Relative future activity indicators for assisting in selecting the source of received communications

• US 20030013454A1
• Filed: 03/11/2002
• Published: 01/16/2003
• Est. Priority Date: 03/09/2001
• Status: Active Grant

• Current Assignee: Beijing Xiaomi Mobile Software Co., Ltd. (Xiaomi Corp.)
• Original Assignee: DENSO Corporation
• Inventors: Hunzinger, Jason F.
• Granted Patent: US 6,834,194 B2
• Time in Patent Office: Days
• US Class Current: 455/452.1
• CPC Class Codes: H04W 48/20 Selecting an access point

Abstract

A method and apparatus is disclosed for providing network access point differential future activity indicator (FAI) bits which includes the direction and magnitude of predicted future activity relative to current activity levels to enable a mobile station (MS) to select a preferred network access point. The network access point computes a predicted future change in activity ΔA′(t+1) as future predicted activity A′(t+1) minus current actual activity A(t). The predicted future change in activity is translated into FAI bits, which are transmitted to the MS. The FAI bits are also an indication of the expected change in the pilot strength ΔPS′_s(t+1) for a BS/sector. The MS measures the pilot strengths PS_s(t) of sectors, then biases these pilot strengths using ΔPS′_s(t+1) to compute a predicted future pilot strength PS′_s(t+1)=PS_s(t)+ΔPS′_s(t+1) for each sector. The MS then uses the PS′_s(t+1) values to choose the best eligible sector.

Claims

1. In a system comprising a plurality of base stations (BSs) and a plurality of mobile stations (MSs) communicatively couplable for establishing connections and maintaining communication channels between them, each BS and MS in the system capable of acting as a transmitting entity and a receiving entity, at least one receiving entity for maintaining an eligible set of transmitting entities with which a communication link may be established, a method for enabling at least one receiving entity to select a transmitting entity from the eligible set for establishing a communication link, comprising:

receiving at a receiving entity one or more differential future activity indicator (FAI) bits from one or more transmitting entities in an eligible set of the receiving entity, the one or more FAI bits from the one or more transmitting entities providing an indication of a predicted future change in activity Δ

A′

(t+1) relative to a current activity level for a particular transmitting entity;

for one or more of the transmitting entities in the eligible set,

deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the, one or more FAI bits,

determining a current pilot strength, and

computing a predicted future pilot strength for a next time period PS′

_s(t+1) by adding the expected change in pilot strength Δ

PS′

_s(t+1) to the current pilot strength; and

selecting one or more transmitting entities from the one or more transmitting entities in the eligible set for establishing a communication link based on the predicted future pilot strengths PS′

_s(t+1).

2. The method as recited in claim 1, wherein the indication of a predicted future change in activity relative to a current activity level provided by the one or more FAI bits comprises an indication of a directional change in activity.

3. The method as recited in claim 2, wherein the indication of a predicted future change in activity relative to a current activity level provided by the one or more FAI bits comprises an indication of a magnitude of the change in activity.

4. The method as recited in claim 3, wherein a value of the one or more FAI bits comprises a direct indicator of a magnitude and direction of the predicted future change in activity.

5. The method as recited in claim 1, wherein prior to the step of deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits, for those transmitting entities in the eligible set from which no FAI bits are received, the method further comprises assigning default FAI bits indicating no change activity.

6. The method as recited in claim 1, wherein prior to the step of deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits, for those transmitting entities in the eligible set from which no FAI bits are received, the method further comprises assigning default FAI bits indicating no estimate for predicted future change in activity is available.

7. The method as recited in claim 1, wherein prior to the step of deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits, for those transmitting entities in the eligible set from which no FAI bits are received, the method further comprises assigning FAI bits indicating a particular predicted future change in activity in accordance with information maintained by the receiving entity.

8. The method as recited in claim 3, wherein a value of the one or more FAI bits comprises an indirect indicator capable of being mapped to a stored magnitude and direction of the predicted future change in activity.

9. The method as recited in claim 1, the step of determining a current pilot strength comprising measuring a pilot strength PS_s(t) at the receiving entity, and using the measured pilot strength PS_s(t) as the current pilot strength.

10. The method as recited in claim 1, the step of determining a current pilot strength comprising:

measuring a pilot strength PS_s(t) at the receiving entity; and

applying historical pilot strength results stored in the receiving entity to the measured pilot strength PS_s(t) to determine an updated future pilot strength PS″

_s(t+1), and using the updated future pilot strength PS″

_s(t+1) as the current pilot strength.

