Fuzzy Based Network Assignment and Link-Switching Analysis

Research ArticleFuzzy Based Network Assignment and Link-Switching Analysisin Hybrid OCCLiFi System

Moh Khalid Hasan Mostafa Zaman Chowdhury Md Shahjalal and Yeong Min Jang

Department of Electronics Engineering Kookmin University Seoul 02707 Republic of Korea

Correspondence should be addressed to Yeong Min Jang yjangkookminackr

Received 3 August 2018 Accepted 4 November 2018 Published 19 November 2018

Academic Editor Laurie Cuthbert

Copyright copy 2018 Moh Khalid Hasan et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

In recent times optical wireless communications (OWC) have become attractive research interest in mobile communication forits inexpensiveness and high-speed data transmission capability and it is already recognized as complementary to radio-frequency(RF) based technologies Light fidelity (LiFi) and optical camera communication (OCC) are two promising OWC technologies thatuse a photo detector (PD) and a camera respectively to receive optical pulses These communication systems can be implementedin all kinds of environments using existing light-emitting diode (LED) infrastructures to transmit data However both networkinglayers suffer from several limitations An excellent solution to overcoming these limitations is the integration of OCC and LiFi Inthis paper we propose a hybrid OCC and LiFi architecture to improve the quality-of-service (QoS) of users A network assignmentmechanism is developed for the hybrid system A dynamic link-switching technique for efficient handover management betweennetworks is proposed afterward which includes switching provisioning based on usermobility and detailed network switching flowanalysis Fuzzy logic (FL) is used to develop the proposed mechanisms A time-division multiple access (TDMA) based approachcalled round-robin scheduling (RRS) is also adopted to ensure fairness in time resource allocation while serving multiple usersusing the same LED in the hybrid system Furthermore simulation results are presented taking different practical applicationscenarios into considerationThe performance analysis of the network assignment mechanism which is provided at the end of thepaper demonstrates the importance and feasibility of the proposed scheme

1 Introduction

Communication currently relies on the radio-frequency (RF)spectrum which is overcrowded and strictly regulated [1]Because of several factors including interference limitedresources and human safety it is obvious that RF basedtechnologies will not be sufficient to manage the massivefuture data traffic Wireless communication using the opticalspectrum has been regarded as a congruent solution to thespectrum congestion of RF based technologies [2ndash6] Inparticular the optical wireless technology especially visiblelight communication (VLC) has added a new dimension inthe world of mobile communications for its huge unregulatedspectrum (up to 800 THz [7]) cost effectiveness energy effi-ciency and high security [3 8 9] Moreover current indoorand outdoor environments are currently heavily congested

with light-emitting diode (LED) based lighting infrastruc-tures enabling VLC to be exploited as a complementarytechnology to RF

Light fidelity (LiFi) is a subset of OWC technology inwhich a photo detector (PD) receives the variation in theintensity of light which carries data bits encoded from thelight source [3 10 11] A PD can detect high-speed LEDflickering a capability that enables LiFi to support highdata rates An extensive improvement in bandwidth reuse isobserved for LiFi technologies resulting in excellent spectralefficiency Because of these benefits provided by LiFi severalarchitectures integrating LiFi and RF have been already pro-posed to enhance the quality-of-service (QoS) of users thesearchitectures include those that manage resource allocation[12ndash15] dynamic handover [16 17] energy harvesting [18]delay analysis [19] and channel assignment [20]

HindawiWireless Communications and Mobile ComputingVolume 2018 Article ID 2870518 15 pageshttpsdoiorg10115520182870518

2 Wireless Communications and Mobile Computing

However LiFi cannot be efficiently utilized in daylightbecause it suffers from extensive interference generated bysunlight [3] In indoor environments it can suffer from thesame problem resulting from neighboring lighting infras-tructures LiFi has a low signal-to-interference-plus-noiseratio (SINR) because it is heavily affected by the inter-ferences generated by adjacent light sources In additionthe communication distance that can be obtained usingLiFi is comparatively short with respect to other existingtechnologies These limitations inspire further research onthe optimum potentiality of LiFi in practical environments

Optical camera communication (OCC) is a recentlyintroduced VLC technique that uses an image sensor toreceive optical signals [21ndash26] The exponential growthin camera-mounted smart devices has enabled OCC tobe utilized in innovative application scenarios such asindooroutdoor positioning [27 28] localized advertising[29] digital signage and vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communications [30ndash32] OCC hasadded significant user flexibility with the use of smartphonecameras to receive data from LEDs Furthermore OCCis highly stable in terms of variations in communicationdistance Because of the limited angle-of-view (AoV) ofcameras OCC is less affected by interferences generated fromneighboring LEDsHowever similar to LiFi OCC has severallimitations For example because of the meager samplingrates of current commercial cameras OCC offers a low datarate which particularly decreases the user QoS

Until now a hybrid OCC and LiFi model had not beendeveloped In this study a hybrid networking architectureintegrating OCC and LiFi is proposed to enhance the userQoS The network is assigned to users through utilizationof fuzzy logic (FL) FL is a convenient approach to mapan input to an output and is provided on the basis ofseveral truth scores ranging from 0 to 1 [33] This method isflexible and intuitive without far-reaching complexity whichare characteristics that lead us to choose this approachWe propose a new network assignment mechanism insidethe LED cell (the entire coverage area of the LED) forusers Fuzzy inputs are chosen using the parameters thatdetermine the quality of both networks The fuzzy rules aregenerated by considering real-world application scenariosof users The center-of-gravity (CoG) method is used todefuzzify the inputs and obtain mark allocations for eachuser Furthermore we develop a FL-based vertical link-switching mechanism between the networking layers asboth of the networks support user mobility We brieflydiscuss the switching probability and corresponding networkswitching flow analysis of the hybrid system Round-robinscheduling (RRS) [34] an existing time-division multipleaccess (TDMA) approach is adopted to ensure fairness inresource allocation among users

The remainder of the paper is organized as followsSection 2 provides a system overview and an analysis onchannel parameters which includes theoretical representa-tions of SINR for both technologies The FL-based networkassignment mechanism including a discussion on user QoSis explained in Section 3 Sections 4 and 5 describe the link-switching strategy and the network switching flow process

respectively The performance of the assignment mechanismis evaluated in Section 6 which also includes a discussionof the outage probability and QoS performance A briefsummary of our work is provided in Section 7 FinallySection 8 presents future research possibilities related to ourproposed hybrid infrastructure

2 System Overview

21 Hybrid System Architecture In this study a hybridOCCLiFi networking layer is considered Taking usermobil-ity into account this hybrid system can serve multiple usersTherefore the hybrid system is suitable for any roamingor stationary user A particular LED is configured by twoparallel LED-driving circuitries Although both technologiesuse the same optical spectrum no interference will begenerated because the TDMA based RRSmethod is exploitedto allocate time resources when there are multiple usersA generalized block diagram of our proposed architectureis shown in Figure 1 The PD can receive high-rate LEDflickering whereas a camera cannot Current commercialcameras are configured with low frame rates (in most cases30ndash50 frames per second) This configuration particularlyreduces the modulation bandwidth of OCC [35 36] It is alsoworth noting that the LEDflickering must not be observed byhuman eyes (equivalent to a threshold of approximately 100Hz [37])

22 OCC Channel Model For a VLC system the route foroptical signal transmission has two components line-of-sight (LOS) and non-line-of-sight (NLOS) Because of thenature of camera pixels region-of-interest (RoI) mechanismsare applied for OCC by which the reflection componentof the transmitted signal is spatially separated from theLOS component [23] An indoor hybrid system with thetransmitter and receiver presented at Tx and Rx respectivelyis illustrated in Figure 2 The LED cell represents the entirecoverage area of the LED

The LOS channel for optical signal transmission is mod-eled by Lambertian radiant intensity which is represented bythe following equation [38]

