Patent Publication Number: US-2021184820-A1

Title: System and method for managing interference in li-fi communication networks

Description:
TECHNICAL FIELD 
     This disclosure relates generally to Light Fidelity (Li-Fi) communication networks, and more particularly to a system and method for managing interference in Li-Fi communication networks. 
     BACKGROUND 
     The demand for wireless data communication is increasing at a very high rate, To keep up with this growing demand, the available Radio Frequency (RF) spectrum of below 10 GHz may not be sufficient. As an alternative, Optical Wireless Communication (OWC) involves communication over a light channel by a transmit-receive (transceiver) pair. The transceiver pair can transmit information using a Light Emitting Diode (LED) and receive information using a light sensor, such as, a photo diode or a camera. In Li-Fi, as defined in the IEEE standard 802.15.7, the transmitter transmits information using a single LED and the transmit information can be coded using various modulation techniques like On-Off Keying (OOK), Pulse Position Modulation (PPM), Color Shift Keying (CSK). The receiver side includes a photo detector to receive and decode the information. 
     The current OWC systems (for example, Li-Fi) lack the mechanism to overcome the interference caused by adjacent access points/transmit sources modulated using white light (single carrier). In the Li-Fi standard 802.15-7, under the VLC cell design and mobility support, the standard talks about the logical movement of a device from one cell to another, due to either interference or deliberate switching. The standard does not mention how to stay in the interference region and still be able to receive the transmit data. It does state about the interference caused by the ambient light but not due to the overlapping access points. The standard also talks about the beacon frame as a part of the super-frame used to discover the new devices that have come into the vicinity of the access points. However, there is no existing mechanism to transmit this beacon to discover the devices within the interference region. 
     When a user moves from one access point to another, the user connectivity persists as long as the user stays in the vicinity of the modulated light. If there is a region where modulated lights from adjacent access points interfere, the user will not be able to receive data in this interference region. In the current implementation of the OWC systems, there is no mechanism to overcome the interference caused by the overlapping access points, which are white light modulated using On-Off keying. There is no method to detect the physical cell IDs of the access points associated to the devices in the interference region. Interference management and multi-access in the overlapping region remains a key challenge in the OWC systems, where the mobility of a user is hindered by the interference of the overlapping access points in the vicinity. 
     SUMMARY 
     In one embodiment, a method for managing interference between a set of Light Fidelity (Li-Fi) access points in a Li-Fi communication network is disclosed. In one example, the method may include receiving, by an interference management device, a plurality of uplink data frames sent by a User Equipment (UE). Each of the plurality of uplink data frames includes a response to an associated downlink test frame received from an associated Li-Fi access point within the set of Li-Fi access points. The response includes one of an Acknowledgement (ACK) and a Negative Acknowledgment (NACK) for the associated downlink test frame and a Channel Quality Indication (CQI) for the associated Li-Fi access point based on the associated downlink test frame. The method may further include detecting, by the interference management device, presence of the UE in an interference region of the set of Li-Fi access points, based on presence of at least one NACK in at least one of the plurality of uplink frames received from the set of Li-Fi access points. The method may further include attaching, by the interference management device, the UE with a first Li-Fi access point from the set of Li-Fi access points. A CQI associated with the first Li-Fi access point is highest amongst the set of Li-Fi access points. The method may further include scheduling, by the interference management device, data transmission from the set of Li-Fi access points in a mutually exclusive time slot. The UE accepts data received from the attached Li-Fi access point and drops data received from remaining set of Li-Fi access points. The remaining set of Li-Fi access points does not include the first Li-Fi access point. 
     In another embodiment, a system for managing interference in a Li-Fi communication network is disclosed. In one example, the system may include a set of Li-Fi access points, a plurality of UEs, a processor, and a computer-readable medium communicatively coupled to the processor. The computer-readable medium may store processor instructions, which when executed by the processor, may cause the processor to receive a plurality of uplink data frames sent by a UE. Each of the plurality of uplink data frames includes a response to an associated downlink test frame received from an associated Li-Fi access point within the set of Li-Fi access points. The response includes one of an ACK and a NACK for the associated downlink test frame and a CQI for the associated Li-Fi access point based on the associated downlink test frame. The stored processor-executable instructions on execution, may further cause the processor to detect presence of the UE in an interference region of the set of Li-Fi access points, based on presence of at least one NACK in at least one of the plurality of uplink frames received from the set of Li-Fi access points. The stored processor-executable instructions on execution, may further cause the processor to attach the UE with a first Li-Fi access point from the set of Li-Fi access points. A CQI associated with the first Li-Fi access point is highest amongst the set of Li-Fi access points. The stored processor-executable instructions on execution, may further cause the processor to schedule data transmission from the set of Li-Fi access points in a mutually exclusive time slot. The UE accepts data received from the attached Li-Fi access point and drops data received from remaining set of Li-Fi access points. The remaining set of Li-Fi access points does not include the first Li-Fi access point. 
