Method of creating and utilizing diversity in a multiple carrier communication system

• US 8,374,613 B2
• Filed: 03/31/2008
• Issued: 02/12/2013
• Est. Priority Date: 08/08/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Uppala, Sathyadev Venkata
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Mohebbi, Kouroush
• Application Number:
  US12/060,249
• Publication Number:
  US 20080182580A1
• Time in Patent Office: 1,779 Days
• Field of Search: None
• US Class Current: 455/440
• CPC Class Codes: H04W 16/12 Fixed resource partitioning
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/20 for optimising the interference level
• CPC Class Codes: H04W 52/0235 where the received signal is a power saving command
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/281 taking into account user or data type priority
• CPC Class Codes: H04W 52/283 Power depending on the position of the mobile
• CPC Class Codes: H04W 52/286 during data packet transmission, e.g. high speed packet access [HSPA]
• CPC Class Codes: H04W 52/287 when the channel is in stand-by
• CPC Class Codes: H04W 52/288 taking into account the usage mode, e.g. hands-free, data transmission, telephone
• CPC Class Codes: H04W 52/60 using different transmission rates for TPC commands
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 68/02 Arrangements for increasing efficiency of notification or paging channel
• CPC Class Codes: H04W 68/025 Indirect paging
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/51 based on terminal or device properties
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

In many cellular systems, reusing spectrum bandwidth, creates problems in boundary regions between the cells and sectors where the signal strength received from adjacent base stations or adjacent sector transmissions of a single base station may be nearly equivalent. The invention creates a new type of diversity, referred to as multiple carrier diversity by utilizing multiple carriers, assigning different power levels to each carrier frequency at each base station, and/or offsetting sector antennas. The cell and/or sector coverage areas can be set so as to minimize or eliminate overlap between cell and/or sector boundary regions of different carrier frequencies. Mobile nodes traveling throughout the system can exploit multiple carrier diversity by detecting carriers and selecting to use a non-boundary carrier based on other system criteria in order to improve performance. Boundary carriers may, but need not be, identified and excluded from consideration for use by a wireless terminal.

Claims

1. A method of operating a wireless terminal in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two carrier signals including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, the method comprising:

operating said wireless terminal to communicate with said base station using said first carrier signal over a period of time;

during said period of time, checking a plurality of said at least two carrier signals to determine channel interference associated with each of said at least two carrier signals;

estimating by said wireless terminal, intersector channel interference due to transmissions from another sector of said base station;

identifying at least one sector boundary carrier frequency based on said intersector channel interference;

determining candidate carrier frequencies by considering traffic loading, power, and noise levels, wherein said candidate carrier frequencies exclude said at least one sector boundary carrier frequency; and

initiating an intercarrier handoff based on the intersector channel interference, the intercarrier handoff occurring between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference, wherein said intercarrier handoff involves a carrier signal having one of said candidate carrier frequencies.

2. The method of claim 1, wherein said wireless terminal estimates intercell channel interference due to transmissions from another base station and wherein said intercarrier handoff is initiated to cause an intercarrier handoff to a carrier subject to lower intercell interference in a geographic region in which said wireless terminal is located.

3. The method of claim 1, wherein said intercarrier handoff is triggered by detecting a decrease in the first carrier signal'"'"'s signal to noise ratio.

4. The method of claim 1, in which said intercarrier handoff is initiated to cause an intercarrier handoff to a carrier subject to lower intersector interference in a geographic region in which said wireless terminal is located.

5. A wireless terminal, comprising:

receiver means for receiving carrier signals corresponding to at least two different available carrier frequencies transmitted by a same base station at different power levels;

carrier selection means for determining candidate carrier frequencies from among said at least two different available carrier frequencies by considering traffic loading, power, and noise levels and for selecting which one of said at least two different available carrier frequencies to use at any point in time for the receipt of information, said carrier selection means including;

means for repeatedly checking, during an interval of time during which said wireless terminal has a reliable communications connection with said base station using a first one of said at least two different available carrier frequencies, which of said at least two different available carrier frequencies has better interference properties;

means for estimating intersector channel interference due to transmissions from another sector of said base station;

means for identifying at least one sector boundary carrier frequency based on said intersector channel interference; and

means for signaling said base station to initiate an intracell intercarrier handoff to change said carrier frequency used to communicate with said wireless terminal when one of said candidate carrier frequencies is determined to be better for communication of signals to said wireless terminal than said carrier frequency being used, the intracell intercarrier handoff being based on said intersector channel interference,

wherein said candidate carrier frequencies exclude said at least one sector boundary carrier frequency, and

wherein said intracell intercarrier handoff involves a carrier signal having one of said candidate carrier frequencies.

