CA2338293A1 - Method for switching data received via a packet-oriented data transmission link - Google Patents
Method for switching data received via a packet-oriented data transmission link Download PDFInfo
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- CA2338293A1 CA2338293A1 CA002338293A CA2338293A CA2338293A1 CA 2338293 A1 CA2338293 A1 CA 2338293A1 CA 002338293 A CA002338293 A CA 002338293A CA 2338293 A CA2338293 A CA 2338293A CA 2338293 A1 CA2338293 A1 CA 2338293A1
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- timeslot
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- 230000005540 biological transmission Effects 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims description 22
- 238000006243 chemical reaction Methods 0.000 claims abstract description 34
- 239000000945 filler Substances 0.000 claims description 23
- 230000011664 signaling Effects 0.000 claims description 16
- 230000006978 adaptation Effects 0.000 claims description 6
- 238000012546 transfer Methods 0.000 claims description 4
- 230000000737 periodic effect Effects 0.000 claims 1
- 239000011159 matrix material Substances 0.000 abstract 1
- 238000004891 communication Methods 0.000 description 40
- 230000002457 bidirectional effect Effects 0.000 description 7
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 230000006837 decompression Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
- H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
- H04Q11/0478—Provisions for broadband connections
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
- H04J2203/0003—Switching fabrics, e.g. transport network, control network
- H04J2203/0005—Switching elements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5638—Services, e.g. multimedia, GOS, QOS
- H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
- H04L2012/5652—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
- H04L2012/5653—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly using the ATM adaptation layer [AAL]
- H04L2012/5656—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly using the ATM adaptation layer [AAL] using the AAL2
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5672—Multiplexing, e.g. coding, scrambling
- H04L2012/5675—Timeslot assignment, e.g. TDMA
Abstract
Data packets (ATM-Z1, ATM-Z2) partitioned into substructure elements (SE) ar e set up for data transmission via the packet oriented data transmission path. Channels with a time slot oriented format (TDM) are assigned to the data received via the packet oriented data transmission path by a conversion unit (UE). The converted data is then switched via a time slot oriented switching matrix module (KN).
Description
METHOD FOR SWITCHING DATA RECEIVED VIA A PACKET-ORIENTED DATA TRANSMISSION LINK
The significance of transmission and switching techniques for high data transmission rates (above 100 Mbit/s) is increasing due to the increasing need for a transmission of video information in modern communications technology such as, for example, still and moving images in picture telephony applications or the presentation of high-resolution graphics at modern data processing systems. A known dat transmission method for high transmission bit rates is what is referred to as the asynchronous transfer mode (ATM). A data transmission on the basis of the asynchronous transfer mode currently enables a variable transmission bit rate of up to 622 MbitJs.
In the transmission technique known as asynchronous transfer mode (ATM), data packets having a fixed length, what are referred to as ATM cells, are used for the data transport. An ATM cell is composed of a cell header that is five bytes long and contains the switching data relevant for the transport of an ATM cell and of a 48 byte long payload field. Only data allocated to one logical connection -frequently referred to as virtual channel VC or ATM channel in the literature -are thereby transmitted in the payload field of an ATM cell.
US Published Application US-A-5784371 discloses a communication 2 0 network formed of a plurality of communication systems that are connected to one another via an ATM network. The communication systems respectively comprise a timeslot-oriented switching network module for a connection of timeslot-oriented terminal devices to the respective communication system, whereby a bidirectional switching of data to be exchanged bet [...] device and the packet-oriented ATM
2 5 network ensues with the timeslot-oriented switching network modules.
The German Patent Application bearing the serial number 198 187 76.9 has already disclosed a method that enables a transmission of data belonging to different logical connections in the payload region of one or, respectively, several ATM cells. To this end, what are referred to as sub-structure elements having a 3 o variable payload field 0 through 64 bytes long is defined in the payload field of an ATM cell, said sub-structure elements being capable of being respectively allocated to a logical connection via an address field in the cell header of the sub-structure element. Due to the 8-bit long address field in the cell header of a sub-structure element, a maximum of 2g = 256 different logical connections can be addressed.
Additionally, at least one sub-structure element is reserved for a transmission of signalling information allocated to the logical connections.
The article by Mauger, R., et al., "ATM Adaptation Layer Switching" ISS, World Telecommunications Congress (International Switching Symposium), Ca, Toronto, Pinnacle group, pages 207-214, XP000720525, discloses an arrangement for a switching of data received via a timeslot-oriented data transmission link and a packet-oriented data transmission link. The arrangement thereby comprises both a timeslot-oriented switching network module as well as a packet-oriented switching network module. A switching of data received via the packet-oriented data transmission link and to be forwarded via a packet-oriented data transmission link as well thereby ensues with the packet-oriented switching network module.
An object of the present invention is to specify an alternative method with which a switching of data that are received via a packet-oriented data transmission link and are to be forwarded is enabled.
Proceeding from the features of the preamble of patent claim l, this object 2 0 is inventively achieved by the characterizing features thereof.
