WO1998015157A1

WO1998015157A1 - Arrangement for interleaving data and signalling information

Info

Publication number: WO1998015157A1
Application number: PCT/SE1997/001621
Authority: WO
Inventors: Leif Isaksson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1996-10-01
Filing date: 1997-09-26
Publication date: 1998-04-09
Also published as: CN1239637A; NO991532L; SE9603598L; EP1010347A1; NO991532D0; SE511344C2; AU721715B2; SE9603598D0; AU4578697A

Abstract

The present invention relates to an arrangement and a method respectively for switching information at least in the form of data and signalling information wherein the signalling information at least partly is transported on a common channel signalling channel (14). The switching arrangement (10) comprises signalling handling means (12) for handling signalling information on said common channel signalling channel and data access means (11) handling data. The data access means (11) further comprises means or additional access means for handling signalling information on the common channel signalling channel and means for replacing idle information or filler information on the common channel signalling channel by data information.

Description

ARRANGEMENT FOR INTERLEAVING DATA AND SIGNALLING INFORMATION

TECHNICAL FIELD

The present invention relates to switching of information at least in the form of data and signalling information in e.g. a communications network. The signalling information for example relates to status information about connections, services and information about which channel is to be used for a given connection etc. Signalling is used both between subscriber equipment and exchange or switching arrangement and between different switching arrangements or exchanges. The invention particularly relates to a switching arrangement for switching information at least in the form of data and signalling information and to a method for transferring at least data information and signalling information between at least a first network node and a second network node in a communications network. Furthermore the invention relates to a switching point in a communications network which comprises a private branch exchange. Still further the invention relates to a communications network comprising at least a first and a second node between which data information and signalling information is transferred.

STATE OF THE ART

Signalling is among others used between various switching arrangements in a communications network, wherein the signalling information for example comprises information about A-number, B- number, services, communications channels to be used etc.

In modern telecommunication systems a common channel signalling channel is used, one example is for instance the so called D- channel in the integrated services digital network, ISDN. In the mostly used 2 Mbit connections (PCM (Pulse Code Modulated) systems) wherein one frame comprises 32 time slots, the D-channel is sent in time slot 16. Using standard transmission technology, the D-channel is generally transported either as a 64 kbps channel, a 16 kbps channel or as a V.24 based data channel such as a modem or some other kind of data network. Thus it is transported in a separate network which as such requires a considerable amount of equipment since it is separate from the data network and/or a network used for transportation of voice. If thus there are at least two networks, separate units for the separate networks are required as well as separate supervision, e.g. separate operation and maintenance systems etc. Furthermore such a system is not as flexible as would be desired.

In many implementations the capacity of the channel used for signalling purposes is only used to a very limited extent, e.g. only to some per cent or a few per cents. Particularly if there are network nodes in the network which only require a small number of simultaneous voice connections, the bandwidth, which often is leased, in some cases involving high costs, specifically intended for signalling purposes is only used to very a limited extent. If for example a node requires one ERLANG with a holding time of 180 seconds per call, it will use the signalling link for 20 calls per hour which represents a very small fraction of the leased capacity which for example may be a full 64 kbps channel. EP-A-0418851 relates to a control channel terminating interface for terminating the control channel signal at a digital multiplex transmission route. In this case information is spread over a several connections or a whole interface and not sent on a channel.

Motorola Technical Developments, Vol. 17, Dec. 1992, (USA), V. Fernandes "Enhanced transmission of data over common channel signalling number 7 links", page 145-150 discloses how the established telephony signal can be used for transfer of some data from time to time.

The drawback of the known arrangements is thus that they are not flexible, that for example leased bandwidth is not used to a sufficient extent but wasted, at least in several low bandwidth applications which is an important issue since leased lines may be very expensive. Furthermore higher costs and complicated solutions are required because there is needed more than one network to carry the information that needs to be transferred. Still further signalling information is not transported as fast as desired.

SUMMARY OF THE INVENTION

What is needed is therefore a switching arrangement at least for switching data and signalling information through which the channel used for signalling information, which e.g. may be leased or comprised in a public network such as ISDN or PSTN, is used in a more efficient manner than hitherto known. An arrangement is also needed through which switching of data and signalling information can be effected using one and the same network. Furthermore an arrangement is needed which is flexible, easy to implement and which does not require much equipment as compared to hitherto known arrangements. Furthermore an arrangement is needed which involve comparatively low maintenance costs. Still further an arrangement is needed which enables a fast switching, particularly of signalling information.

A network switching node or a switching point m a telecommunications network comprising a private branch exchange is also needed through which the above mentioned can be achieved. Still further a communications network comprising at least two switching nodes, or private branch exchanges, is needed which fulfils the above mentioned requirements.

A method for switching at least data information and signalling information through a number of switching arrangements m a communications network is also needed through which the m the foregoing discussed objects can be satisfied.

Still further a switching arrangement, a method and a telecom system are needed through which a rapid switching of signalling information is provided for.

