Floor determination for a wireless device

• US 7,894,412 B2
• Filed: 09/07/2007
• Issued: 02/22/2011
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Venkataramani, Nirmala Nott, Jacob, Anto, Maldonado, Emilio, Hart, Brian Donald
• Primary Examiner(s): Duong; Frank
• Application Number:
  US11/852,018
• Publication Number:
  US 20090067392A1
• Time in Patent Office: 1,264 Days
• Field of Search: 370328-329, 455/115.3, 455/116.3, 455/226.2, 455/404.2, 455/456.1, 455/456.3
• US Class Current: 370/338
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 2205/02 Indoor
• CPC Class Codes: G01S 5/014 Identifying transitions between environments
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

An apparatus configured to acquire received signal strength intensities (RSSIs) for a wireless device from a plurality of access points (APs) located on a plurality floors. The apparatus is configured to determine which floor the wireless device is on by analyzing the RSSIs. In an example embodiment, the RSSIs are adjusted, and the adjusted RSSIs for each floor are summed. The floor with highest sum of adjusted RSSIs is determined to be the floor the wireless device is on. In an example embodiment, the floor that the wireless device is on is determined by calculating the probability that the wireless device is within the cell of each AP on the network, and combining the probabilities for each floor. Known RSSIs between APs can be employed for comparing measured RSSIs with the known RSSIs to determine the probability that the wireless device is within the cell of each AP.

Claims

1. An apparatus, comprising:

a communication interface configured to acquire received signal strength indicator (RSSI) data for a wireless device from a plurality of access points on a plurality of floors; and

floor determination logic in data communication with the communication interface, the floor determination logic is configured to determine a floor that the wireless device is located on by analyzing the RSSI data acquired by the communication interface;

wherein the floor determination logic is configured to calculate an adjusted RSSI from the acquired RSSI data for the wireless device received by every access point by one of a group consisting of adding and subtracting a predetermined value from the RSSI data acquired from each access point;

wherein the floor determination logic is configured to sum the adjusted RSSI for each floor; and

wherein the floor determination logic is configured to select the floor with the highest sum.

2. An apparatus according to claim 1, wherein the floor determination logic is configured to calculate the adjusted RSSI based on the maximum value selected from a group consisting of a predefined minimum value and the acquired RSSI.

3. An apparatus according to claim 2, wherein the predefined minimum value is −

90 dB.

4. An apparatus according to claim 3, wherein the predetermined value is −

90 dB.

5. An apparatus according to claim 1, wherein the predetermined value is −

90 dB.

6. An apparatus, comprising:

a communication interface configured to acquire received signal strength indicator (RSSI) data for a wireless device from a plurality of access points on a plurality of floors; and

floor determination logic in data communication with the communication interface, the floor determination logic is configured to determine a floor that the wireless device is located by analyzing the RSSI data acquired by the communication interface;

wherein the floor determination logic is configured to determine which floor the wireless device is on by calculating an approximate probability of the wireless device being within each access point'"'"'s cell;

wherein the floor determination logic is configured to combine the approximate probability for access points on each floor; and

wherein the floor determination logic is configured to determine the wireless device is located on the floor with the highest combined approximate probabilites.

7. An apparatus according to claim 6, wherein the floor determination logic employs predicted RSSIs between clients under or nearby an AP to another access point to determine the approximately probability of the wireless device being within each access point'"'"'s cell.

8. An apparatus according to claim 7, wherein the floor determination logic uses measured RSSIs between access points when known.

9. An apparatus according to claim 8, wherein the floor determination logic factors out transmitting access point antenna gain and excess transmitter power.

10. An apparatus according to claim 6, the floor determination logic is further configured for determining the probability the wireless device is within a first access point'"'"'s cell by comparing a measured RSSI from the wireless device by a second access point with one of a group consisting of a predicted RSSI and a measured RSSI between the first and second access points.

11. An apparatus according to claim 10, the floor determination logic further comprises logic for adjusting the result of the comparison with a shadowing standard deviation between the first and second access points.

12. An apparatus according to claim 6, the floor determination logic is further configured for determining the probability the wireless device is within a first access point'"'"'s cell by comparing a predetermined minimum RSSI with one of a group consisting of a predicted RSSI and a measured RSSI between the first access point and the second access point responsive to the second access point not receiving a signal from the wireless device.

