# Design and Performance Analysis of Navigation Signal Based on OFDM
###### Abstract  
This paper proposes a new navigation modulation based on orthogonal frequency division multiplexing (OFDM). We derived the autocorrelation function and power spectral density of the OFDM modulation. The influence of the cyclic prefix and zero-padding is discussed. The influence of OFDM modulation parameters on navigation signal performance was deeply analyzed, which can help signal designers choose the OFDM parameters. The main peak of the proposed autocorrelation function is narrow and has good tracking accuracy. The sidelobe is lower, and the delay locking loop is more robust. The power spectrum density is evenly distributed  
the level of physical signals. The integration design of communication and navigation at the signal system level is the foundation of fusing the two systems and is also a hotspot of current research. The on-on fusion at the signal design level can increase spectrum utilization and reduce resource occupancy. At present, many scholars in related fields have conducted a lot of research on the signal system design of communication fusion, mainly including a signal design based on mobile communication and other communication systems. The orthogonal frequency division multiplexing (OFDM) was first presented by [PERSON] [10; 11; 12] and was developed by [PERSON] and [PERSON] [13] and [PERSON] [14]. [PERSON] and [PERSON] proposed an adaptive technique in designing the spectrum of orthogonal frequency division multiplexing (OFDM) waveforms to improve the broadband ambiguity function of the signal. Adaptive OFDM signals produce better autocorrelation functions (ACF), thus improving the delay (range) resolution of the system. This design scheme can place more signal energy on sub-carriers with a weak target response [15]. [PERSON] et al. introduced constant envelope OFDM signals, which combined OFDM and phase modulation or frequency modulation; this effectively solved the problem of OFDM signals being vulnerable to the influence of system nonlinearity because of their large fluctuations [16]. [PERSON] et al. proposed a new OFDM-based waveform (TS-W-OFDM). TS-W-OFDM uses a windowing program to improve the spectral efficiency. Compared with the traditional cyclic prefix of OFDM, the windowing OFDM (W-OFDM) and weighted overlap and addition-based OFDM (WOLA-OFDM), TS-W-OFDM had a higher spectral efficiency and almost the same error rate, and its complexity was lower than that of W-OFDM, WOLA-OFDM, and F-OFDM [17]. [PERSON] et al. proposed an OFDM signal design scheme with an adaptive structure based on maximizing the mutual information of the transmitted waveform between the random target impulse response and the received echo, taking advantage of the benefits of the OFDM signal. Compared with the non-adaptive waveform design method, the proposed method achieved a higher performance [18]. The time & code division-OFDM signal system, proposed by [PERSON] et al. is a typical technology for the design of pass-through fusion signals. By superimposing the navigation signal onto the OFDM signal, the TC-OFDM signal can be realized. At the same time, the continuous acquisition and tracking of positioning signals are realized [19]. [PERSON] proposed a frequency domain composite OFDM modulation scheme, which applied a spread spectrum sequence to frequency domain modulation combined with OFDM in a communication system. The author studied the fusion method of communication and navigation signals from the level of signal modulation and achieved a good compatibility of pass-through signals [20]. [PERSON] proposed the integrated waveform design of communication and navigation systems based on spread spectrum modulation, where the author evaluated the interaction between the communication and navigation components [21]. [PERSON] et al. proposed a new signal modulation scheme named CE-OFDM-PM, which is suitable for the S-band and has a wide normalized power spectral density (PSD) and high main peak sidelobes ratio. It is capable of high tracking accuracy, and the code tracking accuracy can reach 0.85 m [22].