A critical advantage of the inventive method is then comprised'therein that a switching of data allocated to different logical connections and transmitted in one or, respectively, several data cells can ensue via a traditional timeslot-oriented switching network module. A development of a switching network module designed 2 5 for the present packet-oriented data format and a signalling adapted thereto are thus not necessary.
Advantageous developments of the invention are recited in the subclaims.
One advantage of developments of the invention defined in the subclaims is comprised, among other things, therein that the insertion of filler cells or, 3 o respectively, of filler data into a sub-structure element during the conversion of a packet-oriented data format into a timeslot-oriented data format makes a switching of 2a compressed data possible without preceding decompression. A quality loss in the switching of compressed data is thus avoided.
An exemplary embodiment of the invention is explained in greater detail below on the basis of the drawing.
Thereby shown are:
Figure 1 a structogram of the schematic illustration of the critical function units participating in the inventive method;
Figure 2 a structogram of the schematic illustration of the conversion of a packet-1 o oriented data format into a timeslot-oriented data format according to a first operating mode of a conversion unit;
Figure 3 a structogram of the schematic illustration of the conversion of the packet-oriented data format into the timeslot-oriented data format according to a second operating mode of the conversion unit.
Figure 1 shows a schematic illustration of a communication system PBX.
The communication system PBX comprises subscriber or, respectively, network line/trunk modules - a line/trunk module ABG is shown by way of example - for the connection of communication terminal devices or, respectively, for a connection to a communication network - for example, an ISDN-oriented communication network, an analog communication network, a radio communication network or an ATM-based communication network.
Further, the communication system PBX contains a timeslot-oriented switching network module KN comprising a plurality of bidirectional, time-division multiplex-oriented switching terminals KA, whereby the time-division multiplex-oriented switching terminals KA are fashioned as PCM terminals (pulse code modulation), also referred to as PCM highways, speech highways or SZM
terminals.
Given an internal data transmission of the communication system, a PCM highway generally comprises 32 payload channels that are fashioned as ISDN-oriented B-channels (integrated services digital network) with a respective transmission bit rate of 64 kbit/s.
A line unit AE and a conversion unit UE are arranged on the line/trunk module ABG. The communication system PBX is connected to an ATM-based communication network ATM-KN via a network interface NA of the line unit AE, said ATM-based communication network ATM-KN being composed of a plurality of communication systems connected to one another. A first and a second communication terminal device KE-A, KE-B are connected to the ATM-based communication network ATM KN. The line unit AE is connected to a bidirectional, 2 0 packet-oriented terminal SK of the conversion unit UE via a bidirectional, packet-oriented terminal SK. [sic) The conversion unit UE, further, is connected to a switching terminal KA
of the timeslot-oriented switching network module KN via a bidirectional, time division multiplex-oriented switching terminal KA. [sic) Via further switching 2 5 terminals KA (not shown), the timeslot-oriented switching network module KN is respectively connected to a bidirectional time-division multiplex-oriented terminal SK
of further subscriber or, respectively, line/trunk modules (not shown) arranged in the communication system PBX.
A bidirectional conversion between the packet-oriented data format of a 3 o connecting line PO-VL between the conversion unit UE and the line unit AE
and the timeslot-oriented data format of a connecting line ZO-VL between the conversion unit UE and the timeslot-oriented switching network module KN ensues with the conversion unit UE according to two different operating modes of said conversion unit UE that are described in greater detail below.
Further, a control unit STE comprising a plurality of control terminals Sl, S2 is arranged in the communication system PBX. The control unit STE is connected to a control input SE of the timeslot-oriented switching network module KN via a control terminal S2, and is connected to a control input SE of the line/trunk module ABG via a control terminal Sl. the control unit STE is connected to control inputs of further subscriber or, respectively, line/trunk modules arranged in the communication system PBX via further control terminals (not shown). A communication of signalling information between the control unit STE and the timeslot-oriented switching network module KN or, respectively, the line/trunk module ABG
thereby ensues according to the HDLC data format (high level data link control).
Figure 2 shows a schematic illustration of a conversion of the packet-oriented ATM data format according to the ATM adaption layer AAL type 2 into the timeslot-oriented data format according to the TDM method (time-division multiplex) in a first operating mode of the conversion unit UE. A data transmission in the framework of the packet-oriented ATM data format ensues via ATM cells ATM-Z1, ATM-Z2. An ATM cell ATM-Zl, ATM-Z2 is composed of a five byte long cell 2 0 header H containing the switching data relevant for the transport of an ATM cell ATM-ZI, ATM-Z2 and of a 48 byte long payload field.
In a data transmission in the framework of the packet-oriented ATM data format according to the ATM adaption layer AAL type 2, there is the possibility of subdividing the payload area of an ATM cell ATM-Z1, ATM-Z2 into sub-structure 2 5 elements SE. The adaptation of the ATM data format - also frequently referred to as "ATM layer" (layer 2) in the literature - to the switching layer (layer 3) according to the OSI reference model (open systems interconnection) thereby ensues with what is referred to as the ATM adaption layer AAL.
