KR20140085200A - In-band communication for wireless power transfer - Google Patents

Abstract

And physical layer and MAC layer protocols for in-band communication of a wireless power transmission system for wireless charging of multiple devices. A communication method of a wireless power transmission system according to the present invention is a communication method of a wireless power transmission system for wireless charging of multiple devices, the wireless power transmission system comprising: A base station for managing connection and release of data and wireless power transmission in the wireless power transmission network; And a plurality of nodes that are devices that receive wireless power from the base station, the wireless power transmission system having a center frequency between 80 kHz and 400 kHz Performs wireless power transmission and magnetic field communication using one frequency band, and performs wireless power transmission and magnetic field communication through a superframe composed of a request section, a response section and an autonomous section as a temporal component.

Description

≪ Desc / Clms Page number 1 > In-band communication for wireless power transmission [

The present invention relates to an in-band communication method of a wireless power transmission system for wireless charging of multiple devices, and more particularly, to an in-band communication method capable of simultaneously performing wireless power transmission and magnetic field communication using the same frequency band .

A wireless charging system using a magnetic induction phenomenon is being used as a wireless power transmission technology for transferring energy wirelessly.

For example, an electric toothbrush or a wireless shaver is charged with the principle of electromagnetic induction, and recently, wireless charging products capable of charging a portable device such as a mobile phone, a PDA, an MP3 player, and a notebook computer by using electromagnetic induction have been introduced .

However, the magnetic induction method of inducing a current from one coil to another through a magnetic field is very sensitive to the distance between the coils and the relative position thereof, so that the transmission efficiency is rapidly deteriorated even if the distance between the two coils is slightly decreased or turned. Accordingly, such a magnetic induction type charging system has a weak point that it can be used only at a short distance of a few cm or less.

On the other hand, U.S. Patent No. 7,741,735 discloses a non-radiation energy transfer method based on attenuation wave coupling of a resonance field. This is because the resonator with two identical frequencies has a tendency to be coupled to each other without affecting other surrounding non-resonators, and this technique has been introduced as a technology capable of transmitting energy to a far distance as compared with the conventional electromagnetic induction .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an in-band communication method capable of simultaneously performing wireless power transmission and magnetic field communication using the same frequency band.

The present invention provides a physical layer and a MAC layer protocol for in-band communication of a wireless power transmission system for wireless charging of multiple devices.

A communication method of a wireless power transmission system according to the present invention is a communication method of a wireless power transmission system for wireless charging of multiple devices, the wireless power transmission system comprising: A base station for managing connection and release of data and wireless power transmission in the wireless power transmission network; And a plurality of nodes that are devices that receive wireless power from the base station, the wireless power transmission system having a center frequency between 80 kHz and 400 kHz A wireless power transmission and a magnetic field communication are performed using a single frequency band and wireless power transmission is performed through a superframe composed of a request period, a response period and a spontaneous period as a temporal component. Transmission and magnetic field communication.

According to the present invention, wireless power transmission and data transmission of several kbps are possible based on a network formed within a distance of several meters.

1 illustrates a wireless power transmission system
Figure 2 shows a mobile device
Fig. 3 is a cross-
Figure 4 shows an iWPTN superframe structure for an MFC
5 shows an iWPTN superframe structure for WPT
FIG. 6 is a cross-
7 shows a UID structure
Figure 8 shows the iWPTN-B state diagram
Figure 9 shows the iWPTN-D state diagram
FIG. 10 illustrates a PHY layer frame format
11 shows a preamble format
12 shows a MAC layer frame format
Figure 13 shows a control field frame format
14 shows a request frame format
15 shows a response frame format
16 shows a data frame format
FIG. 17 shows a response confirmation frame format
Figure 18 shows a data verification frame format
Figure 19 shows a payload format
Figure 20 shows a connection request block format
FIG. 21 is a block diagram of a separation request block format
22 shows a connection state request block format
23 shows a data request block format
24 shows a group ID setup request block format
FIG. 25 shows a power transmission request block format
FIG. 26 is a block diagram of a power transfer start request block format
Figure 27 shows a payload format
Figure 28 illustrates a connection response block format
FIG.
30 shows a connection status response block format
FIG. 31 shows a data response block format
32 illustrates a group ID setup response block format
Figure 33 illustrates a power transmission response block format
Figure 34 shows a payload format
Figure 35 shows a payload format
Figure 36 shows a connection acknowledgment block format
FIG. 37 is a block diagram of the < RTI ID =
38 shows a connection status response confirmation block format
39 shows a data response confirmation block format
Figure 40 shows a group ID setup response confirmation block format
FIG. 41 is a diagram illustrating a PSFI
42 shows a PS beacon format
Figure 43 shows the frame control of the PS beacon
FIG. 44 shows the PSF
Figure 45 shows the frame control of the PSF
46 shows a BPTRq format
Figure 47 shows a BPTRs format
48 shows a connection procedure
FIG.
50 shows a connection status confirmation procedure
FIG. 51 is a flowchart illustrating a data transmission procedure
52 is a flowchart illustrating a data transfer procedure
53 shows a group ID setup procedure
54 shows a wireless power transfer procedure
55 shows a battery discharge procedure
56 shows an envelope waveform
57 shows a BPSK-modulated signal
58 shows an ASK-modulated signal
FIG.

3 Terms and Definitions

The following terms and definitions are used herein.

3.1 Wireless power transfer (WPT)

Mechanism for a device with sufficient power to transmit it wirelessly to another device

3.2 Wireless power transfer network (WPTN)

A system for transmitting wireless power to a device under consideration based on a recognition of the wireless power transmission state through wired /

3.3 Magnetic field communication (MFC)

Wireless communication using magnetic field

3.4 In-band wireless power transfer network (iWPTN)

A wireless power transmission network using one frequency band for wireless power transmission and magnetic field communication

3.5 In-band Wireless Power Transmission Network - Base Station (iWPTN-B)

A system for managing the transmission and reception times of data wireless power transmission within the iWPTN;

3.6 In-band Wireless Power Transmission Network - Appliance (iWPTN-D)

A device other than the base station constituting the network in the iWPTN, which receives wireless power from the base station

3.7 Magnetic field area network (MFAN)

Wireless network providing wireless communication based on reliable in-band magnetic field communication using magnetic field

4 Symbols and Abbreviations

The following abbreviations are used herein.

ABNR Abnormal

ARq Association Request

ARs Association Response

ARA Association Response Acknowledgment

ASC Association Status Check

ASK Amplitude Shift Keying

ASRq Association Status Request

ASRs Association Status Response

ASRA Association Status Response Acknowledgment

BPSK Binary Phase Shift Keying

BPTRq Battery-out Power Transfer Request

BPTRs Battery-out Power Transfer Response

MFC Magnetic Field Communication

CRC Cyclic Redundancy Check

DA Data Acknowledgment

DaRq Disassociation Request

DaRs Disassociation Response

DaRA Disassociation Response Acknowledgment

DRq Data Request

DRs Data Response

DRA Data Response Acknowledgment

FCS frame Check Sequence

GSRq Group ID Set-up Request

GSRs Group ID Set-up Response

GSRA Group ID Set-up Response Acknowledgment

HCS Header Check Sequence

LSB Least Significant Bit

MAC Media Access Control

NRZ-L Non-Return-to-Zero Level

PHY Physical Layer protocol

PTRq Power Transfer Request

PTRs Power Transfer Response

PS Power Status

PSF Power Status Feedback

PSFI Power Status Feedback Interval

RA Response Acknowledgment

RR Response Request

SIFS Short Inter Frame Space

TDMA Time Division Multiple Access

UID Unique Identifier

5 Overview

The iWPTN is a wireless network that can transmit power wirelessly and exchange the necessary data and control commands over an MFC system that uses the same frequencies as those used in wireless power transmission. Due to the characteristics of the magnetic field and the power level that satisfies the specification, the communication area is larger than the power transmission area. The necessary information is exchanged based on the communication link supported by MFAN, and iWPTN-B performs scheduling to provide efficient WPT.

