Nach oben pdf Positioning Performance Limits of GNSS Meta-Signals and HO-BOC Signals

Positioning Performance Limits of GNSS Meta-Signals and HO-BOC Signals

Positioning Performance Limits of GNSS Meta-Signals and HO-BOC Signals

a key player in the next-generation intelligent transportation systems and several safety-critical applications. However, even if the navigation research community has been developing positioning methodologies for decades, there are still several limitations that may limit the use of GNSS in the most stringent applications, i.e., lane-level precision for autonomous driving in highly populated cities with harsh propagation conditions. One of the key open problems is how to achieve precise PNT solutions under harsh environments, i.e., affected by multipath, deep fading, signal blockage, or non-line-of-sight (NLOS) conditions. Using standard GNSS signals, it is known that code-based techniques (i.e., only relying on the time-delay estimation between the receiver and a set of visible satellites) do not provide precise PNT information. The standard way to provide such precise navigation capabilities is by exploiting carrier phase information. Indeed, this measurement is linked to the wavelength, which is much smaller than the baseband signal resolution (i.e., for a legacy Global Positioning System (GPS) L1-C/A signal, the wavelength is 19.4 cm, while the baseband signal resolution is around 300 m). The two main solutions are precise point positioning (PPP) [ 1 ] and real-time kinematic (RTK) positioning [ 2 ]. However, the main problem of these techniques is that they are very sensitive to the quality of phase observables, i.e., it is unlikely that they provide a robust solution under harsh propagation conditions, at least exploiting standard GNSS signals. Therefore, in order to provide robust and precise solutions, new alternatives must be accounted for. A possible alternative is to robustify the signal processing, for instance resorting to outlier mitigation techniques [ 3 , 4 ]. Another option is to increase the receiver complexity and exploit large bandwidth signals, which allow obtaining a better (i.e., with respect to standard signals) baseband resolution, and therefore more precise code-based observables. The latter can be achieved by using (i) high-order binary offset carrier (HO-BOC) modulations or (ii) GNSS meta-signals, which is the combination of two GNSS signals at different frequency bands as a single signal.
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Positioning Using Terrestrial Multipath Signals and Inertial Sensors

Positioning Using Terrestrial Multipath Signals and Inertial Sensors

Today, most smartphones are equipped with global naviga- tion satellite systems (GNSSs) receivers which allow using applications on the smartphones for navigation [1]. GNSSs provide sufficient position accuracies for mass market appli- cation in open sky conditions. However, indoors or in urban canyons the GNSS positioning accuracy could be drastically reduced. In these situations, the GNSS signals might be blocked, degraded by multipath effects, or received with low power. To enhance the positioning performance indoors, different methods and sensor systems can provide position information rather than relying on GNSSs [2–4]. Most of the indoor positioning systems use local infrastructure like positioning with Radio Frequency Identification (RFID) [5], mobile communication base-stations [6, 7], wireless local area network (WLAN) [8], or ultra-wideband (UWB) [9– 11]. However, also these wireless radio technologies experi- ence multipath and non-line-of-sight (NLoS) propagation.
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Exploring Signals on L5/E5a/B2a for Dual-Frequency GNSS Precise Point Positioning

Exploring Signals on L5/E5a/B2a for Dual-Frequency GNSS Precise Point Positioning

