Data communications method and system using buffer size to calculate transmission rate for congestion control

• US 20050021830A1
• Filed: 09/13/2002
• Published: 01/27/2005
• Est. Priority Date: 09/21/2001
• Status: Abandoned Application

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Urzaiz, Eduardo, Walker, Mathew D
• Application Number:
  US10/488,345
• Publication Number:
  US 20050021830A1
• Time in Patent Office: Days
• US Class Current: 709/234
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/263 Rate modification at the source after receiving feedback
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes

Abstract

A data transmission method and system is disclosed in which one or more data streams are transmitted at respective transmission rates which are controlled to prevent data buffers in the receiver from overflowing. In some embodiments feedback data concerning the state of each buffer in a receiving client is received at the transmitting server, and used to adapt the sending rates to achieve the effect. Information indicative of the data decode rates or the fill extent of each buffer is communicated to the server as the feedback data. In other embodiments the server makes an open-loop estimate of the remaining space in the buffer, and controls the transmission rate accordingly. A data receiving method and system adapted to receive the data streams is also disclosed.

Claims

1. A method of data transmission across a network, comprising the steps of:

transmitting data onto the network for transmission to a receiver in the form of a data stream at a data transmission rate;

determining at least one or more characteristics of a data buffer in the receiver in which the received data is stored; and

controlling the data transmission rate of the data stream in response to the determined one or more characteristics in order to prevent the data buffer in the receiver from overflowing.

2. A method according to claim 1, wherein the determining step further comprises the steps of:

monitoring the amount of data already transmitted to the receiver in the data stream;

storing one or more parameters relating to the receiver buffer; and

estimating the one or more characteristics on the basis of the monitored data and the stored parameters;

wherein the estimating step is performed in an open-loop manner without repeated feedback from the receiver indicative of the one or more characteristics of the receiver data buffer.

3. A method according to claim 1, wherein the determining step further comprises the steps of:

receiving feedback data from the receiver indicative of the one or more characteristics of the receiver data buffer;

wherein the controlling step controls the data transmission rate in response to the received feedback data.

4. A method according to claim 1, wherein the one or more characteristics include at least the decoding rate of the transmitted data in the stream received at the receiver;

and the transmission rate of the data stream is further controlled as a function of at least the receiver decoding rate.

5. A method according to claim 1, wherein the one or more characteristics include information indicative of the remaining capacity of the buffer.

6. A method according to claim 1, and further comprising calculating a maximum transmission rate at which the data stream should be transmitted, the controlling step being further arranged to control the transmission bit-rate so as to be within the calculated maximum bit-rate.

7. A method according to claim 6 wherein the maximum transmission rate is calculated to give an average thoughput of data over the network similar to that obtained using Transport Control Protocol (TCP).

8. A method according to claim 6, wherein the calculating step further comprises the steps of:

receiving feedback data from the receiver indicative of one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value at the receiver; and

calculating the maximum transmission rate as a function of one or more of the received values indicated by the feedback data;

wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to the receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to the receiver which is lost; and

the receiving rate value is the number of bits received in the round trip-time.

9. A method according to claim 8, wherein the maximum transmission rate is calculated In accordance with:

10. A method according to claim 1, and further comprising the steps of transmitting a plurality of data streams onto the network for transmission to one or more receivers, each at a respective data transmission rate;

determining for each stream at least the one or more characteristics of respective data buffers in which the received data In each stream is stored; and

controlling the respective data transmission rates of each stream in response to the received feedback data in order to prevent the data buffers from overflowing.

11. A method according to claim 10 and further comprising calculating a maximum transmission rate at which the data stream should be transmitted, the controlling step being further arranged to control the transmission bit-rate so as to be within the calculated maximum bit-rate, wherein for two streams transmitted to the same receiver, the respective data transmission rates for each stream are controlled in accordance with the following equations:

12. A method of generating one or more data streams on a network comprising a method of data transmission according to claim 1.

24. A computer readable storage medium storing a computer program which when run on a computer controls the computer to perform a method according to claim 1.

25. A method of receiving data from a network, the data having been transmitted according to a transmission method as claimed in claim 3, the method comprising the steps of:

receiving a data stream at a data transmission rate;

passing the received data to a data buffer for buffering therein;

measuring at least one or more characteristics of the data buffer; and

transmitting the measured characteristics to a transmitter for use in calculating the transmission rate for the data stream transmitted therefrom.

