Abstract: Apparatus and methods are provided to calibrate a closed-loop envelop tracking system for a power amplifier of a wireless transmitter using standardized modulation signals. In one novel aspect, a closed-loop adaptive method is used to track changes in PA nonlinearity due to environmental or circuitry changes during operating condition using standardized modulation signals. In one embodiment, the PA supply voltage compensation lookup table (LUT) and/or the phase compensation LUT is updated during normal operation to sustain good linearity and efficiency performance. In another novel aspect, the PA target response is adjusted in response to changes in PA-related system configuration, such as changes in PA bias settings, and/or indicators measured from the transmitter such as changes in impedance or temperature changes for the RF module or the PA module. The PA supply voltage compensation LUT and/or the phase LUT is updated accordingly upon adjustment of the PA target response.

Abstract: A method of obtaining system frame number for handover is provided. A UE receives a handover command from a serving base station in a serving cell. The UE performs downlink synchronization with a target base station. Upon synchronization, the UE determines a radio frame boundary of a target cell. The UE then obtains a system frame number of the target cell based on the radio frame boundary. The UE performs a handover procedure with the target cell by transmitting a RACH preamble to the target base station. The RACH preamble is transmitted over a PRACH resource determined from the system frame number without reading SFN information from a PBCH/BCH broadcasted from the target base station. Finally, the UE establishes data connection with the target base station. Handover interruption time is reduced by obtaining SFN before PBCH reading and decoding.

Abstract: A method of obtaining system frame number for handover is provided. A UE receives a handover command from a serving base station in a serving cell. The UE performs downlink synchronization with a target base station. Upon synchronization, the UE determines a radio frame boundary of a target cell. The UE then obtains a system frame number of the target cell based on the radio frame boundary. The UE performs a handover procedure with the target cell by transmitting a RACH preamble to the target base station. The RACH preamble is transmitted over a PRACH resource determined from the system frame number without reading SFN information from a PBCH/BCH broadcasted from the target base station. Finally, the UE establishes data connection with the target base station. Handover interruption time is reduced by obtaining SFN before PBCH reading and decoding.