Method and apparatus for determining coverage and switching between overlay communication systems

• US 7,450,943 B2
• Filed: 02/12/2003
• Issued: 11/11/2008
• Est. Priority Date: 02/12/2003
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rezaiifar, Ramin, Black, Peter J., Ekvetchavit, Thunyachate
• Primary Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US10/366,101
• Publication Number:
  US 20040157610A1
• Time in Patent Office: 2,099 Days
• Field of Search: 455/414.1, 455/417, 455/421, 455/422.1, 455436-439, 455/440, 455/525, 455/550.1, 455/552.1, 455/553.1, 455/168.1, 455/42.3, 455/67.11, 370/332, 370/252, 370/345
• US Class Current: 455/436
• CPC Class Codes: H04W 36/144 over a different radio air interface technology
• CPC Class Codes: H04W 36/302 due to low signal strength

Abstract

Techniques to determine whether or not a terminal is under the coverage of a current wireless communication system (e.g., a packet data system) and to switch from the current system to another wireless communication system (e.g., a voice/data system). In one method, at least one measurement of at least one parameter for at least one base station in the current system is initially obtained. The measurement(s) may be SNR measurements. A metric is derived based on the measurement(s) and used (typically along with a metric threshold and a timer) to determine whether or not the terminal is within the coverage of the current system. A switch to another system is initiated if the terminal is deemed to be outside the coverage of the current system. The two systems provide at least one common service (e.g., packet data service).

Claims

1. A method of switching a terminal from a first wireless cdma communication system to a second cdma wireless communication system, comprising:

obtaining at least one measurement of at least one parameter for at least one base station in the first cdma communication system;

deriving a metric based on the at least one measurement;

determining whether or not the terminal is within coverage of the first cdma communication system based on the metric; and

initiating a switch to the second cdma communication system if the terminal is deemed to be outside the coverage of the first cdma communication system, wherein said metric is derived using one of the following formulae;

(a) metric=Sum of E_C/I₀ of all pilots in the active and candidate sets and Max {E_C/I₀ of pilots inthe neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference,

(b) metric=Sum of E_C/I₀ of all pilots in the active set and Max {E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference,

(c) metric=Max {sum of E_C/I₀ of pilots in the active set, E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference, and

(d) metric=Max {E_C/I₀ of pilots in the active, candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference.

2. The method of claim 1, wherein the switch to the second cdma communication system is initiated only if at least one signal of sufficient signal quality is received from the second cdma communication system.

3. The method of claim 1, wherein the metric is derived based on quality of signals received by the terminal from base stations in the first cdma communication system.

4. The method of claim 1, wherein the metric is derived based on quality of signals received by the terminal from base stations in one or more sets selected from an active set, a candidate set, and a neighbor set.

5. The method of claim 1, wherein the determining is further based on a metric threshold.

6. The method of claim 5, wherein the metric threshold is a fixed value.

7. The method of claim 5, wherein the metric threshold is an adaptive value.

8. The method of claim 5, wherein the metric threshold is determined based on one or more measurements obtained for the second cdma communication system.

9. The method of claim 5, wherein the determining is further based on a timer.

10. The method of claim 9, wherein the terminal is deemed to be outside the coverage of the first cdma communication system if the metric is below the metric threshold for the duration of the timer.

11. The method of claim 10, wherein the timer duration is an adaptive value.

12. The method of claim 11, wherein the timer duration is determined based on one or more measurements obtained for the first cdma communication system.

13. The method of claim 1, wherein the switch is initiated only if at least one base station in the second cdma communication system is received by the terminal with sufficient signal quality.

14. The method of claim 1, wherein the first and second cdma communication systems provide at least one common service.

15. The method of claim 1, wherein the at least one common service includes packet data service.

16. The method of claim 1, wherein the first cdma communication system is an IS-856 system and the second cdma communication system is a cdma2000 system.

17. The method of claim 1, wherein said metric is derived based on a sum of the at least one signal quality measurement.

18. The method of claim 1, wherein said metric is derived based on a maximum of the at least one signal quality measurement.

19. The method according to claim 1, wherein said metric is derived based on a maximum and a sum of a signal-to-noise ratio of the at least one measurement of at least one pilot in active, candidate and neighbor sets.

20. A terminal comprising:

a metric computation unit operative to receive at least one measurement of at least one parameter for at least one base station in a first cdma wireless communication system and to derive a metric based on the at least one measurement;

a coverage determination unit operative to determine whether or not the terminal is within coverage of the first cdma communication system based on the metric; and

a controller operative to initiate a switch to a cdma second wireless communication system if the terminal is deemed to be outside the coverage of the first cdma communication system, wherein said metric is derived using one of the following formulae;

(a) metric=Sum of E_C/I₀ of all pilots in the active and candidate sets and Max {I E_C/I₀ of pilots in the neighbor sets}. wherein said E_C represents energy-per-chip, and I₀ represents noise and interference,

(b) metric=Sum of E_C/I₀ of all pilots in the active set and Max {E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference

(c) metric=Max {sum of E_C/I₀ of pilots in the active set, E_C/I₀ of pilots in the candidate and neighbor sets}. wherein said E_C represents energy-per-chip, and I₀ represents noise and interference, and

(d) metric=Max {E_C/I₀ of pilots in the active, candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference.