119877119900 (120572) = (119898119897 + 1) cos119898119897 (120572119894119903)2120587 (1)

where 120572119894119903 signifies the angle of irradiance of the LED 119898119897 isthe Lambertian emission index which originates from theradiation angle Ψ12 called the radiation semiangle of theLED119898119897 is defined as

119898119897 = minuslogcosΨ122 (2)

We assume that the Euclidean distance between Tx andRx is 119889119886119887 which is calculated from the horizontal distance119889119887119909 and the vertical distance 119889119886ℎ (119889119886119887 = radic1198892119886ℎ + 1198892119887119909) Theoverall DC channel gain for OCC is formulated as [12]

119867119868119878119905119903 = 119892119900119901 cos (120572119894119899) Δ 119900119888119888119877119900 (120572)1198601198881198892119886119887 (3)

Wireless Communications and Mobile Computing 3

Input data

Encoder Modulator LED driver

AD

Output data

AmplificationPD

Framesampling

OCC transmitter OCC receiver

LED

DA Modulator LED driver

Demodulator

Demodulator

Decoder

ImageSensor

LiFi transmitter LiFi receiver

Figure 1 Basic block diagram of the hybrid OCCLiFi architecture

LED

LiFi dongle

FOV of PDAoV of Camera

Smartphone camera

Gateway dbx

daℎ

minus ir

info

dab

２Ｒ

ao

４Ｒ

LED cell

Figure 2 Data transmission model for the hybrid network

where 120572119894119899 implies the corresponding angle of incidence119892119900119901 represents the gain of the optical filter and Δ 119900119888119888 is arectangular function whose value implies that the channelhas no gain if the LED remains outside of the angle-of-view(AoV) of camera receiver If 120573119886119900V is the AoV of the camerathen Δ 119900119888119888 is represented as

Δ 119900119888119888 = 0 120572119894119899 ge 120573119886119900V1 120572119894119899 lt 120573119886119900V (4)

119860119888 is the area of the entire image of the LED projected inthe image sensor It is often signified by the number of pixelsoccupied by the image If120588 denotes the pixel edge length thenthe projected area is

119860119888 = 119860 119897119891119900212058821198892119886119887

(5)

where 119891119900 denotes the focal length of the camera and 119860 119897represents the physical area of the LED

There is a minimum area of the projected image in theimage sensor below which the transmitted data cannot be

decodedThe power received by the image sensor in this caseis termed as the threshold power and expressed as

119875119868119878119905ℎ = argmin119875119868119878119903= argmin[119892119900119901 cos (120572119894119899) Δ 119900119888119888119877119900 (120572) 1198601198881198751199051198892

119886119887

] (6)

where 119875119868119878119903 is the power received by the image sensor and 119875119905denotes the optical power transmitted by the LED

Most existing commercial cameras offer a low AoV Asa result the LOS components of neighboring LEDs do notreach inside the camerarsquosAoVMoreover asmentioned aboveintroducing RoI signaling techniques significantly reducesthe effect of the reflected components Thus OCC offers anexcellent SINR which is represented as

119878119868119873119877119900119888119888 = (120577119888119875119905119867119868119878119905119903)2sum119873119894=0 (120577119888119875119905119867119900119888119888119894119903 )2 + 119873119900119891119903

(7)

where 120577119888 denotes the optical-to-electrical conversion effi-ciency at the image sensor 119873119900 is the spectral density of the


noise power 119891119903 is the sampling rate of the camera 119873 isthe number of interfering transmitters and 119867119900119888119888119894119903 is the DCgain from these transmitters The channel capacity can beexpressed by the Shannon capacity formula [23] which is

119862119900119888119888 = 119891119903119882119904log2 (1 + 119878119868119873119877119900119888119888) (8)

where119882119904 represents the number of data symbols transmittedto the pixels within each image frame

23 LiFi Channel Model The NLOS part of the transmittedsignal is disregarded in terms of LiFi because our basebandmodulation bandwidth 119861 is 20 MHz which does not exceedthe maximum allowable value [16 39] Thus the LOS trans-mission model for LiFi is represented as

119867119875119863119905119903 = 119892119900119901119892119888119900119899 cos (120572119894119899) Δ 119897119894119891119894119877119900 (120572)1198601199011198892119886119887

(9)

where 119860119901 denotes the physical area of the PD sensitive tolight and 119892119888119900119899 is the gain of the optical concentrator whichis a function of the refractive index and field-of-view (FoV)of PDThe rectangular function Δ 119897119894119891119894 is expressed as

Δ 119897119894119891119894 = 0 120572119894119899 ge 120573119891119900V1 120572119894119899 lt 120573119891119900V (10)

where 120573119891119900V denotes the PD FoV The PD should receive acertain amount of power to generate a minimum electricalcurrent in order to decode the actual sent data bits Thethreshold power of LiFi is denoted as


119886119887

] (11)

where 119875119875119863119903 denotes the total amount of power received bythe PD LiFi uses an intensity based modulation scheme assuch LiFi is affected by the interference generated by neigh-boring LEDs and other background lights This interferenceultimately results in reducing the SINR to a great extentas LED infrastructures are commonly developed for indoorenvironments Several studies [16 40] have investigated theSINR in terms of LiFi which can be expressed as

119878119868119873119877119897119894119891119894 = ((120577119901radic119875119890119875119905) 119875119905119867119875119863119905119903 )2sum119873119894=0 ((120577119901radic119875119890119875119905) 119875119905119867119875119863119894119903 )2 + 119873119900119861

(12)

where 120577119901 is the optical-to-electrical conversion efficiency atthe PD and 119875119890 is the amount of electrical power convertedafter receiving the optical signals The LiFi channel capacitycan also be calculated from the Shannon capacity formulawhich is

119862119897119894119891119894 = 119861 log2 (1 + 119878119868119873119877119897119894119891119894) (13)

3 FL-Based Network Assignment

Inside the hybrid network the network is selected accordingto the type of service and quality that the user requires FL isdispensed to assign a particular user to a network Instead ofmaking decisions for choosing a network in a hybrid systemin terms of Boolean logic (only true or false values) the FL-based assignment considers truth values of variables rangingfrom0 to 1 [33 41ndash43]We apply theMamdani fuzzy inferencesystem to evaluate our proposed scheme this system includesthree principal steps fuzzification of input variables rulesevaluation and defuzzification

Fuzzification refers to the process of transforming thecrisp inputs into degrees of functional blocks through usingthe different types of fuzzifiers called membership func-tions A fuzzy set is graphically represented by membershipfunctions For example a triangular function is presented inFigure 3(a) and described as

120583 (119909 119886119879 119887119879) =

0 119909 le 119886119879 [119877119890119889 119897119894119899119890]119909 minus 119886119879119887119879 minus 119886119879 119886119879 le 119909 le 119887119879 [119861119897119906119890 119897119894119899119890]1 119909 ge 119887119879 [119866119903119890119890119899 119897119894119899119890]

(14)

where 119886119879 and 119887119879 are the breakpoints of the membershipfunctions and 119909 is a particular input

We considered four input variables to perform the net-work assignment mechanism data rate requirement SINRrequirement amount of instantaneous received power andLOS Euclidean distance between the access point (AP) andthe receiver The variables are chosen on the basis of appli-cation scenarios For example if a user wants to localize itsposition it will definitely need an excellent SINR rather thanhigh data rate to minimize the localization resolution On thecontrary both data rate and SINRmust be high for a real-timevideo call Moreover the instantaneous power significantlycontributes to determining the bit-error performance ofconnectivity In addition a low received power degrades theuserrsquos QoS level by increasing the outage probability to a greatextent On the other hand the maximum communicationdistance varies for different optical wireless systems anduser achieves satisfactory QoS when the communicationdistance is short A long distance between the LED andreceiver increases the interference for LiFi although OCCis less affected by interference In particular the maximumcommunication distance for LiFi is very short compared toOCC for stable communications

