However, due to the successive interference cancelation (SIC) employed to separate navigation messages from communication data, the computational burden on the receiver to process multi-satellite signals is substantial. Furthermore, the proposed signals in [36; 37] must process the entire bandwidth to demodulate the data used for navigation, which undoubtedly increases the processing burden on the navigation receiver. In summary, the existing INAC waveforms still face the following challenges: (1) A high-power communication signal impacts the correlation function of the navigation signal in waveforms that share frequency bands, thereby limiting ranging accuracy. (2) The complexity of receiving navigation signals is quite high. Navigation receivers typically process signals from dozens of satellites [38], while broadband LEO satellites usually operate in the Ka, Ku, and C frequency bands, with signal bandwidths exceeding hundreds of megahertz, imposing a significant burden on signal processing. (3) Data transmission reliability is poor in high-mobility channels. OFDM-based signals experience severe ICI in high-mobility channels, leading to a significant increase in BER. We focus on the design of an INAC waveform based on OTFS to address these three issues, inspiring LEO PNT applications while ensuring communication reliability in high-mobility channels. Specifically, the contributions of this paper include the following four aspects:  
1. A delay-Doppler block division multiplexing (DDBDM) waveform is proposed. The navigation PRN codes and communication data are modulated on two-dimensional orthogonal basis functions in the DD domain, and this orthogonality limits MI, making it easier to improve ranging accuracy. Meanwhile, data transmission in the DD domain ensures reliability of communication. 2. By independently transforming navigation and communication signals across different DD blocks, they are separated in the frequency domain. This allows users to receive the navigation signal independently, without the loss of useful power, thereby reducing the signal processing overhead. Additionally, the dedicated broadcast signal enables continuous and passive positioning, facilitating easier collaboration with the GNSS. 3. We propose a navigation receiver architecture for DDBDM that extracts continuous and accurate measurements. The proposed acquisition and tracking structure is compatible with traditional navigation receivers, facilitating the simplification of receiver design and reducing the development costs for user equipment (UE). Furthermore, we implement a software-defined radio (SDR) prototype of the INAC system to validate the design of the proposed architecture. Simulation results indicate that the proposed waveform exhibits superior comprehensive performance compared to existing schemes. The ranging accuracy of DDBDM is higher than that of ZC-NOMA, PN-OTFS, and RP-OTFSM, with the same bandwidth. Even with an 80% reduction in the signal bandwidth of DDBDM, the ranging accuracy remains higher than that of PN-OTFS and RP-OTFSM, and it also surpasses that of ZC-NOMA when the signal-to-noise ratio (SNR) is greater than 10 dB and the communication-to-navigation power ratio (CNPR) is 30 dB. In LEO high-mobility multipath channels, DDBDM has a lower BER compared to the other schemes, thus providing reliable communication. It also aids in the transmission of broadcast messages to reduce the time to first fix (TTFF) for navigation receivers and to provide information augmentation services. The remainder of this paper is organized as follows. Section 2 introduces the system model and elucidates the problem of the original OTFS. Section 3 introduces the proposed waveform and elaborates on the steps of signal generation. Section 4 proposes the navigation signal processing method. Section 5 evaluates the navigation and communication performance and implements the prototype of the INAC system. Finally, the paper is summarized in Section 6.