Inter-related switching, activity compression and demand assignment

• US 4,009,344 A
• Filed: 12/30/1974
• Issued: 02/22/1977
• Est. Priority Date: 12/30/1974
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Flemming, Donald C.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/537,212
• Time in Patent Office: 785 Days
• Field of Search: 179/15.55 T, 179/15 BA, 179/15 A, 179/15 BV, 179/15 BW, 179/15 AT, 179/15 AQ, 179/15 BS, 325/4, 343/100 ST, 340/172.5
• US Class Current: 370/321
• CPC Class Codes: H04B 7/2123 Variable assignment, e.g. demand assignment
• CPC Class Codes: H04Q 11/04 for time-division multiplexing H04Q11/0001 takes precedence

Abstract

Digital exchange terminals are linked by earth satellite in a privately coordinatable time division switching and communication network system serving multiple voice telephone and data communication lines. Terminals operate in each satellite time division frame to pass information switchably between variously paired lines and groups of n buffer stores, and between up to m (less than n) stores of each group (addressed in predetermined time order as internal time division channels termed virtual channels) and associated time-ordered groups of up to m external (satellite) channels. The selective switching between internal and external channels is termed activity compression handling. The external channels are adaptively appropriated to the terminals by demand assignment. Demand information exchanged between terminals at all network nodes is processed through a predetermined and pretimed reassignment computation process executed at all terminals. The terminals then exchange information representing proposed (bid) reassignments of external channels. In the absence of conflict the bid assignments are instituted. The activity compresssion acts as an intrinsic limiting factor on demand when more than m virtual channels are occupied.

Claims

1. In a time division multiple access demand assigned communication system including multiple digital exchange terminals linked for time division communication by a multiaccessible communication transmission facility, said exchange terminals serving to switchably link multiple space separated lines carrying digital data and digitalized voice telephone information traffic to time channels of said facility, said facility having fixed assigned order channels and demand assignable traffic channels in recurrent time division frames for respectively carrying supervisory information and line traffic information between said terminals, terminal apparatus comprising:

means for utilizing information exchanged with other terminals through said order channels for demand assigning a variable number of said traffic channels to the respective terminal;

means containing multiple buffer storage locations for temporary storage of traffic information in transit between multiple lines of the respective terminal and traffic channels demand assigned to the respective terminal;

first selective switching mean operating in time coordination with said time division frames for passing traffic information between selected said storage locations and successive said assigned traffic channels in each frame; and

second selective switching means operating in time coordination with said first switching means for passing traffic information between said storage locations and lines variously paired with said locations.

2. Terminal apparatus in accordance with claim 1 wherein said means for demand assigning said traffic channels includes:

means for determining over a predetermined number of said frames the number of calls for connection to said lines of said respective terminal which cannot be completed due to present assignment of insufficient traffic channels to said respective terminal;

means for exchanging information with other terminals at predetermined intervals indicating said number of uncompletable calls; and

means for utilizing said exchanged information to control selective reassignment of traffic channels to said respective terminal.

3. Apparatus in accordance with claim 1 wherein said second selective switching means repeatedly samples said lines at a rate suitable for intelligible bidirectional conveyance of voice telephone traffic between lines through said facility;

and wherein said frame has a time duration which is long by comparison to the time interval between successive samplings of a single said line.

4. Apparatus in accordance with claim 3 wherein each traffic channel includes multiple bit sub-channels sufficient to carry a packet of multiple voice bit samples of a single line and said storage locations each contain multiple bit sub-locations for storage of a packet of bits relative to the respectively paired line.

5. A method of using a time division multiple access communication system having multiple access nodes, multiple time division order channels fixed assigned to respective said nodes, said multiple time division traffic channels variably assignable to said nodes on demand;

said method comprising;

demand assigning said traffic channels to said nodes;

storing digital data and digitalized voice telephone information at each node, in randomly accessible buffer storage, in transit between said respectively assigned traffic channels and multiple space separated lines served by the respective node;

switchably pairing said respective lines with various addresses of said buffer storage for routing information variously between said buffer storage and said lines;

recurrently linking variously selected said addresses in predetermined groups of said addresses in predetermined time order with successive said demand assigned traffic channels in ordered groups of said traffic channels;

thereby virtually connecting each said address-paired line with a remotely paired line, through said traffic channels and a remote said node, but actually connecting only selected said lines through said traffic channels in each time division frame of said system.

