KR101953607B1 - Backscatter system and uplink communication method using the same - Google Patents

Abstract

The present invention relates to a backscatter system and an uplink communication method using the same. An uplink communication method using a backscatter system comprises the steps of: broadcasting a wireless signal by an access point; transmitting information by reflecting the wireless signal through a plurality of antennas to which different sizes of power is allocated, by a powerless sensor node; detecting a first signal having a largest power among a plurality of signals received from the powerless sensor node and detecting a remaining signal using the detected first signal and estimated channel information, by a reader.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backscatter system and an uplink communication method using the same, and more particularly, to a backscatter system capable of improving a data rate in uplink communication using a tag having a plurality of antennas, ≪ / RTI >

Recently, the Internet of Things (IOT), which connects the Internet to all things, has attracted attention. The IOT provides intelligent interfaces and communication protocols to objects so that objects are integrated into the network, autonomously detects changes in objects or environments, and responds to user requests.

What is required to realize IOT technology is the implementation of intelligent interfaces and communication protocols, and the provision of intelligent interfaces to all objects. However, not all things can support LTE (Long Term Evolution), Wi-Fi protocol used in modern smart phones, etc., and the power required for wireless communication can not be periodically supplied through a battery.

In recent years, Wi-Fi backscatter technology has been attracting attention because it is connected with backscatter technology that collects Wi-Fi RF signals and acquires power. Wi-Fi backscatter technology is a promising technology for the IoT field where the Wi-Fi signal transmitted from the Wi-Fi AP (Access Point) is used for communication as an energy source so that the RFID tag can communicate without a separate power supply .

The Wi-Fi backscatter technology described above is largely composed of three devices. A Wi-Fi AP that generates a Wi-Fi signal, a Wi-Fi tag that reflects signals from the AP to transmit its signal, and a Wi-Fi reader that receives the tag information.

Wi-Fi APs and Wi-Fi readers are one of the existing Wi-Fi devices and therefore can send and receive Wi-Fi packets. The tag only reflects the signal generated from the Wi-Fi AP, and if it reflects the signal, it means '1'. The Wi-Fi reader determines what information has been transmitted from the tag through the power of the signal received from the tag.

However, in the conventional Wi-Fi backscatter system, since information of '1' and '0' is transmitted using a single antenna in a tag, there is a disadvantage that it has a low data rate in an uplink transmission.

A related prior art is Korean Patent No. 825,362 (published on April 28, 2008).

An object of the present invention is to provide a backscatter system capable of enhancing data transmission rate and signal detection performance in uplink communication and an uplink communication method using the same.

The problems to be solved by the present invention are not limited to the above-mentioned problem (s), and another problem (s) not mentioned can be clearly understood by those skilled in the art from the following description.

A method for uplink communication using a backscatter system according to an embodiment of the present invention includes the steps of broadcasting a radio signal by an access point and a powerless sensor node transmitting a radio signal through a plurality of antennas The reader detects a first signal having the largest power among a plurality of signals received from the powerless sensor node and transmits the first signal using the estimated first signal and the estimated channel information to the remaining And detecting a signal.

Advantageously, the access point is further configured to: after broadcasting the wireless signal, the powerless sensor node reflecting the wireless signal through the plurality of antennas and transmitting a preamble bit to the reader, And setting a threshold value for discrimination of the information bits using the bits.

Preferably, the step of setting the threshold value includes: when the preamble bits are '1' and '0', when the preamble bits are transmitted by one antenna at each antenna of the powerless sensor node, And a threshold value is set for each of them.

Preferably, the step of setting the threshold value comprises: when transmitting 2 bits at each antenna of the powerless sensor node, when the preamble bits are '11' and '00' And a threshold value when the preamble bit is '11' and a threshold value when the preamble bit is '00', respectively, for each of the preamble bits '01' and '10' And the threshold value is set by using the threshold value.

Advantageously, the step of detecting the residual signal comprises the steps of: detecting a first signal having the highest power among a plurality of signals received from the powerless sensor node; Estimating channel information from the signal, and calculating a difference signal between the estimated channel information and the signal based on the detected first signal to detect a remaining signal.

Advantageously, the first signal of the largest power can be detected by measuring the power magnitude of each of the plurality of signals and using the magnitude of the power of the preamble signal received from each antenna of the detected or null power sensor node.

