KR101645996B1 - Ofdm symbol transmiting using espar antenna in beamspace mimo system - Google Patents

Abstract

The present invention discloses an ESPAR antenna transmitter and a method for transmitting multiple OFDM symbols in a beam-space MIMO environment. A method for transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beam-space MIMO system according to an embodiment of the present invention is characterized in that a beam pattern of a beam-space MIMO system is applied to multiple OFDM symbols under a plurality of constraint conditions And a second current value that is implemented through the ESPAR antenna transmitter and is applied to the active antenna and the plurality of parasitic antennas disposed around the active antenna, respectively, to minimize the difference between the first current value and the second current value, Calculating; And transmitting the multiple OFDM symbols by applying the calculated parameters to the ESPAR antenna transmitters. The variable includes a matrix representing a beam pattern, a voltage value applied to the active antenna through an RF chain connected to the active antenna, and an impedance value connected to the parasitic antenna.

Description

Technical Field [0001] The present invention relates to a method and an apparatus for transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beam-space MIMO system,

The present invention relates to a method for transmitting independent multiple OFDM symbols via an ESPAR antenna transmitter in a beam-space MIMO system and an ESPAR antenna transmitter transmitter in a beam-space MIMO environment.

OFDM systems are used in wireless LAN and LTE environments. In the modern communication system, an OFDM system that transmits signals using a plurality of sub-carriers is combined with a multiple input multiple output (MIMO) system.

However, since a multiple input / multiple output (MIMO) system with multiple antennas includes a plurality of antennas and a plurality of RF chains connected to them in a limited space, it is possible to increase the complexity of hardware, increase interference between plural RF chains, A systematic burden problem arises.

In order to solve this problem, an active antenna including a plurality of parasitic antennas disposed around the active antenna and a mutual coupling phenomenon between the active antenna and the parasitic antenna Electronically Steerable Parasitic Array Radiator (ESPAR) has been proposed, and communication technologies using ESPAR in a MIMO system are being studied.

On the other hand, in order to transmit the OFDM signal without distortion in the ESPAR transmitter, a large range of impedances are required, so that an impedance matching problem occurs and a negative resistance is required, which may cause the transmitter to oscillate. In addition, a large range of currents can cause high PAPR. Therefore, a new method for calculating the beam design, impedance value, and voltage value of the beam space MIMO to solve this problem is required.

US Pat. No. 8,446,318 (entitled " Controlling A Beamforming Antenna Using Reconfigurable Parasitic Elements ") discloses a general concept for ESPAR, and the paper A. Kalis, AG Kanatas, and CB Papadias, " A novel (IEEE J. Select. Areas Commun., vol. 26, no. 6, pp. 972-980, Aug. 2008.) discloses a method for generating three or five parasitic antennas (2x2 MIMO or the like) which implements two or three sub-channels for the case where the modulation scheme is PSK (BPSK, QPSK, 16-PSK).

In an embodiment of the present invention, when a plurality of independent OFDM symbols are transmitted through an ESPAR antenna transmitter in a beam-space MIMO system under a plurality of constraint conditions, a matrix representing a beam pattern is mapped to independent multiple OFDM symbols, A matrix representing a beam pattern of a beam space MIMO system that minimizes a difference between a first current value and a second current value implemented through an ESPAR antenna transmitter and applied to an active antenna and a parasitic antenna, Values, and impedance values, and to provide a transmitter.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may be present.

A method for transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beam-space MIMO system according to an embodiment of the present invention includes the steps of, for a plurality of OFDM symbols, A difference between a first current value calculated by mapping a matrix representing a pattern and a second current value that is implemented through the ESPAR antenna transmitter and applied to each of a plurality of parasitic antennas disposed around the active antenna and the active antenna is minimized Calculating a variable to be used; And transmitting the multiple OFDM symbols by applying the calculated parameters to the ESPAR antenna transmitter.

