Research on pulse response characteristics of wireless ultraviolet communication in mobile scene

Peng Song; Chun Liu; Taifei Zhao; Hua Guo; Jinni Chen

doi:10.1364/OE.27.010670

1. Introduction

Non-line-of-sight (NLOS) ultraviolet (UV) communication (UVC) is a new type of wireless optical communication mode, which transmits information by the scattering of UV in the atmosphere in the 200–280-nm “solar blind” band [1]. Compared with conventional communication methods, the UVC has many advantages, such as good security, strong anti-interference ability, omnidirectional ability, and NLOS communication. The UVC can be used in close-range covert communication [2,3], enabling wireless UVC to be a good application prospect in the military field.

The establishment of a suitable model is the basis for studying wireless UVC. In 1979, Reilly and Warde [4] were the first to introduce a classical single scattering transmission model based on the ellipsoidal coordinate system. Then, based on their study, a common volume was integrated in different areas of study, and the single-scatter communication coplanar model of UVC was established [5]. Xiao et al. [6] proposed the NLOS channel model in atmospheric random turbulence. Based on the Monte-Carlo (MC) method, Song et al. [7] presented a multiple-scatter propagation model for noncoplanar UVC with a height difference between the transmitter (Tx) and receiver (Rx).

With the establishment of a series of UVC channel models, several studies were conducted on the characteristics of a wireless UVC channel. Chen et al. [8] and He et al. [9] presented an empirical path loss model for UV coplanar single-scattering and introduced some parameters of the empirical path loss formula. The signal-to-noise ratio (SNR) formula of a UVC system was presented in [10], and an SNR-estimation method for NLOS UVC was presented in [11] to estimate the channel capacity. An approximate closed-form solution of path loss for a noncoplanar UV single-scatter system with a small beam angle or FOV angle was proposed in [12]. Jiang et al. [13] studied the influence of multiuser interference on the communication performance of a NLOS UVC system based on the MC method. In the same year, Dong et al. [14] studied the influence of transmission geometry and communication distance on UVC based on the NLOS single-scatter model of UV rays. In [15], based on the spherical coordinate system and theory of UV single-scatter, a method for calculating path loss of a noncoplanar UVC system was proposed using the Riemann sum method (RSM). El-Shimy and Hranilovic [16] presented a statistical inter-symbol interference (ISI) channel model for NLOS UV channels including the stochastic effects of propagation and detection.

In the study of channel characteristics, it is important to study the pulse broadening effect in UVC to reduce ISI and improve system transmission rate. The experimental platform of NLOS UVC was first built by Chen et al. [17]; they studied the relationship between the pulse response signal and geometric parameters of the transceiver and concluded that pulse broadening has little relationship with the beam angle. Ding et al. [18] used the gamma function to simulate the channel pulse response and obtained the bandwidth formula. Luo [19] studied the influence of the geometrical parameters of a transceiver and the receiving distance on channel attenuation and pulse response. The influence of the receiver’s geometric parameters on the pulse width of the single-scatter channel was analyzed in [20]. The influences of UV scattering on the time-domain broadening of a pulse signal and cross talk between pulse-signal sequences on the communication rate were studied in [21]. The path loss and pulse response of long-distance NLOS UVC were studied with experimental data and the MC theoretical model in [22].

At present, research have considered fixed wireless UVC nodes, for example, based on the MC method, the multiple scattering transmission model of the NLOS UVC in the noncoplanar communication system was established in [23]. The study concluded that the full width at half-maximum (FWHM) of the pulse response of such an NLOS UVC will increase with the increasing elevation angles of the transmitter and receiver and deflection angle of the receiver. However, in practical applications, most of the communication nodes are mobile, so it is meaningful to study the pulse-broadening characteristics in the case of mobile.

The remainder of this paper is organized as follows. Section 2 explains the research idea, presents the model for NLOS UV single-scatter, and gives a detailed description of the RSM. Then, the validity of the RSM in the pulse response of a wireless UVC is proved through a validation experiment. In Section 3, the influence of the geometric parameters of the transceiver on the pulse response width is simulated and analyzed. Finally, we draw our conclusions in Section 4.