26. A method according to claim 25, further comprising the step of:

decoding the data in the buffer at a decoding rate;

wherein the data decoding rate is transmitted to the transmitter as at least one of the measured characteristics.

27. A method according to claim 25, wherein the one or more characteristics Include information indicative of the remaining capacity of the buffer.

28. A method according to claim 25, and further comprising calculating one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value, and transmitting the calculated values back to the transmitter;

wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to a receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to a receiver which is lost; and

the receiving rate value is the number of bits received by the receiver in the round trip time.

29. A method according to claim 28, wherein the loss rate is calculated using a weighted filter of the n most recent loss intervals, being the output of data received between two loss events.

30. A system for receiving data from a network, the data having been transmitted according to a transmission method as claimed in claim 3, the method comprising the steps of:

data receiving means for receiving a data stream at a data transmission rate;

data bus means for passing the received data to a data buffer for buffering therein;

buffer monitoring means for measuring at least one or more characteristics of the data buffer; and

data transmission means for transmitting the measured characteristics to a transmitter for use in calculating the transmission rate for the data stream transmitted therefrom.

31. A system according to claim 30, further comprising:

decoding means for decoding the data in the buffer at a decoding rate;

wherein the data decoding rate is transmitted to the transmitter as at least one of the measured characteristics.

32. A system according to claim 30, wherein the one or more characteristics include information indicative of the remaining capacity of the buffer.

33. A system according to claim 30, and further comprising calculating means for calculating one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value;

the data transmission means being further operable to transmit the calculated values back to the transmitter;

wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to a receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to a receiver which is lost; and

the receiving rate value is the number of bits received by the receiver In the round trip time.

34. A system according to claim 33, wherein the loss rate is calculated using a weighted filter of the n most recent loss intervals, being the output of data received between two loss events.

35. A computer-readable storage medium storing a computer program which when run on a computer controls the computer to perform the method of claim 25.

13. A system for data transmission across a network, comprising:

data stream transmission means for transmitting data onto the network for transmission to a receiver in a data stream at a data transmission bit rate;

characteristic determination means for determining at least one or more characteristics of a data buffer in the receiver in which the received data is stored; and

data stream controlling means for controlling the data transmission rate of the data stream in response to the determined characteristics in order to prevent the data buffer in the receiver from overflowing.

14. A system according to claim 13, wherein the characteristic determination means further comprise:

monitoring means for monitoring the amount of data already transmitted to the receiver in the data stream;

storage means for storing one or more parameters relating to the receiver buffer; and

estimating means for estimating the one or more characteristics on the basis of the monitored data and the stored parameters;

wherein the estimating means is operable to perform the estimate in an open-loop manner without repeated feedback from the receiver indicative of the one or more characteristics of the receiver data buffer.

15. A system according to claim 13, wherein the characteristic determination means further comprise:

data receiving means for receiving feedback data from the receiver indicative of the one or more characteristics of the receiver data buffer;

wherein the data stream controlling means is further operable to control the data transmission rate in response to the received feedback data.

16. A system according to claim 13, wherein the one or more characteristics include at least the decoding rate of the transmitted data in the stream received at the receiver;

and the data stream controlling means is further operable to control the transmission rate of the data stream as a function of at least the receiver decoding rate.

17. A system according to claim 13, wherein the one or more characteristics include information indicative of the remaining capacity of the buffer.

18. A system according to claim 13, and further comprising calculation means for calculating a maximum transmission rate at which the data stream should be transmitted, the data stream controlling means being further operable to control the transmission bit-rate so as to be within the calculated maximum bit-rate.

19. A system according to claim 18 wherein the calculation means is further operable to calculate the maximum transmission rate to give an average thoughput of data over the network similar to that obtained using Transport Control Protocol (TCP).

20. A system according to claim 18, wherein the data receiving means is further arranged to receive feedback data from the receiver indicative of one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value at the receiver;

and the calculation means is d=further arranged to calculate the maximum transmission rate as a function of one or more of the received values indicated by the feedback data;

wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to the receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to the receiver which is lost; and

the receiving rate value is the number of bits received in the round trip-time.

