Fast forward power control during soft handoff

• US 6,515,975 B1
• Filed: 04/22/1999
• Issued: 02/04/2003
• Est. Priority Date: 04/22/1999
• Status: Active Grant

• Current Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Chheda, Ashvin, Jalali, Ahmad
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): TORRES, MARCOS L
• Application Number:
  US09/296,974
• Time in Patent Office: 1,384 Days
• Field of Search: 370/318, 370/320, 370/322, 370/329, 370/330, 370/331, 370/332, 370/333, 370/335, 370/342, 370/350, 370/441, 370/503, 370/347, 370/378, 370/311, 455/522, 455/69, 455/456, 455/442
• US Class Current: 370/332
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

Disclosed is an apparatus for and method of increasing the stability of a CDMA cellular system using fast forward power control. This is accomplished by improving the relative power level synchronization of all the BTSs communicating with an MS in a handoff mode through the use of at least one of 1) setting the power levels of any BTS other than the BTS having the best measured E_b/N_o (bit energy to noise density) of reverse link FPC (forward power control) bit stream transmissions from said MS, hereinafter BTS(x), to a power level which is a function of the power level of BTS(x), 2) adjusting at least one of lower and upper limits of traffic channel gain of a BTS as a function of whether or not said given MS is in a handoff mode and 3) adjusting at least one of the incremental FPC (forward power control) and RPC (reverse power control) parameters as a function of the number of BTSs in a soft handoff mode with respect to said MS.

Claims

1. A cellular communication system incorporating fast forward power control and having at least 2 BTSs (base transceiver stations), a BSC (base station controller and an MS (mobile station) comprising:

measuring means, comprising a part of each BTS in the system, for measuring the E_b/N_o (bit energy to noise density), at each BTS that is receiving reverse link transmissions from an MS, of reverse link FPC (forward power control) bit stream transmissions from said MS;

BSC comparison means for periodically comparing the measured E_b/N_o to determine, during the time when an MS is in a handoff mode, which BTS is receiving the most reliable FPC data wherein the BTS determined to be is receiving the most reliable FPC data is designated hereinafter as BTS(x);

further BSC comparison means for comparing the transmit power level of each BTS, other than BTS(x), with the transmit power level of BTS(x);

BSC instructing means for instructing each BTS, other than BTS(x), whose power level differs from the transmit power level of BTS(x) by more than a predetermined value, to adjust the power level of transmissions to said MS to the level of BTS(x);

BSC checking means for determining the number of BTSs in a soft handoff mode with respect to a given MS; and

means for adjusting at least one of the incremental FPC, RPC (reverse power control) parameters and the lower limit of traffic channel gain as a function of the number of BTSs in a soft handoff mode with respect to said MS.

2. A method of attempting to synchronize BTS (base transceiver station) transmit powers of a cellular communication system to an MS (mobile station) when there are at least 2 BTSs listed in an active set of said MS comprising the steps of:

measuring the E_b/N_o (bit energy to noise density), at each of the BTSs listed in the active set of said MS, of reverse link FPC (forward power control) bit stream transmissions or pilot bit stream transmissions from said MS;

periodically comparing the measured E_b/N_o to determine which BTS is receiving the most reliable FPC data; and

instructing one or more active set BTSs, other than the BTS determined to be receiving the most reliable FPC data, to adjust the power level of transmissions from each of the one or more active BTSs to said MS to the level of the BTS determined to be receiving the most reliable FPC data from said MS.

15. The method of claim 2, wherein the instructing step further comprises instructing all active set BTSs, other than the BTS determined to be receiving the most reliable FPC data, to adjust the power level of transmissions from all active BTSs to said MS to the level of the BTS determined to be receiving the most reliable FPC data from said MS.

3. A method of attempting to synchronize BTS (base transceiver station) transmit powers of a cellular communication system to an MS (mobile station) when there are at least 2 BTSs receiving reverse link transmissions from said MS comprising the steps of:

measuring the E_b/N_o (bit energy to noise density), at each of the BTSs receiving reverse link transmissions from said MS, of reverse link FPC (forward power control) bit stream transmissions or pilot bit stream transmissions from said MS;

periodically comparing the measured E_b/N_o to determine which BTS is receiving the most reliable FPC data; and

instructing each BTS, other than the BTS determined to be receiving the most reliable FPC data, to adjust the power level of transmissions to said MS to the level of the BTS determined to be receiving the most reliable FPC data from said MS.