     In yet another embodiment, a UE for managing interference between a set of Li-Fi access points in a Li-Fi communication network is disclosed. The UE includes a processor and a memory communicatively coupled to the processor, wherein the memory stores processor instructions, which when executed by the processor, cause the processor to transmit a plurality of uplink data frames. Each of the plurality of uplink data frames comprises a response to an associated downlink test frame received from an associated Li-Fi access point within the set of Li-Fi access points. The response includes one of a ACK and a NACK for the associated downlink test frame and a Channel Quality Indication (CQI) for the associated Li-Fi access point based on the associated downlink test frame. The processor instructions further cause the processor to attach with a first Li-Fi access point from the set of Li-Fi access points. A CQI associated with the first Li-Fi access point is highest amongst the set of Li-Fi access points. The processor instructions cause the processor to process data transmission scheduled from the set of Li-Fi access points in a mutually exclusive time slot. The processing includes accepting data received from the attached Li-Fi access point and dropping data received from remaining set of Li-Fi access points, wherein the remaining set of Li-Fi access points does not include the first Li-Fi access point. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. 
         FIG. 1  is a block diagram of a system within an exemplary Light Fidelity (Li-Fi) communication network for managing interference between a set of Li-Fi access points using an interference management device, in accordance with some embodiments. 
         FIG. 2  is a functional block diagram of a system within an exemplary Li-Fi communication network for managing interference between a set of Li-Fi access points, in accordance with some embodiments. 
         FIG. 3  is a block diagram of a coordinator configured to manage interference between a set of Li-Fi access points, in accordance with some embodiments. 
         FIG. 4  is a flow diagram of an exemplary control logic for managing interference between a set of Li-Fi access points in a Li-Fi communication network, in accordance with some embodiments. 
         FIG. 5  illustrates an exemplary downlink data frame transmitted by a Li-Fi access point to a UE, in accordance with some embodiments. 
         FIG. 6  illustrates an exemplary uplink data frame transmitted by a UE to a Li-Fi access point, in accordance with some embodiments. 
         FIG. 7  illustrates an exemplary communication flow of an exemplary mechanism of attaching a UE with a first Li-Fi access point amongst two Li-Fi access points, in accordance with some embodiments. 
         FIG. 8  illustrates a graphical representation of scheduling transmission of data from a first Li-Fi access point and a second Li-Fi access point in a mutually exclusive time slot and reception of the data by a UE, in accordance with some embodiments. 
         FIG. 9  is a flow diagram of an exemplary method for identifying and eliminating a redundant Li-Fi access point from data transmission, in accordance with some embodiments. 
         FIG. 10  is an exemplary phase interference table for detecting interference between a set of Li-Fi access points, in accordance with some embodiments. 
         FIG. 11  illustrates an exemplary graphical representation for detecting interference between a set of Li-Fi access points, in accordance with some embodiments. 
         FIG. 12  is a flow diagram of an exemplary method for identifying interference between a set of Li-Fi access points based on ranging response received by a UE, in accordance with some embodiments. 
         FIG. 13  illustrates an exemplary graphical representation of receipt of a ranging response from each of the set of Li-Fi access points by a UE, in accordance with some embodiments. 
         FIG. 14  is a flow diagram of an exemplary method for performing handover of a UE from a first Li-Fi access point to a second Li-Fi access point within a set of Li-Fi access points, in accordance with some embodiments. 
         FIG. 15  illustrates an exemplary communication flow for performing handover of a UE from a first Li-Fi access point to a second Li-Fi access point within a set of Li-Fi access points, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments are described with reference to the accompanying drawings. Wherever convenient, the same reference numbers are used throughout the drawings to refer to the same or like parts. While examples and features of disclosed principles are described herein, modifications, adaptations, and other implementations are possible without departing from the spirit and scope of the disclosed embodiments. It is intended that the following detailed description be considered as exemplary only, with the true scope and spirit being indicated by the following claims. Additional illustrative embodiments are listed below. 
       FIG. 1  illustrates a system  100  within an exemplary Light Fidelity (Li-Fi) communication network for managing interference between a set of Li-Fi access points  108 ,  110 , and,  112  using an interference management device  102 , in accordance with some embodiments. In some embodiments, the interference management device  102  may be connected to each of the set of Li-Fi access points  108 ,  110 , and  112 . A light signal region  114  is a data signal transmitted by the Li-Fi access point  108 . The light signal region  114  may interfere With a data signal transmitted by the Li-Fi access point  110 . In such case, a first interference region  116  is created, which is a region of interference between the light signal region  114  and the data signal transmitted by the Li-Fi access point  110 . The first interference region  116  may further interfere with a data signal transmitted by the Li-Fi access point  112 . In such case, a second interference region  118  is created, which is a region of interference between the first interference region  116  and the data signal transmitted from the Li-Fi access point  112 . 