2. Research on pulse response in mobile scene based on RSM

2.1 Research method of pulse broadening in moving scenes

In general, to study the pulse broadening of wireless UVC system in mobile scenes and the relative positional relationship between two nodes, a moving scene must be transformed into a fixed scene of the communication node. Next, the pulse-broadening characteristics of the fixed scene of the node are studied. Finally, the fixed scenes are strung together to reflect the variation in the pulse-broadening characteristics of the system under the moving scene.

As shown in Fig. 1, the receiver was fixed at (100, 0, 0) and the transmitter moved in eight directions centered at the origin. When the transmitter moves, there are two kinds of situations, coplanar and noncoplanar. Except the coplanar cases in the 0° direction and the 180° direction, all the rest are all non-coplanar cases. It is noteworthy that the coordinate system here is parallel to the ground. First, the geometric parameters of the transceiver were fixed, and the moving distance of the transmitter in the eight directions was adjusted, that is, the relative position between the two nodes was adjusted. The relationship between the pulse response of the system and the relative position change between the two nodes was studied using the RSM. Then, the geometric parameters of the transceiver were changed, and the influence of these parameters on the relationship between the pulse response of the system and relative position change between the two nodes was further studied.

Fig. 1 Schematic of the research on the pulse response of the wireless UVC system in a mobile scene.

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2.2 UV noncoplanar single-scatter transmission model based on RSM

The calculation of the received energy and path loss by using the conventional UV NLOS noncoplanar single-scatter model based on ellipsoidal or spherical coordinates is difficult because the upper and lower limits of the triple integral operation of the scattering common volume and integrand function are very complicated [24,25]. The RSM can quickly calculate the path loss of the noncoplanar UVC system and is suitable for arbitrarily pointing at the transmitter and receiver, thus decomposing complex operations into simple arithmetic sums and facilitating in the application of embedded UVC systems. Figure 2 depicts the NLOS UV single-scatter propagation model in noncoplanar geometry, where C_t and C_r denote the Tx beam and Rx field-of-view (FOV) cones, respectively. T and R are the center points of the transmitter and receiver, respectively; TE is the central axis of the emission cone; and TE′ is the projection of TE on the x–y plane. ∠ETE′ is the elevation angle of C_t, recorded as θ_t. In addition, C_t has a half beam angle $ϕ_{t}$ at point T, and α_t is the Tx off-axis angle, which is equal to the angle between TE′ and the positive x-axis. RF is the central axis of the receiving cone, and RF′ is the projection of RF on the x–y plane. ∠FRF′ is the elevation angle of the C_r, recorded as θ_t. Further, C_r has half FOV angle $ϕ_{r}$ at point R, and α_r is the Rx off-axis angle, which is equal to the angle between RF′ and the positive x-axis. The baseline distance between Tx and Rx is d. The elevation and off-axis angles of the transmitter and receiver will determine the orientation of the transmitter and receiver FOV cones, respectively.

Fig. 2 NLOS UV single-scatter propagation model in noncoplanar geometry.

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Common volume V is defined as the common part of the Tx and Rx, as shown by the blue thick coil range in Fig. 2. Scattering point S is chosen in common volume V, and the photons emitted from the transmitter are scattered by S to the receiver. The coordinates of S in the spherical coordinate system can be expressed by apex angle θ, azimuth angle α, and radial distance r. That is, the coordinates of S can be uniquely determined by (θ, α, r). The ranges of θ and α are the same for coplanar and noncoplanar cases in UVC. However, for r, the range of r value is the largest in coplanar case. Therefore, in order to include common volume in both coplanar and non-coplanar cases, the range of r value is set to coplanar case. Scattering angle β_s is defined as the angle between the forward direction of incident ray and its scattered direction toward the Rx. ζ is the angle between the line connecting scattering point S with the center of the detector and the central axis of C_r; r₁ is the distance from S to R.

The basic idea of an RSM is to divide a closed free space containing a common volume into a number of tiny units in a spherical coordinate system, and then perform triple integration on each tiny unit in the common volume. That is, the energy of the UV emitted from the transmitter through the tiny unit to reach the receiver is determined. Finally, all the tiny units are traversed, and all the energy is accumulated to obtain the total energy that reaches the receiver through a single scattering of the common volume.

