Method for performing measurements for handoff of a mobile unit operating with a switched beam antenna in a wireless communication system, and corresponding system
Measurements for handoff are made by a wireless transmit/receive unit (WTRU) operating with a switched beam antenna in a wireless communication system. The switched beam antenna is a smart antenna generating a plurality of directional beams and an omni-directional beam. The WTRU measures signals from a plurality of cells with the omni-directional beam and/or one or more of the directional beams. The WTRU evaluates and reports to the network measurement of the omni-directional beam or the strongest beam for adding cells to an active set of cells. For removing cells from an active set of cells, the WTRU evaluates and reports to the network measurements of the antenna beam selected for communication with the active set cells.
1. A method for operating a wireless transmit/receive unit (WTRU) in a wireless communication system comprising a plurality of cells, the WTRU comprising a switched beam antenna for generating antenna beams including a plurality of directional beams and an omni-directional beam, the method comprising:
using a selected beam for exchanging data with a cell in an active set of cells;
selecting a respective subset of antenna beams for each cell in the active set of cells and for each cell in a candidate set of cells;
receiving signals from cells in the active set of cells and from cells in the candidate set of cells using the respective subset of antenna beams;
measuring the received signals from each cell for each respective subset of antenna beams;
selecting the measured signal having the highest value from each cell in the active set of cells and in the candidate set of cells;
comparing the selected measured signals; and
sending a measurement report to the network when the selected measured signals for a cell in the candidate set of cells exceeds a reporting threshold criteria when compared to the selected measured signals for a cell in the active set of cells.
2. A method according to claim 1 wherein the reporting threshold criteria comprises at least one of a fixed threshold, or threshold based upon the measured signals, and a threshold based upon a plurality of parameters occurring during a predetermined time interval.
3. A method according to claim 1 wherein the respective subsets of antenna beams are different for each cell.
4. A method according to claim 1 wherein the respective subsets of antenna beams are the same for each cell.
5. A method according to claim 1 wherein the respective subsets of antenna beams are selected based upon location of the cells.
6. A method according to claim 1 wherein the respective subsets of antenna beams are selected based upon previous measurements of the cells.
7. A method according to claim 1 wherein the wireless communication system comprises a code division multiple access (CDMA) system.
8. A method according to claim 1 wherein the received signals being measured comprise a pilot signal.
9. A method according to claim 1 wherein the measuring comprises measuring at least one of a signal to interference ratio (SIR), a signal to noise ratio, and a signal strength of the received signals.
10. A method for operating a wireless transmit/receive unit (WTRU) in a wireless communication system comprising a plurality of cells, the WTRU comprising a switched beam antenna for generating antenna beams including a plurality of directional beams and an omni-directional beam, the method comprising:
using a selected antenna beam for exchanging data with one or more cells in an active set of cells;
receiving signals from cells in the active set of cells and from cells in a candidate set of cells using the selected antenna beam;
measuring the received signals from each cell for the selected antenna beam;
selecting a subset of cells from the candidate set of cells based on the measured signals associated therewith;
receiving signals from each cell in the active set of cells and from each cell in the subset of cells using the plurality of directional beams and the omni-directional beam, and receiving signals from the cells in the candidate set of cells but not in the subset of cells using at least the selected antenna beam;
measuring the received signals;
selecting the measured signal having the highest value from each cell in the active set of cells, from each cell in the subset of cells, and from the cells in the candidate set of cells but not in the subset of cells;
comparing the selected measured signals; and
sending a measurement report to the network when the selected measured signals for a cell in the candidate set of cells exceeds a reporting threshold criteria when compared to the selected measured signals for a cell in the active set of cells.
11. A method according to claim 10 wherein the reporting threshold criteria comprises at least one of a fixed number of measurements, and a fixed number of measurements for a given number of measurements.
12. A method according to claim 10 wherein the subset of cells from the candidate set of cells is based on comparing the measured signals associated therewith to a threshold.
13. A method according to claim 10 wherein the threshold is set by the network.
14. A method according to claim 10 wherein the threshold is based on exceeding measurements from the cells in the active set of cells by a predetermined amount.
15. A method according to claim 10 wherein the wireless communication system comprises a code division multiple access (COMA) system.
16. A method according to claim 10 wherein the received signals being measured comprise a pilot signal.
17. A method according to claim 10 wherein the measuring comprises measuring at least one of a signal to interference ratio (SIR), a signal to noise ratio, and a signal strength of the received signals.
18. A method for operating a wireless transmit/receive unit (WTRU) in a wireless communication system comprising a plurality of base stations, each base station belonging to a cell, the WTRU comprising a switched beam antenna for generating antenna beams including a plurality of directional beams and an omni-directional beam, the method comprising:
using a selected antenna beam for exchanging data with one or more cells in an active set of cells;
receiving signals from cells in the active set of cells and from cells in a candidate set of cells using the selected antenna beam;
measuring the received signals from each cell;
selecting a subset of cells from the candidate set of cells based on the measured signals associated therewith;
selecting a subset of antenna beams for each cell in the active set of cells and for each cell in the subset of cells in the candidate set of cells;
receiving signals from cells in the active set of cells and from the subset of cells in the candidate set of cells using the respective subset of antenna beams, and from cells in the candidate set of cells using at least the selected antenna beam;
measuring the received signals for each respective subset of antenna beams;
selecting the measured signal having the highest value from each cell in the active set of cells, from each cell in the subset of cells, and from the cells in the candidate set of cells but not in the subset of cells;
comparing the selected measured signals; and
sending a measurement report to the network when the selected measured signals for a cell in the candidate set of cells exceeds a reporting threshold criteria when compared to the selected measured signals for a cell in the active set of cells.
