阅读说明：本技术 混合可见光/射频的多中继通信方法、系统及控制装置 (Multi-relay communication method, system and control device for mixed visible light/radio frequency ) 是由 李强 张智宣 葛晓虎 于 2021-08-16 设计创作，主要内容包括：本发明公开了一种混合可见光/射频的多中继通信方法、系统及控制装置,通信方法包括：步骤A：在多个中继中选择一个中继接收信源发射的可见光信号；步骤B：在当前时隙内的第一阶段内控制中继对可见光信号进行解码,若解码失败,增大下一时隙信源电信号的峰值振幅并跳转至步骤A；若解码成功,在当前时隙内的第二阶段控制中继将解码后的信息通过射频信号转发给信宿；步骤C：若解码失败,增大下一时隙信源电信号的直流偏置并跳转至步骤A,若解码成功,在下一时隙直接跳转至步骤A。通过设置多个中继并结合合适的反馈调节来解决更换中继后导致的通信中断问题,可以有效地解决目前单中继模式下的通信易中断问题,提高了系统通信的灵活性和可靠性。(The invention discloses a multi-relay communication method, a system and a control device for mixing visible light/radio frequency, wherein the communication method comprises the following steps: step A: selecting one relay from a plurality of relays to receive the visible light signal transmitted by the information source; and B: b, controlling the relay to decode the visible light signal in the first stage in the current time slot, if the decoding fails, increasing the peak amplitude of the signal source electric signal of the next time slot and skipping to the step A; if the decoding is successful, controlling the relay to forward the decoded information to an information sink through a radio frequency signal in the second stage of the current time slot; and C: and if the decoding fails, increasing the direct current bias of the signal source electric signal of the next time slot and skipping to the step A, and if the decoding succeeds, skipping to the step A directly in the next time slot. The problem of communication interruption caused by relay replacement is solved by setting a plurality of relays and combining proper feedback adjustment, the problem of easy interruption of communication in the current single-relay mode can be effectively solved, and the flexibility and reliability of system communication are improved.)

1. A hybrid visible/radio multi-relay communication method, comprising:

step A: selecting one relay from a plurality of relays to receive the visible light signal transmitted by the information source;

and B: in the first stage in the current time slot, controlling the selected relay to decode the visible light signal and obtain a decoding result, judging whether the relay decoding is successful, and when the relay decoding fails, waiting for the next time slot to increase the peak amplitude of the signal source signal of the next time slot and skipping to the step A; when the relay decoding is successful, controlling the relay in the second stage in the current time slot to forward the decoded information to an information sink through a radio frequency signal;

and C: and B, judging whether the information sink decoding is successful, waiting for the next time slot to increase the direct current bias of the information source electric signal of the next time slot and jumping to the step A when the information sink decoding is failed, and maintaining the current electric signal of the information source in the next time slot and jumping to the step A when the information sink decoding is successful.

2. The hybrid visible/radio frequency multi-relay communication method according to claim 1, wherein a radiation area of the visible light signal emitted from the source in the indoor plane is defined as a circle center O and a radius r₀Each relay being at a distance r from the center of the circle_iThe positions of all relays conform to a Poisson distribution, and the probability density function of the relay distribution isWherein the setRepresenting the relay appearing on the conical floor.

3. The hybrid visible light/radio frequency multi-relay communication method according to claim 1, wherein the selecting one of the plurality of relays to receive the visible light signal transmitted from the source comprises:

selecting a relay closest to the information source from a plurality of relays to receive the optical signal transmitted by the information source;

or selecting any one relay which is positioned in the optical signal radiation area and positioned in the distance threshold area from the plurality of relays to receive the optical signal transmitted by the source, wherein the relays in the threshold distance area meet the requirement of successfully decoding the optical signal.