A sub-structure element SE according to the ATM adaption layer AAL
3 o type 2 is composed of a 3 byte long cell header and of a variable-length payload area I
(0 through 64 bytes). The cell header of a sub-structure element SE is subdivided into an 8 bit long channel identifier CID, a 6 bit long length indicator LI, a 5 bit long transmitter-receiver indication UUI (user-to-user indication) and a 5 bit long cell header checksum HEC (header error control).
As a result of the subdivision of an ATM connection with the assistance of 5 sub-structure elements SE into mutually independent data streams, as shown in the Figure with reference to the example of the ATM cells ATM-Z1, ATM-Z2, up to 28 -256 different logical connections can be addressed within an ATM connection of the basis of the 8 bit long channel identifier CID, all of these logical connections being addressed with the same ATM address - composed of a VPI value (virtual path identifier) and of a VCI value (virtual channel identifier). In addition, there is the possibility of defining a sub-structure element SE for a transmission of signalling information allocated to the logical connections. For a transmission of payload data allocated to the logical connections, one sub-structure element SE can be defined for every currently required logical connection, so that the transmission capacity can be exactly matched to the current need.
For example, four different sub-structure elements SE are shown in the Figure that are defined on the basis of different channel identifier CID in the cell header - referred to below as sub-structure element header 0, 1, 2, 3 - of the sub-structure elements SE. A payload field I of variable length (0 through 26 bytes) can be 2 o defined by the 6 bit long length indicator LI in the cell header, so that a data transmission with variable transmission bit rate can be realized for the different logical connections.
For a conversion of the packet-oriented data format according to the ATM
adaption layer AAL type 2 onto the timeslot-oriented data format according to the 2 5 TDM method, a TDM channel K0, ..., K3 of the timeslot-oriented data format according to the TDM method is allocated to each element SE of an ATM cell ATM-Z1, ATM-Z2 defined for a transmission of payload data. An allocation of a sub-structure element SE to a TDM channel K0, ..., K3 thereby ensues in a signalling phase preceding the payload transmission. 32 payload channels, which are configured 3 o as ISDN-oriented B-channels with a constant transmission bit rate of respectively 64 kbit/s, are generally available for a data transmission in the framework of the timeslot-oriented data format according to the TDM method.
In the framework of the conversion of the packet-oriented data format according to the ATM adaption layer AAL type 2 onto the timeslot-oriented data format according to the TDM method, an adaptation of the - potentially variable -transmission bit rate of the packet-oriented data format deriving due to the size and the arrival of sub-structure elements SE onto the constant transmission bit rate of 64 kbit/s of the timeslot-oriented data format must additionally ensue. This is achieved in the scope of the first operating mode of the conversion unit UE by an insertion of 1 o what are referred to as filler cells FZ of variable length into the continuous TDM data stream.
The sub-structure element SE received via the packet-oriented connecting line PO-VL and packed in ATM cells ATM-Z1, ATM-Z2 must be unpacked in the conversion unit UE. For the conversion of the - potentially variable -transmission bit rate deriving due to the size and the arrival of the sub-structure elements SE onto the constant transmission bit rate of 64 kbit/s of the timeslot-oriented data format, what are referred to as filler cells FZ are subsequently attached to the sub-structure elements SE containing the payload data. The length of a filler cell FZ is defined by what is referred to as a filler cell header FZH. the length of a filler cell FZ is thereby 2 o selected such that the overall transmission bit rate of a sub-structure element SE and of a filler cell FZ yields a whole multiple of 64 kbit/s. When the transmission bit rate of a sub-structure element SE is higher than 64 kbit/s - i.e. higher than the transmission bit rate of a TDM channel Kl, ..., K4 - the payload data communicated in a sub-structure element SE are divided onto a plurality of TDM channels K1, ..., 2 5 K4.
In conclusion, these data (sub-structure elements SE and filler cells FX
together) are allocated to a TDM channel K0, ... Kl of the timeslot-oriented connecting line ZO-VL declared in the signalling phase and are transmitted via this to the timeslot-oriented switching network module KN.
3 0 The signalling information communicated from the conversion unit UE to the control unit STE of the communication system PBX in the framework of the signalling phase are converted in the control unit STE into switching-oriented control data for the timeslot-oriented switching network module KN. A switching of the data (sub-structure elements SE and filler cells FZ together) received via the respective TDM channels K0, ..., K3 of the timeslot-oriented connecting line ZO-VL ensues in the timeslot-oriented switching network module KN on the basis of the switching-oriented control data, i.e. an allocation of a TDM channel of an input line of the timeslot-oriented switching network module KN onto a TDM channel of an output line of the timeslot-oriented switching network module KN.
When the payload data to be communicated are to be transmitted anew via the ATM-based communication network ATM-KN to a receiver, the data (sub-structure elements SE and filler cells FZ together) are transmitted from the timeslot-oriented switching network module KN to the conversion unit UE, wherein the filler cells FZ are removed from the TDM data stream, so that the data stream then only comprises sub-structure elements SE containing payload data. The sub-structure elements SE to be transmitted are packed in ATM cells ATM-Z1, ATM-Z2 in the conversion unit UE and are communicated via the ATM-based communication network ATM-KN to the addressed recipient. When the data are to be transmitted to, for example, an internal communication terminal device (not shown), then these are transmitted directly to a subscriber line module (not shown) via which the addressed 2 0 communication terminal device is connected to the communication system PBX.
