Method and apparatus for prioritized transmission of data over a network

• US 6,272,147 B1
• Filed: 09/26/1997
• Issued: 08/07/2001
• Est. Priority Date: 09/27/1996
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Spratt, Michael Peter, Sharon, Oran
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Duong, Frank
• Application Number:
  US08/938,119
• Time in Patent Office: 1,411 Days
• Field of Search: 370/235, 370/236, 370/345, 370/347, 370/350, 370/433, 370/437, 370/443, 370/444, 370/445, 370/447, 370/451, 370/455, 370/458, 370/461
• US Class Current: 370/447
• CPC Class Codes: H04L 12/2803 Home automation networks
• CPC Class Codes: H04L 12/2838 Distribution of signals within a home automation network, e.g. involving splitting/multiplexing signals to/from different paths adaptations of television systems for transmission by electric cable for domestic distribution H04N7/106; hybrid transport H04L12/6418; home network arrangements specially adapted for distribution of digital video signals H04N7/24
• CPC Class Codes: H04L 12/40143 involving priority mechanisms hybrid switching fabrics H04L12/6402; intermediate storage or scheduling H04L49/90; time-division multiplex systems H04J3/00
• CPC Class Codes: H04L 12/407 with decentralised control

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.

Claims

1. 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.

2. A method as claimed in claim 1, wherein the fairness process of each station comprises the further steps of:

detecting whether its contention resolution process has been disabled for a predetermined period of time; and

if so, re-enabling its contention resolution process.

3. A method as claimed in claim 1, further comprising the step of fixing the ranking of each station.

4. A method as claimed in claim 1, wherein each station performs a ranking allocation process prior to an initial transmission on the bus, which comprises the steps of:

determining, from the bus, rankings currently in use by the other station(s); and

allocating to itself a current ranking to one extreme of the determined rankings.

5. A method as claimed in claim 4, wherein the ranking allocation process performed by each station comprises the further steps of:

determining whether its current ranking is the same as that of the other station, or another of the stations; and

if so, recommencing its ranking allocation process.

6. A method as claimed in claim 5, further comprising the step of waiting for a pseudo-random period of time before the recommencement of the ranking allocation process.

7. A method as claimed in claim 4, wherein the ranking allocation process performed by each station comprises the further steps of:

detecting whether the ranking next to that station'"'"'s current ranking in the direction towards the other extreme of the rankings continues to be in use; and

if not, re-allocating to itself that next ranking as its current ranking.

8. A method as claimed in claim 1,

wherein the stations are high-priority stations, the method further comprising the step of:

making at least one low-priority station operable to transmit data on the bus, the low-priority station(s) performing a different contention resolution process to the high-priority stations.

9. A method as claimed in claim 8, comprising the step of operating by the or each low-priority station, a carrier-sense multiple access with collision detection protocol.

10. A method as claimed in claim 8, comprising the steps of:

making the or each low-priority station operable to perform a contention resolution process prior to transmission of data on the bus, the contention resolution process commencing when that station does not sense any activity on the bus, or a predetermined period of time after that station senses a transition from carrier to silence on the bus, or a predetermined period of time after that station has transmitted data; and

making each high-priority station operable, immediately after transmission of data, to transmit a filler on the bus for a period of time exceeding said predetermined period(s) of time for the low-priority station(s).

11. A method as claimed in claim 10, comprising the step, by the or each low-priority station of ceasing transmission, at least temporarily, after transmission of data.

12. A method of operating a data network having a bus, and a plurality of high-priority stations and at least one low-priority station each operable to transmit data on the bus, comprising the steps of:

making the or each low-priority station operable to perform a contention resolution process prior to transmission of data on the bus, the contention resolution process commencing when that station does not sense any activity on the bus, or a predetermined period of time after that station senses a transition from carrier to silence on the bus, or a predetermined period of time after that station has transmitted data; and

making each high-priority station operable, immediately after transmission of data, to transmit a filler on the bus for a period of time exceeding said predetermined period(s) of tie for the low-priority station(s).

13. A method as claimed in claim 12, further comprising step of ceasing, by the or each low-priority station, transmission, at least temporarily, after transmission of data.

14. A method as claimed in claim 12, further comprising the step of operating, by the or each low-priority station, a carrier-sense multiple access with collision detection protocol.

15. 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.

16. A station as claimed in claim 15, wherein the fairness means further comprises:

a third detector for detecting whether the disabling means has been activated for a predetermined period of time, and if so de-activating it.

17. A station as claimed in claim 15, wherein the fairness means further comprises:

a third detector for detecting whether the disabling means has been activated for a predetermined period of time, and if so de-activating it.

18. A station as claimed in claim 17, wherein the ranking means comprises:

a detector for detecting whether the ranking next to that station'"'"'s current ranking in the direction towards the other extreme of the rankings continues to be in use, and wherein the ranking means is responsive to a determination that such next ranking is not in use to re-allocate that next ranking to its station as the current ranking thereof.