KR101971392B1 - Ambient backscatter communication system in energy harvesting cognitive radio network and ambient backscatter communication method using the same - Google Patents

Abstract

The present invention relates to an ambient backscattering communication system in an energy harvesting cognitive radio network, and a method thereof. According to the present invention, the backscattering communication method using a communication system including an access point, a primary user terminal, N secondary transmission terminals, and a secondary reception terminal comprises: a step in which the access point broadcasts a primary signal to be transmitted to the primary user terminal by using a cellular band during a first one of the first and second sections set on an occupation section where a primary user occupies the cellular band in a frame; a step in which each of the N secondary transmission terminals puts its signal to the primary signal received from the access point and sequentially backscatters the signal to the secondary reception terminal during a corresponding one of the subsections in the first section; a step in which each of the N secondary transmission terminals harvests energy from the primary signal that is beamformed and received from the access point during the second section; and a step in which each of the N secondary transmission terminals sequentially transmits its signal to the secondary reception terminal by using the cellular band during a corresponding one of the subsections in a waiting section where the primary user is not occupied in the frame. The present invention can simultaneously increase the energy collection efficiency and data transmission efficiency of a secondary user in the energy harvesting cognitive radio network.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy harvesting communication system and a backward scattering communication method using the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peripheral backscattering communication system in an energy harvesting or radio network and a peripheral backscattering communication method using the same. More particularly, the present invention relates to an energy harvesting- To a peripheral backscattering communication system and a method thereof.

1 is a diagram illustrating a conventional Cognitive Radio Network (CRN) communication system. The H-AP shown in FIG. 1 represents an access point (base station), PR represents a primary user terminal, and ST and SR represent a transmitting terminal and a receiving terminal on the secondary user side, respectively.

Referring to the time frame structure shown in the upper part of FIG. 1, the frame is divided into an occupancy period (Busy) and a waiting period (Idle). In FIG. 1, it is illustrated that the occupation interval is allocated for a longer time than the waiting interval.

First, the left side of FIG. 1 shows the operation of the Busy section. The Busy interval is a period in which the cellular band (license band) is already occupied by the primary user (PU). Thus, during the Busy interval, the primary user terminal (PR) receives data from the access point (H-AP) over the cellular band. At this time, data transmission is limited for a secondary user (SU).

The right figure shows the operation of the Idle section. In the idle period when the primary user (PU) does not use the cellular band, data transmission of the secondary user (SU) becomes possible. That is, the secondary transmitting terminal ST transmits data to the secondary receiving terminal SR using the cellular band.

Thus, if the channel is being used by the primary user (PU), data transfer of the secondary user (SU) is restricted, and if the channel is empty, data transfer of the secondary user (SU) becomes possible.

2 is a diagram illustrating a conventional wireless energy harvesting CRN (EH CRN) communication system.

In the case of FIG. 2, the operation of the Idle section is the same as that of FIG. 1, but the operation of the Busy section is different from that of FIG. In the Busy interval, a secondary user (SU) can collect (harvest) wireless energy from a primary signal transmitted by an access point (H-AP). Of course, other channels may be selected to secure an empty channel for data transmission.

However, since the energy that can be collected by the secondary user (SU) is limited from the primary signal in the Busy interval and there is a limit in energy collection amount, it is difficult to demodulate and transmit the signal when the corresponding channel is empty in the future. Therefore, an application method of peripheral backscattering communication in which a signal is reflected by reflecting or non-reflecting signals existing in the surroundings has been proposed.

FIG. 3 is a diagram illustrating a conventional AMBC-assisted EH CRN (hereinafter, referred to as "AMBC-assisted energy harvesting CRN") communication system to which a peripheral backscattering technique is applied.

In the system of FIG. 3, Busy section is divided into first and second sections, unlike FIG. The first section is a period in which a secondary user (SU) backscatter data (see the left figure and the other one is a section in which a secondary user (SU) collects energy from the surrounding signal (see the middle figure).

