RF Repeater with delay to improve hard handoff performance

• US 6,507,741 B1
• Filed: 12/17/1997
• Issued: 01/14/2003
• Est. Priority Date: 12/17/1997
• Status: Expired due to Term

• Current Assignee: Blackberry Limited
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Bassirat, Farhad
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/992,588
• Time in Patent Office: 1,854 Days
• Field of Search: 455/7, 455/11.1, 455/12.1, 455/18, 455/436, 455/37, 455/40, 455/456, 455/443, 375/211, 370/279, 370/280, 370/281, 370/293, 370/320, 370/335, 370/342
• US Class Current: 455/440
• CPC Class Codes: H04B 7/15507 Relay station based processing for cell extension or control of coverage area, network planning with network coordinated processing with regard to cell extension H04W16/26; network topologies using dedicated repeater stations H04W84/047; terminal devices adapted for relaying to or from an other terminal H04W88/04
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 84/047 using dedicated repeater stations

Abstract

An RF repeater having a fixed or adjustable time delay inserted in the reverse path and/or forward path of the RF repeater is used in a first cell for improving hard handoff performance from the first cell to a second cell. Certain factors associated with the CDMA hard hand-off process effectively reduce the coverage area of the first cell, including the round-trip delay (RTD) uncertainty, the time needed to perform the hard hand-off process, and a higher forward link E_b/N_o requirement. Use of an RF repeater in accordance with the increases the effective coverage area of the first cell. The delayed signal from the RF repeater also allows the base station to determine the location of the subscriber station thereby identifying the particular adjacent cell to which the subscriber station will be switched (hard hand-off). A collocated base station is no longer required for the hard hand-off process and the utilization of beacons (when the source cell and the destination cell operate at different channel frequencies) is eliminated. The present invention further includes a method of adding a delay, using an RF repeater, to the reverse path and/or forward path signal(s) between a subscriber station and a base station.

Claims

1. A radio frequency (RF) base station and repeater system for assisting in the hand-off of a subscriber station from the base station, comprising:

(a) a repeater, further comprising input means for receiving a first signal from a subscriber station, the subscriber station being within a first cell containing at least one base station;

means for delaying the first signal by a predetermined amount of time; and

means for outputting the delayed first signal for transmission to the at least one base station, the delayed first signal being used to permit the subscriber station to be handed off to a second cell; and

(b) the at least one base station, further comprising;

means for receiving the delayed first signal;

means for recognizing the predetermined amount of time that the first signal is delayed; and

means for identifying the repeater from which the signal was received by the recognized predetermined delay.

2. An RF repeater in accordance with claim 1 wherein the means for delaying the first signal comprises a delay generator.

3. An RF repeater in accordance with claim 1 wherein the predetermined amount of time is adjustable.

4. An RF repeater in accordance with claim 1 further comprising:

means for receiving a second signal from the base station; and

means for delaying the second signal.

5. An RF repeater in accordance with claim 4 wherein the means for delaying the second signal comprises a delay generator.

6. An RF repeater in accordance with claim 1 wherein the cell operates using code division multiple access (CDMA) communications.

7. A radio frequency (RF) repeater comprising:

input means for receiving a first signal from a base station located in a first cell;

means for delaying the first signal by a predetermined amount of time, the predetermined amount of time of the delay identifiable by at least one base station in the first cell as identifying the repeater; and

means for outputting the delayed first signal for transmission to a subscriber station, the subscriber station being within the first cell and the predetermined amount of time delay of the delayed first signal being used to identify the repeater and thereby permit the subscriber station to be handed off to a second cell.

8. An RF repeater in accordance with claim 7 wherein the means for delaying the first signal comprises a delay generator.

9. An RF repeater in accordance with claim 7 wherein the predetermined amount of time is adjustable.

10. An RF repeater in accordance with claim 7 further comprising:

input means for receiving a second signal from the subscriber station; and

means for delaying the second signal by a predetermined amount of time.

11. An RF repeater in accordance with claim 10 wherein the means for delaying the second signal comprises a delay generator.

12. An RF repeater in accordance with claim 7 wherein communications between the subscriber station and the base station are code division multiple access (CDMA) communications.

13. An apparatus for delaying an radio frequency (RF) signal between a subscriber station and a base station comprising:

an RF repeater, operable with a base station within a first cell, for receiving an RF signal from a subscriber station and for transmitting the RF signal to the base station; and

means, electrically coupled to the RF repeater, for delaying the RF signal by a predetermined amount of time, the predetermined amount of time of the delay identifying the repeater to the base station with which the repeater operates, the delayed first signal being used to permit the subscriber station to be handed off to a second cell.

14. An apparatus in accordance with claim 13 wherein the means for delaying the RF signal comprises a delay generator.

15. An apparatus in accordance with claim 13 wherein the predetermined amount of time is adjustable.

16. An RF repeater in accordance with claim 13 wherein the RF repeater receives a second RF signal from the base station and transmits the second RF signal to the subscriber station, and the means for delaying delays the second RF signal by a predetermined amount.

17. An RF repeater in accordance with claim 13 wherein communications between the subscriber station and the base station are code division multiple access (CDMA) communications.