According to the basic idea of the RSM and Fig. 2, the NLOS coplanar UV single-scatter propagation model including common volume V is shown in Fig. 3. In Fig. 3, the border ranges of ALCE and AOCG thick coil enclosed regions V ́ and V, respectively. Closed region V ́ is divided into a large number of tiny units V”, where “+” denotes the center of V”. TP and RQ are the central axes of the transmitter and receiver FOV cones, respectively, and P ́ and Q ́ are the projections of the P and Q points on the x–y plane, respectively.

Fig. 3 NLOS UV single-scatter propagation model in coplanar geometry.

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Closed region V ́ is divided into M³ tiny units, V”. According to the relationship between the RSM error and number of divisions, as stated in [15], number of segmentations M was selected as 60 in this study. When the center point of the division is situated in V, the energy scattered by tiny unit V” can be received by the receiver, and this energy can be expressed as follows [15]. For example, consider, tiny unit V” with S as the center point, Then,

\begin{matrix} E_{V^{"}}_{r} = \int_{r_{B}}^{r_{C}} \int_{α_{D}}^{α_{B}} \int_{θ_{A}}^{θ_{B}} \sin θ e^{- k_{e} (r + r_{1})} δ θ δ α δ r \cdot \frac{E_{t} A_{r} k_{s} P (\cos β_{s}) \cos ζ}{4 π_{} Ω_{t} r_{1}^{2}} \\ = \frac{E_{t} A_{r} k_{s} P (\cos β_{s}) \cos ζ}{4 π_{} Ω_{t} r_{1}^{2} k_{e} e^{k_{e} (r_{1} + r_{B} + r_{C})}} (\cos θ_{B} - \cos θ_{A}) \cdot (α_{B} - α_{D}) (e^{k_{e} r_{B}} - e^{k_{e} r_{C}}), \end{matrix}

where ζ = ∠SRF,

r_{1} = | \vec{SR} |

, E_t is the energy emitted by the transmitter, A_r is the Rx detection area, and k_s is the atmospheric scattering coefficient, which is equal to the sum of the Rayleigh and Mie scattering coefficients, i.e.,

k_{s} = k_{s}^{R} + k_{s}^{M}

. Further, k_e is the atmospheric extinction coefficient, which is equal to the sum of the atmospheric absorption and scattering coefficients, that is,

k_{e} = k_{s} + k_{a}

. P(cosβ_s) is the scattering phase function and Ω_t is the solid angle of the Tx,

Ω_{t} = 2π (1 - \cos ϕ_{t})

. In Fig. 2, θ_A and θ_B are the apex angles of A and B, respectively, α_B and α_D are the azimuth angles of B and D, respectively, and r_B and r_C are the radial distances of B and C, respectively.

As tiny unit V” is very small, the scattering angle of its internal scattering point can be approximated by the scattering angle of its central scattering point S, and can be calculated as follows:

β_{s} = π - ∠ TSR = \cos^{- 1} (\frac{\vec{TS} \cdot \vec{SR}}{| \vec{T S} | \cdot | \vec{S R} |}),

where

\vec{S R} = [d - x_{s}, - y_{s}, - z_{s}]

.

The total energy scattered from common volume V and received by the Rx can be calculated by

E_{r} = \sum_{S_{(i, j, k)} \in V} E_{V_{(i, j, k)}^{"} r},

where

E_{V_{(i, j, k)}^{"} r}

can be obtained from Eq. (1).

By taking time point t_n as the center, a time interval with a width of △t was defined as [t_n_min, t_n_max], where t_n_min = t_n − △t and t_n_max = t_n + △t. The time at which the photons travel from the transmitter to the receiver is calculated as t_s = (r + r₁)/c, where c is the speed of light, r is the distance from the emitter to scattering point S, and r₁ is the distance from S to the receiver. If t_n_min < t_s < t_n_max, t_n can be approximated as the time taken for the photon to reach the receiver by scattering from the emitter through V”. According to the RSM, the value of temporal response h(t_n) at time t_n can be calculated as

h (t_{n}) = \sum_{(S_{(i, j, k)} \in V) \cap (t_{n \min} < t_{s} < t_{n \max})} \frac{E_{V^{''}_{{(i, j, k)}^{r}}}}{Δ t},

where

(S_{(i, j, k)} \in V)

implies that V” of all centers in common volume V can be traversed, and

E_{V_{(i, j, k)}^{"} r}

can be obtained through Eq. (1).

