Method of communication using a two-way bus with contention detection

• US 5,319,642 A
• Filed: 04/24/1992
• Issued: 06/07/1994
• Est. Priority Date: 04/26/1991
• Status: Expired due to Term

• Current Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Original Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Inventors: Ota, Takeshi
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Jung, Min
• Application Number:
  US07/873,232
• Time in Patent Office: 774 Days
• Field of Search: 370/85.2, 370/85.3, 370/85.1, 370/108, 370/94.1, 370/94.3, 359/136, 359/135, 359/118, 359/120, 359/121
• US Class Current: 370/447
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 12/44 Star or tree networks

Abstract

A communication system using a two-way bus capable of detecting contentions from nodes other than nodes concerned in communication to ensure confidentiality of communication. A plurality of nodes are connected to a two-way multiple access bus. A transmitting node first monitors the multiple access bus for contention detection before transmission and then transmits a packet only when the bus is not busy. The transmitting node further monitors the multiple access bus for a predetermined time period even after the start of transmission. In the meantime, a receiving node transmits an answer after a predetermined wait time upon reception of the packet addressed to itself. Assuming that the maximum two-way propagation delay time of the multiple access bus is τ₀, the predetermined time period during which the transmitting node monitors the multiple access bus after the start of transmission for contention detection is τ₁, and the wait time between the reception of the packet by the receiving node and the start of transmission of the answer is τ₂, such that the relationship τ₀ <τ₁ <τ₂ is satisfied.

Claims

1. A method of communication between a plurality of nodes comprising the steps of:

connecting said plurality of nodes to a multiple access bus having a bidirectionality, said multiple access bus have a maximum two-way propagation delay time τ

₀ ;

causing a transmitting node to monitor said multiple access bus for contention detection before a transmission of a packet and then causing said transmitting node to make said transmission only when said multiple access bus is not busy;

further causing said transmitting node to monitor said multiple access bus for a predetermined period τ

₁ after the start of said transmission; and

causing a receiving node to start transmitting an answer after a predetermined wait time τ

₂ upon reception of said packet if said packet is addressed to said receiving node;

wherein τ

₀ <

τ

₁ <

τ

₂.

2. The method of communication as defined in claim 1 wherein said step of causing a receiving node to start transmitting an answer after a predetermined wait time τ

₂ comprises echoing back a message of said packet after said predetermined wait time τ

₂.

3. The method of communication as defined in claim 1 further comprising the step of interrupting said transmission of said transmitting node if said answer from said receiving node is not received by said transmitting node after a lapse of a predetermined time τ

₃ from the start of said transmission;

wherein τ

₃ >

τ

₂ +τ

₀.