Therefore a switching arrangement is provided wherein a data resource is used for signalling information and which comprises signalling handling means for handling signalling information on a signalling channel and data accessing means for handling data to/from a number of interfaces. Said data accessing means comprises means or additional access means for handling signalling information on a common channel signalling channel and means for replacing idle information or filler information on the common channel signalling channel by data information so that the bandwidth on the signalling channel not used for useful or real signalling information can be used for carrying data.

A network switching node comprising a private branch exchange is therefore also provided which comprises a switching matrix, data access means for accessing data over a number of data interfaces and signalling handling means receiving and transmitting signalling information. The data access means are arranged within the switching matrix of the private branch exchange and comprise means enabling the access of signalling information. A data resource is thus used for signalling information and signalling information to/from the signalling handling means is transferred via the data access means and signalling to/from the switching point is performed over a line, e.g. a data relaying link and the bandwidth on the signalling channel that is not used for carrying signalling information is used for carrying data. Thus, according to the invention a data resource is used for transfer of both signalling information and ata. It is therefore possible to minimize the bandwidth of the signalling channel.

A communications network is also provided which comprises at least a first and a second switching node, between which nodes at least data information and signalling information is transferred. Each switching node comprises a switching matrix m which are arranged data access means for data access and comprising means for the access of the signalling information. Each switching node further comprises signalling handling means wherein the data access means and the signalling handling means within each switching node communicate via a signalling connection line. The data access means further comprises means for replacing non-useful signalling information or filler information by data information so that the spare bandwidth on the signalling channel can be used for data information instead. Thus, according to the invention a data resource is used for transfer of both signalling information and data. It is therefore possible to minimize the bandwidth of the signalling channel. Still further a method is provided for transferring at least data information and signalling information between at least a first network node and a second network node m a communications network. When information is transferred from the first node to the second node, the method comprises the steps of: examining m the data access means if received signalling information from the signalling handling means over a signalling channel contains non-valid or idle information, replacing such (if existing) non-valid or idle information through data information. The data information and the valid signalling information is then advantageously packetized and sent over a link to the second network node. More particularly, in said second switching node the data information and the signalling information are separated and idle information may be added for sending to the signalling handling means whereafter the signalling information is output to the software of the second switching node which handles it m a known manner.

The data access means particularly comprises packet switching means or a frame relay switch. The data information and the signalling information may then be switched via said (for instance) packet switching means on a data relaying link to another switching arrangement. In an advantageous embodiment the data access means and the signalling information handling means communicate via a full-rate common channel signalling channel. However, m another embodiment the signalling information, and possibly filler information is transported m a subrate e.g. (16 kbps) channel. However, m this case some delay m the transmission of signalling information to the data access means from the signalling handling means will have to be accepted as compared to the full-rate case.

Advantageously the means for replacing idle information such as for example filler bits through data information are also capable of generating idle information such as for example filler bits, when signalling information is transferred to the signalling handling means from the data access means. In particular a full-rate connection to the signalling handling means is upheld.

In a particular embodiment the common channel signalling channel is the ISDN D-channel. In an advantageous embodiment the D-channel is transported as a 64 kbps channel. However in alternative embodiments as discussed above it is also possible to use a 16 kbps subrate connection between the data access means and the signalling handling means. If the common channel signalling channel, or particularly the D-channel, comprises idle information e.g. in the form of filler bits, these are removed in the data accessing means and replaced by data information and vice versa when receiving information from another switching arrangement. Thus, particularly filler bits in subrate channels can be replaced by data. In one particular embodiment the data-link connection on which data information and signalling information is transported comprises an X.25 packet mode interface or a frame relay user interface.

Generally signalling information is given a higher priority than data information. Advantageously the data accessing means of the switching arrangement provides access for almost any data interface such as for example V.24 (ITU-T), Ethernet, Token Ring (IEEE Standards) .

In a particularly advantageous embodiment the switching arrangement also provides for switching of voice and even more particularly compressed voice can be switched without previously being decompressed, i.e. voice can be switched in a compressed format. The switching arrangement then comprises signalling arranging means which at least comprises means for combining subrate channels transported in separate time slots in each of which only some of the bits are used for carrying information. Combined subrate channels are output on a full-rate transmission path or in subrate channels transported in a common time slot. In said signal arranging means are advantageously compressed speech multiplexed or combined with the data and the signalling information.

Still more particularly the switching arrangement comprises compressing/ decompressing means for handling incoming/outgoing voice calls for which the switching arrangement forms an originating and/or a terminating arrangement. Yet further the signalling arranging means advantageously comprise demultiplexing means for dividing a number of subrate channels transported in a common time slot containing compressed voice into a number of separate time slots for switching purposes. The subrate channels switched in separate time slots are combined with other subrate channels arranged in separate time slots also containing compressed voice and/or signalling information and/or data in said combining means before output.

The signal arranging means comprising compressing and multiplexing of voice are described in the Swedish patent application "Channel handling device, telecommunication node and telecommunication system comprising such a channel handling device as well as methods of transmitting signals", filed 01.10.96 with application number 9603590-2, i.e. on the same day and by the same applicant as the present application.