2.3 Experimental validation

To verify the validity and reliability of the RSM in simulating a wireless UVC process, the experimental results were compared with the simulation results. The experiment was conducted in the playground of Xi'an Polytechnic University in Shaanxi Province from 8 p.m. to 11 p.m. on January 11, 2017. The temperature, relative humidity, visibility, and pressure were 3°, 48%, 15 km, and 1027 hPa respectively. The UV light-emitting diode (LED) with a central wavelength of 255 nm at the emitter end and a Hamamatsu photomultiplier tube (PMT) R7154 at the receiver end was used. The geometric parameters of the transceiver are $θ_{t} = θ_{r} = 10^{\circ}$ , $ϕ_{t} = 3^{\circ}$ , and $ϕ_{r} = 40^{\circ}$ .The distance between the transmitter and receiver is 10 m. The pulse signal at the transmitter had a loading frequency of 10 kHz and duty cycle of 10%.

The waveforms of the experimental receiver and simulation result are shown in Figs. 4(a) and 4(b), respectively. The simulation and experimental parameters were the same. The comparison of the two subgraphs of Fig. 4 shows that the FWHM of the received pulse response is almost the same. The slight difference could be because of the presence of many factors (such as characteristics of experimental equipment and changes in the external environment) that affect the communication quality in the actual experiment, while the environment in the simulation is more ideal. As shown, the RSM is available in the wireless UVC.

Fig. 4 Contrast diagrams of experiments and simulations. (a) Experimental result, (b) Simulation result

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3. Simulation analysis

This section shows the pulse-broadening phenomenon of a single-scatter of the UVC system based on the RSM. In addition, we studied the relationship between the pulse broadening and moving position when the geometric parameters of the transmitter and receiver are fixed. Based on the results, we simulated and analyzed the effects of the elevation angle, beam angle, FOV angle, and transmitter position on the pulse broadening. The transmitter transmits a single-pulse signal with energy of 1 J, with a starting time of 0 and pulse width of 3 ns. The remaining simulation parameters are listed in Table 1.

Table 1. Simulation parameters.

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3.1 Influence of relative position change of nodes on pulse broadening when the geometric parameters of the transceiver are fixed

First, the geometric parameters of the transceiver were fixed (the detailed data are listed in Table 2). Then, the transmitter was moved in eight directions from its origin, and the pulse response at the different positions was obtained, thereby obtaining the FWHM of the received pulse response (pulse widths in this article are FWHM values); the trend graph is shown in Fig. 5.

Table 2. Geometric parameters of the transceiver.

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Fig. 5 Influence of node’s position change on pulse broadening.

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As shown in Fig. 5, the pulse-broadening phenomenon occurs when the transmitter moves in the eight directions, indicating that the pulse broadening really exists in the UVC system when a node moves; this proves a necessity for further study. In the 0° direction, the pulse width decreases with increasing distance between the transmitter and origin. This is because in the 0° direction, with the increasing distance between the transmitter and origin, distance d between the transmitter and receiver decreases gradually, and the volume of the common scatter decreases; therefore, the pulse width decreases. In the other directions, the results are the opposite of that in the 0° direction. Moreover, no pulse response was recorded after 60 m in the 45° and 315° directions, and there is no common volume after 72.98 m, that is, the receiver does not receive the pulse signal. The specific calculation process is as follows (with 45° as an example). Similar problems in subsequent simulations are not explained.

As shown in Fig. 6(b), the distance from the intersection of the projection of the Rx cone at the x–y plane to the origin of the 45° line, that is, the length of TA, must be calculated. First, the degree of θ in Fig. 6(a) corresponding to θ in Fig. 6(b) was calculated according to Eq. (5). Then, the length of TA was calculated as 72.98 m according to the trigonometric function. The calculation results verify the correctness of the simulation results.

Fig. 6 Schematic of (a) receiver cone and (b) x–y-plane projection.

