Local area communication network utilizing a round robin access scheme with improved channel utilization

• US 4,503,533 A
• Filed: 08/20/1981
• Issued: 03/05/1985
• Est. Priority Date: 08/20/1981
• Status: Expired due to Fees

• Current Assignee: Cnr-Stibnot, Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Stanford University
• Inventors: Tobagi, Fouad A., Fratta, Luigi, Borgonovo, Flaminio
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US06/294,745
• Time in Patent Office: 1,293 Days
• Field of Search: 370/85, 370/94, 370/93, 370/95, 370/86, 370/87, 370/88, 370/89, 340/825.05, 340/825.5
• US Class Current: 370/445
• CPC Class Codes: H04L 12/4013 Management of data rate on the bus systems modifying transmission characteristics according to link quality H04L1/0001
• CPC Class Codes: H04L 12/40156 by using dedicated slots associated with a priority level
• CPC Class Codes: H04L 12/417 with deterministic access, e.g. token passing
• CPC Class Codes: H04L 12/43 with synchronous transmission, e.g. time division multiplex [TDM], slotted rings

Abstract

Disclosed is a local area communication network based upon a broadcast communication system comprising an inbound channel and an outbound channel, a plurality of stations connected to both the inbound and the outbound channels, transmitting on the outbound channel which utilizes an access protocol where the the access protocol used by the stations connected to the bus is a distributed algorithm and is based upon a conflict-free round robin (RR) access scheme. The time required to switch from one active user to the next in a round is minimized (on the order of carrier detection time, and is independent of the end-to-end network propagation delay. This improvement is particularly significant when the channel data rate is so high, or the end-to-end propagation delay is so large, or the packet size is so small as to render the end-to-end propagation delay a significant fraction of, or larger than, the transmission time of a packet. Moreover, some features of the present invention make it particularly suitable for voice applications. In view of integrating voice and data, a voice/data protocol is described which allows it to meet the bandwidth requirement and maximum packet delay constraint for voice communication at all times, while guaranteeing a minimum bandwidth requirement for data traffic. The voice/data protocol constitutes a highly adaptive allocation scheme of channel bandwidth, which allows data users to steal the bandwidth unused by the voice application.

Claims

1. A local communication network comprising

a communication bus for transmitting data packets including an inbound channel, an outbound channel, and means for connecting said inbound channel to outbound channel such that data packets are transmitted in the same direction on said inbound channel and said outbound channel,

a plurality of stations S1-SN located along and connected to said communication bus where each of said stations have a respective index corresponding to the location of its connection to said bus such that carrier signals having data packets are transmitted from said stations on said outbound channel in a round robin format, each of said stations including for each round of said round robin format,

transmit means for transmitting carrier signals having data packets on said outbound channel past each station connected to said outbound channel having a higher index than the respective transmit station,

receive means connected to said inbound channel such that data packets are propagated past each of said receive means in the same order as the respective indices of said stations connected to said outbound channel thereby achieving said round robin format, and

means for controlling the transmission and reception of said data packets, said control means including

means for sensing a first carrier signal transmitted by one of said stations having a lower index on said outbound channel,

means for detecting the end of said first carrier signal and means responsive thereto for transmitting a second carrier signal having a data packet on said outbound channel,

means for aborting transmission of said second carrier signal if a third carrier signal is sensed within a predetermined period of time t_d where t_d is the time for a station to detect the presence or absence of a carrier signal on said bus.

2. A network as in claim 1 wherein said communication bus is unidirectional.

3. A network as in claim 1 wherein said communication bus is bidirectional.

4. A network as in claim 1 further including means for connecting said inbound channel to said outbound channel thereby permitting transmission of said outbound data packets on said inbound channel.

5. A network as in claim 4 wherein said inbound channel is parallel to said outbound channel.

6. A network as in claim 4 wherein the propagation delay from said transmitting and receiving means is substantially the same for all of said stations.

7. A network as in claim 4 wherein the propagation delay between any two stations on said inbound channel is substantially the same as for the respective two stations on said outbound channel.

8. A network as in claim 4 wherein said data packets include a transmission unit comprising a preamble followed by an information packet and wherein each of said stations include a transmitting tap on said outbound channel.

9. A network as in claim 8 further including means for receiving signals on said outbound channel.

10. A network as in claim 9 wherein each of said stations include a receiving tap on said inbound channel.

11. A network as in claim 4 further including means for sensing a carrier signal on said outbound channel.

12. A network as in claim 11 further including means for sensing carrier flowing in a certain direction on said outbound channel.

13. A network as in claim 12 including means for detecting a carrier signal on the upstream portion of said transmitting means.

14. A network as in claim 10 wherein each of said stations include means connected to said inbound channel for sensing a carrier signal.

15. A network as in claim 10 wherein each of said stations include means for receiving specified ones of said transmission units.

16. A network as in claim 13 wherein each of said stations include means responsive to the detection of an end of carrier signal on said outbound channel for starting transmission of one of said transmission units on said communication bus.

17. A network as in claim 16 wherein each of said stations include a receiving tap on said inbound channel and means for sensing a carrier signal on said inbound channel.