Figure 3 shows a schematic illustration of a conversion of the packet-oriented ATM data format according to the ATM adaption layer AAL type 2 into the timeslot-oriented data format according to the TDM method (time division multiplex) in a second operating mode of the conversion unit UE.
2 5 In contrast to the first operating mode of the conversion unit UE, no separate filler cells FZ are inserted into the continuous TDM data stream in the second operating mode. An adaptation of the - potentially variable - transmission bit rate of the packet-oriented data format to the constant transmission bit rate of 64 kbit/s of the timeslot-oriented data format ensues by filling the sub-structure elements SE
with 3 0 filler data FD, so that the overall transmission bit rate of a sub-structure element SE
(payload data and filler data FD together) yields a whole multiple of 64 bits.
This, however, assumes that each TDM channel K0, ..., K3 additionally has an information about the length of the sub-structure elements SE that is transmitted and supplemented with filler data FD allocated to it such that a separation of the payload data to be transmitted from the filler data FD is enabled with the assistance of this information.
When, proceeding from the first communication terminal device KE-A, data are to be communicated to the second communication terminal device KE-B, the first communication terminal device KE-A sends the necessary signalling information to the communication system PBX in the framework of a signalling phase preceding the payload transmission, sending these information via a defined sub-structure element SE of a first ATM channel V-A, which is frequently abbreviated as VC
(virtual channel ) in the literature. The transmitted signalling information are unpacked in the conversion unit UE, converted into the HDLC data format and communicated to the control unit STE.
On the basis of the communicated signalling information, a TDM channel - for example, the TDM channel 17 - of the timeslot-oriented connecting line ZO-VL
is allocated to the sub-structure elements Se of the first ATM channel V-A
that are defined for the transmission of the payload data from the first communication terminal device KE-A to the communication system PBX. Further, the communicated signalling information are converted into switching-oriented control data for the 2 0 timeslot-oriented switching network module KN. The switching-oriented control data define which input TDM channel - for example, the TDM channel 17 of the timeslot-oriented connecting line ZO-VL - is connected to which output TDM channel of the timeslot-oriented switching network module KN - for example, the TDM channel of the timeslot-oriented connecting line ZO-VL.
2 5 Subsequently, the frist communication terminal device KE-A packs payload data to be transmitted into sub-structure elements SE that are in turn packed in ATM cells ATM-Zl, ATM-Z2 and subsequently communicated via the first ATM
channel V-A to the communication system PBX. The sub-structure elements SE are unpacked from the ATM cells ATM-Z1, ATM-Z2 in the conversion unit UE. In a 3 o next step, the transmission bit rate deriving due to the size and the arnval of the sub-structure elements SE is matched to the constant transmission bit rate of 64 kbit/s by inserting filler cells FZ according to the first operating mode of the conversion unit UE.
The data - composed of sub-structure elements SE and filler cells FZ - are subsequently forwarded via the TDM channel 17 of the timeslot-oriented connecting line ZO-VL to the timeslot-oriented switching network module KN. The data are switched onto the TDM channel 23 of the timeslot-oriented connecting line ZO-VL
by the timeslot-oriented switching network module KN and are sent back to the conversion unit UE. The filler cells FZ are removed from the continuous data stream in the conversion unit UE, so that the data stream is not composed only of sub-1 o structure elements SE containing payload data. These sub-structure elements SE are subsequently packed into ATM cells ATM-Z1, ATM-Z2 and transmitted to the second communication terminal device KE-B via a second ATM channel V-B.
The significance of transmission and switching techniques for high data transmission rates (above 100 Mbit/s) is increasing due to the increasing need for a transmission of video information in modern communications technology such as, for example, still and moving images in picture telephony applications or the presentation of high-resolution graphics at modern data processing systems. A known dat transmission method for high transmission bit rates is what is referred to as the asynchronous transfer mode (ATM). A data transmission on the basis of the asynchronous transfer mode currently enables a variable transmission bit rate of up to 622 MbitJs.
In the transmission technique known as asynchronous transfer mode (ATM), data packets having a fixed length, what are referred to as ATM cells, are used for the data transport. An ATM cell is composed of a cell header that is five bytes long and contains the switching data relevant for the transport of an ATM cell and of a 48 byte long payload field. Only data allocated to one logical connection -frequently referred to as virtual channel VC or ATM channel in the literature -are thereby transmitted in the payload field of an ATM cell.
US Published Application US-A-5784371 discloses a communication 2 0 network formed of a plurality of communication systems that are connected to one another via an ATM network. The communication systems respectively comprise a timeslot-oriented switching network module for a connection of timeslot-oriented terminal devices to the respective communication system, whereby a bidirectional switching of data to be exchanged bet [...] device and the packet-oriented ATM
2 5 network ensues with the timeslot-oriented switching network modules.