In the first section (backscattering section), the secondary transmitting terminal EH ST transmits data to the secondary receiving terminal SR using backscattering (backscattering) . In the second interval (energy collection interval), the secondary transmission terminal EH ST wirelessly collects energy from the surrounding primary signal. The collected energy is used by the secondary user to transmit data over the cellular channel when the channel is empty, that is, during the Idle section.

However, if the backscattering period is long, the time for the secondary user (SU) to transmit data becomes long, and the transmission efficiency increases. However, since the time for collecting the energy is relatively shortened and the energy collection interval is relatively short, the trade-off in which the secondary user (SU) influences the transmission efficiency when data is transmitted through the cellular band in the idle section A trade-off problem occurs. Accordingly, there is a need for a technique for simultaneously improving energy collection efficiency and data transmission efficiency in the AmBC-assisted EH CRN communication system.

The technology of the background of the present invention is disclosed in Korean Patent Publication No. 2017-0071386 (published on June 23, 2017).

It is an object of the present invention to provide a peripheral backscattering communication system and method in an energy harvesting or radio network capable of improving the energy collection rate of a secondary user and ultimately increasing a data transmission rate.

The present invention provides a backscattering communication method using a communication system including an access point, a primary user terminal, N secondary transmission terminals, and a secondary reception terminal, Broadcasting a primary signal to be sent to the primary user terminal using the cellular band during the first one of the first and second intervals set on an occupied interval occupying the bandwidth, Wherein each of the transmitting terminals performs a backscattering on the primary signal received from the access point and sequentially backsamples the signal to the secondary receiving terminal during a corresponding one of the subintervals in the first period, Wherein each of the N secondary transmission terminals transmits a primary signal that is beamformed received from the access point during the second interval, And wherein each of the N secondary transmission terminals uses the cellular band during one corresponding sub-interval of the sub-periods in the idle waiting interval of the primary user in the frame And sequentially transmitting its own signal to the secondary receiving terminal.

In addition, each of the first and second sections may have N sub-sections.

The backscattering may be performed such that during an n-th sub-interval in which the n-th secondary transmitting terminal performs the backscattering, each of the remaining N-1 secondary transmitting terminals, except for the n-th secondary transmitting terminal, You can harvest energy from the primary signal received from the point.

Also, in the backscattering step, the secondary transmitting terminal may perform backscattering in such a manner as to reflect the primary signal when the signal of its own is one bit and not to reflect the primary signal when it is a bit of 0 .

Also, the secondary terminal may be configured to transmit, during the first interval, the access point and the N secondary transmission terminals, using the backscattering channel information estimated through the backscattered signal from each of the N secondary terminals, Estimates a plurality of first channel information as channel information between each of the first channel information and the second channel information, and feeds back the first channel information to the access point, It is possible to design the condition of the beam forming corresponding to each of the N secondary transmission terminals.

In addition, the secondary receiving terminal estimates a plurality of second channel information between the secondary receiving terminal and the secondary transmitting terminal from the signal received from each of the N secondary transmitting terminals during the waiting period in the current frame And acquires the backscattering channel information in a next frame, the first channel information may be estimated using the backscattering channel information and the plurality of second channel information.

The access point adaptively adjusts the lengths of the first section and the second section in the occupancy interval according to the energy collection efficiency of the secondary transmission terminal. The higher the energy collection efficiency, The length of the first section can be increased by decreasing the length of the first section.

In addition, the present invention provides a method for transmitting a primary band to a primary user terminal using a cellular band during a first period of a first period and a second period on a occupied period occupied by a primary user in a frame, A primary user terminal for receiving the primary signal through the cellular band during the occupancy period in the frame; and a second user terminal for receiving the primary signal during a corresponding one of the sub- , Sequentially backscattering the primary signal received from the access point to the secondary receiving terminal and hunting energy from the primary signal beamformed received from the access point during the second period N secondary transmitting terminals, and the primary user in the frame is unoccupied And a secondary receiving terminal for receiving a signal from the N secondary transmitting terminals during a sub-interval in a waiting section, wherein each of the N secondary transmitting terminals includes a corresponding one of the sub- And transmits its signal to the secondary receiving terminal in succession using the cellular band.