Preferably, the estimated channel information and the signal based on the detected first signal are generated by a signal based on an estimated channel between an antenna and a reader of a power-free sensor node that transmits the first signal, Lt; RTI ID = 0.0 > channel. ≪ / RTI >

A backscatter system according to another embodiment of the present invention includes an access point for broadcasting a radio signal, a power-free sensor node for transmitting information by reflecting the radio signal through a plurality of antennas to which power of different sizes is allocated, And a reader for detecting a first signal having the largest power among a plurality of signals received from the powerless sensor node and detecting a remaining signal using the detected first signal and the estimated channel information.

Preferably, the power-free sensor node reflects the radio signal through the plurality of antennas and transmits a preamble bit to the reader, and the reader sets a threshold for discriminating information bits using the preamble bit .

Advantageously, the reader detects a first signal of the highest power among a plurality of signals received from the powerless sensor node, estimates channel information from the wireless signal received from the access point and the powerless sensor node And the remaining signal can be detected by subtracting the estimated channel information and the signal based on the detected first signal from the received signal.

An apparatus for detecting signals in a backscatter system according to another embodiment of the present invention includes a receiver for receiving a plurality of signals from a powerless sensor node having a plurality of antennas allocated with different powers, A channel estimator for estimating channel information from a signal received from a powerless sensor node, a channel estimation unit for detecting a first signal having the largest power among the plurality of signals, And a signal detector for calculating a difference between the received signal and a remaining signal.

The apparatus may further include a threshold value setting unit configured to set a threshold value for discrimination of information bits using the preamble signal received from the powerless sensor node.

Preferably, the threshold value setting unit averages all of the power magnitudes when the preamble bits are '1' and '0' when the antennas of the powerless sensor node transmit 1 bit at a time, The threshold value can be set individually.

Preferably, the threshold setting unit averages all of the power magnitudes when the preamble bits are '11' and '00' when transmitting 2 bits at each antenna of the powerless sensor node, And a threshold value when the preamble bit is '11' and a threshold value when the preamble bit is '00' for each of the preamble bits '01' and '10' Respectively.

Preferably, the signal detector measures a power level of each of the plurality of signals and detects a first signal having the largest power or a power level of a preamble signal received from each antenna of the powerless sensor node, It is possible to detect the first signal.

Preferably, the estimated channel information and the signal based on the detected first signal are transmitted between a signal by an estimated channel between an antenna of a tag that transmits the first signal and a reader, Lt; RTI ID = 0.0 > channel. ≪ / RTI >

According to the present invention, different power is allocated to each of the plurality of antennas of the powerless sensor node in the backscatter system, thereby improving the data transmission rate in the uplink communication.

Further, according to the present invention, the powerless sensor node transmits a signal with a power difference, thereby reducing power consumption as a whole.

According to the present invention, a reader first detects a signal of an antenna having the largest power among signals received from a powerless sensor node, and detects a remaining signal using the detected signal first, There is an effect of improving the transmission rate.

The effects of the present invention are not limited to the above-mentioned effects, and various effects can be included within the scope of what is well known to a person skilled in the art from the following description.

와

의 전력이 할당된 경우의 성능 그래프를 나타낸다.
도 8은 종래의 백스캐터 시스템과 본 발명의 실시예에 따른 백스캐터 시스템의 전송율을 보여주는 그래프이다. 1 is a diagram illustrating a backscatter system according to an embodiment of the present invention.
2 is a view for explaining a powerless sensor node according to an embodiment of the present invention.
3 is a block diagram for explaining a reader according to an embodiment of the present invention.
4 is a diagram for explaining the signal detecting unit shown in FIG.
5 is a diagram for explaining an uplink communication method in a backscatter system according to an embodiment of the present invention.
6 is a graph showing a comparison of error performance between a conventional backscatter system and a backscatter system according to an embodiment of the present invention.
FIG. 7 is a block diagram of a backscatter system according to an embodiment of the present invention.

Wow

Of power is allocated to each of the nodes.
8 is a graph showing a data rate of a conventional backscatter system and a backscatter system according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a backscatter system according to an embodiment of the present invention.

Referring to FIG. 1, a backscatter system includes a powerless sensor node 100, a reader 200, and an access point 300.