The membership functions are chosen on the basis ofseveral experiments involving the use of training data Thegrades of the membership functions are assigned accordingto the effect of variations in the value of a particular inputFigure 3(b) shows an illustration of the fuzzification of theSINR requirement of a specific user on the basis of servicetype and quality The procedure is characterized by four dif-ferent membership grades low average high and excellentThese grades are distributed from ndash10 to 60 dB As shown in


1

0

02

04

06

08

Ta Tb

(a)

05

0

1SINR (dB)

Area of higher membership degreeArea of lower membership degree

p q r s

AverageHighExcellent

Low

Membership grades

(b)

Figure 3 Fuzzification process (a) a generalized triangular function (b) SINR requirement

Figure 3(b) the four membership grades can be representedin a similar approach which is

119871119900119908 997888rarr 120583 (119909 119901 119902) 119909 ge 119901119860V119890119903119886119892119890 997888rarr

1 minus 120583 (119909 119901 119902) 119909 gt 119901120583 (119909 119902 119903) 119909 ge 119902

119867119894119892ℎ 997888rarr 1 minus 120583 (119909 119902 119903) 119909 gt 119902120583 (119909 119903 119904) 119909 ge 119903

119864119909119888119890119897119897119890119899119905 997888rarr 1 minus 120583 (119909 119903 119904) 119909 lt 119904

(15)

The chosen SINR values of the breakpoints are ndash10 1030 and 40 dB For example if a user requires an SINR ofaround 25 dB then the user will be categorized as ldquoaveragerdquo inthe fuzzification process Other inputs are fuzzified througha similar approach However the status of the membershipgrades is varied according to the numerical information ofthe input variables For example the data rate requirement isfuzzified through three membership grades low average andhigh

After fuzzifying the inputs different rules are used toevaluate the performance of the hybrid system [41] Theseifthen rules are generated by assigning a membership gradeto each of the input variables and a decision is made aftermultiplying (also can be referred to as ldquoandrdquo operation) therules For example if the data rate requirement is low theSINR requirement is excellent and the instantaneous receivepower is medium then the user will be connected via LiFi forthe shortest distance between the light source and receiver(or OCC for the highest distance) It is worth noting herethat the rules are comprehensive and are generated keepingthe nature and quality of the user requirements in mind Ingeneral rules are the guidelines generated according to the

membership functions and serve as a basis for why we choosea particular network in a specific kind of service scenario

The network assignment procedure is illustrated inFigure 4 The user must remain inside the LED cell in orderto get connected via LiFi or OCC However the connectionpossibility significantly depends on the FoV or AoV offeredby the PD or camera respectively Because the effects of theNLOS components on the optical signal are disregarded theLED must appear inside the coverage area of the receiverAfter getting a new network access request (NAR) from theuser the service type will be investigated The examinationon the input variables will be initiated immediately followingthe investigation Then the system will go through thefuzzification process described earlier

Subsequently the rules are employed and evaluated Thelast stage of the network assignment mechanism is the markallocation a process that is also referred to defuzzificationThe mark indicates the possibility of choosing a network inthe network assignment process Two separate outputs areconsidered for LiFi and OCC Both outputs are characterizedwith triangular membership functions We have consideredfive membership grades for each output to obtain a preciseresult in the network selection mechanism In this paperthe mark is termed as network assignment factor (NAF) anddenoted as 120599119897119894119891119894 and 120599119900119888119888 for LiFi and OCC respectively Wehave adopted CoG [33] method for defuzzification becauseit shows better performance results than the bisector-of-area(BoA)methodwhich is realized through several experimentson training data The NAF is provided as a crisp value by theCoG method which is represented as

For LiFi 120599119897119894119891119894 = int1

0119911120583119897 (119911) 119889119911

int10120583119897 (119911) 119889119911

For OCC 120599119900119888119888 = int1

0119911120583119888 (119911) 119889119911

int10120583119888 (119911) 119889119911

(16)


Start

New NAR

Detect service type

Analyze crisp input variables

Fuzzy inference systemEvaluate IF-THEN rules

Defuzzification

NAF examination

Accept to OCC Accept to LiFi

Data transmission and processing

User inside LED cell

Yes No

Yes

Yes

No

Allocate time resource to remaining users

Is lifi le occ

Figure 4 Admission strategy for a new network access request

where int10120583119897(119911)119889119911 indicates the total area of the region after

combining all the membership functions NAF values rangefrom 0 to 1 In fact a higher NAF increases the possibilityof choosing a network Thus when a network access isrequested by a new user the NAFs of both networks will becompared The network with the higher NAF will be chosenFor example if LiFi achieves an NAF of 06 for a new userwhereas OCC obtains 08 then the user will be connected toOCC instead of LiFi

When multiple users want to connect to the same APand RRS [34] a TDMA technique is considered Each user isallocated a particular time slot referred to as quantum timeto ensure fairness among all users If the process of serving theuser is not entirely executed within that time slot the processwill resume after completing all other processes in the queueFigure 5 illustrates an RRS scheduling process in which fourusers want to get access from the serving light source Theprocess for LiFi user-2 does not finish within the allocatedtime slot it gets connected again after the other time slotsallocated in the queue have been completed

User-2User-1 User-2 User-3 User-4

Quantum time

OCCLiFi

Job-1 Job-2

Figure 5 Example of RRS scheduling process

The user QoS is measured considering achievable userdata rate and SINR We develop a parameter referred asdemand satisfaction factor (DSF) to analyze theQoS of usersIf the user achieves a lower data rate or SINR than it requiresthe DSF will be decreased In general DSF is calculated onthe basis of time resource allocation to each user The DSF ofa particular user is represented as follows


119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)

120593119886119894120594119886119894120593119903119894120594119903119894 120582 lt 120590119894amp 120593119886119894 lt 120593119903119894amp 120594119886119894 lt 120594119903119894120593119886119894120594119886119894120593119903119894120594119903119894 120582 ge 120590119894amp 120593119886119894 lt 120593119903119894amp 120594119886119894 lt 120594119903119894120594119886119894120594119903119894 120582 ge 120590119894amp 120593119886119894 ge 120593119903119894amp 120594119886119894 lt 120594119903119894120593119886119894120593119903119894 120582 ge 120590119894amp 120593119886119894 lt 120593119903119894amp 120594119886119894 ge 1205941199031198941 120582 ge 120590119894amp 120593119886119894 ge 120593119903119894amp 120594119886119894 ge 120594119903119894

(17)

where 120593119886119894 and 120593119903119894 indicate the achievable and required datarate respectively and 120594119886119894 and 120594119903119894 indicate the achievable andrequired SINR respectively 120582 and 120590119894 represent the quantumtime and burst time of the user respectively 119899 indicatesthe total number of users waiting in queue at the particulartime and 119873119905 is the maximum number of users that can beconnected inside the LED cell

4 Link-Switching Strategy

It is already known that LiFi suffers from more interferencethan OCC This interference can originate from the LOScomponent of other light sources or other componentsreflected from painted walls or mirrors For simplicity weassume an indoor scenario in which a user can be connectedto several LEDs It is obvious that the user device will beaffected by the LOS component of the neighboring LED nearthe edge of the LED cell Thus if just under the LED cellthe user will suffer the least amount of interference and willreceive the best SINRTherefore the probability of allocationto the LiFi network will be high If the user appears to beconnected with OCC at that time the probability of link-switching to LiFi will also be high because the final goal ofnetwork allocation is increasing the user QoS as much aspossible In the same way if the user goes too close to theedge of the LED cell then the probability of switching froma LiFi to an OCC network will be high Figure 6 shows twoLED cells each having a diameter of ] If 120574 of the diameterof a specific LED cell is covered by a neighbor LED cell theprobability of user devices interfering with the neighbor LEDwithin an LED cell will be

