CN103475409B - Moving vehicle visible ray radio communication receives switching method and apparatus - Google Patents

Abstract

The invention discloses vehicle visible ray radio communication in a kind of movement and receive changing method, comprising: in the time there is signal overlap overlay area between adjacent transmission end, select the powerful information source of switching signal power to establish a communications link with it. When between adjacent transmission end when no signal overlay area, calculate unlapped distance between adjacent transmission end; Calculating enters the time before next transmitting terminal coverage; By calculating the data volume in the described time, allow terminal reserve so large cushion space, ensure to be during this period of time unlikely to display network immediately and disconnect. And the switching that applies to communicate by letter between vehicle and street lamp, successfully ensure communicating by letter between vehicle and street lamp.

Description

Moving vehicle visible ray radio communication receives switching method and apparatus

Technical field

The present invention relates to a kind of communications field, relate in particular to a kind of moving vehicle visible ray radio communication and receive switching method and apparatus.

Background technology

Visible light communication (VisibleLightCommunication, VLC) is a kind of in technical grow up new of white light LEDsEmerging light wireless communication technology. Compare with other light wireless communications with traditional radio communication, visible light communication has without electromagnetism dryDisturb, save the energy, have illumination communication function one concurrently, the green advantage such as harmless, visible VLC technology has greatlyDevelopment prospect.

The wireless short-distance that outdoor VLC is applicable in intelligent transportation system (ITS, IntelligentTransportationSystems) leads toLetter. The wireless short-range communication technology in ITS that is applied at present has WIFI, radio frequency etc. But, these line short-range communication techniqueExtra specific wireless apparatus need to be installed. Because the equipment such as LED traffic lights, LED street lamp, vehicle LED headlamp existConstantly popularization and application in traffic system, thereby VLC is progressively applied in ITS. And VLC applies in ITS, do not needWill again drop into extra wireless device construction, can reduce costs, and VLC is high without electromagnetic interference, reliability.

In prior art one, after deliberation VLC apply to communicate by letter between vehicle and traffic lights, communicate by letter between vehicle and vehicle,And the equipment such as vehicle and traffic lights is formed to a network, realize the functions such as vehicle location, and communication distance reaches 15-20 rice,But just consider point-to-point communication. In prior art two, for the research of the switching aspect of indoor VLC, but indoor environmentDifferent from outdoor environment, the interior space is little, does not exist complete no signal region and recipient's translational speed to be far smaller than the car that travelsSpeed. But in prior art, communicating by letter between moving vehicle and street lamp, is the communication of point-to-multipoint, therefore has multiple spotBetween selection switching and signal communication disruption problem while not covering.

Summary of the invention

While covering in order to overcome the selection switching that exists at present between multiple spot and signal, communication disruption problem, the present invention proposesA kind of visible ray radio communication receives switching method and apparatus.

The present invention proposes a kind of visible ray radio communication and receive changing method, comprising:

When between adjacent transmission end when no signal overlay area, calculate unlapped distance between adjacent transmission end;

Calculating enters the time before next transmitting terminal coverage;

By calculating the data volume in the described time, allow terminal reserve so large cushion space, ensure during this period of timeBeing unlikely to display network immediately disconnects.

Further, in said method, calculate unlapped distance between adjacent transmission end, calculating enters next transmitting terminal and coversTime before lid scope, be specially: between described adjacent transmission end, unlapped distance is L, the distance between adjacent transmission endFor D, LED equal altitudes is H, and maximum emission angle is 60 °, and L is:If receiving terminal advancesSpeed be v, the time entering so before next transmitting terminal coverage is t,

Further, in said method, also comprise: in the time there is signal overlap overlay area between adjacent transmission end, by signalBe divided into four class set: Candidate Set, Neighbor Set, residual set and Active Set; Described signal is joined to Neighbor Set, when this signalIntensity while being greater than signal detecting threshold, terminal is just put into Candidate Set by this signal, along with terminal moves on, when two basesWhen in standing, the signal strength signal intensity of one party has been removed thresholding lower than signal, at this moment startup is removed signal timing and is started to clock, to waitingEach signal in selected works retains one and removes signal timing; In the time that timing finishes, if original signal removes door lower than signal all the timeLimit, puts into this signal among Neighbor Set from Active Set, then again upgrades Active Set and Neighbor Set, from Candidate Set, selectsA suitable signal reconnects and starts communicates by letter.

