Statistical contention control for star configured communication networks

• US 4,531,238 A
• Filed: 12/03/1981
• Issued: 07/23/1985
• Est. Priority Date: 12/03/1981
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Stewart, Lawrence C., Rawson, Eric G., Schmidt, Ronald V., Murray, Hallam G.
• Primary Examiner(s): Martin, John C.
• Assistant Examiner(s): Coles, Edward L.
• Application Number:
  US06/326,869
• Time in Patent Office: 1,328 Days
• Field of Search: 455/601, 455/606, 455/607, 455/58, 455/9, 340/825.50, 340/825.51, 350/96.15, 350/96.16, 370/85, 370/93, 370/95, 375/3
• US Class Current: 398/62
• CPC Class Codes: H04B 10/27 Arrangements for networking
• CPC Class Codes: H04B 10/272 Star-type networks or tree-type networks
• CPC Class Codes: H04B 10/29 Repeaters
• CPC Class Codes: H04L 12/44 Star or tree networks

Abstract

An active repeater for a star configured communications network includes a threshold detector for collision detection. Whenever two or more terminals simultaneously feed data into the repeater, a threshold sensitive collision detector is triggered to logically isolate the data from the output of the repeater and to logically substitute a predetermined collision signal therefor, thereby causing the competing terminals to reset to retry the transmissions at randomly selected later times.

Claims

1. In a star configured communications network having a plurality of terminals, a common node, and a plurality of bidirectional communication channels coupled between said common node and respective ones of said terminals for transferring data to and from said terminals;

the improvement comprising

a data detector within said common node for detecting data received from said terminals,

a collision signal generator for supplying a collision signal,

a collision detector within said common node for supplying a control signal whenever data is being received from at least two of said terminals simultaneously,

logic means within said common node;

said logic means being coupled to said data detector, said collision signal generator, and said collision detector for selectively coupling said data detector and said collision signal generator to said communication channels in the absence and presence of said control signal, respectively, whereby data is transferred to said terminals whenever data is being received from only one of said terminals and said collision signal is transferred to said terminals in lieu of data whenever data is being received from at least two of said terminals simultaneously, and

means coupled to said terminals for resetting said terminals in response to said collision signal, whereby said terminals contend for control of said network and are subject to being reset whenever they compete for control.

2. The improvement of claim 1 further including

a plurality of transceivers for interfacing said terminals to respective ones of said communication channels, said transceivers including means for applying reset signals to said terminals in response to said collision signal;

an active repeater within said common node for amplifying and filtering said data.

3. The improvement of claim 2 wherein

said communication channels are optical links, and

said transceivers and said repeater include electrical/optical transformation means for interfacing said terminals and said repeater, respectively, to said optical links.

4. The improvement of claim 2 wherein

said repeater includes a plurality of dedicated receivers for amplifying and filtering data received via respective ones of said channels, and output means for feeding signals back into said channels for re-transmission to said transceivers, and

said data detector has a predetermined threshold, whereby said output means is isolated from said receivers in the absence of data.

5. The improvement of claim 4 wherein

said communication channels are optical links,

said transceivers include electrical/optical transformation means for interfacing said terminals to said optical links, and

said receivers and said output means include electrical/optical transformation means for interfacing said repeater to said optical links.

6. The improvement of claim 4 wherein

said receivers have output stages which are interconnected at a summing node;

and

said data detector and said collision detector have inputs which are coupled to said summing node to determine when data is being applied to said receivers and to determine when data is being applied to more than one of said receivers, respectively.

7. The improvement of claim 6 wherein

said communication channels are optical links,

each of said optical links includes a pair of optical waveguides,

said transceivers include electrical/optical transformation means for interfacing said terminals to the waveguides of respective ones of said optical links,

said receivers include electrical/optical transformation means for interfacing said repeater to one of the waveguides of each of said optical links, and

said output means include electrical/optical transformation means for interfacing said repeater to the other waveguide of each of said optical links.

8. The improvement of claim 6 wherein

said data detector and said collision detector have predetermined voltage thresholds, and

said data detector and said collision detector have inputs coupled to said summing node by means which develop a voltage that is a function of the number of said receivers that are receiving data at any given time.

9. The improvement of claim 8 further including

a low pass filter coupled between said collision detector and said logic means for filtering said control signal, thereby suppressing false collision signalling.

10. The improvement of claim 9 wherein

said communication channels are optical links,

each of said optical links includes a pair of optical waveguides,

said transceivers include electrical/optical transformation means for interfacing said terminals to the waveguides of respective ones of said optical links,

said receivers include electrical/optical transformation means for interfacing said repeater to one of the waveguides of each of said optical links, and

said output means include electrical/optical transformation means for interfacing said repeater to the other waveguide of each of said optical links.