IRS Aided Integrated Sensing and Communication Under Bistatic Configuration

We study a bistatic integrated sensing and communication (ISAC) system assisted by an intelligent reflecting surface (IRS). We propose two new algorithms, namely the channel aware algorithm and the low overhead codebook based channel agnostic algorithm to determine the IRS phase shift vector and the power allocation that maximize the probability of correct detection under minimum rate constraint of the communication user, transmit power constraint and unit modulus constraint at IRS. The channel aware algorithm ensures coherent addition of N out of the N2signal copies received at the sensing receiver (SR). For the channel agnostic algorithm, we consider two codebook based strategies, namely, the Discrete Fourier Transform (DFT) codebook and a codebook with phases drawn from a distribution that is uniform over the interval [0, 2π]. We show that as the number of IRS elements increases, the performance with uniform codebook approaches the performance with channel aware algorithm at substantially reduced pilot and control overhead. Furthermore, we also observe that by increasing the number of elements at the IRS (i) probability of detection PDcan be maintained at a fixed level with fewer observations at SR, (ii) significant savings in radiated power can be obtained at the base station, and (iii) the minimum rate offered to the communication user (CU) can be increased while maintaining PDor probability of false alarm at the desired level.