Abstract: Due to its nature, Precise Point Positioning (PPP) depends on the GNSS measurements and quality of satellite correction products used to relatively quickly provide precise and accurate positions. With the rapid evolution of Global Navigation Satellite Systems (GNSSs), new frequencies and signals are being broadcast, which have a positive impact on PPP performance. This paper presents, for the first time, a comprehensive analysis of PPP performance from these new GPS, Galileo and BeiDou-2/3 signals, which are not yet commonly used for PPP, with correct mitigation of errors such as the estimation of GPS Block-IIF L5 variations. Satellite orbits and clocks, as well as GPS Block- IIF L5 corrections, are estimated in real-time using DLR’s RETICLE engine, while the user processing is performed with York University’s PPP engine. First, as a reference, PPP performance is assessed on widely used signals: GPS L1/L2, Galileo E1/E5a, and BeiDou-2/3 B1-2/B3. Horizontal and vertical rms of 2.3 and 2.6 cm, respectively, are achieved in static processing and 5.4 and 7.5 cm in kinematic processing after 1 h of processing using real-time satellite correction products. The compatibility of BeiDou-2 and BeiDou-3 on the shared B1-2/B3 frequencies is analyzed and discrepancies in the receiver clock are found. Next, since all three constellations share two common frequencies, the paper focuses on analyzing PPP performance of GPS, Galileo and BeiDou-3 on [L1, E1, B1] at 1575.42 MHz and [L5, E5a, B2a] at 1176.45 MHz. Horizontal and vertical rms of 6.9 and 7.1 cm are achieved in kinematic processing. The effect of the known GPS Block-IIF L5 biases is studied as well, as it is shown to affect the receiver position and clock, as well as the ionospheric estimates and ambiguities. Average improvements of 15% and 20% in the horizontal and vertical rms, respectively, are observed when these biases are mitigated.
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Multipath Assisted Positioning for Pedestrians using LTE Signals

Multipath Assisted Positioning for Pedestrians using LTE Signals

Abstract— The rapid growth of available services depending on location awareness has led to a more and more increasing demand for positioning in challenging environments. Global navigation satellite system (GNSS) based positioning methods may fail or show weak performance in indoor and urban scenarios due to blocking of the signals and multipath propagation. In contrast, cellular radio signals provide better reception in these scenarios due to a much higher transmit power. Also, they offer high cov- erage in most urban areas. However, they also undergo multipath propagation, which deteriorates the positioning performance. In addition, there are often only one or two base stations within communication range of the user. Both of these problems can be solved by means of a multipath-assisted positioning approach. The idea is to exploit multipath components (MPCs) arriving at the receiver via multiple paths due to scattering or reflections. Such approaches highly depend on the ability to resolve the MPCs at the receiver. This is why multipath-assisted positioning schemes typically assume ultra-wideband systems. Today’s cellular radio systems work with much smaller bandwidths, though. The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard uses bandwidths up to 20 MHz. The aim of this paper is to show by means of measurements that multipath- assisted positioning is possible using 3GPP-LTE signals with only two base stations. We apply an advanced signal processing algorithm to track MPCs arriving at the mobile terminal, and to estimate the position of the mobile terminal. Since each of the MPCs can be regarded as being sent from some physical or virtual transmitter, we estimate the positions of transmitters in addition. Assuming only the starting position and direction of the mobile terminal to be known, the results show that the root mean square positioning error of the mobile terminal is always below 1.8 meters. In 90% of the cases, it is below 1.25 meters.
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Doppler-aided positioning in GNSS receivers - A performance analysis

Doppler-aided positioning in GNSS receivers - A performance analysis

The main objective of Global Navigation Satellite Systems (GNSS) is to pre- cisely locate a receiver based on the reception of radio-frequency waveforms broadcasted by a set of satellites. Given delayed and Doppler shifted replicas of the known transmitted signals, the most widespread approach consists in a two-step algorithm. First, the delays and Doppler shifts from each satellite are estimated independently, and subsequently the user position and velocity are computed as the solution to a Weighted Least Squares (WLS) problem. This second step conventionally uses only delay measurements to determine the user position, although Doppler is also informative. The goal of this paper is to provide simple and meaningful expressions of the positioning precision. These expressions are analysed with respect to the standard WLS algorithms, exploit- ing the Doppler information or not. We can then evaluate the performance improvement brought by a joint frequency and delay positioning procedure. Numerical simulations assess that using Doppler information is indeed effective when considering long observation times and in challenging reception configu- rations such as urban canyons or near indoor situations, thus providing new insights for the design of robust and high-sensitivity receivers.
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Information content and testosterone dependence of animal signals

