TWI796889B - Communication method of centralized wireless powered communication network - Google Patents

Abstract

A communication method of a centralized wireless powered communication network includes the following steps. During a broadcast slot, a base station sends a broadcast packet to plural IoT devices. During plural mini-slots, the IoT devices respectively send the information including the residual energy and the random selection slot to the base station. The mini-slots are subsequent to the broadcast slot. The base station selects one IoT device with the smallest residual energy from the IoT devices as a selected device. When the base station determines that the random selection slot of the selected device is not equal to a current slot, the base station sends a RF charging signal to the selected device during the current slot, such that the selected device harvests the RF energy from the base station. The current slot is after the mini-slots.

Description

Communication transmission method of centralized wireless charging communication network

The present invention relates to a communication transmission method, and in particular to a communication transmission method of a centralized wireless charging communication network.

In an Internet of Things (IoT) network, various IoT devices communicate with each other. Since IoT devices are usually low-power stand-alone devices, it is very important to supplement the energy of IoT devices and extend the running time of IoT devices. Radio frequency (radio frequency, RF) energy harvesting is a convenient and cost-effective solution for providing energy to IoT devices, which harvest energy from RF energy signals transmitted by base stations. However, because half-duplex IoT devices usually contend for the time slot to transmit packets, if the base station transmits RF energy to the IoT device in the same time slot, the IoT device will not be able to collect energy and cause useless charging ( vain charging) and waste radio frequency energy.

The purpose of the present invention is to propose a communication transmission method of a centralized wireless charging communication network, which includes: the base station sends a broadcast packet to a plurality of Internet of Things devices in a broadcast time slot; Sending data including residual power and randomly selected time slots to the base station, the plurality of mini time slots following the broadcast time slot; the base station selects the one with the smallest residual power from the plurality of IoT devices as the first selected device ; and when the base station determines that the randomly selected time slot of the first selected device is not the current time slot, the base station transmits a radio frequency charging signal to the first selected device at the current time slot, so that the first selected device collects radio frequency energy from the base station , the current slot is after the number of mini-slots.

In some embodiments, the above-mentioned communication transmission method further includes: when the base station judges that the randomly selected time slot of the first selected device is the current time slot, the base station selects the one with the second smallest residual power from the plurality of IoT devices as the current time slot. The second selected device; and when the base station judges that the randomly selected time slot of the second selected device is not the current time slot, the base station transmits a radio frequency charging signal to the second selected device at the current time slot, so that the second selected device can start from the base The station collects radio frequency energy.

In some embodiments, the communication transmission method further includes: when the first selecting device determines that the randomly selected time slot of the first selecting device is the current time slot, the first selecting device transmits the packet to the base station in the current time slot.

In some embodiments, the above-mentioned communication transmission method further includes: when one of the plurality of IoT devices determines that the residual power of the plurality of IoT devices is greater than a power threshold and when the plurality of IoT devices When one of the IoT devices has at least one packet in its queue, the one of the plurality of IoT devices randomly selects one of the plurality of time slots as the one of the plurality of IoT devices A time slot is randomly selected, wherein the plurality of time slots follows the plurality of mini-time slots.

In some embodiments, the above-mentioned communication transmission method further includes: when one of the plurality of IoT devices determines that the residual power of the one of the plurality of IoT devices is not greater than a power threshold or when the plurality of IoT devices When one of the IoT devices does not have at least one packet in its queue, the one of the plurality of IoT devices designates a randomly selected time slot of the one of the plurality of IoT devices as not required The specified time slot for sending packets.

In some embodiments, the above-mentioned communication transmission method further includes: when the randomly selected time slot of one of the plurality of Internet of Things devices is the current time slot, one of the plurality of Internet of Things devices at the current time slot and when the randomly selected time slot of one of the plurality of IoT devices is not the current time slot and when the base station transmits a radio frequency charging signal to the plurality of IoT devices in the current time slot When one of them is selected, one of the plurality of Internet of Things devices receives a radio frequency charging signal from the base station to collect radio frequency energy.