4. A method of attempting to synchronize BTS (base transceiver station) transmit powers of a cellular communication system to an MS (mobile station) when there are at least 2 BTSs receiving reverse link transmissions from said MS comprising the steps of:

measuring the E_b/N_o (bit energy to noise density), at each of the BTSs receiving reverse link transmissions from said MS, of reverse link FPC (forward power control) bit stream transmissions from said MS;

periodically comparing the measured E_b/N_o to determine which BTS is receiving the most reliable FPC data wherein the BTS determined to be is receiving the most reliable FPC data is designated hereinafter as BTS(x);

comparing the transmit power level of each BTS, other than BTS(x), with the transmit power level of BTS(x); and

instructing each BTS, other than BTS(x), whose power level differs from the transmit power level of BTS(x) by more than a predetermined value, to adjust the power level of transmissions to said MS to the level of BTS(x).

13. The method of claim 4, wherein each BTS, other than BTS(x), whose power level differs from the transmit power level of BTS(x) by more than a predetermined level, is instructed to synchronize the power level of transmissions to the level of BTS(x).

5. A method of adjusting power control parameters in a cellular communication system comprising the steps of:

determining the number of BTSs (base transceiver stations) in a soft handoff mode with respect to a MS (mobile station); and

adjusting at least one of the incremental FPC (forward power control) and RPC (reverse power control) parameters as a function of the number of BTSs in a soft handoff mode with respect to said MS, wherein the power control parameters comprise part of a fast forward power control function of the BTSs.

7. The method of claim 5 comprising the additional step of comprising the additional step of:

lowering a lower limit of traffic channel gain of a BTS (base transceiver station) as regards communications with a given MS (mobile station) when said given MS is not in a handoff mode.

8. The method of claim 5 comprising the additional step of:

adjusting the range between upper and lower limits of traffic channel gain of a BTS (base transceiver station) as regards communications with a given MS (mobile station) as a function of whether or not said given MS is in a handoff mode.

9. The method of claim 5 comprising the additional step of:

raising a lower limit of traffic channel gain of a BTS (base transceiver station) as regards communications with a given MS (mobile station) when said given MS is in a handoff mode as compared to the lower limit of the traffic channel gain of the BTS when said given MS is not in a handoff mode.

10. The method of claim 5 comprising the additional step of:

adjusting a lower limit of traffic channel gain of a BTS (base transceiver station) as regards communications with a given MS (mobile station) as a function of whether or not said given MS is in a handoff mode.

6. A method of adjusting power control parameters in a cellular communication system comprising the steps of:

determining the number of BTSs (base transceiver stations) in a soft handoff mode with respect to a MS (mobile station); and

adjusting at least one of the incremental FPC (forward power control) and RPC (reverse power control) parameters as a function of the number of BTSs in a soft handoff mode with respect to said MS, wherein the adjusting function comprises reducing the incremental value of FPC as the number of BTSs in a soft handoff mode with respect to said MS increases.

11. A cellular communication system incorporating fast forward power control and having at least 2 BTSs receiving reverse link transmissions from a MS (mobile station) comprising:

measuring means, comprising a part of each BTS in the system, for measuring a parameter, at each of the BTSs receiving reverse link transmissions from said MS, of reverse link FPC (forward power control) bit stream transmissions from said MS;

comparison means for periodically comparing the measured parameter to determine which BTS is receiving the most reliable FPC data wherein the BTS determined to be is receiving the most reliable FPC data is designated hereinafter as BTS(x);

further comparison means for comparing the transmit power level of each BTS, other than BTS(x), with the transmit power level of BTS(x); and

instructing means for instructing each BTS, other than BTS(x), whose power level differs from the transmit power level of BTS(x) by more than a predetermined value, to adjust the power level of transmissions to said MS to the level of BTS(x).

12. Apparatus as claimed in claim 11 where the parameter measured is E_bN_o (bit density).

14. The method of claim 11, wherein the instructing means instructs each BTS, other than BTS(x), whose power level differs from the transmit power level of BTS(x) by more than a predetermined value, to synchronize the power level of transmission to said MS to the level of BTS(x).