processing effort is in purchase taken to the total delays occurring and reduce the associated memory requirements. Instead of the necessary ones for all channels used Refreshing information once per superframe is for part of the channels the occupancy information with each one Refreshed frame. Out of 128 channels, 4 refreshed once per frame and the bit card will divided over the individual frames of a superframe. The split information is still within of the previous superframe.

Claims (8)

1. Switching device for switching time-division multiplexing channels, the bandwidth of at least some of the channels being changeable by changing the number of bits assigned to this channel within a time-division multiplexing frame (time frame), characterized in that each time frame is a bundle is associated with signaling information that the signaling information contains bits which together form a bit map, that the bit map indicates which bits of a time frame form a specific channel and that at least some of the channels automatically assign the bits within the time frame depending on the respective bandwidth of the channels with changeable bandwidth is changed. 2. Switching device according to claim 1, characterized characterized in that a participant when establishing a connection the maximum bandwidth available to him by reservation the corresponding number of bits within one Time frame is assigned that during the current Connection the number of bits each reduced so far is how this is the bandwidth actually needed corresponds and that the bits following in the time frame, the other connections are assigned to the places of the bits being released so that the time frame is filled with useful information from the front end.   3. Switching device according to claim 1 or 2, characterized in that several time frames each are summarized in an overframe and that the Distribution of the bits in a bundle indicating a superframe of signaling information in the preceding one of this superframe Superframe is transmitted, so the time is made available for the different Settings is required. 4. Switching device according to one of the claims 1 to 3, characterized in that the time frame in the same system channels are divided among themselves that one bit of the bit card is assigned to each system channel, that those coming from outside or going outside Channels in the switching center via a system channel or several combined system channels and that at least part of the system channels in two or more subchannels with less bandwidth is split, these subchannels in the same How the system channels are used. 5. Switching device according to claim 4, characterized characterized that the whole used System channels fill up the timeframe from the beginning, while used subchannels Fill up the time frame from the end. 6. Switching device according to one of the claims 1 to 5, characterized in that at least one of the system channels for the signaling information at Connection establishment and clearing is determined. 7. Switching device according to one of the claims 1 to 6, characterized in that at least one  Coupling device of the first type (TS1-SS1-TS1) is present, those for switching signals at a higher multiplex level it is provided that at least one coupling device second type (TS2-SS2-TS2) is available for Switching of signals at a low multiplex level it is provided that each coupling device is first Type (TS1-SS1-TS1) between the outputs of a demultiplexer first type (HLDM) and the inputs of a multiplexer first type (HLM) is arranged that each coupling device second type (TS2-SS2-TS2) between the outputs a second type demultiplexer (LLDM) and the Inputs of a multiplexer of the second type (LLM) arranged is that at least one output of a demultiplexer is first Type (HLDM) to a coupling device of the second type (TS2- SS2-TS2) leads and that at least one input of a multiplexer first type (HLM) from a coupling device second type (TS2-SS2-TS2) receives incoming information. 8. Switching device according to one of the claims 1 to 7, characterized in that in the bit map contained information in the course of several successive Time frame is refreshed.