The variable includes a matrix representing the beam pattern, a voltage value applied to the active antenna through an RF chain connected to the active antenna, and an impedance value connected to the parasitic antenna.

Also, an ESPAR antenna transmitter in a beam space MIMO environment according to an embodiment of the present invention includes: an active antenna; A plurality of parasitic antennas disposed around the active antenna; An impedance matching unit for performing impedance matching on a resistance value connected to the active antenna and an impedance value connected to the parasitic antenna; And an RF chain connected to the active antenna to apply a voltage value to the active antenna.

In this case, the matrix representing the beam pattern of the beam-space MIMO system, the voltage value, and the impedance value may be calculated by mapping a matrix representing the beam pattern to independent multiple OFDM symbols under a plurality of constraint conditions, Current value and a second current value, which is implemented through the ESPAR antenna transmitter and is applied to the active antenna and the parasitic antenna, respectively, is minimized.

According to an embodiment of the present invention, by transmitting an OFDM symbol through an ESPAR antenna transmitter including an active antenna connected to a single RF chain and a parasitic antenna disposed around the RF antenna, the RF hardware complexity problem, The power consumption problem can be solved.

Also, according to an embodiment of the present invention, when an OFDM symbol is transmitted through an ESPAR antenna transmitter including an active antenna connected to a single RF chain and a parasitic antenna disposed around the active antenna, a beam- And a second current value applied to each of the plurality of parasitic antennas disposed around the active antenna is minimized, thereby calculating and applying an optimum variable to the first current value, which is calculated by mapping a matrix representing the beam pattern of the first antenna, It is possible to prevent the parasitic antenna from flowing into the parasitic antenna according to the radiation of the active antenna.

In addition, in the optimal parameter calculation, the range condition for the resistance value and the reactance value, the range condition for the magnitude of the voltage value, the constraint condition for the subchannel used for transmission, the range condition for the input impedance connected to the RF chain, (RAP) problem caused by OFDM signal transmission, an oscillation problem due to a negative resistance value, and impedance matching problems by applying a constraint on a rank of a matrix representing a pattern. Troubleshooting may be possible.

1 is a view for explaining a structure of an ESPAR antenna.
FIG. 2 illustrates an ESPAR antenna transmitter in a beam-space MIMO environment according to an embodiment of the present invention. Referring to FIG.
3 is a flowchart illustrating a method of transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beam-space MIMO system according to an embodiment of the present invention.
4 is a diagram for explaining an example of a process of calculating a variable in more detail.
5 is a diagram illustrating an example in which a difference between a first current value and a second current value converges as a process of calculating a variable is repeated.
FIGS. 6 to 8 are diagrams for explaining the performance of a transmitter to which the multiple OFDM symbol transmission method proposed in the present invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

In the following description with reference to the drawings, the same reference numerals will be used to designate the same names, and the reference numerals are merely for convenience of description, and the concepts, features, and functions Or the effect is not limited to interpretation.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "including" an element, it is to be understood that the element may include other elements as well as other elements, And does not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

SUMMARY OF THE INVENTION The present invention is based on the finding that a PAPR problem due to a large area impedance and voltage value caused by transmission of independent multiple OFDM symbols through an ESPAR antenna transmitter in a beamspace MIMO system, And a method of designing an optimal beam for solving the problem of impedance matching due to impedance variation of a large area.

SUMMARY OF THE INVENTION In order to design an optimal beam for transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beamspace MIMO system, A difference between a first current value calculated by mapping a matrix representing a beam pattern of the system and a second current value implemented by an ESPAR antenna transmitter and applied to a plurality of parasitic antennas disposed around the active antenna and the active antenna, A calculation method for calculating a variable to be minimized is provided.

