Intra-frequency load balancing method and apparatus thereof

Patent metadata

Field	Value
Publication number	US-9432880-B2
Application number	US-201214111791-A
Country	US
Kind code	B2
Filing date	Feb 29, 2012
Priority date	Apr 22, 2011
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

The present disclosure provides an uplink intra-frequency load balancing method. The uplink intra-frequency load balancing can be performed by adjusting a beam direction of a User Equipment UE. For each of UEs, the method comprises steps of: determining a cell load level of each cell based on an uplink load measurement received from base stations of a plurality of cells; determining a beam-forming capability of the UE based on a beam-forming gain of the UE; and calculating a cell balancing parameter for each of the plurality of cells, according to a common pilot channel CPICH quality report measured by the UE, the cell load levels of the plurality of cells and the beam-forming capability of the UE, so as to determine a beam-forming control cell towards which the beam direction of the UE is directed, the beam-forming control cell being a cell which has an optimal cell balancing parameter among the plurality of cells. The present disclosure further provides, for a UE which supports a CLBF mode but is not in the CLBF mode, a method for selectively activating the CLBF mode so as to enhance the effect of load balancing. The present further provides an uplink intra-frequency load balancing apparatus.

First claim

What is claimed is:

1. A method of uplink intra-frequency load balancing, wherein the uplink intra-frequency load balancing can be performed by adjusting a beam direction of a User Equipment (UE), the method comprising:
determining a cell load level of each of a plurality of cells based on an uplink load measurement received from a base station of a corresponding one of the plurality of cells;
determining a beam-forming capability of the UE based on a beam-forming gain of the UE;
calculating a cell balancing parameter for each of the plurality of cells according to a common pilot channel (CPICH) quality report measured by the UE, the cell load levels of the plurality of cells, and the beam-forming capability of the UE, so as to determine a beam-forming control cell, wherein the beam direction of the UE is directed towards a base station antenna of the beam-forming control cell, the beam-forming control cell being a cell which has an optimal cell balancing parameter among the plurality of cells, wherein for two of the plurality of cells referred to as Cell a and Cell b, the calculating step calculates a relative cell balancing parameter of the Cell a with respect to the Cell b as follows:
( Q a −Qb )+sign(CSO a −CSO b ) X min(abs(CSO a −CSO b ), USO ),

wherein CSO is a cell specific offset, wherein USO is an absolute EU specific offset, wherein Q a represents the CPICH quality of the Cell a, Q b represents the CPICH quality of the Cell b, CSO a represents the CSO of the Cell a, and CSO b represents the CSO of the Cell b, sign represents “+/−”, min represents that a minimum value is taken, X represents a multiplication operator, and abs represents that an absolute value is taken.

2. The method of claim 1 , wherein the uplink load measurement comprises a Received Total Wide Band Power (RTWP), a Rise over Thermal (RoT), or a load factor.

3. The method of claim 1 , wherein determining the cell load level comprises estimating the cell load level of each of the plurality of cells based on a target load and the uplink load measurement received from the base station of the corresponding one of the plurality of cells.

4. The method of claim 3 , wherein estimating the cell load level comprises estimating the cell load level of each of the plurality of cells based on a difference between the target load and the uplink load measurement received from the base stations of the corresponding one of the plurality of cells.

5. The method of claim 1 , wherein calculating the cell balancing parameter for each of the plurality of cells comprises, for each of the plurality of cells:
multiplying a cell specific offset (CSO) representing the cell load level of the cell with a relative UE specific offset (USO) representing the beam-forming capability of the UE to obtain a product for the cell; and
summing the CPICH quality report (Q CPICH ) of the cell measured by the UE and the obtained product to calculate the cell balancing parameter;
wherein the beam-forming control cell comprises a cell having a largest cell balancing parameter among the plurality of cells.

6. The method of claim 5 , further comprising calculating the relative USO according to the beam-forming capability of the UE and a determination of whether the UE is in a closed-loop beam-forming (CLBF) mode.