4. The hybrid visible light/radio frequency multi-relay communication method according to claim 1, wherein when the relay selected in the previous time slot is available and the position is not changed, the relay in the previous time slot is continuously selected in the current time slot to receive the optical signal transmitted by the source; when the relay selected in the last time slot is unavailable or the position changes, other relays are reselected to receive the optical signals transmitted by the source in the current time slot.

5. The hybrid visible/radio multi-relay communication method according to claim 1,

controlling the selected relay to decode the optical signal, comprising: converting the optical signal into an electric signal through a relay, dividing the electric signal into a direct current component and an alternating current component, decoding the alternating current component, and collecting energy of the direct current component;

controlling the relay to forward the decoded information to the sink via the radio frequency signal, including: the decoded information is forwarded to the sink via the radio frequency signal using the energy collected based on the dc component.

6. The hybrid visible/radio multi-relay communication method according to claim 1, further comprising setting an initial peak amplitude and an initial dc bias of the source electrical signal according to constraints and outage probabilities before step a, wherein

The constraint conditions include:

wherein A and B respectively represent source electrical signals x_s(t) peak amplitude and DC offset, P_ledRepresenting the source transmission power per unit current, P_aAnd P_maxRespectively representing the maximum average power and the peak power allowed by the information source;

probability of interruptionWherein the content of the first and second substances,the probability of interruption of the first link communication from the source to the relay,for the probability that the first link communication from the source to the relay is successful and the second link communication from the relay to the sink is interrupted, O_PAnd taking A and B at the minimum value as the initial peak amplitude and the initial direct current bias of the source electric signal.

7. The hybrid visible/radio multi-relay communication method according to claim 1, wherein a minimum variation Δ of the peak amplitude and the DC bias is set,

increasing the peak amplitude of the next time slot information source electrical signal, wherein the peak amplitude of the next time slot information source electrical signal is increased by delta, and the direct current bias of the next time slot information source electrical signal is reduced by delta;

and increasing the direct current bias of the next time slot source electric signal, wherein the step of increasing the direct current bias of the next time slot source electric signal by delta and the step of reducing the peak amplitude of the next time slot source electric signal by delta.

8. The hybrid visible light/radio frequency multi-relay communication method according to claim 1, further comprising, before jumping to step a, determining whether a preset communication duration is exceeded, ending the communication when the preset communication duration is exceeded, and jumping to step a when the preset communication duration is not exceeded.

9. A hybrid visible/radio frequency multi-relay communication control apparatus, comprising:

a selection unit for selecting one relay among the plurality of relays to receive the visible light signal transmitted by the source;

the relay control unit is used for controlling the selected relay to decode the optical signal and obtain a decoding result in the first stage in the current time slot, waiting for the next time slot to increase the peak amplitude of the signal source signal of the next time slot and trigger the selection unit when the relay decoding fails, and controlling the relay to forward the decoded information to the signal sink through the radio frequency signal in the second stage in the current time slot when the relay decoding succeeds;

and the information sink communication unit is used for acquiring the decoding result of the information sink, waiting for the next time slot to increase the direct current bias of the information source electric signal of the next time slot and trigger the selection unit when the information sink fails to decode, and maintaining the current electric signal of the information source and triggering the selection unit in the next time slot when the information sink succeeds in decoding.

10. A hybrid visible/radio multi-relay communication system, comprising:

the information source is used for converting the electric signal into a visible light signal;

the relays are positioned in the radiation area of the optical signals and used for receiving the visible light signals, decoding the visible light signals, transmitting the decoded visible light signals to the information sink and sending the relay decoding results to the control device;

the signal sink is used for receiving and decoding the radio frequency signal transmitted by the relay and feeding back a decoding result of the signal sink to the control device;

a control device according to claim 9.

Technical Field

The invention belongs to the technical field of wireless cooperative communication, and particularly relates to a hybrid visible light/radio frequency multi-relay communication method, system and control device.