     The system  100  may further include a plurality of User Equipments (UEs)  120 ,  122 ,  124 , and  126  that may receive data signals from one or more of the Li-Fi access points  108 ,  110 , and  112  at different locations. As will be appreciated, each of the plurality of UEs may be a computing device with Li-Fi support (for example, a server, a desktop, a laptop, a notebook, a netbook, a tablet, a smartphone, a mobile phone, or the like) or any additional device providing Li-Fi compatibility (for example, a dongle, a Li-Fi sleeve, or the like) to a computing device. The UE  120  and the UE  122  may be located in the light signal region  114 . Further, the UE  124  may be located in the first interference region  116  and the UE  126  may be located in the second interference region  118 . 
     The interference management device  102  may include a processors  104  and a computer-readable medium  106 . The computer-readable medium  106  may store instructions that, when executed by the processor  104 , may cause the processor  104  to manage interference in the Li-Fi communication network, in accordance with various embodiments. The computer-readable medium  106  may also store various data (for example, unique phase of each of the set of Li-Fi access points  108 ,  110 , and  112 , information of each of the plurality of UEs  120 ,  122 ,  124 , and  126  in vicinity of at least one of the set of Li-Fi access points  108 ,  110 , and  112 , or the like) that may be captured, processed, and/or required by the interference management device  102 . The interference management device  102  may interact with the set of Li-Fi access points  108 ,  110 , and  112  for sending or receiving various data. The interference management device  102  may also interact with the plurality of UEs  120 ,  122 ,  124  and  126  for receiving various data, via, one or more of the set of Li-Fi access points  108 ,  110 , and  112 . 
     Referring now to  FIG. 2 , a functional block diagram of a system  200  within an exemplary Li-Fi communication network for managing interference between a set of Li-Fi access points is illustrated, in accordance with some embodiments. The system  200  may include a Li-Fi access point  202  and a UE  204 . The Li-Fi access point  202  may include a photo receptor  212 , a decoder  214 , an encoder  220 , a coordinator  222 , and an Light Emitting Diode (LED)  224 . In some embodiments, the photo receptor  212  may be an Infrared (IR) receiver. 
     Further, the UE  204  may also include an encoder  208 , a photo transmitter  210 , a photo sensor  226 , and a decoder  228 . In some embodiments, the photo transmitter  210  may be an IR transmitter. The LED  224  and the photo sensor  226  may together form a downlink transmission reception system. Further, the photo transmitter  210  and the photo receptor  212  may together form an uplink transmission reception system. The UE  204  may transmit data to the Li-Fi access point  202  through the uplink photo transmitter  210 . Application transmitting data  206  and  218  and application receiving data  216  and  230  may interface with the downlink transmission reception system and the uplink transmission reception system respectively, in order to transmit and receive data. 
     Referring now to  FIG. 3 , a block diagram of a coordinator  304  configured to manage interference between a set of Li-Fi access points is illustrated, in accordance with some embodiments. The coordinator  304  is analogous to the coordinator  222  and the set of Li-Fi access points, for example, may be the set of Li-Fi access points  108 ,  110 , and  112 . The coordinator  304  may include a clock synchronization block  306 , a UE registration block  308 , an interference management unit  310 , and a multi-user support block  312 . The coordinator  304  may receive data  302  from either a Li-Fi access point (for example, the Li-Fi access point  108 ) or a UE (for example, the UE  120 ), via the Li-Fi access point. The clock synchronization block  306  may assign a unique phase to each of the set of Li-Fi access points. By way of an example, the clock synchronization block  306  may assign a phase 1 to the Li-Fi access point  108 , a phase 2 to the Li-Fi access point  110 , and a phase 3 to the Li-Fi access point  112 . 
     The UE registration block  308  may receive and store device information from each of the plurality of UEs in vicinity. The device information may be stored to perform various operations, which may include, but are not limited to providing multiple access, seamless handover to another Li-Fi access point, UE attachment, or interference detection, The interference management unit  310  may perform various techniques for mitigating interference between two or more Li-Fi access points. 
