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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One example in which single-sideband processing might be useful is in a portable wireless device, such as a cellular telephone, that includes a radio navigation satellite service RNSS receiver.
Viewed another way, obtaining the same codetracking error with 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. The error becomes very large for early — late spacing near ns, corresponding to the slope reversal in the S-curves observed in Figure Both fit readily within the 24 MHz allocated bandwidth. By moving signal power away from the band center, they offer the potential for better code-tracking accuracy and multipath rejection.
The maximum of the power spectral density for the BOC 5,2 modulation is more than 6 dB lower than that for 1. Based on similar results for code-tracking accuracy in Figures 15 and 16, it is clear that BOC 5,2 allows reduced receiver front-end bandwidths with less receiver complexity, with very little effect on performance. While the signals are designed to occupy the 24 MHz allocation, the 30 MHz bandlimiting approximates that which occurs at GPS satellites.
Betz_Binary Offset Carrier Modulations for Radio Navigation_百度文库
To examine the effect of multipath on the code tracking of different modulations using NELP, consider a simple model of multipath as a specular reflection having some amplitude relative to the direct path, arriving at some phase and delay, with all values time-invariant over the time period of interest. Spectra and Correlation Functions of Binary Offset Carrier Modulations Assume that the binary values of the BOC spreading sequence values are equally likely, independent, and identically distributed.
The 90 percent power bandwidth indicates the complex bandwidth needed to pass 90 percent of the signal power. Quantized radio modulation modes. Also, increasing transmitted power to improve accuracy is expensive and has a limited effect on multipath fro. Furthermore, the redundancy in the upper and lower sidebands of BOC modulations offers practical advantages in receiver processing for signal acquisition, code tracking, carrier tracking, and data demodulation. As in conventional PSK, the zero crossings of each mainlobe are spaced by radoinavigation the code rate, while the zero crossings of each sidelobe are spaced at the code rate.
Figure 3 portrays the spectra of Figure 13 shows results for BOC 10,5 modulation, computed using equation BOC 10,5 provides slightly better spectral separation with itself, allowing more signals with greater power variation. Since the moeulations in this paper is on modulation design, long spreading codes are assumed, leading to smooth spectra without spectral lines.
The author thanks the anonymous reviewers for many useful suggestions that improved the presentation of the paper, and especially one reviewer for suggestions that simplified the derivation in the appendix. In contrast, n 5 for a BOC 5,2 modulation, and its spectrum has three sidelobes between the two mainlobes, while n 10 for a BOC 5,1 modulation, and its spectrum has eight sidelobes between the two mainlobes.
The zero crossings nearest the main peak occur at approximately 51 ns. For example, while Figure iffset shows that discriminator gain increases as early — late spacing decreases from 40 ns, Figure 13 shows that there is no further reduction in code-tracking error.
Binary offset carrier modulation – Wikipedia
This paper has provided two categories of fundamental results in modulation design. There is a very close relationship between these variations of offset carrier modulations; in fact, a linear offset carrier modulation can be processed by a receiver using a BOC reference signal having the same subcarrier frequency and code rate with very little raadionavigation on performance. The binary offset carrier BOC modulation was developed for this purpose [2]. Design [ edit ] The tor idea behind BOC modulation is to reduce the interference with BPSK -modulated signal, which has a sinc function shaped spectrum.
Code tracking of the dual-sideband signal is based on well-known techniques developed for PSK-R modulations.
The spectral separation coefficient of BOC 10,5 indicates the degree to which the modulation is isolated from the new military signal, so that rafionavigation M-code signals do not interfere with its reception. Figure 17 compares code-tracking accuracy for the set of modulations considered in this paper, using a 24 MHz front-end bandwidth, a code-tracking loop with equivalent rectangular bandwidth of 0.
Considered in this sense, the BOC modulation generalizes a Manchester modulation to more than one zero crossing per spreading symbol i. The quantities and t0 reflect arbitrary offsets in phase and time, respectively, in the complex envelope relative to some reference.
A very small antenna and simple RF electronics having only enough bandwidth to pass one sideband, combined with the reduced sampling rate and processing throughput requirements associated with the bandwidth of one sideband, would help minimize the cost, size, and power consumption of the receiver. Yet the BOC 8,4 modulation provides slightly 0. BOC modulation moddulations several variants: This carrier processing is identical to that for PSK-R modulations, and also supports conventional approaches for data demodulation.
A conventional code-tracking loop can be used with a discriminator based on early — late rarionavigation or an analogous approach. A BOC modulation is denoted BOC fs,fcwhere fs is the subcarrier frequency, and fc is the code rate, defined by fs 1 2Ts 2 Consistent with the convention introduced in [2] and followed subsequently in work on GPS and elsewhere, offzet designation BOCused in this paper is an abbreviation.
Figure 9 shows the cumulative spectra of the five specific modulations being considered. Views Read Edit View history.
Binary offset carrier modulation
Comparing the columns for the BOC 8,4 modulation and 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. As long as an appropriate form of extended range correlation see [10], for example is used to ensure that the main peak of the correlation function is tracked, the shape of the S curve away mdoulations the zero crossing point does not describe how the code-tracking loop behaves.
In some applications, however, the implementation simplicity afforded by radionavigarion opportunity to process narrower bandwidths may offset these disadvantages. The sidelobes of BOC modulations allow the use of additional processing in the discriminator to maintain code track even under stressed conditions. Generation of data, spreading code, subcarrier, and RF uses a common clock so that zero crossings are aligned.
The subcarrier frequency is actually 1. Figure 20 shows similar results for BOC 5,2 and 1.
