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Due to the spectrum congestion of current navigation signals in L-band, C-band has been taken into consideration as a candidate frequency band for global navigation satellite system (GNSS). As is known, modulation scheme is the core part of signal structure, and how to design a modulation waveform that could make full use of narrow bandwidth 20 MHz...
Citations
... The multipath error envelope reflects the sensitivity of a code tracking loop to multipath signals with different parameters. When only one multipath signal exists, the multipath error envelope of the coherent code tracking loop is [41]: ...
Continuous phase modulation (CPM) has the characteristics of high power efficiency, spectral efficiency, and less out-of-band radiation, which is very suitable for the Compass S-band (2483.5–2500 MHz) with limited power and bandwidth. However, as more and more navigation systems share the S-band, the mutual interference between different systems is gradually increasing, and the compatibility of CPM signals with rectangular or raised cosine pulses needs to be further improved. To enhance the navigation performance and compatibility of current CPM candidate signals, we propose to apply continuous phase modulation with prolate spheroidal wave function (CPM-PSWF) to S-band navigation. The proposed modulation scheme selects PSWF with excellent time-frequency energy aggregation and flexible time-bandwidth product as the frequency pulse function of CPM. Then, the influence of key modulation parameters such as M , L , h , and C on CPM-PSWF power spectral density is analyzed, and a specific partial-response CPM-PSWF signal is proposed as the S-band candidate navigation signal. Finally, the navigation performance evaluation criteria are derived, and the proposed signal scheme and existing candidate schemes are comprehensively evaluated. Theoretical analysis and simulation results indicate that compared with CPM with B M 2RC(8), cos-phase binary offset carrier (BOCc(4,4)), sin-phase binary offset carrier (BOCs(4,4)), minimum shift keying-BOCs (MSK-BOCs(4,4)) and binary offset carrier (BPSK(8)), the proposed signal scheme not only delivers exceptional spectral performance but also exhibits superior performance in code tracking accuracy and multipath suppression. In addition, in the acquisition and tracking phase, compared with other candidate signals except for BOCc(4,4), the mutual interference between the proposed signal scheme and most S-band signals is the lowest, which is easier to realize the compatibility of the Compass system with IRNSS, Galileo, and Globalstar systems.
... Additionally, the inherent constant-envelope property of legacy BOC or BPSK signal is undermined through the band-limiting filter, since their phase discontinuity causes time fluctuations with a magnitude increasing with the mount of phase jump incurred [20]. Consequently, such modulation schemes with constant envelope and continuous phase will be top priority for future GNSS, notably in C band [21]. ...
Continuous phase modulation (CPM) is a power and spectrum efficient modulation that intrinsically possesses constant envelope, phase continuity as well as less out of band (OOB) radiation, especially appropriate for stringently bandwidth-constrained systems employing non-linear power amplifiers. Such advantages render CPM as a promising modulation candidate with application to satellite navigation. CPM comprising of a few parameters has large amounts of modulation subclasses. This paper is devoted to optimal parameter design of CPM for future GNSS signals. Parameter design approaches endowing CPM with similar spectrum profiles as legacy binary offset carrier (BOC) and binary phase shift keying (BPSK) modulations are also proposed. Several optimal subclasses of CPM family are suggested as unimodal or bimodal GNSS signal solutions. The simulation results indicate that the designed CPM signals behave same or similar main lobes with BPSK and BOC signals, and proposed optimal subclasses of CPM family with high spectral efficiency are comparable or superior than legacy modulations, typical GMSK, and filtered multitone (FMT) signal using the squared root raised-cosine (SRRC) basic pulse in terms of tracking accuracy, multipath mitigation and compatibility. In addition, some constructive comments on CPM design are presented, which provides a reference for CPM applications in GNSS.
... Yinjiang Yan etc. provided the rain attenuation analysis of C-band navigation signal [9]. Rui Xue etc. proposed continuous phase modulation to reduce signal sidelobes and analyzed its performance [10,11]. Ying Wang etc. studied the technology and prospect of Cn band navigation [12]. ...