     The multi-user support block  312  may apply various multiple access techniques for handling of the plurality of UEs in order to provide multi-user support to the plurality of UEs (which may be present both in overlapping and non-overlapping regions). In some exemplary scenarios, the UE  120 , the UE  122 , and the UE  124  may be located in the light signal region  114  of the Li-Fi access point  108 . As will be appreciated, in such scenarios, access to more than one UE may require a multiple access method. In such scenarios for some embodiments, the multiple access method may be an Orthogonality based Multiple Access technique. In such scenarios, the multi-user support block  312  may provide unique orthogonal codes to each of the UE  120 , the UE  122 , and the UE  124 , thereby enabling a multi-user support. For example, while not necessary, orthogonal codes may be generated as [1 1 1 1] for the UE  120 , [1 1 −1 −1] for the UE  122 , and [1 −1 1 −1] for the UE  124 , as specified in the Code generation and allocation section of ETSI TS 125 213 V13.0.0 (2016 January) [UTMS Spreading and Modulation (FDD)]. These orthogonal codes may then be communicated to a corresponding UE. Each of the orthogonal codes may be used to maintain orthogonality between the UEs  120 ,  122 , and  124  that are using a single channel. It may be noted that for such embodiments, the number of UEs may be more than three. 
     Referring now to  FIG. 4 , an exemplary control logic  400  for managing interference between a set of Li-Fi access points in a Li-Fi communication network is disclosed via a flowchart, in accordance with some embodiments. In an embodiment, the control logic  400  may be executed by a system, such as the system  100  or the interference management device  102 . As illustrated in the flowchart, the control logic  400  may include receiving a plurality of uplink data frames sent by a UE, at step  402 . Each of the plurality of uplink data frames may include a response to an associated downlink test frame received from an associated Li-Fi access point within the set of Li-Fi access points. By way of an example, the UE  124  is associated or attached with the Li-Fi access point  108 . It must be noted that the UE  124  is also within the range of data signal transmitted by the Li-Fi access point  110 . The Li-Fi access point  108  may send a downlink test frame to the UE  124 . In response, the UE  124  may send an uplink data frame. The uplink data frame may be received by the interference management device  102 , via the Li-Fi access point  108 . 
     For a given uplink data frame, the response may include one of an Acknowledgement (ACK) and a Negative Acknowledgment (NACK) for the associated downlink test frame. Additionally, the response may include a Channel Quality Indication (CQI) for the associated Li-Fi access point, based on the associated downlink test frame. In continuation of the example given above, the uplink data frame sent by the UE  124  may include an ACK. An ACK in the uplink data frame indicates that data in the downlink test frame sent by the Li-Fi access point  108  was received by the UE  124 . Alternatively, the uplink data frame sent by the UE  124  may include a NACK. A NACK in the uplink data frame indicates that data in the downlink test frame sent by the Li-FI access point  108  was not received by the UE  124  or was received with errors. Further, the uplink data frame sent by the UE  124  may include the CQI for the Li-Fi access point  108 . This is further explained in detail in conjunction with  FIG. 5  and  FIG. 6 , 
     The control logic  400  may further include detecting presence of the UE in an interference region of the set of Li-Fi access points, based on presence of at least one NACK in at least one of the plurality of uplink data frames received from the set of Li-Fi access points, at step  404 . In continuation of the example above, when the uplink data frame sent by the UE  124  includes a NACK, it may indicate that the UE  124  is present in an interference region, for example, the first interference region  116 . 
     The control logic  400  may further include attaching, at step  406 , the UE with a first Li-Fi access point from the set of Li-Fi access points. A CQI associated with the first Li-Fi access point may be the highest amongst the set of Li-Fi access points. In continuation of the example given above, the CQI of the Li-Fi access point  108  is greater than the CQI of the Li-Fi access point  110 , thus the UE  124  is attached to the Li-Fi access point  108 . This is further explained in detail in conjunction with  FIG. 7 . 
     The control logic  400  may further include scheduling, at step  408 , data transmission from the set of Li-Fi access points in a mutually exclusive time slot. The data transmission is scheduled, such that, the UE accepts data received from the attached Li-Fi access point and drops data received from remaining set of Li-Fi access points. The remaining set of Li-Fi access points does not include the first Li-Fi access point. In continuation of the example given above, for the Li-Fi access points  108  and  110 , data transmission is scheduled, such that, the Li-Fi access points  108  transmits data in a first time slot, while the Li-Fi access points  110  transmits data in a second time slot subsequent to the first time slot. This data transmission through mutually exclusive time slots is carried out iteratively. Since the UE  124  is attached to the Li-Fi access point  108 , the UE  124  accepts data received transmitted by the Li-Fi access point  108  and drops the data transmitted by the Li-Fi access point  110 . This is further explained in detail in conjunction with  FIG. 8 . 