119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)

where 120576 is the total number of neighbor LED cells inter-fering with the serving LED cell and 120591 is the total numberof user devices inside the cell Thus whenever the LOSdistance between the LED AP and the receiver changesthe link-switching probability of either network will alsobe changed according to the user service requirements Thenetwork assignment for the network switching request canbe performed in two ways LiFi-to-OCC and OCC-to-LiFiswitching

The link-switching can be implemented within either thesame LED AP or different APs Figure 7 shows the switchingpolicy for OCC-to-LiFi Initially the user communicates

using the OCC network Then the condition of the userwill be investigated ie whether the user is remainingstatic or roaming around the LED cells The LOS distancefrom the LED AP to the camera will change for everymicrosecond for the moving user Therefore there will bechance for the camera to receive power below119875119868119878119905ℎ In this casecommunication between the user and LEDAPwill terminateThe immediate received power will be compared with 119875119868119878119905ℎ and when the power exceeds the threshold value the LiFireceived powerwill be immediately comparedwith119875119875119863119905ℎ If thereceived power is higher than the threshold then the user willbe connected to LiFi However if the received power is alsobelow threshold the user will be connected to the adjacentAP and follow a newNAR strategy There is a high possibilityfor a static user to switch between service and quality require-ments For example the user can switch from 360p to 1080pvideo calling or can stop real-time communication andstart browsing For this reason whenever the user switchesbetween different services the NAF will be investigated IfNAF is found decreasing then it will be compared to that ofLiFi If LiFi offers a higher NAF than OCC then the user willbe switched to LiFi A similar strategy will be followed forLiFi-to-OCC switching which is shown in Figure 8

5 Network Switching Flow Process

In this section we propose a detailed network switchingflow mechanism for the hybrid system The flow procedureis generalized and applicable to either OCC-to-LiFi or LiFi-to-OCC switching The flow mechanism is illustrated inFigure 9

The switching flow mechanism is implemented through25 steps When the user device senses that the NAF of theserving receiver (SR) is decreasing (step-1) it sends a reportto the serving AP (SAP) it is connected to (step-2) TheSR then searches for new signals (step-3) and the SAP bywhich the user will be connected to the target receiver (TR)is selected (step-4)Then the preauthentication is checked bythe receiver with the target AP (TAP) (step-5) On the basisof the preauthentication and the NAF the SR investigatesthe signal quality Together the SAP and SR decide if aswitch to the TAP should be executed (step-6) The SAPinitiates the switching process by sending a request to theTAPvia a gateway (steps-7 and 8) Network assignment control(NAC) is initiated to specify the possibility of whether or notthe network can be assigned (step-9) Afterward the TAPresponds to the switching request (steps-10 and 11) Then a


Table 1 System parameters for the simulation

Transmitter parametersLED radius 5 cmTransmitted optical power 119875119905 10 WHalf-intensity radiation angleΨ12 60∘Gain of optical filter 119892119900119901 10

LiFi parametersPhysical area of PD 1 cm2

Gain of optical concentrator 119892119888119900119899 15Optical-to-electrical conversion efficiency 120577119901 053 AWOptical bandwidth 119861 20 MHzFoV 120573119891119900V 85∘

OCC parametersImage sensor size 6 times 4 (32 aspect ratio)Pixel edge length 120588 2 120583mFrame rate 119891119903 30 fpsFocal length 119891119900 6 mmOptical-to-electrical conversion efficiency 120577119888 051 AWAoV (diagonal) 120573119886119900V 60∘

O]

]

Figure 6 Illustration of two adjacent LED cells

new link is set up between the TAP and gateway (steps-12to 15) and eventually packet data are forwarded to the TAP(step-16) An optical channel is reestablished with the TAP(step-17) reconfigured (steps-18 to 20) and finally detachedfrom the SAP and synchronized with the TAP (step-21)The SR then sends a signal to the gateway indicating thecompletion of the switching mechanism and synchronizationwith the TAP (steps-22 and 23) Finally the optical linkbetween the former SAP and gateway is deleted (steps-24 and25) and the packets are sent to the TR via the TAP

6 Performance Evaluation

In this section the network assignment mechanism is sim-ulated considering the system parameters summarized inTable 1 The hybrid system can be implemented in indoorand outdoor environments OCC is particularly preferred in

daylight and both LiFi and OCC can be utilized during thenighttime We performed the simulations while consideringthe maximum communication distance of LiFi and OCCWhen the LOS distance is high OCC is slightly morepreferred than LiFi

Figures 10 and 11 show how theNAFs vary with increasingcommunication distance for both LiFi and OCCThe consid-ered fuzzy rules are arranged in Table 2 The simulations areparticularly based on the different service scenarios of usersFor example in case a user wants to localize its position theservice does not need a high data rate rather it requires a leastbit-error rate for precise localization This case is consideredin Scenario-A A user who wants to browse websites isreflected in Scenario D Scenarios B and C indicate high-quality voice and video calling users and Scenarios E and Freflect the standard quality

As shown in Figure 10 LiFi achieves an NAF higher than05 when the communication distance is kept within 6 min all cases The main reason that LiFi works in a limitedcommunication distance is because of the optical signalreceiving characteristics of PDs OCC provides a good NAFfor all cases except high-quality voice and video calling usersbecause of its data rate limitation which is shown in Figure 11

For mobility supporting characteristics of LiFi and OCCtechnologies our proposed hybrid system also ensures effi-cient switching between networks based on the servicescenarios The switching is very essential as the size of theLED cell is very small and our current indoor environmentis decorated with numerous LED infrastructures Link-switching is initiated whenever the receive power of theserving network falls below the threshold value Figure 12illustrates the power received by the users from differentdistances from LED AP

The link-switching probability of OCC and LiFi is illus-trated in Figure 13 The probability is measured considering


Table 2 Selected fuzzy rules for different scenarios

Scenarios Req data rate Req SINR Ins receive powerA Low Excellent MediumB Average High HighC High Excellent HighD Average Poor LowE Average Average HighF Average High High

Start

Switch to LiFi

Handover to adjacent AP and follow new NAR strategy

Continue with OCC

Yes

No

Yes

No

Yes

No Is NAF decreasing

Yes

No

Is userroaming

Is receive power decreasing

No

Yes

Yes

No

User communicates

via cameraFollow LiFi-to-OCC switching

strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ

Figure 7 OCC-to-LiFi link-switching strategy

an indoor scenario in which the diameter of the LED cell is10 m The link-switching probability is illustrated in termsof probability of user position inside the LED cell to receivehighest optical signal The highest position probability insidethe LED cell corresponds with a user situated at the center ofthe LED cell (represented by O in Figure 6) and the lowestprobability corresponds with a user located at the edge ofthe LED cell It can be seen in Figure 13 that a user hasa high probability of switching from LiFi-to-OCC when itremains near the LED cell origin However the probabilitydecreases whenever the user comes close to the LED cell ofthe neighboring LEDTheOCC-to-LiFi handover probability

attains the inverse situation because of the capability of thecamera to spatially separate the interfering element from theimage sensor

Figure 14 illustrates the outage probability of our pro-posed hybrid scheme We set the threshold of the LiFiSINR as 0 dB for the simulation We can clearly see thatthe outage probability is higher when the user moves awayfrom the AP in terms of using LiFi only However afterintegrating OCC and LiFi a clear improvement in outagepossibility can be observed The QoS performance of usersis presented in Figure 15 The average DSF is measuredassuming 016 personsmeter2 can be served inside the LED


Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD

Follow OCC-to-LiFi switching strategy

No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Figure 8 LiFi-to-OCC link-switching strategy

cell We also assume the number of users connected to OCCand LiFi in the hybrid infrastructure are same Althoughthe performance greatly depends on how much time isallocated to each user our proposed scheme demonstratesbetter QoS performance than the case when only LiFi ispresent