6. The wireless terminal of claim 5, wherein said intracell intercarrier handoff is an intersector handoff.

7. The wireless terminal of claim 5, wherein said means for checking performs said checking operation irrespective of a signal quality of a carrier signal being used for an ongoing communication session.

8. The wireless terminal of claim 5, further comprising means for distinguishing between intracell interference and other types of interference.

9. The wireless terminal of claim 5, further comprising means for distinguishing between intersector interference and other types of interference.

10. A wireless terminal, comprising:

a receiver for receiving carrier signals corresponding to at least two different available carrier frequencies transmitted by a same base station at different power levels;

a carrier selection module for determining candidate carrier frequencies from among said at least two different available carrier frequencies by considering traffic loading, power, and noise levels and for selecting which one of said at least two different available carrier frequencies to use at any point in time for the receipt of information;

a carrier strength measurement module for repeatedly checking, during an interval of time during which said wireless terminal has a reliable communications connection with said base station using a first one of said at least two different available carrier frequencies, which of said at least two different available carrier frequencies has better interference properties;

an intersector channel interference estimating means for estimating intersector channel interference due to transmissions from another sector of said base station;

a sector boundary identification module for identifying at least one sector boundary carrier frequency based on said intersector channel interference; and

a transmitter for signaling said base station to initiate an intracell intercarrier handoff to change said carrier frequency used to communicate with said wireless terminal when one of said candidate carrier frequencies is determined to be better for communication of signals to said wireless terminal than said carrier frequency being used based on said estimated intersector channel interference,

wherein said candidate carrier frequencies exclude said at least one sector boundary carrier frequency, and

wherein said intracell intercarrier handoff involves a carrier signal having one of said candidate carrier frequencies.

11. The wireless terminal of claim 10, wherein said intracell intercarrier handoff is an intersector handoff.

12. The wireless terminal of claim 10, wherein said carrier strength measurement module performs said checking operation irrespective of a signal quality of a carrier signal being used for an ongoing communication session.

13. A device for use in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two carrier signals including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, said device comprising:

a processor configured to;

control said device to communicate with said base station using said first carrier signal over a period of time;

during said period of time, check a plurality of said at least two carrier signals to determine channel interference associated with each of said at least two carrier signals;

estimate intersector channel interference due to transmissions from another sector of said base station;

identify at least one sector boundary carrier frequency based on said intersector channel interference;

determine candidate carrier frequencies by considering traffic loading, power, and noise levels, wherein said candidate carrier frequencies exclude said at least one sector boundary carrier frequency; and

initiate an intercarrier handoff based on said intersector channel interference, said intercarrier handoff occurring between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference,

wherein said intercarrier handoff involves a carrier signal having one of said candidate carrier frequencies.

14. The device of claim 13, wherein said device estimates intercell channel interference due to transmissions from another base station and wherein said intercarrier handoff is initiated to cause an intercarrier handoff to a carrier subject to lower intercell interference in a geographic region in which said wireless terminal is located.

15. The device of claim 13, wherein said intercarrier handoff is triggered by detecting a decrease in the first carrier signal'"'"'s signal to noise ratio.

16. A computer program product, comprising:

non-transitory computer readable medium embodying computer executable instructions for controlling a wireless terminal in a cell which includes a base station which transmits at least two carrier signals at different power levels, said at least two carrier signals including a first carrier signal having a first carrier frequency and a second carrier signal having a second carrier frequency, the computer readable medium comprising;

instructions for causing said wireless terminal to communicate with said base station using said first carrier signal over a period of time;

instructions for causing said wireless terminal to check a plurality of said at least two carrier signals, during said period of time, to determine channel interference associated with each of said at least two carrier signals; and

to estimate intersector channel interference due to transmissions from another sector of said base station;

instructions for identifying at least one sector boundary carrier frequency based on said intersector channel interference;

instructions for determining candidate carrier frequencies by considering traffic loading, power, and noise levels, wherein said candidate carrier frequencies exclude said at least one sector boundary carrier frequency; and

instructions for causing said wireless terminal to initiate an intercarrier handoff based on said intersector channel interference, said intercarrier handoff occurring between carrier signals used by said base station, while said first carrier signal still provides a signal to noise ratio of at least 0 dB and another one of said carrier signals is subject to lower channel interference,

wherein said intercarrier handoff involves a carrier signal having one of said candidate carrier frequencies.

17. The computer program product of claim 16, wherein said non-transitory computer readable medium further includes:

instructions for causing said wireless terminal to estimate intercell channel interference due to transmissions from another base station; and

wherein said intercarrier handoff is initiated to cause an intercarrier handoff to a carrier subject to lower intercell interference in a geographic region in which said wireless terminal is located.

18. The computer program product of claim 16, wherein said intercarrier handoff is triggered by detecting a decrease in the first carrier signal'"'"'s signal to noise ratio.