Mobile assisted handoff in radiocommunication systems

• US 6,473,602 B1
• Filed: 10/28/1996
• Issued: 10/29/2002
• Est. Priority Date: 10/28/1996
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Bottomley, Gregory E.
• Primary Examiner(s): LE, THANH C
• Application Number:
  US08/740,306
• Time in Patent Office: 2,192 Days
• Field of Search: 455/67.1, 455/67.3, 455/226.1, 455/226.2, 455/437, 455/302, 455/280, 455/338, 370/210, 370/330, 370/335, 370/342, 370/344, 370/337, 370/347, 375/260, 375/227
• US Class Current: 455/226.1
• 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

Methods and apparatuses for radiocommunication systems including energy (e.g., signal strength) measurements are described. To enable measurements to be performed in parallel with information signal decoding and demodulation, a duplicate of a received signal can be made. The duplicate can be processed to enable measurement on any desired channel. Various access methodologies including FDMA, TDMA and CDMA are contemplated. The measurement information can then be reported to the system for usage in handoff determination. The inventive techniques allow for MAHO measurements to be performed without idle time being available for a receiver and without a dedicated scanning receiver being provided solely for measurement purposes.

Claims

1. A communications terminal comprising:

means for receiving and processing a radio signal to produce a multichannel signal including a plurality of channels and to produce a demodulated signal corresponding to a single channel;

means for producing digital samples of said multichannel signal;

means for removing at least one channel from said digital samples of said multichannel signal, wherein processing means make energy measurements on said at least one channel, wherein said single channel and said at least one channel are associated with different frequencies.

2. The communications terminal of claim 1, wherein said means for receiving and processing further comprises a splitter for producing two copies of said radio signal.

3. The communications terminal of claim 2, wherein said means for receiving and processing further comprises a narrowband filter for receiving a first copy of said radio signal and for passing a subset of frequencies associated with said single channel.

4. The communications terminal of claim 2, wherein said means for receiving and processing further comprises an image rejection filter for receiving a second copy of said radio signal.

5. The communications terminal of claim 1, wherein said means for producing digital samples is an A/D convertor.

6. The communications terminal of claim 1, wherein said means for removing said at least one channel further comprises a channelizer.

7. The communications terminal of claim 1, wherein said at least one of said plurality of channels has an FDMA component.

8. The communications terminal of claim 1, wherein said at least one of said plurality of channels has a TDMA component.

9. The communications terminal of claim 1, wherein said at least one of said plurality of channels has a CDMA component.

10. The communications terminal of claim 1, wherein said means for removing said at least one channel further comprises a fast fourier transform processor.

11. The communications terminal of claim 10, wherein said means for processing said digital samples further comprises at least one extraction device downstream of said fast fourier transform processor for further separating said at least one of said plurality of channels from said digital samples.

12. The communications terminal of claim 11, wherein said at least one extraction device operates to separate a desired timeslot from an output of said fast fourier transform processor.

13. The communications terminal of claim 11, wherein said at least one extraction device operates to correlate an output of said fast fourier transform processor with a spreading code.

14. The communications terminal of claim 1, further comprising:

means for transmitting said measurements over an air interface.

15. A method for making signal strength measurements on at least one channel comprising the steps of:

generating a first and a second copy of a received signal;

processing said first copy to obtain an information signal on a first channel; and

processing said second copy to obtain signal strength measurements on said at least one channel, wherein said first channel and said at least one channel are associated with different frequencies.

16. The method of claim 15, wherein said step of processing said first copy further comprises the steps of:

filtering said first copy to obtain a frequency band of interest; and

demodulating said first copy to obtain said information signal.

17. The method of claim 15, wherein said step of processing said second copy further comprises the steps of:

digitizing said second copy to produce digital samples;

buffering said digital samples; and

processing said buffered digital samples.

18. The method of claim 17, wherein said step of processing said second copy further comprises the steps of:

selecting from among said buffered digital samples, those samples associated with said at least one channel;

determining magnitude squared values of said selected digital samples; and

accumulating said magnitude squared values.

19. The method of claim 17, wherein said step of processing said buffered digital samples further comprises the step of:

channelizing said buffered digital samples based upon at least one of frequency, time and spreading code.

20. The method of claim 17, wherein said step of processing said buffered digital samples further comprises the step of:

processing said buffered digital samples using a fast fourier transform processor to separate said buffered digital samples by frequency.

21. The method of claim 20, further comprising the step of:

extracting said at least one channel from said processed buffered digital samples based upon a desired time slot.

22. The method of claim 20, further comprising the step of:

extracting said at least one channel from said processed buffered digital samples based upon a desired spreading code.

23. A communication terminal comprising:

a receiver for receiving a transmitted signal, processing said transmitted signal into a filtered signal and generating an information signal therefrom;

a splitter for generating a copy of said filtered signal; and

a processor for generating energy measurements on at least two channels associated with different frequencies using said copy of said filtered signal.