Advantageously the link connecting the switching arrangement with a further switching arrangement comprises a leased line such as e.g. a single or multiple 64 kbps line(s). Advantageously the data accessing means are arranged in the switching matrix of a private branch exchange (PBX or PABX) . Advantageously the signalling information handling means are arranged on a common board including functionalities for compressing/decompressing voice information and/or for multiplexing/demultiplexing information in channels in a manner which will be more fully explained later on.

In an advantageous embodiment the network switching point or the switching node comprises means for particularly enabling the maintenance of a full-rate communication channel as discussed above, which provides for removing/adding idle information or filler bits from/to the common channel signalling channel. Further yet the full-rate communication channel between the data access means and the signalling information handling means comprises a full-rate 64 kbps ISDN D-channel. Still further the network switching node may comprise means for switching compressed voice in a non-decompressed format. Particularly compressed voice, data and signalling information is transferred to/from other switching nodes over a full-rate channel, for example a leased line comprising a number of 64 kbps channels, each single 64 kbps channel comprising one 8 bits time slot.

The method for transferring information between at least a first switching node and a second switching node advantageously comprises the steps of sending voice information between said first and second network nodes combined in one e.g. 64 kbps channel with data and signalling information. If compressed voice information is received, arranging the compressed information subrate channels each in a separate time slot, switching said subrate channels in separate time slots and combining said separate subrate channels with other separate subrate channels comprising compressed voice and/or data and/or signalling information and sending the information of one or more kinds in at least one common time slot to the second switching node.

The German patent application "Verfahren und Vorrichtung zum Multiplexen von Sprache und Daten", which was filed on December 29, 1995 by the same applicant and which has the application number 19549126.2-31 discusses dynamic allocation of voice and data. This document is also incorporated herein by reference. According to this document subrate channels can be set up in a full-rate channel depending on demand in a number of different ways. This means that if e.g. more capacity is needed for voice, more voice channels are set up, and vice versa for data, including any way of prioritizing. Only the signalling channel is not handled in said manner, but through the implementation of the concept of the present invention, the spare capacity on the signalling channel can be used for information.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be further described in a non- limiting way under reference to the accompanying drawings m which:

FIG 1 schematically illustrates a switching node handling data and signalling information,

FIG 2 schematically illustrates a switching node handling data, signalling information and compressed voice,

FIG 3 illustrates two switching arrangements between which signalling information and data information is transferred, and

FIG 4 illustrates a first and a second switching arrangement according to a second embodiment between which switching arrangements voice, data and signalling information is transferred. DETAILED DESCRIPTION OF THE INVENTION

Fig 1 schematically illustrates a network switching node 10 which for example may be a standard 64 kbps switching node. The node comprises data access means 11 which in this particular embodiment is a packet/frame relay switching arrangement, here particularly also referred to as packet frame alignment means (PFA) , and signalling handling means 12, in this particular case an ISDN D- channel handler. The packet/frame relay switch 11 receives via the connection line 13 data from a number of data interfaces such as for example V.24, Ethernet, Token Ring etc. In principle, in an advantageous embodiment, the packet switch 11 accepts data from substantially any data interface. The packet/frame relay switch 11 also receives a 64 kbps D-channel from the D-channel handler 12. In an alternative embodiment, not further illustrated herein, the D- channel can also be transported as a 16 kbps channel (for example) but in order to avoid delays the transmission rate of 64 kbps is advantageously used. In the packet/frame relay switch 11 additional access means, particularly transparent access means (not shown) are provided for receiving the 64 kbit D-channel. The transparent access means (particularly a transparent packet assembler disassembler accepting a HDLC (High Level Data Link) protocol for adaptation provides a terminal access function to facilitate the transparent communication of bit and byte-synchronous type protocols such as HDLC/SDLC and BSC, i.e. transparent transport of such protocols is provided for through the network.

All data that is received in the packet/frame relay switch 11 is packetized and all the data interfaces compete for the available bandwidth on the trunk to the next data access means of particularly the next packet/frame relay switch in another network switching node (not shown in the figure) . The data access means or particularly the packet/frame relay switch 11 detects if the D- channel 14 contains idle information, i.e. if it contains for example filler bits without any useful signalling information. If the connection comprising the D-channel comprises such idle information or filler bits, such filler bits are removed and replaced by data from the data interfaces 13. The useful signalling information on the D-channel 14 is sent as packets together with the packets generated comprising the information from other data interfaces on a connection line 15 which for example may be an X.25 or a frame relay link to a packet/frame relay switch in another switching node (not shown) with which it communicates. The information thus comprising signalling information and data information is advantageously sent in a full 64 kbit channel to the next switching node. In a cooperating packet/frame relay switch in said other switching node, this packet/frame relay switch in turn maintains a full 64 kbit connection to the corresponding D- channel handler in said latter switching node through generating idle information replacing the data information which is separated from the signalling information in the packet switching means and deliver it to the relevant address (address information is provided in a manner known per se and it is therefor not further discussed herein) .

