Handover robustness in cellular radio communications

Abstract

An indication of the speed of movement of a UE in a radio communications system is received at a network node of the radio communications system. The parameters of the radio communications system are then analyzed using the speed of movement indication. The system parameters are then adjusted using the analysis.

What is claimed is: 
     
         1 . A method implemented in a network node of a cellular radio communications system to improve system functionality using speed information regarding a user equipment (UE), the method comprising:
 receiving an indication of a speed of movement of the UE;   analyzing system parameters using the speed of movement indication; and   adjusting the system parameters using the analysis.   
     
     
         2 . The method of  claim 1 :
 wherein receiving an indication comprises receiving a report, for example an HO Report or an RLF INDICATION message, from another network node indicating a signal strength measured by the UE during an attempted handover from the network node to the other cell, and a time elapsed between a connection request by the UE and a failure of the connection together with the indication of a speed of movement of the UE;   wherein the system parameters comprise mobility thresholds for the UE;   wherein analyzing comprises analyzing the handover report to determine whether the handover failure is due to UE speed of movement; and   wherein adjusting comprises adjusting mobility thresholds for the UE with respect to neighbor cells.   
     
     
         3 . The method of  claim 2 , wherein receiving a report comprises receiving a handover failure report, for example an HO Report including a UE RLF Report Container IE, the report including an indication of the size of the other cell, and wherein analyzing includes analyzing using the size of the other cell. 
     
     
         4 . The method of  claim 2 , further comprising sending a mapping table to the UE indicating priorities for cells of the cellular radio communications system, the mapping table optionally including scaling factors for analyzing received signal strength for handover to each network node of the mapping table or times to trigger for determining when to request handover to each network node of the mapping table. 
     
     
         5 . The method of  claim 1 , further comprising prioritizing target cells for the UE depending on the indication of the speed of movement of the UE for example by sending a per UE per target CIO to fast moving UEs. 
     
     
         6 . The method of  claim 1 , wherein the system parameters include a list of candidate UEs to move from the network node to another network node as a load balancing move and wherein receiving an indication of speed comprises receiving speed information regarding speed of movement of a move candidate EU, for example in UE history information or an RLF Report from another node, the method further comprising:
 selecting move candidate UEs;   determining whether a selected move candidate UE is a high mobility UE using the received speed information; and   excluding the selected move candidate UE from a load balancing move if the selected move candidate UE is determined to be a high mobility UE.   
     
     
         7 . The method of  claim 6 , wherein determining whether the selected move candidate EU is a high mobility EU comprises comparing the received speed information to a threshold speed. 
     
     
         8 . The method of  claim 6 , wherein receiving speed information comprises receiving speed information as an information element of location information regarding the selected move candidate or as an information element of a failed handover report, for example a UE RLF Report Container IE in an HO Report, and wherein receiving speed information optionally comprises receiving speed information from the move candidate UE. 
     
     
         9 . The method of  claim 1 , wherein the system parameters comprise a list of UEs that have been commanded to operate in an idle mode, the method comprising:
 determining that a UE has a high speed of movement and a low traffic data rate;   commanding the UE to move to an idle mode after a UE data transmission; and   receiving a connection request from the UE when the UE has additional data to transmit, the UE moving from the idle mode to send the connection request; and   sending information to another network node of the radio communications system that the UE has been commanded to move to an idle mode upon determining that the UE has moved near the other cell.   
     
     
         10 . The method of  claim 8 , wherein the UE returns to the idle mode after transmitting the additional data. 
     
     
         11 . The method of  claim 9 , further comprising waking the UE from the idle mode to receive transmitted data. 
     
     
         12 . The method of  claim 9 , wherein the connection request is a request to connect to another cell and the connection request, for example an RRC Connection Setup Request or RRC Connection Setup Complete message, and wherein the request includes sending the information within the request as an indication that the UE has been commanded to move to an idle mode by the first cell. 
     
     
         13 . The method of  claim 9 , wherein sending information comprises the UE sending information to the other network node as part of the connection request. 
     
     
         14 . The method of  claim 9 , wherein sending information comprises sending information as an information element of UE history information. 
     
     
         15 . A network node of a cellular radio communications system configured to improve system functionality using speed information regarding a user equipment (UE), the network node comprising:
 a receiver configured to receive an indication of a speed of movement of the UE;   a controller configured to analyze system parameters using the speed of movement indication and to adjust system parameters; and   a transmitter configured to transmit system parameter adjustments to other nodes.   
     
     
         16 . The network node of  claim 15 , wherein:
 receiving an indication further comprises receiving a handover report from another network node indicating a signal strength measured by the UE during an attempted handover and a time elapsed between a connection request by the UE and a failure of the connection;   analyzing system parameters further comprises analyzing the handover report to determine whether the handover failure is due to UE speed of movement; and   adjusting system parameters further comprises adjusting mobility thresholds for the UE with respect to neighbor network nodes.   
     
     
         17 . The network node of  claim 15 , wherein:
 the controller is further configured to determine that a UE has a high speed of movement and a low traffic data rate;   the transmitter is further configured to transmit system parameter adjustments by commanding the UE to move to an idle mode after a UE data transmission;   the receiver is further configured to receive a connection request from the UE when the UE has additional data to transmit; and   the network node further comprising a system interface configured to send information to another cell of the radio communications system that the UE has been commanded to move to an idle mode upon the controller determining that the UE has moved near the other cell.   
     
     
         18 . The network node of  claim 15 , wherein:
 the controller is further configured to determine that a UE has a high speed of movement and a low traffic data rate;   the transmitter is further configured to transmit system parameter adjustments by commanding the UE to move to an idle mode after a UE data transmission;   the receiver is further configured to receive a connection request from the UE when the UE has additional data to transmit; and   the network node further comprising a system interface configured to send information to another cell of the radio communications system that the UE has been commanded to move to an idle mode upon the controller determining that the UE has moved near the other cell.   
     
     
         19 . The network node of  claim 15 , wherein the transmitter transmits system parameter adjustment as in information element of UE history information. 
     
     
         20 . A network node of a cellular radio communications system configured to improve system functionality using speed information regarding a user equipment (UE), the network node comprising:
 means for receiving an indication of a speed of movement of the UE;   means for analyzing system parameters using the speed of movement indication and to adjust system parameters; and   means for transmitting system parameter adjustments to other nodes.