The German Patent Application bearing the serial number 198 187 76.9 has already disclosed a method that enables a transmission of data belonging to different logical connections in the payload region of one or, respectively, several ATM cells. To this end, what are referred to as sub-structure elements having a 3 o variable payload field 0 through 64 bytes long is defined in the payload field of an ATM cell, said sub-structure elements being capable of being respectively allocated to a logical connection via an address field in the cell header of the sub-structure element. Due to the 8-bit long address field in the cell header of a sub-structure element, a maximum of 2g = 256 different logical connections can be addressed.
Additionally, at least one sub-structure element is reserved for a transmission of signalling information allocated to the logical connections.
The article by Mauger, R., et al., "ATM Adaptation Layer Switching" ISS, World Telecommunications Congress (International Switching Symposium), Ca, Toronto, Pinnacle group, pages 207-214, XP000720525, discloses an arrangement for a switching of data received via a timeslot-oriented data transmission link and a packet-oriented data transmission link. The arrangement thereby comprises both a timeslot-oriented switching network module as well as a packet-oriented switching network module. A switching of data received via the packet-oriented data transmission link and to be forwarded via a packet-oriented data transmission link as well thereby ensues with the packet-oriented switching network module.
An object of the present invention is to specify an alternative method with which a switching of data that are received via a packet-oriented data transmission link and are to be forwarded is enabled.
Proceeding from the features of the preamble of patent claim l, this object 2 0 is inventively achieved by the characterizing features thereof.
A critical advantage of the inventive method is then comprised'therein that a switching of data allocated to different logical connections and transmitted in one or, respectively, several data cells can ensue via a traditional timeslot-oriented switching network module. A development of a switching network module designed 2 5 for the present packet-oriented data format and a signalling adapted thereto are thus not necessary.
Advantageous developments of the invention are recited in the subclaims.
One advantage of developments of the invention defined in the subclaims is comprised, among other things, therein that the insertion of filler cells or, 3 o respectively, of filler data into a sub-structure element during the conversion of a packet-oriented data format into a timeslot-oriented data format makes a switching of 2a compressed data possible without preceding decompression. A quality loss in the switching of compressed data is thus avoided.
An exemplary embodiment of the invention is explained in greater detail below on the basis of the drawing.
Thereby shown are:
Figure 1 a structogram of the schematic illustration of the critical function units participating in the inventive method;
Figure 2 a structogram of the schematic illustration of the conversion of a packet-1 o oriented data format into a timeslot-oriented data format according to a first operating mode of a conversion unit;
Figure 3 a structogram of the schematic illustration of the conversion of the packet-oriented data format into the timeslot-oriented data format according to a second operating mode of the conversion unit.
Figure 1 shows a schematic illustration of a communication system PBX.
The communication system PBX comprises subscriber or, respectively, network line/trunk modules - a line/trunk module ABG is shown by way of example - for the connection of communication terminal devices or, respectively, for a connection to a communication network - for example, an ISDN-oriented communication network, an analog communication network, a radio communication network or an ATM-based communication network.
Further, the communication system PBX contains a timeslot-oriented switching network module KN comprising a plurality of bidirectional, time-division multiplex-oriented switching terminals KA, whereby the time-division multiplex-oriented switching terminals KA are fashioned as PCM terminals (pulse code modulation), also referred to as PCM highways, speech highways or SZM
terminals.
Given an internal data transmission of the communication system, a PCM highway generally comprises 32 payload channels that are fashioned as ISDN-oriented B-channels (integrated services digital network) with a respective transmission bit rate of 64 kbit/s.
A line unit AE and a conversion unit UE are arranged on the line/trunk module ABG. The communication system PBX is connected to an ATM-based communication network ATM-KN via a network interface NA of the line unit AE, said ATM-based communication network ATM-KN being composed of a plurality of communication systems connected to one another. A first and a second communication terminal device KE-A, KE-B are connected to the ATM-based communication network ATM KN. The line unit AE is connected to a bidirectional, 2 0 packet-oriented terminal SK of the conversion unit UE via a bidirectional, packet-oriented terminal SK. [sic) The conversion unit UE, further, is connected to a switching terminal KA
of the timeslot-oriented switching network module KN via a bidirectional, time division multiplex-oriented switching terminal KA. [sic) Via further switching 2 5 terminals KA (not shown), the timeslot-oriented switching network module KN is respectively connected to a bidirectional time-division multiplex-oriented terminal SK
of further subscriber or, respectively, line/trunk modules (not shown) arranged in the communication system PBX.
A bidirectional conversion between the packet-oriented data format of a 3 o connecting line PO-VL between the conversion unit UE and the line unit AE
and the timeslot-oriented data format of a connecting line ZO-VL between the conversion unit UE and the timeslot-oriented switching network module KN ensues with the conversion unit UE according to two different operating modes of said conversion unit UE that are described in greater detail below.
Further, a control unit STE comprising a plurality of control terminals Sl, S2 is arranged in the communication system PBX. The control unit STE is connected to a control input SE of the timeslot-oriented switching network module KN via a control terminal S2, and is connected to a control input SE of the line/trunk module ABG via a control terminal Sl. the control unit STE is connected to control inputs of further subscriber or, respectively, line/trunk modules arranged in the communication system PBX via further control terminals (not shown). A communication of signalling information between the control unit STE and the timeslot-oriented switching network module KN or, respectively, the line/trunk module ABG
thereby ensues according to the HDLC data format (high level data link control).
