Source: http://patents.com/us-9906972.html
Timestamp: 2018-08-15 03:57:39
Document Index: 479504099

Matched Legal Cases: ['application No. 200780039978', 'application No. 200780039978', 'application No. 200780039978', 'application No. 07816083', 'application No. 07816083', 'application No. 2', 'Application No. 2664', 'Application No. 60']

US Patent # 9,906,972. Measure of quality of link between mobile station and base station - Patents.com
United States Patent 9,906,972
Montemurro , et al. February 27, 2018
A mobile station associated with a base station determines a measure of the quality of a communication link between the mobile station and the base station. The measure is determined by comparing either i) an expected data rate for communications over the link and an actual data rate of communications over the link, wherein the expected data rate takes into account radio frequency (RF) power levels of signals received at the mobile station over the link, or ii) an expected RF power level for communications over the link and RF power levels of signals received at the mobile station over the link, wherein the expected RF power level takes into account the actual data rate of communications over the link. This measure of the quality of the link may be a factor in triggering the mobile station to initiate a handoff.
Montemurro; Michael Peter (Toronto, CA), Durand; Roger Paul (Amherst, NH)
Family ID: 1000003144671
14/960,920
US 20160088505 A1 Mar 24, 2016
14134923 Dec 19, 2013 9210640
13348517 Dec 31, 2013 8620325
11924341 Feb 28, 2012 8126454
60863254 Oct 27, 2006
Current CPC Class: H04W 24/08 (20130101); H04W 36/30 (20130101); H04L 43/0847 (20130101)
Current International Class: H04W 24/08 (20090101); H04W 36/30 (20090101); H04L 12/26 (20060101)
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231987 Apr 2002 WO
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This application is a continuation of U.S. patent application Ser. No. 14/134,923, filed on Dec. 19, 2013, which is a continuation of U.S. patent application Ser. No. 13/348,517, filed on Jan. 11, 2012 and issued as U.S. Pat. No. 8,620,325 on Dec. 31, 2013, which is a continuation of U.S. patent application Ser. No. 11/924,341, filed on Oct. 25, 2007, and issued as U.S. Pat. No. 8,126,454 on Feb. 28, 2012, which claims priority to U.S. Provisional Application No. 60/863,254, filed on Oct. 27, 2006, the entire contents of all are hereby incorporated by reference.
1. A method in a mobile station, the method comprising: determining an expected data rate for communications over a link between an access point and the mobile station and an actual data rate of communications over the link, wherein the expected data rate is determined based on radio frequency power levels of signals received at the mobile station over the link; comparing the expected data rate to the actual data rate; and using a result of the comparing as a factor in determining whether to initiate a handoff from the access point.
2. The method of claim 1, further comprising initiating the handoff from the access point based, at least in part, on the result of the comparing.
3. The method of claim 1, further comprising selecting a different access point as a target of the handoff based on a determination that a link with the different access point experiences less interference than the link between the mobile station and the access point.
4. The method of claim 1, further comprising determining based, at least in part, on the result of the comparing whether to transfer to the link a communication session currently being carried over a different link between the mobile station and another access point.
5. The method of claim 1, further comprising using signal strength measurements of the signals as an indication of the power levels.
6. The method of claim 1, further comprising using received channel power indicator measurements of the signals as an indication of the power levels.
7. The method of claim 1, further comprising selecting a network based, at least in part, on the result of the comparing.
8. A mobile station comprising: a wireless local area network communication interface through which the mobile station is able to communicate with an access point over a communication link; and one or more processors coupled to the wireless local area network communication interface and configured to: determine an expected data rate for communications over a link between the access point and the mobile station and an actual data rate of communications over the link, wherein the expected data rate is determined based on radio frequency power levels of signals received at the mobile station over the link; compare the expected data rate to the actual data rate; and use a result of the comparing as a factor in determining whether to initiate a handoff from the access point.
9. The mobile station of claim 8, the one or more processors further configured to initiate the handoff from the access point based, at least in part, on the result of the comparing.
10. The mobile station of claim 8, the one or more processors further configured to select a different access point as a target of the handoff based on a determination that a link with the different access point experiences less interference than the link between the mobile station and the access point.
11. The mobile station of claim 8, the one or more processors further configured to determine based, at least in part, on the result of the comparing whether to transfer to the link a communication session currently being carried over a different link between the mobile station and another access point.
12. The mobile station of claim 8, the one or more processors further configured to use signal strength measurements of the signals as an indication of the power levels.
13. The mobile station of claim 8, the one or more processors further configured to use received channel power indicator measurements of the signals as an indication of the power levels.
14. The mobile station of claim 8, the one or more processors further configured to select a network based, at least in part, on the result of the comparing.
15. A non-transitory computer readable medium storing instructions to cause a processor to perform operations comprising: determining an expected data rate for communications over a link between an access point and a mobile station and an actual data rate of communications over the link, wherein the expected data rate is determined based on radio frequency power levels of signals received at the mobile station over the link; comparing the expected data rate to the actual data rate; and using a result of the comparing as a factor in determining whether to initiate a handoff from the access point.
16. The computer readable medium of claim 15, the operations further comprising initiating the handoff from the access point based, at least in part, on the result of the comparing.
17. The computer readable medium of claim 15, the operations further comprising selecting a different access point as a target of the handoff based on a determination that a link with the different access point experiences less interference than the link between the mobile station and the access point.
18. The computer readable medium of claim 15, the operations further comprising determining based, at least in part, on the result of the comparing whether to transfer to the link a communication session currently being carried over a different link between the mobile station and another access point.
19. The computer readable medium of claim 15, the operations further comprising using signal strength measurements of the signals as an indication of the power levels.
20. The computer readable medium of claim 15, the operations further comprising selecting a network based, at least in part, on the result of the comparing.