The MFC system in the iWPTN has a central carrier frequency band of 30 KHz to 300 KHz, which is the same as the frequency band of the wireless power transmission. This can be implemented at low cost using a simple and robust modulation method such as BPSK, and a low error rate can be obtained. In addition, it is robust against noise using dynamic encoding methods such as Manchester or NRZ-Lem. This provides a data rate of several kbps within a few meters of distance. In WPT, non-modulated sinusoidal signals are used to increase WPT efficiency.

iWPTN uses a simple and efficient network topology such as star topology to reduce power consumption. It also uses dynamic address allocation for small packet sizes and efficient address management. Adaptive link quality control using variable transmission rate and coding method is used depending on the wireless charging environment. The nodes of iWPTN are classified into iWPTN-B and iWPTN-D according to their functions. Only one iWPTN-B exists in one iWPTN network, and a plurality of iWPTN-D nodes form a network around iWPTN-B. iWPTN-B manages connection and release of iWPTN-D. iWPTN uses Time Division Multiple Access (TDMA) for data transmission and reception. When iWPTN-D joins iWPTN-B managed by iWPTN-B, iWPTN-B allocates a time slot for transmission of iWPTN-D according to the request of iWPTN-D and the judgment of iWPTN-B .

As shown in Figure 1, iWPTN-B and iWPTN-D can be located indoors. When iWPTN-B receives data related to wireless power transmission such as ID or battery information from iWPTN-D, it collects the received data and calculates required factors such as the number of time slots for wireless power transmission or the power transmission order . iWPTN-B transmits control data for managing iWPTN to iWPTN-D.

iWPTN applies to a variety of industries. It is applied to electric devices that require power to perform functions. For some applications, power can be supplied wirelessly from outside the device to improve functionality. These devices solve problems such as the life of the battery or the structure for storing the battery.

For example, iWPTN provides a ubiquitous charging environment for mobile devices where battery life is always a problem as usage time increases (FIG. 2). For household appliances, the complicated wires and plugs can be eliminated, allowing for the placement of appliances and the desired decorations (Fig. 3).

6 Network Components

6.1 General

The main components of iWPTN are time and physical components. A time element indicates a superframe composed of a request period, a response period, and a spontaneous period, and a physical element indicates a network composed of iWPTN-B and iWPTN-D. The most basic element of a physical element is a node. The nodes are divided into two types: iWPTN-B, which manages the network, and iWPTN-D, which communicates with iWPTN-B.

FIGS. 4 to 6 show the structure of the superframe and the network, which are time and physical elements, respectively. The first node to be determined in the iWPTN is iWPTN-B, and the superframe is initiated by iWPTN-B sending a request packet during the request interval. iWPTN-B manages the association, disassociation, release and scheduling of iWPTN-D. One iWPTN uses one channel and consists of only one iWPTN-B and the remaining iWPTN-D using that channel. Among the nodes in iWPTN, the remaining nodes except iWPTN-B become iWPTN-D. Depending on the role, any node can be iWPTN-B or iWPTN-D. Basically, a P2P (peer-to-peer) connection between iWPTN-B and iWPTN-D is considered.

6.2 Time Elements

The time factor used in the iWPTN is the time slot of the TDMA scheme. iWPTN-B manages the iWPTN-D group that transmits data in the response interval, and the time slot is self-arraged by the selected iWPTN-D.

6.2.1 MFC Time Elements

The super frame of the iWPTN for the magnetic field communication is composed of a request period, a response period and an autonomous period as shown in FIG. 4, and the length of the request and response period is variable. The superframe is initiated by iWPTN-B sending an RR packet in the request interval.

The RR packet has information on which iWPTN-D will transmit the response packet during the response interval, and the selected iWPTN-D can transmit the response packet in the response interval according to the RR packet information.

6.2.1.1 Request section

In the request interval, iWPTN-B sends an RR packet containing the information that iWPTN-D uses to send the response packet in the response interval.

6.2.1.2 Response interval

In the response interval, iWPTN-D can transmit a response packet according to the RR packet received from iWPTN-B. The response interval is divided into a number of time slots according to the number of iWPTN-D selected in the iWPTN. The length of each time slot may vary depending on the length of the acknowledgment frame and acknowledgment (ACK). When iWPTN-B schedules the response interval, the slot number is determined according to the order of the divided time slots. Otherwise, the slot number is zero. The iWPTN-B allocates a time slot for use of a response interval to each iWPTN-D or a specific group, and the node of the assigned group independently transmits a data frame in the response interval.

6.2.1.3 Autonomous section

The autonomous section is started when there is no node transmitting a response packet for a certain period of time. During this interval, the node can transmit data without the request of iWPTN-B. This interval is maintained until iWPTN-B sends a request packet.

6.2.2 WPT Time Elements

A super frame for WPT of iWPTN is shown in Fig. 5, which is composed of a request interval, a response interval and an autonomous interval, and the length of each interval is variable. The superframe begins when iWPTN-B sends a PTRq packet to iWPTN-D in the request interval. When iWPTN-D receives the packet, it sends the PTRs packet in response. Based on the PTRs packet, the iWPTN-B transmits a PTS packet including scheduling information in which the iWPTN-D can receive the WPT during the response interval, and the selected iWPTN-D transmits the PS from the iWPTN- And transmits the PSF packet as a response of the beacon.

6.2.2.1 Request section

In the request interval, iWPTN-B transmits an RR packet including WPT scheduling information. The iWPTN-D receiving the RR packet prepares to receive the WPT from the iWPTN-B according to the scheduling information.

6.2.2.2 Response interval

In the WPT response interval, iWPTN-B provides WPT to iWPTN-D according to the scheduling order. The response interval can be divided into multiple time slots according to the number of iWPTN-D selected in the iWPTN. The length of each time slot is variable depending on the length of the WPT interval. If iWPTN-B schedules all time slots in the response interval, the slot number is determined by the order of the divided time slots. Otherwise, the slot number is zero. iWPTN-B allocates a time slot to iWPTN-D or a specific group. Depending on the scheduling order, one iWPTN-D receives the WPT, or all the iWPTN-Ds in the assigned group receive wireless power at the same time. Compared to the response interval of the magnetic field communication, the WPT response interval has the PSFI. Variable length PSFIs are intended for rapid power status updates and abnormal situations.