The access point 300 (Access Point) may correspond to a general wireless router, and transmits a wireless signal (Wi-Fi packet) to peripheral devices to provide a wireless Internet connection. The wireless Internet may be a conventional Wi-Fi, and the access point 300 may be a Wi-Fi wireless router used as a Wi-Fi helper. Of course, wireless Internet is not necessarily a Wi-Fi concept.

The access point 300 broadcasts a wireless signal (ex, Wi-Fi packet) to the surroundings. Accordingly, the wireless signal is transmitted to both the reader 200 and the powerless sensor node 100.

Since the powerless sensor node 100 operates with fine power and has no battery, it is difficult to wirelessly communicate with a large amount of power such as Wi-Fi. However, the wireless sensor node 100 can be connected to the Internet via the reader 200, Lt; / RTI >

The powerless sensor node 200 may be implemented in a tag form. In the embodiment of the present invention, the powerless sensor node 200 may refer to a battery-free passive tag in which a separate power supply (battery) such as an RFID tag is not present.

In a typical backscatter system, the reader 200 can transmit or request information to the powerless sensor node 100 through a downlink, and the powerless sensor node 100 transmits a response to the uplink (Up) Link to the reader 200 via the network.

In the embodiment of the present invention, to improve the data rate in the uplink, the power-free sensor node 100 includes a plurality of antennas to which power of different sizes is allocated. Since the powerless sensor node 100 has a plurality of antennas, there are multiple channel environments on the signal transmission / reception path.

The powerless sensor node 100 allocates power of different magnitudes to a plurality of antennas and reflects radio signals received from the access point 300 through a plurality of antennas to which power of different magnitudes is allocated, . That is, the powerless sensor node 100 transmits information to be transmitted to the reader 200 by transmitting the information to the wireless signal received from the access point 300. At this time, the powerless sensor node 100 can transmit the same signal to the reader 200 through a plurality of antennas.

The reader 200 can modulate the wireless signal received from the access point 300 into a signal readable by the powerless sensor node 100 and transmit the modulated signal to the powerless sensor node 100 via the Internet The Internet of things can be realized. The reader 200 may correspond to a user terminal having a built-in wireless Internet function (Wi-Fi function) such as a normal mobile phone, a smart phone, a smart pad, and a notebook computer.

The reader 200 may receive both a wireless signal transmitted by the access point 300 and a wireless signal reflected by the powerless sensor node 100. The reader 200 may receive the wireless signal transmitted from the access point 300 and the non- And estimates channel information from a radio signal received from the base station 100. That is, the reader 200 can estimate the channel information including the two paths using the radio signal received through the two paths (access point to reader, access point to powerless sensor node to reader).

The reader 200 detects a first signal having the largest power among a plurality of signals received from a plurality of antennas of the powerless sensor node 100 and detects a remaining signal using the estimated channel information and the first signal . That is, the reader 200 estimates the channel information from the radio signal received from the access point 300 and the power-free sensor node 100, and estimates channel information of the largest power among the plurality of signals received from the power- And detects the first signal. Since the powerless sensor node 100 transmits the same signal with a difference in power, the reader 200 can detect the first signal having the largest power among a plurality of identical signals having different power sizes. At this time, the reader 200 can measure the power magnitude of each of the plurality of signals received from the powerless sensor node 100, and select the first signal having the largest power magnitude. Also, the reader 200 may detect the first signal having the largest power size by using the power level of each preamble signal received from each antenna of the powerless sensor node 100 before the uplink communication. When the first signal having the largest power size is detected, the reader 200 can calculate the difference between the estimated channel information and the detected first signal using the received signal to detect the remaining signal.

As described above, the reader 200 detects the remaining signals using the signals transmitted from the antennas having the largest power, so that it is not necessary to detect all the signals transmitted from the plurality of antennas of the powerless sensor node 100, This has the effect of improving the signal detection performance.

2 is a view for explaining a powerless sensor node according to an embodiment of the present invention.

Referring to FIG. 2, the powerless sensor node 100 includes a power allocator 120 that allocates different powers to a plurality of antennas 110 according to an embodiment of the present invention.

Since the powerless sensor node 100 has a plurality of antennas 110, multiple channel environments exist on the signal transmission / reception path.

The power allocating unit 120 allocates powers of different sizes to a plurality of antennas so that each of the antennas transmits signals with different powers. In this case, it is desirable to preset the power allocated to each antenna in consideration of the power consumption of the power-free sensor node 100. Therefore, the power allocator 120 may preset the antennas to which power of different sizes is allocated have.