As the only priority frequency band for navigation services except L protected by ITU, the Cn band could provide navigation services to solve problems of spectrum congestion and vulnerability to interference faced in L using global navigation satellite systems. However, Cn band navigation still faces some problems such as limited-bandwidth and link uncertainty. To solve these problems, an orthogonal MSK signal is designed in this paper under Cn limited bandwidth constraint. The analysis results show that although it’s ranging performance of narrow correlation spacing has been deteriorated, the performance of wide correlation spacing has been improved, and it can reduce 98.7% power interference to adjacent radio astronomy band. On the other hand, the Cn band navigation signal test based on the satellite-to-ground link is carried out in this paper. The test results show that the trend of designed signals’ ranging performance is consistent with the simulation results and its rain attenuation is 0.5–1dB.
... In order to illustrate the resistance against multipaths of a given spreading modulation, the multipath error envelope (MPEE) [IAARH05] [XSZ15] [XCW15] is computed. The MPEE assumes a multiple ray model to quantify the worst possible multipath effect. ...
... At the World Radio Communications Conference in 2000, the 5010 MHz to 5030 MHz part of the C-band was assigned for Radio Navigation Satellite Services (RNSS) air-to-ground applications, whereas the 5000 MHz to 5010 MHz part of the C-band was assigned for RNSS ground-to-air applications [1]. The adjacent frequency bands for the Radio Astronomy Service (RAS, 4990 MHz to 5000 MHz) and the Microwave Landing System (MLS, 5030 MHz-5150 MHz) have strict restrictions on out-ofband radiation, and the compatibility between uplink GNSS signals and downlink GNSS signals must also be considered [2]. According to the ITU rules, the PSD (normalized power spectral density) of signals in frequency band 4990-5000 MHz cannot exceed -129.5 dB/Hz, the PSD of signals in frequency band 5030-5150 MHz cannot exceed -64.8 dB/Hz. ...
... where (t) is a function defined in [0, T c /2). It can be verified that the pulse waveform defined by (3) satisfies the conditions required by (2). Thus, the I&Q waveform joint optimization problem was transformed into a phase trajectory optimization problem, which is shown as follows. ...
As the L-band spectral resources for GNSS services are almost exhausted, new bands such as S-band and C-band has been considered for new GNSS signals. In addition to the traditional signal features, out-of-band radiation is an important factor to be considered for signal designing in these new bands. In this paper, a mathematical model for the optimization of GNSS signal waveforms was constructed by integrating ranging accuracy, antijamming performance and out-of-band radiation suppression requirements. In combination with numerical optimization methods, a spectrally efficient constant envelope modulation scheme based on phase trajectory optimization was proposed. The modulated signal has a full-response continuous phase waveform, which facilitates signal processing and implementation at both ends of the transmission and reception. In addition, in the signal design, the balance between signal accuracy, anti-interference performance and out-of-band radiation suppression can be achieved through the adjustment of the weight coefficient. The simulation results show that the out-of-band radiation can be reduced by about 7.2-42.7 dB compared with the existing scheme when the signal performance difference is lower than 2 dB.
... CPM has been widely used in many systems by now, such as satellite communications [9], [10], satellite mesh networks [11], [12], digital video broadcasting (DVB) [13], [14], fiber-optical communications [15], telemetry [16], [17], and so on. In addition, our previous research results have indicated that certain CPM solutions can not only meet the compatibility requirement in the band S or C and reduce the complexity of user terminal, but also provide a better performance in the aspects of tracking precision, multi-path mitigation and antijamming compared to other modulation candidates [18], [19]. Consequently, it is feasible to design an integrated signal model of communication and ranging based on the CPM signals. ...
The inter-satellite links (ISLs) will play an increasingly important role in improving the service performance and enhancing the survivability of global navigation satellite systems (GNSSs).The current signal transmission schemes in ISLs primarily employ constant coded modulation (CCM) to guarantee a high reliable communication even for the worst channel status, and the adaptive coded modulation (ACM) schemes such as binary low-density parity-check (LDPC) coded quadrature phase shift keying (QPSK) or M-ary quadrature amplitude modulation (MQAM) have been introduced to improve spectral efficiency over inter-satellite channels recently. However, the phase discontinuity of the above modulations will widen frequency spectrum and cause the high-voltage transient of transmitter, and the MQAM signal through high power amplifier (HPA) onboard will result in non-linear distortion because of non-constant envelope. In this study, the association between non-binary LDPC (NB-LDPC) codes and high-order partial response CPM (PRCPM) with iterative detection is presented as the source of ACM schemes, which effectively inhibits information loss in the process of conversion between bit and symbol probabilities. According to the constellation of BeiDou navigation satellite system (BDS) in 2020, an open loop ACM control mechanism based on inter-satellite distance is introduced, and implemented by the target bit error rate (BER) and the maximum ratio between throughput and bandwidth (T/B) algorithms. Simulation results show that the proposed ACM scheme can reduce the BER and improve the power efficiency in the requirement of target BER limit, and provide a higher spectral efficiency under the same transmitting power compared to the existing ACM scheme.
