Local area contention network data communication system

• US 4,332,027 A
• Filed: 05/01/1980
• Issued: 05/25/1982
• Est. Priority Date: 10/01/1981
• Status: Expired due to Term

• Current Assignee: Unisys Corporation
• Original Assignee: Burroughs Corp (Unisys Corporation)
• Inventors: Spracklen, John E., Rogers, Lawrence D., Parker, Marshall M., Malcolm, Michael A., Gerhold, Mark L. C., Hodgman, Gary W.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/145,606
• Time in Patent Office: 754 Days
• Field of Search: 370/6, 370/92, 370/93, 370/94, 370/85, 455/58, 455/31, 455/50, 455/51
• US Class Current: 370/448
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]

Abstract

This disclosure relates to a station for a data transmission network which is adapted to operate in a cyclic mode for contending for access to the network channel along with other stations of the network. The three states of the cycle are the idle state, the packet-being-transmitted state and the acknowlegement period state. Each station will not begin transmission until it determines that the channel is in an idle state. Once the station has determined that the channel is idle, it will then delay for a period of time that is randomly chosen and, if the channel is still idle, will then begin transmission. In this way, contention conflicts between stations is minimized without unduly restricting communication between stations. Following transmission, the channel will again be quiescent a short period of time before the acknowledgement signal is transmitted from the receiver. Each packet of data to be transmitted is of a fixed length so as to provide for synchronization between various stations contending for access to the channel.

Claims

1. A station in a data communication network having a plurality of such stations coupled to a communication channel, said station comprising:

storage means to receive an information packet for transmission on said channel;

sensing means coupled to said channel to detect when said channel is inactive;

clock means coupled to said sensing means to determine a random period of time after said sensing means detects no activity on said channel; and

transmitting means coupled to said channel, said clock means and said storage means to transmit said packet on said channel after said random period of time and when there is no activity on said channel.

2. The station according to claim 1 further including:

receiving means coupled to said channel and to said storage means to receive an acknowledgment signal on said channel within a fixed time interval after said packet has been transmitted so as to indicate that said packet need not be retransmitted.

3. A station according to claim 1 wherein:

said clock means includes counter means driven by a random clock.

4. A station according to claim 1 wherein:

said transmitting means transmits said packet during a fixed period of time duration.

5. A station according to claim 1 further including:

channel state means coupled to said storage means, sensing means and transmitting means to maintain said station in a sequence of states which include, in order, the channel idle state, packet-being-transmitted state, and ackowledgment period state.

6. A station according to claim 5 wherein said acknowledgment period state includes a quiescent period preceding any acknowledgment.

7. A station in a data communication network having a plurality of such stations coupled to a communication channel, said station comprising:

sensing means coupled to said channel to detect when said channel is inactive;

clock means coupled to said sensing means to determine a random period of time after sensing means detects no activity on said channel; and

transmitting means coupled to said channel and said clock means to transmit an information packet on said channel after said random period of time and when there is no activity on said channel.

8. The station according to claim 7 further including:

receiving means coupled to said channel to receive an acknowledgment signal on said channel a fixed period of time after said packet has been transmitted so as to indicate that said packet need not be retransmitted.

9. A station according to claim 7 wherein:

said clock means includes counter means driven by a random clock.

10. In a station in a data communication network having a plurality of such stations coupled to a communication channel, said station including detection means coupled to said channel, clock means for determining a random period of time and transmitting means coupled to said clock means and detection means, the method comprising:

detecting when said channel is inactive;

determining a random period of time after the detection of no activity on said channel; and

transmitting an information packet on said channel after said random period of time and when there is no activity on said channel.

11. The method according to claim 10 further including:

receiving an acknowledgment signal on said channel a fixed period of time after said packet has been transmitted so as to indicate that said packet need not be retransmitted.

12. The method according to claim 10 further including:

transmitting said information packet during a fixed period of time duration.