Method and System for performing handoff in wireless communication systems

• US 20070064640A1
• Filed: 11/03/2006
• Published: 03/22/2007
• Est. Priority Date: 08/11/1999
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Grilli, Francesco, Willenegger, Serge, Tiedemann, Edward
• Granted Patent: US 8,199,716 B2
• Time in Patent Office: Days
• US Class Current: 370/320
• CPC Class Codes: H04B 7/2675 Frequency synchronisation
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 36/0088 Scheduling hand-off measurements
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/283 Power depending on the position of the mobile
• CPC Class Codes: H04W 52/288 taking into account the usage mode, e.g. hands-free, data transmission, telephone
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 52/48 during retransmission after error or non-acknowledgment
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase

Abstract

The structure of a time-multiplexed physical channel is used to time inter-frequency or inter-system search excursions. A mobile station that receives an instruction to perform a search excursion prepares for the search excursion by detecting the first radio frame of a message frame. Transport format combination indicator bits are extracted from the first radio frame and stored. After the search excursion is performed, the mobile station recalls the stored indicator bits and uses the indicator bits to decode other radio frames of the message frame.

Claims

1. A method for performing a search excursion from an original frequency on a wideband code division multiple access (WCDMA) system to a target frequency, comprising:

decoding at least one radio frame in a Transmission Time Interval (TTI) on the original frequency;

extracting a parameter value from the at least one radio frame and storing the parameter value in a memory element;

tuning to a target frequency after storing the parameter value;

tuning to the original frequency; and

decoding a subsequently received radio frame in the TTI by using the stored parameter value.

2. The method of claim 1, wherein the target frequency is on a WCDMA system.

3. The method of claim 1, wherein the target frequency is on a non-WCDMA system.

4. A method for timing a search excursion performed by a mobile station operating in a spread spectrum communications system, comprising:

detecting a first radio frame of a Transmission Time Interval (TTI) on an original frequency;

extracting a plurality of indicator bits from the first radio frame;

storing the plurality of indicator bits;

performing the search excursion on a target frequency, wherein the search excursion ends with a return to the original frequency; and

decoding a subsequent radio frame of the TTI using the stored plurality of indicator bits from the first radio frame.

5. The method of claim 4, wherein the first radio frame is 10 ms in duration.

6. The method of claim 5, wherein performing the search excursion on the target frequency comprises tuning the mobile station to the target frequency, whereupon the mobile station collects and stores signal samples from the target frequency.

7. The method of claim 6, wherein the method for timing the search excursion further comprises increasing the amount of power allocated to the subsequent radio frame of the TTI.

8. The method of claim 6, wherein the method for timing the search excursion further comprises increasing the amount of power allocated to the first radio frame of the TTI.

9. An apparatus for performing a timed search excursion in a wireless communication system, comprising:

at least one memory element; and

a processor configured to execute a set of instructions stored on the at least one memory element, the set of instructions for;

decoding at least one radio frame in a Transmission Time Interval (TTI) on the original frequency;

extracting a parameter value from the at least one radio frame and storing the parameter value in the at least one memory element;

controlling a search excursion to a target frequency after storing the parameter value, wherein the search excursion ends with a return to the original frequency; and

decoding a subsequently received radio frame by using the stored parameter value.

10. An apparatus for performing a timed search excursion in a wireless communication system, comprising:

means for decoding at least one radio frame in a Transmission Time Interval (TTI) on the original frequency;

means for extracting a parameter value from the at least one radio frame and storing the parameter value in at least one memory element;

means for performing a frequency search on a target the frequency and returning to the original frequency, whereupon the means for decoding the at least one radio frame further decodes a subsequently received radio frame by using the stored parameter value.

11. A method for timing a frequency search excursion in a wireless communications system having a mobile station exchanging communications with a base station the method comprising:

determining at least one transmission parameter value from the first radio frame of the plurality of associated radio frames and storing the at least one transmission parameter value;

tuning the mobile station to the target frequency, whereupon the mobile station collects and stores signal samples from the target frequency;

tuning the mobile station to the original frequency;

processing the stored samples from the target frequency to obtain a result;

transmitting the result from processing the stored samples to the base station;

increasing the amount of power allocated to subsequently received radio frames of the plurality of associated radio frames; and

decoding the subsequently received frame symbols using the stored transmission parameter value.

12. The method of claim 11 further comprising the step of keeping the transmission energy of a pilot channel equal to the transmission energy of the pilot channel prior to said frequency search excursion.

13. The method of claim 11 further comprising the steps of:

determining whether said mobile station is capable of increasing the transmission power of said information channels to the desired extent; and

selectively increasing the transmission power of said information channels when said mobile station is not capable of increasing the transmission power of said information channels to the desired extent.

14. The method of claim 13, wherein selectively increasing the transmission power of said information channels, comprises the steps of:

ranking the channels in accordance with the importance of having a non-interrupted reverse link transmission; and

adjusting the transmission energies of said information channels in accordance with said ranking.

15. The method of claim 14 wherein said information channels comprise a traffic channel and a common access channel.