Figure 2 shows a schematic illustration of a conversion of the packet-oriented ATM data format according to the ATM adaption layer AAL type 2 into the timeslot-oriented data format according to the TDM method (time-division multiplex) in a first operating mode of the conversion unit UE. A data transmission in the framework of the packet-oriented ATM data format ensues via ATM cells ATM-Z1, ATM-Z2. An ATM cell ATM-Zl, ATM-Z2 is composed of a five byte long cell 2 0 header H containing the switching data relevant for the transport of an ATM cell ATM-ZI, ATM-Z2 and of a 48 byte long payload field.
In a data transmission in the framework of the packet-oriented ATM data format according to the ATM adaption layer AAL type 2, there is the possibility of subdividing the payload area of an ATM cell ATM-Z1, ATM-Z2 into sub-structure 2 5 elements SE. The adaptation of the ATM data format - also frequently referred to as "ATM layer" (layer 2) in the literature - to the switching layer (layer 3) according to the OSI reference model (open systems interconnection) thereby ensues with what is referred to as the ATM adaption layer AAL.
A sub-structure element SE according to the ATM adaption layer AAL
3 o type 2 is composed of a 3 byte long cell header and of a variable-length payload area I
(0 through 64 bytes). The cell header of a sub-structure element SE is subdivided into an 8 bit long channel identifier CID, a 6 bit long length indicator LI, a 5 bit long transmitter-receiver indication UUI (user-to-user indication) and a 5 bit long cell header checksum HEC (header error control).
As a result of the subdivision of an ATM connection with the assistance of 5 sub-structure elements SE into mutually independent data streams, as shown in the Figure with reference to the example of the ATM cells ATM-Z1, ATM-Z2, up to 28 -256 different logical connections can be addressed within an ATM connection of the basis of the 8 bit long channel identifier CID, all of these logical connections being addressed with the same ATM address - composed of a VPI value (virtual path identifier) and of a VCI value (virtual channel identifier). In addition, there is the possibility of defining a sub-structure element SE for a transmission of signalling information allocated to the logical connections. For a transmission of payload data allocated to the logical connections, one sub-structure element SE can be defined for every currently required logical connection, so that the transmission capacity can be exactly matched to the current need.
For example, four different sub-structure elements SE are shown in the Figure that are defined on the basis of different channel identifier CID in the cell header - referred to below as sub-structure element header 0, 1, 2, 3 - of the sub-structure elements SE. A payload field I of variable length (0 through 26 bytes) can be 2 o defined by the 6 bit long length indicator LI in the cell header, so that a data transmission with variable transmission bit rate can be realized for the different logical connections.
For a conversion of the packet-oriented data format according to the ATM
adaption layer AAL type 2 onto the timeslot-oriented data format according to the 2 5 TDM method, a TDM channel K0, ..., K3 of the timeslot-oriented data format according to the TDM method is allocated to each element SE of an ATM cell ATM-Z1, ATM-Z2 defined for a transmission of payload data. An allocation of a sub-structure element SE to a TDM channel K0, ..., K3 thereby ensues in a signalling phase preceding the payload transmission. 32 payload channels, which are configured 3 o as ISDN-oriented B-channels with a constant transmission bit rate of respectively 64 kbit/s, are generally available for a data transmission in the framework of the timeslot-oriented data format according to the TDM method.
In the framework of the conversion of the packet-oriented data format according to the ATM adaption layer AAL type 2 onto the timeslot-oriented data format according to the TDM method, an adaptation of the - potentially variable -transmission bit rate of the packet-oriented data format deriving due to the size and the arrival of sub-structure elements SE onto the constant transmission bit rate of 64 kbit/s of the timeslot-oriented data format must additionally ensue. This is achieved in the scope of the first operating mode of the conversion unit UE by an insertion of 1 o what are referred to as filler cells FZ of variable length into the continuous TDM data stream.
The sub-structure element SE received via the packet-oriented connecting line PO-VL and packed in ATM cells ATM-Z1, ATM-Z2 must be unpacked in the conversion unit UE. For the conversion of the - potentially variable -transmission bit rate deriving due to the size and the arrival of the sub-structure elements SE onto the constant transmission bit rate of 64 kbit/s of the timeslot-oriented data format, what are referred to as filler cells FZ are subsequently attached to the sub-structure elements SE containing the payload data. The length of a filler cell FZ is defined by what is referred to as a filler cell header FZH. the length of a filler cell FZ is thereby 2 o selected such that the overall transmission bit rate of a sub-structure element SE and of a filler cell FZ yields a whole multiple of 64 kbit/s. When the transmission bit rate of a sub-structure element SE is higher than 64 kbit/s - i.e. higher than the transmission bit rate of a TDM channel Kl, ..., K4 - the payload data communicated in a sub-structure element SE are divided onto a plurality of TDM channels K1, ..., 2 5 K4.