Background

With the rapid development of the internet of things, a large number of mobile devices access to the network, so that the problem of lack of radio frequency resources is increasingly serious. The visible light communication has the characteristics of wide frequency band, low cost, no electromagnetic radiation and the like, and the effective bandwidth of signals of a communication system can be improved by utilizing visible light. The coverage of visible light is generally a limited cone-shaped area, and the emitted light beams are easily blocked by obstacles. Therefore, at present, a hybrid visible light/radio frequency communication technology is commonly used, a relay is arranged between an information source and an information sink, the information source transmits an optical signal to the relay, and the relay decodes the optical signal and forwards the decoded optical signal to the information sink, so that the problems of insufficient radio frequency band and easy blockage of the optical signal by a barrier are solved.

At present, only one relay is usually arranged between the information source and the information sink, namely, a single relay mode is arranged, once the relay fails or the position changes, the communication between the information source and the information sink is interrupted, and the reliability of the system is not high.

Disclosure of Invention

In view of the above drawbacks and needs of the prior art, the present invention provides a hybrid visible/radio multi-relay communication method, system and control device, which aims to solve the technical problem that communication between a source and a sink is easily interrupted due to instability of relay.

To achieve the above object, according to an aspect of the present invention, there is provided a hybrid visible light/radio frequency multi-relay communication method, including:

step A: selecting one relay from a plurality of relays to receive the visible light signal transmitted by the information source;

and B: in the first stage in the current time slot, the selected relay is controlled to decode the optical signal and obtain a decoding result, whether the relay decoding is successful is judged, and when the relay decoding fails, the next time slot is waited to increase the peak amplitude of the signal source signal of the next time slot and the step A is skipped; when the relay decoding is successful, controlling the relay in the second stage in the current time slot to forward the decoded information to an information sink through a radio frequency signal;

and C: and B, judging whether the information sink decoding is successful, waiting for the next time slot to increase the direct current bias of the information source electric signal of the next time slot and jumping to the step A when the information sink decoding is failed, and maintaining the current electric signal of the information source in the next time slot and jumping to the step A when the information sink decoding is successful.

Preferably, the radiation area of the visible light signal emitted by the source in the indoor plane is defined as the circle center O and the radius r₀Each relay being at a distance r from the center of the circle_iThe positions of all relays conform to a Poisson distribution, and the probability density function of the relay distribution isN-0, 1, … wherein the setRepresenting the relay appearing on the conical floor.

Preferably, the selecting one of the plurality of relays to receive the optical signal transmitted by the source includes:

selecting a relay closest to the information source from a plurality of relays to receive the optical signal transmitted by the information source;

or selecting any one relay which is positioned in the optical signal radiation area and positioned in the distance threshold area from the plurality of relays to receive the optical signal transmitted by the source, wherein the relays in the threshold distance area meet the requirement of successfully decoding the optical signal.

Preferably, when the relay selected in the previous time slot is available and the position is not changed, the relay of the previous time slot is continuously selected in the current time slot to receive the optical signal transmitted by the source; when the relay selected in the last time slot is unavailable or the position changes, other relays are reselected to receive the optical signals transmitted by the source in the current time slot.

Preferably, the first and second electrodes are formed of a metal,

controlling the selected relay to decode the optical signal, comprising: converting the visible light signal into an electric signal through a relay, dividing the electric signal into a direct current component and an alternating current component, decoding the alternating current component, and collecting the energy of the direct current component;

controlling the relay to forward the decoded information to the sink via the radio frequency signal, including: the decoded information is forwarded to the sink via the radio frequency signal using the energy collected based on the dc component.

Preferably, before step a, the method further comprises setting an initial peak amplitude and an initial dc offset of the source electrical signal according to constraints and outage probabilities, wherein

The constraint conditions include:

wherein A and B respectively represent source electrical signals x_s(t) peak amplitude and DC offset, P_led、P_aAnd P_maxRespectively representing the source transmitting power of each unit current, the maximum average power allowed by the source and the peak power;

probability of interruptionWherein the content of the first and second substances,the probability of interruption of the first link communication from the source to the relay,for the probability that the first link communication from the source to the relay is successful and the second link communication from the relay to the sink is interrupted, O_PAnd taking A and B at the minimum value as the initial peak amplitude and the initial direct current bias of the source electric signal.

