Efficient implementation of hybrid automatic gain control algorithm for chirp spread spectrum

Abstract

In this paper, we propose a novel hybrid automatic gain control (AGC) algorithm as a solution to improve the signal reception performance based on the IEEE 802.15.4a chirp spread spectrum (CSS). The CSS signals are composed of a number of full-chirps, which are separated by long guard time. A full-chirp is composed of two low-band sub-chirps and two high-band sub-chirps whose frequency characteristics are different because of multipath fading in indoor environment. Due to long guard time and wideband properties of the CSS, it is not appropriate to make use of conventional AGC algorithm which only uses one window size in order to estimate the power of signal and regardless of the different bands. The proposed hybrid AGC algorithm is made up of two steps: the first step is synthetically to utilize large window size and small window size, simultaneously improving performance of adaptation time and stability; the second step is based on two AGCs which are designed to be matched well with low-band and high-band signals separately.