CN113783615A - Multi-relay communication method, system and control device for mixed visible light/radio frequency - Google Patents

Multi-relay communication method, system and control device for mixed visible light/radio frequency Download PDF

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CN113783615A
CN113783615A CN202110935743.8A CN202110935743A CN113783615A CN 113783615 A CN113783615 A CN 113783615A CN 202110935743 A CN202110935743 A CN 202110935743A CN 113783615 A CN113783615 A CN 113783615A
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relay
time slot
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CN113783615B (en
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李强
张智宣
葛晓虎
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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Abstract

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.

Description

Multi-relay communication method, system and control device for mixed visible light/radio frequency
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 circleiThe positions of all relays conform to a Poisson distribution, and the probability density function of the relay distribution is
Figure BDA0003213035670000021
N-0, 1, … wherein the set
Figure BDA0003213035670000022
Representing 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:
Figure BDA0003213035670000031
Figure BDA0003213035670000032
Figure BDA0003213035670000033
wherein A and B respectively represent source electrical signals xs(t) peak amplitude and DC offset, Pled、PaAnd PmaxRespectively representing the source transmitting power of each unit current, the maximum average power allowed by the source and the peak power;
probability of interruption
Figure BDA0003213035670000034
Wherein the content of the first and second substances,
Figure BDA0003213035670000035
the probability of interruption of the first link communication from the source to the relay,
Figure BDA0003213035670000036
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, OPAnd 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 RbAnd (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 RiAnd a signal sink D, wherein,
from source S to N relay nodes RiBroadcasting visible light signals xs(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 is1/260 degrees, the conical ground is centered on O and has radius r0A 3m circle. From source S to N relay nodes RiBroadcasting visible light signals xs(t) the radiation angle of each relay node is
Figure BDA0003213035670000061
Wherein
Figure BDA0003213035670000062
N relay nodes RiIs 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 riDistance d from the source Si(ii) a Each relay node is provided with a photoelectric detector, wherein psifovAnd psiiRespectively 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 RiBroadcasting visible light signals xs(t) wherein only N relay nodes R are requirediSelecting one relay receiving optical signal, and defining the selected relay as relay RbSink and relay node RbA distance of dDReceiving and decoding from the relay node RbOf the radio frequency signal.
The transmitted visible light signal x of the source S taking into account the security of the visible light transmissions(t) the following two constraints are satisfied, as shown in FIG. 4:
Figure BDA0003213035670000071
wherein P isled、PaAnd PmaxRepresenting the transmission power, average power and peak power of the source, respectively, a and B representing the signal x, respectivelysPeak amplitude and dc offset on (t).
In one embodiment, a plurality of relay nodes RiSubject to a Poisson distribution having a probability density function of
Figure BDA0003213035670000072
N-0, 1, … wherein the set
Figure BDA0003213035670000073
Represents relays that appear on the conical floor; relay selection method based on beacon positioning technologyTo a relay node RbThe 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 followsb：
(1) Selecting the relay closest to the source S from the N relay nodes, namely riThe smallest relay node is used as the relay node Rb。
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 relaysi≤r0) And is located within a distance threshold region (r)i≤rth) Wherein the relay node decodes the distance threshold rthDefined as follows, when the relay node RiDistance r from center Oi≤rthTime, relay node RiThe source signal can be successfully decoded; when r isi＞rthTime, relay node RiThe decoding fails. In particular, the method comprises the following steps of,
when r isth＜r0When the relay R is selected to be accessed, the relay R can be selected as followsb：
(2) From satisfying ri≤rthRandomly selects one relay node from all relay nodes as a relay node Rb。
When r isth＝r0When the relay R is selected to be accessed, the relay R can be selected as followsb：
(3) Randomly selecting one relay node from N relay nodes, namely satisfying ri≤r0Randomly selects one relay node from all relay nodes as a relay node Rb。
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 xs(t)＝Pled(x (t) + B), wherein PledRepresenting 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 xs(t) nonnegativity. In a first stage of the current time slot, controlling the selected relay to decode the optical signal, specifically, the relay RbThe photodetector converts the received optical signal into an electrical signal yb(t) and simultaneously separating y with a signal component separation strategyb(t) separation into a DC component ydcAnd an alternating current component yac(t) for energy harvesting and information decoding, respectively, wherein the harvested energy is denoted as Eb。
First hop source-relay node RiThe channel gain of the link is:
Figure BDA0003213035670000081
where n-1 is Lambertian radiation coefficient, LrWhich represents the surface area of the photodetector,
Figure BDA0003213035670000082
denotes the light concentrator gain,. epsilon.is the refractive index, Ts(ψi) Representing the optical filter gain.
First hop source-relay node RiThe link channel capacity is:
Figure BDA0003213035670000083
wherein
Figure BDA0003213035670000084
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,
Figure BDA0003213035670000091
is the noise power of additive white gaussian noise at the relay node.