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\begin{array}{l} y = x t g 20^{\circ} \\ z = x t g 50^{\circ} \\ a = \sqrt{z^{2} - y^{2}}, \\ b = \sqrt{x^{2} + y^{2}} \\ t g θ = \frac{a}{b} \end{array}

According to Fig. 5, we can also find that among the eight directions, the 45° direction curve is consistent with the 315° direction curve, the 90° direction curve is consistent with the 270° direction curve, and the 135° direction curve is consistent with the 225° direction curve. This implies that with the x-axis as the axis of symmetry, the upper and lower corresponding trends are the same. Based on this result, the next study will investigate only the influence of the geometric parameters of the transceiver on the pulse response in the five directions above the x-axis (including the x-axis).

3.2 Effect of the change of the elevation angle of the transceiver on the pulse broadening in the moving scene

We verified that a pulse broadening phenomenon is indeed witnessed in the case of motion. This section mainly discusses the simulation of the influence of the elevation angle of the transmitter and receiver on the pulse response. The simulation parameters were taken as $ϕ_{t} = 10^{\circ}$ , $ϕ_{r} = 50^{\circ}$ , and α_t = α_r = 0°.

Figure 7 displays a graph showing changes in pulse width in five directions when the elevation angles of the transmitter were changed to 20°, 40°, 60°, and 80° at θ_r = 20°. As shown, with the increasing distance between the transmitter and origin in the five directions, the pulse broadening shows an increasing trend except in 0° and 45°directions. Figure 7 show that when θ_r is fixed and θ_t increases, the width of the pulse response increases. In Fig. 7(c), by considering the transmitter at the origin as an example, θ_t was increased from 20° to 80°, and the pulse response width was increased from 13.3 to 200 ns, which shows an increase by 14 times. In Fig. 7(e), for example, the distance between the transmitter and origin is 100 m, θ_t increases from 20° to 80°, and the pulse response width increases from 22.2 to 366.7 ns, which shows an increase by 15.5 times.

Fig. 7 Effect of elevation angle change at the transmitter on pulse broadening. (a)0° path, (b) 45° path, (c) 90° path, (d) 135° path, (e) 180° path

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In the case of θ_t = 20°, the relationship between the pulse response width and the distance from the transmitter to origin is shown in Fig. 8. We can see that Fig. 8 has the same trend as Fig. 7. When θ_t is fixed, θ_r increases and the pulse response width increases. In Fig. 8(c), for example, when the transmitter is at the origin, θ_r increases from 20° to 80°, and the pulse response width increases from 13.3 to 66.7 ns, which shows an increase by four times. In Fig. 8(e), when the distance between the transmitter and origin is 100 m, θ_r increases from 20° to 80°, and the pulse response width increases from 22.2 to 133.3 ns, which shows an increase by five times. The comparisons between Figs. 7(c) and 8(c) as well as Figs. 7(e) and 8(e) show that the change in the transmitter elevation angle has a greater influence on the pulse response broadening than that in the receiver elevation angle.

Fig. 8 Effect of elevation angle change at the receiver on pulse broadening. (a)0° path, (b) 45° path, (c) 90° path, (d) 135° path, (e) 180° path

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According to the simulation result shown in Fig. 9, the pulse width also increases as the elevation angle of the transceiver increases. The larger the elevation angle of the transceiver, the more the slope of the pulse width increases. Figure 9(d) shows that when the transmitter is at the origin, the elevation angle of the transceiver increases from 20° to 80° and the pulse response width increases from 13.3 to 555.6 ns, showing an increase by 40.7 times. When the transmitter is 100 m away from the origin, the pulse response width increases from 26.9 to 923.1 ns, showing an increase by 33 times. This implies that for larger elevation angles of the transceiver, the pulse broadening phenomenon is severe, thus resulting in a low communication rate.

