Method of seamlessly roaming between multiple wireless networks using a single wireless network adaptor

• US 20080069065A1
• Filed: 09/20/2006
• Published: 03/20/2008
• Est. Priority Date: 09/20/2006
• Status: Abandoned Application

• Current Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Original Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Inventors: Lo, Tun Han Felix, Wu, Wai Keung
• Application Number:
  US11/524,766
• Publication Number:
  US 20080069065A1
• Time in Patent Office: Days
• US Class Current: 370/340
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/22 for handling the traffic
• CPC Class Codes: H04W 36/36 by user or terminal equipment
• CPC Class Codes: H04W 76/20 Manipulation of established connections
• CPC Class Codes: H04W 92/18 between terminal devices

Abstract

A method of roaming between access points on the same or different wireless networks using a single wireless network interface adaptor. A device will establish a connection with a second wireless network access point while still connected with a first wireless network access point such that the device can concurrently communicate with both wireless access points. During and after connection with the second wireless network access point real-time IP data transfer is maintained with another network device by switching between the first and second access points for concurrently sending and receiving data packets via both access points using a switching strategy based at least in part on a number of the data packets to be send to each network access point. The method also determines when to roam, scans for candidate wireless network access points to connect to and selects the best access point for roaming based on selection criteria.

Claims

1. A method in a portable device having a single wireless network interface adaptor of roaming between access points on the same or different wireless networks while maintaining real-time IP data transfer with another device, the method comprising:

when connected with a first wireless network access point for real-time IP data transfer with another device, establishing a connection with a second wireless network access point such that the portable device can concurrently communicate with the first and second wireless access points for relocating the real-time IP data transfer to the second access point, and

switching between the first and second network access points for concurrently sending and receiving data packets via both access points using a switching strategy based at least in part on a number of the data packets to be send to each network access point.

2. The method of claim 1 wherein the switching strategy is based on a weighting scheme wherein the access point currently handling the real-time IP data transfer is allocated a first active time period and the other access point is allocated a second active time period shorter than the first active time period.

3. The method of claim 2 wherein the first active time period is between 60 and 100 milliseconds.

4. The method of claim 2 wherein the second active time period is between 10 and 40 milliseconds.

5. The method of claim 1 wherein the switching strategy is based at least in part on a number of packets buffered within the portable device for sending to each network access point.

6. The method of claim 5 wherein the switching strategy comprises switching to one of the network access points after a first switching time when there is a packet buffered for sending to that access point, and when no packet is buffered for sending to that access point switching to that access point after a second switching time that is longer than the first switching time.

7. The method of claim 6 wherein the first switching time is between 10 and 40 milliseconds.

8. The method of claim 6 wherein the second switching time is between 60 and 100 milliseconds.

9. The method of claim 1 wherein the switching strategy comprises before switching away from one of the network access points sending a first message to that network access point indicating that the portable device wireless network interface adaptor has entered a power save mode, and after a switching time switching back to that network access point and sending a second message requesting that any packets buffered by that access point be sent.

10. The method of claim 9 wherein the switching time is based at least in part on packets buffered within the portable device for sending to that access point.

11. The method of claim 9 wherein the switching time comprises a first switching time and a second switching time longer than the first switching time, and wherein the switching strategy further comprises switching back to that network access point after the first switching time when there is a packet buffered in the portable device for sending to that access point, and when no packet is buffered in the portable device for sending to that access point switching back after the second switching time.

12. The method of claim 11 wherein the first switching time is between 10 and 40 milliseconds.

13. The method of claim 11 wherein the second switching time is between 60 and 100 milliseconds.

14. The method of claim 9 wherein the first message is an IEEE 802.11 power save message.

15. The method of claim 9 wherein the second message is an IEEE 802.11 standard poll message.

77. The method of claim 76 wherein if none of the located wireless access points fulfil the condition then selecting as the second wireless access point the access point having the highest signal strength that is also higher than the signal strength of the first access point and undertaking the method of any one of claims 1 to 15.

16. A method in a portable device having a single wireless network interface adaptor of roaming between access points on the same or different wireless networks while maintaining real-time IP data transfer with another device, the method comprising:

receiving a beacon signal from a first wireless network access point with which the portable device has established a first connection for real-time IP data transfer with the other device,

determining whether to search for a second wireless network access point with which to established a second connection based at least in part on a condition, and

when it is determined to search for a second wireless network access point, probing each wireless radio channel separately to locate wireless network access points on the probed channel and between each probe allowing the portable device to send and receive packets to/from the other device.