In conclusion, these data (sub-structure elements SE and filler cells FX
together) are allocated to a TDM channel K0, ... Kl of the timeslot-oriented connecting line ZO-VL declared in the signalling phase and are transmitted via this to the timeslot-oriented switching network module KN.
3 0 The signalling information communicated from the conversion unit UE to the control unit STE of the communication system PBX in the framework of the signalling phase are converted in the control unit STE into switching-oriented control data for the timeslot-oriented switching network module KN. A switching of the data (sub-structure elements SE and filler cells FZ together) received via the respective TDM channels K0, ..., K3 of the timeslot-oriented connecting line ZO-VL ensues in the timeslot-oriented switching network module KN on the basis of the switching-oriented control data, i.e. an allocation of a TDM channel of an input line of the timeslot-oriented switching network module KN onto a TDM channel of an output line of the timeslot-oriented switching network module KN.
When the payload data to be communicated are to be transmitted anew via the ATM-based communication network ATM-KN to a receiver, the data (sub-structure elements SE and filler cells FZ together) are transmitted from the timeslot-oriented switching network module KN to the conversion unit UE, wherein the filler cells FZ are removed from the TDM data stream, so that the data stream then only comprises sub-structure elements SE containing payload data. The sub-structure elements SE to be transmitted are packed in ATM cells ATM-Z1, ATM-Z2 in the conversion unit UE and are communicated via the ATM-based communication network ATM-KN to the addressed recipient. When the data are to be transmitted to, for example, an internal communication terminal device (not shown), then these are transmitted directly to a subscriber line module (not shown) via which the addressed 2 0 communication terminal device is connected to the communication system PBX.
Figure 3 shows a schematic illustration of a conversion of the packet-oriented ATM data format according to the ATM adaption layer AAL type 2 into the timeslot-oriented data format according to the TDM method (time division multiplex) in a second operating mode of the conversion unit UE.
2 5 In contrast to the first operating mode of the conversion unit UE, no separate filler cells FZ are inserted into the continuous TDM data stream in the second operating mode. An adaptation of the - potentially variable - transmission bit rate of the packet-oriented data format to the constant transmission bit rate of 64 kbit/s of the timeslot-oriented data format ensues by filling the sub-structure elements SE
with 3 0 filler data FD, so that the overall transmission bit rate of a sub-structure element SE
(payload data and filler data FD together) yields a whole multiple of 64 bits.
This, however, assumes that each TDM channel K0, ..., K3 additionally has an information about the length of the sub-structure elements SE that is transmitted and supplemented with filler data FD allocated to it such that a separation of the payload data to be transmitted from the filler data FD is enabled with the assistance of this information.
When, proceeding from the first communication terminal device KE-A, data are to be communicated to the second communication terminal device KE-B, the first communication terminal device KE-A sends the necessary signalling information to the communication system PBX in the framework of a signalling phase preceding the payload transmission, sending these information via a defined sub-structure element SE of a first ATM channel V-A, which is frequently abbreviated as VC
(virtual channel ) in the literature. The transmitted signalling information are unpacked in the conversion unit UE, converted into the HDLC data format and communicated to the control unit STE.
On the basis of the communicated signalling information, a TDM channel - for example, the TDM channel 17 - of the timeslot-oriented connecting line ZO-VL
is allocated to the sub-structure elements Se of the first ATM channel V-A
that are defined for the transmission of the payload data from the first communication terminal device KE-A to the communication system PBX. Further, the communicated signalling information are converted into switching-oriented control data for the 2 0 timeslot-oriented switching network module KN. The switching-oriented control data define which input TDM channel - for example, the TDM channel 17 of the timeslot-oriented connecting line ZO-VL - is connected to which output TDM channel of the timeslot-oriented switching network module KN - for example, the TDM channel of the timeslot-oriented connecting line ZO-VL.
2 5 Subsequently, the frist communication terminal device KE-A packs payload data to be transmitted into sub-structure elements SE that are in turn packed in ATM cells ATM-Zl, ATM-Z2 and subsequently communicated via the first ATM
channel V-A to the communication system PBX. The sub-structure elements SE are unpacked from the ATM cells ATM-Z1, ATM-Z2 in the conversion unit UE. In a 3 o next step, the transmission bit rate deriving due to the size and the arnval of the sub-structure elements SE is matched to the constant transmission bit rate of 64 kbit/s by inserting filler cells FZ according to the first operating mode of the conversion unit UE.
The data - composed of sub-structure elements SE and filler cells FZ - are subsequently forwarded via the TDM channel 17 of the timeslot-oriented connecting line ZO-VL to the timeslot-oriented switching network module KN. The data are switched onto the TDM channel 23 of the timeslot-oriented connecting line ZO-VL
by the timeslot-oriented switching network module KN and are sent back to the conversion unit UE. The filler cells FZ are removed from the continuous data stream in the conversion unit UE, so that the data stream is not composed only of sub-1 o structure elements SE containing payload data. These sub-structure elements SE are subsequently packed into ATM cells ATM-Z1, ATM-Z2 and transmitted to the second communication terminal device KE-B via a second ATM channel V-B.
