Signal strength measurements in cellular telecommunication systems

• US 7,366,475 B2
• Filed: 06/04/2004
• Issued: 04/29/2008
• Est. Priority Date: 06/04/2004
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Ramesh, Rajaram
• Primary Examiner(s): Tran; Tuan A.
• Application Number:
  US10/861,987
• Publication Number:
  US 20050272375A1
• Time in Patent Office: 1,425 Days
• Field of Search: 455423-425, 455436-451, 4554521- 2, 455453-455, 455500-502, 455 631- 2, 455 6711- 16, 455/67.7, 455/296, 455 68- 70, 455/550.1, 455/561, 455 901- 2, 4551141- 2, 4551151- 4, 4551611- 3, 4552261- 4, 370252-253, 370328-333, 370335-338, 370277-278, 370286-292, 370/431, 370441-442, 370461-465, 370/437, 370/503, 370509-510, 370/512, 370/514, 375229-236, 375340-343, 375346-349, 375/150, 375/152, 375/285
• US Class Current: 455/67.13
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/302 due to low signal strength

Abstract

A mobile station (MS) and method for estimating received signal strength of a radio signal from a neighboring cell in a cellular radio telecommunication network. The MS measures the received signal strength of the radio signal over a plurality of frames, and calculates an average received signal strength. During an idle frame, the MS receives a synchronization channel (SCH) signal, and determines a channel estimate for the SCH using a known extended training sequence. The extended training sequence is then modified with the channel estimate, and the modified extended training sequence is subtracted from the received SCH signal to obtain a residual signal. The MS calculates a residual energy of the residual signal, and subtracts the residual energy from the average received signal strength of the radio signal to obtain an estimated received signal strength of the radio signal from the neighboring cell.

Claims

1. A method of estimating received signal strength of a radio signal from a neighboring cell in a cellular radio telecommunication network, said method comprising the steps of:

measuring the received signal strength of the radio signal over a plurality of frames;

calculating an average received signal strength over the plurality of frames;

receiving a synchronization channel signal during an idle frame;

determining a channel estimate for the synchronization channel using a known extended training sequence;

modifying the extended training sequence with the channel estimate;

subtracting the modified extended training sequence from the received synchronization channel signal to obtain a residual signal;

calculating an energy level of the residual signal to obtain a residual energy; and

subtracting the residual energy of the residual signal from the average received signal strength of the radio signal to obtain an estimated received signal strength of the radio signal from the neighboring cell.

2. The method of claim 1, wherein the method is performed by a mobile station operating in the cellular radio telecommunication network.

3. The method of claim 2, wherein the cellular radio telecommunication network is an unsynchronized Global System for Mobile Communications (GSM) network.

4. The method of claim 2, wherein the cellular radio telecommunication network is a synchronized Global System for Mobile Communications (GSM) network.

5. The method of claim 2, further comprising the steps of:

reporting the estimated received signal strength to the network, and

utilizing the estimated received signal strength by the network to determine whether to handover the mobile station to the neighboring cell.

6. A method of estimating received signal strength of a radio signal from a neighboring cell in a cellular radio telecommunication network, said method comprising the steps of:

measuring the received signal strength of the radio signal over a plurality of frames;

calculating an average received signal strength over the plurality of frames;

receiving a synchronization channel signal during an idle frame;

determining a channel estimate for the synchronization channel using a known extended training sequence;

modifying the extended training sequence with the channel estimate;

subtracting the modified extended training sequence from the received synchronization channel signal to obtain a residual signal;

calculating an energy level of the residual signal to obtain a residual energy;

calculating a signal component energy on the synchronization channel by determining the energy of the modified extended training sequence;

determining whether the average received signal strength minus the residual energy is greater than or equal to the signal component energy plus a predefined threshold value;

upon determining that the average received signal strength minus the residual energy is greater than or equal to the signal component energy plus the predefined threshold value, utilizing the average received signal strength minus the residual energy as the estimated received signal strength of the radio signal from the neighboring cell; and

upon determining that the average received signal strength minus the residual energy is less than the signal component energy plus the predefined threshold value, utilizing the signal component energy as the estimated received signal strength of the radio signal from the neighboring cell.

7. The method of claim 6, wherein the method is performed by a mobile station operating in the cellular radio telecommunication network.

8. The method of claim 7, wherein the cellular radio telecommunication network is an unsynchronized Global System for Mobile Communications (GSM) network.

9. The method of claim 7, wherein the cellular radio telecommunication network is a synchronized Global System for Mobile Communications (GSM) network.

10. The method of claim 7, further comprising the steps of:

reporting the estimated received signal strength to the network, and

utilizing the estimated received signal strength by the network to determine whether to handover the mobile station to the neighboring cell.

11. A mobile station for estimating received signal strength of a radio signal from a neighboring cell in a cellular radio telecommunication network, said mobile station comprising:

means for measuring the received signal strength of the radio signal over a plurality of frames;

means for calculating an average received signal strength over the plurality of frames;

means for receiving a synchronization channel signal during an idle frame;

means for determining a channel estimate for the synchronization channel using a known extended training sequence;

means for modifying the extended training sequence with the channel estimate;

means for subtracting the modified extended training sequence from the received synchronization channel signal to obtain a residual signal;

means for calculating an energy level of the residual signal to obtain a residual energy; and

means for subtracting the residual energy of the residual signal from the average received signal strength of the radio signal to obtain an estimated received signal strength of the radio signal from the neighboring cell.

