###### Abstract  
The design of an integrated sensing and communication (ISAC) waveform compatible with the 5G new radio (NR) system is crucial in enabling ISAC by utilizing the hardware of existing base stations (BSs). In this paper, we design an inner-frame time division multiplexed sensing waveform in the frame structure of 5G NR to achieve ISAC. The designed waveform is computed by the simulated annealing algorithm on an optimization cost function of a constrained combination of the peak-to-sidelobe ratio (PSLR) and the integrated sidelobe ratio (ISLR) of the velocity ambiguity function. Specifically, the constraints are the 5G communication protocol and 5G NR frame structure. In addition, we conducted corresponding signal detection and estimation methods to illustrate the performance of the sensing waveform. Both theoretical analysis and simulation experiments show that the designed waveform can effectively achieve target detection and parameter estimation under low sensing cost conditions. OFDM; 5G new radio (NR); integrated sensing and communication; waveform design 2023  
2323685  
most widely used communication-centric waveform is the orthogonal frequency division multiplexing (OFDM)-integrated radar and communication waveform. OFDM waveforms provide high communication data rates and the ability to efficiently deal with frequency selective fading. Hence, many researchers have investigated the OFDM-integrated radar and communications waveform [18; 19; 20; 21; 22; 23; 24; 25; 26; 27]. In [18; 19], the authors proposed a waveform design method that maximizes the weighted sum of the communications data information rate (DIR) and the conditional mutual information (MI) between the observed signal and the random target impulse response over the entire uncertainty class. Moreover, Ref. [20] proposed an adaptive waveform design method by maximizing the mutual information (MI), subject to the subcarrier power ratio, energy constraints, and communication channel capacity. Ref. [21] considered the MI between the frequency-dependent target response and the transmit OFDM waveforms. Ref. [22] proposed minimizing the Cramer-Rao bound (CRB) on the delay-Doppler estimation, subject to an integrated side-lobe level (ISL). Ref. [23] transformed the optimal waveform design problem by designing subcarrier coefficients for optimal power allocation and phase coding. The above methods add a coefficient before the subcarrier of the OFDM waveform and use different optimization criteria to achieve the optimal waveform design. In addition, [24] proposed maximizing the energy efficiency (EE) and sum rate (SR) of the ISAC system. However, radar and communications require the use of different transceiver antennas. In [25], the concept of shared and private subcarriers is proposed, where shared subcarriers are used to realize the communication function, and private subcarriers are used to assist sensing. When the number of private subcarriers is increased, the sensing performance improves, but the communication rate decreases. In [26], a sensing-integrated discrete Fourier transform spread OFDM system is proposed for THz ISAC. The authors of [27] proposed a joint radar-communication system with offset quadrature amplitude modulation-based orthogonal frequency division multiplexing (OQAM-OFDM). Although communication-centric waveforms can achieve a high data rate, the sensing performance suffers due to the random autocorrelation property and the high peak-to-average-power ratio of the transmitted waveform. With the advent of the 5G era, 5G base stations (BSs) have widely being deployed around the world. The utilization of existing 5G BS hardware to achieve ISAC offers advantages such as low cost and rapid deployment. Therefore, many researchers are looking at how to utilize existing 5G BS hardware to achieve ISAC [28; 29; 30]. [PERSON]. [28] optimized the ISAC waveform by filling the empty subcarriers of a 5G BS working in downlink mode and optimizing the transmission power of some of the communication subcarriers.