     Referring now to  FIG. 5 , an exemplary downlink data frame  500  transmitted by a Li-Fi access point to a UE is illustrated, in accordance with some embodiments. The Li-Fi access point, for example, may be the Li-Fi access point  108  and the UE, for example, may be the UE  124 . The downlink data frame  500  includes a start frame  502 , a cell ID  504 , a data  506 , a tracking downlink  508 , and an end frame  510 . The start frame  502  indicates start of the downlink data frame  500  and the cell ID  504  may be an identifier of the Li-Fi access point (for example, an identifier for the Li-FI access point  108 ). The cell ID  504  may be in a numerical format and in an embodiment, the coordinator  304  may assign the cell ID  504  to the Li-Fi access point. Further, the tracking downlink  508  may be a test frame sent by the Li-Fi access point to the UE in order to maintaining connectivity with the UE. The tracking downlink  508  may aid in detecting interference between two or more Li-Fi access points. The end frame  510  may indicate end of the downlink data frame  500 . The UE may send an uplink data frame in response to the downlink data frame  500 . This is further explained in detail in conjunction with  FIG. 6 . 
     Referring now to  FIG. 6 , an exemplary uplink data frame  600  transmitted by a UE to a Li-Fi access point is illustrated, in accordance with some embodiments. The UE, for example, may be the UE  124  and the Li-Fi access point, for example, may be the Li-Fi access point  108 . The uplink data frame  600  may be sent from the UE to the Li-Fi access point in response to the downlink data frame  500  sent by the Li-Fi access point to the UE. The uplink data frame  600  may include a start frame  602 , a cell ID  604 , a UE ID  606 , a CQI  608 , a tracking uplink  610 , and an end frame  612 . While the start frame  602  indicates start of the uplink data frame  600 , the end frame  612  indicates end of the uplink data frame  600 . The cell ID  604  indicates the identifier of the Li-Fi access point. Thus, the value in cell ID  504  and the cell ID  604  would be the same. 
     After receiving the downlink data frame  500 , the UE may calculate the CQI  608  of the Li-Fi access point based on a Packet Error Rate (PER) associated with the Li-Fi access point. By way of an example, when the UE is the UE  124  and the Li-Fi access point is the Li-Fi access point  108 , the CQI  608  would represent CQI value associated with the Li-Fi access point  108 . Further, the tracking uplink  610  may include either an ACK or a NACK. The ACK may indicate that data transmitted by the Li-Fi access point was received without errors and that the UE is not experiencing any interference. Similarly, the NACK may indicate that data transmitted by the Li-Fi access point was received with errors and that the UE may be experiencing interference. The tracking uplink  610  may be sent by the UE to the Li-Fi access point in order to maintain connectivity. 
     Referring now to  FIG. 7 , a communication flow  700  of an exemplary mechanism of attaching a UE with a first Li-Fi access point amongst two Li-Fi access points is illustrated, in accordance with some embodiments. The communication flow  700  may include the UE  124 , the Li-Fi access point (AP)  108 , the Li-Fi access point (AP)  110 , the interference management unit (IMU)  310 , and the clock synchronization block (CSB)  306 . The CSB  306  assigns a first phase  702  to the AP  108  and a second phase  704  to the AP  110 . Upon detection of interference between the APs  108  and  110  by the coordinator  304 , the IMU  310  may initiate interference mitigation. To this end, the IMU  310  may send a test frame  706  to the AP  108  and a test frame  708  to the AP  110 . The AP  108  may further send the test frame  706  to the UE  124  through the first phase  702 . In a similar manner, the AP  110  may further send the test frame  708  to the UE  124  through the second phase  704 . In some embodiments, the test frame  706  and the test frame  708  may be similar to the downlink data frame  500 . 
     The UE  124  may receive the test frame  702  and may evaluate a PER  710 . The UE  124  may send the PER  710  along with a NACK/ACK signal  712  to the AP  108 . The AP  108  may send the PER  710  to the IMU  310  and the NACK/ACK signal  712  to the CSB  306 . A similar sequence of steps may be applied for the AP  110  by the UE  124  to obtain and send a PER  714  and a NACK/ACK signal  716  to the IMU  310  and to the CSB  306 , respectively. In some embodiments, the NACK/ACK signals  712  and  714  may be a part of the uplink data frame  600 . 
     After receiving the PERs  710  and  714 , the IMU  310  may determine that the PER  710  is less than the PER  714 . Based on this, the IMU  310 , at  716 , may initiate attaching the UE  124  with the AP  108 . In some embodiments, PER may be used to estimate a CQI. In such embodiments, instead of PERs  710  and  714 , respective CQI values may be shared by the UE  124 . Additionally, in such embodiment, the IMU  310  may attach the UE  124 , at  718 , with the AP  108 , when a first CQI corresponding to the PER  710  is greater than a second CQI corresponding to the PER  714 . Once the UE  124  is attached to the AP  108 , the UE  124  may accept data transmitted by the AP  108  and may drop the data transmitted by the AP  110 . This is further explained in detail in conjunction with  FIG. 8 . 