7 Conclusions

Next generation VLC networks will be exploited to achieve ahigher service quality for users in all kinds of environmentsOne of the main advantages of using VLC is that existinglighting infrastructures can be utilized to send data tousers LiFi is a OWC technology that offers a high datarate However it suffers from interferences when there aremultiple light sources and the interference originated fromthese sources eventually degrades the service quality UsingOCC the SINR can be significantly improved in all kindsof scenarios Thus the combination of high data rate andhigh SINR can be achieved by integrating OCC and LiFi Ahybrid OCC and LiFi architecture is proposed in this paper inwhich the network assignment for each user is based on FLBy using the FL concept optimality can be achieved with lesscomputational complexity After defuzzification each net-work generates a score called NAF which is utilized to assign

the appropriate network to a particular user Furthermore alink-switching mechanism based on FL is proposed and anetwork switching flow analysis is provided Performance isevaluated on the basis of different practical scenarios and thisevaluation includes switching and outage probability analysisinside the LED cell The user QoS is also analyzed and theresults of this analysis demonstrate the importance of ourproposed scheme

8 Future Research

Currently researchers are working on enabling the coexis-tence of RF and OWC to achieve high-data-rate output withimproved coverage The coexistence of different OWC tech-nologies for the same kind of AP can be utilized to achievea better service quality for users The implementation of ourproposed hybrid system indifferent application scenarios willbe a momentous topic in future OWC related research whichwill include testing our systemrsquos optimality with respect toother future homogenous hybrid infrastructures

Data Availability

The data used to support the findings of this study areavailable from the corresponding author upon request


SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC

16 Forwarding of packet data

12 New link setup request

14 Link setup response

17 Physical channel reconfiguration

15 Transport bearer setup

20 Physical channel reconfiguration complete

23 HO complete

24 Optical link deletionrequest

25 Optical link deletion response

26 Transport bearer release

PacketPacket

22 HO complete

21 Detached from serving AP and synchronized to target AP

1 NAF is going down

7 HO required



complete

2 Measurement report

5 Pre-authentication to target AP

4 Selection of target AP for handover

3 Searches for new signals

11 HO response

TR

13 Communication link establishment

6 Decision to perform handover to target network

Figure 9 Network switching flow strategy


00

02

04

06

08

10

NA

F

2 4 6 8 10 12 14LOS distance between user and AP (m)

Scenarios A B C

D E F

Figure 10 NAF variation using LiFi with increasing distance between user and LED AP

NA

F

2 4 6 8 10 12 1400

02

04

06

08

10

LOS distance between user and AP (m)

Scenarios A B C

D E F

Figure 11 NAF variation using OCC with increasing distance between user and LED AP


OCCLiFi

minus90minus80minus70minus60minus50minus40minus30minus20minus10

0102030

Rece

ived

Pow

er (d

Bm)

15 20 25 30 35 40 45 5010Horizontal distance between receiver and LED AP (m)

Figure 12 Distribution of received power for LiFi and OCC

00

02

04

06

08

10

00 02 04 06 08 10

Probability of user position inside LED cell

OCC-to-LiFiLiFi-to-OCC

Switc

hing

pro

babi

lity

Figure 13 Link-switching probability analysis

Disclosure

This article is an extended version of a paper presentedin the International Conference on Ubiquitous and FutureNetworks (ICUFN 2018) Prague Czech Republic July 2018

Conflicts of Interest

The authors do not have any conflicts of interest

Acknowledgments

Thisworkwas supported by Institute for Informationamp Com-munications Technology Promotion (IITP) grant funded by

LiFi onlyHybrid system

10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y

4 6 8 102LOS distance between AP and receiver

Figure 14 Comparison of outage probability

LiFi onlyOCC amp LiFi integration

00

02

04

06

08

10Av

erag

e DSF

4 6 8 10 122Number of users inside LED cell

Figure 15 AverageDSF comparison formultiple users served by thesame LED AP

the Korea Government (MSIT) (no 2017-0-00824 Develop-ment of Intelligent and Hybrid OCC-LiFi Systems for NextGeneration Optical Wireless Communications)

References

[1] Z Ghassemlooy S Arnon M Uysal Z Xu and J ChengldquoEmerging Optical Wireless Communications-Advances andChallengesrdquo IEEE Journal on SelectedAreas in Communicationsvol 33 no 9 pp 1738ndash1749 2015

[2] P H Pathak X Feng P Hu and P Mohapatra ldquoVisible LightCommunication Networking and Sensing A Survey Potentialand Challengesrdquo IEEE Communications Surveys amp Tutorialsvol 17 no 4 pp 2047ndash2077 2015


[3] M Z Chowdhury M T Hossan A Islam and Y M Jang ldquoAComparative Survey of Optical Wireless Technologies Archi-tectures and Applicationsrdquo IEEE Access vol 6 pp 9819ndash98402018

[4] H Chen H P A Van Den Boom E Tangdiongga and T Koo-nen ldquo30-Gbs bidirectional transparent optical transmissionwith an MMF access and an indoor optical wireless linkrdquo IEEEPhotonics Technology Letters vol 24 no 7 pp 572ndash574 2012

[5] D K Borah A C Boucouvalas C C Davis S Hranilovic andK Yiannopoulos ldquoA review of communication-oriented opticalwireless systemsrdquo EURASIP Journal on Wireless Communica-tions and Networking vol 91 pp 1ndash28 2012

[6] H Elgala RMesleh andHHaas ldquoIndoor optical wireless com-munication Potential and state-of-the-artrdquo IEEE Communica-tions Magazine vol 49 no 9 pp 56ndash62 2011

[7] D Karunatilaka F Zafar V Kalavally and R Parthiban ldquoLEDbased indoor visible light communications state of the artrdquoIEEE Communications Surveys amp Tutorials vol 17 no 3 pp1649ndash1678 2015

[8] R Zhang JWang ZWang Z Xu C Zhao and L Hanzo ldquoVis-ible light communications in heterogeneous networks Pavingthe way for user-centric designrdquo IEEEWireless CommunicationsMagazine vol 22 no 2 pp 8ndash16 2015

[9] A C Boucouvalas P Chatzimisios Z Ghassemlooy M Uysaland K Yiannopoulos ldquoStandards for indoor Optical WirelessCommunicationsrdquo IEEECommunicationsMagazine vol 53 no3 pp 24ndash31 2015

[10] M Leba S Riurean andA Lonica ldquoLiFi -Thepath to anewwayof communicationrdquo inProceedings of the 12th IberianConferenceon Information Systems and Technologies CISTI 2017 PortugalJune 2017

[11] Y Perwej ldquoThe Next Generation of Wireless CommunicationUsing Li-Fi (Light Fidelity) Technologyrdquo Computer Networksvol 4 no 1 pp 20ndash29 2017

[12] Y Wang X Wu and H Haas ldquoLoad Balancing Game withShadowing Effect for Indoor Hybrid LiFiRF Networksrdquo IEEETransactions on Wireless Communications vol 16 no 4 pp2366ndash2378 2017

[13] M Kashef M Ismail M Abdallah K A Qaraqe and E Ser-pedin ldquoEnergy efficient resource allocation for mixed RFVLCheterogeneous wireless networksrdquo IEEE Journal on SelectedAreas in Communications vol 34 no 4 pp 883ndash893 2016

[14] F Jin R Zhang and L Hanzo ldquoResource allocation underdelay-guarantee constraints for heterogeneous visible-light andRF femtocellrdquo IEEE Transactions on Wireless Communicationsvol 14 no 2 pp 1020ndash1034 2015

[15] Y Wang D A Basnayaka X Wu and H Haas ldquoOptimizationof Load Balancing in Hybrid LiFiRF Networksrdquo IEEE Transac-tions on Communications vol 65 no 4 pp 1708ndash1720 2017

[16] YWang andHHaas ldquoDynamic LoadBalancingwithHandoverin Hybrid Li-Fi and Wi-Fi Networksrdquo Journal of LightwaveTechnology vol 33 no 22 pp 4671ndash4682 2015

