Method of reporting link failure

Abstract

If a new link is established between a user equipment and a serving base station after a previous link failure, the user equipment is configured to report information associated with the previous link failure, including UE mobility information during the previous link, information related to transmitting/receiving the RRC connection reconfiguration, or information related to radio link failure. The serving base station is configured to perform mobility optimization in the minimization of drive test accordingly for improving handover success rate and overall network efficiency.

What is claimed is: 
     
       1. A method of reporting link failure, comprising:
 measuring mobility information during a first link between a user equipment (UE) and a serving base station, wherein the mobility information includes one of a user equipment mobility state, a change in the user equipment mobility state, and a user equipment mobility speed when the user equipment mobility state changes; 
 wherein the user equipment mobility state indicates a high-mobility state, a medium-mobility state or a low-mobility state according to how many times a cell re-selection occurs during a predetermined period; 
 wherein the change in the user equipment mobility state is provided by one of (a) measuring a location change of the user equipment during the first link using a global positioning system (GPS), and (b) based on a timing change of the user equipment which is acquired by measuring transmission times of a single-frequency network (SFN) or an orthogonal frequency-division multiplexing (OFDM) during the first link; 
 retaining the mobility information measured during the first link regardless of whether the user equipment has encountered a coverage problem for a predetermined period of time during the first link; 
 establishing a second link between the user equipment and a target base station after a first link between the user equipment and the serving base station fails, wherein the target base station and the serving base station is a same base station; 
 the user equipment reporting the mobility information of the user equipment to the target base station after establishing the second link; 
 when determining that a radio resource control (RRC) connection reconfiguration is received from the serving base station during the first link, the user equipment reporting first information associated with a condition in which the RRC connection reconfiguration is transmitted or received during the first link; and 
 the target base station performing a minimization of drive test (MDT) mobility optimization according to the mobility information and the first information. 
 
     
     
       2. The method of  claim 1 , further comprising:
 measuring a reference signal received power (RSRP) or a reference signal received quality (RSRQ) of the serving base station and the target base station during the first link; and 
 determining that the mobility information indicates a high-mobility state, a medium-mobility state or a low-mobility state according to how many times a cell re-selection occurs during a predetermined period. 
 
     
     
       3. The method of  claim 1 , further comprising:
 providing the change in the user equipment mobility state by measuring a location change of the user equipment during the first link using a standalone global positioning system (GPS), a standalone global navigation satellite system (GNSS), an assisted GPS, an assisted GNSS, a location services (LCS) orientation, or a secure user plane location (SUPL) orientation. 
 
     
     
       4. The method of  claim 1 , further comprising:
 acquiring the user equipment mobility speed using a standalone global positioning system (GPS), a standalone global navigation satellite system (GNSS), an assisted GPS, an assisted GNSS, a location services (LCS) orientation, or a secure user plane location (SUPL) orientation. 
 
     
     
       5. The method of  claim 1 , wherein the condition in which the RRC connection reconfiguration is transmitted or received during the first link includes:
 a start time of a timer defined in a corresponding 3rd Generation Partnership Project (3GPP) specification; 
 an expire time of the timer; 
 a location or a speed of the user equipment when the timer starts; 
 a location or a speed of the user equipment when the timer expires; or 
 a maximum random access channel (RACH) power used to transmit the RRC connection reconfiguration. 
 
     
     
       6. The method of  claim 1 , further comprising:
 when determining that a radio resource control connection reconfiguration is not received during the first link, the user equipment reporting second information associated with a radio link failure (RLF) during the first link, wherein the target base station is configured to perform the MDT mobility optimization further according to the second information. 
 
     
     
       7. The method of  claim 6 , wherein the second information includes a start time of a timer defined in a corresponding 3rd Generation Partnership Project specification, an expire time of the timer, a media access control (MAC) problem, or a radio link control (RLC) problem. 
     
     
       8. A method of reporting link failure, comprising:
 measuring mobility information during a first link between a user equipment and a serving base station, wherein the mobility information includes one of a user equipment mobility state, a change in the user equipment mobility state, and a user equipment mobility speed when the user equipment mobility state changes; 
 wherein the user equipment mobility state indicates a high-mobility state, a medium-mobility state or a low-mobility state according to how many times a cell re-selection occurs during a predetermined period; 
 wherein the change in the user equipment mobility state is provided by one of (a) measuring a location change of the user equipment during the first link using a global positioning system (GPS), and (b) based on a timing change of the user equipment which is acquired by measuring transmission times of a single-frequency network (SFN) or an orthogonal frequency-division multiplexing (OFDM) during the first link; 
 retaining the mobility information measured during the first link regardless of whether the user equipment has encountered a coverage problem for a predetermined period of time during the first link; 
 establishing a second link between the user equipment and a target base station after a first link between the user equipment and the serving base station fails, wherein the target base station and the serving base station is a same base station; 
 the user equipment reporting the mobility information of the user equipment to the target base station after establishing the second link; 
 when determining that a radio resource control connection (RRC) reconfiguration is not received from the serving base station during the first link, the user equipment reporting first information associated with a condition in which a radio link failure (RLF) occurs during the first link or associated with a cause of the radio link failure; and 
 the target base station performing a minimization of drive test (MDT) mobility optimization according to the mobility information and the first information. 
 
     
     
       9. The method of  claim 8 , wherein the condition in which the radio link failure occurs during the first link or the cause of the radio link failure, the first information includes a start time of a timer defined in a corresponding 3rd Generation Partnership Project specification, an expire time of the timer, a media access control (MAC) problem, or a radio link control (RLC) problem.