Hybrid Amplitude and Phase Coding for Intelligent Reflecting Surface Aided Channel Estimation

The channel estimation techniques for intelligent reflecting surface (IRS)-assisted communication are investigated in this paper. IRS-aided communications rely on the accurate and efficient channel estimation of IRS component-related channels. But conventional channel estimation methods are inefficient due to the sequential estimations of pilot signals. This paper proposes a hybrid coding method, which changes the amplitude and phase of the signal over time and generates two pilot signals at the required frequencies to estimate the channel using interpolation. By using this method, a new send-and-reflect estimation scheme is proposed for separated channel estimation. The method is evaluated based on discrete and continuous coding, respectively. Numerical results show that the proposed method significantly reduces the channel estimation time with a trivial penalty on transmitting accuracy. Besides, the feasibility of discrete hybrid coding is also validated through simulations.