6.2.2.3 Autonomous section

The autonomous interval starts when all PSF packets from iWPTN-D considered in the last time slot of all response intervals are acknowledged. In this interval, the node can send an EPTq packet even if there is no iWPTN-B request. When iWPTN-B receives the EPTq packet, iWPTN-B transmits the EPT packet and then provides the WPT for a certain period of time. This interval is maintained until iWPTN-B sends a request packet.

6.2.3 Network activation

The superframe of the iWPTN is divided into a request interval, a response interval and an autonomous interval. iWPTN-B and iWPTN-D in iWPTN operate as follows in each section.

6.2.3.1 Request packet transmission within the request interval

In the request interval, iWPTN-B sends an RR packet to iWPTN-D. Based on this, the iWPTN-D receiving the RR packet determines whether to transmit the response packet during the response period. iWPTN-B may allow the iWPTN-D group to transmit during the response interval.

6.2.3.2 Response packet transmission within the response interval

iWPTN-D selected by iWPTN-B can transmit a response packet in the response interval. When iWPTN-D transmits the response packet in the response interval, iWPTN-B that received the response packet transmits the RA packet. The iWPTN-D that has not received the RA packet transmits a response packet to each time slot until it receives the RA packet from iWPTN-B.

6.2.3.3 Wireless power transmission within the response interval

The iWPTN-D selected by iWPTN-B receives the WPT during the response interval. After each time slot there is a PSFI for rapid power status update and abnormal situation occurrence. During WPT, if iWPTN-D receives a PS beacon in PSFI, it sends a PSF packet to iWPTN-B informing the updated power state in response to the PS beacon in PSFI. If an abnormal situation is detected by iWPTN-B, all iWPTN-Ds are notified to PSFI by iWPTN-B. If iWPTN-D recognizes the error by receiving the PS beacon, it waits until it receives a request from iWPTN-B.

6.2.3.4 Data packet transmission within the autonomous section

The autonomous section starts when iWPTN-D does not receive power and does not transmit a response packet during a certain time interval, and this interval is maintained until iWPTN-B transmits an RR packet. In the autonomous period, iWPTN-D can transmit data without request of iWPTN-B.

6.2.3.5 Wireless power transmission within the autonomous section

The autonomous interval begins when all PSF packets from iWPTN-D considered in the last time slot of all response intervals are acknowledged, and this interval is maintained until iWPTN-B transmits an RR packet. In the autonomous period, iWPTN-D can transmit an EPTq packet without request of iWPTN-B. When iWPTN-B receives EPTq packet, iWPTN-B transmits EPTs packet in response to EPTq packet and then provides WPT for a certain time.

6.3 Physical Elements

The physical elements of iWPTN are divided into iWPTN-B and iWPTN-D, and all iWPTN-D are connected to iWPTN-B (that is, the central connection device). The basic component node is divided into iWPTN-B and iWPTN-D depending on the role. iWPTN-B manages the entire iWPTN, and only one iWPTN-B exists in one network. iWPTN-B manages iWPTN-D by transmitting an RR packet. iWPTN-D shall transmit a response packet according to the management of iWPTN-B. iWPTN can be configured as shown in Fig.

6.3.1 iWPTN-B

iWPTN-B is the node that manages the iWPTN; Only one iWPTN-B exists in one network and manages and controls WPTN-D by RR packets.

6.3.2 iWPTN-D

iWPTN-D is a node present in the iWPTN (excluding iWPTN-B), and there can be up to 65,519 iWPTN-Ds per network. iWPTN-D transmits a response packet according to the RR packet transmitted by iWPTN-B.

6.4 Address Elements

To identify iWPTN-D, iWPTN uses an address system such as iWPTN ID, UID, group ID, node ID and charging ID.

6.4.1 iWPTN ID

The iWPTN has a unique ID for identifying the network to other networks; This value can be duplicated with other iWPTNs and remains as long as iWPTN exists. This value is defined by the user to identify the network.

6.4.2 UID

The UID is a unique identifier consisting of 64 bits; It consists of the group ID, the IC manufacturer code, and the serial number of the IC manufacturer. iWPTN-D is identified by the UID.

7 shows the UID structure.

6.4.3 Group ID

iWPTN-D can be grouped by application. The Group ID is an identifier for iWPTN-Ds grouped in the network. iWPTN-B can request a response to a specific iWPTN-D group to reduce packet collisions. Some group IDs are specified as shown in Table 1. This value is defined by the user to identify the group.

[Table 1] Reserved group ID

6.4.4 Node ID

The Node ID is an identifier used instead of a UID to identify the node, and has a 16-bit address assigned by iWPTN-B. Some node IDs are specified as shown in Table 2.

[Table 2] Reserved node ID

6.4.5 WPT ID

WPT ID is the ID used during WPT. This ID has an 8-bit address assigned by iWPTN-B for fast communication during WPT. This ID may be assigned to iWPTN-D during the request interval immediately before the WPT of the response interval. Some WPT IDs are specified as shown in Table 3.

[Table 3] Reserved charging ID

7 Network Status

7.1 General

In iWPTN, iWPTN-D can be enabled in network configuration, network connection, response transmission, data transmission, network separation, network release and wireless power transmission.

7.2 Network Configuration

iWPTN-B configures the network by sending a request packet to iWPTN-D in the request interval. The request packet includes an iWPTN ID so that iWPTN-D can identify the network to which it is connected. The minimum interval of the network means while iWPTN-B exists, and consists of only the request interval and the autonomous interval.

7.3 Network connection

When iWPTN-B transmits an ARq packet in the request interval, iWPTN-D checks the received packet and transmits an ARs packet to iWPTN-B in the response interval if the packet is an ARq packet for a desired iWPTN. iWPTN-B receives the ARs packet and transmits the ARA packet to iWPTN-D. The network connection of iWPTN-D is completed upon receipt of the ARA packet from iWPTN-B.

7.4 Disconnecting the Network

The iWPTN-D connected to the iWPTN may be separated by the request of iWPTN-B or by itself. iWPTN-B can transmit DaRq packets to iWPTN-D for forced separation according to current network conditions. In case of spontaneous separation by shutdown or deviation from network area, iWPTN-B can know the connection status of iWPTN-D by response of ASRq from iWPTN-B.

7.5 Data Transfer

When iWPTN-B sends a DRq packet to iWPTN-D in the request interval, iWPTN-D sends DRs packet to iWPTN-B according to the requested data type. Upon receiving the DRs packet, iWPTN-B sends the DRA packet to iWPTN-D, and when iWPTN-D receives the DRA packet, the data transmission is completed.

7.6 Wireless Power Transmission

When iWPTN-B sends the PTRq packet to the iWPTN-D in the request interval, iWPTN-D sends the PTRs packet in the response interval. Based on information in the PTRs packet, iWPTN-B schedules time slots for WPT and transmits PTS packets containing scheduling information to the request interval. iWPTN-D receives WPT from iWPTN-B in the response interval according to the scheduling order. During each time slot a WPT may be provided for one iWPTN-D or group. After each iWPTN-D or group receives the WPT, there is a PSFI for fast power status update. When iWPTN-D receives a PS beacon in PSFI from iWPTN-B, it sends a PSF packet only when iWPTN-B requests a packet. After confirming the PSF packet, iWPTN-B provides WPT to iWPTN-D of the next slot. During WPT, if iWPTN-B detects an error, it stops WPT. When the PSFI is started, iWPTN-B notifies other iWPTN-D of the detection of the error by sending a PS beacon. When iWPTN-B receives the last iWPTN-D in the last time slot of the response interval or the PSF packet from the last group, WPT is completed.

