KR101546189B1 - Transmitter, receiver using multiple antennas in cloud environment and transmitting, receiving method thereof - Google Patents

Abstract

Provided are a transmitter and a receiver having multiple antennas in a cloud environment and a transmitting and receiving method using the same. According to the present invention, the transmitter for transmitting a signal in the cloud environment where each base station uses a same frequency comprises: an encoder for generating a channel code bit by encoding an input signal; an interleaver for converting the encoded channel code bit into a certain sequence; a mapper for modulating the converted sequence into a transfer symbol; and a transmitting portion for multiplying a precoding vector to the modulated transfer symbol, and transmitting the same through a plurality of antennas.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter and receiver having multiple antennas in a cloud environment, and a transmission / reception method using the same. 2. Description of the Related Art [

The present invention relates to a transmitter / receiver and a transmission / reception method using multiple antennas in a cloud environment.

In recent years, due to the explosion of mobile communication traffic, a plan to convert a part of frequencies allocated to broadcasting worldwide for use in mobile communication, etc. is being planned. Terrestrial broadcasters use broadcasting frequencies I am concerned about the shortage.

In order to solve the frequency shortage and the use efficiency problems as described above, there is a need to develop a transmission technique that can increase the transmission capacity and enhance the reception performance while improving the frequency utilization efficiency.

With this technology, a terrestrial cloud transmission technique has been proposed which facilitates transmission and reception in the existing white space and facilitates frequency reuse and single frequency network (SFN) construction.

Cloud-based broadcasting, also called frequency-shared broadcasting, is required to be able to transmit and receive even in negative SNR (Signal to Noise Ratio) with strong characteristics of noise and interference signals. It is easy to construct a single frequency network, It should also be possible to transmit broadcast signals.

However, only the concept of frequency utilization and transmission technology is presented in such frequency sharing type broadcasting technology, and the technology suitable for actual broadcasting is in the state of research and development.

In addition, although a multi-antenna MIMO technique has been studied, conventional frequency-shared broadcasting has been constructed as a single-input single-output (SISO) -based scenario. Even in a negative SNR environment, Shared multi-antenna technology for transmitting contents of a mobile station has not yet been reported.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a frequency sharing type multiple antenna technique for transmitting a high capacity content even in a negative SNR environment.

According to an aspect of the present invention, there is provided an encoder comprising: an encoder for encoding an input signal according to an embodiment of the present invention to generate a channel code bit; A mapper for modulating the converted sequence into transmission symbols, and a transmitter for multiplying the modulated transmission symbols by a precoding vector and transmitting the multiplied transmission symbols through a plurality of antennas .

According to an aspect of the present invention, there is provided a receiver for receiving a signal in a cloud environment in which base stations use the same frequency, wherein the receiver is configured to receive an interference symbol from a signal received from the plurality of antennas, Equalization and unitary decoders for detecting a target symbol, determining an effective channel to which a noise magnitude weight for the received signal is to be applied, and determining an interleaved channel code bits A demapper for calculating a log-likelihood ratio (LLR), and an LDPC decoder for decoding the channel code bits using an LDPC code.

According to an aspect of the present invention, there is provided a method of transmitting a cloud signal using a same frequency by a transmitter in a transmitter according to an embodiment of the present invention includes transmitting a precoded signal through a Low-density parity- ) Code to generate a channel code bit, converting the encoded channel code bits into a specific sequence, modulating the converted sequence into a transmission symbol, And multiplying the transmitted transmission symbols by a unitary precoding vector and transmitting the multiplied transmission symbols through a plurality of antennas, wherein the number of unitary vectors is determined by the number of antennas.

According to an embodiment of the present invention, compared to the existing single frequency network, it can tolerate the same channel interference type and can synchronize with a strong signal path, so that the position of the co-channel transmitter and the output of the transmitter are correlated It is possible to utilize the maximum space utilization rate and to transmit various programs.

In addition, robustness against co-channel interference and the use of same channel transmission enable more channels to be used for broadcasting services, and can be utilized for interactive broadcasting services by utilizing various devices such as smart phones, tablet computers, and repeaters .

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a conceptual diagram of a service of a frequency-shared broadcast system according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of a transmitter that transmits signals using multiple antennas in a cloud environment in which base stations use the same frequency according to an embodiment of the present invention.
3 is a block diagram illustrating a configuration of a receiver that receives signals using multiple antennas in a cloud environment in which base stations use the same frequency according to an embodiment of the present invention.
4 is a flowchart illustrating an operation of a transmitter according to an exemplary embodiment of the present invention.
5 is a flowchart illustrating an operation of a receiver according to an embodiment of the present invention.
6A and 6B are graphs showing experimental results according to an embodiment of the present invention.
7A and 7B are graphs showing experimental results according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. 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.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" .

Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

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

1 is a conceptual diagram of a service of a frequency-shared broadcast system according to an embodiment of the present invention.