Preferably, a minimum variation delta of the peak amplitude and the dc offset is set,

increasing the peak amplitude of the next time slot information source electrical signal, wherein the peak amplitude of the next time slot information source electrical signal is increased by delta, and the direct current bias of the next time slot information source electrical signal is reduced by delta;

and increasing the direct current bias of the next time slot source electric signal, wherein the step of increasing the direct current bias of the next time slot source electric signal by delta and the step of reducing the peak amplitude of the next time slot source electric signal by delta.

Preferably, before jumping to step a, the method further includes determining whether a preset communication duration is exceeded, ending the communication when the preset communication duration is exceeded, and jumping to step a when the preset communication duration is not exceeded.

According to another aspect of the present invention, there is provided a hybrid visible light/radio frequency multi-relay communication control apparatus, comprising:

a selection unit for selecting one relay among the plurality of relays to receive the visible light signal transmitted by the source;

the relay control unit is used for controlling the selected relay to decode the optical signal and obtain a decoding result in the first stage in the current time slot, waiting for the next time slot to increase the peak amplitude of the signal source signal of the next time slot and trigger the selection unit when the relay decoding fails, and controlling the relay to forward the decoded information to the signal sink through the radio frequency signal in the second stage in the current time slot when the relay decoding succeeds;

and the information sink communication unit is used for acquiring the decoding result of the information sink, waiting for the next time slot to increase the direct current bias of the information source electric signal of the next time slot and trigger the selection unit when the information sink fails to decode, and maintaining the current electric signal of the information source and triggering the selection unit in the next time slot when the information sink succeeds in decoding.

According to still another aspect of the present invention, there is provided a hybrid visible/radio frequency multi-relay communication system, including:

the information source is used for converting the electric signal into a visible light signal;

the relays are positioned in the radiation area of the optical signals and used for receiving the optical signals, decoding the optical signals, transmitting the decoded optical signals to an information sink and sending the relay decoding results to the control device;

the signal sink is used for receiving and decoding the radio frequency signal transmitted by the relay and feeding back a decoding result of the signal sink to the control device;

a control device, said control device being the control device described above.

Generally speaking, according to the above technical solution of the present invention, by setting a plurality of relays, different relays can be selected in each time slot according to actual situations and requirements. After the relay is converted, the position of the relay node is changed, and communication interruption is possibly caused, so that the scheme is adaptive to a corresponding feedback regulation function, after the relay is selected in each time slot, whether normal decoding communication can be carried out between the information source and the information sink is judged, when the normal decoding communication cannot be carried out, the information source electric signal is fed back and regulated, the communication between the information source and the information sink is divided into first link communication from the information source to the relay and second link communication from the relay to the information sink for analysis, when the first link communication is interrupted, the peak amplitude of the information source electric signal is regulated, and when the second link communication is interrupted, the direct current bias of the information source electric signal is regulated until the decoding is successful. In the method, the problem of communication interruption caused by relay replacement is solved by setting a plurality of relays and combining proper feedback adjustment, the problem of easy interruption of communication in the current single-relay mode can be effectively solved, and the flexibility and reliability of system communication are greatly improved.

Drawings

Fig. 1 is a schematic model diagram of a hybrid visible light/radio frequency multi-relay communication system according to an embodiment of the present invention;

fig. 2 is a flowchart illustrating steps of a hybrid visible light/radio frequency multi-relay communication method according to an embodiment of the present invention;

fig. 3 is a flowchart illustrating steps of a hybrid visible light/radio frequency multi-relay communication method according to another embodiment of the present invention;

