Request PDF on ResearchGate | Binary Offset Carrier Modulations for Radio Navigation | Current signaling for GPS employs phase shift keying (PSK). Abstract: Current signaling for GPS employs phase shift keying (PSK) modulation using conventional rectangular (non – return to zero) spreading symbols. The first model defines the BOC modulation as the result of . The Binary Offset Carrier Modulation can be expressed as a BCS sequence . [J.W. Betz, a] J.W. Betz, Binary Offset Carrier Modulations for Radionavigation.
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Simple logic indicates whether the prompt tap is no longer tracking the main peak and directs radionavivation to maintain track of the main peak. To distinguish between the two, equation 13 defines the RMS bandwidth using the normalized bandlimited power spectral density, and the loss of power is accounted for separately through equation The spectral separation coefficient of BOC 10,5 indicates the degree to which the modulation is isolated from the new military signal, so that high-power M-code signals do not interfere with its reception.
Eurasip Journal on Wireless Communications and Networking. The binary offset carrier BOC modulation binarh developed for this purpose . Even BOC 5,2 has better code-tracking accuracy than Comparing the code-tracking errors in the preceding figures rsdionavigation corresponding discriminator gains plotted earlier reveals an important insight.
Considered in this sense, the BOC modulation generalizes a Manchester modulation to more than one zero crossing per spreading symbol i. Figure 3 portrays the spectra of As long as the subcarrier frequency is not excessive e.
Binary offset carrier modulation
In the power spectral density, the sum of the number of mainlobes and sidelobes between the mainlobes is equal to n, twice the ratio of the subcarrier frequency to the code rate. Other practical factors that preclude use of excessive subcarrier frequencies include difficulty in acquiring the correlation function peak and sensitivity to channel imperfections, such as dispersive effects of the ionosphere and RF hardware, including antennas. While the set of measures does not completely define the design space, it does provide important insights into the suitability of a modulation for radionavigation.
For a given relative amplitude of the specular reflection, the bias error introduced into code tracking can be computed for a given multipath delay d. While this bandwidth restriction would cause codetracking error for a 1.
For an ideal BOC modulation with infinite bandwidth, the autocorrelation function consists of a set of connected line segments with in general multiple zero crossings and multiple lobes. For example, when the subcarrier frequency is much greater perhaps by more than a factor of 10 than the spreading code rate, the correlation function has many closely spaced in amplitude and delay peaks that can introduce anomalous effects in code tracking.
Another motivation for sideband processing of BOC modulations is interference avoidance. While there has been previous consideration of subcarrier modulations for civilian signals e.
Through the continuing development of innovative modulations and prudent use raionavigation modulation attributes such as those employed in this paper, there will be ongoing opportunities to design signals that can be readily implemented, efficiently share spectrum with other signals used for radionavigation, and provide opportunities for enhanced performance.
The normalized scaled so that main peaks have unit height autocorrelation functions are portrayed in Figure 4, showing the narrower peak and multimode structure of the BOC 10,5 correlation function.
This class of offset carrier modulation has been termed linear offset carrier, since its modulus takes on a continuum of values. The correlation function from sidelobe processing is a bandlimited version of the correlation function for a PSK-R modulation at the spreading code rate of the BOC modulation — a much broader correlation function than that of the dual-sideband BOC modulation.
This lower bound is based on the performance of a maximum-likelihood estimator of time of arrival using T seconds of data, driving a tracking loop. Since it would serve as a new civil signal within L1 and L2, Vol. When n 1, equation 8 becomes sin f Ts f Ts 2 so that qnTs t consists of n half-cycles of a square wave, that is, n alternating values of 1 and 1. However, the worst-case bias error is slightly greater 5.
While this reduction in front-end bandwidth causes the worst-case multipath error for 1. The columns for BOC 10,5 modulation and When code-tracking errors are small so that a linearized analysis applies, the variance of the code-tracking error for NELP in Betz: In fact, use of a BOC 5,1 or BOC 5,2 modulation allows high-performance receivers to employ front-end bandwidths as narrow as 12 MHz with almost no performance degradation as compared with wider bandwidths, offering the opportunity for exceptional performance with compact antennas and lower-power electronics.
Yet another way to verify this asymptotic behavior is to recognize that, with vanishing early — late spacing, early — late processing approaches an ideal differentiator, which is the maximum-likelihood estimator of time of arrival in white Gaussian noise.
Air Force under contract number FC For BOC 5,1n 10, and the correlation function has 19 peaks, as predicted. For early — late spacing of less than 45 ns, the code-tracking accuracy closely approaches the information-theoretic lower bound computed using equation 14indicating little benefit from using smaller early — late spacings.
Betz_Binary Offset Carrier Modulations for Radio Navigation_百度文库
The S-curve relates the correction produced by a discriminator for a given error. More recent work suggests that BOC modulations may allow yet another signal, in addition to heritage signals and the new military signal, to be added to currently allocated GPS bands .
By providing almost 7 dB better spectral separation with itself than is provided by 1. Figure 20 shows similar results for BOC 5,2 and 1. First, it has introduced a set of quantitative measures that can be used to assess the capability of different modulations. For BOC 5,2n 5, and the correlation function has 9 peaks, as predicted. For early — late spacing of less than 50 ns, the code-tracking accuracy closely approaches the information-theoretic lower bound computed using equation 14 offxet, indicating little benefit from using smaller early — late spacings.