17. The method of claim 16 wherein the condition includes at least the beacon signal strength falling below a threshold.

18. The method of claim 17 wherein the threshold is −

80 dbm.

19. The method of claim 16 further comprising creating a list of located wireless network access points on each channel and after all wireless radio channels have been probed selecting from the list a second wireless network access point with which to established a second connection based at least in part on a second condition.

20. The method of claim 19 wherein the second condition is the access point having the highest signal strength that is also higher than the beacon signal strength of the first access point.

21. The method of claim 16 further comprising establishing a connection with the second wireless network access point such that the portable device can concurrently communicate with the first and second access points for relocating a real-time IP data transfer path from the first access point to the second access point, and when the real-time IP data path is relocated disconnecting from the first wireless network access point.

22. The method of claim 21 further comprising increasing the size of a data buffer in the portable device while the device is concurrently communicating with the first and second wireless access points.

23. The method of claim 21 further comprising switching between the first and second network access points using a dynamic switching strategy.

24. The method of claim 23 wherein the switching strategy is based at least in part on the number of packets to be send via each network access point.

25. The method of claim 23 wherein the switching strategy is based at least in part on the time spent on one of the access points after a packet is to be send via the other access point.

26. The method of claim 24 wherein the switching strategy comprises switching to the other access points after a first switching time when there is a packet buffered for sending to the other access point, and when no packet is buffered for sending to the other access point switching to the other access point after a second switching time that is longer than the first switching time.

27. The method of claim 26 wherein the first switching time is between 10 and 40 milliseconds.

28. The method of claim 26 wherein the second switching time is between 60 and 100 milliseconds.

29. A method in a portable device having a single wireless network interface adaptor of roaming between access points on the same or different wireless networks while maintaining real-time IP data transfer with another device, the method comprising:

providing a data buffer for storing received data during playback in the portable device and while connected with a first wireless network access point for real-time IP data transfer with another device;

making a decision to switch to a second wireless network access point for relocating the real-time IP data transfer to the second access point,

increasing a size of the buffer,

establishing a connection with the second wireless network access point such that the portable device can concurrently communicate with the first and second wireless access points,

switching between the first and second network access points for concurrently sending and receiving packets via both access points using a switching strategy based at least in part on a number of packets to be send to each access point,

relocating the real-time IP data transfer to the second access point, and

after the real-time IP data transfer is relocated to the second access point, disconnecting from the first wireless network access point and decreasing the size of the buffer.

30. The method of claim 29 further comprising, when increasing the size of the buffer also decreasing a speed of playback of the data, and when decreasing the size of the buffer also increasing the speed of playback of the data.

31. The method of claim 29 wherein making the decision to switch to the second wireless network access point comprises:

receiving a beacon signal from a first wireless network access point,

determining whether to search for a second wireless network access point with which to established a second connection based at least in part on the beacon signal strength,

when it is determined to search for a second wireless network access point, probing each wireless radio channel separately to locate wireless network access points on the probed channel and between each probe allowing the portable device to send and receive packets to/from the other device,

creating a list of located wireless network access points on each channel, and

selecting from the list a second wireless network access point with which to established a second connection based at least in part on which located access point has the highest signal strength that is also higher than the beacon signal strength of the first access point.

32. The method of claim 29 wherein the switching strategy comprises switching to one of the network access points after a first switching time when there is a packet buffered for sending to that access point, and when no packet is buffered for sending to that access point switching to that access point after a second switching time that longer than the first switching time.

33. The method of claim 32 wherein the first switching time is between 10 and 40 milliseconds.

34. The method of claim 32 wherein the second switching time is between 60 and 100 milliseconds.

35. A method in a portable device having a single wireless network adapter of simultaneously associating with two wireless network access points, the method comprising:

providing in the device an adapter driver for controlling the wireless network adapter,

maintaining a list of association parameters for at least a first and a second wireless network access point with which the portable device is associated,

determining a switching schedule for switching between the first and second wireless network access points, and

switching between the first and second network access points according to the schedule, wherein a power save message is sent to one of the first or second network access points and association parameters from the list are loaded to the adapter driver for connection with the other one of the first or second network access points.