13. An apparatus according to claim 6, the floor determination logic is further configured for determining the probability the wireless device is within a first access point'"'"'s cell by comparing a difference between a predetermined minimum RSSI with one of a group consisting of a predicted RSSI and a measured RSSI between the first access point and the access point being evaluated responsive to the access point being evaluated not receiving a signal from the wireless device.

14. An apparatus according to claim 6, the floor determination is configured to determine the probability that the wireless device is within a first access point'"'"'s cell by subtracting one of a group consisting of a predicted RSSI and a measured RSSI between the first access point and a second access point from a RSSI measured for the wireless device measured by the second access point, wherein the result of the subtraction is divided by a shadowing standard deviation between the first access point and the second access point, when the RSSI from the wireless device is measured by the second access point;

and

the floor determination logic is further configured to determine the probability that the wireless device is within a first access point'"'"'s cell by comparing a predetermined minimum signal with one of a group consisting of a predicted RSSI and a measured RSSI between the first and second access points responsive to the second access point not receiving a signal from the wireless device.

15. An apparatus according to claim 6, the floor determination logic is configured to determine the probability that the wireless device is within a first access point'"'"'s cell by computing a function for every access point on the network, the function comprising one of a group consisting of:

a difference between an RSSI measured by an access point being evaluated and one of a group consisting of a predicted RSSI and a measured RSSI between the first access point and the access point being evaluated, wherein the difference is divided by a shadowing standard deviation between the first access point and the access point being evaluated, responsive to the access point being evaluated detecting a RSSI above a predetermined threshold; and

a difference between a predetermined minimum RSSI with one of a group consisting of a predicted RSSI and a measured RSSI between the first access point and the access point being evaluated responsive to the access point being evaluated not receiving a signal from the wireless device.

16. An apparatus according to claim 15, wherein the function evaluates the RSSI of the wireless device received by the first access point by one of a group consisting of:

a difference between an RSSI measured by the first access point and a predefined within cell RSSI, wherein the difference is divided by a shadowing standard deviation for the first access point '"'"'s cell; and

the difference between a predetermined minimum RSSI with the predefined within cell RSSI responsive to the first access point not receiving a signal from the wireless device.

17. An apparatus according to claim 16, wherein the probability for the wireless device being within the first access point'"'"'s cell comprises the product of the function computed for every access point on the network operating on a same channel as the first access point

18. An apparatus according to claim 17, wherein the predefined minimum is −

90 dBm and the predefined within cell RSSI is −

55 dBm.

19. An apparatus, comprising:

means for acquiring received signal strength intensities (RSSIs) for between a plurality of access points on a network distributed among a plurality of floors;

means for acquiring a RSSI value for a wireless client from each access point on the network;

means for determining the probability the wireless device is within an access point'"'"'s cell, comprising means for comparing for each access point the measured RSSI value for the wireless client with an RSSI value expected when the client is within proximity of the access point and an access point providing the measured RSSI value, the means for determining the probability determines the probability for each access point on the network;

means for determining the probability for a floor, comprising means for combining the probabilities of each access point on the floor, the means for determining the probability for a floor determining the probability for all floors on the network; and

means for determining which floor the wireless device is on, comprising means for selecting the floor with the highest combined probability.

20. An apparatus according to claim 19, the means for comparing further comprising means for adjusting the comparison based on a shadowing standard deviation.

21. A method, comprising:

receiving received signal strength indicator (RSSI) data for a wireless device from a plurality of access points having associated cells dispersed on a plurality of floors;

calculating an approximate probability of the wireless device located within each access point'"'"'s cell;

combining the calculated probabilities for each floor; and

determining a floor the wireless device is located on by selecting the floor with the highest combined calculated probabilities.

22. The method according to claim 21, the calculating further comprises comparing predicted RSSIs of clients within an access point'"'"'s cell to measured RSSIs.

23. The method according to claim 22, the comparing further comprises adjusting results of the comparison with a shadowing standard deviation between access points.

24. The method according to claim 22, the comparing further comprises using a predefined value responsive to an RSSI being less than the predefined value.