The present invention also provides a method for multiplexing and transmitting two independent OFDM symbols for a 3-elements ESPAR antenna featuring a single RF chain structure. However, this is merely for convenience of explanation and can easily be extended to a parasitic antenna based transmitter featuring a small number of RF chains and a plurality of parasitic antennas, and multiplexing independent OFDM symbols below the total number of antennas It is possible to transmit the data.

Hereinafter, a method for transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter and an ESPAR antenna transmitter in a beam-space MIMO environment in a beam space MIMO system proposed in the present invention will be described in detail with reference to the accompanying drawings.

1 is a view for explaining a structure of an ESPAR antenna.

The ESPAR antenna 100 according to an exemplary embodiment of the present invention includes an active antenna 110, parasitic antennas 120 to 125, a load resistor (50 ohms) connected to an active antenna, variable impedances 130 to 135 connected to a parasitic antenna, .

The active antenna 110 forms an antenna beam through an active element (variable capacitance element). At this time, the active antenna includes a load resistor (50 ohms) connected to the (110) active antenna.

The parasitic antennas 120 to 125 adjust the reactance values of the variable impedances 130 to 135 connected to the parasitic antenna to form a beam which mutually couples the beam with the active antenna.

On the other hand, since the parasitic antenna is composed of the active antenna, the energy radiated from the active antenna connected to the RF chain may induce parasitic antennas. Therefore, in order to modify the current induced in the parasitic antenna, the variable impedance value connected to each parasitic antenna is adjusted, and the desired current value can be applied to the parasitic antenna. Here, the elements for controlling the impedance may be composed of a capacitor, an inductor, and positive / negative resistors. The adjustment of the values may be performed by a switching method, In the case of capacitors and inductors, passive regulation can be achieved by using varactor elements.

FIG. 2 illustrates an ESPAR antenna transmitter in a beam-space MIMO environment according to an embodiment of the present invention. Referring to FIG.

An ESPAR antenna transmitter 100 in a beam space MIMO environment according to an embodiment of the present invention includes an active antenna 120, parasitic antennas 121 and 122, a load resistor 130 connected to each antenna, variable impedances 131 and 132, An impedance matching unit 140, an RF chain 150, and a calculation module 160.

The active antenna 120 is connected to a single RF chain.

The parasitic antennas 121 and 122 are disposed around the active antenna 122.

At this time. The parasitic antennas 121 and 122 are designed such that the radiant energy of the active antenna is not introduced, and the beam pattern can be designed such that mutual coupling is made with the beam emitted from the active antenna.

The impedance matching unit 140 performs impedance matching on a resistance value connected to the active antenna and an impedance value connected to the parasitic antenna.

The RF chain 150 is connected to the active antenna to apply a voltage value to the active antenna.

The resistance 130 and the impedances 131 and 132 connected to each antenna are a load resistance and a load impedance value for impedance matching. The resistance value connected to the active antenna is impedance matching at 50 ohms, and the load impedance connected to the parasitic antenna is variably controlled in order to modify the current flowing due to radiation of the active antenna.

The calculation module 160 calculates the matrix, voltage value, and impedance value representing the beam pattern of the beam space MIMO system described above by mapping a matrix representing a beam pattern for independent multiple OFDM symbols under a plurality of constraint conditions And the second current value, which is implemented through the ESPAR antenna transmitter and applied to the active antenna and the parasitic antenna, respectively, is minimized.

3 is a flowchart illustrating a method of transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beam-space MIMO system according to an embodiment of the present invention.

A method of transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter in a beam-space MIMO system according to an exemplary embodiment of the present invention includes calculating a variable for minimizing a first current value and a second current value (S410) , And transmitting the OFDM symbol using the calculated variable (S420).