When data information and signalling information is sent out on the line 15, signalling information is given priority. Packet/frame relay switches as such are well known in the art and e.g. comprise central processing means for measuring and evaluating the amount etc. of data that is transmitted.

Advantageously, data as well as signalling information can be sent in a subrate information channel, or the subrate channel can be used for data as well. Furthermore, the switching node 10 of course operates in duplex which is illustrated through the dashed lines illustrating connection links 15', 14', 13'. However, m an advantageous embodiment, the switching node also handles voice, particularly compressed voice.

This is m a schematical way illustrated m Fig 2. The data access means 21 are, similar to the embodiment discussed m Fig 1, arranged inside the switching matrix of for example a private branch exchange, PBX or PABX, for communication with other private branch exchanges using compressed voice channels and data channels and comprising a switch control means for setting up at least one fullrate channel leaving said private branch exchange on a first telecommunication line, which fullrate channel is arranged for connection to said other private branch exchange. The transmission format of the first telecommunication line is divided into frames containing a number of time slots and the fullrate channel occupies a certain time slot, and at least one channel handling device is provided comprising at least one channel input for receiving signals to be output m said fullrate channel, at least one voice channel means connected to a respective channel input and being arranged to compress signals appearing on this respective channel input to signals intended for at least one first subrate traffic channel or to pass at least part of each signal appearing on this channel input unaffected through the voice channel means to said first subrate traffic channel. A subrate traffic channel can be a subrate voice channel or a subrate data channel. A first multiplexer is connected to each voice channel means and arranged to multiplex signals incoming to the multiplexer to outgoing signals m at least two subrate channels provided m the first fullrate channel. Switch control means can advantageously be arranged to dynamically allocate the subrate traffic channels m the fullrate channel to compressed voice and data m dependence of demand.

The data access means 21, also here for example m the form a packet/frame relay switch 21, are arranged within the switching node 20 and receives as described under reference to Fig 1 data via a number of data interfaces over the connection lines 23. A full 64 kbps D-channel is via the connection line 24 connected to the packet/frame relay switch 21 in order to minimize the transmission delay. (As discussed above under reference to Fig 1 it could also have been a 16 kbps subrate connection, but in this case a transmission delay has to be taken into account.) The PFA 21 thus provides for a reduction in the bitrate.

The switching arrangement or the switching node 20 is in Fig 2 illustrated as if it would only operate in simplex although it of course also, like Fig 1, operates in duplex; this is so for reasons of clarity. Via a number of extensions, trunks, a compressing arrangement 27 receives voice over the connection lines 26. The voice information undergoes in the compressing arrangement 27 a 4:1 or a 8:1 or a 2:1 compression. The compressed voice is via the connection line 29 sent to the signal multiplexing means 30. The packet/frame relay switch 21 receives, as discussed above under reference to Fig 1, data information via the connection lines 23 and signalling information from the D-channel handler 22 via the connection line 24. Idle information is removed and the spare bandwidth on the D-channel is used for data traffic. As in the foregoing case signalling information is given priority. On a 64 kbit transmission line 28 with 16 (or 8) kbit the information comprising the data and the signalling information is sent to the multiplexing arrangement 30 in which voice, data information and signalling information is multiplexed, sent out on a leased line 31

(for example) e.g. in the form of a single 64 kbit channel comprising one time slot to the next switching arrangement or switching node (not shown) .

In Fig. 2 is illustrated how non-compressed voice is received and compressed in the switching node. However, the node may also receive already compressed voice in which case the voice goes directly to the multiplexing arrangement 30. This as well as the functioning in general will now be more thoroughly explained under reference to Figs 3 and 4 respectively.

Fig 3 illustrates two switching arrangements 100, 200. For reasons of clarity is only transmission in one direction illustrated but it should be obvious to everyone who is skilled in the art that the arrangements operate in duplex. The first switching arrangement 100 comprises data access means 101, for example a packet/frame relay switch PFA which receives data information Dl, D2, D3, D4 over connection lines 105 from a number of data interfaces as discussed under reference to Figs 1 and 2. The information may for example comprise data from computers, from automatic teller machines etc. The data access means 101 furthermore receives signalling information which may comprise pure signalling information or signalling information and idle information (or just idle information) e.g. in the form of so called filler bits over a connection line 106 which advantageously comprises a full 64 kbit channel.

The signalling means 102, in a particular embodiment the D-channel handler of ISDN, receives information from the system software SW 1, i.e. the software of the exchange, for example a PBX (PABX) as discussed above. In the D-channel handler 102 the information is processed in a protocol, for example the ISDN LAPD protocol (link access protocol for the D-channel) in a manner known per se. The 64 kbit channel on the connection line 106 from the D-channel handler 102 to the packet/frame relay switch 101 may comprise idle information if for example the full bandwidth of the channel is not used for signalling information e.g. in the case of low bandwidth applications. In the packet/frame relay switch 101 filler information is detected and replaced by data from the data interfaces .