The frequency-shared broadcast system of the present invention can provide one or more layer data services or one or more streams. In FIG. 1 (a), the coverage of a frequency-shared broadcast service providing three streams A, B, Respectively.

Here, stream A may be provided as a fixed service, a mobile service, stream A + B, and stream A + B + C as a fixed service.

1 (b) is a diagram showing differences between a conventional single frequency network and a frequency-shared broadcast network.

In the conventional single frequency network, two transmitters can transmit the same signal (stream A) and superpose their coverage to transmit the same program. However, in case of transmission using the frequency-shared broadcasting system of the present invention, two transmitters Tx1, Tx2 may transmit different signals, that is, streams A1 and A2, respectively, to provide coverage for their respective programs, and that there is an area that can simultaneously receive streams A1 and A2.

1C is a diagram illustrating a case where two transmitters Tx1 and Tx2 transmit different programs in the frequency-shared broadcast system of the present invention.

Transmitter Tx1 may provide streams A1 and B1, and transmitter Tx2 may provide streams A2 and B2, respectively, where A1 and B1 and A2 and B2 are different streams.

As shown in FIG. 1 (c), it can be seen that each transmitter has its own program coverage, and there is an area where streams A1 and A2 can be simultaneously received.

Since the reception threshold values for the streams B1 and B2 are not negative dB values, the coverage for B1 and B2 is not overlapped.

Thus, different transmitters Tx1 and Tx2 require only a fixed RF frequency and do not need to be fixed to the phase of the signal, so the transmit SNR can be implemented with lower complexity and lower cost than the existing SNR.

2 is a block diagram illustrating a configuration of a transmitter that transmits signals using multiple antennas in a cloud environment in which base stations use the same frequency according to an embodiment of the present invention.

Conventional base stations use different frequencies, while base stations use the same frequency in the cloud environment of the present invention.

The transmitter 100 of the present invention that transmits signals using multiple antennas in such a cloud environment may include an encoder 110, an interleaver 120, a mapper 130, and a transmitter 140.

For reference, the transmitter 100 shown in FIG. 2 may be included in the frequency-shared broadcasting system shown in FIG.

The encoder 110 may encode a precoded signal to generate a channel code bit.

을 인코딩할 수 있으며, 정보 비트 당 코드 비트가 데이터율(R)의 역수(J=1/R)인 채널 코드 비트

를 순차적으로 생성할 수 있다.To this end, the encoder 110 uses an LDPC (Low-density parity-check) code to generate an information bit stream corresponding to stream A or B

And the code bit per information bit is the channel code bit (J = 1 / R), which is the reciprocal of the data rate R

Can be sequentially generated.

With such an LDPC, it is possible to transmit signals even in a low SNR (Signal to Noise) environment.

- 는 인코더(110)에 의해 인코딩된 채널 코드 비트(

)를 특정 순서열(sequence)(

)로 변환할 수 있다.Meanwhile, the interleaver 120 -

- is the channel code bit encoded by the encoder 110 (

) To a specific sequence (

). ≪ / RTI >

는 심볼 인덱스(symbol index)를 나타내고

은

이며,

는 복호 신호 성상도(Complex Signal Constellation)를 나타낸다.here,

Represents a symbol index,

silver

Lt;

Represents a complex signal constellation.

That is, the interleaver 120 may convert the encoded channel code bits into a specific sequence column in consideration of the symbol index and the decoding signal constellation.

는

매핑을 사용하여 심볼 a_k나 b_k로 변조될 수 있다.On the other hand, the mapper 130 can modulate the sequence transformed by the interleaver 120 into transmission symbols,

The

Mapping can be used to modulate the symbols a _k and b _k .

Meanwhile, the transmitter 140 may multiply the modulated transmission symbol by a unitary precoding vector, and transmit the precoded transmission vector to the receiver through a plurality of antennas.

, 크기가 M×1인 유니터리 프리코딩 벡터를 w_i라 하면, 크기가 M×1인 프리코딩된 송신 벡터 x_i는 아래의 <수학식 1>과 같이 나타낼 수 있다.Here,

, And a unitary precoding vector of size M × 1 is w _i , a precoded transmission vector x _i having a size of M × 1 can be expressed by Equation (1) below.

&Quot; (1) &quot;

It is assumed that the unitary precoding vector w _i is normalized in the above equation, and mathematically, the unitary vector w is a complex vector of n × 1 in size and satisfies the condition of Equation (2) below.

&Quot; (2) &quot;

는 Hermitian operator를 나타낸다. <수학식 2>에서 표현된 유니터리 벡터 w의 조건에 따라서 수신기는 송신 스트림이 곱해지고 결합하는 연산을 통해 원하지 않는 스트림을 효과적으로 제거할 수 있다.In the above formula

Represents the Hermitian operator. According to the condition of the unitary vector w expressed in Equation (2), the receiver can effectively remove the unwanted stream by multiplying and combining the transmission stream.