19. A method according to claim 18 wherein the reporting threshold criteria comprises at least one of a fixed threshold, or threshold based upon the measured signals, and a threshold based upon a plurality of parameters occurring during a predetermined time interval.
20. A method according to claim 18 wherein the subset of cells from the candidate set of cells is based on comparing the measured signals associated therewith to a threshold.
21. A method according to claim 18 wherein the threshold is set by the network.
22. A method according to claim 18 wherein the threshold is based on exceeding measurements from the cells in the active set of cells by a predetermined amount.
23. A method according to claim 18 wherein the respective subsets of antenna beams are different for each cell.
24. A method according to claim 18 wherein the respective subsets of antenna beams are the same for each cell.
25. A method according to claim 18 wherein the respective subsets of antenna beams are selected based upon location of the cells.
26. A method according to claim 18 wherein the respective subsets of antenna beams are selected based upon previous measurements.
27. A method according to claim 18 wherein the wireless communication system comprises a code division multiple access (CDMA) system.
28. A method according to claim 18 wherein the received signals being measured comprise a pilot signal.
29. A method according to claim 18 wherein the measuring comprises measuring at least one of a signal to interference ratio (SIR), a signal to noise ratio, and a signal strength of the received signals.
30. A wireless communication system comprising:
an active set of cells;
a candidate set of cells; and
a wireless transmit/receive unit (WTRU) comprising
a switched beam antenna for generating antenna beams including a plurality of directional beams and an omni-directional beam, a respective subset of antenna beams being selected for each cell in the active set of cells and for each cell in the candidate set of cells,
a transceiver connected to the switched beam antenna for receiving signals from cells in the active set of cells and from cells in the candidate set of cells using the respective subset of antenna beams,
a measuring unit connected to said transceiver for measuring the received signals from each cell for each respective subset of antenna beams,
a controller for selecting the measured signal having the highest value from each cell in the active set of cells and in the candidate set of cells, for comparing the selected measured signals, and for sending a measurement report to the network when the selected measured signals for a cell in the candidate set of cells exceeds a reporting threshold criteria when compared to the selected measured signals for a cell in the active set of cells.
31. A wireless communication system comprising:
an active set of cells;
a candidate set of cells; and
a wireless transmit/receive unit (WTRU) comprising
a switched beam antenna for generating antenna beams including a plurality of directional beams and an omni-directional beam, an antenna beam being selected for exchanging data with one or more cells in the active set of cells,
a transceiver connected to the switched beam antenna for receiving signals from cells in the active set of cells and from cells in the candidate set of cells using the selected antenna beam,
a measuring unit connected to said transceiver for measuring the received signals from each cell for the selected antenna beam, and
a controller for selecting a subset of cells from the candidate set of cells based on the measured signals associated therewith,
said transceiver also for receiving signals from each cell in the active set of cells and from each cell in the subset of cells using the plurality of directional beams and the omni-directional beam, and receiving signals from the cells in the candidate set of cells but not in the subset of cells using at least the selected antenna beam,
said measurement unit also for measuring the received signals,
said controller also for
selecting the measured signal having the highest value from each cell in the active set of cells, from each cell in the subset of cells, and from the cells in the candidate set of cells but not in the subset of cells,
comparing the selected measured signals, and
sending a measurement report to the network when the selected measured signals for a cell in the candidate set of cells exceeds a reporting threshold criteria when compared to the selected measured signals for a cell in the active set of cells.
32. A wireless communication system comprising:
an active set of cells;
a candidate set of cells; and
a wireless transmit/receive unit (WTRU) comprising
a switched beam antenna for generating antenna beams including a plurality of directional beams and an omni-directional beam, an antenna beam being selected for exchanging data with one ore more cells in the active set of cells,
a transceiver connected to the switched beam antenna for receiving signals from cells in the active set of cells and from cells in a candidate set of cells using the selected antenna beam,
a measuring unit connected to said transceiver for measuring the received signals from each cell for the selected antenna beam, and
a controller for selecting a subset of cells from the candidate set of cells based on the measured signals associated therewith, and for selecting a respective subset of antenna beams for each cell in the active set of cells and for each cell in the subset of cells in the candidate set of cells,
said transceiver also for receiving signals from cells in the active set of cells and from the subset of cells in the candidate set of cells using the respective subset of antenna beams, and from cells in the candidate set of cells but not in the subset using at least the selected antenna beam,
said measurement unit also for measuring the received signals from each cell for each respective subset of antenna beams,
said controller also for
selecting the measured signal having the highest value from each cell in the active set of cells, from each cell in the subset of cells, and from the cells in the candidate set of cells but not in the subset of cells,
comparing the selected measured signals, and
sending a measurement report to the network when the selected measured signals for a cell in the candidate set of cells exceeds a reporting threshold criteria when compared to the selected measured signals for a cell in the active set of cells.