36. A portable device for engaging in real-time IP data transfer with another device over a network, the device having a single wireless network interface adaptor and at least one electronic storage medium having machine readable instructions thereon permitting the device to perform steps of:

connecting with a first wireless network access point for real-time IP data transfer with another device,

establishing a connection with a second wireless network access point such that the portable device can concurrently communicate with the first and second wireless access points for relocating the real-time IP data transfer to the second access point, and

switching between the first and second network access points for concurrently sending and receiving data packets via both access points using a switching strategy based at least in part on a number of the data packets to be send to each network access point.

37. The portable device of claim 36 wherein the switching strategy is based on a weighting scheme wherein the access point currently handling the real-time IP data transfer is allocated a first active time period and the other access point is allocated a second active time period shorter than the first active time period.

38. The portable device of claim 37 wherein the first active time period is between 60 and 100 milliseconds.

39. The portable device of claim 37 wherein the second active time period is between 10 and 40 milliseconds.

40. The portable device of claim 36 wherein the switching strategy is based at least in part on a number of packets buffered within the portable device for sending to each network access point.

41. The portable device of claim 40 wherein the switching strategy comprises switching to one of the network access points after a first switching time when there is a packet buffered for sending to that access point, and when no packet is buffered for sending to that access point switching to that access point after a second switching time that is longer than the first switching time.

42. The portable device of claim 41 wherein the first switching time is between 10 and 40 milliseconds.

43. The portable device of claim 41 wherein the second switching time is between 60 and 100 milliseconds.

44. The portable device of claim 36 wherein the switching strategy comprises before switching away from one of the network access points sending a first message to that network access point indicating that the wireless network interface adaptor has entered a power save mode, and after a switching time switching back to that network access point and sending a second message requesting that any packets buffered by that access point be sent.

45. The portable device of claim 44 wherein the switching time is based at least in part on packets buffered within the portable device for sending to that access point.

46. The portable device of claim 44 wherein the switching time comprises a first switching time and a second switching time longer than the first switching time, and wherein the switching strategy further comprises switching back to that network access point after the first switching time when there is a packet buffered in the portable device for sending to that access point, and when no packet is buffered in the portable device for sending to that access point switching back after the second switching time.

47. The portable device of claim 46 wherein the first switching time is between 10 and 40 milliseconds.

48. The portable device of claim 46 wherein the second switching time is between 60 and 100 milliseconds.

49. The portable device of claim 44 wherein the first message is an IEEE 802.11 power save message.

50. The portable device of claim 44 wherein the second message is an IEEE 802.11 standard poll message.

51. The portable device of claim 36 which is a wireless IP phone.

52. A portable device for engaging in real-time IP data transfer with another device over a network, the device having a single wireless network interface adaptor and at least one electronic storage medium having machine readable instructions thereon permitting the device to perform steps of:

receiving a beacon signal from a first wireless network access point with which the portable device has established a first connection for real-time IP data transfer with the other device,

determining whether to search for a second wireless network access point with which to established a second connection based at least in part on a condition, and

when it is determined to search for a second wireless network access point, probing each wireless radio channel separately to locate wireless network access points on the probed channel and between each probe allowing the portable device to send and receive packets to/from the other device.

53. The portable device of claim 52 wherein the condition includes at least the beacon signal strength falling below a threshold.

54. The portable device of claim 53 wherein the threshold is −

80 dbm.

55. The portable device of claim 52 further comprising machine readable instructions permitting the device to perform steps of creating a list of located wireless network access points on each channel and after all wireless radio channels have been probed selecting from the list a second wireless network access point with which to established a second connection based at least in part on a second condition.

56. The portable device of claim 55 wherein the second condition is the access point having the highest signal strength that is also higher than the beacon signal strength of the first access point.

57. The portable device of claim 52 further comprising machine readable instructions permitting the device to perform steps of establishing a connection with the second wireless network access point such that the portable device can concurrently communicate with the first and second access points for relocating a real-time IP data transfer path from the first access point to the second access point, and when the real-time IP data path is relocated disconnecting from the first wireless network access point.