Further, in said method, also comprise: setting current transmitting terminal is p in the received power of certain point_r1, p_r1CanBe expressed as,Wherein ψ is incidence angle, p_tFor transmitting power, h is LED street lamp height; IfNext transmitting terminal is p in the received power of this point_r2, p_r2Can be expressed as,Wherein ψ incidence angle, p_tFor transmitting power, h is LED street lamp height, and d is the horizontal range between two adjacent street lamps; ?Determine when next signal is stablized, introduce a timer, for ensureing whether the next signal that receives is stablized; This timerComputing timeWherein v is the speed that receiving terminal moves, and the distance dependent λ between two transmitting terminals of d isConstant between 0-1.

The present invention proposes a kind of moving vehicle visible ray radio communication and receive switching device shifter, comprising: bank switching module, forWhen between adjacent transmission end when no signal overlay area, calculate unlapped distance between adjacent transmission end; Calculating enters the next oneTime before transmitting terminal coverage; By calculating the data volume in the described time, allow terminal reserve so large buffering skyBetween, ensure to be during this period of time unlikely to display network immediately and disconnect.

Further, visible ray radio communication receives switching device shifter, also comprises: select handover module, for working as adjacent transmission endBetween while there is signal overlap overlay area, signal is divided into four class set: Candidate Set, Neighbor Set, residual set and Active Set;Described signal is joined to Neighbor Set, and in the time that the intensity of this signal is greater than signal detecting threshold, terminal is just put into time by this signalIn selected works, along with terminal moves on, in the time that the signal strength signal intensity of one party in two base stations has been removed thresholding lower than signal, thisShi Qidong removes signal timing and starts to clock, and each signal in Candidate Set is retained to one and remove signal timing; Work as timingWhen end, if original signal removes thresholding lower than signal all the time, this signal is put among Neighbor Set from Active Set, then again moreNew Active Set and Neighbor Set are selected a suitable signal to reconnect and start communication from Candidate Set.

By the invention described above, two kinds of RSP(ReceivingSignalPower received signal powers are proposed) handover scheme, andThe switching that applies to communicate by letter between vehicle and street lamp, has successfully ensured communicating by letter between vehicle and street lamp. Between adjacent street lamp, do not depositThe in the situation that of signal coverage areas, adopt RSP bank switching, ensure seamless link between moving vehicle and street lamp, adjacentBetween two street lamps, exist in the situation of signal overlap overlay area, adopted RSP to select to switch, can reduce the bit error rate of communication,Improve communication quality.

Brief description of the drawings

Fig. 1 is the LED road lamp wireless traffic model schematic diagram that has signal overlap in the embodiment of the present invention between adjacent street lamp;

Fig. 2 is the LED road lamp wireless traffic model schematic diagram that in the embodiment of the present invention, between adjacent street lamp, no signal covers;

Fig. 3 is the schematic diagram of the LED street lamp direct projection line-of-sight channel in the embodiment of the present invention;

Fig. 4 is the schematic diagram of the overlapping LED street lamp of the no signal in the embodiment of the present invention;

Fig. 5 has a signal overlap LED street lamp schematic diagram in the embodiment of the present invention.

Detailed description of the invention

Below in conjunction with accompanying drawing, technical scheme of the present invention is elaborated:

In VCL system, LED street lamp is similar is base station one by one, and the carrier signal of transmission is launched by LED street lampVisible ray, its illumination zone is exactly its signal cover, and the directionality of visible ray is very strong, along straightline propagation. Car travelsCommunicate with street lamp, LED street lamp is as signal sending end, and vehicle is as signal receiving end, and both enter by visible raySerial Communication, what affect performance is mainly direct light, in the process of calculating received power, will ignore irreflexive impact.

According to these characteristics, moving vehicle communicate by letter with LED street lamp can exist two kinds of situations, embodiment of the present invention moving vehicle withTwo kinds of situations that between LED street lamp, communication exists, as shown in Figure 1, cover for the present invention's two street lamp compartments exist signal overlapThe schematic diagram of the scene between the moving vehicle in region and LED street lamp, in this kind of situation, due to adjacent street lamp close together, depositsAt unlike signal, but the power of signal is along with the movement of vehicle is changing, and in the meantime, exists stronger signal and selects alsoThe problem of switching, driving vehicle is through out-of-date, and can there is too small situation in a certain signal, at this moment can adopt RSP(ReceivingSignalPower) select the powerful information source of switch selection signal power to establish a communications link with it.

