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Composite binary offset carrier (CBOC) signal has been widely researched in GNSS. The main ingredient of CBOC signal is BOC

With the development of wireless devices, radio environment is becoming more and more complex. Global Navigation Satellite Systems (GNSS) have to share the crowded frequency source and work in terrible environment with multipath or interference. Then, in 2004, the BOC modulation was proposed by the European Union (EU) and the US, which can be used for modernized civil Global Position System (GPS) signal on L1 band and Galileo Open Service (OS) on E1 band [

The MBOC modulated signal can be produced by CBOC or time-multiplexed BOC (TMBOC) signals. This new modulation allocates a wide band signal BOC

The main contributions of this paper are enumerated below:

An optimized acquisition technique named SSCM is proposed to remove side peaks and then the ambiguity problem can be restrained.

CBOC modulated signal is an important part of modern navigation systems. Some acquisition methods only use part of signal power to capture signal, while SSCM make full use of CBOC signal power. Then the acquisition performance is improved.

In order to overcome the complicated wireless environment, this method is suitable when the GNSS receiver works in a serious condition, which is based on the antijamming performance of modern GNSS signal.

The remainder of this paper is organized as follows. In Section

Several techniques have been proposed in the last ten years to overcome ambiguity problem. The BPSK-like method regards BOC or CBOC modulated signal as the sum of binary phase shift keying (BPSK) signals, using filtering, shifting, and integration to change the ACF shape into BPSK-like correlation function shape. Then, an unambiguous correlation function with a decreasing precision is obtained. However, the structure of BPSK-like method is complex and expensive to implement. The in-band noise of intermediate frequency (IF) signal will have an effect on acquisition. In [

In the new algorithm SSCM, a special auxiliary signal for CBOC modulated signal is introduced to remove side peaks. Moreover, the data channel and pilot channel signals are utilized completely, to ensure the detection probability. Additionally, the subtraction of the correlation channels is used to suppress in-band noise. This way, the side peaks are removed before signal detection. And the acquisition precision will be improved, which accelerates the tracking process.

CBOC signal is recommended and produced by BOC

The power spectrum and autocorrelation function of CBOC modulated signal are shown in Figures

PSD of CBOC signal.

Normalized ACFs of BOC

The subcarrier formula of BOC

CBOC

CBOC

For the case of a CBOC waveform on both data and pilot components, CBOC

In order to introduce the method, the baseband signal of CBOC

Based on the waveform of CBOC

Then, the correlation results (

Based on the fixed component and ratio of CBOC

Similarly, the correlation results

By calculating and comparing,

Correlation results of

Looking at Figure

From (

From formula (

Based on subtract operation, the noise of each channel is restrained, while the main peak value of correlation output is uninfluenced. Furthermore, by using

Architecture of SSCM algorithm.

Eight correlators are employed in this architecture. And the in-phase branches are omitted to simplify structure.

In order to analyze detection probability

Here

Then the four terms

And the test criterion without noise can be expressed as

According to the statistical theory [

In order to verify the effectiveness and validity of SSCM, it is necessary to analyze the efficiency in terms of correlation function, peak-to-average ratio (PAR) with different noise, detection probability

Figure

Normalized correlation functions of SSCM, ASPeCT, SCPC, and PCF.

Nonnormalized correlation functions of SSCM and PCF.

In CBOC

Along with SNR increasing from −35 dB to 0 dB, simulation shows that SSCM method own the best PAR than other three methods. From formula (

PARs of four methods.

With a fixed false alarm probability

The detection probabilities of both proposed technique and PCF method are drawn in Figure

Detection probability for CBOC,

In this paper, the principle and characteristics of CBOC

The authors declare that they have no conflicts of interest.

This work was supported by the National Natural Science Foundation of China (no. 61501309), the Program for Liaoning Innovative Research Team in University (no. LT2011005), New Century Program for Excellent Talents of Ministry of Education of China (no. NCET-11-1013), Project of Science and Technology Department of Liaoning Province (no. 20121038), and Project of Education Department of Liaoning Province (no. L2013085).