18. A network as in claim 17 wherein a succession of transmission units comprise a train and wherein each of said stations include means for sensing an end of train on said inbound channel, means responsive to said end of train for initiating transmission of a transmission unit and for simultaneously sensing for a carrier signal on said outbound channel.

19. A network as in claim 18 wherein each of said stations include means for detecting the end of one of said trains on said inbound channel, means responsive to the detection of said end of train for generating a carrier having a predetermined duration, and means for initiating transmission of a respective transmission unit following said carrier.

20. A network as in claim 16 wherein each of said stations include means for sensing carrier on said outbound channel after starting transmission of said respective transmission unit, and means for aborting transmission of said respective transmission unit if carrier is sensed on said outbound channel while transmitting.

21. A network as in claim 16 further including means for completing transmission of said transmission unit if said outbound channel is sensed as idle within a predetermined time period.

22. A network as in claim 14 wherein each of said stations include means for detecting a carrier signal on said inbound channel for a predetermined time period, means for transmitting continuously a pilot carrier signal if no carrier is detected, means for detecting the beginning of a carrier signal on said inbound channel and means responsive to the detection of said beginning of said carrier signal for terminating transmission of said pilot signal.

23. A network as in claim 20 wherein said data packets are of different type and further including means for integrating said different types of packets on said communication bus.

24. A network as in claim 23 wherein said means for integrating include means for recognizing the different types of packets on said bus.

25. A network as in claim 23 further including means for distinguishing trains of different types on said communication bus.

26. A network as in claim 25 further including means for specifying the train type indicator.

27. A network as in claim 25 further including means for recognizing the train type.

28. A network as in claim 27 including means for transmitting a particular packet on a corresponding train of the same type.

29. A network as in claim 27 wherein each of said stations include means for determining the state of the respective station for representing the type of train in progress.

30. A network as in claim 29 including means for storing information representing the previous types of trains transmitted.

31. A network as in claim 29 including means for updating the state of said station.

32. A network as in claim 31 where said means for updating are responsive to an end of train on said communication bus.

33. A network as in claim 31 where said means for updating are responsive to end of packet transmission on said communication bus.

34. A network as in claim 20 including means for controlling the length of the train on said communication bus.

35. A network as in claim 34 including means for measuring the current train length in progress on said communication bus.

36. A network as in claim 35 including means for measuring a train in progress on said inbound channel.

37. A network as in claim 34 including means for measuring the length of a train in progress on said outbound channel.

38. A network as in claim 29 including means for aborting transmission of transmission unit when a certain maximum train length is reached.

39. A network as in claim 35 including means for starting transmission of a transmission unit if the measured train length including packet information does not exceed said maximum length.

40. A network as in claim 35 including means for completing transmission of a transmission unit as long as said maximum train length is not reached.

41. A network as in claim 23 wherein each station includes at least a first state permitting transmission of a transmission unit and a second state prohibiting transmission of a transmission unit and including means responsive to said first state for permitting transmission of a transmission unit and means responsive to said second state for prohibiting transmission of a transmission unit.

42. A network as in claim 23 wherein each station includes one or more states for controlling transmission and reception of said transmission unit.

43. A network as in claim 41 including means for updating said station states.

44. A network as in claim 42 including means responsive to an end of transmission unit transmission for updating said station state.

45. A network as in claim 42 including means responsive to an end of train transmission for updating said station state.

46. A local area communication network comprising a communication bus including an inbound channel and an outbound channel, and means for connecting said inbound channel to said outbound channel such that carrier signals having data packets are transmitted in the same direction on said inbound channel and said outbound channel in a round robin format, a plurality of stations S1-SN located along and connected to said communication bus where each of said stations have a respective index corresponding to the location of its connection to said bus, each of said stations including a transmitting tap connected to said outbound channel for transmitting data packets, means for sensing a carrier signal flowing in a certain direction on said outbound channel, means for detecting an end of said carrier signal with a certain time period, and means responsive to said end of carrier for starting transmission of one of said data packets thereby achieving a round robin format.

47. A network as in claim 46 further including means for aborting transmission of said data packets if carrier is sensed on said outbound channel.

48. A network as in claim 46 including means for completing transmission of said data packets if said outbound channel is sensed as idle within a certain time period.

49. A local area communication network comprising a communication bus having an inbound channel and an outbound channel, a plurality of stations S1-SN located along and connected to said bus where each of said stations have a respective index corresponding to the locations of its connection to said bus, each of said stations including means for transmitting and receiving carrier signals having data packets on said bus in a round robin format such that said data packets are propagated past each of said stations in the same direction on said outbound channel to said inbound channel thereby achieving said round robin format, means for sensing a first carrier signal transmitted by one of said stations having a lower index on said outbound channel, and means responsive to the detection of an end of carrier signal on said outbound channel for starting transmission of one of said transmission units on said outbound channel.

50. A network as in claim 49 further including means for aborting transmission of said transmission unit if carrier is sensed on said outbound channel while transmitting.

51. A network as in claim 49 wherein said each of said stations further include means for completing transmission of said transmission unit if said outbound channel is sensed as idle within a predetermined time period.