In the packet/frame relay switch 101 in which the received data and the signalling information from the D-channel handler 102 is packetized, priority is given to the signalling information. Data D1-D4 and the signalling information D-ch is sent over for example an X.25 or frame relay link 107 via a board 104 (VCU board) comprising at least the D-channel handler via a line to an interface board 103 which for example comprises a TLU trunk (trunk line unit) which is an interface board or a standard board, in this case for transferring information between exchanges. Here the interface board 103 and the VCU-board VCU 1 comprise separate boards so that the VCU outputs can be dynamically allocated to e.g. a leased line or a public network etc. In one embodiment there is e.g. a so called nailed connection through the switch for the interface board. Other alternatives are however also possible. The VCU-board VCU 1 comprises the D-channel handler 102.

Over a full 64 kbps channel the data information D1-D4 and the D- channel signalling information D-ch is sent in one time slot TS to the next switching arrangement 200 as discussed above. In an advantageous embodiment bandwidth sharing (e.g. with dynamic allocation) is used. This is further discussed in "Verfahren und Vorrichtung zum multiplexen von Sprache und Daten" as referred to above. In brief, the whole time slot is reserved for data in the embodiment shown in the Fig. 3. The one fourth of each of the data D1-D4 is sent in each subrate channel, at the same time. This is merely schematically illustrated in Fig. 3. In one embodiment packet switching is applied which as such is supposed to be known to the skilled man. Then three 16 kbit subrate channels are used for the data Dl, D2 and D3 respectively whereas the last two bits corresponding to a 16 kbit subrate channel comprises the D-channel information plus the data D4, if the D-channel from the D-channel handler did comprise filler bits which then were replaced by, at least, D4. However, signalling information is always prioritized.

The second switching arrangement 200 in a similar manner comprises an interface board, particularly a TLU board 203 which via a line connects to a VCU board 204 which comprises the D-channel handler 202. Via the connection link 207 the data information and the signalling information is sent to the packet/frame relay switch 201. The packet switch 201 extracts the data information Dl, D2, D3 and recognizes the data information D4 which is marked in any convenient manner and separates the data from the signalling information D-ch. The data information is either output to destination computers etc. or sent on to a further switching arrangement, this merely being schematically illustrated through the connection links 205. In the PFA 201 means are further provided for adding idle information to the D-channel in order to maintain a full 64 kbit D-channel to the D-channel handler 202 i.e. filler bits are added so that a full 8-bits time slot is created. The signalling information is processed in a manner known per se in the D-channel handler 202 by the LAPD-protocol (ITU-T standard ETS 300 125) and "pure" signalling information is output to the system software SW 2 of the second switching arrangement, e.g. a second private branch exchange .

As already discussed under reference to Fig 2, in an advantageous embodiment of the invention, the switching arrangements also comprises means for switching voice or particularly means for switching compressed voice. In this context is also referred to the copending patent applications "Private branch exchange, telecommunication system and methods of transmitting signals in subrate channels" by the same applicant. In Fig 4 a switching arrangement 300 is shown which may be comprised m for example a private branch exchange. Also m Fig 4 is merely unidirectional transmission illustrated although the arrangements of course operate m duplex. To the switching arrangement 300 data D5, D6 is via the connection link 305 input over data interfaces. Data access means or particularly PFA 301 operate m the same manner as described above under reference to the previous figures and it also receives signalling information from the D-channel handler 302 over advantageously a full 64 kbps channel on connection line 306. The D-channel handler 302 m turn receives and processes information from the system software SW 3. In packet/frame relay switch 301 idle information is replaced by data information whereupon the data information and the signalling information are packetized. Output from the packet/frame relay switch 301 are m this case two 16 kbps subrate channels m one of which the D5 data information is carried m one time slot and m the other time slot the D6 data information and the signalling information is contained. These channels are input to a time slot assignment arrangement with a signal arranging means comprising a multiplexer 315.

However, the switching arrangement 300 also receives non-compressed voice VI from a telephone 311. The voice information VI comprises 8 bits and is via the connection line 312 sent to a compressing arrangement 313 m which a compressing operation is carried out. Thereafter VI is via connection line 314 sent to multiplexer 315 m one 16 kbps subrate channel.

For the compression a compressing algorithm is used such as e.g. the LD-CELP (standardized m ITU-T Rec. G.728) coding algorithm for compression to 16 kbps (4:1 compression). The compression algorithm is m a common ROM of the board (VCU) and it is loaded into e.g. 4 or 8 digital signal processors (DSP) of the board. The compression capacity can be increased through adding further signal processors. This is however not part of the present invention.