In some embodiments, the above-mentioned base station works in a full-duplex transmission mode, and the above-mentioned IoT device works in a half-duplex transmission mode.

In some embodiments, the above-mentioned communication transmission method further includes: the plurality of Internet of Things devices receive broadcast packets from the base station during broadcast time slots to collect radio frequency energy.

In some embodiments, the IoT device uses simultaneous wireless information and power transfer (SWIPT) technology to receive broadcast packets to harvest radio frequency energy.

In some embodiments, the above-mentioned centralized wireless charging communication network is a communication network based on framed slotted ALOHA (framed slotted ALOHA, FSA) protocol.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

Embodiments of the invention are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable concepts that can be implemented in a wide variety of specific contexts. The discussed and disclosed embodiments are for illustration only, and are not intended to limit the scope of the present invention. The terms “first”, “second”, etc. used herein do not specifically refer to a sequence or order, but are only used to distinguish elements or operations described with the same technical terms.

FIG. 1 is a schematic diagram of a communication system of a centralized wireless charging communication network according to an embodiment of the present invention. A plurality of IoT devices 120 ₁ -120 ₆ are located within the coverage of the base station 140 . It should be noted that the number of IoT devices shown in FIG. 1 is just an example, and the present invention is not limited thereto.

In the embodiment of the present invention, the base station 140 works in a full-duplex transmission mode, that is, the base station 140 can send a radio frequency charging signal to the IoT device and receive data packets from the IoT device at the same time. After the base station 140 receives the data packet transmitted by the IoT device, it can further forward the data packet to the network 160 .

In the embodiment of the present invention, in order to reduce system cost, the IoT devices 120 ₁ - 120 ₆ work in half-duplex transmission mode, that is, when a certain IoT device transmits a data packet to the base station 140, the certain IoT device An IoT device cannot receive RF charging signals from the base station 140 to collect energy.

Figure 1 shows an example of energy transfer and packet transfer. For example, as shown by the solid arrow in FIG. 1 , the base station 140 sends a radio frequency charging signal to the IoT device ₁₂₀₃ to enable the IoT device ₁₂₀₃ to collect energy. For example, as shown by the dotted arrow in FIG. 1 , the IoT device ₁₂₀₂ transmits a data packet to the base station 140 .

In an embodiment of the present invention, the IoT devices 120 ₁ -120 ₆ are equipped with radio frequency energy harvesting modules for receiving radio frequency charging signals sent from the base station 140 to harvest energy. Furthermore, the IoT devices 120 ₁ -120 ₆ are equipped with batteries to store the collected energy. In the embodiment of the present invention, the IoT devices 120 ₁ ~ 120 ₆ use the simultaneous wireless information and power transfer (SWIPT) technology, so that when the IoT devices 120 ₁ ~ 120 ₆ receive broadcast packets, the Internet of Things The devices 120 ₁ -120 ₆ can collect radio frequency energy.

Multiple access control (MAC) is very important for IoT devices to transmit data packets and collect energy in the wireless charging IoT network. The framed slotted ALOHA (framed slotted ALOHA, FSA) protocol is quite suitable for IoT devices due to its simplicity, low latency of short packets, no need for sensing in IoT devices, and no need for initial connection setup. The present invention relates to multiple access control (MAC) based on framed slotted ALOHA (framed slotted ALOHA, FSA) protocol in a centralized wireless charging communication network. In other words, the centralized wireless charging communication network of the embodiment of the present invention is a communication network based on the FSA protocol.

FIG. 2 is a schematic diagram of time allocation of a centralized wireless charging communication network according to an embodiment of the present invention. In the FSA protocol, time is divided into multiple frames (FR), and each frame FR is further divided into multiple time slots (time slots). There are two types of time slots: uplink time slots and downlink time slots. In the uplink time slot, the IoT device sends data packets to the base station 140 . Each frame FR contains only one downlink time slot, and the downlink time slot is a broadcast time slot, and the base station 140 omnidirectionally (omnidirectionally) broadcasts/sends a carrying broadcast packet to multiple IoT devices in the broadcast time slot B Every IoT device that is not fully charged can use SWIPT technology in broadcast slot B to harvest energy in broadcast slot B. In an embodiment of the present invention, the information included in the broadcast packet includes, for example, frame synchronization, the number of time slots in a frame, the acknowledgment in a previous frame, and the like. The IoT devices 120 ₁ -120 ₆ will use the synchronization information of the broadcast packet to synchronize with the base station 140 .