12. The mobile station of claim 11, wherein the mobile station is adapted to operate in an unsynchronized Global System for Mobile Communications (GSM) network.

13. The mobile station of claim 11, wherein the mobile station is adapted to operate in a synchronized Global System for Mobile Communications (GSM) network.

14. The mobile station of claim 11, further comprising means for reporting the estimated received signal strength to the network for use in a handover algorithm.

15. A mobile station for estimating received signal strength of a radio signal from a neighboring cell in a cellular radio telecommunication network, said mobile station comprising:

means for measuring the received signal strength of the radio signal over a plurality of frames;

means for calculating an average received signal strength over the plurality of frames;

means for receiving a synchronization channel signal during an idle frame;

means for determining a channel estimate for the synchronization channel using a known extended training sequence;

means for modifying the extended training sequence with the channel estimate;

means for subtracting the modified extended training sequence from the received synchronization channel signal to obtain a residual signal;

means for calculating an energy level of the residual signal to obtain a residual energy;

means for calculating a signal component energy on the synchronization channel by determining the energy of the modified extended training sequence;

means for determining whether the average received signal strength minus the residual energy is greater than or equal to the signal component energy plus a predefined threshold value;

means responsive to a determination that the average received signal strength minus the residual energy is greater than or equal to the signal component energy plus the predefined threshold value, for utilizing the average received signal strength minus the residual energy as the estimated received signal strength of the radio signal from the neighboring cell; and

means responsive to a determination that the average received signal strength minus the residual energy is less than the signal component energy plus the predefined threshold value, for utilizing the signal component energy as the estimated received signal strength of the radio signal from the neighboring cell.

16. The mobile station of claim 15, wherein the mobile station is adapted to operate in an unsynchronized Global System for Mobile Communications (GSM) network.

17. The mobile station of claim 15, wherein the mobile station is adapted to operate in a synchronized Global System for Mobile Communications (GSM) network.

18. The mobile station of claim 15, further comprising means for reporting the estimated received signal strength to the network for use in a handover algorithm.

19. A method of estimating received signal strength of a first radio signal from a neighboring cell in a cellular radio telecommunication network, said method comprising the steps of:

measuring the received signal strength of the first radio signal over a plurality of frames;

calculating an average received signal strength over the plurality of frames;

receiving on a radio channel, a second radio signal having a known component that has been modified by the radio channel;

determining what modifications have been made to the known component by the radio channel;

reconstructing the known component to account for the radio channel modifications;

subtracting the reconstructed component from the received second radio signal to obtain a residual signal;

calculating an energy level of the residual signal to obtain a residual energy; and

subtracting the residual energy from the average received signal strength of the first radio signal to obtain an estimated received signal strength of the first radio signal from the neighboring cell.

20. The method of claim 19, wherein the network is a Global System for Mobile Communications (GSM) network and the step of receiving a second radio signal having a known component includes receiving a frequency correction channel (FCH) having a known sine wave at a known frequency.

21. A method of estimating received signal strength of a first radio signal from a neighboring cell in a cellular radio telecommunication network, said method comprising the steps of:

measuring the received signal strength of the first radio signal over a plurality of frames;

calculating an average received signal strength over the plurality of frames;

receiving a timing signal on a frequency correction channel (FCH) transmitted on a radio channel, said timing signal having a known sine wave at a known frequency, wherein the sine wave is modified by the radio channel during transmission;

determining what modifications have been made to the known sine wave by the radio channel;

reconstructing the known sine wave to account for the modifications by the radio channel;

subtracting the reconstructed sine wave from the sine wave received on the FCH to obtain a residual signal;

calculating an energy level of the residual signal to obtain a residual energy; and

subtracting the residual energy from the average received signal strength of the first radio signal to obtain an estimated received signal strength of the first radio signal from the neighboring cell.

22. A method of estimating received signal strength of a first radio signal from a neighboring cell in a cellular radio telecommunication network, said method comprising the steps of:

calculating an average received signal strength of the first radio signal;

receiving a second radio signal on a frequency correction channel (FCH) transmitted on a radio channel, said second radio signal having a known sine wave at a known frequency, wherein the sine wave is modified by the radio channel during transmission;

calculating a residual energy associated with the FCH by performing the steps of;

determining what modifications have been made to the known sine wave by the radio channel;

reconstructing the known sine wave to account for the modifications by the radio channel;

subtracting the reconstructed sine wave from the sine wave received on the FCH to obtain an FCH residual signal; and

calculating an energy level of the FCH residual signal to obtain an FCH residual energy;

receiving a third radio signal on a synchronization channel (SCH), said third radio channel having a known extended training sequence;

calculating a residual energy associated with the SCH by performing the steps of;

determining a channel estimate for the synchronization channel using a known extended training sequence;

modifying the extended training sequence with the channel estimate;

subtracting the modified extended training sequence from the received synchronization channel signal to obtain an SCH residual signal; and

calculating an energy level of the SCH residual signal to obtain an SCH residual energy;

averaging the FCH residual energy and the SCH residual energy; and

subtracting the averaged residual energy from the average received signal strength of the first radio signal to obtain an estimated received signal strength of the first radio signal from the neighboring cell.