     Referring now to  FIG. 8 , a graphical representation  800  of scheduling transmission of data from the AP  108  and the AP  110  in a mutually exclusive time slot and reception of the data by the UE  124  is illustrated, in accordance with some embodiments. The graphical representation  800  may be an amplitude-time graph for each of the AP  108  and the AP  110 . In some embodiments, the IMU  310  may instruct the AP  108  and the AP  110  to transmit data signals according to the unique phase allocated to each of the AP  108  and the AP  110  by the CSB  306  over a time  802 . 
     In some embodiments, the AP  108  may transmit a data signal depicted as a flicker  804  or a non-flicker  806  on the graphical representation  800 . In such embodiments, the non-flicker  806  may be a time period of a constant intensity whereas the flicker  804  may be a time period of a lower or higher light intensity. As an example, the transmitting LED could be supplied with an average voltage (Vavg). When a bit pattern 1 is detected, the LED transmits with higher voltage (Vavg+v) for the bit duration and when a bit pattern 0 is detected, the LED transmits with a lower voltage (Vavg−v) for the bit duration. In a similar manner, in such embodiments, data signal of the AP  110  may be depicted as a flicker  808  or a non-flicker  810  on the graphical representation  800 . Referring back to  FIG. 7 , and in an exemplary scenario, the CQI of the AP  108  may be higher than the CQI of the AP  110 . In such a scenario, the UE  124  may accept the data signal from the AP  108  and reject the data signals from the AP  110 . As will be appreciated, the decoder  228  of the system  200  may aid the UE  124  in decoding the data signal received from the AP  108 . 
     Referring now to  FIG. 9 , an exemplary method  900  for identifying and eliminating a redundant Li-Fi access point from data transmission is depicted, in accordance with some embodiments. The redundant Li-Fi access point may be eliminated from a set of Li-Fi access points (for example, the set of Li-Fi access points  108 ,  110 , and  112 ). The method  900  may include allocating a unique phase to each of the set of Li-Fi access points, at step  902 . Further, the method  900  may include detecting an interference between the set of Li-Fi access points, at step  904 . At step  906 , at least one unique phase may be determined as detected by the UE at each of a plurality of locations. At step  908 , at least one location from the plurality of locations may be identified as prone to interference. At the at least one location, the UE may detect two or more unique phases, thereby indicating interference. At step  910 , a redundant Li-Fi access point may be identified from the set of Li-Fi access points based on the step  906 . For the redundant Li-Fi access point, at each of the plurality of locations, the UE detects a unique phase allocated to the redundant Li-Fi access point and at least one unique phase allocated to a non-redundant Li-Fi access point from the set of Li-Fi access points. At step  912 , the redundant Li-Fi access point may be eliminated from data transmission. In some embodiments, the redundant Li-Fi access point may be used only as an illumination source. 
     Referring back to  FIG. 1 , in an exemplary scenario, data signal from the Li-Fi access point  110  may receive interference from the data signals of Li-Fi access points  108  and  112  at each location within the Li-Fi communication network. Moreover, the region covered by the data signal of the Li-Fi access point  110  is also covered either by the Li-Fi access point  108  or the Li-Fi access point  112 . In such a scenario, the Li-Fi access point  110  may be considered as a redundant Li-Fi access point and may thus be eliminated and may only be used as an illumination source. As a result of this elimination, interference mitigation and management only needs to be performed for the Li-Fi access points  108  and  112 . 
     Referring now to  FIG. 10 , an exemplary phase interference table  1000  for detecting interference between a set of Li-Fi access points is illustrated, in accordance with some embodiments. The phase interference table  1000  includes results of an exemplary experimental setup further including the UE  124  and three Li-Fi access points, i.e., the AP  108 , the AP  110 , and the AP  112 . Further, the phase interference table  1000  includes observational values for a UE ID  1002  of the UE  124 , a light intensity  1004  (in lux) of each of the APs  108 ,  110 , and  112  at varying locations of the UE  124 , and a phase  1006  allocated to each of the APs  108 ,  110 , and  112 , by the CSB  306 . 
