## 1 Introduction  
Facing the arrival of the 6G communication era, the proliferation of wireless communication devices is inevitable, and spectrum resources will become even scarcer. In the design of lightweight systems such as earthquake relief, intelligent transportation, and smart agriculture, the integration of independent radar and communication devices may result in system redundancy [1]. To efficiently utilize spectrum and hardware resources, radar communication spectrum sharing (RCSS) is categorized into two research lines: radar communication spectrum coexistence (RCC) and radar communication integrated system (DFRC) [2]. Regarding joint radar and communication systems, the core issue is the integrated waveform design. Therefore, there is a need to design a new multiplexed waveform that can carry communication information and be used for target detection at the same time. Integrated signals can be classified into two major categories: multiplexed signals and shared signals [3]. The performance of multiplexed signals depends on their ability to suppress interference between radar and communication through multiplexing techniques. However, under the constraints of simultaneous frequency and spatial sharing, multiplexing techniques limited to code division multiplexing do not meet the orthogonal requirements defined by the radar ambiguity functions. Also, code division multiplexing is more prone to co-frequency interference [4; 5; 6]. In the case of shared signals, radar-shared signals are used to carry communication information by adjusting the parameters of the radar signal [7; 8]. To ensure the detection performance of the radar, this method has a few adjustable parameters. And the communication data rate of the radar-shared signals is low because the communication channel estimation and channel equalization are not considered [9; 10; 11]. Therefore, with a focus on orthogonal frequency-division multiplexing (OFDM), communication-shared waveforms are currently a research hotspot [12; 13; 14; 15]. An integrated signal design, a processing scheme for radar communication based on OFDM, has been proposed by both [PERSON] et al. [16] and [PERSON] et al. [17]. [PERSON] et al. summarized the research and progress on integrated waveform design, highlighting that communication-shared signals based on OFDM are the most favorable integrated signal scheme [18]. [PERSON] et al. achieved the integrated waveform design by separately modulating radar and communication functions using orthogonal frequency-division multiplexing with zero padding (ZP-OFDM) signals [19]. They improved radar detection performance by avoiding false targets introduced during detection through blank guard intervals. Even if the length of the zero padding (ZP) is greater than the maximum delay of the multipath channel, a small symbol timing offset (STO) will cause discontinuities in the OFDM symbols within the effective period inside the FFT window. Additionally, compared to the orthogonal frequency-division multiplexing with cyclic prefix (CP-OFDM) symbols, ZP-OFDM symbols will introduce higher out-of-band power. Therefore, to enhance the system's robustness against channel-induced distortion, this paper integrates the cyclic prefix (CP) and virtual carriers (VC) into the composite signal. Furthermore, to reduce communication error rates, we introduce low-density parity-check (LDPC) in this system. On the receiver side, channel estimation performance is improved by the symbol timing offset (STO) estimation, the carrier frequency offset (CFO) estimation, and channel estimation techniques assisted by radar-based a priori information. During radar detection, the joint estimation of radar target distance and velocity is achieved by using matched filtering, pulse compression, and windowing to obtain the delay and Doppler frequency. We reduce the false alarm probability by setting a fixed threshold. The content arrangement of this article is as follows: Section 1 is an introduction, providing an improvement plan based on the current research status.