According to the present invention, an energy harvesting or energy-saving efficiency and a data transmission efficiency of a secondary user can be simultaneously increased in a radio network.

1 is a diagram illustrating a conventional cognitive radio network communication system.
2 is a diagram illustrating a conventional wireless energy harvesting radio network communication system.
3 is a diagram illustrating a wireless energy harvesting radio network communication system to which a conventional peripheral backscattering technique is applied.
4 is a diagram illustrating a peripheral backscattering communication system in an energy harvesting or radio network according to an embodiment of the present invention.
5 is a diagram for explaining operations of each secondary phase of a secondary transmitting terminal in each system in the system of FIG.
FIGS. 6 to 8 are views for explaining the system operation of each phase of FIG. 4. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

4 is a diagram illustrating a peripheral backscattering communication system in an energy harvesting cognitive radio network (EH CRN) according to an embodiment of the present invention.

A peripheral backscattering communication system in an EH CRN according to an embodiment of the present invention includes an access point (H-AP), a primary user equipment (PR), N secondary transmission terminals (EH ST; Energy Harvesting Secondary Transient), and a Secondary Receiver (SR).

The embodiment of the present invention considers a model in which there is one primary network and one secondary network. An access point (H-AP) is assumed to be a hybrid base station capable of transmitting both data and power.

In the system, a primary user terminal (PR) means a primary user (PU), a secondary transmission terminal (EN) (ST) and a secondary reception terminal (SR) ; Secondary User). In this embodiment, the secondary receiving terminal SR may be a gateway device

A frame structure is shown at the top of Fig. The length direction of the frame corresponds to time. In the present embodiment, a frame structure composed of an occupied section Busy and a waiting section Idle is considered. Here, an access point (H-AP) first transmits a signal to a primary user through a cellular downlink channel, and then an access point (H-AP) transmits a signal through which a primary user transmits a signal through the uplink channel (H-AP), the frame structure is configured as Busy and Idle in terms of operation of the access point (H-AP).

In the frame structure, the occupation interval Busy is a period during which the primary user occupies the cellular band (channel), and the waiting period Idle represents a period of the idle state in which the channel is idle. Here, the cellular band may mean the license band allowed in the cellular network.

During the occupancy period (Busy), the primary user receives data from the access point (H-AP) using the cellular band. At this time, the use of the corresponding band is restricted to the secondary user.

Thereafter, when the waiting period Idle comes, the secondary user can transmit data using the empty cellular band. That is, the secondary transmitting terminal ST can transmit data to the secondary receiving terminal SR using the corresponding cellular band.

As described above, when the channel is being used by the primary user, the secondary user can not use the corresponding channel, but the secondary user can transmit data using the channel during the time when the channel is empty.

In the embodiment of the present invention, the occupancy period (Busy) is again divided into two sections: a first section (Phase I) and a second section (Phase II). The first interval is a backscattering period in which a secondary user sends its signal to a primary signal (primary signal), and the second interval is an energy collection interval in which a secondary user hunts the energy sensed in the surroundings.

In this embodiment, the primary signal can be defined as data to be sent to the primary user terminal (PR) by the access point (H-AP) during the busy period (Busy). Of course, the primary signal is not transmitted in the idle phase (Phase III).

During the first period (Phase I), the secondary transmitting terminal ST can transmit its signal to the primary signal and backscatter it to the secondary receiving terminal SR, and during the second period (Phase II) The secondary transmission terminal ST can collect the energy of the primary signal. The collected energy may be used when the secondary transmitting terminal ST sends a signal to the secondary receiving terminal SR using the corresponding cellular band in a waiting period Idle.

As above. In Phase I, the secondary user backs-cats its signal to the primary signal, and in Phase Ⅱ, the secondary user collects energy from the primary signal. Phase III is a period in which the primary user is unoccupied, and the secondary user communicates over the empty cellular band.

