US 5,668,811 A · Method of maintaining frame synchronization in a communication network

Abstract

A data communication system, such as a local area network, is provided with a capability of transmitting isochronous data. Preferably the system conveys both isochronous data and non-isochronous data by time-multiplexing the data into a recurring frame structure on a four-bit nibble basis. An efficient encoding scheme permits transmission of both isochronous and non-isochronous data over existing media, such as twisted pair, without degrading bandwidth previously achieved for non-isochronous data over the same media, such as using an ethernet system. Bandwidth available for a particular isochronous source/sink is selectable and sustainable with a predefined granularity. The arriving data is de-multiplexed at the hub into separate channels for handling the separate streams by appropriate hardware. Preferably, the present invention can be implemented in a fashion that is transparent to already-installed media access controllers. Preferably, some components of the system can detect the frame-transmission capability of other components and, if such capability is lacking, can fall back to a mode compliant with existing capabilities.

Claims18

Dependent claims

In a data communications network having a first station with a plurality of ports, each port coupled to one of a first plurality of other stations, said network providing a series of communication time periods, each communication time period having a nominal length and beginning with a start delimiter signal, said ports communicating with said other stations in a series of time frames of a nominal length, each time frame beginning with a frame reference signal, a method for maintaining a desired temporal relationship between said series of communication time periods and said series of time frames, comprising:

determining the delay period between receipt of said start delimiter signal and said frame reference signal;
replacing a time frame of said nominal length with a shortened time frame in said series of time frames when said frame reference signal occurs more than a first predetermined period after said start-delimiter signal;
and
replacing a time frame of said nominal length with a lengthened time frame in said series of time frames when said frame reference signal occurs less than a second predetermined period after said start delimiter signal.

1 more element

A data communications network providing a series of communication time periods, each communication time period having a nominal length and beginning with a start delimiter signal, comprising;

a first station with a plurality of ports, each port coupled to one of a first plurality of other stations, said ports communicating with said other stations in a series of time frames of a nominal length, each time frame beginning with a frame reference signal;
means for generating said frame reference signal;
means for determining the delay period between receipt of said start delimiter signal and the generation of said frame reference signal;
means for replacing a time frame of said nominal length with a shortened time frame in said series of time frames when said frame reference signal occurs more than a first predetermined period after said start-delimiter signal;
and
means for replacing a time frame of said nominal length with a lengthened time frame in said series of time frames when said frame reference signal occurs less than a second predetermined period after said start delimiter signal.

3 more elements

Dependencies are inferred from the claim text.

Method of maintaining frame synchronization in a communication network

Life of this patent

Method of maintaining frame synchronization in a communication network

Life of this patent

Abstract

Claims18