[17] M Ayyash H Elgala A Khreishah et al ldquoCoexistence of WiFiand LiFi toward 5G concepts opportunities and challengesrdquoIEEE Communications Magazine vol 54 no 2 pp 64ndash71 2016

[18] G Pan J Ye andZDing ldquoSecureHybridVLC-RF SystemswithLight Energy Harvestingrdquo IEEE Transactions on Communica-tions vol 65 no 10 pp 4348ndash4359 2017

[19] S Shao and A Khreishah ldquoDelay Analysis of Unsaturated Het-erogeneous Omnidirectional-Directional Small Cell WirelessNetworksTheCase of RF-VLCCoexistencerdquo IEEETransactionsonWireless Communications vol 15 no 12 pp 8406ndash8421 2016

[20] H-S Kim D-H Kwon S-H Yang Y-H Son and S-K HanldquoChannel assignment technique for RF frequency reuse in CA-VLC-based accurate optical indoor localizationrdquo Journal ofLightwave Technology vol 32 no 14 pp 2544ndash2555 2014

[21] P Luo Z Ghassemlooy H Le Minh X Tang and H-M TsaildquoUndersampled phase shift ON-OFF keying for camera com-municationrdquo in Proceedings of the 6th International Conferenceon Wireless Communications and Signal Processing (WCSP rsquo14)pp 1ndash6 IEEE Hefei China October 2014

[22] T Yamazato I Takai H Okada et al ldquoImage-sensor-basedvisible light communication for automotive applicationsrdquo IEEECommunications Magazine vol 52 no 7 pp 88ndash97 2014

[23] T Nguyen A Islam T Hossan and Y M Jang ldquoCurrent statusand performance analysis of optical camera communicationtechnologies for 5G networksrdquo IEEE Access vol 5 pp 4574ndash4594 2017

[24] Y Goto I Takai T Yamazato et al ldquoA New Automotive VLCSystem Using Optical Communication Image Sensorrdquo IEEEPhotonics Journal vol 8 no 3 pp 1ndash17 2016

[25] R D Roberts ldquoUndersampled frequency shift ON-OFF key-ing (UFSOOK) for camera communications (CamCom)rdquo inProceedings of the 22nd Wireless and Optical CommunicationsConference WOCC rsquo13 pp 645ndash648 China May 2013

[26] I Takai S Ito K Yasutomi K Kagawa M Andoh andS Kawahito ldquoLED and CMOS image sensor based opticalwireless communication system for automotive applicationsrdquoIEEE Photonics Journal vol 5 no 5 2013

[27] M T Hossan M Z Chowdhury A Islam and Y M JangldquoA Novel Indoor Mobile Localization System Based on Opti-cal Camera Communicationrdquo Wireless Communications andMobile Computing vol 2018 17 pages 2018

[28] B Lin Z Ghassemlooy C Lin X Tang Y Li and S ZhangldquoAn Indoor Visible Light Positioning System Based on OpticalCamera Communicationsrdquo IEEE Photonics Technology Lettersvol 29 no 7 pp 579ndash582 2017

[29] T Nguyen A Islam T Yamazato and Y M Jang ldquoTechnicalIssues on IEEE 802157m Image Sensor Communication Stan-dardizationrdquo IEEECommunicationsMagazine vol 56 no 2 pp213ndash218 2018

[30] I Takai T Harada M Andoh K Yasutomi K Kagawa andS Kawahito ldquoOptical vehicle-to-vehicle communication systemusing LED transmitter and camera receiverrdquo IEEE PhotonicsJournal vol 6 no 5 pp 1ndash14 2014

[31] T Yamazato M Kinoshita S Arai et al ldquoVehicle Motion andPixel Illumination Modeling for Image Sensor Based VisibleLight Communicationrdquo IEEE Journal on Selected Areas inCommunications vol 33 no 9 pp 1793ndash1805 2015

[32] P Ji H-M Tsai C Wang and F-Q Liu ldquoVehicular visible lightcommunications with led taillight and rolling shutter camerardquoin Proceedings of the IEEE 79th Vehicular Technology Conference(VTC rsquo14) pp 1ndash6 Seoul Republic of Korea May 2014

[33] T J Ross Fuzzy Logic with Engineering Applications JohnWileyamp Sons Ltd 3rd edition 2011

[34] M Kawser ldquoPerformance Comparison between Round RobinandProportional Fair Scheduling Methods for LTErdquo Interna-tional Journal of Information and Electronics Engineering vol2 no 5 pp 678ndash681 2012

[35] P Luo M Zhang Z Ghassemlooy S Zvanovec S Feng and PZhang ldquoUndersampled-BasedModulation Schemes for OpticalCamera Communicationsrdquo IEEE Communications Magazinevol 56 no 2 pp 204ndash212 2018


[36] R D Roberts ldquoA MIMO protocol for camera communications(CamCom) using undersampled frequency shift ON-OFF key-ing (UFSOOK)rdquo in Proceedings of the IEEE Globecom Work-shops (GC Wkshps rsquo13) pp 1052ndash1057 Atlanta GA December2013

[37] P Luo et al ldquoExperimental demonstration of RGB LED-basedoptical camera communicationsrdquo IEEE Photonics Journal vol 7no 5 pp 1ndash12 2015

[38] J M Kahn and J R Barry ldquoWireless infrared communicationsrdquoProceedings of the IEEE vol 85 no 2 pp 265ndash298 1997

[39] V Jungnickel V Pohl S Nonnig and C VonHelmolt ldquoA phys-ical model of the wireless infrared communication channelrdquoIEEE Journal on Selected Areas in Communications vol 20 no3 pp 631ndash640 2002

[40] X Wu M Safari and H Haas ldquoAccess Point Selection forHybrid Li-Fi and Wi-Fi Networksrdquo IEEE Transactions on Com-munications vol 65 no 12 pp 5375ndash5385 2017

[41] M Kaya andR Alhajj ldquoUtilizing genetic algorithms to optimizemembership functions for fuzzy weighted association rulesminingrdquo Applied Intelligence vol 24 no 1 pp 7ndash15 2006

[42] T Bouali and S Senouci ldquoA fuzzy logic-based communicationmedium selection for QoS preservation in vehicular networksrdquoin Proceedings of the IEEE International Conference on Commu-nications (ICC rsquo16) pp 1ndash6 Kuala Lumpur Malaysia May 2016

[43] A I Aziz S Rizvi and N M Saad ldquoFuzzy logic based verticalhandover algorithmbetween LTE andWLANrdquo inProceedings ofthe International Conference on Intelligent andAdvanced Systems(ICIAS rsquo10) pp 1ndash4 IEEE Kuala Lumpur Malaysia June 2010

International Journal of

AerospaceEngineeringHindawiwwwhindawicom Volume 2018

RoboticsJournal of

Hindawiwwwhindawicom Volume 2018


Active and Passive Electronic Components

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

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Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawiwwwhindawicom

Volume 2018

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

Control Scienceand Engineering

Journal of



Journal ofEngineeringVolume 2018

SensorsJournal of



RotatingMachinery


Modelling ampSimulationin EngineeringHindawiwwwhindawicom Volume 2018


Chemical EngineeringInternational Journal of Antennas and

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Navigation and Observation


Hindawi

wwwhindawicom Volume 2018

Advances in

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Submit your manuscripts atwwwhindawicom


However LiFi cannot be efficiently utilized in daylightbecause it suffers from extensive interference generated bysunlight [3] In indoor environments it can suffer from thesame problem resulting from neighboring lighting infras-tructures LiFi has a low signal-to-interference-plus-noiseratio (SINR) because it is heavily affected by the inter-ferences generated by adjacent light sources In additionthe communication distance that can be obtained usingLiFi is comparatively short with respect to other existingtechnologies These limitations inspire further research onthe optimum potentiality of LiFi in practical environments