Figure 2 shows that two street lamp compartments in the present invention do not exist between the moving vehicle in the region that signal covers and LED street lampThe schematic diagram of scene in this kind of situation, owing to not having signal to cover, now enters without any signal sending end for vehicleSerial Communication connects, and therefore has the problem that ensures seamless link. If under signal can not coverage condition, driving vehicle warpWhile crossing this section, signal can interrupt, and we adopt RSP bank switching method to realize the seamless link of communication. At LED street lampBetween use RSP bank switching scheme while there is the region of the overlapping covering of signal power, reserved buffer memory is proposed and by disconnection processThe information of transmission is first deposited into buffer memory and is realized seamless link.

Multiple LED street lamp power distribution situations are by the power distribution and constitution of single led street lamp, and single led street lamp is a kind of brightUncle's radiation model, if LED transmitting power is P_t, in transmitting terminal covering, the received power of any is:

P_r=H(0)P_t(1)

The direct sighting distance light DC current gain that wherein H (0) is channel.

Calculate by formula 1, can show that the whole figure of received power size distribution presents coniform and do not connect at boundary powerContinuous, show that thus while being positioned at coverage when changing the time,, during the closer to transmitting terminal, signal power is larger, otherwise power is less,If when this point exceeds coverage border, its signal power all will be considered as 0.

In scene situation between moving vehicle and the LED street lamp in the region covering for two street lamp compartment no signals, can adoptBy RSP bank switching method. As shown in Figure 4, no signal overlay area between adjacent street lamp, when receiving terminal exit illumination coverGai Shi, the interval between two continuous illumination lamps can affect the connection of communication, may disconnect server. Here can adopt RSPBank switching method, first estimates unlapped distance between adjacent transmission end, establishes distance for L, the distance between adjacent transmission endFrom being D, LED equal altitudes is H, and maximum emission angle is 60 °, and L is:

$L=D-2\×\tan \frac{\mathrm{\π}}{3}\×H---\left(2\right)$

If the speed that receiving terminal advances is v, the time entering so before next transmitting terminal coverage is t,

$t=\frac{L}{v}---\left(3\right)$

By the data volume in estimating during this period of time, and allow terminal reserve so large cushion space, ensure during this period of timeInside be unlikely to display network immediately and disconnect, or communication disruption. If average transmission rate is B. Reserved cushion space outSize G is

$G>\stackrel{\‾}{B}\×t---\left(4\right)$

There is the scene between moving vehicle and the LED street lamp of signal overlap overlay area during for two street lamp compartments, can adoptSelect changing method with RSP, as shown in Figure 5, there is the region of signal overlap in adjacent two transmitting terminals, in this case choosingSelect a suitable transmitting and bring in to communicate and just seem particularly important, can adopt RSP to select changing method to select to close hereSuitable transmitting terminal. Should be select switch have improve switch success rate, improve service quality, reduce the advantages such as power attenuation.

In VLC system, adopt RSP to select to switch, first signal to be divided into four class set: Candidate Set (CS), phaseAdjacent collection (NS), residual set (RS), Active Set (AS). Secondly introduce three important parameters, be respectively signal detecting threshold T_ADD,Signal removes thresholding T_DROP, removes signal timer T_TDROP.

Shown in Fig. 5, moving vehicle, turning right in moving process, supposes that this receiving terminal communicates with first transmitting terminal,In the time that entering signal is overlapping covered, receiving terminal scans another signal, first this signal is joined to Neighbor Set (NS),In the time that the intensity of this signal is greater than signal detecting threshold (T_ADD), terminal is just put into Candidate Set by this signal, along with terminalMove on, in the time that the signal strength signal intensity of one party in two base stations has been removed thresholding (T_DROP) lower than signal, at this moment start and goSwap signal timing (T_TDROP) starts to clock, and each signal in Candidate Set is retained to a T_TDROP. Work as timingWhen end, if original signal, all the time lower than T_DROP, is put into this signal among Neighbor Set (NS) from Active Set, then again moreNew Active Set (AS) and Neighbor Set (NS) are selected a suitable signal to reconnect and start communication from Candidate Set.