As used herein, the term "handoff" is intended to include transfers between networks of the same type and networks of different types, and also to include transfers while a mobile station is in idle mode and transfers while a mobile station is in an active communication session such as a telephone call.
While many different schemes for triggering handoffs have been proposed, most schemes are directed at achieving one or more of the following general objectives: a) A mobile station should look to perform a handoff before it loses its WLAN connection; b) A handoff ought to take a minimum amount of time; and c) A handoff from a WLAN to a cellular network ought to be completed while the mobile station is still in an area of overlapping coverage between the WLAN and the cellular network.
Some wireless local area networks (WLANs) operate in an unlicensed frequency band and may therefore be subject to interference from non-WLAN devices operating in the same frequency band. For example, IEEE 802.11 WLANs, also known as "Wi-Fi networks", operate in the unlicensed 2.4 GHz and 5 GHz bands. The 2.4 GHz band is also used by cordless telephones, microwave ovens, baby monitors, Bluetooth.RTM. devices, ZigBee.TM. devices and WirelessUSB.TM. devices. The lower portion of the 5 GHz band is used by satellite to ground links, and the middle portion of the 5 GHz band is used by RADAR devices. There is a general assumption among persons of ordinary skill in the art that since the cellular spectrum is licensed, it is relatively clean of interference.
In the following description and claims, the term "base station" is intended to encompass an access point (AP) of a WLAN (e.g. a Wi-Fi network), a base station of a WWAN (e.g. a cellular network), and a Head End of a WMAN (e.g. a WiMAX network).
At 304, link quality measurement module 206 may determine an expected data rate based on the RF power level measured at 302. A look-up table may be employed to determine the expected data rate. The look-up table may be based on field measured data, laboratory measured data, expected receiver performance, manufacturing calibration data, or any combination thereof
An example of such a look-up table for IEEE 802.11b devices follows, assuming a data rate algorithm derives a packet error rate of <1 in 1000 and the radio noise floor plus other radio implementation errors equal -95 dBm:
TABLE-US-00001 Received Power Level Expected Data Rate -83 dBm or higher 11 Mbps -86 dBm to -84 dBm 5.5 Mbps -89 dBm to -87 dBm 2 Mbps -90 dBm or lower 1 Mbps
An example of such a look-up table for IEEE 802.11g/a devices follows, assuming a data rate algorithm derives a packet error rate of <1 in 1000 and the radio noise floor plus other radio implementation errors equal -95 dBm:
TABLE-US-00002 Received Power Level Expected Data Rate -68 dBm or higher 54 Mbps -72 dBm to -69 dBm 48 Mbps -76 dBm to -73 dBm 36 Mbps -80 dBm to -77 dBm 24 Mbps -83 dBm to -81 dBm 18 Mbps -85 dBm to -84 dBm 12 Mbps -87 dBm to -86 dBm 9 Mbps -88 dBm or lower 6 Mbps
If the actual data rate is within x "steps" of the expected data rate on the scale of allowable data rates, as checked at 402, then the quality of the link is determined at 404 to be "high". If the actual data rate is y or more "steps" below the expected data rate on the scale of allowable data rates, as checked at 406, then the quality of the link is determined at 408 to be "low". If neither of these conditions is met, then the quality of the link is determined at 410 to be "medium". The values of x and y will depend upon the total number of allowable data rates and on how the abstraction is to be handled.
For example, for IEEE 802.11b devices, x may be set to zero, and y may be set to two. If the expected data rate (based on the RF power levels of the received signals) is 11 Mbps and the actual data rate is 2 Mbps or 1 Mbps, then the quality of the link is "low".
In another example, for IEEE 802.11g/a devices, x may be set to one, and y may be set to three. If the expected data rate (based on the RF power levels of the received signals) is 48 Mbps and the actual data rate is 18 Mbps or less, then the quality of the link is "low". If the actual data rate is 48 Mbps or 36 Mbps, then the quality of the link is "high". If the actual data rate is 24 Mbps, then the quality of the link is "medium".
As is known in the art, a mobile station and the base station with which it is associated or otherwise connected will derive or negotiate or adapt, or any combination thereof, to an actual data rate for communications over the link between the mobile station and the base station. At 504, link quality measurement module 206 may determine an expected RF power level based on the actual data rate. A look-up table may be employed to determine the expected RF power level. The look-up table may be based on field measured data, laboratory measured data, expected receiver performance, manufacturing calibration data, or any combination thereof
TABLE-US-00003 Actual Data Rate Expected Power Level 11 Mbps -83 dBm or higher 5.5 Mbps -86 dBm to -84 dBm 2 Mbps -89 dBm to -87 dBm 1 Mbps -90 dBm or lower
TABLE-US-00004 Actual Data Rate Expected Power Level 54 Mbps -68 dBm or higher 48 Mbps -72 dBm to -69 dBm 36 Mbps -76 dBm to -73 dBm 24 Mbps -80 dBm to -77 dBm 18 Mbps -83 dBm to -81 dBm 12 Mbps -85 dBm to -84 dBm 9 Mbps -87 dBm to -86 dBm 6 Mbps -88 dBm or lower
If the measured RF power level is within x "steps" or x dB of the expected RF power level on the scale of allowable data rates, as checked at 602, then the quality of the link is determined at 604 to be "high". If the measured RF power level is y or more "steps" or is at least y dB above the expected RF power level on the scale of allowable data rates, as checked at 606, then the quality of the link is determined at 608 to be "low". If neither of these conditions is met, then the quality of the link is determined at 610 to be "medium". The values of x and y will depend upon the total number of allowable data rates and on how the abstraction is to be handled either as a finite number of explicit data rates or are converted relative to a common measure such as dBm.
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