Still further the switching arrangement 300 receives compressed voice over connection 308 which transports voice in one time slot with four 16 kbps subrate channels. The information is demultiplexed in the demultiplexing arrangement 309 into four time slots, each comprising one 16 kbps subrate channel, i.e. time slots in which (in this example) only two bits are used for information carrying purposes. Three separate subrate channels in this case comprise voice information (calls) for which the switching arrangement 300 forms a terminating switching arrangement. They are therefore decompressed and output to their respective destinations. The decompressing and output is for reasons of clarity not illustrated in the figure. However, one of the 16 kbps separate subrate channels, carrying voice corresponding to call V2, is to be sent on to switching arrangement 400, i.e. the switching arrangement 300 forms a transit switching arrangement for said call. Therefore one 16 kbps subrate channel comprising voice information V2 is sent in one separate time slot (in which only two bits are used for carrying the information) via the connection line 310 to the multiplexer 315. The multiplexer 315 thus receives voice VI from the compressing arrangement, voice V2 from the demultiplexer 309 and data D5 and D6 and the D-channel information from the packet/frame relay switch 301. The subrate channels are combined in a multiplexer 315 and via connection line 316 sent to an interface board 303 in a manner similar to that described under reference to Fig 3, e.g. a TLU board and output as a full 64 kbps channel comprising one time slot in which two bits are used for voice VI, two bits for voice V2, two bits for data D5 and two bits for the D-channel plus the data D6 over the connection line 317 to an interface board 403, e.g. a TLU-board, in the switching arrangement 400. However, most advantageously is also here bandwidth sharing applied. In this case is then 32 kbits used for data (D4 and D5) and signalling information D-ch. On each 16 kbit channel is then e.g. half of D5 sent whereas the other half of D5 is sent on the other 16 kbits channel. It is similar for D6 etc. This is schematically illustrated through the dashed line m the time slot transmitted to switching arrangement 400.

The multiplexing arrangement is responsible for the position (m time) and all the information passes via the multiplexer. Signalling information has priority over data and data info may e.g. be prioritized m relation to voice.

Over connection 416 line the time slot comprising the information VI, V2, D5, D6 and D-ch is sent to the demultiplexer 409 m which a demultiplexing operation is carried out to arrange VI, V2, D5 and D6 + D-ch m four separate time slots (or at least one each for VI and V2 respectively) m each of which only (for example) two bits are used for carrying information. In a conventional manner addressing information is contained and the voice information, data information and signalling information is sent on to the appropriate arrangements for handling that particular information. For voice information V2 the switching arrangement 400 forms a terminating switching arrangement and one 16 kbps subrate channel m which two bits are used for carrying the voice information V2 is thus sent to decompressing arrangement 413 from which 8 bits containing V2 are output to telephone 411. The voice information VI contained m a 16 kbps subrate channel arranged m one separate time slot m which only two bits are used for carrying the information VI is via connection line 410 sent to the multiplexer 415. In the multiplexer 415 is according to an advantageous embodiment the voice VI is e.g. combined with other voice information e.g. received via a compressing arrangement (not shown m the figure) and output on connection line 417. This is not further explained since it functions in the same manner as the information output from switching arrangement 300. The data information D5 and D6 as well as the signalling information D-ch is over connection link 407 transported m two time slots to the packet/frame relay switch 401. The D6 data information is marked m any appropriate way and detected and data information D5, D6 is separated from the signalling information D-ch. In this case data information D5 and D6 is output to computers m a manner known per se. To the D-channel signalling information (D-ch) filler bits are added so that a full 64 kbps channel connection 406 to the D- channel handler 402 is maintained. In a similar manner as described under reference to Fig 3 the LAPD protocol of the D-channel handler 402 processes the information and pure signalling information is output to the software SW 4 of the exchange, e.g. a private exchange.

In an advantageous embodiment the compressing arrangement 313, the demultiplexing arrangement 315 and the D-channel handler 302 of switching arrangement 300 are arranged on a common board, e.g. a so called VCU board, Voice Compression Unit; m this particular case compressing functionality is included, this is however not always the case, c.f. e.g. Fig. 3, the denotation is however used m spite of that. The multiplexer 309 of the switching arrangement 300 is arranged on another (VCU) board. Moreover, the demultiplexer 409, the decompressing arrangement 413 and the D-channel handler 402 of the second switching arrangement 400 are arranged on a common (VCU) board whereas the multiplexer 415 is arranged on another board. In general there can be said to be one board or VCU board per input and output respectively. Each such board may m a particular embodiment handle one 64 kbit channel. However, m an alternative embodiment the DEMUX 309 could be on the same board as the D- channel handler 302, MUX 315 and compressing means 313. Advantageously one D-channel handler handles at least 32 channels, e.g. the tree other channels available on the same board and additional channels from other boards. Advantageously a board, such as e.g. the boards denoted VCU, are connected via the switch to the interface boards, here 303; 403. It may also handle additional channels used for overflow conditions. The D-channel can be transported m any channel.