21. The terminal of claim 20, wherein the metric relates to an active set that includes base stations in the first cdma communication system received by the terminal with sufficient signal quality.

22. The terminal of claim 20, wherein the metric is derived based on quality of signals received by the terminal from base stations in one or more sets selected from an active set, a candidate set, and a neighbor set.

23. The terminal of claim 20, wherein said metric is derived based on a sum of the at least one measurement.

24. The terminal of claim 20, wherein said metric is derived based on a maximum of the at least one measurement.

25. The terminal according to claim 20, wherein said metric is derived based on a maximum and a sum of a signal-to-noise ratio of the at least one measurement of at least one pilot in active, candidate and neighbor sets.

26. An apparatus comprising:

means for obtaining at least one measurement of at least one parameter for at least one base station in a first cdma wireless communication system;

means for deriving a metric based on the at least one measurement;

means for determining whether or not the terminal is within coverage of the first cdma communication system based on the metric; and

means for initiating a switch to a second wireless communication system if the terminal is deemed to be outside the coverage of the first cdma communication system, wherein said metric is derived using one of the following formulae;

(a) metric=Sum of E_C/I₀ of all pilots in the active and candidate sets and Max {E_C/I₀ of pilots in the neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference,

(b) metric=Sum of E_C/I₀ of all pilots in the active set and Max {E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference

(c) metric=Max {sum of E_C/I₀ of pilots in the active set, E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference, and

(d) metric=Max {E_C/I₀ of pilots in the active, candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference.

27. The apparatus of claim 26, wherein said metric s derived based on a sum of the at least one measurement.

28. The apparatus of claim 26, wherein said metric is derived based on a maximum of the at least one measurement.

29. The method according to claim 26, wherein said metric is derived based on a maximum and a sum of a signal-to-noise ratio of the at least one measurement of at least one pilot in active, candidate and neighbor sets.

30. A memory communicatively coupled to a digital signal processing device (DSPD) capable of interpreting digital information to:

receive at least one measurement of at least one parameter for at least one base station in a first cdma wireless communication system;

derive a metric based on the at least one measurement;

determine whether or not a terminal is within coverage of the first cdma communication system based on the metric; and

initiate a switch to a second cdma wireless communication system if the terminal is deemed to be outside the coverage of the first cdma communication system, wherein said metric is derived using one of the following formulae;

(a) metric=Sum of E_C/I₀ of all pilots in the active and candidate sets and Max {E_C/I₀ of pilots in the neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference,

(b) metric=Sum of E_C/I₀ of all pilots in the active set and Max {E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference,

(c) metric=Max {sum of E_C/I₀ of pilots in the active set, E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference, and

(d) metric=Max {E_C/I₀ of pilots in the active, candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference.

31. The memory of claim 30, wherein said metric s derived based on a sum of the at least one measurement.

32. The memory of claim 30, wherein said metric is derived based on a maximum of the at least one measurement.

33. The method according to claim 30, wherein said metric is derived based on a maximum and a sum of a signal-to-noise ratio of the at least one measurement of at least one pilot in active, candidate and neighbor sets.

34. A method of determining coverage for a terminal in a wireless communication system, comprising:

obtaining at least one signal quality measurement for at least one base station in the wireless communication system;

deriving a metric based on a maximum of the at least one signal quality measurement; and

determining whether or not the terminal is within coverage of the wireless communication system based on the metric, wherein said metric is derived using one of the following formulae;

(a) metric=Sum of E_C/I₀ of all pilots in the active and candidate sets and Max {E_C/I₀ of pilots in the neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference

(b) metric=Max E_C/I₀ of pilots in the active, candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference

(c) metric=Sum of E_C/I₀ of all pilots in the active set and Max {E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference, and

(d) metric=Max sum of E_C/I₀ of pilots in the active set, E_C/I₀ of pilots in the candidate and neighbor sets}, wherein said E_C represents energy-per-chip, and I₀ represents noise and interference.

35. The method of claim 34, wherein the metric is derived based on signal quality measurements for base stations in one or more sets selected from an active set, a candidate set, and a neighbor set.

36. The method of claim 34, wherein said step of deriving a metric based on a maximum of the at least one signal quality measurement further comprises deriving the metric based on a sum of the at least one signal quality measurement.

37. The method of claim 34, wherein said step of deriving a metric based on a maximum of the at least one signal quality measurement further comprises deriving said metric based on a maximum of a signal-to-noise ratio of at least one pilot in active, candidate and neighbor sets.

38. The method of claim 34, wherein the terminal is deemed to be outside the coverage of the wireless communication system if the metric is below a metric threshold for the duration of a timer.