Powerless sensor node 100 uses power through backscatter technology, so there is power limitation. Therefore, it is necessary to allocate power suitable for a plurality of antennas of the powerless sensor node 100, and power of different sizes can be allocated to each antenna as needed.

, 제2 안테나에

의 전력을 할당할 수 있다. For example, when the first antenna and the second antenna are provided, the power allocation unit 120 allocates

, The second antenna

Quot; power "

As described above, the powerless sensor node 100 can reduce the power consumption as a whole by transmitting a signal with a power difference. At this time, backscattering is performed simultaneously through a plurality of antennas.

FIG. 3 is a diagram illustrating a configuration of a reader according to an embodiment of the present invention, and FIG. 4 is a diagram for explaining a signal detector shown in FIG.

Referring to FIG. 3, the reader 200 includes a receiving unit (not shown), a threshold setting unit 210, a channel estimating unit 220, and a signal detecting unit 230.

The receiving unit receives a plurality of signals from the powerless sensor node having a plurality of antennas to which power of different sizes is allocated. Here, the receiving unit may be, for example, an antenna.

The threshold value setting unit 210 sets a threshold value using the received power of the preamble signal sent from the powerless sensor node in the initial communication process with the powerless sensor node. The preamble signal is a signal promised between the powerless sensor node and the reader 200, that is, a signal that is known in advance.

The powerless sensor node transmits a preamble signal to the reader 200 before the actual uplink communication, and the threshold setting unit 210 sets a threshold value based on the preamble signal received from the powerless sensor node do. That is, the powerless sensor node transmits a preamble signal to the reader 200 by reflecting a radio signal through a plurality of antennas to which power of different sizes is allocated. Then, the threshold value setting unit 210 can set the respective threshold values for discriminating the information bits carried on each antenna by using the preamble signal.

When transmitting information by 1 bit in each antenna of the powerless sensor node, the threshold value setting unit 210 sets the power of the subcarriers of the same index to the power when the preamble bits are '1' and '0' The magnitudes can be compared and the thresholds can be set by averaging all the power magnitudes selected by the comparison.

)을 산출할 수 있다. For example, when the preamble bit is '10101010', the threshold setting unit 210 sets a threshold value (

) Can be calculated.

는 임계값이고,

는 프리앰블 비트에 해당하는 전력 크기일 수 있다. here,

Is a threshold value,

May be a power magnitude corresponding to a preamble bit.

In addition, when transmitting information by 2 bits in each antenna of the power-free sensor node 100, the threshold setting unit 210 sets the power magnitudes for each of the preamble bits '11' and '00' A threshold is set for each of the preamble bits when the preamble bits are '01' and '10', and a threshold value when the preamble bit is '11' and a threshold value when the preamble bit is '00' The threshold value can be set individually.

 For example, if the preamble bit is '10101010' and each antenna of the powerless sensor node 100 transmits 2 bits, the threshold setting unit 210 calculates a threshold value using Equation (2) can do.

The channel estimator 220 estimates channel information from a radio signal received from the access point and the power-free sensor node. That is, the channel estimation unit 220 can estimate channel information including two paths using the radio signal received through two paths (access point to reader, access point to powerless sensor node to reader) .

For example, when the power-free sensor node is provided with a first antenna and a second antenna, the channel estimation unit 220 estimates a channel 1 ( _htr1 ) between the first antenna and the reader, a channel 2 ( _htr1 ) between the second antenna and the reader h _tr2 ).

The signal detector 230 detects the first signal having the largest power among the plurality of signals received from the plurality of antennas of the powerless sensor node and detects the remaining signal using the estimated channel information and the first signal. That is, the signal detector 230 measures a power magnitude of signals received from the powerless sensor node, and detects a first signal having the largest measured power magnitude. At this time, the signal detector 230 may detect the first signal having the largest power size using the power level of each preamble signal received from each antenna of the powerless sensor node before the uplink communication. When the first signal having the largest power is detected, the signal detector 230 can perform a difference operation on the estimated channel information and the first signal with respect to the received signal to detect the remaining signal.

Hereinafter, a method in which the signal detection unit 230 detects a signal when the powerless sensor node has two antennas will be described with reference to FIG.

The reader 200 receives wireless signals from the access point and the powerless sensor node. Accordingly, all the signals y _reader (t) received by the reader 200 can be signals as shown in Equation (3) below.