5 is a diagram for explaining operations of each secondary phase of a secondary transmitting terminal in each system in the system of FIG.

First, in Phase I, N secondary transmitting terminals ST carry their signals to primary signals and backscatter them to secondary receiving terminals SR (S510). At this time, the secondary transmitting terminal ST performs backscattering in one sub-section assigned to itself among N sub-sections in which Phase 1 is N-divided. Therefore, backscattering is performed sequentially one by one of the respective secondary transmission terminals ST. However, the energy is collected around the non-backscattering section.

Next, in Phase II, each of the secondary transmission terminals ST collects energy from a primary signal received by beamforming from an access point (H-AP) (S520).

The length of Phase II can be gradually reduced through optimization in the communication process. The process for optimization will be described in detail later. As phase Ⅱ decreases, Phase Ⅰ increases, so it is possible to increase the transmission capacity of backscatter data and increase transmission efficiency of secondary users.

Further, in Phase II, the access point (H-AP) can send a primary signal to each secondary transmission terminal ST in a beam-fusing manner based on the channel information previously fed back from the secondary reception terminal SR Which can increase energy collection efficiency. The principle will be described in detail later.

Next, in Phase III, the N secondary transmitting terminals ST transmit their signals to the secondary receiving terminals SR using the cellular band (S530). At this time, the secondary transmitting terminal ST transmits data in one sub-section assigned to itself among N sub-sections in which Phase III is divided into N parts. Therefore, data is sequentially transmitted one by one from each of the secondary transmission terminals ST.

Based on the above description, the operation of the system in each phase will be described in more detail below.

6 is a diagram for explaining the system operation in Phase I of FIG.

As shown in FIG. 6, during the first period (Phase I) of the first and second intervals Phase I and II set on the occupation interval Busy, the access point H-AP uses the cellular band And broadcasts a primary signal to be sent to the primary user terminal (PR). The primary user terminal (PR) can receive and demodulate the primary signal via the cellular download link.

In addition, since the access point (H-AP) can transmit the primary signal in a broadcast manner, the primary signal is also transmitted to the secondary transmitting terminal (ST).

In this first phase (Phase I), each of the N secondary transmitting terminals ST1 to STN operates in a backscatter mode and transmits data to the secondary receiving terminal SR in a backscattering manner. At this time, each of the secondary transmission terminals ST1 to STN performs backscattering in different time intervals.

In other words, each of the N secondary transmitting terminals ST1 to STN receives, from one access point (H-AP), one of the N sub-sections divided in the first section (Phase I) And sends back its signal to the primary signal to be backscattered to the secondary receiving terminal SR sequentially.

As described above, each of the secondary transmitting terminals ST performs backscattering of its own signal in the primary signal only during one sub-interval corresponding to itself in the N sub-sections in the first period (Phase I) The secondary transmitting terminals ST1 to STN sequentially perform backscattering.

For example, ST1 backscatter data only in subinterval # 1 of N subintervals and ST2 backscatter data only in subinterval # 2. At this time, the remaining N-1 secondary transmission terminals that are not backscattered perform an operation of collecting energy from the surrounding primary signals.

That is, during the n-th sub-interval in which the n-th secondary transmitting terminal STn performs backscattering, the remaining N-1 secondary transmitting terminals except for the n-th secondary transmitting terminal STn are received from the access point You can harvest energy from the primary signal. Here, n = {1,2, ... , N}.

Through such an energy collection operation, the N secondary transmission terminals ST1 to STN can sufficiently maintain the energy consumed in the circuit when operating in the backscatter mode.

The backscattering method is as follows. The secondary transmitting terminal ST performs backscanning in such a manner that it reflects the primary signal when its signal is '1' and does not reflect the primary signal when it is '0'. Thereafter, the secondary receiving terminal SR can demodulate to '1' if the level of the received signal is higher than the threshold, and to '0' if it is lower than the threshold. The backscatter (ex, Wi-Fi backscatter) technique is well known and thus its detailed description is omitted.