     In some embodiments, the values of the phase  1006  for each of the APs  108 ,  110 , and  112 , may be detected by the UE  124  and may be transferred to the IMU  310 . In some embodiments, the phase  1006  of the APs  108 ,  110 , and  112  may be φ1, φ2, and φ3, respectively. In some exemplary scenarios of such embodiments, a location of the UE  124  may be in a region of interference between at least two APs from the APs  108 ,  110 , and  112 . The interference, for example, may be between the AP  108  and the AP  110 . In such scenarios of such embodiments, the UE  124  may detect the phase  1006  values of the at least two APs, thereby detecting interference between the at least two APs. In some embodiments, the phase  1006  values may further be used to detect a redundant Li-Fi access point. In some exemplary scenarios of such embodiments, a phase value for a redundant Li-Fi access point may always be received along with one of the three Li-Fi access points. In such scenarios, such embodiments may eliminate the redundant Li-Fi access point from data transmission. By way of an example and referring to the table  1000 , φ2 assigned to the AP  110  is always received along with φ1 assigned to the AP  108 . Thus, the AP  110  may be identified as a redundant Li-Fi access point. 
     Referring now to  FIG. 11 , an exemplary graphical representation  1100  for detecting an interference between a set of Li-Fi access points is illustrated, in accordance with some embodiments. The graphical representation  1100  includes a line chart of the phase interference table  1000 . Further, the graphical representation  1100  includes an intensity distribution of each of the APs  108 ,  110 , and  112  on the y-axis and a plurality of corresponding reference points on the x-axis. Further, the graphical representation  1100  includes line representations for the light intensity  1004  for each of the APs  108 ,  110 , and  112 . 
     Referring now to  FIG. 12 , a flow diagram of an exemplary method  1200  for identifying interference between a set of Li-Fi access points based on ranging response received by a UE is illustrated, in accordance with some embodiments. At step  1202 , a unique phase may be allocated to each of the set of Li-Fi access points. At step  1204 , the UE may be instructed to transmit a ranging signal in an uplink data frame within the Li-Fi communication network. In response to the ranging signal, at least one of the set of Li-Fi access points may send at least one ranging response. At step  1206 , the at least one ranging response received from at least one of the set of Li-Fi access points may be analyzed. Each of the at least one ranging response may include an identifier of an associated Li-Fi access point. Based on the analysis of the at least one ranging response, interference between the at least one of the set of Li-Fi access points may be identified, at step  1208 , between the set of Li-Fi access points. 
     Referring now to  FIG. 13 , an exemplary graphical representation  1300  of receipt of a ranging response from each of a set of Li-Fi access points by a UE is illustrated, in accordance with some embodiments. The graphical representation  1300  may include a measure for the ranging response on the y-axis  1302  and time on the x-axis  1310 . In some embodiments, the measure for the ranging response may be an amplitude. Further, the graphical representation  1300  may include values for the ranging responses RR-AP  1304  for a first Li-Fi access point, RR-AP  1306  for a second Li-Fi access point, and RR-AP  1308  for a third Li-Fi access point. It may be noted that each of the ranging responses RR-AP  1304 , RR-AP  1306 , and RR-AP  1308  may be transmitted in a single phase, one at a time for better identification by the UE. It may also be noted that the ranging responses RR-AP  1304 , RR-AP  1306 , and RR-AP  1308  may provide information to the coordinator  304  related to visibility of the set of Li-Fi access points for the UE. 
     Referring now to  FIG. 14 , an exemplary method  1400  for performing handover of a UE from a first Li-Fi access point to a second Li-Fi access point within a set of Li-Fi access points is illustrated, in accordance with some embodiments. The UE may be attached to the first Li-Fi access point. By way of an example, the UE may be the UE  124 , the first Li-Fi access point may be the Li-Fi access point  108 , the second Li-Fi access point may be the Li-Fi access point  110 . In this example, the UE  124  may be attached to the Li-Fi access point  108 . At step  1402 , a plurality of uplink data frames (for example, the uplink data frame  500 ) sent by a UE may be received, for example, by the interference management device  102 . Based on the plurality of uplink data frames received from the UE, at step  1404 , the CQI of the first Li-Fi access point may be compared with the CQI of the second Li-Fi access point. It may be determined that the CQI of the second Li-Fi access point is higher than the CQI of the first Li-Fi access point. Thus, at step  1406 , handover of the UE from the first Li-Fi access point to a second Li-Fi access point may be performed. This is further explained in detail in conjunction with  FIG. 15 . 
     Referring now to  FIG. 15 , an exemplary communication flow  1500  for performing handover of a UE from a first Li-Fi access point to a second Li-Fi access point within a set of Li-Fi access points, in accordance with some embodiments. The mechanism  1500  may include the UE  124 , the AP  108 , the AP  110 , the IMU  310 , and the CSB  306 . The CSB  306  assigns a first phase  1502  to the AP  108  and a second phase  1504  to the AP  110 . As discussed in  FIG. 14 , the UE  124  may initially be attached to the AP  108 , as the CQI of the AP  108  at the time of initial evaluation was greater than the CQI of the AP  110 . Even after the UE  124  is attached to the AP  108 , the IMU  310  may continue sending test frames from each of the AP  108  and the AP  110  to the UE  124  for dynamic evaluation of CQI of the AP  108  and the AP  110 . 