58. The portable device of claim 57 further comprising a data buffer and machine readable instructions permitting the device to perform steps of increasing the size of the data buffer while the device is concurrently communicating with the first and second wireless access points.

59. The portable device of claim 57 further comprising machine readable instructions permitting the device to perform steps of switching between the first and second network access points using a dynamic switching strategy.

60. The portable device of claim 59 wherein the switching strategy is based at least in part on the number of packets to be send via each network access point.

61. The portable device of claim 59 wherein the switching strategy is based at least in part on the time spent on one of the access points after a packet is to be send via the other access point.

62. The portable device of claim 60 wherein the switching strategy comprises switching to the other access points after a first switching time when there is a packet buffered for sending to the other access point, and when no packet is buffered for sending to the other access point switching to the other access point after a second switching time that is longer than the first switching time.

63. The portable device of claim 62 wherein the first switching time is between 10 and 40 milliseconds.

64. The portable device of claim 62 wherein the second switching time is between 60 and 100 milliseconds.

65. The portable device of claim 52 which is a wireless IP phone.

66. A portable device for engaging in real-time IP data transfer with another device over a network, the device having a single wireless network interface adaptor, and at least one electronic storage medium having a data buffer for storing received data during playback and machine readable instructions thereon permitting the device to perform steps of:

connecting with a first wireless network access point for real-time IP data transfer with another device

making a decision to roam to a second wireless network access point for relocating the real-time IP data transfer to the second access point,

increasing a size of the buffer,

establishing a connection with the second wireless network access point such that the portable device can concurrently communicate with the first and second wireless access points,

switching between the first and second network access points for concurrently sending and receiving packets via both access points using a switching strategy based at least in part on a number of packets to be send to each access point,

relocating the real-time IP data transfer to the second access point, and

after the real-time IP data transfer is relocated to the second access point, disconnecting from the first wireless network access point and decreasing the size of the buffer.

67. The portable device of claim 66 further comprising machine readable instructions permitting the device to perform steps of decreasing a speed of playback of the data when increasing the size of the buffer, and increasing the speed of playback of the data when decreasing the size of the buffer.

68. The portable device of claim 66 wherein making the decision to roam to the second wireless network access point comprises:

receiving a beacon signal from a first wireless network access point,

determining whether to search for a second wireless network access point with which to established a second connection based at least in part on the beacon signal strength,

when it is determined to search for a second wireless network access point, probing each wireless radio channel separately to locate wireless network access points on the probed channel and between each probe allowing the portable device to send and receive packets to/from the other device,

creating a list of located wireless network access points on each channel, and

selecting from the list a second wireless network access point with which to established a second connection based at least in part on which located access point has the highest signal strength that is also higher than the beacon signal strength of the first access point.

69. The portable device of claim 66 wherein the switching strategy comprises switching to one of the network access points after a first switching time when there is a packet buffered for sending to that access point, and when no packet is buffered for sending to that access point switching to that access point after a second switching time that longer than the first switching time.

70. The portable device of claim 69 wherein the first switching time is between 10 and 40 milliseconds.

71. The portable device of claim 69 wherein the second switching time is between 60 and 100 milliseconds.

72. The portable device of claim 66 which is a wireless IP phone.

73. A method in a portable device having a single wireless network interface adaptor of roaming between access points on the same or different wireless networks while maintaining real-time IP data transfer with another device, the method comprising:

when connected with a first wireless access point on a first wireless network scanning wireless radio channels to locate a second wireless access point with which to established a second connection, and

upon locating a second wireless access point determining if the second wireless access point is on the first wireless network or another wireless network, said determining step comprising sending a digital communications packet to the second wireless access point and waiting for a response to the sent communications packet from the second wireless access point, wherein the packet has as its immediate destination the first wireless access point and as its final destination the second wireless access point.

74. The method of claim 73 wherein, if a response to the sent communications packet is received from the second wireless access point then roaming from the first wireless access point to the second wireless access point.

75. The method of claim 73 further comprising creating a list of located wireless access points on each channel and after all wireless radio channels have been scanned determining for each located wireless access point if that wireless access point is on the first wireless network or another wireless network, and selecting from the list the second wireless access point with which to established a second connection based at least in part on a condition.

76. The method of claim 75 wherein the condition is an access point on the first wireless network and having the highest signal strength that is also higher than the signal strength of the first access point.