US 6,272,147 B1Granted

Method and apparatus for prioritized transmission of data over a network

AssigneeHewlett-Packard Company

InventorsMichael Peter Spratt, Oran Sharon

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Abstract

In order to allow a data network, for example around the home, to carry real-time data such as digital video and digital audio, in addition to carrying data for example between a PC and a printer or ISDN router, and in order to permit the latter data to be handled in accordance with known protocols, such as the IEEE 802.3 CSMA/CD Ethernet protocol, the real-time data is handled on a high-priority basis. The high-priority stations, such as a digital television set, digital TV set-top box, digital VTR and CD player employ a contention resolution process which ensures that they succeed in accessing the network bus over any low-priority stations, and the high priority stations employ a fairness process which ensures that they take it in turns to access the bus.

Claims18

Dependent claims

A method of operating a data network having a bus and a plurality of stations operable to transmit data on the bus, comprising the steps of:

assigning respective rankings to those stations which wish to transmit on the bus;
performing by those stations which wish to transmit on the bus, a contention resolution process whereby those stations transmit in cycles;
transmitting, by those stations which wish to transmit on the bus, within each cycle in an order determined from their ranking,
wherein the step of performing the contention resolution process comprises the steps of:
transmitting a jam on the bus for up to a period of time dependent on the current ranking of that station;
and
detecting whether there is a collision on the bus while transmitting the jam;
and
if not, enabling transmission of data,
the method further comprising the step of making each station operable to perform a fairness process, which comprises the steps of:
detecting whether one of the stations has transmitted data succeeding a jam
without a collision;
and
if not, disabling its contention resolution process until such a detection has been made,
the method further comprising the step of:
refraining by each station which wishes to transmit further data immediately after it has transmitted data in a current cycle, from the contention resolution process until it has determined that the current cycle has been completed.

13 more elements

A station for transmitting data over a data network having a bus, comprising:

storage means for storing a respective ranking for the station;
contention resolution means for performing a process whereby the station transmits with other stations in cycles, and within each cycle the station transmits in an order relative those other stations determined from its stored ranking;
and
disabling means for disabling said contention resolution means in the event that the station wishes to transmit further data immediately after it has transmitted data in a current cycle, until the current cycle has bee completed,
wherein said contention resolution means comprises;
a transmitter for transmitting a jam on the bus for up to a period of time dependent on the current ranking of that station;
a detector for detecting whether there is a collision on the bus while said transmitter is transmitting the jam, and, if there is no collision, enabling transmission of data;
and wherein each station includes fairness means comprising a second detector for detecting whether a station on the network has transmitted data succeeding a jam without a collision, and, if not, for activating said disabling means until such a detection has been made.

5 more elements

Dependencies are inferred from the claim text.