When relay node RiDistance r from center Oi≤rthTime, relay node RiThe source signal can be successfully decoded, i.e. C1≥R0(ii) a When r isi＞rthTime, relay node RiDecoding 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 nodeth. 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 RbTransmitting power P of different information sourcesledLower system energy efficiency ηE-a predefined target rate R0And (5) a simulation graph. From FIG. 6, the system energy efficiency ηEWith 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 RbWhether 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 RbThe average interruption probability of the communication interruption of the first link is recorded as
Figure BDA0003213035670000092
When the first hop source-relay node RbChannel link capacity C1＜R0When is, i.e. rb＞rthWhen the first-hop decoding fails, the first-hop communication interruption probability is
Figure BDA0003213035670000093
Wherein r isbAs a relay node RbDistance 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 RbThe decoded information is forwarded to the sink D by means of radio frequency signals using the collected energy.
Relay node RbThe output electric signal on the photoelectric detector is expressed as
yb(t)＝yac(t)+ydc+n1(t)，
Wherein y isac(t)＝ρh1bPledx (t) is an alternating component, ydc＝ρh1bPledB is a direct-current component,
Figure BDA0003213035670000101
is additive white gaussian noise for the first hop link.
Wherein, the relay node RbThe energy collected is denoted as Eb＝fydcVoc＝fρh1bPledBVocWhere f is a fill factor, between 0.7 and 0.8, VocIs the open circuit voltage on the photodetector. In one embodiment, the relay node RbTransmitting the radio-frequency signal by using all the collected energy, i.e. Pb＝Eb＝fρh1bPledBVocIn which P isbAs a relay node RbThe 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 Rb-sink link communication outage, noting the average outage probability of the second hop as
Figure BDA0003213035670000102
The signal received by the signal sink D is
Figure BDA0003213035670000103
Wherein
Figure BDA0003213035670000104
Relaying node R for the second hopb-channel gain, upsilon, of the sink link is a path loss factor,
Figure BDA0003213035670000105
is additive white gaussian noise of the second hop link channel.
Further, the achievable rate of the second hop link channel is
Figure BDA0003213035670000106
Wherein
Figure BDA0003213035670000111
The 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
Figure BDA0003213035670000112
O since interrupt events of two-hop transmission are mutually exclusive to each otherPCan be expressed as a first-hop communication interruption probability
Figure BDA0003213035670000113
And second hop communication interruption probability
Figure BDA0003213035670000114
And (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 RbSystem end-to-end interruption probability O under selection methodPAnd source transmission power PledA simulation diagram of (1). As can be seen from the figure, with the source transmit power PledThe system outage probability under the 3 relay selection methods is reduced, and approaches to the probability of no relay in the circle, because of PledWill result in a relay node decoding distance threshold r of the first hopthAnd a second hop relay node RbTransmit power P ofbThereby resulting in an outage probability for the first and second hop signal transmissions, respectively
Figure BDA0003213035670000121
And
Figure BDA0003213035670000122
is reduced, and
Figure BDA0003213035670000123
approaching the probability of no relay in the circle, and
Figure BDA0003213035670000124
approaching 0. Meanwhile, it can be observed that in 3 relay selection methods, the nearest relay node is selected as the relay node RbWhen is no matter PledWhat is, the system end-to-end interrupt performance is best, at low PledRegion at rthInternal random selection ratio is r0When the internal random is selected, the selection is good, when P isledAfter increasing to a certain critical value, at rthInternal random sum is in r0The interrupt performance at internal random selection is the same, since it is no matter at rthInternal random selection of r0The relay node selected at random is not necessarily the nearest relay. Therefore, first hop outage probability when selecting the nearest relay
Figure BDA0003213035670000125
Is smallest, and
Figure BDA0003213035670000126
has no effect, and PledWill result in rthWhen P is increasedledWhen increasing to a certain threshold value, rthAnd 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:
Figure BDA0003213035670000127
Figure BDA0003213035670000128
and is
Figure BDA0003213035670000129
Under this premise, the end-to-end outage probability O is expressed abovePThe 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 as
Figure BDA00032130356700001210
In this embodiment, the signal x is rationally arranged at the initial stage of communication by estimation of probability theorysThe 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 RiThe 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.

Claims (10)

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 circleiThe positions of all relays conform to a Poisson distribution, and the probability density function of the relay distribution is
Figure FDA0003213035660000011
Wherein the set
Figure FDA0003213035660000012
Representing 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:
Figure FDA0003213035660000021
Figure FDA0003213035660000022
Figure FDA0003213035660000023
wherein A and B respectively represent source electrical signals xs(t) peak amplitude and DC offset, PledRepresenting the source transmission power per unit current, PaAnd PmaxRespectively representing the maximum average power and the peak power allowed by the information source;
probability of interruption
Figure FDA0003213035660000024
Wherein the content of the first and second substances,
Figure FDA0003213035660000025
the probability of interruption of the first link communication from the source to the relay,
Figure FDA0003213035660000026
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, OPAnd 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.
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