As shown in Figure 2, the broadcast time slot B is located at the beginning of each frame, and immediately after the broadcast time slot B are multiple mini-slots (mini-slots) MS, and each mini-slot is pre-allocated to an IoT device . Multiple IoT devices send their energy information (residual power) to the base station 140 in multiple mini-slots MS.

The mini time slot is only used to allow the IoT device to send necessary device information to the base station 140 , so the length of the mini time slot is relatively short. As shown in Figure 2, there are m consecutive time slots TS ₁ ~TS _m after the mini time slot, and the IoT device can try to transmit packets (data packets) in m consecutive time slots TS ₁ ~TS _m to base station 140 . In addition, in the time slots TS ₁ -TS _m , the base station 140 can select an IoT device in a remaining time slot and send an RF charging signal to it to collect energy. Specifically, with the help of the radio frequency positioning of the IoT device, the base station can obtain the precise location of the IoT device, so in each time slot TS ₁ ~TS _m , the base station 140 uses directional (directional) wireless power transmission to one of the IoT devices send radio frequency charging signals. In addition to reducing energy consumption and interference during transmission and prolonging operating time, the base station can also have a longer energy transmission distance.

FIG. 2 shows several examples of energy transmission (indicated by the solid arrow from the base station 140 towards the IoT device) and/or packet transmission (indicated by the dotted arrow from the IoT device towards the base station 140). For example, in time slot TS ₁ , the IoT device ₁₂₀₂ and the IoT device 120 _i send data packets to the base station 140 at the same time, causing packet collision (packet collision), and the base station 140 cannot successfully receive from the IoT device. data packets. For example, in the time slot TS _m−1 , the IoT device 120 ₁ sends a data packet to the base station 140, and the base station 140 successfully receives the data packet from the IoT device 120 ₁ successfully.

In each time slot TS ₁ ~TS _m , the base station 140 selects an IoT device and sends a radio frequency charging signal to it, for example, in the time slot TS ₁ , the base station 140 sends a radio frequency to the IoT device 120 ₁ Charging signal; in time slot TS ₂ , the base station 140 sends a radio frequency charging signal to the IoT device 120 _n ; in time slot TS _m−1 , the base station 140 sends a radio frequency charging signal to the IoT device 120 _i . It is worth noting that in the time slot TS _m , the IoT device ₁₂₀₂ sends a data packet to the base station 140, and at the same time the base station 140 sends a radio frequency charging signal to the IoT device ₁₂₀₂ , however, because the IoT device works on Due to the half-duplex transmission mode, the IoT device 120 ₂ cannot receive the RF charging signal from the base station 140 to collect energy. This phenomenon is called vain charging. The purpose of the present invention is to eliminate useless charging.

FIG. 3 is a flowchart of a communication transmission method of a centralized wireless charging communication network according to an embodiment of the present invention. In step S1, the base station 140 sends a broadcast packet to a plurality of IoT devices 120 ₁ ~ 120 ₆ in the broadcast time slot B, and then, the plurality of IoT devices 120 ₁ ~ 120 ₆ use SWIPT technology to broadcast from the base station in the broadcast time slot B Station 140 receives broadcast packets to harvest RF energy.

In step S2, multiple IoT devices send data including residual power and randomly selected time slots to the base station 140 in multiple mini time slots MS. Specifically, since the residual power stored in the battery of each IoT device is different, in subsequent time slots, the base station 140 will give priority to sending radio frequency charging to the IoT device with lower residual power. signal to allow it to collect energy. Specifically, the randomly selected time slot of the IoT device is the time slot in which the IoT device sends a packet to the base station 140. For example, if the randomly selected time slot TS _m-1 of the IoT device ₁₂₀₁ is, then the IoT device The device 120 ₁ sends the packet to the base station 140 in time slot TS _m-1 .