7.7 Battery-out

When the iWPTN-D in the battery discharge state enters the iWPTN, power is received during the response period even if it is not considered in the scheduling. After receiving the power required to perform the basic functions of the MFC, it stops receiving power. During the autonomous period, additional power is received by sending a BPTRq packet. When iWPTN-D receives power above the threshold, it stops receiving power and waits for a request interval to join iWPTN.

7.8 Network Off

iWPTN release is classified into normal release by request of iWPTN-D and abnormal release by unexpected situation. Normal release refers to releasing the network by sending a DaRq packet to all iWPTN-D by iWPTN-B's decision. Abnormal release refers to a shutdown of the iWPTN-B or a deviation from the network area.

7.9 iWPTN node status

The iWPTN node state includes the iWPTN-B state and the iWPTN-D state. Specifically, the iWPTN-B state can be divided into a standby state, a packet analysis state, a packet generation state, and a power transfer state, and the iWPTN-D state A packet analysis state, a packet generation state, a mute state, and a power reception state (state transition state), a power saving state, a sleep state, an activation state, a standby state, and a power receiving state.

7.9.1 iWPTN-B Status

The iWPTN-B status is set to standby status when the power is turned on. In the idle state, when the COMM system instructs the RR packet transmission or when the superframe starts, the iWPTN-B state is in the packet generation state and iWPTN-B sends the RR packet to iWPTN-D. The next iWPTN-B state returns to the D wait state (see route 4 in FIG. 8). When iWPTN-B receives a packet (response or data packet) from iWPTN-D, the iWPTN-B state is in packet analysis state during carrier detection in the wait state (see path 1 in FIG. 8). If the destination ID of the received packet is the same as the node ID of iWPTN-B, the iWPTN-B state is set to the packet generation state, and the iWPTN-B generates the RA or DA packet in the packet generation state and sends it to iWPTN-D 8). Next, the iWPTN-B state returns to the standby state (see route 4 in Fig. 8). On the other hand, if there is an error in the data packet, the iWPTN-B state immediately returns to the standby state (see route 3 in FIG. 8). In the packet analysis state, if there is an error in the received response packet, or if the destination ID of the received response packet does not correspond to the node ID of iWPTN-B, iWPTN-B regenerates the RR packet in the packet generation state, And returns to the standby state (see route 2 in Fig. 8). If this failure is repeated, the operation of the packet analysis state is repeated as many times as necessary (up to N times). In the (N + 1) th operation, the state of iWPTN-B returns from the packet analysis state to the standby state (see route 2 in FIG. 8).

With respect to WPT, when the superframe starts, the iWPTN-B state becomes the packet generation state, and the PTRq packet is sent. After the packet is sent, the state returns to the stand-by state (see route 4 in FIG. 8). Once iWPTN-B receives the PTRs packet, it enters the packet analysis state (see path 1 in FIG. 8). After the packet is confirmed, a packet is generated and a PTS packet including the scheduling information is generated (see route 5 in FIG. 8). After sending the PTS packet, the iWPTN-B state becomes the power transfer state for providing WPT to the first scheduled iWPTN-D or group (see path 5 in FIG. 8 for the description below). When the PSFI is started, the iWPTN-B state returns from the power transfer state to the packet generation state. PSFI is initiated and the PS beacon is transmitted to all the iWPTN-Ds, and then it is in the standby state for receiving the PSF packets from the iWPTN-D. Upon receiving the PSF packet, it returns to the packet analysis state. Upon confirming the PSF packet, it becomes a power transmission state for providing WPT to the next iWPTN-D or group. Thus, the path from the power transmission state to the packet analysis state is repeated until all the iWPTN-D receive the WPT. If the PSF packet is checked in the packet analysis state, the PWR system returns to the standby state when it instructs to terminate the process. If an error occurs, it returns to the wait state. In the battery discharge state, the BPTRq packet is received from the iWPTN-D, and the iWPTN-B goes from the packet analysis state to the packet generation state. After sending the BPTRs packet, the iWPTN-B state becomes the power transmission state. When the MFC system commands or the superframe starts, the RR packet is generated in the packet generation state (see route 4 in FIG. 8). The iWPTN-B state diagram is shown in Fig.

7.9.2 iWPTN-D Status

The iWPTN-D state goes into a power-saving state when the power is turned on. When the wake-up sequence is detected in the power save state, it is activated (see route 1 in Fig. 9 for the following description). The wakeup sequence is defined in 8.1 below. When the iWPTN-D receives the RR packet, the iWPTN-D state enters the packet analysis state, and the iWPTN-D analyzes the received RR packet. If the destination ID of the RR packet matches the iWPTN-D ID (group ID and node ID), the iWPTN-D state becomes the packet generation state, iWPTN-D sends the response packet to iWPTN-B, (See route 3 in Fig. 9). Otherwise, it returns to the power saving state (see route 2 in FIG. 9).

During the carrier detection in the standby state, the iWPTN-D state enters the power save state upon receipt of its RA packet (see route 1 in Fig. 9), or when the MFAN-N receives the RA packet from another node (See route 2 in Fig. 9). When the slot number is not allocated in the standby state and the timeout period ends, the iWPTN-D state is set to the power saving state (see path 1 in FIG. 9), and the slot number is allocated and the timeout period is ended ) The iWPTN-D state is in a packet generation state (see route 1 in FIG. 9). However, when the slot number is allocated and the (N + 1) th timeout period ends, the power saving state is entered (see route 1 in FIG. 9). Slot number is assigned, and if the iWPTN-D does not receive the RA packet during the timeout period, it enters the packet generation state from the standby state (see route 1 in FIG. 9). The next iWPTN-D regenerates and retransmits the response packet with iWPTN-B, and the iWPTN-D state becomes the packet generation state in the waiting state (see route 3 in FIG. 9). The retransmission of the response packet is repeated as many times as necessary (up to N times). In the (N + 1) th timeout period, the power saving state is entered in the standby state (see route 1 in FIG. 9). When the iWPTN-D receives the RR packet while performing the carrier detection in the waiting state, it enters the packet analysis state (see route 1 in Fig. 9).

When a system interrupt occurs in a power save state, the iWPTN-D state is brought into an active state (see route 3 in FIG. 9 for the description below). When iWPTN-D receives data from the system, the packet generation state is established. Next, iWPTN-D generates and sends a data packet to iWPTN-B, and the iWPTN-D state is put into a standby state. When iWPTN-D receives the DA packet, it returns to the power saving state. Otherwise, iWPTN-D retransmits data up to N times and returns to the standby state.