,

,

값)과, ESPAR 안테나 송신기를 통해 구현되어 능동 안테나 및 능동 안테나의 둘레에 배치된 다수의 기생 안테나로 각각 인가되는 제 2 전류 값(예를 들어, 도 2의

,

,

값) 간의 차이가 최소화되도록 하는 변수를 산출한다.In step S410, a first current value calculated by mapping a matrix representing a beam pattern of the beam-space MIMO system to multiple OFDM symbols under a plurality of constraint conditions (for example,

,

,

And a second current value that is implemented through the ESPAR antenna transmitter and applied to a plurality of parasitic antennas disposed around the active antenna and the active antenna, respectively (e.g.,

,

,

Value) is minimized.

Next, S420 transmits the multiple OFDM symbols using the calculated parameters for the ESPAR antenna transmitter. In this case, the variable includes a matrix representing a beam pattern, a voltage value applied to the active antenna through an RF chain connected to the active antenna, and an impedance value connected to the parasitic antenna.

For example, independent multiple OFDM symbol transmission of an ESAPR antenna transmitter (3-elements ESPAR structure) according to an exemplary embodiment of the present invention calculates a beam space MIMO operation procedure and a load variable, And then transmitting the OFDM symbols.

First, a beam space MIMO operation is a process of mapping an OFDM sample independent of a vector generating each beam pattern for one sample time from two independent OFDM symbols. For example, a beamspace MIMO operation for K subcarriers OFDM symbols consisting of K subcarriers can be expressed by Equation (1).

Next, the process of calculating the variable and calculating the calculated variable calculates the optimal variable value, and the process transmits the OFDM symbol by applying the calculated variable value. Here, the variable may include a voltage value applied to the active antenna through an RF chain connected to the active antenna, and an impedance value connected to the parasitic antenna.

At this time, the variable is a current value ((= (i-1)) that is a current value (i = i) to be transmitted through the beam space MIMO operation is correctly applied to each ESPAR antenna (ESPAR i in FIG. 2) implemented in the ESPAR antenna) may be a value calculated so as to minimize the difference.

For example, a variable (for example, a load impedance value connected to a parasitic antenna) is a variable impedance value that can modify the current so that the energy radiated from the active antenna is not induced in the parasitic antennas.

)는 독립적인 다중 OFDM 심볼에 대하여 빔 패턴을 나타내는 행렬을 맵핑하여 계산된 제 1 전류 값(

)과, ESPAR 안테나 송신기를 통해 구현되어 능동 안테나 및 기생 안테나로 각각 인가되는 제 2 전류 값(

) 간의 차이가 최소화되도록 하는 부하 임피던스값 (impedance load)

와

과 상관관계가 있다.Also, a variable (e.g., voltage value

) Maps a matrix representing a beam pattern for independent multiple OFDM symbols to a first current value

), And a second current value that is implemented through the ESPAR antenna transmitter and applied to the active antenna and the parasitic antenna, respectively

) To minimize the difference between the load impedance value (impedance load)

Wow

.

,

는 독립적인 다중 OFDM 심볼에 대하여 빔 패턴을 나타내는 행렬을 맵핑하여 계산된 제 1 전류 값(

)과, ESPAR 안테나 송신기를 통해 구현되어 능동 안테나 및 기생 안테나로 각각 인가되는 제 2 전류 값(

) 간의 차이가 최소화되도록 하는 [수학식 2]를 통해 도출될 수 있다. 여기서,

는 RF 체인으로부터의 전압 값으로 능동안테나에 인가되는 전압이고, 50 옴은 능동 안테나에 연결된 임피던스 값(주로 임피던스 매칭 역할을 위해 사용)이며,

와

는 기생 안테나에 연결된 가변 임피던스 값을 타나낸다. 또한,

는 안테나들간의 상호 결합(mutual coupling) 행렬을 나타낸다.Therefore,

,

A first current value calculated by mapping a matrix representing a beam pattern for independent multiple OFDM symbols

), And a second current value that is implemented through the ESPAR antenna transmitter and applied to the active antenna and the parasitic antenna, respectively

≪ / RTI > that minimizes the difference between < RTI ID = 0.0 > here,

Is the voltage applied to the active antenna as a voltage value from the RF chain, 50 ohms is the impedance value (mainly used for impedance matching) connected to the active antenna,

Wow

Shows the variable impedance value connected to the parasitic antenna. Also,

Represents a mutual coupling matrix between antennas.