Also, during this first period (Phase I), the secondary reception terminal SR estimates the backscattering channel information through the backscattered signals from each of the N secondary transmission terminals ST1 to STN. Here, the backscattering channel information means a channel between an access point (H-AT), a secondary transmitting terminal (ST), and a secondary receiving terminal (SR). This is because the backscattering signal itself is a signal sent to the secondary receiving terminal SR by receiving the secondary transmitting terminal ST signal on the primary signal received from the access point H-AP.

Also, the secondary receiving terminal SR uses the estimated back scattering channel information to transmit a plurality of first channel information, which is a channel between the access point (H-AP) and the N secondary transmitting terminals ST1 to STN, respectively And feedbacks back to the access point (H-AP). The first channel information means a channel between an access point (H-AP) and a secondary transmission terminal (ST).

The access point H-AP transmits the first channel information received from the secondary receiving terminal SR to the N secondary transmitting terminals ST1 to STN (Number of energy beamforming, angle, signal intensity, etc.) corresponding to each of the energy beamforming parameters.

That is, the access point (H-AP) can transmit a primary signal to each of the secondary transmission terminals ST1 to STN through the energy beamforming method in a second period (Phase II). This maximizes the energy collection efficiency of the secondary transmitting terminals ST1 to STN in the second period (Phase II).

Of course, in the first period (Phase I), the access point (H-AP) must temporarily receive the feedback transmitted from the secondary reception terminal SR while transmitting the primary signal. Therefore, As shown in Fig.

For reference, information necessary for beamforming is forward channel estimation information (first channel information) between a base station and a secondary transmission terminal, not backscattering channel estimation information. If channel estimation information (second channel information) between the secondary transmitting terminal ST and the secondary receiving terminal SR obtained in the waiting period (Phase III) is used in the future, the forward channel estimation information First channel information) can be obtained. This will be described in more detail in the description of the waiting period (Phase III).

Next, referring to FIG. 7, the operation in the second section (Phase II) in the Busy section in which the primary user occupies the cellular band is described.

Fig. 7 is a diagram for explaining the system operation in Phase II of Fig. 4. Fig.

As shown in FIG. 7, during the second period (Phase II), the access point (H-AP) transmits the primary signal to the primary user terminal (PR) via the cellular downlink, ST1 to STN) by a beam forming (Energy Beamforming) method.

The energy (beam) can be concentrated according to the position and angle of the secondary transmission terminals ST1 to STN according to the beam forming. Thus, each of the secondary transmitting terminals ST1 to STN can harvest energy from the beamforming primary signal.

Thus, in the second period (Phase II), all the secondary transmission terminals ST operate in the energy hubbing mode to collect energy. Due to the influence of the energy beam forming, the secondary transmission terminals ST can efficiently collect energy. Since the battery capacity of the secondary transmitting terminal ST is limited, the time required to collect the limited energy will decrease as the energy collection efficiency increases.

In the Busy period occupied by the main channel, if the energy collection interval (first interval) decreases, the backscatter interval (second interval) becomes longer, so that the secondary transmitting ST can transmit more data.

Next, referring to Fig. 8, the operation in the idle period Idle in which the primary user has not occupied the cellular band is described.

Fig. 8 is a diagram for explaining the system operation in Phase III of Fig. 4. Fig.

When the idle period (Phase III, Idle) occurs, the secondary transmitting terminal ST transmits its signal to the secondary receiving terminal SR through the cellular band. At this time, each of the secondary transmission terminals ST1 to STN transmits signals in different time intervals.

That is, each of the N secondary transmitting terminals ST1 to STN transmits its signal to 2 (n + 1) using the cellular band during one sub-interval corresponding to itself among the N sub- To the difference receiving terminal (SR).

Since each of the secondary transmitting terminals ST1 to STN transmits signals only during one sub-period corresponding to the N sub-sections in the first period (Phase III), the N secondary transmitting terminals ST1 to STN, STN) in turn transmit the signal using the cellular band.