7. The method of claim 6 , wherein calculating the relative USO comprises calculating the relative USO in real-time.

8. The method of claim 6 :
wherein calculating the relative USO comprises calculating the relative USO as k(flag BCLBF , Gain BF ), where Gain BF represents the beam-forming gain and k(*,GainBF) represents a monotone non-decreasing function of Gain BF whose range domain comprises [0, 1]; and
wherein when the UE is in the CLBF mode, flag BCLBF =1, and otherwise flag BCLBF =0.

9. The method of claim 6 :
wherein calculating the relative USO comprises calculating the relative USO as flag BCLBF X(1−1/M ant ) n , where M ant represents a number of transmitting antennas of the UE and n represents a system configurable integer greater or equal to one; and
wherein when the UE is in the CLBF mode, flag BCLBF =1, and otherwise flag BCLBF =0.

10. The method of claim 1 , further comprising:
if the relative cell balancing parameter of the Cell a with respect to the Cell b is positive, indicating that the cell balancing parameter of the Cell a is more optimal than that of the Cell b, continuing to calculate a relative cell balancing parameter of the Cell a relative to another cell; and
if the relative cell balancing parameter of the Cell a with respect to the Cell b is negative, indicating that the cell balancing parameter of the Cell b is more optimal than that of the Cell a, continuing to calculate a relative cell balancing parameter of the Cell b relative to another cell until the cell which has the optimal cell balancing parameter is selected.

11. The method of claim 1 , further comprising calculating the USO according to the beam-forming capability of the UE and a determination of whether the UE is in a closed-loop beam-forming (CLBF) mode.

12. The method of claim 11 , wherein calculating the USO comprises calculating the USO in real-time.

13. The method of claim 11 ;
wherein calculating the USO comprises calculating the USO as f(flag BCLBF ,Gain BF ), where Gain BF represents the beam-forming gain and f(*,Gain BF ) represents a monotone non-decreasing function of Gain BF ;
wherein when the UE is in the CLBF mode, flag BCLBF =1, and otherwise flag BCLBF =0.

14. The method of claim 11 :
wherein calculating the USO comprises calculating the USO as
flag BCLBF Xmin (CSO max , −10 lg M ant ), where min represents that a minimum value is taken, M ant represents a number of transmitting antennas of the UE, lg represents a logarithm operator, and CSO max represents a maximum CSO, which comprises a system configurable parameter; and
wherein when the UE is in the CLBF mode, flag BCLBF =1, and otherwise flag BCLBF =0.

15. The method of claim 1 , wherein the beam-forming capability of the UE depends on the beam-forming gain estimated based on at least one of a number of transmitting antennas of the UE and a pre-coding scheme.

16. The method of claim 1 , wherein a larger beam-forming gain is indicative of a stronger beam-forming capability of the UE.

17. The method of claim 1 , further comprising:
activating a closed-loop beam-forming (CLBF) mode according to at least one of:
activating a UE with a higher beam-forming gain; and
activating the CLBF mode for at most m UEs in every n seconds, wherein m and n comprise configurable parameters, for a UE which supports the CLBF mode but is not in the CLBF mode; and

if the CLBF mode is activated, the UE supporting the CLBF mode re-determines the beam-forming control cell.

18. The method of claim 1 , wherein the method is performed at a radio network controller (RNC), and wherein the UE notifies the RNC of the measured CPICH quality report and the determined beam-forming capability of the UE.

19. The method of claim 1 , wherein the method is performed at the UE, and wherein a radio network controller (RNC) notifies the UE of the cell load levels of the plurality of cells.

20. An uplink intra-frequency load balancing apparatus, wherein the uplink intra-frequency load balancing can be performed by adjusting a beam direction of a User Equipment (UE), the apparatus comprising:
a first determination circuit configured to determine a cell load level of each of a plurality of cells based on an uplink

Assignees

• Zhang Zhang
• Liu Jinhua
• Ericsson Telefon Ab L M

Inventors

• Zhang Zhang
• Liu Jinhua

Classifications

• H04B7/0404 Primary

  the mobile station comprising multiple antennas, e.g. to provide uplink diversity · CPC title

• H04B7/0617

  for beam forming · CPC title

• H04W16/28

  using beam steering · CPC title

• H04B7/0634

  Antenna weights or vector/matrix coefficients · CPC title

• H04W28/085 Primary

  Electricity · mapped topic