Telecommunications apparatus and method

• US 5,862,136 A
• Filed: 05/30/1996
• Issued: 01/19/1999
• Est. Priority Date: 07/07/1995
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Irwin, George Frank
• Primary Examiner(s): Patel, Ajit
• Application Number:
  US08/655,402
• Time in Patent Office: 964 Days
• Field of Search: 370/375, 370/376, 370/389, 370/395, 370/398, 370/351-357, 370/412, 370/378, 370/379, 370/428
• US Class Current: 370/395.4
• CPC Class Codes: H04J 2203/0089 Multiplexing, e.g. coding, scrambling, SONET
• CPC Class Codes: H04L 12/5601 Transfer mode dependent, e.g. ATM
• CPC Class Codes: H04L 12/64 Hybrid switching systems
• CPC Class Codes: H04L 12/6402 Hybrid switching fabrics
• CPC Class Codes: H04L 2012/5619 Network Node Interface, e.g. tandem connections, transit switching
• CPC Class Codes: H04L 2012/5625 Operations, administration and maintenance [OAM]
• CPC Class Codes: H04L 2012/563 Signalling, e.g. protocols, reference model
• CPC Class Codes: H04L 2012/5672 Multiplexing, e.g. coding, scrambling
• CPC Class Codes: H04L 49/108 using shared central buffer
• CPC Class Codes: H04L 49/255 Control mechanisms for ATM switching fabrics
• CPC Class Codes: H04L 49/3081 ATM peripheral units, e.g. policing, insertion or extraction
• CPC Class Codes: H04L 49/309 Header conversion, routing tables or routing tags
• CPC Class Codes: H04L 49/606 Hybrid ATM switches, e.g. ATM&STM, ATM&Frame Relay or ATM&IP
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A telecommunications apparatus for transporting ATM cells having either of isochronous units of payload data and asynchronous units of payload data, between receiving and transmitting ports includes a buffer for asynchronously queuing units of payload data received from the receiving ports and for subsequently transmitting the queued units of payload data in a time division multiplex data stream toward the transmitting ports. A timeslot interchanger is used to reorder a time defined sequence of isochronous units of payload data from the first data stream into a second time defined sequence of isochronous units of payload data in a second TDM data stream. An outgoing TDM data stream is assembled by transferring the first data stream into the outgoing data stream while substituting each payload occurrence of isochronous units from the second TDM data stream, into corresponding TDM locations in the outgoing data stream. The outgoing data stream is transmitted toward the transmitting ports whereby telephone calls are connected via the isochronous units of payload data. Delay typically inherent in telephone conversations connected via prior ATM facilities and the consequent severe echo often experience by users is substantially reduced.

Claims

1. A telecommunications apparatus for transporting packets having either of isochronous units of payload data and asynchronous units of payload data, between receiving and transmitting ports, comprising:

buffer means for asynchronously queuing units of payload data received from the receiving ports and for subsequently transmitting the queued units of payload data in a time division multiplex (TDM) format of a first data stream; and

a timeslot interchanger for reordering a time defined sequence of isochronous units of payload data from the first data stream into a second time defined sequence of isochronous units of payload data in a second data stream of said TDM format;

means for assembling an outgoing data stream by transferring each payload occurrence of isochronous units from said TDM format in the second data stream, into the corresponding TDM location of a first data stream and for transmitting the outgoing data stream toward the transmitting ports.

2. A telecommunications apparatus as defined in claim 1 further comprising:

means for stuffing at least one data unit into each packet with an odd number of data units being received at one of the receiving ports, to generate a stuffed packet with an even number of data units; and

means for removing each stuffed data unit when the stuffed packet is being received at one of said transmitting ports, to regenerate a packet with said odd number of data units.

17. A telecommunications apparatus as defined in claim 1 wherein said packets are in accordance with a 53 octet ATM cell standard, wherein each ATM cell includes a cell header and either of isochronous units of cell payload data and asynchronous units of cell payload data, the telecommunications apparatus further comprising;

a controller means being responsive to information contained in a cell header for simultaneously issuing an egress buffer address pointer and an egress timeslot interchanger address pointer, for causing the buffer means to transmit a queued isochronous payload data, corresponding to said cell header, in the first data stream and for causing the timeslot interchanger to provide a corresponding cell payload of isochronous reordered data in the second data stream;

whereby the assembling means is provided with a cell payload in the second data stream, at an appropriate time for transmission in the outgoing data stream while at the same time the timeslot interchanger is provided with a cell payload from the first data stream.