The secondary receiving terminal SR can recover the data using the signal received from the nth secondary transmitting terminal STn and can obtain channel information between the secondary receiving terminal SR and the nth secondary transmitting terminal STn , The second channel information can be estimated.

That is, the secondary receiving terminal SR receives the signals from each of the N secondary transmitting terminals ST during the waiting period (Phase III) in the current frame from the secondary receiving terminal SR and the secondary transmitting terminal ST A plurality of second channel information are estimated. Thereafter, when the backscattering channel information is obtained in the next frame, the first backscattering channel information and the plurality of second channel information are used to respectively estimate the first channel information

A plurality of first channel information (H-AT to ST channels) are estimated using backscattering channel information (H-AT? ST? SR channel) and a plurality of second channel information . That is, it is possible to estimate the forward channel information between the access point (H-AP) and the secondary transmission terminal ST from the backscattering channel information by utilizing the second channel information. The secondary receiving terminal SR feeds back the estimated first channel information to the access point (H-AP) so that it can be used for the beam-forming design.

The access point (H-AP) can design the energy beamforming using the improved channel estimation information, and as the operation is repeated every frame, the design accuracy of the beamforming gradually increases with time, and finally, Can improve the energy collection efficiency of each secondary transmission terminal ST through beamforming in the second section II.

In addition, the access point (H-AP) determines the length of the first section (Phase I) and the second section (Phase II) in the occupied section Busy, according to the energy collection efficiency of the secondary transmitting terminal ST And the length of the first section (Phase I) can be increased by decreasing the length of the second section (Phase II) as the energy collection efficiency is higher.

Accordingly, since the amount of data backscattered by each secondary transmission terminal ST in the first section can also be increased, it is possible to simultaneously increase the energy collection efficiency and the data transmission efficiency of the secondary transmission terminal ST .

According to the present invention, it is possible to simultaneously improve the data transmission efficiency and the energy collection efficiency of the secondary user. That is, the secondary transmitting terminal ST reflects (backscatter) the primary signal existing in the surroundings and sends its data to the secondary receiving terminal SR during the time the primary user occupies the channel, The data transmission efficiency of the secondary user can be improved.

In particular, the secondary reception terminal SR restores data from the back-scattered received signal, estimates the back-scattered channel, and transmits the back-scattered channel information to the access point (H-AP) ST) and feeds it back to the access point (H-AP) to be used for transmit beamforming design for energy delivery at the access point (H-AP). Thus, the energy collection efficiency of the secondary transmitting terminal ST can be improved.

If the energy collection efficiency of the secondary transmitting terminal ST is improved, the amount of energy that can be stored is limited, so that the energy harvesting period (the second period) can be reduced. Therefore, the backscattering interval (first interval) in the Busy state in which the primary channel is occupied by the primary user is increased, and the data transmission efficiency can be simultaneously improved.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

H-AP: access point PR: primary user terminal
EH ST: Secondary sending terminal SR: Secondary receiving terminal

Claims (14)