Adopt and select when handover scheme, most importantly the calculating to two watt levels in overlapping region firstSuppose that current transmitting terminal is p in the received power of certain point_r1, p_r1Can be expressed as:

$p_{r1}=p_t\×\frac{2A}{{\mathrm{\πh}}^2}{\cos }^4\left(\mathrm{\Ψ}\right)---\left(5\right)$

Wherein ψ is incidence angle, p_tFor transmitting power, h is LED street lamp height.

If next transmitting terminal is p in the received power of this point_r2, p_r2Can be expressed as:

$p_{r2}=p_t\×\frac{{2\mathrm{Ah}}^2}{\mathrm{\π}\left[{(d-h\tan {\left(\mathrm{\Ψ}\right)}^2+h^2)}^2\right]}---\left(6\right)$

Wherein ψ is incidence angle, p_tFor transmitting power, h is LED street lamp height, and d is the horizontal range between two adjacent street lamps.

Finally, in the time that definite next signal is stablized, introduce a timer, for ensureing whether the next signal that receives is stablized.Distance d between speed v and two transmitting terminals that the size of this timer T_TDROP computing time is moved by receiving terminal hasClose.

$T\_\mathrm{TDROP}=\frac{\mathrm{\λd}}{v}---\left(7\right)$

It is wherein a constant between 0-1.

According to the method described above, LED street lamp actual parameter can be set: under outdoor conditions, now suppose between street lamp and street lamp to beHave distance and fixing, in as Fig. 4 situation, according to actual parameter, the height of establishing LED street lamp is 3m, its luminous powerFor 15w, luminous flux is 1500lm, and beam angle is 60 °/120, and the area of vehicle receiving terminal is 1cm2, between LED street lampDistance be 15m. In as Fig. 5 situation, the distance between LED street lamp is 8m, and other parameters are consistent with Fig. 4.

RSP bank switching cache size is calculated: in the time adopting RSP bank switching method, first calculate not coverage itBetween distance be 4.6m. Known according to formula (3) (4), reserved cushion space size is with the speed relation that is inversely proportional to. According to vehicleGeneral travel speed, selected velocity interval: 10m/s-25m/s. In the time that speed is less, need enough large cushion spaceDeposit a large amount of bufferings. Along with the raising of speed, need reserved cushion space also to reduce thereupon.

According to the method described above, can arrange RSP select handoff parameter: when vehicle from current location to next LED street lampEnter in process, incidence angle also changes thereupon, according to formula (5), the received power p under current street lamp_r1Can be along with incidence angle ψ'sBecome large and diminish. And according to formula (6), next transmitting terminal is at the received power p of this point_r2Can be along with the change of incidence angle ψ becomes greatlyGreatly.

In handoff procedure, need constantly to monitor p_r1、p_r2Size variation, then by two parameter T_ADD and T_DROPSuitable threshold value is set, and according to the size of transmitting power, T_ADD is set to 3.63 × 10^-5W, T_DROP is set to2.8×10^-5W. In last moving process, first find p_r2Value be greater than T_ADD, and timer timing arrives, by this signalPut into Candidate Set, the more mobile p that finds_r1Be less than T_DROP, start timing, while end at that time, if be still less than this value, disconnectedOpen connection, starting with power is p_r2Signal connect.

The invention provides a kind of visible ray radio communication and receive switching device shifter, comprising: bank switching module, for working as adjacent transmissionBetween end, when no signal overlay area, calculate unlapped distance between adjacent transmission end; Calculating enters next transmitting terminal and coversTime before scope; By calculating the data volume in the described time, allow terminal reserve so large cushion space, ensureDuring this period of time, being unlikely to display network immediately disconnects. Select handover module, for there is signal overlap when between adjacent transmission end, signal is divided into four class set: Candidate Set, Neighbor Set, residual set and Active Set when the overlay area; Described signal is joinedNeighbor Set, in the time that the intensity of this signal is greater than signal detecting threshold, terminal is just put into Candidate Set by this signal, along with terminalMove on, in the time that the signal strength signal intensity of one party in two base stations has been removed thresholding lower than signal, at this moment start and remove signal meterIn time, starts to clock, and each signal in Candidate Set is retained to one and remove signal timing; In the time that timing finishes, if original signalAll the time remove thresholding lower than signal, this signal is put among Neighbor Set from Active Set, then again upgrade Active Set and adjacentCollection is selected a suitable signal to reconnect and starts communication from Candidate Set.