Information content and testosterone dependence of animal signals

mate choice. However, support for this assumption is rarely provided and alternative signalling functions are rarely considered. Indeed, in House Sparrows it is unlikely that variation in bill coloration is used in mate choice, given that during the breeding season there is virtually no variance in its expression (Laucht et al. 2010). Given its strong seasonal dependency and threshold relationship with T, it is more likely that bill colour signals something to do with different behavioural strategies (Dale 2006) associated with being in non-breeding versus breeding condition (such as aggression, Laucht et al. 2010). In Queleas, it is also unlikely that variance in bill coloration is particularly important during mate choice given that females also develop red bills only during the non-breeding season, when competition for limited food resources is very high. Even Zebra Finches and Red-legged Partridges have mating systems where sexual selection is not expected to be particularly strong: monogamy with long- term pair bonds. In Zebra Finches, demonstrating a strong mate choice for redder bills (let alone a benefit to females for having such preferences) has been notoriously difficult (Sullivan 1994; Balzer and Williams 1998; Forstmeier and Birkhead 2004) in comparison to other systems. In Red-legged Partridges, we are unaware of any research directed towards understanding the social contexts and decision making influences their carotenoid based ornaments are used for. Considering the current state of knowledge, we argue that it is just as likely that these ornaments signal aggression and dominance to competitive rivals as it is that they signal quality of the immune/anti-oxidation system to potential mates. Indeed, in Zebra Finches, Ardia et al. (2010) have recently demonstrated that a short term exposure to T produces a rapid change in bill colour and dominance. Moreover, the ornaments of Red-legged Partridges are deliberately displayed to rivals during aggressive interactions (Cramp and Simmons 1977-1994) suggesting a prominent role for them as signals used during competitive interactions.
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Market pricing of credit rating signals

Market pricing of credit rating signals

F-stat countries 0.00 0.00 0.00 Note: This table reports the coefficients corresponding to the equation 1, also including the country-specific dummies. Due to the specification of the rating scale, positive coefficients for β mean an increase (decrease) in spread following a downgrade (upgrade). The bottom row of the table report F-statistics for the significance of β-coefficients and country-specific dummies. The sample period is January 1999 to June 2011. The crisis period is defined as: August 2008 to Jun 2011, while the non-crisis period is defined as: January 2004 to December 2006. Countries with less than 20 observations are excluded.
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Estimation and cancellation of interferences in automotive radar signals

Estimation and cancellation of interferences in automotive radar signals

Investigations on the interference potential and effects between FMCW (frequency modulated continuous wave) radars showed that such interferences can severely decrease the detection capability of the sensors [1, 2]. The most common interference scenario is an intersection of the frequency ramps transmitted by different sensors [3]. Such interference increases the receiver’s noise floor and can lead to a sensor blindness. Especially targets with a low radar cross section, like pedestrians, cannot be detected reliably anymore due to this effect.

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Bayesian inference of early-universe signals

Bayesian inference of early-universe signals

Bibliography 103 [56] K. N. Abazajian, K. Arnold, J. Austermann, B. A. Benson, C. Bischoff, J. Bock, J. R. Bond, J. Borrill, I. Buder, D. L. Burke, E. Calabrese, J. E. Carlstrom, C. S. Carvalho, C. L. Chang, H. C. Chiang, S. Church, A. Cooray, T. M. Crawford, B. P. Crill, K. S. Dawson, S. Das, M. J. Devlin, M. Dobbs, S. Dodelson, O. Doré, J. Dunkley, J. L. Feng, A. Fraisse, J. Gallicchio, S. B. Giddings, D. Green, N. W. Halverson, S. Hanany, D. Hanson, S. R. Hildebrandt, A. Hincks, R. Hlozek, G. Holder, W. L. Holzapfel, K. Honscheid, G. Horowitz, W. Hu, J. Hubmayr, K. Irwin, M. Jackson, W. C. Jones, R. Kallosh, M. Kamionkowski, B. Keating, R. Keisler, W. Kinney, L. Knox, E. Komatsu, J. Kovac, C.-L. Kuo, A. Kusaka, C. Lawrence, A. T. Lee, E. Leitch, A. Linde, E. Linder, P. Lubin, J. Maldacena, E. Martinec, J. McMahon, A. Miller, L. Newburgh, M. D. Niemack, H. Nguyen, H. T. Nguyen, L. Page, C. Pryke, C. L. Reichardt, J. E. Ruhl, N. Sehgal, U. Seljak, L. Senatore, J. Sievers, E. Silverstein, A. Slosar, K. M. Smith, D. Spergel, S. T. Staggs, A. Stark, R. Stompor, A. G. Vieregg, G. Wang, S. Watson, E. J. Wollack, W. L. K. Wu, K. W. Yoon, O. Zahn, and M. Zaldarriaga, ArXiv e-prints (2013), arXiv:1309.5381 [astro-ph.CO] .
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War signals: A theory of trade, trust and conflict