The figure merely illustrates one time slot being transported between the switching arrangement 300 and the switching arrangement 400. However, m a PCM-multiplexed system there can be 32 time slots between the VCU boards as discussed above. For example, if one time slot is used as described under reference to Fig 4, 31 time slots could be used for carrying e.g. compressed voice if there are the corresponding number of VCU boards m the respective switching arrangements. Alternatively more time slots can be used for the combination of voice and data and signalling information or data and signalling information etc. m any combination. Also m any other respect the invention is not limited to the embodiments as illustrated m the figures, for example in Fig 4 might as well two 8 bits voice information calls be compressed m the compressing arrangement and e.g. no compressed voice, or alternatively the switching arrangement does not form an originating arrangement for any connections. Still further there might be more or less data etc. but how this works should be clear to every man skilled m the art when contemplating the embodiments as described under reference to for example Fig 4. Moreover is not necessarily a 1:4 compression used but alternatively might also a 1:8 compression or 1:2 compression etc. be used.

Still further, even if the embodiments are merely described referring to the ISDN D-channel, the invention of course is applicable on every other system using a common channel signalling channel .

It is an advantage of the present invention that bandwidth, that may be leased, can be efficiently used. Still another advantage is that signalling information can be transported faster than m hitherto known systems and that, m advantageous embodiments, additional bandwidth can be allocated according to the needs. It is also an advantage that there is only one transmission resource to be supervised as compared to known systems.

The invention can also m many other aspects be varied m a number of ways without departing from the scope of the claims.

Claims

1. A switching arrangement (10; 20; 100;200; 300; 400) for switching information at least in the form of data and signalling information, the signalling information at least partly being transported on a common channel signalling channel connection line (14;24;106;206;306;406) , c h a r a c t e r i z e d i n , that said switching arrangement (10;20; 100;200; 300; 400) comprises signalling handling means (12; 22; 102; 202; 302; 402) for handling signalling information on said common channel signalling channel connection line (14; 24; 106; 206; 306; 406) , and data access means (11;21;101;201;301;401) handling data to/from a number of data interfaces, said data access means further comprising means, e.g. additional access means, for handling signalling information on the common channel signalling channel, and means for replacing idle information or filler information on the common channel signalling channel by data information, a data resource being used for both data and signalling information.

2. A switching arrangement according to claim 1, c h a r a c t e r i z e d i n , that said data access means (11;21; 101; 201; 301; 401) comprises packet switching means.

3. A switching arrangement according to claim 2, c h a r a c t e r i z e d i n , that data information and signalling information is switched via said packet switching means (11; 21; 101; 201 ; 301; 401 ) on a data relaying link.

4. A switching arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that spare bandwidth, i.e. the bandwidth not used for valid or useful signalling information, on the common channel signalling channel, is used for data information.

5. A switching arrangement according to anyone of the preceding claims , c h a r a c t e r i z e d i n , that the data access means and the signalling information handling means communicate (exchange information) via a full-rate common channel signalling channel connection line (14,14';24;106;206;306;406).

6. A switching arrangement according to claim 5, c h a r a c t e r i z e d i n , that the data access means (201; 01) comprising said means for replacing idle information or filler bits by data information also are capable of generating idle information, e.g. filler bits when transferring signalling information to the signalling handling means (202; 402) maintaining a full-rate connection to said signalling handling means (202; 402) .

7. A switching arrangement according to claim 6, c h a r a c t e r i z e d i n , that the common channel signalling channel is the ISDN D-channel .

8. A switching arrangement according to claim 7, c h a r a c t e r i z e d i n , that the D-channel is transported over a connection line (14,14' ; 24; 106; 206; 306; 406) as a 64 kbps channel, 64 kbps being the full-rate D-channel transmission rate.

9. A switching arrangement according to claim 7, c h a r a c t e r i z e d i n , that if the D-channel comprises idle information e.g. m the form of filler bits, these are removed m the data accessing means and replaced by data information and m that data information is removed and filler information, e.g. filler bits, are added if signalling information is to be transferred from/to the signalling handling means respectively.

10. A switching arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that at least data information and signalling information is switched and sent e.g. to another switching arrangement via data connection lines (15, 15 '; 31; 108; 317) , e.g. comprising full-rate or subrate channels.

11. Arrangement according to claim 10, c h a r a c t e r i z e d i n , that the data link connection comprises an X.25 protocol link cr a frame relay link.

12. Arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that signalling information has a higher priority than data information.

13. Switching arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that the data accessing means (11; 21 ; 101; 301) receives information from data interfaces such as e.g. V.24, Ethernet, Token Ring.

14. Switching arrangement (20; 300; 400) according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that it also provides for switching of voice.

15. Switching arrangement according to claim 14, c h a r a c t e r i z e d i n , that it comprises signalling arranging means (30; 309, 315; 409, 415) and m that compressed voice can be switched without being decompressed, i.e. m a compressed format.

16. Switching arrangement according to claim 15, c h a r a c t e r i z e d i n , that said signal arranging means at least comprises multiplexing means (30; 315; 415) for multiplexing subrate channels transported m separate time slots m each of which only some of the bits are used for carrying information.

17. Switching arrangement according to claim 16, c h a r a c t e r i z e d i n , that combined subrate channels are output on a full-rate transmission line or subrate channels transported m a common time slot.