Optical camera communication (OCC) is a recentlyintroduced VLC technique that uses an image sensor toreceive optical signals [21ndash26] The exponential growthin camera-mounted smart devices has enabled OCC tobe utilized in innovative application scenarios such asindooroutdoor positioning [27 28] localized advertising[29] digital signage and vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communications [30ndash32] OCC hasadded significant user flexibility with the use of smartphonecameras to receive data from LEDs Furthermore OCCis highly stable in terms of variations in communicationdistance Because of the limited angle-of-view (AoV) ofcameras OCC is less affected by interferences generated fromneighboring LEDsHowever similar to LiFi OCC has severallimitations For example because of the meager samplingrates of current commercial cameras OCC offers a low datarate which particularly decreases the user QoS

Until now a hybrid OCC and LiFi model had not beendeveloped In this study a hybrid networking architectureintegrating OCC and LiFi is proposed to enhance the userQoS The network is assigned to users through utilizationof fuzzy logic (FL) FL is a convenient approach to mapan input to an output and is provided on the basis ofseveral truth scores ranging from 0 to 1 [33] This method isflexible and intuitive without far-reaching complexity whichare characteristics that lead us to choose this approachWe propose a new network assignment mechanism insidethe LED cell (the entire coverage area of the LED) forusers Fuzzy inputs are chosen using the parameters thatdetermine the quality of both networks The fuzzy rules aregenerated by considering real-world application scenariosof users The center-of-gravity (CoG) method is used todefuzzify the inputs and obtain mark allocations for eachuser Furthermore we develop a FL-based vertical link-switching mechanism between the networking layers asboth of the networks support user mobility We brieflydiscuss the switching probability and corresponding networkswitching flow analysis of the hybrid system Round-robinscheduling (RRS) [34] an existing time-division multipleaccess (TDMA) approach is adopted to ensure fairness inresource allocation among users

The remainder of the paper is organized as followsSection 2 provides a system overview and an analysis onchannel parameters which includes theoretical representa-tions of SINR for both technologies The FL-based networkassignment mechanism including a discussion on user QoSis explained in Section 3 Sections 4 and 5 describe the link-switching strategy and the network switching flow process

respectively The performance of the assignment mechanismis evaluated in Section 6 which also includes a discussionof the outage probability and QoS performance A briefsummary of our work is provided in Section 7 FinallySection 8 presents future research possibilities related to ourproposed hybrid infrastructure

2 System Overview

21 Hybrid System Architecture In this study a hybridOCCLiFi networking layer is considered Taking usermobil-ity into account this hybrid system can serve multiple usersTherefore the hybrid system is suitable for any roamingor stationary user A particular LED is configured by twoparallel LED-driving circuitries Although both technologiesuse the same optical spectrum no interference will begenerated because the TDMA based RRSmethod is exploitedto allocate time resources when there are multiple usersA generalized block diagram of our proposed architectureis shown in Figure 1 The PD can receive high-rate LEDflickering whereas a camera cannot Current commercialcameras are configured with low frame rates (in most cases30ndash50 frames per second) This configuration particularlyreduces the modulation bandwidth of OCC [35 36] It is alsoworth noting that the LEDflickering must not be observed byhuman eyes (equivalent to a threshold of approximately 100Hz [37])

22 OCC Channel Model For a VLC system the route foroptical signal transmission has two components line-of-sight (LOS) and non-line-of-sight (NLOS) Because of thenature of camera pixels region-of-interest (RoI) mechanismsare applied for OCC by which the reflection componentof the transmitted signal is spatially separated from theLOS component [23] An indoor hybrid system with thetransmitter and receiver presented at Tx and Rx respectivelyis illustrated in Figure 2 The LED cell represents the entirecoverage area of the LED

The LOS channel for optical signal transmission is mod-eled by Lambertian radiant intensity which is represented bythe following equation [38]

119877119900 (120572) = (119898119897 + 1) cos119898119897 (120572119894119903)2120587 (1)

where 120572119894119903 signifies the angle of irradiance of the LED 119898119897 isthe Lambertian emission index which originates from theradiation angle Ψ12 called the radiation semiangle of theLED119898119897 is defined as

119898119897 = minuslogcosΨ122 (2)

We assume that the Euclidean distance between Tx andRx is 119889119886119887 which is calculated from the horizontal distance119889119887119909 and the vertical distance 119889119886ℎ (119889119886119887 = radic1198892119886ℎ + 1198892119887119909) Theoverall DC channel gain for OCC is formulated as [12]

119867119868119878119905119903 = 119892119900119901 cos (120572119894119899) Δ 119900119888119888119877119900 (120572)1198601198881198892119886119887 (3)


Input data


AD

Output data

AmplificationPD

Framesampling


LED


Demodulator

Demodulator

Decoder

ImageSensor



LED

LiFi dongle


Smartphone camera

Gateway dbx

daℎ

minus ir

info

dab

２Ｒ

ao

４Ｒ

LED cell



Δ 119900119888119888 = 0 120572119894119899 ge 120573119886119900V1 120572119894119899 lt 120573119886119900V (4)


119860119888 = 119860 119897119891119900212058821198892119886119887

(5)





119886119887

] (6)



119878119868119873119877119900119888119888 = (120577119888119875119905119867119868119878119905119903)2sum119873119894=0 (120577119888119875119905119867119900119888119888119894119903 )2 + 119873119900119891119903

(7)




119862119900119888119888 = 119891119903119882119904log2 (1 + 119878119868119873119877119900119888119888) (8)



119867119875119863119905119903 = 119892119900119901119892119888119900119899 cos (120572119894119899) Δ 119897119894119891119894119877119900 (120572)1198601199011198892119886119887

(9)


Δ 119897119894119891119894 = 0 120572119894119899 ge 120573119891119900V1 120572119894119899 lt 120573119891119900V (10)



119886119887

] (11)


119878119868119873119877119897119894119891119894 = ((120577119901radic119875119890119875119905) 119875119905119867119875119863119905119903 )2sum119873119894=0 ((120577119901radic119875119890119875119905) 119875119905119867119875119863119894119903 )2 + 119873119900119861

(12)


119862119897119894119891119894 = 119861 log2 (1 + 119878119868119873119877119897119894119891119894) (13)




120583 (119909 119886119879 119887119879) =


(14)





1

0

02

04

06

08

Ta Tb

(a)

05

0

1SINR (dB)


p q r s


Low

Membership grades

(b)



119871119900119908 997888rarr 120583 (119909 119901 119902) 119909 ge 119901119860V119890119903119886119892119890 997888rarr

1 minus 120583 (119909 119901 119902) 119909 gt 119901120583 (119909 119902 119903) 119909 ge 119902

119867119894119892ℎ 997888rarr 1 minus 120583 (119909 119902 119903) 119909 gt 119902120583 (119909 119903 119904) 119909 ge 119903

119864119909119888119890119897119897119890119899119905 997888rarr 1 minus 120583 (119909 119903 119904) 119909 lt 119904

(15)






For LiFi 120599119897119894119891119894 = int1

0119911120583119897 (119911) 119889119911

int10120583119897 (119911) 119889119911

For OCC 120599119900119888119888 = int1

0119911120583119888 (119911) 119889119911

int10120583119888 (119911) 119889119911

(16)


Start

New NAR

Detect service type



Defuzzification

NAF examination




Yes No

Yes

Yes

No


Is lifi le occ






Quantum time

OCCLiFi

Job-1 Job-2




119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)


(17)




119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)













O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



Input data


AD

Output data

AmplificationPD

Framesampling


LED


Demodulator

Demodulator

Decoder

ImageSensor



LED

LiFi dongle


Smartphone camera

Gateway dbx

daℎ

minus ir

info

dab

２Ｒ

ao

４Ｒ

LED cell



Δ 119900119888119888 = 0 120572119894119899 ge 120573119886119900V1 120572119894119899 lt 120573119886119900V (4)


119860119888 = 119860 119897119891119900212058821198892119886119887

(5)





