Vertical roaming in wireless networks through improved quality of service measures

• US 20050250508A1
• Filed: 06/27/2005
• Published: 11/10/2005
• Est. Priority Date: 02/28/2003
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Guo, Zihua, Zhang, Qian, Zhu, Wenwu, Yao, Richard
• Granted Patent: US 7,154,869 B2
• Time in Patent Office: Days
• US Class Current: 455/452.100
• CPC Class Codes: H04W 36/0088 Scheduling hand-off measurements
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 36/1446 wherein at least one of the networks is unlicensed
• CPC Class Codes: H04W 36/22 for handling the traffic

Abstract

A system and method for improved vertical handoff between different types of wireless network. Network allocation vector occupation and packet collision probability are used as quality of service measures, enabling vertical handoffs to be delayed until actually beneficial to quality of service. Improved wireless network cell boundary detection in vertical handoff scenarios is achieved with a Fourier-based technique in conjunction with an adaptively determined minimum operating signal strength threshold. Improved wireless network cell boundary detection enables vertical handoffs from high quality of service networks to be delayed as long as possible. Together, practical wireless network quality of service measures and improved detection of wireless network cell boundaries in vertical handoff scenarios reduce the rate of unnecessary vertical handoff resulting in higher overall quality of service experienced by a mobile computing device roaming between wireless network types.

Claims

2. A method comprising:

sampling a network allocation vector of a wireless network for a period of time;

calculating a network allocation vector occupation comprising calculating the ratio of the amount of time that the network allocation vector is busy during the time period to the total amount of time during the time period; and

calculating a wireless network quality of service measure as a linear function of the network allocation vector occupation.

3. The method according to claim 2, wherein a low network allocation vector occupation corresponds to a high wireless network quality of service measure and a high network allocation vector occupation corresponds to a low wireless network quality of service measure.

4. The method according to claim 3, wherein the wireless network quality of service measure comprises an estimated residual bandwidth in the wireless network.

5. The method according to claim 4, wherein a high level of network allocation vector occupation corresponds to zero estimated residual bandwidth in the wireless network.

31. A computer-readable medium having instructions stored thereon for execution by a computing device to perform the method of claim 2.

32. The computer-readable medium of claim 31, wherein a low network allocation vector occupation corresponds to a high wireless network quality of service measure and a high network allocation vector occupation corresponds to a low wireless network quality of service measure.

33. The computer-readable medium of claim 32, wherein the wireless network quality of service measure comprises an estimated residual bandwidth in the wireless network.

34. The computer-readable medium of claim 33, wherein a high level of network allocation vector occupation corresponds to zero estimated residual bandwidth in the wireless network.

6. (canceled)

7. A method comprising:

sampling a network allocation vector of a wireless network for a period of time;

calculating a network allocation vector occupation comprising calculating the ratio of the amount of time that the network allocation vector is busy during the time period to the total amount of time during the time period; and

calculating a wireless network quality of service measure as a function of the network allocation vector occupation, wherein calculating the wireless network quality of service measure as a function of network allocation vector occupation comprises looking-up the wireless network quality of service measure in a network allocation vector occupation to wireless network quality of service measure look-up table.

28. The method according to claim 7, wherein a low network allocation vector occupation corresponds to a high wireless network quality of service measure and a high network allocation vector occupation corresponds to a low wireless network quality of service measure.

29. The method according to claim 28, wherein the wireless network quality of service measure comprises an estimated residual bandwidth in the wireless network.

30. The method according to claim 29, wherein a high level of network allocation vector occupation corresponds to zero estimated residual bandwidth in the wireless network.

41. A computer-readable medium having thereon a data structure corresponding to the look-up table of claim 7, wherein the data structure comprises the following fields:

network allocation vector occupation; and

estimated residual bandwidth.

42. The look-up table data structure of claim 41 further comprising an average data packet transmission size field.

8-27. -27. (canceled)

35. A computing device comprising:

at least one wireless network interface;

a network device interface operatively connected to the at least one wireless network interface; and

a vertical roaming manager comprising;

a multi-network manager configured to, at least;

monitor the at least one wireless network interface with the network device interface, the monitoring comprising sampling a network allocation vector for a period of time; and

generate at least one quality of service measure; and

a policy manager configured to, at least, receive the at least one quality of service measure from the multi-network manager.

36. The computing device of claim 35, wherein the multi-network manager is further configured to generate network status notifications and the policy manager is further configured to receive the network status notifications from the multi-network manager.

37. The computing device of claim 35, wherein the multi-network manager is further configured to calculate a network allocation vector occupation comprising calculating the ratio of the amount of time that the network allocation vector is busy during the time period to the total amount of time during the time period.

38. The computing device of claim 37, wherein the at least one quality of service measure comprises a linear function of the network allocation vector occupation.

39-1. The system of claim 39, wherein the at least one quality of service measure comprises an estimated residual bandwidth.