FIG. 4 is a diagram illustrating the feasible ranges of peak amplitude A and DC offset B under two constraints according to an embodiment of the present invention;

fig. 5 is a simulation result diagram of system end-to-end interruption probability-source transmission power under 3 relay selection schemes provided in an embodiment of the present invention;

fig. 6 shows an embodiment of the present invention for selecting a nearest relay node as R_bAnd (3) a simulation result graph of system energy efficiency-predefined target rate under different information source transmitting powers.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

To facilitate understanding of the communication method, a communication system used in the communication scheme will be described. As shown in figure 1, the multi-relay communication system of mixed visible light/radio frequency comprises a signal source S, N relay nodes R_iAnd a signal sink D, wherein,

from source S to N relay nodes R_iBroadcasting visible light signals x_s(t) the coverage area of the light source S is conical in view of the characteristics of the light source radiation. For example, the source S may be an LED light source located on the ceiling of a room, the height of the light source from the ground is 2m, and the half-power angle Φ of the light source S is_1/260 degrees, the conical ground is centered on O and has radius r₀A 3m circle. From source S to N relay nodes R_iBroadcasting visible light signals x_s(t) the radiation angle of each relay node isWherein

N relay nodes R_iIs an indoor movable device, such as a trolley in a supermarket, a vehicle in a parking lot and the like, is arranged on the bottom surface of the LED information source radiation area, and the distance from the center of the circle O is r_iDistance d from the source S_i(ii) a Each relay node is provided with a photoelectric detector, wherein psi_fovAnd psi_iRespectively the field angle and the angle of incidence of the photodetector.

The information sink D is positioned outside the communication coverage range of the information source S and receives and decodes the radio frequency signal from the relay node.

Based on the above communication system, as shown in fig. 2, a flowchart of steps of a hybrid visible light/radio frequency multi-relay communication method in an embodiment of the present invention is shown, where the communication method includes:

step S100: one of the relays is selected to receive the optical signal transmitted by the source.

In one embodiment, the source S is directed to N relay nodes R_iBroadcasting visible light signals x_s(t) wherein only N relay nodes R are required_iSelecting one relay receiving optical signal, and defining the selected relay as relay R_bSink and relay node R_bA distance of d_DReceiving and decoding from the relay node R_bOf the radio frequency signal.

The transmitted visible light signal x of the source S taking into account the security of the visible light transmission_s(t) the following two constraints are satisfied, as shown in FIG. 4:

wherein P is_led、P_aAnd P_maxRepresenting the transmission power, average power and peak power of the source, respectively, a and B representing the signal x, respectively_sPeak amplitude and dc offset on (t).

In one embodiment, a plurality of relay nodes R_iSubject to a Poisson distribution having a probability density function ofN-0, 1, … wherein the setRepresents relays that appear on the conical floor; relay selection method based on beacon positioning technologyTo a relay node R_bThe radio frequency signal is transmitted to the sink D.

In one embodiment, when the distance of each relay from center O is known, the accessed relay R may be selected as follows_b：

(1) Selecting the relay closest to the source S from the N relay nodes, namely r_iThe smallest relay node is used as the relay node R_b。

In one embodiment, when the distance of each relay from the center O is unknown, the optical signal radiation area (r) can be selected among the plurality of relays_i≤r₀) And is located within a distance threshold region (r)_i≤r_th) Wherein the relay node decodes the distance threshold r_thDefined as follows, when the relay node R_iDistance r from center O_i≤r_thTime, relay node R_iThe source signal can be successfully decoded; when r is_i＞r_thTime, relay node R_iThe decoding fails. In particular, the method comprises the following steps of,

when r is_th＜r₀When the relay R is selected to be accessed, the relay R can be selected as follows_b：

(2) From satisfying r_i≤r_thRandomly selects one relay node from all relay nodes as a relay node R_b。

When r is_th＝r₀When the relay R is selected to be accessed, the relay R can be selected as follows_b：

(3) Randomly selecting one relay node from N relay nodes, namely satisfying r_i≤r₀Randomly selects one relay node from all relay nodes as a relay node R_b。

Step S200: and in the first stage in the current time slot, controlling the selected relay to decode the optical signal and obtain a decoding result.