In step S3, the base station 140 selects a selected device from the plurality of IoT devices according to the residual power of the plurality of IoT devices. Specifically, the base station 140 selects the device with the smallest residual power from the plurality of IoT devices as the first selected device. In addition, if there are more than two IoT devices with the smallest residual power, the base station 140 randomly selects one as the first selected device.

In step S4, the base station 140 determines whether the randomly selected time slot of the selected device is the current time slot, if not, proceeds to step S5, and if yes, returns to step S3. Specifically, the base station 140 determines whether the randomly selected time slot of the first selected device is the current time slot.

In step S5, when the base station 140 determines that the randomly selected time slot of the selected device is not the current time slot, the base station 140 transmits the RF charging signal to the selected device in the current time slot. Specifically, when the base station 140 judges that the randomly selected time slot of the first selected device is not the current time slot, the base station 140 transmits a radio frequency charging signal to the first selected device in the current time slot, so that the first selected device can be transferred from the base station. Station 140 harvests radio frequency energy. In this way, since only the first selected device receives the radio frequency charging signal, useless charging will not occur.

Relatively speaking, when the base station 140 determines that the randomly selected time slot of the selected device is the current time slot, the base station 140 again selects the selected device from the plurality of Internet of Things devices according to the residual power of the plurality of Internet of Things devices. Specifically, when the base station 140 determines that the randomly selected time slot of the first selected device is the current time slot, the base station 140 selects the second selected device with the second smallest residual power among the plurality of IoT devices. And so on (that is, when the base station 140 judges that the randomly selected time slot of the second selected device is not the current time slot, the base station 140 transmits a radio frequency charging signal to the second selected device in the current time slot, so that the second selected device Collect radio frequency energy from the base station; when the base station 140 judges that the randomly selected time slot of the second selected device is the current time slot, the base station 140 selects the one with the smaller residual power from a plurality of IoT devices as the third selected device).

In addition, in the embodiment of the present invention, if the judgment result in step S4 is negative, that is, when the base station 140 judges that the randomly selected time slot of the first selected device is the current time slot, except that the base station 140 is in the current time slot In addition to selecting the second selected device to transmit the RF charging signal, the first selected device (or any IoT device other than the second selected device) can transmit packets to the base station in the current time slot. In this way, since there is only the second selected device to receive the RF charging signal, useless charging will not occur, and since the sender of the data packet only has the first selected device (or any IoT device other than the second selected device) ), no packet collision will occur.

In other words, when the randomly selected time slot of the IoT device is the current time slot, the IoT device transmits packets to the base station at the current time slot; relatively speaking, when the randomly selected time slot of the IoT device is not the current time slot And when the base station transmits the radio frequency charging signal to the Internet of Things device in the current time slot, the Internet of Things device receives the radio frequency charging signal from the base station to collect radio frequency energy.

Specifically, the base station 140 collects the residual power of multiple IoT devices and the information of the randomly selected time slots in the mini time slot MS, and creates a table for recording the information. Then, in the time slots TS ₁ ~ TS _m after the mini time slot MS, the base station 140 will use the information of the residual power in the table to select the IoT device with the smallest residual power in the table as the selected device, and then the base station 140 Judging whether the randomly selected time slot of the selected device is the current time slot, if so, the base station 140 abandons the selected device, and tries to select the one with the second smallest residual power from the remaining IoT devices as the selected device, so as to avoid useless charging (vain charging) ). The base station 140 will repeat the above process until (i) the random selection time slot of the selected device is not the current time slot (ii) there are no remaining IoT devices to be selected.

Specifically, when the IoT device does not send a packet in a certain time slot, if (i) the base station sends a radio frequency charging signal to the IoT device in that time slot, and (ii) the battery of the IoT device If it is not yet fully charged, the IoT device receives a radio frequency charging signal from the base station to collect radio frequency energy.