Claims (7)
1. Method for switching data that are received via a packet-oriented data transmission link and are to be forwarded, whereby data packets (ATM-Z1, ATM-Z2) subdivided into sub-structure elements (SE) are established for a data transmission via the packet-oriented data transmission link, characterized in that an allocation of the data received via the packet-oriented data transmission link to channels of a timeslot-oriented data format TDM formed of a periodic sequence of channel-individual information segments is undertaken such by a conversion unit (UE) that the data allocated to a sub-structure element (SE) are allocated to at least one channel of the timeslot-oriented data format (TDM);
in that a switching of the data converted into the timeslot-oriented data format ensues via a timeslot-oriented switching network module (KN); and in that the timeslot-oriented data are converted back into the packet-oriented data format and are transmitted via the packet-oriented data transmission link.
in that a switching of the data converted into the timeslot-oriented data format ensues via a timeslot-oriented switching network module (KN); and in that the timeslot-oriented data are converted back into the packet-oriented data format and are transmitted via the packet-oriented data transmission link.
2. Method according to claim 1, characterized in that a data transmission via the packet-oriented data transmission link ensues according to the ATM
data format (asynchronous transfer mode).
data format (asynchronous transfer mode).
3. Method according to one of the preceding claims, characterized in that a sub-structure element (SE) is reserved for the transmission of signalling information allocated to data transmitted via the packeted-oriented dat transmission link.
4. Method according to claim 3, characterized in that the received signalling information are communicated from the conversion unit (UE) to a control unit (STE) wherein the signalling information are converted into switching-oriented control data for the timeslot-oriented switching network module (KN).
5. Method according to one of the preceding claims, characterized in that filler cells (FZ) are inserted for an adaptation of the transmission bit rate deriving due to the arrival and the size of sub-structure elements (SE) to the transmission bit rate of a channel.
6. Method according to one of the claims 1 through 4, characterized in that filler data (FD) are inserted into a sub-structure element (SE) for an adaptation of the transmission bit rate deriving due to the arrival and the size of sub-structure elements (SE) to the transmission bit rate of a channel.
7. Method according to claim 6, characterized in that an information about the plurality of payload data communicated in the channel and an information about the plurality of filler data (FD) communicated in the channel is transmitted for each channel.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1998132999 DE19832999C2 (en) | 1998-07-22 | 1998-07-22 | Method for switching data received via a packet-oriented data transmission link |
| DE19832999.7 | 1998-07-22 | ||
| PCT/DE1999/001946 WO2000005917A1 (en) | 1998-07-22 | 1999-07-01 | Method for switching data received via a packet oriented data transmission path |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2338293A1 true CA2338293A1 (en) | 2000-02-03 |
Family
ID=7874937
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002338293A Abandoned CA2338293A1 (en) | 1998-07-22 | 1999-07-01 | Method for switching data received via a packet-oriented data transmission link |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1099358A1 (en) |
| CA (1) | CA2338293A1 (en) |
| DE (1) | DE19832999C2 (en) |
| WO (1) | WO2000005917A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6898213B1 (en) | 2000-10-16 | 2005-05-24 | Iprad Ltd. | Circuit emulation service (CES) over IP |
| DE10244980A1 (en) * | 2002-09-26 | 2004-04-15 | Siemens Ag | Method for communicating time-slot oriented information e.g. for ISDN communication network, requires communication time-slot oriented information from central communication unit to distributed communication unit |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2921424B2 (en) * | 1995-01-13 | 1999-07-19 | 日本電気株式会社 | ATM electronic exchange network system and electronic exchange used in the system |
| DE19533507C2 (en) * | 1995-09-04 | 1997-10-02 | Hartmut Dipl Ing Neus | Multiplex, access and duplex methods for a cellular radio system |
| DE19604245C2 (en) * | 1996-02-06 | 2000-07-06 | Siemens Ag | Method for transmitting time-division multiplex channel shape digital signals via an ATM transmission device |
| CN1131624C (en) * | 1996-03-08 | 2003-12-17 | Ntt移动通信网株式会社 | System and method for short-cell multiplex ATM transmission |
| GB9700930D0 (en) * | 1997-01-17 | 1997-03-05 | Northern Telecom Ltd | Distribution network |
| DE19757598A1 (en) * | 1997-12-23 | 1999-07-08 | Siemens Ag | Data exchange method in ATM exchange |
| DE19818776A1 (en) * | 1998-04-27 | 1999-11-04 | Siemens Ag | Method for connecting communication systems over a packet-oriented data transmission path |
-
1998
- 1998-07-22 DE DE1998132999 patent/DE19832999C2/en not_active Expired - Fee Related
-
1999
- 1999-07-01 WO PCT/DE1999/001946 patent/WO2000005917A1/en not_active Application Discontinuation
- 1999-07-01 CA CA002338293A patent/CA2338293A1/en not_active Abandoned
- 1999-07-01 EP EP99944231A patent/EP1099358A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE19832999A1 (en) | 2000-01-27 |
| DE19832999C2 (en) | 2001-10-11 |
| EP1099358A1 (en) | 2001-05-16 |
| WO2000005917A1 (en) | 2000-02-03 |
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