Specifically, Equation (2) can be expressed as Equation (3) below.

Therefore, [Equation 3] can be expressed as Equation 4 below.

)은 하기 [수학식 5]에 의해서 도출될 수 있다. Also, a second current value (< RTI ID = 0.0 >

) Can be derived by the following equation (5).

과 기생안테나에 연결된 부하 임피던스값 (parasitic impedance load)

,

를 구할 수 있다.Therefore, by referring to Equations (1) and (5), the following Equation (6) can be obtained and the voltage value

And a parasitic impedance load connected to the parasitic antenna.

,

Can be obtained.

과 기생안테나에 연결된 부하 임피던스값 (Parasitic Impedance Load)

,

역시 큰 범위를 가지게 되어 여러가지 문제가 발생할 수 있다. 예를 들면, 임피던스 값들의 범위가 커지게 될 경우 시스템의 발진 문제를 발생시키는 음의 저항이 요구되는 경우가 발생할 수 있다.However, when OFDM symbols are transmitted, since the range of the dynamic range is large, the voltage value applied from the RF chain of Equation (6)

And the parasitic impedance load (Parasitic Impedance Load)

,

There is also a large range that can cause various problems. For example, when the range of the impedance values becomes large, a negative resistance that causes an oscillation problem of the system may be required.

Therefore, in order to solve the problem that may occur in transmission of OFDM symbols, the variable calculation according to an embodiment of the present invention may be classified into impedance and load condition constraints for a resistance value and a reactance value, PAPR constraints on the magnitude of the value, impedance matching constraints on the input impedance connected to the RF chain, channel constraints on the subchannels used in transmission, rank of the matrix representing the beam pattern Constraints on rank constraints can be considered.

Here, B is a matrix representing a beam pattern, v is a voltage value applied to an active antenna through an RF chain, x is an impedance value of a parasitic antenna, and s is an OFDM symbol. Here, each variable can be calculated according to a constraint condition.

The impedance condition of the resistance value and the reactance value are limited to the range of resistance of the device that varies the impedance of the parasitic antenna . In other words, the designer can set impedance conditions for the impedance and reactance values to limit impedance values that can be implemented, thereby preventing the negative resistance value from being set. In addition, the positive resistance range Can be set to reduce power consumption.

The range condition (PAPR constraints) for the magnitude of the voltage value may have a high PAPR characteristic due to the OFDM signal. To solve this problem, the magnitude of the input voltage value of the RF chain is limited. That is, the designer can set the PAPR constraints on the magnitude of the voltage value to limit the variation of the voltage value to maximize the efficiency of the power amplifier used.

The channel constraints for the subchannels used in the transmission are such that when the channel information is available to the transmitter, the beams belong to a space in which the dominant directions of the channel span, And to limit the value to be large. Here, the dominant direction means a space composed of vectors corresponding to a dominant singular value among the singular vectors of the channel.

가 발생되어 임피던스 매칭 회로에 영향을 주게 되는데, 이때, 입력 임피던스

의 범위에 제한을 두어 임피던스 매칭 회로를 간소화를 위해 제한하는 것이다. 즉, 설계자는 신호로 인해 다이나믹 레인지(dynamic range)의 입력 임피던스 범위에 제한을 둠으로써, 입력 임피던스의 변화량을 제한시켜 임피던스 매칭 회로의 복잡도를 낮출 수 있다.Impedance matching constraints on the input impedance connected to the RF chain are due to the input impedance of the dynamic range due to the OFDM signal.

Is generated to affect the impedance matching circuit. At this time, the input impedance

To limit the impedance matching circuit for simplicity. That is, the designer limits the input impedance range of the dynamic range due to the signal, thereby reducing the complexity of the impedance matching circuit by limiting the variation of the input impedance.