For WPT, when iWPTN-D receives the PTRq packet during the request interval, it enters the packet generation state and generates a PTRs packet in response to the PTRq packet (see route 5 in FIG. 9). After transmitting the PTRs packet during the response interval, it returns to the power saving state. When iWPTN-D receives the PTS packet, it enters the packet analysis state. After confirming the packet, it becomes a power transmission state or an isolation state. If the next time slot is not the WPT sequence for iWPTN-D, the next time slot is switched off from the packet analysis state to not interfere with the other iWPTN-D that will receive the WPT. When PSFI starts, iWPTN-D becomes active. Upon receipt of the PS beacon from iWPTN-B, the packet analysis state is c. On the other hand, if iWPTN-D is the WPT target node in the next time slot, the packet analysis state is changed to the power transmission state. When the power transmission is completed, the mobile station enters a standby state and receives a PS beacon from iWPTN-B. Upon receiving the PS beacon from iWPTN-B, the packet analysis state is established.

In the packet analysis state, if there is a request for a PSF packet, the packet generation state is established, and a PSF packet for quick power state update is generated and sent to iWPTN-B. After the PSF packet is transmitted, if the next time slot is not the WPT sequence for iWPTN-D, it is put in a power cut-off state so as not to interfere with the other iWPTN-D to receive the WPT in the next time slot. Otherwise, it is in a power transmission state for receiving the WPT. This path from the power cutoff state to the packet analysis state is repeated until the response interval for the WPT ends. In this case, the state becomes a waiting state in the packet analysis state.

When the detection of an error is recognized, this path is aborted. For iWPTN-D currently receiving WPT, if the WPT interruption is detected during the current time slot (not after the slot has ended), it is switched to the standby state. Next, when iWPTN-D receives the PS beacon, it enters the packet analysis state. When the PSFI starts, another iWPTN-D that does not receive the current WPT is activated and the packet analysis state is established. By recognizing the PS beacon in the packet analysis state, it recognizes that the error has started and enters the power save state.

When the iWPTN-D is battery discharged, the power saving state is maintained, and a small amount of power for the other scheduled iWPTN-D is collected in the jamming period (see route 4 in FIG. 9 for the following description). When iWPTN-D detects a wake-up 2 signal, it enters a power saving packet analysis state and analyzes the PS beacon. After checking the PS beacon, it returns to the power saving state. When the response interval ends, the power save packet generation state is entered and a BPTRq packet is generated. After sending the packet, it returns to sleep state and waits for the BPTRs packet. When a wake-up 2 signal is detected, it enters a power saving packet analysis state and analyzes the BPTRs packet. After confirming the packet, it enters the power transmission state and receives the WPT in the autonomous section. The iWPTN-D state diagram is shown in Fig.

8 Physical layer (PHY layer)

8.1 Physical layer frame format (PHY layer frame format)

8.1.1 General

This section describes the physical layer frame format. As shown in FIG. 10, the PHY layer format includes three components: a preamble, a header, and a payload. When transmitting a packet, the preamble is transmitted first, followed by the header, and finally the payload is transmitted. The LSB is the first transmitted bit.

8.1.2 Preamble

As shown in Fig. 11, the preamble consists of two parts: a wake-up sequence and a synchronization sequence. The 8-bit wakeup sequence can be divided into two types: one for general MFC and one for general WPT. The wakeup 1 sequence for MFC consists of [0000 0000] and the wakeup 2 sequence for WPT consists of [1111 1111]. The 16-bit synchronization sequence consists of a 12-bit [000000000000] sequence and a 4-bit [1010] sequence. The wakeup 1 signal is included only in the preamble of the response packet of the request interval and the wakeup 2 signal is included only in the preamble of the PS beacon of the request interval and the BPTRs packet of the autonomous interval. The synchronization sequence is used for packet acquisition, symbol timing and carrier frequency measurement.

The preamble is encoded using type 0 as defined in Section 7.1.3. The wakeup sequence is modulated with ASK, and the synchronization signal is modulated with BPSK.

8.1.3 Header

The header is included after the preamble to convey information about the payload. The header format is defined in ISO / IEC 15149.

8.1.4 Payload

The payload format is defined in ISO / IEC 15149.

8.1.5 Frame Check Sequence (FCS)

The payload uses CRC-16 FCS to check for errors. This sequence is defined in ISO / IEC 15149.

8.2 Coding and modulation

8.2.1 Coding

The MFC between iWPTN-B and iWPTN-D uses Manchester coding or NRZ-L coding. In addition, scrambling for coded data is used. Such encoding and scrambling are defined in ISO / IEC 15149.

8.2.2 Data rate and encoding type

The data rates and encodings for the preamble / header and payload are defined in ISO / IEC 15149.

8.2.3 Modulation

The MFC between iWPTN-B and iWPTN-D uses ASK modulation or BPSK modulation. The details of the modulation are defined in ISO / IEC 15149.

8.2.4 Coding and Modulation Processes

The encoding and modulation process for preamble, header and payload is defined in ISO / IEC 15149.

9 MAC layer frame format

9.1 General

The MAC frame of the iWPTN consists of a frame header and a frame body. The frame header has information between iWPTN-D, and the frame body has data for transmission between iWPTN devices.

9.2 Frame Format

All MAC frames are composed of a frame header and a frame body as shown in FIG.

1) frame header: iWPTN ID, frame control, source node ID, destination node ID, and sequence number. The frame header can be used for data transmission.

2) Frame Body: consists of payload including data transmitted between iWPTN devices and FCS for checking errors in payload.

9.2.1 Frame Headers

The frame header has information for transmission / reception and flow control of the frame.

9.2.1.1 iWPTN ID

As shown in FIG. 12, the iWPTN ID field consists of 1 byte and is used to identify the network.

9.2.1.2 Frame Control

The frame control field consists of a frame type, an acknowledgment policy, a first fragment, a last fragment and a protocol version, which are shown in FIG.

The description of each field is as follows.

1) The frame type field consists of 3 bits; See Section 8.3 for frame type details.

2) The acknowledgment policy field consists of two bits; If the received frame is a confirmation frame, this indicates the policy of the acknowledgment frame, otherwise it indicates the policy of the confirmation frame for the destination node.

a) No acknowledgment: The destination node does not acknowledge the transmitted frame, and the source node considers the transmission successful, regardless of the transmission result. This method is used in frames transmitted in 1: 1 or 1: N, and transmission does not require acknowledgment.

b) Single acknowledgment: The destination node receiving the frame sends a confirmation frame to the source node in response to SIFS. This acknowledgment policy can only be used for 1: 1 transmissions.

c) Multiple Identification: The destination node that receives the frame sends a confirmation frame in response to SIFS to the multiple source nodes. This acknowledgment policy can only be used for 1: N transmissions.

d) Data confirmation: The destination node that received the data frame sends a confirmation frame to the source node in response to SIFS. This acknowledgment policy can only be used for 1: 1 transmissions.

3) The first fragment field is 1 bit; '1' indicates that the frame is the start of a request, response, or data packet from a higher layer, and '0' indicates that it is not a start.

4) The last fragment field is 1 bit; A '1' indicates that the frame is the end of the request, response, or data packet from the upper layer, and '0' indicates that it is not the last.

5) The protocol version field consists of 2 bits, and the size and position are fixed regardless of the protocol version of the system. The current value is 0, which increases by 1 each time a new version is issued. When a node receives a packet of a higher version than its own, it discards it without notifying the originating node.

6) Reserved: Reserved for future use.

9.2.1.3 Sequence Number

The sequence number field has a length of 8 bits and indicates a frame sequence number. In the data frame, an incremental counter is assigned a sequence number between 0 and 255 for each packet, and when it reaches 255, it returns to 0 again.