3. A method for transporting packets having either of isochronous units of payload data and asynchronous units of payload data, between receiving ports and transmitting ports, comprising the steps of:

asynchronously queuing received packets from the receiving ports for time division multiplex (TDM) transmission toward a transmitting port of destination;

reordering a sequence the isochronous units having been queued, into a second sequence, for TDM transmission during a frame period toward a transmitting port of destination;

TDM transmitting the asynchronous units in packets and the reordered isochronous units in packets toward the transmitting ports of destination;

whereby the isochronous units of payload data are time switched during transport between the receiving ports and the transmitting ports.

4. A method as defined in claim 3 wherein the packets are in accordance with a 53 octet ATM cell standard, the method comprising the further steps of:

stuffing an octet into each ATM cell to generate a 54 octet cell prior to the step of asynchronously queuing a received packet, and

removing the stuffed octet when it is received at one of said transmitting ports to regenerate a standard ATM cell.

5. A telecommunications facility for transporting data packets having headers and payloads between a plurality of input ports and a plurality of output ports, comprising;

a concentrator for receiving data packets from the plurality of input ports and for multiplexing the payloads into an incoming data stream and multiplexing the headers into an incoming header stream;

a distributor for directing outgoing headers from an outgoing header stream along with respective payloads from an output data stream to those of a plurality of output ports to which the data packets are destined;

a memory controller being responsive to information contained in the headers in the incoming header stream, for generating queue control information for relating each data packet to one of the plurality of output ports, for generating the outgoing headers in the outgoing header stream for data packets destined for any of the plurality outport ports, and for generating scheduling information;

a buffer for receiving the incoming data stream and being responsive to the queue control information for queuing the payload of each related data packet into a queue associated with the output port for which the payload is destined, and for subsequently selecting and transferring queued payload data units of each data packet into an intermediate data stream;

timeslot switching means for receiving a frame of payloads from the intermediate data stream and in response to timeslot switching information, for reordering data units from selected payloads into a switched data stream, and in response to the scheduling information from the controller for multiplexing reordered data units of a preceding frame of payloads from the switched data stream with the unselected payloads of data from the intermediate data stream into the outgoing data stream.

6. A telecommunications facility as defined in claim 5 being limited to transporting data packets of a fixed length, each consisting of a predetermined plurality of header data units followed by a predetermined plurality of payload data units, the header data units each including a source indication as to whether or not one or more of the payload data units is from a synchronous source;

and

wherein the memory controller is responsive to each source indication for generating the scheduling information; and

wherein said timeslot switching means is limited to receiving those payloads which include at least one data unit from a synchronous source as these payloads occur throughout a frame period, in response to the scheduling information.

7. A telecommunications facility as defined in claim 6 being further limited to transporting any data packet with a payload of at least one asynchronous data unit to the exclusion of any isochronous data unit, and to transporting any data packet with a payload of at least one isochronous data unit to the exclusion of any asynchronous data unit.

8. A method for transporting data packets having headers and payloads between a plurality of input ports and a plurality of output ports, comprising the steps of;

receiving data packets from the plurality of input ports and multiplexing the payloads into an incoming data stream and multiplexing the headers into an incoming header stream;

generating queue control information for relating each received data packet to one of the plurality of output ports, in response to information contained in the headers in the incoming header stream;

selecting and queuing the payloads of data packets from incoming data stream into queues associated with the output ports for which the payloads are destined, subsequently selecting and transferring queued payload data units of each data packet into an intermediate data stream, in response to the queue control information;

in response to information contained in the headers in the incoming header stream generating an outgoing header stream of outgoing headers;

receiving a frame of payloads data units from the intermediate data stream and in response to timeslot switching information, reordering selected data units in the frame into a switched data stream;

multiplexing the unselected payloads of data from the intermediate data stream with payloads of a preceding frame from the switched data stream into an output data stream; and

a distributing outgoing headers from the outgoing header stream in association with respective payloads from the output data stream to at least one port of a plurality of output ports for which the payloads are destined.