Rank constraints on the rank of the matrix representing the beam pattern are limited to prevent the rank of the beam matrix from being insufficient than the number of beams to be transmitted. In this case, there is a method of directly limiting the rank of the beam and a method of limiting the singular value range of the beam matrix indirectly.

However, Equation (7) is a non-convex problem and it is not easy to derive a solution value for various variables at once. Therefore, it is possible to calculate optimal variable values by performing alternating calculations by separating two convex problems as in the following embodiments.

 According to an embodiment of the present invention, the step of calculating the variable may include re-executing the first calculation step, the second calculation step and the first calculation step.

 The first calculation step calculates a voltage value (V1) by using an initial matrix representing an arbitrary beam pattern under a constraint condition of at least one of a resistance condition for determining an impedance value, a range condition for a reactance value, And the impedance value can be calculated. At this time, the first calculation step can be calculated according to the following equation (8).

은 제 1 기생 안테나의 임피던스 값,

는 제 2 기생 안테나의 임피던스 값, s는 OFDM 심볼, Z는 상기 능동 안테나와 상기 기생 안테나 간의 상호 커플링을 나타내는 행렬을 나타낸다.Here, B is a matrix representing a beam pattern, v is a voltage value,

Is an impedance value of the first parasitic antenna,

Represents an impedance value of the second parasitic antenna, s represents an OFDM symbol, and Z represents a matrix representing mutual coupling between the active antenna and the parasitic antenna.

Next, the second calculation step includes a constraint on a subchannel used in transmission of multiple OFDM symbols, a range condition on an input impedance connected to an RF chain, and a constraint on a rank of a matrix representing a beam pattern A matrix representing the beam pattern is calculated using the values calculated through the first calculation step under at least any one constraint condition. At this time, the second calculation step can be calculated according to the following equation (9).

은 제 1 기생 안테나의 임피던스 값,

는 제 2 기생 안테나의 임피던스 값, s는 OFDM 심볼, Z는 상기 능동 안테나와 상기 기생 안테나 간의 상호 커플링을 나타내는 행렬을 나타낸다.Where B is a matrix representing a beam pattern, v is the voltage value,

Is an impedance value of the first parasitic antenna,

Represents an impedance value of the second parasitic antenna, s represents an OFDM symbol, and Z represents a matrix representing mutual coupling between the active antenna and the parasitic antenna.

Finally, the re-executing step re-executes the first calculation step using the matrix calculated through the second calculation step instead of the initial matrix. At this time, the second calculation step is performed again using the values calculated through the re-performed first calculation step, and an iterative calculation step is performed to re-execute the first calculation step using the matrix calculated through the re- . ≪ / RTI > At this time, the iterative calculation step may be repeatedly performed until a variable converging the difference between the first current value and the second current value is calculated. That is, it is repeatedly calculated until the following equation (10) converges.

4 is a diagram for explaining an example of a process of calculating a variable in more detail.

Referring to FIG. 4, first, in step (1), the impedance of the RF chain / the impedance connected to each antenna is calculated. At this time, the calculation can be performed by setting a constraint condition of at least one of a resistance value for determining the impedance value, a range condition for the reactance value, and a range condition for the magnitude of the voltage value.

Next, in (2), a beam pattern matrix calculation is performed. At this time, at least one of constraints on a subchannel used for transmission of an OFDM symbol, a range condition for an input impedance connected to an RF chain, and a constraint for a rank of a matrix representing a beam pattern .

Finally, in (3), (1) is performed after (2), and the result is repeatedly calculated to calculate the optimal variable value. At this time, the iterative calculation can be performed until a variable value in which the difference between the first current value and the second current value is minimized is calculated.

Meanwhile, the application order of the constraint conditions and the number of application of the constraint conditions considered in the processes (1), (2), and (3) of FIG. 4 are only one embodiment of the present invention. The application order and the number of application of the constraint can be changed.