9.2.2 Frame body

The frame body has a variable length and consists of a payload and an FCS. Each payload has a different format depending on the frame type of the frame control field, and the FCS is used to identify errors in the frame.

9.2.2.1 Payload

The payload has data transmitted between iWPTN-B and each iWPTN-D, and the length is a variable value between 0 and 247.

9.2.2.2 Frame check sequence

The FCS is 16 bits long and is used to verify that the frame body was received without error. This is generated using the following 16th order generator polynomial.

9.3 Frame Types

The frame type is defined as four types of request frame, response frame, data frame, and confirmation frame.

[Table 4] Frame type value

9.3.1 Request frame

The request frame is used when iWPTN-B sends an RR packet to a specific iWPTN-D in iWPTN in the request interval or broadcasts information to all iWPTN-D. The request frame format is shown in FIG. It should be noted that the confirmation policy when broadcasting the RR packet is not checked. The RR packet includes ARq, DaRq, ARsRq, DRq, PRRq, and the like.

9.3.2 Response frame

The response frame is used when iWPTN-D sends a response packet to the request of iWPTN-B in the response interval. iWPTN-D sends a response packet a certain number of times until a confirmation packet is received within the response interval.

The response frame format is shown in Fig.

9.3.3 Data Frame

The data frame is used when iWPTN-D sends data to iWPTN-B without request of iWPTN-B in autonomous section.

The data frame format is shown in Fig.

9.3.4 Confirmation frame

The confirmation frame includes an RA frame and a DA frame. When iWPTN-B transmits an RR packet, iWPTN-D that receives the RR packet transmits the response packet, and iWPTN-B that receives the response packet transmits the RA packet. The payload of the acknowledgment frame contains the acknowledgment data of the received acknowledgment packet. After receiving the response packet, iWPTN-B responds to iWPTN-D by sending an RA packet after SIFS of the response interval. The DA frame is a confirmation frame for the received data packet. iWPTN-B responds to iWPTN-D that transmitted the data packet by sending the DA packet after SIFS of the autonomous section.

The response confirmation frame format is shown in Fig. 17, and the data confirmation frame format is shown in Fig.

As shown in Fig. 18, a DA frame is composed of a frame header and a frame body. If the destination node ID is a node ID that does not join at 0xFFFE, the UID field is included.

9.4 Payload Format

The payload format includes a request frame, a response frame, a data frame, and a confirmation frame.

9.4.1 Request frame

As shown in FIG. 19, the payload of the request frame consists of a group ID, a request code, a length, and one or more request blocks. The group ID of 0xFF indicates that iWPTN-B requests a response to all iWPTN-D groups.

9.4.1.1 Group ID

The group ID field consists of one byte and is used to send an RR packet to a specific group. See Section 6.4.3 for details of group ID.

9.4.1.2 Request Code

The request code of the payload of the request frame is shown in Table 5.

[Table 5] Payload request code of request frame

9.4.1.3 Length

The length field is composed of 1 byte and represents the total length of the request field, and the length field value is variable according to the length and the number of the request block.

9.4.1.4 Request Block

The data format of the request block is configured differently according to the request code, and one or more request blocks may be included in the payload of the request frame.

The data format of each request block is as follows.

1) Connection request

The block format of ARq is shown in Fig. 20, and is composed of an 8-byte UID mask. This UID mask can be used to implement a binary search algorithm.

2) Separation request

The block format of DaRqD is shown in Fig. The first 2 bytes are the node ID of iWPTN-D for DaRq, and the next 1 byte is the slot number used in the response interval. When the node ID is 0xFFFF, it indicates that DaRq is transmitted to all iWPTN-D of the group ID.

3) Request a connection status

The block format of ASRq is shown in FIG. The first two bytes are the node ID of iWPTN-D for ASRq. When the node ID is 0xFFFF, it indicates that ASRq is requested to all iWPTN-Ds of the group ID.

4) Data request

The block format of DRq is shown in FIG. The first two bytes are the node ID, the next one byte is the slot number, and the last L byte is the received data type. The data type depends on the application product. For WPT, one of the data types is charging information of iWPTN-D, such as remaining battery power, received power level, desired power level, battery charging and so on.

5) Group ID setup request

The block format of GSRq is shown in FIG. The first two bytes are the node ID, the next one byte is the slot number, and the last byte is the group ID to be set up.

6) Power transmission request

The block format of PTRq is shown in FIG. The first two bytes are the node ID of iWPTN-D for PTRq. If the node ID is 0xFFFF, it indicates that PTRq is requested to all iWPTN-D of the group ID. The next 1 byte is the slot number. The next one bit is a request for the remaining power of the battery, the next one bit is a request for the power consumption rate, and the next one bit is a request for the received power level. 5 bits are reserved for future use, and the last L bytes are data related to iWPTN power reception scheduling.

7) Power transmission start request

The block format of the PTS is shown in Fig. The first 1 byte is the WPT ID of iWPTN-D for the PTS. If the node ID is 0xFF, the PTS is requested to all iWPTN-D. The next 1 byte is the slot number, and the last L byte is data related to iWPTN power reception scheduling.

9.4.2 Response frame

The payload format of the response frame has response information for the request of iWPTN-B. The response frame payload is shown in Fig. The first byte is the group ID, the second byte is the response code, the third byte is the response data length (L), and the next byte is the response data.

9.4.2.1 Group ID

The group address field consists of one byte and is used to send RR packets to a specific group. For details of the group ID, see 6.4.3. See section.

9.4.2.2 Response Codes

The response code types are shown in Table 6.

[Table 6] Response code of response frame payload

9.4.2.3 Length

The length field consists of one byte and represents the length of the response data; This is variable depending on the response data.

9.4.2.4 Response Data

The response data is divided into ARs, DaRs, ASRs, DRs, GSRs, and PTRs. The response data format is as follows.

1) Connection response

The block format of ARs is as shown in FIG. The ARs data consists of an 8-byte UID.

2) Separation response

The block format of DaRs is as shown in FIG. DaRs data consists of 8-byte UIDs.

3) Connection status response

Association status response

The block format of the ASRs is as shown in FIG. The ASRs data consists of an 8-byte UID and a 1-byte status value.

The state values are shown in Table 7 below.

[Table 7] Association status check value

4) Data response

The block format of DRs is as shown in FIG. The DRs data consists of L bytes of requested data. For WPT according to the requested data type, the data is charging information of iWPTN-D such as remaining battery level, received power level, desired power level, battery discharge rate and the like.

5) Group ID setup response

The block format of GSRs is as shown in FIG. The GSRs data consists of an 8-byte UID with the changed group ID and a 1-byte changed group ID.

6) Power transmission response

The block format of the PTRs is as shown in FIG. The PTRs data are 2 bytes for the remaining power of the battery and 2 bytes for the received power level and reserved L bytes for later use.

9.4.3 Data Frame

The data frame payload contains the data to be transmitted. The data frame payload is composed of 8 bytes of UID and L bytes of data as shown in FIG.

9.4.4 Confirmation Frame

The confirmation frame payload has data for the received response packet. The RA payload format is shown in Fig. The first byte is the group ID, the second byte is the acknowledgment code, the third byte is the length (L), and the next L byte is the acknowledgment block.