9. A method of operating a telecommunications switching facility for receiving and transmitting ATM cells having either of isochronous payload data and asynchronous payload data between a plurality of ATM ports;

the method comprising the steps of;

receiving incoming headers from the plurality ATM ports in a predefined cyclic order;

serially transferring incoming payload octets of incoming ATM cells from receiving ones of the plurality of ATM ports into receive TDM timeslots exclusively preallocated to each of the ATM ports,

elastically queuing cell payloads from the receive TDM timeslots and subsequently reading octets of the elastically queued cell payloads into intermediate TDM timeslots being exclusively preallocated to each of the ATM ports;

accepting the payload octets in a sequence in which said payload octets appear in the intermediate TDM timeslots, throughout a predefined periodic frame occurrence, and presenting selected ones of said octets in a reordered sequence in isochronous TDM timeslots;

multiplexing octets from either of the intermediate TDM timeslots and the isochronous TDM timeslots, into transmit TDM timeslots;

generating outgoing header octets, in response to those of the incoming headers which meet predetermined parameters, into header TDM timeslots, in synchronism with the transmit TDM timeslots;

serially transferring payload octets from the transmit TDM timeslots and header octets from the header TDM timeslots to the respective payload and header portions of an outgoing ATM cell for which the payload octets are destined;

whereby a data sample of an isochronous payload having been received in one of the payload octets of an ATM cell during one of said periodic frame occurrences is retransmitted in a selectable one of the payload octets of a full frame of octets within a following periodic frame occurrence.

10. A telecommunications switching facility for receiving and transmitting ATM cells having either of isochronous payload data and asynchronous payload data between a plurality of ATM ports;

the telecommunications switching facility comprising;

a receive TDM bus for transporting payload octets from ATM cells in time division multiplexed (TDM) frame defined timeslots;

an intermediate transfer bus for transporting payload octets destined for ATM cells in TDM frame defined timeslots;

a transmit TDM bus for transporting payload octets to ATM cells in TDM frame defined timeslots;

a receive header bus for transporting header octets from ATM cells;

a transmit header bus for transporting header octets to ATM cells;

an asynchronous buffer having a plurality of FIFO queue elastic storage functions for queuing cell payloads from the receive TDM bus, and for reading octets of cell payloads from the elastic storage queuing functions onto the intermediate transfer bus;

switch means for accepting the payload octets in a sequence in which said payload octets appear on the intermediate transfer bus, throughout a predefined periodic frame occurrence, and for presenting selected ones of said octets in a reordered sequence throughout a subsequent one of the predefined periodic frame occurrences via an isochronous payload bus;

multiplexing means for passing octets from either of the intermediate transfer bus and the isochronous payload bus, into the TDM frame defined timeslots of the transmit TDM bus

an access unit including;

incoming header transfer means for transferring header octets from the plurality ATM ports to the receive header bus in a predefined cyclic order,

a control means being responsive to a header from the receive header bus, which meets predetermined parameters, for transmitting a header onto the transmit header bus;

outgoing header transfer means for transferring header octets from the transmit header bus to the plurality of ATM ports in a predefined cyclic order,

incoming payload transfer means for serially transferring payload octets of incoming ATM cells from receiving ones of the ATM ports into receive TDM bus timeslots exclusively preallocated to each of the ATM ports, and

outgoing payload transfer means for serially transferring payload octets destined for outgoing ATM cells from transmit TDM bus timeslots exclusively preallocated to each of the ATM ports;

whereby a data sample of an isochronous payload having been received in one of the payload octets of an ATM cell during one of said periodic frame occurrences is retransmittable as any one of the payload octets of a full frame of octets within a next following periodic frame occurrence.