18. Arrangement according to claim 15 or 16, c h a r a c t e r i z e d i n , that m said multiplexing means of said signal arranging means, compressed speech is combined with data and signalling information.

19. Switching arrangement according to anyone of claims 14-18, c h a r a c t e r i z e d i n , that it further comprises compressing/decompressing means (27;313;413) for handling incoming/outgoing voice calls for which the switching arrangement forms an originating/terminating arrangement .

20. Switching arrangement according to anyone of claims 14-19, c h a r a c t e r i z e d i n , that said signal arranging means further comprises demultiplexing means (309; 409) for dividing a number of subrate channels transported in a common time slot containing said compressed voice into a number of separate time slots for switching purposes and in that switched subrate channels in separate time slots are multiplexed or combined with other subrate channels containing compressed voice and/or signalling information and/or data in said multiplexing means (30; 315; 415) before output.

21. A switching arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that a connection line (15, 15 '; 108; 317; 417) connecting the switching arrangement with another switching arrangement comprises a leased line such as e.g. a single 64 kbps line.

22. A switching arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that the data access means (11; 21; 101; 201; 301; 401) are arranged in the switching matrix of a private branch exchange (PBX) .

23. Switching arrangement according to anyone of the preceding claims, c h a r a c t e r i z e d i n , that the signalling information handling means are arranged on a board including functionalities for compressing/ decompressing of voice information and/or for combining/dividing information m channels .

24. Network switching node (10; 20; 100; 200; 300; 400) m a communications network comprising a private branch exchange with a switching matrix and data access means (11;21; 101; 201; 301; 401) for data access and signalling handling means (12; 22; 102; 202; 302; 402) receiving/transmitting signalling information, c h a r a c t e r i z e d i n , that the data access means (11;21; 101;201; 301; 401) are arranged within the switching matrix of the private branch exchange and m that signalling information to/from the signalling handling means (12;22; 102;202; 302; 402) is transferred using a subrate information channel via the data access means (11; 21; 101; 201; 301; 401) which comprises means enabling the access and handling of signalling information and m that spare capacity on the signalling channel is used for data information.

25. Network switching node according to claim 24, c h a r a c t e r i z e d i n , that said means providing the access of signalling information further enables the maintenance of a full-rate common channel signalling channel between the data access means and the signalling handling means and m that said means provides for removal/adding of idle information or filler bits from/to the common channel signalling channel.

26. Network switching node according to claim 25, c h a r a c t e r i z e d i n , that the full-rate communication channel between the data access means and the signalling information handling means comprises a full-rate 64 kbps ISDN D-channel.

27. Network swithing node according to anyone of claims 25-26, c h a r a c t e r i z e d i n , that it further comprises means (30; 309, 315; 409, 415) for switching compressed voice m a non-decompressed format and m that compressed voice, data and signalling information is transferred to/from other switching nodes over a full-rate channel, for example a leased line comprising a single 64 kbps channel.

28. Communications network comprising at least a first and a second switching node between which data information and signalling information is transferred, c h a r a c t e r i z e d i n , that each switching node comprises a switching matrix m which is arranged data access means for handling data and signalling information and m that further each switching node comprises signalling handling means, the data access means and the signalling handling means within each switching node communicating over a common channel signalling channel, and m that m each data access means, means are provided for replacing non-useful signalling information e.g. filler bits by data information so that the bandwidth of said channel that is not used for valid signalling information, is used for data information, and m that first and second switching nodes communicate via connection lines on which at least data and signalling information is transferred m channels.

29. Communications network according to claim 28, c h a r a c t e r i z e d i n , that at least some of the switching nodes comprises means for switching compressed voice without decompressing said voice and m that voice, data and signalling information is transferred between the nodes in a common time slot over a leased line.

30. Method for transferring at least data information and signalling information between at least a first network node and a second network node in a communications network, said method comprising the steps of: receiving data information and signalling information from signalling handling means arranged in said first switching means in data access means arranged in the switching matrix of the first node, examining in said data access means if received signalling information from the signalling handling means over a signalling channel contains idle information or filler information, - replacing idle information through data information, sending the data information and the valid signalling information to the second network node.

31. Method according to claim 30 further comprising the steps of; - receiving packetized signalling information and data information from the second network node in the data access means of the first network node, separating data information from signalling information, generating idle or filler information if needed to use all the capacity of the common channel signalling channel, sending useful signalling information and/or idle information to the signalling handling means in the first network node.

32 . Method according to claim 30 or 31 , c h a r a c t e r i z e d i n , that it further comprises the step of: giving signalling information priority over data information.

33. Method according to anyone of claims 30-32, c h a r a c t e r i z e d i n , that it further comprises the steps of: receiving and arranging compressed voice information in subrate channels in separate time slots, one for each subrate channel, switching said subrate channels, combining said separate subrate channels with other subrate channels comprising voice and/or data and/or signalling information, - sending voice and/or data and/or signalling information from one network node to another over e.g. a full-rate channel.