21. A system according to claim 20, wherein the maximum transmission rate is calculated in accordance with:

22. A system according to claim 13, comprising means for transmitting a plurality of data streams onto the network for transmission to one or more receivers, each at a respective data transmission rate;

means for determining for each stream at least the one or more characteristics of respective data buffers in which the received data in each stream is stored; and

means for controlling the respective data transmission rates of each stream in response to the received feedback data in order to prevent the data buffers from overflowing.

23. A system according to claim 22 and further comprising calculation means for calculating a maximum transmission rate at which the data stream should be transmitted, the data stream controlling means being further operable to control the transmission bit-rate so as to be within the calculated maximum bit-rate,

wherein for two streams transmitted to the same receiver, the respective data transmission rates for each stream are controlled in accordance with the following equations:

$\mathrm{sr\_str}<br><br>\_<br><br>1=\frac{y<br><br>\left(t<br><br>\text{\hspace{1em}<br><br>}<br><br>r-\mathrm{dr\_str2}\right)+x<br><br>\left(\mathrm{dr\_str1}\right)}{x+y}$$\mathrm{sr\_str}<br><br>\_<br><br>2=\frac{x<br><br>\left(t<br><br>\text{\hspace{1em}<br><br>}<br><br>r-\mathrm{dr\_str1}\right)+y<br><br>\left(\mathrm{dr\_str2}\right)}{x+y}$

wherein the variables relate to the following;

Sr_str_1;

sending rate of the first data stream;

Sr_str_2;

sending rate of the second data stream;

tr;

the sum of the calculated maximum transmission rates for each stream;

dr_str1;

the decoding rate at the receiver of the data in the first data stream;

dr_str2;

the decoding rate at the receiver of the data in the second data stream;

x;

a co-efficient of filling rate of a first buffer in the receiver which receives data from the first data stream; and

y;

a co-efficient of filling rate of a second buffer in the receiver which receives data from the second data stream.

36. A method of data transmission across a network, comprising the steps of:

calculating a total transmission rate for the transmission of data using a transmission rate formula;

transmitting data onto the network for transmission to a receiver in at least two separate data streams each at a respective data transmission bit rate; and

controlling the respective data transmission rates of at least a subset of the respective data streams to trade bit-rate between said streams;

wherein the sum of the respective transmission rates of each data stream is substantially equal to or less than the calculated total transmission rate.

37. A method according to claim 36, wherein the data transmission rates of the data streams are controlled so as to prevent data buffers in the receiver which receive the data in the data streams from overflowing.

38. A method according to claim 36 wherein the controlling steps further comprises the step of receiving feedback data from the receiver;

and

controlling the data transmission rates of at least a subset of the respective data streams in response to the received data.

39. A method according to claim 38 wherein the received feedback data is indicative of at least the decoding rate of the transmitted data in each stream received at the receiver;

and the transmission rates of the controlled data streams are further controlled as a function of at least the receiver decoding rates.

40. A method according to claim 39 wherein in the case of two data streams the respective transmission rates are controlled in accordance with the equations:

41. A method according to claim 36 wherein the total transmission rate is calculated to give an average thoughput of data over the network similar to that obtained using Transport Control Protocol (TCP).

42. A method according to claim 36 wherein the calculating step further comprises the steps of:

receiving feedback data from the receiver indicative of one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value at the receiver; and

calculating the total transmission rate as a function of one or more of the received values indicated by the feedback data;

wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to the receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to the receiver which is lost; and

the receiving rate value is the number of bits received in the round trip-time.

43. A method according to claim 42, wherein the total transmission rate is calculated in accordance with:

44. A method according to claim 36, wherein the data transmitted in at least a subset of two or more of the data streams is related.

45. A method according to claim 44, wherein at least one of said data streams contains real-time data of a first type, and one or more other of said data streams contains real-time data of a second type related to said data of said first type.

46. A method of generating a plurality of data streams on a network comprising a method of data transmission according to claim 36.

57. A computer readable storage medium storing a computer program which when run on a computer controls the computer to perform a method according to claim 36.

58. A method of receiving data from a network, the data having been transmitted according to a transmission method as claimed in claim 36 the method comprising the steps of:

receiving at least two separate data streams each at a respective data transmission rate;

passing the received data in each stream to a respective data buffer for buffering therein;

calculating one or more quantitative values indicative of one or more characteristics of the received data; and

transmitting the calculated quantitative values to a transmitter for use in calculating the total transmission rate for data transmitted therefrom.