Table 1 is an exemplary table used to illustrate the communication transmission method of the centralized wireless charging communication network according to an embodiment of the present invention. Table I IoT device residual energy random time slot 120 ₁ 3 TS ₂ 120 ₂ 1 TS ₁ 120 ₃ 4 TS ₃ 120 ₄ 2 TS ₄

As shown in Table 1, firstly, in the time slot TS ₁ , the base station 140 selects the device with the smallest residual power from the plurality of IoT devices 120 ₁ -120 ₄ as the first selected device (ie, the IoT device 120 ₂ ). At this time, since the randomly selected time slot TS ₁ of the Internet of Things device ₁₂₀₂ is the current time slot TS ₁ , if the Internet of Things device 120 ₂ sends a data packet to the base station 140 and at the same time the base station 140 sends a radio frequency charge to the Internet of Things device 120 ₂ signal, will cause useless charging (vain charging). Therefore, for the present invention, the base station 140 will determine in step S4 that the randomly selected time slot (time slot TS ₁ ) of the first selected device (i.e. the IoT device 120 ₂ ) is the current time slot, and the base station 140 will automatically Among the plurality of IoT devices 120 ₁ -120 ₄ , the one with the second smallest residual power is selected as the second selected device (ie, the IoT device 120 ₄ ). At this time, since the randomly selected time slot TS ₄ of the IoT device 1204 is not the current time slot TS ₁ , the IoT device 120 _{2 whose} randomly selected time slot is the current time slot TS ₁ sends a data packet to the base station 140 and at the same time The base station 140 sends a radio frequency charging signal to the second selected device (ie, the IoT device 120 ₄ ), thereby avoiding vain charging.

In the embodiment of the present invention, the decision logic of the random selection time slot of the IoT device is as follows. When the IoT device judges that its residual power is greater than the power threshold and there is at least one packet in the queue of the IoT device, the IoT device randomly selects from multiple time slots (such as TS ₁ ~TS _m ) One is used as a random selection time slot for the IoT device. Relatively speaking, when the IoT device determines that its residual power is not greater than the power threshold or when there is not at least one packet in the queue of the IoT device, the IoT device designates the randomly selected time slot of the IoT device as There is no designated time slot (eg TS ₀ , not shown) to send packets.

Specifically, an IoT device first checks the residual power stored in its battery. If its residual power is greater than the power threshold (for example, a specific value set by the user) and when there is a packet in its queue, the IoT device randomly selects one of the m time slots as the IoT device's Randomly select a time slot as the time slot for subsequent packets to be sent. Relatively speaking, if the remaining power is less than or equal to the power threshold or there is no packet in its queue, the IoT device will not send packets from the m time slots. In the embodiment of the present invention, in order to avoid vain charging, the IoT device will send its randomly selected time slot to the base station 140 in advance of the mini time slot MS.

Specifically, if only one IoT device sends a packet to the base station in one of the m time slots, the base station receives a packet from the IoT device and the base station sends a packet to the IoT device in broadcast time slot B of the next frame. The networked device replies with an acknowledgment (ie, the acknowledgment from the previous frame). In addition, if two or more IoT devices send packets to the base station in one of the m time slots, a packet collision will occur, and the base station will receive a damaged packet, and the base station will not send packets to the base station in the next frame. The acknowledgment message is sent in the broadcast slot B, and those IoT devices that sent the corrupted packet will try to resend the same packet in the next frame with permission probability p, where 0≦p≦1. The above retransmission attempts will be repeated until the delay of the packet exceeds the predetermined delay period. When the delay of the packet exceeds the predetermined delay period, the packet is discarded.

In general, the present invention proposes a multiple access control (Multiple access control, MAC) based on the framed slotted ALOHA (framed slotted ALOHA, FSA) protocol. The residual power of the connected devices and the information of the randomly selected time slots are used to arrange the charging sequence of the connected devices. For the present invention, since time slots are shareable between IoT devices based on the FSA protocol, IoT devices can harvest energy in time slots in which they are not sending packets. Simulation results show that the MAC based on the FSA protocol of the present invention produces better system performance, higher throughput, and lower packet loss.