9.4.4.1 Group ID

The group ID field consists of one byte and is used to send RR packets to a specific group. See Section 6.4.3. For the details of the group ID.

9.4.4.2 Response Verification Code

The response acknowledgment code types are shown in Table 8.

[Table 8] Response confirmation code

9.4.4.3 Length

The length field consists of one byte; This indicates the length of the acknowledgment data and is variable depending on the acknowledgment data.

9.4.4.4 Response Verification Block

The acknowledgment block is divided into ARs check, DaRs check, ASRs check, DRs check and GSRs check. The block format of the acknowledgment is as follows.

1) Check the connection response

The block format of the ARs confirmation is as shown in FIG. The first 8 bytes are the UID, and the next 2 bytes are the assigned node ID. The assigned node ID of 0xFFFE is the address of the un-joined node, which means that ARq is rejected.

2) Confirm separation response

The block format of the DaRs confirmation is as shown in FIG. The first 8 bytes are the UID, and the next 2 bytes are the node ID. The allocated node ID is used when the separation is not permitted, and when the separation is permitted, the non-joined node ID of 0xFFFE is recorded.

3) Check the connection status response

The block format of the ASRs confirmation is as shown in FIG. The ASRs confirmation block consists of an 8-byte UID.

4) Check data response

The block format of the DRs confirmation is as shown in FIG. The first two bytes are the node ID, and the next one byte is reserved.

5) Confirm the group ID setup response

The block format of the GSRs confirmation is as shown in FIG. The GSRs confirmation block consists of an 8-byte UID and a 1-byte status check value.

Group ID setup status values are shown in Table 9.

[Table 9] Group ID set-up status value

9.5 PSFI Frame Format

When iWPTN-B provides a WPT, there is a PSFI in the response interval. The PSFI is initiated when each time slot for a particular iWPTN-D or WPT for a group ends and remains until iWPTN-B receives all PSF frames from the required iWPTN-D. The PSFI frame format has a short and simple structure in order to secure sufficient WPT time.

9.5.1 PS Beacon Format

When the PSFI starts, iWPTN-B sends a PS beacon for rapid power status updates and abnormal conditions. The request frame format is shown in Fig.

9.5.1.1 Slot Number

It represents the current time slot number and is one byte.

9.5.1.2 Frame Control

The frame control consists of a frame type and a PSF policy. 4 bits are reserved for future use. The format is shown in Fig.

1) Frame type

The frame type field is composed of 3 bits. The frame type is defined as two types, a request frame and a response frame.

[Table 10] Frame type value

2) PSF policy

The PSF policy field consists of two bits. The PSF policy is defined as two types of response frame transmission policy and no transmission policy.

[Table 11] PSF policy value

3) On-going policy

The in-progress policy consists of 1 bit. If the value is 1, WPT is provided in the next time slot, otherwise WPT is stopped.

9.5.1.3 WPT ID number

This represents the number of the WPT ID listed in the frame body.

9.5.1.4 WPT ID

iWPTN-B selects a specific iWPTN-D or group for the PS beacon response. In PS beacons, the WPT ID is used to reduce the length of the beacon and simplify the beacon structure. See Section 6.4.5 for details of the WPT ID.

9.5.1.5 Frame Check Sequence

The FCS is 8 bits long and is used to verify that the frame body was received without error. This is generated using the following 8th order generator polynomial.

9.5.2 PSF Frame Format

After receiving the PSF request in the PS beacon from iWPTN-B, the selected iWPTN-D sends the PSF frame as a response to iWPTN-B. The PSF frame format is shown in Fig.

9.5.2.1 Slot Number

This indicates the current time slot number, which is one byte.

9.5.2.2 Frame Control

The frame control field consists of a frame type. Five bits are reserved for future use. The format is shown in Fig.

1) Frame type

The frame type field is composed of 3 bits. The frame type is defined as two types, a request frame and a response frame.

[Table 12] Frame type value

9.5.2.3 WPT ID

See Section 6.4.5.

9.5.2.4 Battery level

When the iWPTN-B requests battery information, the iWPTN-D sends the remaining battery power information. 8 bits are reserved for battery information.

9.5.2.5 Frame check sequence

The FCS is 8 bits long and is used to verify that the frame body was received without error. This is generated using the following 8th order generator polynomial.

9.6 Battery discharge frame format of WPT

When iWPTN-D battery is discharged, iWPTN-D requests WPT to iWPTN-B in autonomous section without request of iWPTN-B. The frame format during battery discharge is the shortest and simplest due to the battery condition.

9.6.1 BPTRq Frame Format

When the autonomous section starts, the battery discharge iWPTN-D sends a BPTRQ frame for the WPT request. The frame consists of only one byte [00000000]. The BPTRs frame format is shown in Fig.

9.6.2 BPTRs Frame Format

After receiving the BPTRq frame from iWPTN-D, iWPTN-B transmits the BPTRs frame to inform the length of the WPT interval in the autonomous section. The BPTRs frame format is shown in Fig.

10 MAC Layer Function

10.1 General

To manage the iWPTN, the connection, disconnection, and ASC processes for iWPTN-D are considered in the MAC layer of iWPTN. Data can be sent in the response interval or the autonomous interval. In addition, a group ID setup function is provided to manage the iWPTN-D group.

10.2 Connecting and disconnecting the network

iWPTN-D must first be associated with iWPTN to communicate with iWPTN-B. Each iWPTN-D searches for a predetermined iWPTN and associates it with the discovered iWPTN. If iWPTN is not searched, any iWPTN-D may be made to iWPTN-B by the user of the application. (Ie setting up a new iWPTN will cause the new iWPTN-B to periodically send a request packet). However, after the iWPTN is set, the node can maintain its state as iWPTN-B or iWPTN-D depending on its role. In this case, there is only one available channel, so if there is already set iWPTN, network setting is canceled.

10.2.1 Connection

In the request interval, iWPTN-B sends the ARq packet to iWPTN-D which has not joined. iWPTN-D transmits the ARs packet to iWPTN-B in the response interval. When iWPTN-B determines whether or not iWPTN-D is to be connected to iWPTN, it notifies the result through ARA packet. If the connection is granted, the assigned node ID is included in the ARA packet, and if the connection is rejected, the unjoined node ID 0xFFFE is recorded. If WiWPTN-D does not receive an ARA packet due to an ARA packet error, or PTN-B does not receive an ARs packet, ARq packets are sent to every superframe until an ARA packet is received without error from all selected iWPTN- Continue to send. The connection process for iWPTN-D is completed when iWPTN-D receives the ARA packet from iWPTN-B.

The connection process is shown in Fig.

10.2.2 Isolation

When iWPTN-B sends a DaRq packet to iWPTN-D connected to iWPTN in the request interval, iWPTN-D sends DaRs packet to iWPTN-B in the response interval. iWPTN-B determines whether iWPTN-D is to be separated from iWPTN, and notifies the result through DaRA packet. When the separation is permitted, the node ID of the DaRA packet is recorded with the non-joined node ID 0xFFFE, and if the separation is rejected, the assigned node ID is recorded. If the iWPTN-D does not receive the DaRA packet due to the DaRA packet error or if the iWPTN-B does not receive the DaRs packet, iWPTN-D continuously retransmits the DaRs packet in every superframe until receiving the DaRA packet. The separation is completed when iWPTN-D receives a DaRA packet from iWPTN-B.