6. A method in accordance with claim 5 including:

determining relative demand for traffic channels at said access nodes;

exchanging information indicating said demand between said nodes via said order channels;

utilizing said exchanged demand information to control appropriation of said traffic channels at said nodes at predetermined intervals encompassing multiple said time division frames; and

adapting said line pairing and communicative linking at each node to operate relative to the traffic channels appropriated in the preceding utilizing step.

7. Apparatus for multiplex switching to provide selective access to a time division multiple access communication facility having both fixed assigned time division channels and demand assignable time division channels comprising:

means utilizing communications via said fixed assigned channels for appropriating said demand assignable channels variously at an access node of said facility in coordination with appropriation processes at other nodes;

means containing randomly accessible buffer storage locations representing virtual channels of communication linkable to demand assignable channels of said facility;

means for communicatively linking selected said virtual channels with successive said appropriated channels in each time division frame of said facility;

means for switchably linking individual said virtual channels with individual lines for voice telephone and data communication;

means for adaptively passing voice and data information traffic in digital signal form between said lines and said appropriated channels via respective said virtual channels.

8. Apparatus in accordance with claim 7 wherein said means for appropriating utilizes demand information, channel utilization information and proposed reassignment information exchanged via said reserved channels with like apparatus at other access nodes of said facility.

9. Apparatus in accordance with claim 7 wherein said means for appropriating includes:

means for exchanging demand and channel utilization information periodically with other apparatus having access to said facility, over said reserved channels; and

means for utilizing the exchanged information for unambiguously appropriating said demand assignable channels in accordance with a predetermined distributed demand assignment protocol.

10. Apparatus in accordance with claim 7 wherein said means for appropriating includes means for acquiring synchronization relative to other apparatus having access to said facility for coordinating the times at which said appropriation is instituted.

11. Apparatus in accordance with claim 10 wherein said means for acquiring synchronization operates on plural time interval boundaries including bit times, frame times, superframe times and masterframe times;

and said means for appropriating coordinates its appropriations on masterframe boundaries.

12. A method of communication relative to a time division multiple access communication facility having both reserved and demand assignable time division channels comprising:

exchanging information through said reserved channels of said facility;

assigning said demand assignable channels to access nodes of said facility based upon said information;

establishing adaptively variable virtual connection paths at each node between multiple input/output ports usable by separate voice telephone and data circuits and said demand assigned channels;

passing voice and data traffic in digital signal form between said ports and said demand assigned channels utilizing said virtual connection paths.

13. A method according to claim 12 including coordinating said assigning of said demand assignable channels to commence simultaneously at all nodes of said facility.

14. A method according to claim 12 comprising:

exchanging demand and channel utilization information intermittently between access nodes of said facility via said reserved channels; and

utilizing the exchanged information at each node in accordance with a predetermined distributed demand assignment protocol common to all access nodes to determine the number of demand assignable channels to be assigned to the respective node.

15. A method in accordance with claim 12 including:

exchanging synchronization information between said nodes for coordinating the timing of said demand assigning step.

16. A method in accordance with claim 15 including:

synchronizing the information exchange on frame, superframe and masterframe time boundaries, in order to coordinate the demand assignment processes at all access nodes on masterframe boundaries.

17. A method in accordance with claim 12 wherein:

said facility includes a satellite communication transponder.

18. A method of using an access node of a time division multiple access communication facility comprising:

establishing virtual time division connection links through m time division traffic channels of said facility serving up to n (greater than m) separate data and voice telephone lines concurrently;

performing activity compression in each time division frame of communication of said facility to link only up to m selected active said lines with said m traffic channels; and

varying the number m of traffic channels assigned to said node using information communicated over said facility denoting the distribution of idle said channels and unfulfilled demand for establishment of connection links;

said unfulfilled demand being intrinsically restricted by said activity compression.