11. A telecommunications switching facility comprising;

a memory controller;

a plurality of ports (511-519) for receiving and transmitting ATM cells having either of isochronous payload data and asynchronous payload data and;

an asynchronous buffer (560) for queuing a received ATM cell in relation to a destination one of the plurality of ports and for transmitting the queued cell at a time designated for receipt at the destined one of the ports in response to addressing and control signals from the memory controller;

switch means (520) being responsive to payload data having been transmitted from the asynchronous buffer during a frame period (125 μ

s), for storing the payload data in a first sequence of data storage locations; and

for reproducing said stored data in second sequence, wherein one of the first sequence and the second sequence is of a fixed order and the other of the sequences is variable in order; and

multiplexing means (722,

     723) for passing a cell payload from either of the asynchronous buffer and a cell payload retransmitted from the storage locations in the second sequence to the destination one of the plurality of ports;

whereby a data sample having been transmitted in one of the payload octets of an ATM cell is retransmittable in any one of the payload octets of a full frame of octets within a time period of less than two frame periods from the moment of its storage to its port of destination.

12. A telecommunications switching facility as defined in claim 11 further comprising;

port access means (500) for transferring the ATM cell payload data octets between the buffer means and the ports in a time division multiplex TDM signal format, and for transferring the ATM cell payload data between the multiplexing means and the ports in a time division multiplex TDM signal format.

13. A telecommunications switching facility as defined in claim 12, wherein the port access means includes lower and upper access units, each comprising;

a plurality of pairs of incoming octet latches(601608) for transferring octets being serially receiving from a group of a corresponding plurality of the ports in octet pairs onto a corresponding plurality of buses;

a payload multiplexer (610-612,

     728) for interleaving the octet pairs from the plurality of buses into a time division multiplex (TDM) format in response to a repeating sequence of a corresponding plurality of port payload selection signals;

a header multiplexer (606,

     727) for interleaving the octet pairs from the plurality of buses into a time division multiplex (TDM) format in response to a repeating sequence of a corresponding plurality of port header selection signals.

14. A telecommunications switching facility as defined in claim 13, further comprising;

a sequencer (709), being responsive to occurrences of a periodic frame signal and a periodic clock signal for repetitively generating said plurality of sequences of port payload selection signals onto a corresponding plurality of payload selection leads, and for repetitively generating said plurality of sequences of port header selection signals onto a corresponding plurality of header selection leads, such that an assertion interval of any one of the port header selection signals is mutually exclusive of an assertion interval of any one of the others of the port header selection signals and mutually exclusive of payload selection signals for the same port;

whereby the lower and upper access units each transfer two payload octets from alternate pairs of the ports in alternate odd and even TDM timeslots.

15. A telecommunications switching facility as defined in claim 12, wherein the asynchronous buffer comprises:

first and second random access memories (RAM)s (741,742), each RAM having a write port for storing octet pairs at address defined storage locations and a read port for reproducing the octet pairs from said address defined storage locations;

an ingress commutator means (FIG.

     13) for presenting the octets, from 108 timeslots in a port of origin sequence repeated during each of 54 subframes per frame period, to the write ports; and

an egress commutator means (FIG.

     15) for transferring octets, having been reproduced at either of the read ports, onto a predetermined part of an intermediate TDM bus (547) in odd ones and even ones of said time slots.

16. A telecommunications switching facility as defined in claim 11, wherein the memory controller comprises:

write means being responsive to clock and frame signals for generating write memory pointers; and

read means being responsive to switching information as well as said clock and frame signals for generating read memory pointers, the telecommunications switching facility further comprising;

a first connection memory for storing first timeslot switching instructions at address defined storage locations, and for reproducing the first timeslot switching instructions from said address storage locations;

a second connection memory for storing second timeslot switching instructions at address defined storage locations, for reproducing the second timeslot switching instructions from said address storage locations;

first and second data memories each having identical address defined storage locations for storing pairs of octets;

an ingress means being responsive to an occurrence of the frame signal and a sequence of the write memory pointers for depositing a frame of octets of said payload data identically in a one half of said identical address defined storage locations in the first and second data memories;

an egress means being responsive to an occurrence of the frame signal and to each read memory pointer for causing a corresponding series of the first timeslot connection addresses to be reproduced by the first connection memory and a corresponding series of the second timeslot connection addresses to be reproduced by the second connection memory;

means for coupling the first and second timeslot addresses to the first and second data memories respectively, whereby first and second frames of octet pairs of reordered first and second sequences are reproduced by the first and second data memories; and

means responsive to a portion of each of the first and second timeslot connection addresses for selectively passing one octet of each of said octet pairs to provide said stored data to said multiplexing means.