(t)는 리더기에서 수신받은 신호,

는 액세스 포인트로부터 발생한 신호, h_ar(t)는 액세스 포인트와 리더기 사이의 채널, h_at(t)는 액세스 포인트와 무전력 센서노드(100) 사이의 채널, h_tr1 은 무전력 센서노드의 제1 안테나와 리더기 사이의 채널, h_tr2 은 무전력 센서노드의 제2 안테나와 리더기 사이의 채널,

는 평균이 '0'이고 분산이

인 AWGN(Additive White Gaussian Noise)잡음을 의미한다. AP신호는 액세스 포인트로부터 수신한 신호이고, 태그신호는 무전력 센서노드 각각의 안테나로부터 수신한 신호일 수 있다.

는 무전력 센서 노드의 각각의 안테나에서 신호를 반사시킬 때 '1', 신호를 반사시키지 않을 때 '0'으로, 그 값은 임계값을 통해 판단될 수 있다. 예를 들어, 무전력 센서 노드가 하나의 패킷 당 하나의 비트를 전송하는 경우, 리더기(200)는 무전력 센서 노드가 백스캐터링한 신호의 크기(전력 크기)를 기 설정된 임계값과 비교하여, 임계값 이상이면 '1'의 비트, 임계값 미만이면 '0'의 비트로

를 판단할 수 있다. 또한, 무전력 센서노드가 하나의 패킷 당 두개의 비트를 전송하는 경우, 리더기(200)는 무전력 센서노드의 각 안테나로부터 수신한 신호의 전력 크기를 임계값과 비교하여,

가 '00', '01', '10' 또는 '11'인지 판단할 수 있다. here,

(t) is the signal received by the reader,

The second signal, h _ar (t) is between the access between the point and the reader channel, h _at (t) is the access point and the non-power sensor node 100 channel, h _tr1 is no power sensor node generated from the access point 1 denotes a channel between the antenna and the reader, _htr2 denotes a channel between the second antenna and the reader of the _powerless sensor node,

The average is '0' and the variance is

Quot; Additive White Gaussian Noise (AWGN) noise " The AP signal is a signal received from the access point, and the tag signal may be a signal received from the antenna of each powerless sensor node.

Is '1' when the signal is reflected by each antenna of the powerless sensor node, and '0' when it does not reflect the signal, and the value can be judged through the threshold value. For example, if the powerless sensor node transmits one bit per packet, the reader 200 compares the size (power size) of the signal backscattered by the powerless sensor node with a preset threshold value, If it is greater than or equal to the threshold value, the bit is set to '1'. If the threshold value is less than the threshold value,

Can be determined. Also, if the powerless sensor node transmits two bits per packet, the reader 200 compares the power magnitude of the signal received from each antenna of the powerless sensor node with a threshold value,

01 "," 10 ", or " 11 ".

)를 검출한다. 즉, 신호 검출부(230)는 무전력 센서 노드로부터 수신받은 신호들의 전력 크기를 측정하고, 전력 크기가 가장 큰 안테나로부터 전송된 제1 신호(

)를 검출할 수 있다. The signal detecting unit 230 detects a first signal having the largest power among the plurality of signals received through the plurality of antennas of the powerless sensor node

). That is, the signal detector 230 measures a power magnitude of signals received from the powerless sensor node, and outputs a first signal ("

Can be detected.

When the first signal of the largest power is detected, the signal detector 230 detects the first signal, the first antenna transmitting the signal of the antenna having the largest channel and the estimated channel in the access period and the reader period, The second signal can be detected by subtracting the signal by the channel from the previously received signal. That is, the signal detector can detect the second signal y ₂ (t) using Equation 4 described below.

는 먼저 검출된 제1 신호,

는 액세스 포인트와 리더기 간에 추정된 채널,

는 액세스 포인트와 태그 간에 추정된 채널,

태그의 제1 안테나와 리더기 사이에 추정된 채널을 의미할 수 있다.

는 액세스 포인트와 리더기간에 추정된 채널에 의한 신호,

는 태그의 제1 안태나와 리더기 간에 추정된 채널에 의한 신호를 의미한다. Here, y _reader (t) represents all the signals received by the _reader (corresponding to Equation (1)),

The first signal detected first,

Is an estimated channel between the access point and the reader,

Is the estimated channel between the access point and the tag,

And may be an estimated channel between the first antenna of the tag and the reader.

