Method and Apparatus for Signal Strength Indication

• US 20090280814A1
• Filed: 05/08/2009
• Published: 11/12/2009
• Est. Priority Date: 05/10/2008
• Status: Abandoned Application

• Current Assignee: Blackberry Limited
• Original Assignee: Blackberry Limited
• Inventors: FARNSWORTH, Andrew
• Application Number:
  US12/463,157
• Publication Number:
  US 20090280814A1
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 17/26 using historical data, averaging values or statistics
• CPC Class Codes: H04B 17/327 Received signal code power [RSCP]
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method, in a wireless communications device, the method for reporting a signal strength indication from a first layer to a second layer, the method comprising: measuring and reporting an initialisation value of signal strength; periodically measuring a current value of signal strength; determining whether a change in signal strength meets a threshold criterion; reporting the current value of signal strength as an update value of signal strength when the change in signal strength meets a threshold criterion.

Claims

1. A method, in a wireless communications device, the method for reporting a signal strength indication from a first layer to a second layer, the method comprising:

measuring and reporting an initialization value of signal strength;

periodically measuring a current value of signal strength;

determining whether a change in signal strength meets a threshold criterion;

reporting the current value of signal strength as an update value of signal strength when the change in signal strength meets a threshold criterion.

2. A method as claimed in claim 1, wherein the threshold criterion is that the change in signal strength is greater than or equal to a threshold value.

3. A method as claimed in claim 2, wherein the threshold value is 3 dBm.

4. A method as claimed in claim 1, wherein the initialization value of signal strength is reported upon:

the wireless communications device first camping on a cell following receipt of a camp request;

cell reselection from a first radio access technology to a second radio access technology;

hard handover from the first radio access technology to the second radio access technology; and

cell change order from the first radio access technology to the second radio access technology.

5. A method as claimed in claim 4, wherein the first radio access technology is GSM.

6. A method as claimed in claim 4, wherein the second radio access technology is UMTS.

7. A method as claimed in claim 1, wherein when the wireless communications device can communicate with a wireless communications network, the value of signal strength is the highest value of the set of instantaneous signal strengths measured on a particular channel of the or each cell the wireless communications device is in communication with.

8. A method as claimed in claim 7, wherein the value of signal power is measured using the Received Signal Code Power (RSCP) of the particular channel.

9. A method as claimed in claim 7, wherein the particular channel is the Primary Common Pilot Channel (Primary CPICH).

10. A method as claimed in claim 1, wherein the value of signal strength is determined to have a predefined value when the wireless communications device cannot communicate with a wireless communications network.

11. A method as claimed in claim 1, wherein measuring the current value of signal strength comprises measuring a raw value of signal strength and filtering the raw value of signal strength to obtain the current value of signal strength.

12. A method as claimed in claim 11, wherein the filtering of the raw value of signal strength comprises taking an average of the raw value of signal strength and a previously obtained filtered value of signal strength.

13. A method as claimed in claim 12, wherein the average is a weighted average using a weighting factor “

a”

as a multiplier of the raw value of signal strength and a weighting factor “

1−

a”

as a multiplier of the previously obtained filtered value of signal strength.

14. A method as claimed in claim 13, wherein the weighting factor “

a”

is obtained from the discontinuous reception cycle length using a lookup table.

15. A method as claimed in claim 13, wherein the weighting factor “

a”

is determined by the communication state of the wireless communications device.

16. A method as claimed in claim 11, wherein the filtering is continued across events for which a step change is expected.

17. A method as claimed in claim 16, wherein the event for which a step change is expected is one of:

a communication state transition of the wireless communications device;

a cell handover;

cell reselection when the wireless communications device is in a bidirectional communication state using shared channels;

cell reselection when the wireless communications device is in a communication state having discontinuous reception;

connection to a cell in an active set having the highest instantaneous value of the received signal power of the cells in the new active set; and

disconnection from the cell in an active set having the highest instantaneous value of the received signal power of the cells in the active set.

18. A wireless communications device having a first layer and a second layer, wherein the first layer is arranged to:

measure an initialization value of signal strength;

report the initialization value of signal strength to the second layer;

periodically measure a current value of signal strength;

determine whether a change in signal strength meets a threshold criterion;

report the current value of signal strength to the second layer as an update value of signal strength when the change in signal strength meets a threshold criterion.

19. A computer program product comprising program code, the computer program product arranged to cause a first layer of a wireless communications device to:

measure an initialization value of signal strength;

report the initialization value of signal strength to a second layer of the wireless communications device;

periodically measure a current value of signal strength;

determine whether a change in signal strength meets a threshold criterion;

report the current value of signal strength to the second layer as an update value of signal strength when the change in signal strength meets a threshold criterion.