US 4,234,952 A · Conflict resolution by retransmission delay on shared communication medium

Abstract

An apparatus for enabling communications between two or more transceivers when a plurality of transceivers share a common communication medium or channel. The geographical locations of the transceivers are such that the propagation delay between any source to destination pair is relatively a small function of the transmission duration or packet time. In order to prevent two or more transceivers from simultaneously transmitting over the common medium, each transceiver requires a control apparatus. The simultaneous transmission by two or more transceivers is not very likely due to different start times. However, if such start times differ by less than the propagation delay between the transceivers then interference will result. Hence the control apparatus includes a means of resolving such contention interferences by providing a retransmission delay to govern the transmission.

Claims10

Dependent claims

A data communication modem adapted for use in conjunction with a plurality of other modems over a shared communication medium, said modem comprising:

a transmitting and receiving means for transmitting and receiving data over the communication medium;
a first sense means coupled to said modem for detecting carrier transmission from any of the modems on the communication medium (busy) and for detecting no transmission (idle) on the communication medium;
a second sense means for detecting simultaneous transmission (interference) of more than one modem;
a computation means for determining a first duration of time between the time of transition from an idle channel to a busy channel and the time of transmission interference, and a second duration of time between the time of transmission interference and the time of transition from a busy channel to an idle channel;
and
a control means responsive to outputs from said first sense means, said second sense means and said computation means for governing transmission of said modem so that said modem will not transmit until said first sense means is not detecting carrier transmission and will interrupt transmission if interference is detected by said second sense means.

3 more elements

A data communication modem adapted for use in conjunction with a plurality of other modems over a shared communication medium, said modem comprising:

a transmitting and receiving means over the communication medium;
a first sense means coupled to said modem for detecting carrier transmission from any of the modems on the communication medium (busy) and for detecting no transmission (idle) on the communication medium;
a second sense means for detecting simultaneous transmission (interference) of more than one modem;
a computation means for determining a duration of time between transmission interference and the time of transition from a busy channel to an idle channel;
a control means responsive to outputs from said first sense means, said second sense means and said computation means for governing transmission of said modem;
and
a delay means coupled to said control means for determining a retransmission delay, said delay means including a weighting means for determining the retransmission delay by using said duration.

4 more elements

Dependencies are inferred from the claim text.

Conflict resolution by retransmission delay on shared communication medium

Life of this patent

Conflict resolution by retransmission delay on shared communication medium

Life of this patent

Abstract

Claims10