A signal due to the channel estimated by the access point and the reader period,

Denotes a signal due to a channel estimated between the first mode of the tag and the reader.

In Equation (4), the signal due to the channel estimated by the access point and the interrogator can be subtracted from the received signal to account for the interference signal caused by the access point. .

As described above, the signal detector 230 detects the remaining signals using the signals transmitted from the antennas having the highest power, so that it is not necessary to detect all the signals transmitted from the plurality of antennas of the powerless sensor node, The detection performance is improved.

5 is a diagram for explaining an uplink communication method in a backscatter system according to an embodiment of the present invention.

Referring to FIG. 5, the access point 300 broadcasts a radio signal (S510). That is, the access point 300 transmits a radio signal to the reader 200 and the powerless sensor node 100 in the vicinity.

When step S510 is performed, the powerless sensor node 100 allocates power of different sizes to the plurality of antennas, and reflects the wireless signal (S520). That is, the powerless sensor node 100 can transmit the information to be sent to the reader 200 to the wireless signal received from the access point 300, and transmit the information to the reader 200.

When step S520 is performed, the reader 200 estimates channel information of a plurality of signals received from the power-free sensor node 100 (S530), and selects a signal having the largest power among the plurality of received signals ( S540). That is, since the powerless sensor node 100 transmits signals with different powers, the reader 200 can select the signal with the largest power. At this time, the reader 200 can select the signal having the largest power using the power level of the preamble included in the received signal.

Although it has been described herein that the signal is selected after the channel estimation, the order of steps S530 and S540 may be changed.

When step S540 is performed, the reader 200 detects the remaining signal using the estimated channel information and the detected signal (S550). That is, the reader 200 can calculate the difference between the detected signal and the received signal to detect the remaining signal. At this time, the reader 200 may subtract a signal based on the estimated channel between the access point 300 and the reader 200 from the received signal so as to consider the interference signal by the access point 300.

와

의 전력이 할당된 경우이다. 도 5를 참조하면, 본 발명의 백스캐터 시스템에서 더 큰 전력을 할당한 첫 번째 안테나의 성능은 기존 백스캐터 시스템보다 우수하지만, 더 적은 전력을 할당한 두 번째 안테나의 성능은 기존 백스캐터 시스템보다 성능이 열화 된 것을 알 수 있다.6 is a graph showing a comparison of error performance between a conventional backscatter system and a backscatter system according to an embodiment of the present invention. In the performance comparison, the distance between the powerless sensor node 100 and the reader is 1 m, 3 m, and 5 m,

Wow

Quot; is allocated. Referring to FIG. 5, the performance of the first antenna that allocates a larger power in the backscatter system of the present invention is better than that of the conventional backscatter system, but the performance of the second antenna that allocates less power is higher than that of the conventional backscatter system The performance deteriorates.

와

의 전력이 할당된 경우의 성능 그래프를 나타낸다. 도 5에 비해 각각의 안테나에서의 전력 차이가 더 크기 때문에 첫 번째 안테나의 신호검출 성능이 향상된 것을 알 수 있다.FIG. 7 is a block diagram of a backscatter system according to an embodiment of the present invention.

Wow

Of power is allocated to each of the nodes. It can be seen that the signal detection performance of the first antenna is improved because the power difference in each antenna is larger than in FIG.

8 is a graph showing a data rate of a conventional backscatter system and a backscatter system according to an embodiment of the present invention. Referring to FIG. 8, it can be seen that a higher data rate is obtained by using multiple antennas as compared with the conventional backscatter system.

The above-described embodiments of the present invention can be embodied in a general-purpose digital computer that can be embodied as a program that can be executed by a computer and operates the program using a computer-readable recording medium.

The computer readable recording medium includes a magnetic storage medium (e.g., ROM, floppy disk, hard disk, etc.), optical reading medium (e.g., CD ROM, DVD, etc.).