Fig. 9 Effect of the same change in the elevation angle of the transceiver on the pulse broadening. (a)0° path, (b) 45° path, (c) 90° path, (d) 135° path, (e) 180° path

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The effects of elevation angle change on pulse broadening in a mobile scene (Fig. 7) are summarized in Table 3. According to Fig. 7 and Table 3, it can be found that except 0° and 45° directions, the others directions showed an upward trend. The trend of pulse broadening is affected by both d and V. In 0° direction, d and V decrease, the pulse broadening decreases consequently. In 180° direction, d and V increase, therefore the pulse broadening increases. In 90° and 135° directions, V decreases and d increases, meanwhile d plays a major role and causes the pulse broadening to increase. In Fig. 7(b), the pulse broadening tends to decrease overall when θ_t = 80°, because the elevation angle of the transmitter is large, and when the transmitter moves in the direction of 45°, V decreases rapidly, thus the pulse broadening decreases. Figures 8 and 9 show similar reasons for curve changes.

Table 3. Summary of pulse broadening trend when the elevation angle of the transmitter changes.

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3.3 Effect of FOV angle variation on pulse width

In the aforementioned text, we studied the effect of the elevation angles of the transmitter and receiver on the pulse response width in the moving scene. Next, we analyze the effect of the FOV angle on the pulse response width. The simulation parameters were taken as θ_t = θ_r = 20°, α_t = α_r = 0°, and $ϕ_{t} = 10^{\circ}$ .

The five subgraphs of Fig. 10 show that when the other parameters are fixed, the angle of FOV increases from 20° to 50°, which has little effect on the pulse width, and the three curves are intertwined. This is because after the FOV angle increases from 30°, all the additional photons are photons at the end of the Tx cone, and their probability of reaching the receiver is small, and thus their survival rate is low; therefore, the change in FOV angle has little effect on the pulse response width. In addition, in all directions, the relationship between the pulse width and distance from the transmitter to origin is the same as that in Fig. 5.

Fig. 10 Effect of FOV angle variation on pulse width. (a)0° path, (b) 45° path, (c) 90° path, (d) 135° path, (e) 180° path

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3.4 Influence of beam angle on pulse response width

Here, we simulated the effect of the variation of the beam angle on the pulse response width. At this point, the remaining geometric parameters were fixed at θ_t = θ_r = 20°, α_t = α_r = 0°, and $ϕ_{r} = 50^{\circ}$ . The simulation results are shown in Fig. 11, according to which when the FOV angle is fixed at 50°, the beam angle increases from 5° to 10° and then to 15°, and the pulse response width shows little change. In the 135° direction [Fig. 11(d)], when the transmitter is at the origin, the pulse width changes from 15, to 14, and to 11 ns at beam angles of 5°, 10°, and 15°, respectively. Figure 11(b) shown that in the direction of 45°, the pulse width corresponds to 6.7, 6.2, and 5 ns at beam angles of 5°, 10°, and 15°, respectively, when the distance between transmitter and origin is 70 m.

Fig. 11 Influence of beam angle on impulse response width. (a)0° path, (b) 45° path, (c) 90° path, (d) 135° path, (e) 180° path

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The simulation results of the five moving paths show that the pulse width first increases and then decreases in the 90° direction, with an upward trend from 0 to 70 m and a downward trend from 70 to 100 m. This is because the pulse response is affected by two factors when the transmitter is moving at 90°. Factor 1 is that as the distance between the transmitter and receiver increases, the pulse response width increases along with the time delay of the photon reaching the receiver. Factor 2 is the size of the common volume. When the transmitter moves in the 90° direction and the FOV angle is fixed, the V decreases gradually, which leads to the pulse response width decreases. During the movement, two factors affect the pulse width, as stated earlier. From 0 to 70 m, factor 1 plays a leading role; however, when the emitter moves to a relatively distant position, the influence of factor 1 weakens at 70 m, and factor 2 plays a major role in the range of 70 to 100 m. Based on the above-mentioned analysis, the reason for the curve to first ascend and then descend in the 90° direction is explained. As shown in Figs. 11(a)–11(c), the 45° direction is a transition phase from the 0° to 90°.

4. Conclusions

In this study, RSM was mainly used as the theoretical basis, along with the NLOS UV single-scatter model to study the influence of the change in the geometric parameters of the transceiver on the pulse response width under moving conditions. The following conclusion can be drawn from the simulation results.