By the invention described above, two kinds of RSP handover schemes are proposed, and the switching that applies to communicate by letter between vehicle and street lamp, successfully protectHinder communicating by letter between vehicle and street lamp. In the situation that there is not signal coverage areas between adjacent street lamp, adopt RSP storageSwitch, ensure seamless link between moving vehicle and street lamp, between adjacent two street lamps, have the feelings of signal overlap overlay areaIn condition, adopt RSP to select to switch, can reduce the bit error rate of communication, improved communication quality.

Claims (4)

1. moving vehicle visible ray radio communication receives a changing method, it is characterized in that, comprising:

When between adjacent transmission end when no signal overlay area, calculate unlapped distance between adjacent transmission end; Calculating enters the next oneTime before transmitting terminal coverage; By calculating the data volume in the described time, allow terminal reserve so large buffering skyBetween, ensure to be during this period of time unlikely to display network immediately and disconnect;

In the time there is signal overlap overlay area between adjacent transmission end, signal is divided into four class set: Candidate Set, Neighbor Set, residueCollection and Active Set; Described signal is joined to Neighbor Set, and in the time that the intensity of this signal is greater than signal detecting threshold, terminal just willThis signal is put into Candidate Set, along with terminal moves on, when the signal strength signal intensity of one party in two base stations is gone lower than signalWhile falling thresholding, at this moment startup is removed signal timing and is started to clock, and each signal in Candidate Set is retained to one and remove signalTiming; In the time that timing finishes, if original signal removes thresholding lower than signal all the time, this signal is put among Neighbor Set from Active Set,Then again upgrade Active Set and Neighbor Set, from Candidate Set, select a suitable signal to reconnect and start communication.

2. moving vehicle visible ray radio communication as claimed in claim 1 receives changing method, it is characterized in that described calculating phaseUnlapped distance between adjacent transmitting terminal, calculates the time entering before next transmitting terminal coverage, is specially: described adjacentBetween transmitting terminal, unlapped distance is L, and the distance between adjacent transmission end is D, and LED equal altitudes is H, maximum emission angleBe 60 °, L is: $L=D-2\×tan\frac{\mathrm{\π}}{3}\×H;$

If the speed that receiving terminal advances is v, the time entering so before next transmitting terminal coverage is t,

3. moving vehicle visible ray radio communication as claimed in claim 2 receives changing method, it is characterized in that, also comprises: establishSettled front transmitting terminal is p in the received power of certain point_r1, p_r1Be expressed as,Wherein Ψ is for enteringFiring angle, p_tFor transmitting power, h is LED street lamp height; If next transmitting terminal is p in the received power of this point_r2, p_r2Be expressed as,The photodetector photosensitive area that wherein A is receiver, Ψ is for enteringFiring angle, p_tFor transmitting power, h is LED street lamp height, and d is the horizontal range between two adjacent street lamps;

In the time that definite next signal is stablized, introduce a timer, for ensureing whether the next signal that receives is stablized; This timingDevice computing timeWherein v is the speed that receiving terminal moves, and d is two distance dependents between transmitting terminalParameter lambda is the constant between 0-1.

4. moving vehicle visible ray radio communication receives a switching device shifter, it is characterized in that, comprising:

Bank switching module, for when between adjacent transmission end when no signal overlay area, calculates unlapped distance between adjacent transmission endFrom; Calculating enters the time before next transmitting terminal coverage; By calculating the data volume in the described time, make terminal pre-Reserve so large cushion space, ensure to be during this period of time unlikely to display network immediately and disconnect;

Select handover module, in the time there is signal overlap overlay area between adjacent transmission end, signal is divided into four class set: waitSelected works, Neighbor Set, residual set and Active Set; Described signal is joined to Neighbor Set, when the intensity of this signal is greater than signal inspectionWhile surveying thresholding, terminal is just put into Candidate Set by this signal, along with terminal moves on, when the signal of one party in two base stationsWhen intensity has been removed thresholding lower than signal, at this moment startup is removed signal timing and is started to clock, to each letter in Candidate SetNumber retain one remove signal timing; In the time that timing finishes, if original signal removes thresholding lower than signal all the time, by this signal from swashThe collection of living is put among Neighbor Set, then again upgrades Active Set and Neighbor Set, selects a suitable signal weight from Candidate SetNewly connect and start and communicate by letter.