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100: No power sensor node
110: antenna
120: Power allocation unit
200: reader
210: threshold value setting unit
220: channel estimation unit
230: Signal detector
300: access point

Claims (16)

The access point broadcasting a radio signal;
The powerless sensor node allocates power of different magnitudes to a plurality of antennas and each of the plurality of antennas reflects the wireless signal with the allocated power of different sizes to transmit information; And
The reader detects a first signal having the largest power among a plurality of signals received from the powerless sensor node and detects a remaining signal using the detected first signal and the estimated channel information
And transmitting the uplink data to the base station.
The method according to claim 1,
Wherein the access point is configured to, after broadcasting the wireless signal,
Wherein the powerless sensor node reflects the radio signal through the plurality of antennas and transmits a preamble bit to the reader; And
Wherein the reader further comprises a step of setting a threshold for discrimination of information bits using the preamble bit.
3. The method of claim 2,
The step of setting the threshold value
The thresholds are set by averaging all the power magnitudes when the preamble bits are '1' and when the preamble bits are '0', when the antennas of the powerless sensor node transmit 1 bit at a time, Uplink communication method using a backscatter system.
3. The method of claim 2,
The step of setting the threshold value
And a threshold value is set by averaging all the power magnitudes when the preamble bits are '11' and when the preamble bits are '00' in each antenna of the powerless sensor node, Is set to a threshold value when the preamble bit is '11' and a threshold value when the preamble bit is '00' for each of '01' and '10' Uplink communication method using CATAR system.
The method according to claim 1,
The step of detecting the remaining signal comprises:
Detecting a first signal having the largest power among a plurality of signals received from the powerless sensor node;
Estimating channel information from a wireless signal received from the access point and the powerless sensor node; And
And calculating a difference between the estimated channel information and the detected first signal based on the received signal to detect a remaining signal.
6. The method of claim 5,
The first signal of the largest power
And detecting the power level of each of the plurality of signals and detecting the power level of the preamble signal received from each antenna of the detected or null power sensor node.
6. The method of claim 5,
And the estimated channel information and the signal based on the detected first signal,
And a signal based on a channel estimated between a reader and an antenna of a powerless sensor node that transmits the first signal and a channel estimated between the access point and the reader. Communication method.
An access point for broadcasting a wireless signal;
A power-free sensor node that allocates power of different sizes to a plurality of antennas, and each of the plurality of antennas reflects the wireless signal with the allocated power of different sizes to transmit information; And
A reader for detecting a first signal having the largest power among a plurality of signals received from the powerless sensor node and detecting a remaining signal using the detected first signal and the estimated channel information,
/ RTI >
9. The method of claim 8,
Wherein the powerless sensor node reflects the radio signal through the plurality of antennas and transmits a preamble bit to the reader,
Wherein the reader sets a threshold value for discriminating information bits using the preamble bits.
9. The method of claim 8,
The reader
Detecting a first signal having the largest power among a plurality of signals received from the powerless sensor node, estimating channel information from a radio signal received from the access point and the powerless sensor node, And a difference signal detecting unit for detecting a difference between the first signal and the second signal.
A receiver for receiving a plurality of signals from a powerless sensor node provided with a plurality of antennas having different sizes of power;
A channel estimator for estimating channel information from a signal received from the access point and the power-free sensor node; And
A signal detector for detecting a first signal having the largest power among the plurality of signals and calculating a difference between the estimated channel information and a signal based on the detected first signal on the basis of the received signal,
And a detector for detecting the signal in the backscatter system.
12. The method of claim 11,
And a threshold value setting unit for setting a threshold value for discriminating information bits using the preamble signal received from the powerless sensor node.
13. The method of claim 12,
The threshold value setting unit
When the bits of the preamble signal are '1' and '0', the power magnitudes are all averaged to set a threshold value when transmitting the 1 bit by each antenna of the powerless sensor node A device for signal detection in a backscatter system.
13. The method of claim 12,
The threshold value setting unit
When the bits of the preamble signal are '11' and '00', the threshold values are respectively set by averaging the power magnitudes for each of the antennas of the powerless sensor node, A threshold value when the bit of the preamble signal is '11' and a threshold value when the bit of the preamble signal is '00' are respectively set for each of the bits when the bits of the preamble signal are '01' and '10' Wherein the backscattering system comprises:
12. The method of claim 11,
The signal detector
Detecting the first signal of the largest power by measuring the power magnitude of each of the plurality of signals or detecting the first signal of the largest power using the power magnitude of the preamble signal received from each antenna of the powerless sensor node A device for signal detection in a backscatter system.
12. The method of claim 11,
And the estimated channel information and the signal based on the detected first signal,
And a signal based on a channel estimated between the reader and the antenna of the powerless sensor node that transmitted the first signal and a channel estimated between the access point and the reader. .

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