  Integrated sensing and communication (ISAC), with sensing and communication
sharing the same wireless resources and hardware, has the advantages of high
spectrum efficiency and low hardware cost, which is regarded as one of the key
technologies of the fifth generation advanced (5G-A) and sixth generation (6G)
mobile communication systems. ISAC has the potential to be applied in the
intelligent applications requiring both communication and high accurate sensing
capabilities. The fundamental challenges of ISAC system are the ISAC signal
design and ISAC signal processing. However, the existing ISAC signal has low
anti-noise capability. And the existing ISAC signal processing algorithms have
the disadvantages of quantization errors and high complexity, resulting in
large energy consumption. In this paper, phase coding is applied in ISAC signal
design to improve the anti-noise performance of ISAC signal. Then, the effect
of phase coding method on improving the sensing accuracy is analyzed. In order
to improve the sensing accuracy with low-complexity algorithm, the iterative
ISAC signal processing methods are proposed. The proposed methods improve the
sensing accuracy with low computational complexity, realizing energy efficient
ISAC signal processing. Taking the scenarios of short distance and long
distance sensing into account, the iterative two-dimensional (2D) fast Fourier
transform (FFT) and iterative cyclic cross-correlation (CC) methods are
proposed, respectively, realizing high sensing accuracy and low computational
complexity. Finally, the feasibility of the proposed ISAC signal processing
methods are verified by simulation results.
