Determining a handoff metric
View Patent ↗A method and apparatus of determining a hand-off metric is disclosed. One method includes a subscriber receiving identifications of a neighboring set of base stations from a serving base station. From the neighboring set, the subscriber determines an active set of base stations. The active set is determined by the subscriber measuring received signal power from each of the base stations of the neighboring set at first discrete points in time, averaging the received signal power for each of the base stations of the neighboring set, and selecting the active set based on the average received signal power of the base stations of the neighboring set. Determining the at least one hand-off metric further includes the subscriber measuring at second discrete points in time an excess received signal power for each base station of the active set, wherein the excess received signal power includes signal power received by the subscriber in excess of power received from the base station. The subscriber averages the excess received signal power. The subscriber calculates the hand-off metric by calculating a ratio of average receive signal power to average excess received signal power, for each base station of the active set.
1. A method of determining a hand-off metric, comprising:
determining, by a mobile station, an active set of base stations, comprising:
measuring received signal power from each base stations of a neighboring set of base stations at first discrete points in time,
averaging the received signal power for each of the base stations of the neighboring set, and
selecting the active set based on the average received signal power of the base stations of the neighboring set;
measuring, by the mobile station at second discrete points in time, an excess received signal power for each base station of the active set, wherein the excess received signal power comprises signal power received in excess of power received from the base station;
averaging, by the mobile station, the excess received signal power; and
determining, by the mobile station, the hand-off metric by calculating a ratio of average receive signal power to average excess received signal power, for each base station of the active set.
2. The method of claim 1 , further comprising selecting a transmitting mode based on the hand-off metric, wherein the transmitting mode is one of in a partial usage of sub-carriers mode and an adjacent sub-carrier within band allocation mode.
3. The method of claim 1 , wherein at least one of the first discrete points in time and the second discrete points in time are determined discrete points in time.
4. The method of claim 1 , wherein the first discrete points in time and the second discrete points in time are determined discrete points in time that are substantially the same.
5. The method of claim 3 , wherein the determined discrete points in time are based on occurrences of preamble symbols of signals received from the active set of base stations.
6. The method of claim 3 , wherein the determined discrete points in time are based on occurrences of downlink frames of signals received from the active set of base stations.
7. The method of claim 3 , wherein the determined discrete points in time occur at a rate that is dependent on a Doppler frequency measured by the mobile station.
8. The method of claim 7 , wherein the rate increases as the Doppler frequency increases, and the rate decreases as the Doppler frequency decreases.
9. The method of claim 1 , further comprising interlacing the measurements of the received signal power from the base stations in the neighboring set.
10. The method of claim 9 , wherein the interlacing comprises time interleaving the received signal power measurements of the base stations in the neighboring set.
11. The method of claim 9 , wherein the interlacing comprises periodically cycling the received signal power measurements of the base stations in the neighboring set.
12. The method of claim 1 , further comprising interlacing the measurements of the excess received signal power for the base stations in the active set.
13. The method of claim 1 , wherein the selecting the active set is based on a relative variation of the average received signal power.
14. The method of claim 1 , wherein the selecting the active set is based on an absolute average received signal power.
15. The method of claim 1 , wherein the selecting the active set is based on the average received signal power exceeding a threshold.
16. The method of claim 1 , wherein the averaging the received signal power and averaging the excess received signal power comprises at least one of IIR and FIR filtering of the received signal power and the excess received signal power.
17. The method of claim 1 , further comprising identifying one or more base stations in the neighboring set based on corresponding PRBS (pseudo random bit sequences).
18. The method of claim 1 , further comprising:
measuring a total received signal power by computing a sum square of an FFT (Fast Fourier Transform) over a set of frequency tones the represent a segment of a downlink signal preamble;
determining the received signal power at a discrete point in time by determining a difference between the total received signal power and a sum of received signal correlation indicators from all base stations except a desired base station;
determining the excess received signal power at the discrete point in time by determining a difference between the total received signal power and a received signal correlation indicator associated with the desired base station;
averaging the received signal power over time;
averaging the excess received signal power over time; and
computing a handoff metric associated with the desired base station by computing a ratio of the average received signal power to the average excess received signal power.
19. A method of determining a hand-off metric, comprising:
determining, by a mobile station, an active set of base stations, comprising:
measuring received signal power from each base station of a neighboring set of base stations at first discrete points in time,
averaging the received signal power for each of the base stations of the neighboring set, and
selecting the active set based on the average received signal power of the base stations of the neighboring set;
measuring, by the mobile station at second discrete points in time, a signal interference for each base station of the active set;
averaging, by the mobile station, the signal interference; and
determining, by the mobile station, the hand-off metric by calculating a ratio of average receive signal power to signal interference, for each base station of the active set.
20. The method of claim 19 , further comprising:
measuring a total received signal power by computing a sum square of an FFT (Fast Fourier Transform) over a set of frequency tones that represent a segment of a downlink signal preamble;
determining the received signal power at a discrete point in time by determining a difference between the total received signal power and a sum of received signal correlation indicators from all base stations except a desired base station;
determining the signal interference at the discrete point in time by determining a difference between the total received signal power and a received signal correlation indicator associated with the desired base station;
averaging the received signal power over time;
averaging the signal interference over time; and
computing a handoff metric associated with the desired base station by computing a ratio of the average received signal power to the average interference.