52. A network as in claim 49 wherein each of said stations includes means for detecting carrier on said outbound channel for a certain time period, means for transmitting a pilot signal if no carrier signal is detected, means for detecting the beginning of carrier on said inbound channel and means responsive to the detection of said beginning of carrier signal for terminating transmission of said pilot signal.

53. A local area communication network comprising a communication bus having an inbound channel and an outbound channel, a plurality of stations S1-SN located along and connected to said communication bus where each of said stations have a respective index corresponding to the location of its connection to said bus, each of said stations including means for transmitting and receiving carrier signals having information data packets on said communication bus in a round robin format wherein said data packets are of a different type, means for integrating said different types of packets on said communication bus such that the data packets are propagated on said inbound channel in the same direction with respect to each of said stations as on said outbound channel thereby achieving a round robin format, and means for controlling the transmission and reception of said data packets, said control means including means for sensing a first carrier signal transmitted by one of said stations having a lower index on said outbound channel, means for detecting the end of said first carrier signal and means responsive thereto for transmitting a second carrier signal having a data packet on said outbound channel, and means for aborting transmission of said second carrier signal if a third carrier signal is sensed within a predetermined period of time t_d where t_d is the time for a station to detect the presence or absence of a carrier signal on said bus.

54. A local area communication network comprising a communication bus having an inbound channel and an outbound channel, a plurality of stations S1-SN located along and connected to said communication bus where each of said stations have a respective index corresponding to the location of its connected to said bus, each of said stations including a transmitting tap on said outbound channel and means for transmitting and receiving carrier signals having information data packets on said communication bus in a round robin format such that said data packets are propagated past each of said stations on said inbound channel in the same direction with respect to said stations on said outbound channel thereby achieving said round robin format, means for controlling the transmission and reception of said data packets, said control means including means for sensing a first carrier signal transmitted by one of said stations having a lower index on said outbound channel, means for detecting the end of said first carrier signal and means responsive thereto for transmitting a second carrier signal having a data packet on said outbound channel, and means for aborting transmission of said second carrier signal if a third carrier signal is sensed within a predetermined period of time t_d where t_d is the time for a station to detect the presence or absence of a carrier signal on said bus.

55. A network as in claim 54 wherein each of said stations includes means for sensing carrier on the upstream side of said transmitting tap.

56. A network as in claim 54 wherein each of stations include means for forcing undirectionality on said communication bus with respect to said connected stations.

57. A network as in claim 56 wherein such stations include means for sensing carrier on the upstream side of the first of said enforcing means.

58. A network as in claim 56 wherein each of said stations includes means for sensing carrier on said bus other than the respective transmission by said station, and means for subtracting the transmitted signal of said respective station.

59. A network as in claim 55 wherein each of said stations includes at least two taps on said communication bus separated by a predetermined distance for forcing undirectionality on said communication bus.

60. A network as in claim 59 wherein said enforcing means includes delay means for delaying said data packets and means for negating the delayed transmitted signal.

61. A network as in claim 60 wherein each of said stations includes means for sensing a carrier signal upstream with respect to the transmission direction.

62. A network as in claim 54 including directional coupler means for coupling said data packets to said communication bus.

63. A network as in claim 54 wherein said communication bus is bidirectional and wherein each of said stations includes means for sensing carrier on said communication bus.

64. A local area communication network comprising a communication bus having an outbound channel, a plurality of stations S1-SN located along and connected to said communication bus where each of said stations have a respective index corresponding to the location of its connection to said bus, each of said stations including a transmitting tap connected to said outbound channel, transmit means for transmitting carrier signals having data packets in a round robin format on said outbound channel past each station connected to said outbound channel having a higher index than the respective transmit station, means for sensing a carrier signal on the upstream side of said transmitting tap, means for detecting the end of said first carrier signal and means responsive thereto for transmitting a second carrier signal having a data packet on said outbound channel, and means for aborting transmission of said second carrier signal is sensed within a predetermined period of time t_d where t_d is the time for a station to detect the presence or absence of a carrier signal on said bus, thereby achieving said round robin format.

65. A local area communication network comprising a communication bus, a plurality of stations S1-SN located along and connected to said communication bus where each of said stations have a respective index corresponding to the location of its connection to said bus such that said carrier signals having data packets are transmitted from said stations on said communication bus in a round robin format, each of said stations including, for each round of said round robin format,

transmit means for transmitting carrier signals having data packets on said communication bus past each station connected to said communication bus having a higher index than the respective transmit station,

receive means connected to said communication channel such that data packets are propagated past each of said receive means in the same order as the respective indices of said stations connected to said communication bus thereby achieving said round robin format,

means for controlling the transmission and reception of said data packets, said control means including

means for sensing a first carrier signal transmitted in a certain direction by one of said stations having a lower index on said communication bus, and

means for detecting the end of said first carrier signal and means responsive thereto for transmitting a second carrier signal having a data packet on said communication bus.

66. A local area communication network as in claim 65 wherein said control means includes means for aborting transmission of said second carrier signal if a third carrier signal is sensed within a predetermined period of time t_d where t_d is the time for a station to detect the presence or absence of a carrier signal on said bus.