## 4 Structure and Operation of Coded Laser Pilots-Based HILPB WPT System
### Power Receiver (PRX)  
An EV communicating with traffic lights via V2I functions as a PRX. It receives HILPBs transmitted from PTXs using a PV array and converts them into electricity for power supply. It can broadcast PCI request messages, transfer start messages, and transfer stop messages to PTXs via V2I communication. It receives and decodes the unique PCI sent from a PTX through its designated WPC using the DS-OCDMA system and calculates the maximum deliverable power (MDP) of a PTX and WPC on the basis of the RCPI of the incoming laser beam. Based on the calculation results, it selects the optimal PTX and WPC best suited for its MPQ. The operation of a PRX is divided into standby, detection, and transfer steps as marked in red, green, and blue, respectively, in Algorithm 2. In the standby step, the PRX does not receive any laser beams. It proceeds to the detection step and broadcasts a PCI request message via V2I whenever an MPQ is detected. In the detection step, the PRX receives the PCI from each of the PTXs responding to its PCI request message, thereby recording the RCPI. Thus, the data received are decoded with DS-OCDMA, followed by checksum (CRC) comparison and storage of errorless PCI along with RCPI. RCPI varies from an incoming laser beam to another depending on the distance between the PTX and PRX, the laser beam incident angle, and the power distribution in the PV array, because each PTX transmits its unique PCI within the range of Class 1 MPE per pulse. The MDP from a PTX through a particular WPC can be calculated using the RCPI. Among the parameters in Equation (6),the laser power (\(P_{Tclass1}\)) is within Class 1 MPE per pulse; however, it becomes the MDP when HILPB is transmitted. Because the PV array area (\(A\)) is a characteristic of the PRX, all PTXs have the same values for the same PRX. Therefore, the calculation of the PTE (\(\tau_{sys}\)) based on the RCPI, which varies from one PTX to another in the detection step, can be simplified to Equation (6). \[\tau_{sys}=\frac{P_{R}}{P_{Tclass1}}. \tag{6}\]  
Using the PTE calculated on the basis of the RCPI during the detection period, the amount (\(U\)) of MDP of the PRX at the MTP (\(P_{Tmax}\)) can be defined by Equation (7). \[U=P_{Tmax}\times\tau_{sys}. \tag{7}\]  
```
thread TIME_SYNC() if 1 pps then SYNC_LOCAL_TIME() pos=POSITIONING_DGPS() end if end thread thread MAIN() PCI_prx_id=V2I_ALLOCATE_PRX_ID() V2I_BROADCAST_PCI_REQUEST(PCI.prx_id,pos) while (1 sec) do while (40 us) do \(1\leftarrow\) MEASURE_POWER_PV_ARRAY() end while t=SELECT_BEST_CHANNEL(i) for t in each selected_prx do V2I_REQUEST_CHARGING(t.ptx_id,t.p,t.a) end for V2I_BROADCAST_CHARGING(START) CHARGE_BATTERY() V2I_BROADCAST_CHARGING(END) end thread function OCDMA_RECEPTION(prx_id,l) m \(\leftarrow\) NRZ_OOK(l) for code in each_synchronous_prime_sequence_code do if AUTOCORRELATION(m,code)=PRIME_SEQ_WEIGHT then s\(\leftarrow\)ENCODE_SYNC_PRIME_SEQ(m) if s.crc=CRC3(s.prx_id,s.ptx_id,sp,s.a,smpt) then if s.prx_id==prx_id then mdp \(\leftarrow\)CALC_MDP(CALC_PTE(CALC_RCPI(l)),s.mpt) i \(\leftarrow\)PCI_INFO(mdp,s.ptx_id,s.p,s.a,smpt) end if end if end if end for return i end function
```  
**Algorithm 2** PRX operation algorithm. The PRX establishes the optimal power transmission path by selecting the optimal PTX and WPC based on the amount of MDP of each PRX through each designated WPC calculated by substituting each PTX's unique PCI and RCPI into Equations (6) and (7). The PRX then proceeds to the transfer step by sending the transfer start message to the selected PTX along with the PCI on the designated WPC. If the MDP of one PTX does not meet it's MPQ, the PRX sends the transfer start message to two or more PTXs, distributing the total amount of required power supply among them. The PRX converts the HILPB received through the PV array into electricity for power supply. If the desired MPQ is met, the PRX sends a transfer stop message to the PTX. When all PTXs stop power delivery, the PRX returns to the standby step and stays in the standby mode until an MPQ is sensed.