5, it can be seen that the error converges to 0 or a constant value as the process of calculating the variable continues.

In an ESPAR antenna transmitter and a beam-space MIMO system in the beam-space MIMO system described above, it is possible to transmit OFDM symbols without distortion through a method of transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter.

In addition, according to an embodiment of the present invention, an OFDM symbol is transmitted through an ESPAR antenna transmitter including an active antenna connected to a single RF chain and a parasitic antenna disposed around the active antenna, thereby improving RF hardware complexity, , The circuit power consumption problem can be solved.

Also, according to an embodiment of the present invention, when an OFDM symbol is transmitted through an ESPAR antenna transmitter including an active antenna connected to a single RF chain and a parasitic antenna disposed around the active antenna, a beam- And a second current value applied to each of the plurality of parasitic antennas disposed around the active antenna is minimized, thereby calculating and applying an optimum variable to the first current value, which is calculated by mapping a matrix representing the beam pattern of the first antenna, It is possible to prevent the current from flowing into the parasitic antenna according to the radiation of the active antenna.

In addition, in the optimal parameter calculation, the range condition for the resistance value and the reactance value, the range condition for the magnitude of the voltage value, the constraint condition for the subchannel used for transmission, the range condition for the input impedance connected to the RF chain, By applying the constraint on the rank of the matrix representing the pattern, it is possible to solve a complex problem such as a PAPR problem occurring in OFDM signal transmission, an oscillation problem due to a negative resistance value, and an impedance matching problem.

FIGS. 6 to 8 are diagrams for explaining the performance of a transmitter to which the multiple OFDM symbol transmission method proposed in the present invention is applied.

6 is a diagram for explaining an impedance distribution when an initial beam matrix is used. That is, FIG. 6 shows a required impedance distribution during a sample interval for arbitrary 10 OFDM symbols when an optimal variable value is not applied through the calculation module. At this time, it can be confirmed that the impedance value (resistance value) is distributed to the negative value, which means that the negative resistance value is required.

FIG. 7 is a required impedance distribution when a variable calculated based on the negative resistance limit is applied according to a range condition (impedance load chip constraints) for a resistance value and a reactance value in the calculation module proposed in the present invention. That is, in order to confirm the performance improvement when the optimal variable value is applied according to the present invention, it is necessary to confirm that the resistance component of the negative tone is not required.

That is, as shown in FIG. 7, it can be seen that the impedances excluding the negative resistance component are distributed (the impedance is distributed in the positive region). In other words, the ESPAR transmitter proposed in the present invention can transmit an independent OFDM symbol without distortion by excluding the negative resistance component by applying the optimum parameter calculated according to the constraint condition.

FIG. 8 is a view for explaining a comparison of the performance of the OFDM symbol transmission method proposed in the present invention.

Referring to FIG. 8, the gain of the ESPAR antenna transmitter having a single RF chain designed according to a resistance condition for determining an impedance value and a range condition for a reactance value achieves a gain higher than a multiplexing gain of a conventional multi-antenna system . Also, it can be seen that the slope of a single RF chain antenna transmitter rate achieves a multiplexing gain of 4. In addition, the loss of the full-RF chain transmitter (about 10 bps / Hz) loss may be compensated by applying restrictions based on channel information other than negative resistance exclusion and restrictions on correlation between beams.

In the beam space MIMO system proposed in the present invention, a method of transmitting independent multiple OFDM symbols through an ESPAR antenna transmitter, an ESPAR antenna transmitter in a beam-space MIMO environment is executed by a computer such as a program module executed by a computer But may also be embodied in the form of a recording medium including possible instructions. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, the computer-readable medium can include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Communication media typically includes any information delivery media, including computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transport mechanism. While the methods and systems of the present invention have been described in connection with specific embodiments, some or all of those elements or operations may be implemented using a computer system having a general purpose hardware architecture.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form. It is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. .