18. An apparatus for delaying a radio frequency (RF) signal between a subscriber station and a base station comprising:

an RF repeater, operable with a base station within a first cell, for receiving an RF signal from the base station and for transmitting the RF signal to a subscriber station; and

means, electrically coupled to the RF repeater, for delaying the RF signal by a predetermined amount of time, the predetermined amount of time of the delay identifying the repeater to the subscriber station, the delayed RF signal being used to permit the subscriber station to be handed off to a second cell.

19. An apparatus in accordance with claim 18 wherein the means for delaying the RF signal comprises a delay generator.

20. An RF repeater in accordance with claim 19 wherein communications between the subscriber station and the base station are code division multiple access (CDMA) communications.

21. A communications cell utilizing CDMA technology, comprising:

a first cell having a base station emitting a base station signal for communicating with a subscriber station within a predetermined geographic area, the subscriber station emitting a first signal; and

a radio frequency (RF) repeater operable with the base station and located proximate a boundary of the predetermined geographic area, the RF repeater comprising,

input means for receiving a first signal from the subscriber station,

means for delaying the first signal by a predetermined amount of time, and

means for outputting the delayed first signal for transmission to the base station, the predetermined amount of time of the delay of the transmission being recognized by the base station as identifying the repeater, the delayed first signal being used to permit the subscriber station to be handed off to a second cell.

22. A communications cell in accordance with claim 21 wherein the base station receives the delayed first signal from the RF repeater and determines from the delayed first signal that the subscriber station is proximate a second cell having a base station operating at a frequency different from the frequency of operation of the base station of the first cell.

23. communications cell in accordance with claim 21 wherein the base station receives the first signal from subscriber station and initiates a process for handing off the subscriber station from the first cell to the second cell when the signal strength of the received delayed first signal exceeds the signal strength of the received first signal.

24. A method of improving hand-off performance from a first cell to a second cell, comprising the steps of:

receiving at a radio frequency (RF) repeater a first CDMA signal from a subscriber station, the repeater being operable with a base station and located near a cell boundary of the first cell;

delaying the first CDMA signal by a predetermined amount of time; and

outputting the delayed first CDMA signal for transmission to the base station; and

the predetermined amount of time of the delay of the first signal being used to provide information to the base station concerning the location of the subscriber station, thereby the delayed first signal being used to permit the subscriber station to be handed off to the second cell.

25. A method in accordance with claim 24 further comprising the step of determining from the delayed first signal that the subscriber station is located proximate the second cell having a base station operating at a frequency different from the frequency of operation of the base station of the first cell.

26. A method in accordance with claim 24 further comprising the steps of:

receiving at the base station the first signal from the subscriber station;

receiving at the base station the delayed first signal from the RF repeater; and

initiating a process for handing off the subscriber station from the first cell to the second cell when the signal strength of the received delayed first signal exceeds the signal strength of the received first signal, wherein the delay of the first signal is used to provide information concerning the location of the subscriber station.

27. A method in accordance with claim 26 wherein communications between the subscriber station and the base station are code division multiple access (CDMA) communications.

28. An apparatus for improving hand-off performance from a first cell to a second cell, comprising the steps of:

means for receiving at a radio frequency (RF) repeater operable with a base station a first signal from a subscriber station;

means for delaying the first signal by a predetermined amount of time; and

means for outputting the delayed first signal for transmission to the base station, the predetermined amount of time of the delay of the first signal being used to provide information to the base station concerning the location of the subscriber station and the delayed first signal being used to permit the subscriber station to be handed off from the first cell to the second cell.

29. A method of defining the location of a subscriber station located within a cell or near the boundary of the cell, comprising the steps of:

receiving at a radio frequency (RF) repeater operable with a base station of the cell a first signal from a subscriber station;

delaying the first signal by a predetermined amount of time;

outputting the delayed first signal for transmission to the base station;

receiving at the base station the delayed first signal from the RF repeater; and

determining from the predetermined amount of time of the signal delay the identity of the repeater, thereby deriving the location of the subscriber station from the received delayed first signal.

30. A method of increasing the effective coverage of a cell for hard hand-offs, comprising the steps of:

deploying a radio frequency (RF) repeater proximate the cell boundary of the cell, the RF repeater operable with a base station located within the cell;

receiving at the RF repeater a first signal from a subscriber station;

delaying the first signal by a predetermined amount of time; and

outputting the delayed first signal for transmission to the base station;

receiving at the base station the delayed first signal from the RF repeater; and

measuring the delayed first signal to determine the location of the repeater, the subscriber station and whether a hand-off should be performed,

thereby increasing the effective coverage area of the cell.

31. A method of communicating with a subscriber station located proximate the boundary of a cell, comprising the steps of:

receiving at a radio frequency (RF) repeater operable with a base station within the cell a first signal from a subscriber station;

delaying the first signal by a predetermined amount of time, the predetermined amount of time identifying the repeater to the base station;

outputting the delayed first signal for transmission to the base station; and

determining the location of the subscriber station using the delay of the first signal.

32. A radio frequency (RF) repeater comprising:

input means for receiving a first signal transmitted by a subscriber station directly to a base station, the subscriber station being within a cell containing the base station;

means for delaying the first signal by a predetermined amount of time t₁ associated with the repeater; and

means for transmitting the delayed first signal to the base station, the predetermined amount of time t₁ being determined by the base station and used to identify the repeater and determine the approximate location of the subscriber station.