119886119887

] (6)



119878119868119873119877119900119888119888 = (120577119888119875119905119867119868119878119905119903)2sum119873119894=0 (120577119888119875119905119867119900119888119888119894119903 )2 + 119873119900119891119903

(7)




119862119900119888119888 = 119891119903119882119904log2 (1 + 119878119868119873119877119900119888119888) (8)



119867119875119863119905119903 = 119892119900119901119892119888119900119899 cos (120572119894119899) Δ 119897119894119891119894119877119900 (120572)1198601199011198892119886119887

(9)


Δ 119897119894119891119894 = 0 120572119894119899 ge 120573119891119900V1 120572119894119899 lt 120573119891119900V (10)



119886119887

] (11)


119878119868119873119877119897119894119891119894 = ((120577119901radic119875119890119875119905) 119875119905119867119875119863119905119903 )2sum119873119894=0 ((120577119901radic119875119890119875119905) 119875119905119867119875119863119894119903 )2 + 119873119900119861

(12)


119862119897119894119891119894 = 119861 log2 (1 + 119878119868119873119877119897119894119891119894) (13)




120583 (119909 119886119879 119887119879) =


(14)





1

0

02

04

06

08

Ta Tb

(a)

05

0

1SINR (dB)


p q r s


Low

Membership grades

(b)



119871119900119908 997888rarr 120583 (119909 119901 119902) 119909 ge 119901119860V119890119903119886119892119890 997888rarr

1 minus 120583 (119909 119901 119902) 119909 gt 119901120583 (119909 119902 119903) 119909 ge 119902

119867119894119892ℎ 997888rarr 1 minus 120583 (119909 119902 119903) 119909 gt 119902120583 (119909 119903 119904) 119909 ge 119903

119864119909119888119890119897119897119890119899119905 997888rarr 1 minus 120583 (119909 119903 119904) 119909 lt 119904

(15)






For LiFi 120599119897119894119891119894 = int1

0119911120583119897 (119911) 119889119911

int10120583119897 (119911) 119889119911

For OCC 120599119900119888119888 = int1

0119911120583119888 (119911) 119889119911

int10120583119888 (119911) 119889119911

(16)


Start

New NAR

Detect service type



Defuzzification

NAF examination




Yes No

Yes

Yes

No


Is lifi le occ






Quantum time

OCCLiFi

Job-1 Job-2




119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)


(17)




119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)













O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




119862119900119888119888 = 119891119903119882119904log2 (1 + 119878119868119873119877119900119888119888) (8)



119867119875119863119905119903 = 119892119900119901119892119888119900119899 cos (120572119894119899) Δ 119897119894119891119894119877119900 (120572)1198601199011198892119886119887

(9)


Δ 119897119894119891119894 = 0 120572119894119899 ge 120573119891119900V1 120572119894119899 lt 120573119891119900V (10)



119886119887

] (11)


119878119868119873119877119897119894119891119894 = ((120577119901radic119875119890119875119905) 119875119905119867119875119863119905119903 )2sum119873119894=0 ((120577119901radic119875119890119875119905) 119875119905119867119875119863119894119903 )2 + 119873119900119861

(12)


119862119897119894119891119894 = 119861 log2 (1 + 119878119868119873119877119897119894119891119894) (13)




120583 (119909 119886119879 119887119879) =


(14)





1

0

02

04

06

08

Ta Tb

(a)

05

0

1SINR (dB)


p q r s


Low

Membership grades

(b)



119871119900119908 997888rarr 120583 (119909 119901 119902) 119909 ge 119901119860V119890119903119886119892119890 997888rarr

1 minus 120583 (119909 119901 119902) 119909 gt 119901120583 (119909 119902 119903) 119909 ge 119902

119867119894119892ℎ 997888rarr 1 minus 120583 (119909 119902 119903) 119909 gt 119902120583 (119909 119903 119904) 119909 ge 119903

119864119909119888119890119897119897119890119899119905 997888rarr 1 minus 120583 (119909 119903 119904) 119909 lt 119904

(15)






For LiFi 120599119897119894119891119894 = int1

0119911120583119897 (119911) 119889119911

int10120583119897 (119911) 119889119911

For OCC 120599119900119888119888 = int1

0119911120583119888 (119911) 119889119911

int10120583119888 (119911) 119889119911

(16)


Start

New NAR

Detect service type



Defuzzification

NAF examination




Yes No

Yes

Yes

No


Is lifi le occ






Quantum time

OCCLiFi

Job-1 Job-2




119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)


(17)




119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)













O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



1

0

02

04

06

08

Ta Tb

(a)

05

0

1SINR (dB)


p q r s


Low

Membership grades

(b)



119871119900119908 997888rarr 120583 (119909 119901 119902) 119909 ge 119901119860V119890119903119886119892119890 997888rarr

1 minus 120583 (119909 119901 119902) 119909 gt 119901120583 (119909 119902 119903) 119909 ge 119902

119867119894119892ℎ 997888rarr 1 minus 120583 (119909 119902 119903) 119909 gt 119902120583 (119909 119903 119904) 119909 ge 119903

119864119909119888119890119897119897119890119899119905 997888rarr 1 minus 120583 (119909 119903 119904) 119909 lt 119904

(15)






For LiFi 120599119897119894119891119894 = int1

0119911120583119897 (119911) 119889119911

int10120583119897 (119911) 119889119911

For OCC 120599119900119888119888 = int1

0119911120583119888 (119911) 119889119911

int10120583119888 (119911) 119889119911

(16)


Start

New NAR

Detect service type



Defuzzification

NAF examination




Yes No

Yes

Yes

No


Is lifi le occ






Quantum time

OCCLiFi

Job-1 Job-2




119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)


(17)




119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)













O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



Start

New NAR

Detect service type



Defuzzification

NAF examination




Yes No

Yes

Yes

No


Is lifi le occ






Quantum time

OCCLiFi

Job-1 Job-2




119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)


(17)




119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)













O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



119863119878119865 =

(1 minus 119899119873119905)(

120582120590119894)


(17)




119875119895 =120591sum119895=1

[[[2120576int]2(]minus2120574119895])2

radic]2 minus 41199112119889119911120591120587]2 ]]

](18)













O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia








O]

]













Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia





Start

Switch to LiFi


Continue with OCC

Yes

No

Yes

No

Yes


Yes

No

Is userroaming


No

Yes

Yes

No

User communicates


strategyNo

Yes

PISr gt PIS

tℎ

PPDr gt PPD

tℎ

Is lifi le occ






Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



Start

Switch to OCC


Continue with LiFi

Yes

No

Yes

No

Yes

No

Is NAF decreasing

Yes

No

Is user static


No

Yes

Yes

User communicates

via PD


No

Yes

No

Is lifi lt occ

PISr gt PIS

tℎ

PPDr gt PPD

tℎ



7 Conclusions



8 Future Research


Data Availability



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



SR TAP

8 HO request

SAP

10 HO response

Gateway

9 NAC







23 HO complete




PacketPacket

22 HO complete


1 NAF is going down

7 HO required



complete





11 HO response

TR





00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



00

02

04

06

08

10

NA

F


Scenarios A B C

D E F


NA

F

2 4 6 8 10 12 1400

02

04

06

08

10


Scenarios A B C

D E F



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia



OCCLiFi


0102030

Rece

ived

Pow

er (d

Bm)



00

02

04

06

08

10

00 02 04 06 08 10



Switc

hing

pro

babi

lity


Disclosure




Acknowledgments



10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Out

age p

roba

bilit

y




00

02

04

06

08

10Av

erag

e DSF




References
















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia















































RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia













RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia




RoboticsJournal of




VLSI Design



Shock and Vibration







Journal of



Volume 2018



Volume 2018


Journal of




SensorsJournal of



RotatingMachinery





Propagation






Hindawi


Advances in

Multimedia


Documents

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