This is the first link communication from the source to the relay.

The visible light signal emitted by the source S is x_s(t)＝P_led(x (t) + B), wherein P_ledRepresenting the unit current emission power of the source S, x (t) is a modulated electrical signal with peak amplitude A and desired 0, and B is a DC bias applied to x (t) to ensure that x_s(t) nonnegativity. In a first stage of the current time slot, controlling the selected relay to decode the optical signal, specifically, the relay R_bThe photodetector converts the received optical signal into an electrical signal y_b(t) and simultaneously separating y with a signal component separation strategy_b(t) separation into a DC component y_dcAnd an alternating current component y_ac(t) for energy harvesting and information decoding, respectively, wherein the harvested energy is denoted as E_b。

First hop source-relay node R_iThe channel gain of the link is:

where n-1 is Lambertian radiation coefficient, L_rWhich represents the surface area of the photodetector,denotes the light concentrator gain,. epsilon.is the refractive index, T_s(ψ_i) Representing the optical filter gain.

First hop source-relay node R_iThe link channel capacity is:

wherein

Where ρ is the responsivity, γ, of the photodetector on the relay node₁Is the first hop link power gain, e is the base of the natural logarithm,is the noise power of additive white gaussian noise at the relay node.

When relay node R_iDistance r from center O_i≤r_thTime, relay node R_iThe source signal can be successfully decoded, i.e. C₁≥R₀(ii) a When r is_i＞r_thTime, relay node R_iDecoding failure, i.e. C₁＜R₀. By making C₁＝R₀And the obtained distance between the relay and the circle center is the decoding distance threshold r of the relay node_th. Wherein R is₀For a predefined target rate, R₀The value of (a) can be selected according to the simulation result, as shown in fig. 6, for selecting the nearest relay node as R_bTransmitting power P of different information sources_ledLower system energy efficiency η_E-a predefined target rate R₀And (5) a simulation graph. From FIG. 6, the system energy efficiency η_EWith a predefined target rate R₀Is increased and then decreased, so that a target rate R for maximizing energy efficiency can be obtained₀。

Step S300: and judging whether the relay decoding is successful.

Determining Relay R_bWhether the decoding is successful, when the relay decoding fails, step S400 is performed. When the relay decoding is successful, step S500 is performed.

At this time, the first hop source-relay node R_bThe average interruption probability of the communication interruption of the first link is recorded as

When the first hop source-relay node R_bChannel link capacity C₁＜R₀When is, i.e. r_b＞r_thWhen the first-hop decoding fails, the first-hop communication interruption probability is

Wherein r is_bAs a relay node R_bDistance from the center O.

Step S400, wait for the next time slot to increase the peak amplitude of the source electrical signal of the next time slot and jump to step S100.

In an embodiment, as shown in fig. 3, before jumping to step S100, the method further includes:

judging whether the current communication time length exceeds the preset communication time length or not, and if not, skipping to the step S100; and if the preset communication time length is exceeded, ending the communication.

In one embodiment, the peak amplitude and the minimum variation Δ of the dc offset are set, and in step S400, the next slot source electrical signal is adjusted to increase the peak amplitude of x (t), i.e., a ═ a + Δ, and decrease the dc offset, i.e., B ═ B- Δ, so as to improve the decoding success rate of the relay.

And step S500, controlling the relay to forward the decoded information to the information sink through the radio frequency signal in the second stage of the current time slot.

In the second phase of the time slot, the relay node R_bThe decoded information is forwarded to the sink D by means of radio frequency signals using the collected energy.

Relay node R_bThe output electric signal on the photoelectric detector is expressed as

y_b(t)＝y_ac(t)+y_dc+n₁(t)，

Wherein y is_ac(t)＝ρh_1bP_ledx (t) is an alternating component, y_dc＝ρh_1bP_ledB is a direct-current component,is additive white gaussian noise for the first hop link.