... These distortions directly affect the correlation properties of the signal and have a direct consequence to the discrimination function used on the receiver. In order to evaluate such as distortion, the MPEE [9] [17] [18], which quantizes the bias error induced by the multipath, is computed. ...
... The anti-jamming capability is predicted based on four parameters [16] [17] [18] based on the effective carrier to noise density ratio ( / 0) [2], which indicates the level of interference at the input of the receiver. Higher anti-jamming coefficients involve less vulnerability to the jamming attacks. ...
... & antijamming of narrowband Dem&AJNB = 10 10 ( 1 * max ( ( )) ) [18] ...
... With the development of GNSSs and regional navigation systems, such as Japanese Quasi-Zenith Satellite System (QZSS) and Indian Regional Navigation Satellite System (IRNSS), the number of navigation signals in space is anticipated over 400 by 2030 [3], which will further aggravate an already crowded radio spectrum in L-band (1164 ∼ 1610 MHz) and negatively impact the new signal scheme design due to excessive spectrum overlapping [4]. Meanwhile, compatibility and interoperability among different navigation systems are becoming a hot research topic around the world in recent years [5][6][7]. ...
Ranging code is the core component of the signal transmission scheme in any global navigation satellite system (GNSS); its performance directly influences on the technical indexes of positioning accuracy, compatibility, interoperability, anti-interference, security, synchronization realization, and so on. Therefore, research on ranging codes could provide theoretical support for the improvement of the performance of ranging codes and extension of their design methods to future satellite navigation signal structures. In order to improve the balance in classical chaotic sequences, a novel ranging code is proposed in this paper and constructed by a series of the improved Logistic-map chaotic sequences with different initial values through weighted optimization, summation, and quantization. Then a comprehensive performance evaluation method based on the Welch bound including three main indexes has been introduced, namely the performance of acquisition, tracking, and robustness against interfering narrowband signals. Finally, the three indexes are combined in a cost function by weighting to evaluate the proposed code, coarse/acquisition (C/A), Gold, Weil, and Random as well as the conventional chaotic codes, and the corresponding weighted coefficients can be adjusted flexibly according to the user groups or application types. Theoretical analysis and simulation results over an additive white Gaussian noise (AWGN) channel show that the proposed ranging code cannot only demonstrate excellent performance in acquisition and anti-narrowband interference while maintaining high quality in tracking performance as the C/A code but also significantly improve balance performance and strengthen reliability and security.
The construction of a navigation constellation with inter-satellite links (ISLs) has become one of the important development trends for new-generation global navigation satellite systems (GNSSs), and ISLs currently realize navigation and communication functions through separate low-rate omnidirectional telemetry, tracking, command and high-rate data service channels, respectively. If the above two functions are integrated into one channel, this will result in simplification of the onboard equipment, improvement of the electromagnetic compatibility, power consumption reduction and frequency resources savings, and we speculate that autonomous navigation will be achieved by ISLs with navigation and communication fusion. In this paper, a system capable of simultaneous high-data rate communication transmission and precision ranging is investigated, and a specific scheme is introduced by combining continuous phase modulation (CPM) and a pseudonoise (PN) ranging code denoted as CPM+PN. The chip pulse is one of the key factors to design the ranging code, which not only affects the ranging performance but also influences the properties of the CPM+PN scheme, such as its spectral characteristics, communication reliability, and acquisition time. To consider the above performance indexes, a new chip pulse based on a normally distributed wave is proposed. Theoretical analysis and simulation results show that compared to square-wave and half-sine wave cases, the normally distributed wave attains great advantages in the ranging accuracy and communication reliability, which become more notable with reasonable selection of the energy distribution index. Moreover, the proposed chip pulse achieves a similar acquisition time as the traditional wave. As a result, the normally distributed wave can be used as a better alternative to the ranging chip pulse for the CPM+PN waveform.