The separation procedure is shown in Fig.

10.2.3 Checking Connection Status

When iWPTN-B sends an ASRq packet to iWPTN-D connected to the request interval, iWPTN-D sends ASRs packet to iWPTN-B in the response interval. iWPTN-B Check the connection status of iWPTN-D to iWPTN and send ASRA packet. If iWPTN-D does not receive an ASRA packet due to a packet error or iWPTN-B does not receive an ASRs packet, iWPTN-D transmits ASRs packets continuously in every time slot until it receives an ASRA packet. The connection status check of iWPTN-D is completed when iWPTN-D receives ASRA packet from iWPTN-B.

The procedure of checking the connection status is shown in Fig.

10.3 Data Transmission

In iWPTN, data can be transmitted in the response interval or the autonomous interval. Data is transmitted in the response interval by the request of iWPTN-B or in the autonomous interval without the request of iWPTN-B.

10.3.1 Transmission in response interval

When iWPTN-B transmits a DRq packet to iWPTN-D connected to iWPTN in the request interval, iWPTN-D transmits DRs packet in the response interval. iWPTN-B receives a DRs packet from iWPTN-D, and then sends a DRA packet. If iWPTN-D does not receive a DRA packet due to a packet error or if iWPTN-B does not receive a DRs packet, iWPTN-D transmits DRs packet continuously in every time slot until receiving DRA packet.

The data transmission procedure in the response interval is completed when iWPTN-D receives the DRA packet from iWPTN-B.

The data transfer procedure in the response interval is shown in FIG.

10.3.2 Transmission in autonomous section

The autonomous period starts when iWPTN-D does not send a response packet during the timeout period, and this interval is. and remains until iWPTN-B transmits an RR packet. iWPTN-D can transmit data without request of iWPTN-B during autonomous period. When a system interruption occurs, iWPTN-D can transmit data without request of iWPTN-B. If iWPTN-D does not receive DA packet or iWPTN-B does not receive data packet due to packet error, iWPTN-D continuously transmits data packet until it receives DA packet. The data transmission procedure in the autonomous section is completed when iWPTN-D receives the DA packet from iWPTN-B.

The data transfer procedure in the autonomous section is shown in FIG.

10.4 Setting up the group ID

When iWPTN-B sends GSRq packet to iWPTN-D in the request interval, iWPTN-D sends GSRs packet in response interval. iWPTN-B confirms the group ID setup status of iWPTN-D and transmits the GSRA packet.

The group ID setup procedure is shown in FIG.

10.5 Wireless power transmission

When iWPTN-B sends a PTRq packet to iWPTN-D, iWPTN-D sends a PTRs packet to iWPTN-B. iWPTN-B performs WPT scheduling with received data in the PTRs packet. iWPTN-B broadcasts a PTS packet having the calculated scheduling information to a desired iWPTN-D. When iWPTN-D receives the PTS packet, it follows the scheduling sequence. iWPTN-B provides WPT to iWPTN-D scheduled in the first order. During WPT, the other iWPTN-D is powered off to increase power transfer efficiency. After receiving the power of the first iWPTN-D, iWPTN-B generates a PS beacon in PSFI and transmits it to all iWPTN-D. When the PSFI is started, the other iWPTN-D is activated to receive the PS beacon. When iWPTN-D receives the PS beacon, iWPTN-D selected by iWPTN-B generates a PSF packet and sends it to iWPTN-B. After verifying the PSF packet from the selected iWPTN-D, iWPTN-B starts the WPT for the second iWPTN-D. When iWPTN-B detects an error in WPT, it stops WPT, iWPTN-D recognizes WPT interrupt, and then becomes active. When PSFI is started, iWPTN-B sends a PS beacon to notify other iWPTN-D of error detection. This process is repeated until all desired iWPTN-D receives power, and iWPTN-B receives the PSF packet from iWPTN-D in the last time slot of the response interval.

The wireless power transmission procedure is shown in FIG.

10.6 Battery discharge

If iWPTN-D is battery discharged, WPT is received from iWPTN-B even if the considered node is not available. The battery discharge, iWPTN-D, is divided by iWPTN-B into a small fraction of the power to be delivered to its original destination, iWPTN-D. When the current time slot expires, iWPTN-B transmits a PS beacon. The original destination iWPTN-D transmits a PSF packet in response to the PS beacon and enters a power saving state. On the other hand, the battery discharge iWPTN-D keeps the power saving state even after receiving the PS beacon because the battery power is low. When the autonomous section starts, the emergency iWPTN-D enters the power-saving packet generation state and transmits the BPTRq packet. When iWPTN-B receives the packet, it sends the BPTRs packet in response and provides the WPT with the emergency iWPTN-D.

The procedure of battery discharge is shown in Fig.

11 Air interface

11.1 Frequency

The center frequency (fc) of the iWPTN is between 80 kHz and 400 kHz; The maximum tolerance can be ± 20 ppm at 88 kHz, 128 kHz, and 370 kHz.

11.2 Signal waveform

56 shows the envelope waveform, and the envelope parameters are defined in Table 13. The amplitude in Table 13 represents the amplitude of the envelope. The envelope amplitude varies within 10% of the amplitude from the negative variance Mi to the positive variance Mh. tr and tf represent the envelope increase time of the amplitude from 10% to 90% and the envelope decrease time of the amplitude from 90% to 10%, respectively. The bit interval (Tbit) varies with the data rate, and tr and tf can not exceed 30% of Tbit.

[Table 13] BPSK envelope parameters

BPSK modulation is used for transmission between iWPTN-B and iWPTN-D. The transmission signal is BPSK modulated according to the envelope defined in this section, as shown in FIG.

Fig. 57 shows a BPSK-modulated signal, and Fig. 58 shows an ASK-modulated signal.

[Table 14] ASK envelope parameters

11.3 WPT Signal Waveform

Figure 59 shows the waveform of the WPT signal and the envelope parameters are defined in Table 15. For WPT, a common sinusoidal waveform is used because it provides high efficiency for power transmission. The amplitude in Table 15 represents the amplitude of the envelope. The envelope amplitude varies within 10% of the amplitude from the negative variance Mi to the positive variance Mh.

[Table 15] WPT envelope parameters

While the invention has been described in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the appended claims are intended to embrace all such modifications and variations as fall within the true spirit of the invention.

Claims (1)

A communication method of a wireless power transmission system for wireless charging of multiple devices,
The wireless power transmission system includes:
A base station for managing wireless power transmission to the device, charging and disconnecting to and from the devices in the communication area, transmission and reception times of data and wireless power transmission in the wireless power transmission network; And
An apparatus other than the base station constituting the wireless power transmission network, the apparatus including a plurality of nodes that are apparatuses for receiving wireless power from the base station,
The wireless power transmission system performs wireless power transmission and magnetic field communication using one frequency band having a center frequency between 80 kHz and 400 kHz,
A communication method of a wireless power transmission system that performs wireless power transmission and magnetic field communication through a superframe composed of a request period, a response period, and a spontaneous period as a temporal component.

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