The features of several embodiments are outlined above, so those skilled in the art can better understand aspects of the present invention. Those skilled in the art should appreciate that they can easily use the present invention as a basis to design or modify other processes and structures, thereby achieving the same goals and/or achieving the same advantages as the embodiments described herein . Those skilled in the art should also understand that these equivalent constructions do not depart from the spirit and scope of the present invention, and that they can make various changes, substitutions and alterations without departing from the spirit and scope of the present invention.

120 ₁ ~120 ₆ , 120 _i , 120 _n : IoT device 140: base station 160: network B: broadcast time slot FR: frame MS: mini time slot S1~S5: step TS ₁ ~TS ₄ , TS _{m- 1} ,TS _m : time slot

A better understanding of aspects of the present invention can be obtained from the following detailed description in conjunction with the accompanying drawings. It is to be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of discussion. [ FIG. 1 ] is a schematic diagram of a communication system of a centralized wireless charging communication network according to an embodiment of the present invention. [ FIG. 2 ] is a schematic diagram of time allocation of a centralized wireless charging communication network according to an embodiment of the present invention. [ FIG. 3 ] is a flowchart of a communication transmission method of a centralized wireless charging communication network according to an embodiment of the present invention.

S1~S5: steps

Claims (9)

A communication transmission method for a centralized wireless charging communication network, comprising: a base station sends a broadcast packet to a plurality of Internet of Things devices in a broadcast time slot; Power and data of a randomly selected time slot are sent to the base station, wherein the mini-slots are followed by the broadcast time slot; the base station selects the device with the smallest remaining power from among the IoT devices as a first selected device ; and when the base station determines that the randomly selected time slot of the first selected device is not a current time slot, the base station transmits a radio frequency charging signal to the first selected device at the current time slot, so that the second selected device A selected device collects radio frequency energy from the base station, wherein the current time slot is after the mini time slots; wherein the base station operates in a full-duplex transmission mode, wherein each of the IoT devices operates in half Duplex transmission mode. The communication transmission method as described in claim 1, further comprising: when the base station judges that the randomly selected time slot of the first selected device is the current time slot, the base station selects the remaining time slot from the IoT devices The one with the second smallest power is used as a second selected device; and when the base station judges that the randomly selected time slot of the second selected device is not the current time slot, the base station transmits the radio frequency charging signal to the current time slot at the current time slot the second selected device, so that the second selected device transmits from the base station Harvesting RF energy. The communication transmission method as described in claim 1, further comprising: when the first selected device determines that the randomly selected time slot of the first selected device is the current time slot, the first selected device transmits in the current time slot packet to the base station. The communication transmission method as described in claim 1, further comprising: when one of the IoT devices determines that the residual power of the IoT device is greater than a power threshold and when the IoT devices one of the IoT devices randomly selects one of the plurality of time slots as the randomly selected time slot of the one of the IoT devices when there is at least one packet in one of the queues of the IoT devices, Wherein these time slots are followed by these mini time slots. The communication transmission method as described in claim 4, further comprising: when one of the IoT devices judges that the residual power of the one of the IoT devices is not greater than the power threshold or when the IoT When the one of the devices does not have at least one packet in the queue, the one of the IoT devices designates the randomly selected time slot of the one of the IoT devices as a designation that there are no packets to send time slot. The communication transmission method as described in claim 1, further comprising: when the random selection slot of one of the IoT devices is the corresponding When the previous time slot, the one of the IoT devices transmits packets to the base station in the current time slot; and when the randomly selected time slot of the one of the IoT devices is not the current time slot and When the base station transmits the radio frequency charging signal to the one of the IoT devices in the current time slot, the one of the IoT devices receives the radio frequency charging signal from the base station to collect radio frequency energy. The communication transmission method as described in Claim 1, further comprising: the IoT devices receive the broadcast packet from the base station in the broadcast time slot to collect radio frequency energy. The communication transmission method as described in claim 7, wherein each of the IoT devices uses a simultaneous wireless information and power transfer (SWIPT) technology to receive the broadcast packet to collect radio frequency energy. The communication transmission method as described in Claim 1, wherein the centralized wireless charging communication network is a communication network based on framed slotted ALOHA (framed slotted ALOHA, FSA) protocol.

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