War signals: A theory of trade, trust and conflict

the one hand, and beliefs and norms of cooperation in the labor market, on the other hand. 10 This paper is also related more generally to the economic literature studying con‡ict. Some existing theories focus on institutional failures, such as weak state capacity and weak institutions (Besley and Persson, 2010, 2011; Fearon, 2005). In Besley and Persson (2011) the lack of checks and balances implies that rent-sharing strongly depends on who is in power, thereby strengthening incentives to …ght. 11 Poverty and natural resource abundance have also been found to fuel con‡ict, as the former reduces the opportunity cost of …ghting, while the latter results in a larger "pie" that can be appropriated (cf. Torvik, 2002, and Collier and Hoe- er, 2004). Esteban and Ray (2008) emphasize the role of ethnic diversity, and argue that ethnic polarization can favor the collective action needed for appropriation by generating the right mix of capital and labor for the groups. In Rohner (2011) ethnic diversity increases the risk of con‡ict by reducing the reputational cost of non-cooperative behavior. While explaining why some countries are more prone to con‡icts than others, most of such theories do not explain why a civil war today makes future con‡ict more likely. An exception is Acemoglu, Ticchi and Vindigni (2010) who argue that in weakly-institutionalized states civilian governments have incentives to select small and weak armies to prevent coups. This has the undesired consequence of making it harder for the state to end insurgency and rebellion. Collier and Hoe- er (2004) argue that current con‡ict makes con‡ict recurrence more likely due to the existence of con‡ict-speci…c capital, like cheap military equipment.
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Skills, Signals, and Employability: An Experimental Investigation

Skills, Signals, and Employability: An Experimental Investigation

There is also abundant evidence highlighting the importance of non-cognitive skills. While non-cognitive skills are often used as a vague term for any skill that is not cognitive (and, in fact, many skills generally referred to as non-cognitive contain a strong cognitive component), an increasing literature investigates different empirically clearly specified skills in the non-cognitive domain. One important dimension of non-cognitive skills is social skills. Deming (2017) argues that the importance of social skills on the labor market is growing, with the fastest-growing occupations requiring a substantial amount of interpersonal interactions. His results support a model of team production where workers trade tasks to exploit their comparative advantage. In this setting, social skills reduce coordination costs, allowing workers to specialize and trade more efficiently. Thus, social skills such as the willingness to cooperate may make workers more productive in team production. 10 This may be particularly important in occupations with a high complementarity between cognitive and social skills (Weinberger 2014). Recent evidence suggests that social volunteering may be used to credibly signal willingness to cooperate (Baert and Vujić 2016; Heinz and Schumacher 2017), but social volunteering may also be correlated with other skills valued by employers.
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Skills, Signals, and Employability: An Experimental Investigation