100: ESPAR Antenna Transmitter
120: active antenna
121, 122: parasitic antenna
130: Load resistance
131, 132: Load Impedance
140: Impedance matching unit
150: RF chain
160: Beam pattern calculation module

Claims (7)

A method for transmitting independent multiple OFDM symbols via an ESPAR antenna transmitter in a beam-space MIMO system,
A first current value calculated by mapping a matrix representing a beam pattern of the beam-space MIMO system for the multiple OFDM symbols under a plurality of constraint conditions, and a second current value, which is implemented through the ESPAR antenna transmitter, Calculating a variable for minimizing the difference between the second current values applied to the plurality of parasitic antennas disposed around the first parasitic antenna; And
And transmitting the multiple OFDM symbols by applying the calculated parameters to the ESPAR antenna transmitter,
Wherein the variable includes a matrix representing the beam pattern, a voltage value applied to the active antenna through an RF chain connected to the active antenna, and an impedance value coupled to the parasitic antenna. The method according to claim 1,
Wherein the step of calculating the variable when the parasitic antenna is 2 is calculated according to the following equation.

Where x is the impedance value of the first parasitic antenna, x2 is the impedance value of the second parasitic antenna, s is the OFDM symbol, Z is the impedance of the active antenna, Lt; / RTI > is a matrix representing mutual coupling between parasitic antennas) The method according to claim 1,
The step of calculating the variable
Wherein the voltage value is calculated using an initial matrix representing an arbitrary beam pattern under a constraint condition of at least one of a resistance condition for determining the impedance value, a range condition for a reactance value, and a range condition for a magnitude of the voltage value, A first calculation step of calculating an impedance value;
At least one constraint among a constraint on a subchannel used in transmission of the multiple OFDM symbols, a range condition on an input impedance connected to the RF chain, and a constraint on a rank of a matrix representing the beam pattern, A second calculation step of calculating a matrix indicating the beam pattern by using the value calculated through the first calculation step under the condition;
Performing the first calculation step again using a matrix calculated through the second calculation step instead of the initial matrix; And
Performing the second calculation step again using the value calculated through the re-performed first calculation step, and repeating the first calculation step using the matrix calculated through the re-performed second calculation step And a calculation step of calculating a transmission power of the OFDM symbol. The method of claim 3,
Wherein the iterative calculation is repeatedly performed until a variable for converging the difference between the first current value and the second current value is calculated. The method of claim 3,
Wherein if the number of parasitic antennas is two, the first calculation step is calculated according to the following equation.

Where x is the impedance value of the first parasitic antenna, x2 is the impedance value of the second parasitic antenna, s is the OFDM symbol, Z is the impedance of the active antenna, Lt; / RTI > is a matrix representing mutual coupling between parasitic antennas) The method of claim 3,
And if the parasitic antenna is 2, the second calculation step is calculated according to the following equation.

Where x is the impedance value of the first parasitic antenna, x2 is the impedance value of the second parasitic antenna, s is the OFDM symbol, Z is the impedance of the active antenna, Lt; / RTI > is a matrix representing mutual coupling between parasitic antennas) In an ESPAR antenna transmitter in a beam-space MIMO environment,
Active antenna;
A plurality of parasitic antennas disposed around the active antenna;
An impedance matching unit for performing impedance matching on a resistance value connected to the active antenna and an impedance value connected to the parasitic antenna; And
And an RF chain connected to the active antenna to apply a voltage value to the active antenna,
Wherein the matrix representing the beam pattern of the beam-space MIMO system, the voltage value, and the impedance value are generated by mapping a matrix representing the beam pattern for independent multiple OFDM symbols under a plurality of constraint conditions to a first current Value and a second current value that is implemented through the ESPAR antenna transmitter and applied to the active antenna and the parasitic antenna, respectively, is minimized.

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