A method, comprising: transmitting uplink data from a user device (102, 103, 104, 105; 301), UE, to a network device (101; 302) over a wireless uplink channel; measuring transmission power of the uplink channel and thereby generating transmission power information; obtaining transmission Quality of Service, QoS information of the uplink channel; and correlating the transmission power information with the transmission QoS information and thereby determining uplink performance of the UE (102, 103, 104, 105; 301); characterized in that the UE (102, 103, 104, 105; 301) archives a correlation result of the transmission power information and the transmission QoS information in a UE metrics log and the archiving into the log is conditional based on a condition corresponding to a network performance problem; wherein the condition is fulfilled when a data rate is smaller than a minimum data rate and the UE (102, 103, 104, 105; 301) is power limited and wherein the data rate is comprised by the transmission QoS information and an indicator, which indicates that the UE (102, 103, 104, 105; 301) is power limited, is comprised by the transmission power information; or wherein the condition is fulfilled when a transport block size is smaller than a minimum transport block size and the UE (102, 103, 104, 105; 301) is power limited and wherein the transport block size is comprised by the transmission QoS information and an indicator, which indicates that the UE (102, 103, 104, 105; 301) is power limited, is comprised by the transmission power information; or wherein the condition is fulfilled when a modulation and coding scheme is smaller than a minimum modulation and coding scheme threshold and the UE (102, 103, 104, 105; 301) is power limited and wherein the modulation and coding scheme is comprised by the transmission QoS information and an indicator, which indicates that the UE (102, 103, 104, 105; 301) is power limited, is comprised by the transmission power information. transmitting uplink data from a user device (102, 103, 104, 105; 301), UE, to a network device (101; 302) over a wireless uplink channel; measuring transmission power of the uplink channel and thereby generating transmission power information; obtaining transmission Quality of Service, QoS information of the uplink channel; and correlating the transmission power information with the transmission QoS information and thereby determining uplink performance of the UE (102, 103, 104, 105; 301); characterized in that the UE (102, 103, 104, 105; 301) archives a correlation result of the transmission power information and the transmission QoS information in a UE metrics log and the archiving into the log is conditional based on a condition corresponding to a network performance problem; wherein the condition is fulfilled when a data rate is smaller than a minimum data rate and the UE (102, 103, 104, 105; 301) is power limited and wherein the data rate is comprised by the transmission QoS information and an indicator, which indicates that the UE (102, 103, 104, 105; 301) is power limited, is comprised by the transmission power information; or wherein the condition is fulfilled when a transport block size is smaller than a minimum transport block size and the UE (102, 103, 104, 105; 301) is power limited and wherein the transport block size is comprised by the transmission QoS information and an indicator, which indicates that the UE (102, 103, 104, 105; 301) is power limited, is comprised by the transmission power information; or wherein the condition is fulfilled when a modulation and coding scheme is smaller than a minimum modulation and coding scheme threshold and the UE (102, 103, 104, 105; 301) is power limited and wherein the modulation and coding scheme is comprised by the transmission QoS information and an indicator, which indicates that the UE (102, 103, 104, 105; 301) is power limited, is comprised by the transmission power information.