Wherein, the relay node R_bThe energy collected is denoted as E_b＝fy_dcV_oc＝fρh_1bP_ledBV_ocWhere f is a fill factor, between 0.7 and 0.8, V_ocIs the open circuit voltage on the photodetector. In one embodiment, the relay node R_bTransmitting the radio-frequency signal by using all the collected energy, i.e. P_b＝E_b＝fρh_1bP_ledBV_ocIn which P is_bAs a relay node R_bThe transmit power of.

The signal sink D tries to decode the received radio frequency signal and feeds back the decoding result.

Step S600: it is judged whether the sink decoding is successful.

When the relay decoding fails, step S700 is performed. When the relay decoding is successful, step S800 is performed.

Communication from the relay to the sink is defined as second link communication.

If the second hop relay node R_b-sink link communication outage, noting the average outage probability of the second hop as

The signal received by the signal sink D isWhereinRelaying node R for the second hop_b-channel gain, upsilon, of the sink link is a path loss factor,is additive white gaussian noise of the second hop link channel.

Further, the achievable rate of the second hop link channel isWhereinThe noise power of the second hop link channel.

Further, if R₂＜R₀If the second hop decoding fails, the probability of second hop communication interruption is that the first link communication from the source to the relay is successful and the second link communication from the relay to the sink is successfulThe probability of a disruption of the path communication can be expressed as

O since interrupt events of two-hop transmission are mutually exclusive to each other_PCan be expressed as a first-hop communication interruption probabilityAnd second hop communication interruption probabilityAnd (4) summing.

Step S700: waiting for the next time slot to increase the dc offset of the source electrical signal of the next time slot and jumping to step S100.

In an embodiment, as shown in fig. 3, before jumping to step S100, the method further includes:

judging whether the current communication time length exceeds the preset communication time length or not, and if not, skipping to the step S100; and if the preset communication time length is exceeded, ending the communication.

In one embodiment, the peak amplitude and the minimum variation Δ of the dc offset are set, and in step S700, the next slot source electrical signal is adjusted to decrease the peak amplitude of x (t), i.e., a ═ a- Δ, and increase the dc offset, i.e., B ═ B + Δ, so as to improve the decoding success rate of the relay.

Step S800: the source current electrical signal is maintained in the next slot and the process jumps to step S100.

If the decoding is successful, the source electrical signal does not need to be adjusted, and the communication is continued according to the current electrical signal in the next time slot.

In the scheme, the relay can be reselected for each time slot, wherein whether the relay needs to be changed or not for each time slot can be selected according to the actual situation of inventory. In one embodiment, when the relay selected in the previous time slot is available and the position is not changed, the relay in the previous time slot is continuously selected in the current time slot to receive the optical signal transmitted by the source; when the relay selected in the last time slot is unavailable or the position changes, other relays are reselected to receive the optical signals transmitted by the source in the current time slot.

When the current time slot reselects the optical signals transmitted by other relay receiving sources, the selection can be performed according to the 3 ways described above. As shown in fig. 5 as 3 different relay nodes R_bSystem end-to-end interruption probability O under selection method_PAnd source transmission power P_ledA simulation diagram of (1). As can be seen from the figure, with the source transmit power P_ledThe system outage probability under the 3 relay selection methods is reduced, and approaches to the probability of no relay in the circle, because of P_ledWill result in a relay node decoding distance threshold r of the first hop_thAnd a second hop relay node R_bTransmit power P of_bThereby resulting in an outage probability for the first and second hop signal transmissions, respectivelyAndis reduced, andapproaching the probability of no relay in the circle, andapproaching 0. Meanwhile, it can be observed that in 3 relay selection methods, the nearest relay node is selected as the relay node R_bWhen is no matter P_ledWhat is, the system end-to-end interrupt performance is best, at low P_ledRegion at r_thInternal random selection ratio is r₀When the internal random is selected, the selection is good, when P is_ledAfter increasing to a certain critical value, at r_thInternal random sum is in r₀The interrupt performance at internal random selection is the same, since it is no matter at r_thInternal random selection of r₀The relay node selected at random is not necessarily the nearest relay. Therefore, first hop outage probability when selecting the nearest relayIs smallest, andhas no effect, and P_ledWill result in r_thWhen P is increased_ledWhen increasing to a certain threshold value, r_thAnd r₀Is the same, so after the threshold value, the interrupt performance is the same for both cases.