(1) The pulse broadening phenomenon does exist under moving conditions, and the pulse response width increases in all directions except the 0° direction.
(2) For fixed FOV, off-axis, and beam angles, pulse broadening will occur with increasing elevation angles of the transmitter and receiver, and the effect of the elevation angle of the transmitter on the pulse response width is greater than that of the receiver.
(3) When the FOV angle increases to more than 30°, it has less influence on the pulse response width.
(4) When the FOV angle is 50°, the variation in the beam angle has no obvious influence on the pulse response.

Funding

National Natural Science Foundation of China-Joint Research Funding of Civil Aviation Administration (U1433110), and Natural Science Foundation of Shaanxi Province Department of Education (17JK0319).

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Parameter	Value
Wavelength $λ$	266 nm
Rayleigh scattering coefficients $k_{s}^{R}$	$0.24 \times 10^{- 3}$ m⁻¹
Mie scattering coefficients $k_{s}^{M}$	$0.25 \times 10^{- 3}$ m⁻¹
Absorption coefficients $k_{a}$	$0.74 \times 10^{- 3}$ m⁻¹
Receiving aperture radius $r$	$0.4 \times 10^{- 2}$ m
Rayleigh phase function scattering parameter $γ$	0.017
Mie phase function asymmetry parameter $g$	0.72
Mie phase function parameter $f$	0.5
Division times $M$	60
Speed of light $c$	$3 \times 10^{8}$ m/s

Parameter	Value
Tx elevation angle $θ_{t}$	$20^{\circ}$
Half-beam angle $ϕ_{t}$	$10^{\circ}$
Tx off-axis angle $α_{t}$	$0^{\circ}$
Rx elevation angle $θ_{r}$	$20^{\circ}$
Half FOV angle $ϕ_{r}$	$50^{\circ}$
Rx off-axis angle $α_{r}$	$0^{\circ}$

θ_t	θ_r	movement path of the transmitter
θ_t	θ_r	0°	45°	90°	135°	180°
20°	20°	slowly falling	basically unchanged	slowly rising	slowly rising	slowly rising
40°	20°	gradually falling	basically unchanged	slowly rising	gradually rising	gradually rising
60°	20°	gradually falling	slightly falling	slowly rising	gradually rising	gradually rising
80°	20°	rapidly falling	slowly falling	rapidly rising	rapidly rising	rapidly rising

Parameter	Value
Wavelength $λ$	266 nm
Rayleigh scattering coefficients $k_{s}^{R}$	$0.24 \times 10^{- 3}$ m⁻¹
Mie scattering coefficients $k_{s}^{M}$	$0.25 \times 10^{- 3}$ m⁻¹
Absorption coefficients $k_{a}$	$0.74 \times 10^{- 3}$ m⁻¹
Receiving aperture radius $r$	$0.4 \times 10^{- 2}$ m
Rayleigh phase function scattering parameter $γ$	0.017
Mie phase function asymmetry parameter $g$	0.72
Mie phase function parameter $f$	0.5
Division times $M$	60
Speed of light $c$	$3 \times 10^{8}$ m/s

Parameter	Value
Tx elevation angle $θ_{t}$	$20^{\circ}$
Half-beam angle $ϕ_{t}$	$10^{\circ}$
Tx off-axis angle $α_{t}$	$0^{\circ}$
Rx elevation angle $θ_{r}$	$20^{\circ}$
Half FOV angle $ϕ_{r}$	$50^{\circ}$
Rx off-axis angle $α_{r}$	$0^{\circ}$

Research on pulse response characteristics of wireless ultraviolet communication in mobile scene

Abstract

1. Introduction

2. Research on pulse response in mobile scene based on RSM

2.1 Research method of pulse broadening in moving scenes

2.2 UV noncoplanar single-scatter transmission model based on RSM

2.3 Experimental validation

3. Simulation analysis

3.1 Influence of relative position change of nodes on pulse broadening when the geometric parameters of the transceiver are fixed

3.2 Effect of the change of the elevation angle of the transceiver on the pulse broadening in the moving scene

3.3 Effect of FOV angle variation on pulse width

3.4 Influence of beam angle on pulse response width

4. Conclusions

Funding

References

Cited By

Figures (11)

Tables (3)

Equations (5)

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