Skills, Signals, and Employability: An Experimental Investigation

firms (indicated in the column headers) for the secondary-school-graduate and the college-graduate sample, respectively. Each cell stems from a separate regression. For apprenticeship positions, we find substantial effect heterogeneity with respect to HR manager characteristics (Table 6). Older HR managers (median split at age 51) put less weight on school grades, but more weight on IT skills. Older managers also appreciate social volunteering more, but consider team sports to be less important for the decision whom to invite for a job interview. These differences between young and old HR managers might indicate that older HR managers experienced that school grades predict the workplace performance of apprentices less well than signals of specific abilities such as IT skills. Similarly, experienced HR managers might have experienced that social volunteering is indeed a good signal for social skills that are important on the labor market. Interestingly, the focus of HR managers who are also the managing directors of their firm goes in the same direction as that of older HR managers, partly reflecting that the majority of managing directors (59.5 percent) are also in the subgroup of older HR managers. Furthermore, managing directors also place more weight on work experience through long internships than HR managers who are not managing directors. The latter is also true for HR managers who are responsible for hiring decisions in their firm.
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Assortative matching through signals

Assortative matching through signals

6 Equilibrium properties 6.1 Efficiency The separating equilibrium we have identified is efficient in a number of important re- spects. First and foremost, search costs are minimised, both for each agent individually and overall: in equilibrium, truthful signals allow each agent to ensure that no meeting is wasted, but that every meeting she attends results in a match. Hence, whenever an agent searches, she matches after an expected search time of 1/η. This is the minimum delay because a meeting necessarily precedes a match. In a random search model, each match would typically be preceded by a number of unsuccessful meetings, and only by chance will the first meeting of an agent result in a match. Therefore, search costs in random search models are at least as high from the individual perspective as in our model with truthful signals, and strictly higher in expectation as well as on aggregate. Second, note that all agents match in equilibrium so that there is no unrealised surplus left in the form of agents who never match. On the contrary, Becker (1973) proved the following result:
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Skills, Signals, and Employability: An Experimental Investigation

Skills, Signals, and Employability: An Experimental Investigation

self-reported hiring priorities of HR managers tend to be in line with their decisions between the fictitious resumes in the choice experiments. Overall, our results indicate that a broad range of skill signals does indeed causally affect employment chances at labor-market entry. Employers appear to value skill signals in several different domains. While situated in a specifically designed experimental setting, the results add an important dimension to our understanding of how labor markets process and use information on skills. When observational data indicate that, for example, high-school grades are associated with labor-market outcomes, it remains unclear whether employers really value grades or whether the association captures other productivity aspects that happen to be correlated with grades, whereas grades are potentially never conscientiously observed by employers. Even in the setting of a convincing natural experiment, it is hard to imagine a research design that can separately identify independent exogenous variation in different skill dimensions such as GPAs and other skill signals such as social engagement. Our experimental results indicate that employers do indeed care about signals such as high-school GPAs, social volunteering, and internships, adding to the scientific knowledge on the importance of skills and signals for labor-market outcomes. The results also provide an indication about which signals may be particularly relevant for whom. The observed effect heterogeneities by stage of application (school vs. college graduates), gender of applicants, and traits of HR decision-makers suggest that different signals are regarded as relevant, expected, and credible in different situations.
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L band solar radio bursts on September 6, 2017 and its impact on GNSS signals

L band solar radio bursts on September 6, 2017 and its impact on GNSS signals

Strong solar radio bursts are known to cause radio interference and have the potential to affect satellite radio systems such as Global Navigation Satellite System (GNSS).. On September[r]

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Joint Bayesian Positioning and Multipath Mitigation in GNSS

Joint Bayesian Positioning and Multipath Mitigation in GNSS

To demonstrate the capabilities of the proposed estimator sim- ulations were carried out. The employed navigation signal is a BPSK modulated GPS C/A code signal having a two- sided bandwidth of 20 MHz. In the simulations it is assumed that four satellites are received with a C/N 0 of 50 dB-Hz re-

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Cheap Talk with Correlated Signals