18. A telecommunications apparatus as defined in claim 11 wherein the memory controller comprises;

means being responsive to information contained in a cell header for simultaneously issuing an egress buffer address pointer and an egress switch address pointer, for causing the asynchronous buffer to transmit a queued isochronous payload data for a cell corresponding to said cell header, and at the same time for causing the timeslot interchanger to provide a corresponding cell payload of isochronous reordered data in said second sequence.

19. A telecommunications apparatus as defined in claim 16 wherein the read means in the memory controller comprises;

means being responsive to information contained in a cell header for simultaneously issuing an egress buffer address pointer and an egress switch address pointer, for causing the asynchronous buffer to transmit a queued isochronous payload data for a cell corresponding to said cell header, and at the same time for causing the timeslot interchanger to provide a corresponding cell payload of isochronous reordered data in said second sequence.

20. A switching system for accommodating both asynchronous and isochronous telecommunications traffic comprising;

means for receiving ATM cells from ports of origin and organizing the payloads of the ATM cells into frames of timeslots in a time division multiplex (TDM) transmission medium;

means for reorganizing ATM cells from the TDM transmission medium and distributing the ATM cells to ports of destination; and

a timeslot switching apparatus including;

means for collecting frames of payloads, having datas of isochronous origins, from the time division multiplex (TDM) transmission medium,

means for reordering the datas of a collected frame of payloads to produce reordered payloads, and

means for substituting the reordered payloads for the corresponding payloads in the next frame of payloads in the transmission medium;

whereby a delay introduced by the switching system into the transmission of a telephone conversation is of a duration of less than two frame periods.

21. An ATM switching facility comprising:

a switching system having a plurality of ATM ports and a time switch means for providing voice band connections between telephony lines and trunks for servicing telephony terminal apparatus and interoffice telecommunications;

at least one peripheral group unit for interfacing any of the telephony lines and trunks with one of the ATM ports and for generating and for receiving signalling and supervision information on behalf of said any of the telephone lines and trunks; and

a call controller being coupled to the switching system via one of said ATM ports and being responsive to receiving signalling and supervision information via said one ATM port for transmitting timeslot switching information via said one ATM port for controlling the time switch means to set up and tear down telephone calls between any of said lines and trunks.

22. An ATM switching network comprising:

a first switching system having a plurality of ATM ports and a time switch means for providing voice band connections between first telephony lines and trunks for servicing telephony terminal apparatus and interoffice telecommunications;

at least one peripheral group unit for interfacing any of the telephony lines and trunks with one of the ATM ports of the first switching system and for generating and for receiving signalling and supervision information on behalf of said any of the first telephone lines and trunks;

a second switching system having a plurality of ATM ports and a time switch means for providing voice band connections between second telephony lines and trunks for servicing telephony terminal apparatus and interoffice telecommunications;

at least one peripheral group unit for interfacing any of the telephony lines and trunks with one of the ATM ports of the second switching system and for generating and for receiving signalling and supervision information on behalf of said any of the second telephone lines and trunks;

an ATM trunk being connected between ATM ports of the respective first and second switching systems for coupling ATM cells therebetween including ATM cells with signalling and supervision information; and

a call controller being coupled to one of the first and second switching systems via a respective one of said ATM ports and being responsive to receiving signalling and supervision information via said one ATM port for transmitting timeslot switching information via said one ATM port for controlling the time switch means respectively of the first and second switch means to set up and tear down telephone calls between any of said lines and trunks;

whereby the control functions of a call controller are shared between a plurality of the switching systems in the ATM switching network without physical geographical constraint.

23. An ATM switching network as defined in claim 22 comprising:

an ATM switch node, at least one ATM trunk coupling each of the switching systems with the ATM switch node and wherein the call controller is a central call controller being coupled with the time switch means via the ATM node.