A backscattering communication method using a communication system including an access point, a primary user terminal, N secondary transmitting terminals, and a secondary receiving terminal,
Wherein the access point transmits a primary signal to be transmitted to the primary user terminal using the cellular band during a first one of a first period and a second period that is set on an occupancy period in which a primary user occupies a cellular band in a frame, Broadcasting;
Wherein each of the N secondary transmission terminals transmits its signal to a primary signal received from the access point during a corresponding one of the sub-intervals in the first period to sequentially transmit the signal to the secondary receiving terminal, Catering;
Each of the N secondary transmitting terminals harvesting energy from a primary signal beamformed received from the access point during the second period; And
Wherein each of the N secondary transmission terminals transmits its signal to the secondary reception unit using the cellular band during one sub-interval corresponding to one of the sub-periods in the idle waiting interval of the primary user in the frame And sequentially transmitting to the terminal,
In the backscattering step,
The secondary transmitting terminal backscattering the primary signal in a manner that it reflects the primary signal when its signal is a one bit and does not reflect the primary signal when it is a bit of zero. The method according to claim 1,
Wherein each of the first and second sections has N sub-sections. The method according to claim 1 or 2,
Wherein the backscattering comprises:
During the n-th sub-interval in which the n-th secondary transmitting terminal performs the backscattering, each of the remaining N-1 secondary transmitting terminals except for the n-th secondary transmitting terminal receives energy from the primary signal received from the access point, To the surrounding back scattering communication method. delete The method according to claim 1,
The secondary receiving terminal,
Wherein the first and second transmission terminals are respectively connected to the first and second secondary transmission terminals by using backscattering channel information estimated through a backscattered signal from each of the N secondary transmission terminals, Estimates channel information, feeds back the channel information to the access point,
The access point comprising:
And designing the condition of the beam forming corresponding to each of the N secondary transmission terminals in the second section based on the plurality of first channel information fed back from the secondary receiving terminal. The method of claim 5,
The secondary receiving terminal,
Estimating a plurality of second channel information between the secondary receiving terminal and the secondary transmitting terminal from signals received from the N secondary transmitting terminals during the waiting period in the current frame,
And estimating the plurality of first channel information using the backscattering channel information and the plurality of second channel information when the backscattering channel information is obtained in a next frame. The method according to claim 1,
The access point comprising:
Wherein the length of the first section and the length of the second section are adaptively adjusted according to the energy collection efficiency of the secondary transmission terminal and the length of the second section is decreased as the energy collection efficiency is higher, 1 < / RTI > An access for broadcasting a primary signal to be transmitted to the primary user terminal using the cellular band during the first period of the first period and the second period set on the occupation period in which the primary user occupies the cellular band within the frame point;
A primary user terminal for receiving the primary signal over the cellular band during the occupancy period within the frame;
During a corresponding one of the sub-periods of the sub-periods in the first period, back-cats the primary signal received from the access point to the secondary receiving terminal, and during the second period, N secondary transmitting terminals for harvesting energy from a primary signal received beamforming from a point; And
And a secondary receiving terminal for receiving signals from the N secondary transmitting terminals during a sub-period in a waiting section in which the primary user is not occupied in the frame,
Wherein each of the N secondary transmission terminals comprises:
And sequentially transmits its signal to the secondary receiving terminal using the cellular band during a corresponding one of the sub-periods in the waiting interval,
The secondary transmitting terminal,
And backscattering the primary signal in a manner that reflects the primary signal when the signal is one bit and does not reflect the primary signal when the bit is a zero. The method of claim 8,
Wherein each of the first and second sections has N sub-sections. The method according to claim 8 or 9,
During the n-th sub-interval in which the n-th secondary transmitting terminal performs the backscattering, each of the remaining N-1 secondary transmitting terminals except for the n-th secondary transmitting terminal receives energy from the primary signal received from the access point, To the surrounding backscattering communication system. delete The method of claim 8,
The secondary receiving terminal,
A plurality of first channel information between the access point and the N secondary transmission terminals using the backscattering channel information estimated through a backscattered signal from each of the N secondary transmission terminals, Estimates and feeds back to the access point,
The access point comprising:
Wherein the condition of the beam forming corresponding to each of the N secondary transmission terminals in the second section is designed based on the plurality of first channel information fed back from the secondary receiving terminal. The method of claim 12,
The secondary receiving terminal,
Estimating a plurality of second channel information between the secondary receiving terminal and the secondary transmitting terminal from signals received from the N secondary transmitting terminals during the waiting period in the current frame,
And estimates the plurality of first channel information using the backscattering channel information and the plurality of second channel information when the backscattering channel information is acquired in a next frame. The method of claim 8,
The access point comprising:
Wherein the length of the first section and the length of the second section are adaptively adjusted according to the energy collection efficiency of the secondary transmission terminal and the length of the second section is decreased as the energy collection efficiency is higher, And a peripheral backscattering communication system that increases the length of one section.

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