In one embodiment, at the beginning of communication, i.e. before the beginning of the first timeslot or during the first timeslot, the initial peak amplitude and the initial dc bias of the source electrical signal are set according to the constraint and the outage probability.

Specifically, the feasible regions of the peak amplitude a and the dc offset B are obtained according to the constraint conditions of the optical signal: and isUnder this premise, the end-to-end outage probability O is expressed above_PThe peak amplitude a and dc offset B at which the lowest is reached serve as the initial peak amplitude and initial dc offset of the source electrical signal.

During communication, the lower the probability of communication interruption is, the lower the energy efficiency of the system can be improved to some extent, and the relationship between the energy efficiency and the interruption probability can be expressed asIn this embodiment, the signal x is rationally arranged at the initial stage of communication by estimation of probability theory_sThe peak amplitude A and the DC offset B of (t) enable information flow and energy flow between two hops to be balanced, and the end-to-end communication interruption probability is minimized, so that the communication system is improvedEnergy efficiency of (2).

The present invention also relates to a hybrid visible/radio multi-relay communication control device, comprising:

a selection unit for selecting one relay among the plurality of relays to receive the visible light signal transmitted by the source;

the relay control unit is used for controlling the selected relay to decode the optical signal and obtain a decoding result in the first stage in the current time slot, waiting for the next time slot to increase the peak amplitude of the signal source signal of the next time slot and trigger the selection unit when the relay decoding fails, and controlling the relay to forward the decoded information to the signal sink through the radio frequency signal in the second stage in the current time slot when the relay decoding succeeds;

and the information sink communication unit is used for acquiring the decoding result of the information sink, waiting for the next time slot to increase the direct current bias of the information source electric signal of the next time slot and trigger the selection unit when the information sink fails to decode, and maintaining the current electric signal of the information source and triggering the selection unit in the next time slot when the information sink succeeds in decoding.

The invention also relates to a multi-relay communication system, as shown in fig. 1, comprising:

the information source S is used for converting the electric signal into a visible light signal;

multiple relays R_iThe relay decoding device is positioned in the radiation area of the optical signal and used for receiving the optical signal, decoding the optical signal, transmitting the decoded optical signal to an information sink and sending a relay decoding result to the control device;

the signal sink D is used for receiving and decoding the radio frequency signal transmitted by the relay and feeding back a signal sink decoding result to the control device;

a control device (not shown in fig. 1), which is the control device described above.

Generally speaking, according to the above technical solution of the present invention, by setting a plurality of relays, different relays can be selected in each time slot according to actual situations and requirements. After the relay is converted, the position of the relay node is changed, and communication interruption is possibly caused, so that the scheme is adaptive to a corresponding feedback regulation function, after the relay is selected in each time slot, whether normal decoding communication can be carried out between the information source and the information sink is judged, when the normal decoding communication cannot be carried out, the information source electric signal is fed back and regulated, the communication between the information source and the information sink is divided into first link communication from the information source to the relay and second link communication from the relay to the information sink for analysis, when the first link communication is interrupted, the peak amplitude of the information source electric signal is regulated, and when the second link communication is interrupted, the direct current bias of the information source electric signal is regulated until the decoding is successful. In the method, the problem of communication interruption caused by relay replacement is solved by setting a plurality of relays and combining proper feedback adjustment, the problem of easy interruption of communication in the current single-relay mode can be effectively solved, and the flexibility and reliability of system communication are greatly improved.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.