Cheap Talk with Correlated Signals

Formally, we assume that the distribution of preferences is associated with the dis- tribution of signal correlations according to the linear function b(k) = B − ak, where both B, a > 0. The slope a measures how much additional distance in preferences is needed to generate sensitive given decrease in correlation. We interpret this parameter as an index of polarization of society: a large a indicates that very distant preferences do not imply a very different correlation of information. This would be the case if, for instance, all agents acquired information from similar sources, regardless of their preferences — a case of weak polarization. The position of the line b(k), given by the intercept B, measures the general level of correlation of information: a parallel shift to the right captures an increase of correlation for each possible distance in preferences. We interpret B as an index of correlation in the information disclosed by primary sources (e.g., newspapers) to the senders.
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Cheap Talk with Correlated Signals

Cheap Talk with Correlated Signals

The quality of information is usually measured by its accuracy. However, when different pieces of information come from multiple sources, correlation also affects their informative content in an intuitive way. In the limit case of perfect correlation, observing one single piece of information is equivalent to observing any number of pieces, and communication becomes worthless. Correlation is, indeed, a common feature of many problems where the strategic transmission of information is a relevant issue: a legislative commission audits several experts on a given matter and the experts have partially coincident information sources; a perspective voter wants to form an opinion and joins an online political discussion group whose members lean towards the same party and form their opinions sourcing from similar media; witnesses in a cross-examination may have information that overlaps to different extents; etc. In general, correlation of private information may be caused either by external factors (e.g. a small number of information sources is available) or by preferences (e.g. people with similar views and preferences may source from similar sources and have similar acquaintances).
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Neural signals encoding shifts in beliefs

Neural signals encoding shifts in beliefs

Dopamine is implicated in a diverse range of cognitive functions including cognitive flexibility, task switching, signalling novel or unexpected stimuli as well as advance information. There is also longstanding line of thought that links dopamine with belief formation and, crucially, aberrant belief formation in psychosis. Integrating these strands of evidence would suggest that dopamine plays a central role in belief updating and more specifically in encoding of meaningful information content in observations. The precise nature of this relationship has remained unclear. To directly address this question we developed a paradigm that allowed us to decompose two distinct types of information content, information-theoretic surprise that reflects the unexpectedness of an observation, and epistemic value that induces shifts in beliefs or, more formally, Bayesian surprise. Using functional magnetic- resonance imaging in humans we show that dopamine-rich midbrain regions encode shifts in beliefs whereas surprise is encoded in prefrontal regions, including the pre-supplementary motor area and dorsal cingulate cor- tex. By linking putative dopaminergic activity to belief updating these data provide a link to false belief formation that characterises hyperdopaminergic states associated with idiopathic and drug induced psychosis.
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Parametric Amplification and Wavelength Conversion of Phase-Modulated Signals

Parametric Amplification and Wavelength Conversion of Phase-Modulated Signals

modulation index first increases at low pump powers, then reaches a distinct maximum and falls off after. At low pump powers, the SOA is not saturated and the idler phase distortion increases because the XPM efficiency is proportional to the pump power. At high powers, the idler phase distortion decreases because the SOA is strongly satu- rated so that the gain and therefore the XPM efficiency is decreasing. For higher signal powers, the phase distortion decreases because the signal also contributes to the SOA saturation. Fig. 5.14b shows the same data but keeping the signal-to-pump power ratio (SPR) constant instead of the signal power. In this case, the idler phase distortion decreases monotonically with increasing pump power due to the SOA saturation. The relative contribution of the signal to the SOA satura- tion is constant due to the constant SPR. For lower SPR values, the sig- nal contributes stronger to the SOA saturation leading to a decreased XPM efficiency. The transfer function of the process is shown in Fig. 5.15. The used parameters were L = 1 mm, I B = 190 mA, P p = 12.8 dBm, P s = 2.8 dBm and ∆ λ = −2.5 nm. λ p was set to the ASE spectral peak. Due to the limited time constant of the CDP gain contribution, the XPM efficiency falls off quickly beyond 10 GHz. This bandwidth is similar to that of the CDP contribution to the FWM conversion ef- ficiency schematically depicted in Fig. 5.4b (as well as similar to the XGM bandwidth of the SOA). The simulated values were fitted by the third-order low-pass filter function given by
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