59. A method according to claim 58, further comprising the step of:

decoding the data in each buffer at a respective decoding rate;

wherein the respective data decoding rates are transmitted to the transmitter as at least one of the calculated quantitative values.

60. A method according to claim 58 wherein the calculating step further comprises calculating one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value as the one or more quantitative values, wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to a receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to a receiver which is lost; and

the receiving rate value is the number of bits received by the receiver in the round trip time.

61. A method according to claim 60, wherein the loss event rate is calculated using a weighted filter of the n most recent loss intervals, being the output of data received between two loss events.

62. A system for receiving data from a network, the data having been transmitted according to a transmission method as claimed in claim 36, the system comprising:

data receiving means for receiving at least two separate data streams each at a respective data transmission rate;

at least two data buffers arranged to receive data therein from the respective received data streams;

calculation means for calculating one or more quantitative values indicative of one or more characteristics of the received data; and

data transmission means for transmitting the calculated quantitative values to a transmitter for use in calculating the total transmission rate for data transmitted therefrom.

63. A system according to claim 62, further comprising data decoding means for decoding the data in each buffer at a respective decoding rate;

wherein the respective data decoding rates are transmitted to the transmitter as at least one of the calculated quantitative values.

64. A system according to claim 62 wherein the calculation means are further operable to calculate one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value as the one or more quantitative values, wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to a receiver and back to the transmitter;

the loss rate is a measure of the amount of data transmitted to a receiver which is lost; and

the receiving rate value is the number of bits received by the receiver in the round-trip-time.

65. A system according to claim 64 wherein the calculation means further comprises a weighted filter means for calculating the loss event rate using a weighted filter of the n most recent loss intervals, being the amount of data received between two loss events.

66. A computer-readable storage medium storing a computer program which when run on a computer controls the computer to perform the method of claim 58.

47. A system for data transmission across a network, comprising:

transmission rate calculation means for calculating a total transmission rate for the transmission of data using a transmission rate formula;

data stream transmission means for transmitting data onto the network for transmission to a receiver in at least two separate data streams each at a respective data transmission bit rate; and

data stream controlling means for controlling the respective data transmission rates of at least a subset of the respective data streams to trade bit-rate between said streams;

wherein the data stream controlling means is further operable such that the sum of the respective transmission rates of each data stream is controlled to be substantially equal to or less than the calculated total transmission rate.

48. A system according to claim 47, wherein the data stream controlling means is further arranged to control the data transmission rates of the data streams so as to prevent data buffers in the receiver which receives the data in the data streams from overflowing.

49. A system according to claim 47 further comprising data receiving means for receiving feedback data from the receiver;

wherein the data stream controlling means is further arranged to control the data transmission rates of at least a subset of the respective data streams in response to the received data.

50. A system according to claim 49 wherein the received feedback data is indicative of at least the decoding rate of the transmitted data in each stream received at the receiver;

and the data stream controlling means is further arranged to control the transmission rates of the controlled data streams as a function of at least the receiver decoding rates.

51. A system according to claim 50 wherein in the case of two data streams the respective transmission rates are controlled in accordance with the equations:

52. A system according to claim 47 wherein the total transmission rate is calculated to give an average thoughput of data over the network similar to that obtained using Transport Control Protocol (TCP).

53. A system according to claim 47 further comprising:

data receiving means for receiving feedback data from the receiver indicative of one or more of a round trip time value (RTT), a loss rate value, and/or a receiving rate value at the receiver; and

wherein the transmission rate calculation means is further arranged to calculate the total transmission rate as a function of one or more of the received values indicated by the feedback data;

wherein the round trip time is a measure of the time it takes for data to travel from a transmitter to the receiver and back to the transmitter;

the loss rate value is a measure of the amount of data transmitted to the receiver which is lost; and

the receiving rate value is the number of bits received in the round trip-time.

54. A system according to claim 53 wherein the total transmission rate is calculated in accordance with:

55. A system according to claim 47 wherein the data transmitted in at least two or more of the data streams is related.

56. A system according to claim 55, wherein at least one of said data streams contains real-time data of a first type and one or more other of said data streams contains real-time data of a second type related to said data of said first type.