11. The method as recited in claim 1, wherein prior to computing a predicted future pilot strength for a next time period PS′

_s(t+1), the method further comprises, for each of the one or more transmitting entities in the eligible set that transmitted the one or more FAI bits;

recalling a measured pilot strength PS_s(t−

1) and one or more FAI bits representing a future activity level A′

_s(t−

1) from a previous time period, and deriving an expected change in pilot strength Δ

PS′

_s(t) for the previous time period from the recalled one or more FAI bits;

computing an actual change in pilot strength Δ

PS_s(t) during the previous time period by subtracting the measured pilot strength during the previous time period PS_s(t−

1) from the current pilot strength PS_s(t);

computing a correlation value for the actual change in pilot strength Δ

PS_s(t) and the expected change in pilot strength Δ

PS′

_s(t); and

biasing the expected change in pilot strength Δ

PS′

_s(t+1) in accordance with the computed correlation value.

12. The method as recited in claim 11, wherein prior to biasing the expected change in pilot strength Δ

PS′

_s(t) with the correlation value, the method further comprises filtering the correlation value using previously derived correlation values.

13. The method as recited in claim 12, further comprising normalizing the filtered correlation values.

14. The method as recited in claim 11, wherein the step of biasing the expected change in pilot strength Δ

PS′

_s(t+1) in accordance with the computed correlation value comprises leaving the expected change in pilot strength Δ

PS′

_s(t+1) unchanged if the computed correlation value indicates poor accuracy of the recalled one or more FAI bits from the previous time period.

15. The method as recited in claim 1, wherein prior to the step of receiving the one or more FAI bits at the receiving entity, at each of one or more transmitting entities in the eligible set that transmitted the one or more FAI bits the method further comprises:

determining a current activity level A(t);

determining an expectation of future transmissions and generating a predicted future activity A′

(t+1);

computing a predicted future change in activity Δ

A′

(t+1) by subtracting the current activity level A(t) from the predicted future activity A′

(t+1);

translating the predicted future change in activity Δ

A′

(t+1) into the one or more FAI bits and transmitting the one or more FAI bits to the receiving entity.

16. The method as recited in claim 15 wherein, for each of the one or more transmitting entities in the eligible set that transmitted the one or more FAI bits, the method further comprises:

recalling a future activity level A′

(t) from a previous time period;

computing a prediction error Δ

A(t) representing a difference between current and predicted activity by subtracting the future activity level A′

(t) during the previous time period from the current activity level A(t); and

adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t).

17. The method as recited in claim 16, wherein for each of the one or more transmitting entities in the eligible set that transmitted the one or more FAI bits, prior to the step of adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t), the method further comprises filtering the prediction error Δ

A(t) using previously derived Δ

A(t) values.

18. The method as recited in claim 16, the step of adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t) comprising adding the prediction error Δ

A(t) to the predicted future activity A′

(t+1).

19. The method as recited in claim 17, the step of adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t) comprising limiting the predicted future activity A′

(t+1) to a range of values established by past Δ

A(t) values.

20. A first transceiver communicatively couplable to one or more second transceivers for establishing a connection and maintaining a communication channel with the one or more second transceivers, the first transceiver configured as a receiving entity for maintaining an eligible set of one or more second transceivers with which a communication link may be established, the first transceiver comprising:

a first transceiver processor programmed for

receiving one or more differential future activity indicator (FAI) bits from one or more second transceivers in an eligible set of the first transceiver, the one or more FAI bits from the one or more second transceivers providing an indication of a predicted future change in activity Δ

A′

(t+1) relative to a current activity level for a particular second transceiver;

for one or more of the second transceivers in the eligible set,

deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits,

determining a current pilot strength, and

computing a predicted future pilot strength for a next time period PS′

_s(t+1) by adding the expected change in pilot strength Δ

PS′

_s(t+1) to the current pilot strength; and

selecting one or more second transceivers from the one or more second transceivers in the eligible set for establishing a communication link based on the predicted future pilot strengths PS′

_s(t+1).

21. The first transceiver as recited in claim 20, wherein the indication of a predicted future change in activity relative to a current activity level provided by the one or more FAI bits comprises an indication of a directional change in activity.

22. The first transceiver as recited in claim 21, wherein the indication of a predicted future change in activity relative to a current activity level provided by the one or more FAI bits comprises an indication of a magnitude of the change in activity.

23. The first transceiver as recited in claim 22, wherein a value of the one or more FAI bits comprises a direct indicator of a magnitude and direction of the predicted future change in activity.

24. The first transceiver as recited in claim 20, wherein prior to deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits, for those second transceivers in the eligible set from which no FAI bits are received, the first transceiver processor is further programmed for assigning default FAI bits indicating no change activity.

25. The first transceiver as recited in claim 20, wherein prior to deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits, for those second transceivers in the eligible set from which no FAI bits are received, the first transceiver processor is further programmed for assigning default FAI bits indicating no estimate for predicted future change in activity is available.