     To this end, the IMU  310  may send a test frame  1506  to the AP  108  and a test frame  1508  to the AP  110 . The AP  108  may further send the test frame  1506  to the UE  124  through the first phase  1502 . In a similar manner, the AP  110  may further send the test frame  1508  to the UE  124  through the second phase  1504 . In some embodiments, the test frame  1506  and the test frame  1508  may be similar to the downlink data frame  500 . 
     The UE  124  may receive the test frame  1502  and may evaluate a PER  1510 . The UE  124  may send the PER  1510  along with a NACK/ACK signal  1512  to the AP  108 . The AP  108  may send the PER  1510  to the IMU  310  and the NACK/ACK signal  1512  to the CSB  306 . A similar sequence of steps may be applied for the AP  110  by the UE  124  to obtain and send a PER  1514  and a NACK/ACK signal  1516  to the IMU  310  and to the CSB  306 , respectively. In some embodiments, the NACK/ACK signals  1512  and  1514  may be a part of the uplink data frame  600 . 
     After receiving the PERs  1510  and  1514 , the IMU  310  may determine that the PER  1514  is less than the PER  1516 . Based on this, the IMU  310  at  1516 , may perform handover of the UE  124  from the AP  108  to the AP  110 . In some embodiments, PER may be used to estimate a CQI). In such embodiments, instead of PERs  1510  and  1514 , respective CQI values may be shared by the UE  124 . Additionally, in such embodiment, the IMU  310  may handover the UE  124 , at  1518 , from the AP  108  to the AP  110 , when a first CQI corresponding to the PER  1510  is greater than a second CQI corresponding to the PER  1514 . 
     As will be appreciated, the above described techniques may take the form of computer or controller implemented processes and apparatuses for practicing those processes. The disclosure can also be embodied in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, solid state drives, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer or controller, the computer becomes an apparatus for practicing the invention. The disclosure may also be embodied in the form of computer program code or signal, for example, whether stored in a storage medium, loaded into and/or executed by a computer or controller, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. 
     As will be appreciated by those skilled in the art, the techniques described in the various embodiments discussed above are not routine, or conventional, or well understood in the art. As mentioned earlier, the techniques include determining visibility of a set of Li-Fi access points for a UE, eliminating redundant Li-Fi access points, detecting interference between the set of Li-Fi access points, sending data from each of the set of Li-Fi access points in a time shift manner, evaluating CQI of each of the set of Li-Fi access points for the UE, and attaching to a Li-Fi access point with the highest CQI. Further, the techniques may provide for dynamic evaluation of CQI of the set of Li-Fi access points for the UE and a handover of connection to a second Li-Fi access point with a higher CQI. Further, techniques may provide for a multiple user support using multiple access method. Typically, when a UE moves from one Li-Fi access point to another, connectivity persists as long as the UE stays in vicinity of modulated light. It may be noted that if there is a region where modulated lights from one or more adjacent Li-Fi access points interfere, the UE may stop receiving data. Further, it may be noted that there is no method to detect physical cell IDs of the Li-Fi access points associated to the UE in interference region. 
     As will also be appreciated by those skilled in the art, current Li-Fi systems lack the mechanism to overcome the interference caused by the adjacent Li-Fi access points modulated using a white light (single carrier). The techniques described above provide for managing interference between a set of Li-Fi access points in a Li-Fi communication network. In particular, the above techniques provide for detecting and mitigating interference between the set of Li-Fi access points by allocating a unique phase to each of the set of Li-Fi access points, transmitting data signals from each of the set of Li-Fi access points in a time shift manner, dynamically evaluating CQI of each of the Li-Fi access points for a UE, and attaching/handing over the UE to a Li-Fi access point with the highest CQI. 
     The specification has described managing interference between a set of Li-Fi access points in a Li-Fi communication network. The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. 
     Furthermore, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the present disclosure. A computer-readable storage medium refers to any type of physical memory on which information or data readable by a processor may be stored. Thus, a computer-readable storage medium may store instructions for execution by one or more processors, including instructions for causing the processor(s) to perform steps or stages consistent with the embodiments described herein. The term “computer-readable medium” should be understood to include tangible items and exclude carrier waves and transient signals, i.e., be non-transitory. Examples include random access memory (RAM), read-only memory (ROM), volatile memory, nonvolatile memory, hard drives, CD ROMs, DVDs, flash drives, disks, and any other known physical storage media. 
     It is intended that the disclosure and examples be considered as exemplary only, with a true scope and spirit of disclosed embodiments being indicated by the following claims.