Broadband wireless systems need to achieve high spectrum efficiency as well as high power efficiency of HPA (High Power Amplifier). When HPA is used with low output back-off (OBO), increased ACLP (Adjacent Channel Leakage Power) results in significant ACI (Adjacent Channel Interference) especially in TDD (Time Division Duplexing) wireless systems due to a near-far problem. In order to solve this ACLP problem of HPA at a mobile terminal, this paper proposes a novel HPA linearization system using amplitude reference pilot signal which is used to measure input-output characteristics of HPA of a mobile terminal at a base station. It describes design and performance of amplitude reference pilot signal and shows ACLP improvement to confirm the feasibility of the proposed HPA linearization system.