Method and apparatus for cell handoff

Abstract

A method for handoff between cells in a communication system includes the network sends a cell individual offset preset for a cell in the active set relative to each of its neighboring cells respectively to a terminal; after measuring the cell in the active set and its neighboring cells, the terminal evaluates the measurement in accordance with the measurement result and the cell individual offset for the cell in the active set relative to its each neighboring cell; the terminal then submits a measurement report to the network in accordance with the measurement evaluation result; the network instructs the terminal to perform a handoff between cells in accordance with the measurement report. The invention also discloses a network controller and a terminal corresponding to the method. With the invention, the cell individual offset for a cell is set relative to its each neighboring cell so that the handoff between cells can be more accurate. As a result, user of the terminal can obtain better experience.

1 . A method for handoff between cells, comprising:
 obtaining from a network a cell individual offset for an adjacent cell of an active set cell configured by the network, wherein each adjacent has such an cell individual offset relative to the cell;   measuring the active set cell and the adjacent cell;   evaluating the cell measurement according to a result of the cell measurement and the cell individual offset;   submitting a measurement report to the network according to a result of the measurement evaluation; and   receiving an instruction to perform handoff from the network, wherein the instruction is made by the network according to the measurement report.   
   
   
       2 . The method of  claim 1 , wherein evaluating of the measurement according to the measurement result and the cell individual offset comprises:
 if, during a time period ΔT of measurement report triggering, the pilot signal quality of a target cell in a monitored set meets a condition for adding a cell and the active set is not full, adding the target cell to a cell list of the active set of the terminal and marking the target cell as a cell to be added to the active set; or   if, during a time period ΔT of measurement report triggering, the pilot signal quality of a target cell in the active set fulfills a condition for removing a cell, removing the target cell from the active set of the terminal; or   if, during a time period ΔT of measurement report triggering, the pilot signal quality of a target cell in a monitored set fulfills a condition for replacing a cell and the active set is full, replacing the worst cell in the cell list of the active set of the terminal with the target cell in the monitored set.   
   
   
       3 . The method of  claim 1 , further comprising:
 receiving an adjusted cell individual offset from the network, wherein the adjusted cell individual offset is adjusted by the network according to a change about the active set.   
   
   
       4 . The method of  claim 3 , further comprising:
 measuring cell signal quality of the active set in response to the change about the active set; and   sending the measured cell signal quality to the network for adjusting the cell individual offset.   
   
   
       5 . A method used for handoff between cells, comprising:
 sending to a terminal, a cell individual offset for an adjacent cell of a cell in an active set relative to the active set cell, wherein each adjacent cell has such an cell individual offset independently relative to the active set cell;   receiving a cell measurement report from the terminal device; and   instructing the terminal device to perform a handoff between cells according to the received cell measurement report.   
   
   
       6 . The method of  claim 5 , wherein instructing the terminal to perform a handoff between cells comprises:
 performing a handoff evaluation based on the received measurement report; and   sending a handoff instruction message to the terminal to perform the handoff if a handoff condition is fulfilled according to the handoff evaluation.   
   
   
       7 . The method of  claim 5 , further comprising:
 in responsive to acquiring a change about the active set,   adjusting the cell individual offset for the adjacent cell of corresponding active set cell according to the change about the active set; and   sending the adjusted cell individual offset to the terminal.   
   
   
       8 . The method of  claim 7 , wherein the change about the active set includes a removal of a cell from the active set or a change of strength of cell signal in the active set. 
   
   
       9 . The method of  claim 8 , wherein if a cell in a monitored set is an adjacent cell of plural cells in the active set, in response to the change about the active set cell,
 obtaining, by the network, cell signal quality of the active set from and measured by the terminal;   selecting a cell in the active set with the best signal quality among those adjacent cells of the monitored set cell; and   taking, by the network, the cell individual offset of the selected active set cell relative to the monitored set cell as a new cell individual offset for the monitored set cell, and sending the new cell individual offset for the monitored set cell to the terminal.   
   
   
       10 . The method of  claim 8 , wherein if a cell in a monitored set is the adjacent cell of only one cell in the active set,
 in response to the change of the cell signal strength in the active set, keeping currently configured cell individual offset for the monitored set cell unchanged; or,   in response to the removal of a cell from the active set,
 the network does not set the cell individual offset for the monitored set cell if the removed active set cell is the only one adjacent cell of the monitored set cell, or, 
 if the removed cell is any other cell in the active set, keeping currently configured cell individual offset for the monitored set cell unchanged. 
   
   
   
       11 . A network controller in a network, comprising:
 a configuration module, adapted to configure a cell individual offset for an adjacent cell of a cell, wherein each adjacent cell has such an independent cell individual offset relative to the cell;   a sending module, adapted to send the cell individual offset for an adjacent cell of an active set cell configured by the configuration module to a terminal, whereby the terminal evaluates a cell measurement according to the cell individual offset and submits a measurement report to the network controller;   an instruction module, adapted to instruct the terminal to perform a cell handoff in accordance with the measurement report from the terminal.   
   
   
       12 . The network controller of  claim 11 , further comprising:
 an acquiring module, configured to acquire a change about the active set;   an adjustment module, adapted to adjust the cell individual offset for an adjacent cell of the active set cell relative to the corresponding active set cell according to the change about the active set and send the adjusted cell individual offset to the sending module,   the sending module is adapted to send the adjusted cell individual offset to the terminal.   
   
   
       13 . The network controller of  claim 12 , wherein the adjustment module comprises:
 a cell determination sub-module, adapted to determine, in response to the change about the active set, a cell in the active set with the best signal quality from those adjacent cells of a cell in the monitored set, in accordance with the signal quality reported by the terminal; and   an adjustment sub-module, adapted to take the cell individual offset of the determined cell with the best signal quality relative to the monitored set cell as a new cell individual offset for the monitored set cell and send the new cell individual offset to the individual offset sending module.   
   
   
       14 . The network controller of  claim 12 , wherein the change about the active set cell include a removal of a cell from the active or a change of cell signal quality in the active set. 
   
   
       15 . The network controller of  claim 13 , wherein the change about the active set cell include a removal of a cell from the active or a change of cell signal quality in the active set. 
   
   
       16 . A terminal device comprising:
 an obtaining module, adapted to obtain from a network a cell individual offset for an adjacent cell of a cell in an active set preconfigured by the network, wherein each adjacent cell of the active set cell has such an independent cell individual offset relative to the active cell configured by the network;   a measurement module, adapted to measure the active set cell and the adjacent cell;   a measurement evaluation module, adapted to evaluate the cell measurement according to the result of the cell measurement and the cell individual offset;   a measurement report module, adapted to send a measurement report to the network according to the result of the measurement evaluation; and   a handoff execution module, adapted to perform a handoff between cells according a handoff instruction sent by the network.   
   
   
       17 . The terminal device of  claim 16 , further comprising:
 means for, in response to a change about the active set, measuring signal quality of the cell in the active set and sending the measured signal quality to the network.   
   
   
       18 . The terminal device of  claim 16 , wherein the change about the active set includes a removal of a cell from the active set or a change of signal quality of a cell in the active set.