Radio link handover in a cellular communication system
View Patent ↗A base station ( 109 ) of a cellular communication system ( 100 ) comprises an RNC interface ( 301 ) which receives a radio link handover initiation message for a radio link from a radio network controller ( 113 ). A switch delay processor ( 309 ) determines a handover switch delay and a characteristics processor ( 311 ) sets a characteristic of a radio link handover acknowledge message in response to the handover switch delay. A message generator ( 313 ) generates a radio link handover acknowledge message and transmits this to the radio network controller ( 113 ). The radio network controller ( 113 ) comprises an RNC handover controller ( 125 ) which determines a radio link handover switch time in response to the characteristic. A better timing of the radio link handover may be achieved. The invention may e.g. be applicable to an HSDPA (High Speed Downlink Packet Access) service of a UMTS (Universal Mobile Telecommunication System) cellular communication system and may reduce the amount of data discarded from buffers during an HSDPA handover.
1. A base station supporting a radio link handover in a cellular communication system, the base station comprising:
means for receiving a radio link handover initiation message from a network element for a radio link supporting a communication between the base station and a user equipment;
determining means for determining a handover switch delay;
setting means for setting a characteristic of a radio link handover acknowledge message in response to the handover switch delay; and
means for transmitting the radio link handover acknowledge message to the network element;
wherein the determining means are arranged to determine the handover switch delay in response to a data discard measure of a previous radio link handover for the base station.
2. The base station claimed in claim 1 wherein the setting means are arranged to set a transmission time for the radio link handover acknowledge message in response to the handover switch delay.
3. The base station claimed in claim 1 wherein the setting means are arranged to delay transmission of the radio link handover acknowledge message until a buffer level of a buffer for the communication is below a threshold.
4. The base station claimed in claim 1 wherein the setting means are arranged to include an indication of the handover switch delay in the radio link handover acknowledge message.
5. The base station claimed in claim 1 wherein the setting means are arranged to determine a minimum preferred handover activation time in response to the handover switch delay and to include an indication of the minimum preferred handover activation time in the radio link handover acknowledge message.
6. The base station claimed in claim 5 wherein the minimum preferred handover activation time indicates a frame number.
7. The base station claimed in claim 1 wherein the determining means are arranged to determine the handover switch delay in response to a data buffer characteristic for the communication.
8. The base station claimed in claim 1 wherein the radio link is a Universal Mobile Telecommunication System Terrestrial Radio Access Network radio link, the radio link handover initiation message is an Nobe B Application Part (NBAP) Radio Link Reconfiguration Prepare message, and the radio link handover acknowledge message is an NBAP Radio Link Reconfiguration Ready message.
9. A method for supporting a radio link handover in a cellular communication system, the method comprising:
receiving a radio link handover initiation message from a network element for a radio link supporting a communication between a base station and a user equipment;
determining a handover switch delay;
setting a characteristic of a radio link handover acknowledge message in response to the handover switch delay; and
transmitting the radio link handover acknowledge message to the network element;
wherein determining comprises determining the handover switch delay in response to a data discard measure of a previous radio link handover for the base station.