A fast automatic gain control scheme for initial cell search in 3GPP LTE TDD system

In this paper, we propose a fast automatic gain control (AGC) scheme for initial cell search in long term evolution (LTE) time division duplex (TDD) system. Since the received signal has a large signal power difference between uplink and downlink in TDD systems, conventional AGC scheme leads to increased AGC gain variation and the received signal will be attenuated. In order to overcome this problem, we propose a modified AGC scheme based on the average amplitude ratio calculation which can not only effectively increase convergence speed of the AGC gain but also maintain the stability of AGC operation. Also, it is important for AGC to converge efficiently for the accurate radio frame timing detection during the subsequent initial cell search procedure. Therefore, we also consider the proposed AGC scheme in combination with primary synchronization signal (PSS) detection interface. By using extensive computer simulation in the presence of frequency offset and various channel environments, we show that the proposed method can obtain a good behavior in terms of convergence speed and PSS detection performance in LTE TDD system and verify that it is attractive and suitable for implementation with stable operation.