26. The first transceiver as recited in claim 20, wherein prior to the deriving an expected change in pilot strength Δ

PS′

_s(t+1) from the one or more FAI bits, for those second transceivers in the eligible set from which no FAI bits are received, the first transceiver processor is further programmed for assigning FAI bits indicating a particular predicted future change in activity in accordance with information maintained by the first transceiver.

27. The first transceiver as recited in claim 22, wherein a value of the one or more FAI bits comprises an indirect indicator capable of being mapped to a stored magnitude and direction of the predicted future change in activity.

28. The first transceiver as recited in claim 20, the first transceiver processor further programmed for determining the current pilot strength by measuring a pilot strength PS_s(t) at the first transceiver, and using the measured pilot strength PS_s(t) as the current pilot strength.

29. The first transceiver as recited in claim 20, wherein for each of the one or more second transceivers in the eligible set that transmitted the one or more FAM bits, the first transceiver processor is further programmed for determining the current pilot strength by:

measuring a pilot strength PS_s(t) at the first transceiver; and

applying historical pilot strength results stored in the first transceiver to the measured pilot strength PS_s(t) to determine an updated future pilot strength PS″

_s(t+1), and using the updated future pilot strength PS″

_s(t+1) as the current pilot strength.

30. The first transceiver as recited in claim 20, wherein for each of the one or more second transceivers in the eligible set that transmitted the one or more FAI bits, prior to adding the expected change in pilot strength Δ

PS′

_s(t+1) to the current pilot strength to compute a predicted future pilot strength for the next time period PS′

_s(t+1), the first transceiver processor is further programmed for;

recalling a measured pilot strength PS_s(t−

1) and one or more FAI bits representing a future activity level A′

(t−

1) from a previous time period, and deriving an expected change in pilot strength Δ

PS′

_s(t) for the previous time period from the recalled one or more FAI bits;

computing an actual change in pilot strength Δ

PS_s(t) during the previous time period by subtracting the measured pilot strength during the previous time period PS_s(t−

1) from the current pilot strength PS_s(t);

computing a correlation value for the actual change in pilot strength Δ

PS_s(t) and the expected change in pilot strength Δ

PS′

_s(t); and

biasing the expected change in pilot strength Δ

PS′

_s(t+1) in accordance with the computed correlation value.

31. The first transceiver as recited in claim 30, wherein prior to biasing the expected change in pilot strength Δ

PS′

_s(t) with the correlation value, the first transceiver processor is further programmed for filtering the correlation value using previously derived correlation values.

32. The first transceiver as recited in claim 31, the first transceiver processor further programmed for normalizing the filtered correlation values.

33. The first transceiver as recited in claim 30, wherein the first transceiver processor is further programmed for biasing the expected change in pilot strength Δ

PS′

_s(t+1) in accordance with the computed correlation value by leaving the expected change in pilot strength Δ

PS′

_s(t+1) unchanged if the computed correlation value indicates poor accuracy of the recalled one or more FAI bits from the previous time period.

35. The second transceiver as recited in claim 34, the second transceiver processor further programmed for:

recalling a future activity level A′

(t) for the second transceiver from a previous time period;

computing a prediction error Δ

A(t) representing a difference between current and predicted activity for the second transceiver by subtracting the future activity level A′

(t) during the previous time period from the current activity level A(t); and

adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t).

36. The second transceiver as recited in claim 35, wherein prior to adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t), the second transceiver processor is further programmed for filtering the prediction error Δ

A(t) using previously derived Δ

A(t) values.

37. The second transceiver as recited in claim 35, the second transceiver processor further programmed for adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t) by adding the prediction error Δ

A(t) to the predicted future activity A′

(t+1).

38. The second transceiver as recited in claim 36, the second transceiver processor further programmed for adjusting the predicted future activity A′

(t+1) by the prediction error Δ

A(t) by limiting the predicted future activity A′

(t+1) to a range of values established by past Δ

A(t) values.

34. A second transceiver communicatively couplable to a first transceiver for establishing a connection and maintaining a communication channel with the first transceiver, the first transceiver configured as a receiving entity for maintaining an eligible set of one or more second transceivers with which a communication link may be established;

the second transceiver configured as a transmitting entity for assisting in the first transceiver'"'"'s selection of one second transceiver from the eligible set for establishing a communication link, the second transceiver comprising;

a second transceiver processor programmed for

determining a current activity level A(t) for the second transceiver;

determining an expectation of future transmissions and generating a predicted future activity A′

(t+1) for the second transceiver;

computing a predicted future change in activity Δ

A′

(t+1) for the second transceiver by subtracting the current activity level A(t) from the predicted future activity A′

(t+1);

translating the predicted future change in activity Δ

A′

(t+1) into the one or more FAI bits and transmitting the one or more FAI bits to the first transceiver.