For reference, the maximum number of generation of unitary vectors can be determined by the number of transmission antennas. That is, the number of unitary vectors may be up to the number of physical antennas located at each transmitter.

Assuming that a transmission signal vector x of size M × 1 is broadcast through a wireless channel through a transmitter 140, a received vector of size N × 1 can be expressed as Equation (3) below.

&Quot; (3) &quot;

For reference, the size of the channel matrix H in the above equation is N × M.

3 is a block diagram illustrating a configuration of a receiver that receives signals using multiple antennas in a cloud environment in which base stations use the same frequency according to an embodiment of the present invention.

A receiver 200 for receiving signals using multiple antennas in a cloud environment in which base stations use the same frequency according to an embodiment of the present invention includes a ZF equalization and unitary decoder 210, a demapper 220, A de-interleaved decoder 230, an LDPC decoder 240 and a maximum likelihood detector 250. The de-interleaved decoder 230 may include a de-interleaved decoder 230, an LDPC decoder 240,

3 may be included in the frequency-shared broadcast system shown in FIG. 1, and in order to treat a signal received from the transmitter 100 as a MIMO equivalent model, the maximum over- (Guard Interval).

Meanwhile, the ZF equalization and unitary decoder 210 may apply the Zero-Forcing (ZF) technique to extract the desired symbol from the received signal without interference between streams.

를 송신 벡터를 나타내는 <수학식 4>

에 곱할 수 있으며, 그 결과는 아래의 <수학식 5>와 같다.In addition, the ZF equalization and unitary decoder 210 uses a different matrix, i.e., a filter matrix using the channel information of the interference symbol x ₂ , to detect only the target symbol x ₁ from the received signal

&Quot; (4) &quot;

And the result is as shown in Equation (5) below.

&Quot; (5) &quot;

The ZF equalization and unitary decoder 210 may then multiply the received signal by a Hermitian operation of the unitary vector to remove the interference between the precoded streams, Respectively.

&Quot; (6) &quot;

는 유니터리 벡터의 성질을 나타내는 <수학식 2>, 즉,

에 의해 완전히 제거될 수 있다.In the above equation,

(2) representing the nature of the unitary vector, that is,

Lt; / RTI &gt;

On the other hand, the demapper 220 may determine an effective channel to which the noise magnitude weight for the input is to be applied.

That is, when the effective SNR is not proper when the cyclic recovery is performed, the noise size input value can be determined at a low signal-to-interference noise ratio (SINR) to prevent performance degradation.

The ZF equalization and unitary decoder 210 is not related to the noise increase effect, but the noise term modified by the filter coefficient should be adjusted after the Soft-Bit information of the demapper 220 is generated.

In Equation (6), since the covariance matrix of the noise vector n can be influenced by the ZF filter matrix G ₂ , the demapper 220 calculates the weighted noise size using Equation (7) below. can do.

&Quot; (7) &quot;

The effective channel h after the equalization can be obtained using Equation (8) below.

&Quot; (8) &quot;

산출할 수 있다.The demapper 220 also determines the external LLRs for the interleaved code bits

Can be calculated.

Since the external information can be calculated using the max-log approximation in order to reduce the complexity, the bit matrix is given by the observation of the channel in Equation (8) and the Equation (6) .

&Quot; (9) &quot;

은 심볼

의

번째 비트 값을 나타낸다.For reference, r in Equation (9) is a symbol passing through the equalizer by Equation (6).

Symbol

of

Th bit value.

의

번째 비트의 a-Priori LLR값

을 산출할 수 있다.On the other hand, the de-interleaved decoder 230 is a de-

of

Lt; th &gt; bit of the a-Priori LLR value

Can be calculated.

는

이고 비트 0과 같은 심볼에 해당하는

번째 비트

의 부분 집합이다.From here

The

And corresponds to a symbol such as bit 0

Th bit

.

Meanwhile, the LDPC decoder (LDPC decoder) 240 can calculate the ratio of the log a posteriori probability (log-APP).

와 주어진 비트에 대해 Log-Likelihood Ratio(LLR)를 이용하여 산출하되, 그 값은 아래의 <수학식 10>을 이용할 수 있다.At this time, the LDPC decoder 240

And a Log-Likelihood Ratio (LLR) for a given bit, and the value can be calculated using Equation (10) below.

&Quot; (10) &quot;

는 밑이 e인 자연 로그를 나타낸다. 참고로, LDPC 디코더(LDPC Decoder)(240)는

를 산출하기 위해 sum-product algorithm(SPA), min-sum algorithm(MSA)과 같은 다양한 soft-output 채널 디코더 알고리즘들을 사용할 수 있다.In the above formula

Represents the natural logarithm of e. For reference, the LDPC decoder (LDPC decoder) 240

Output channel decoder algorithms such as the sum-product algorithm (SPA) and the min-sum algorithm (MSA) can be used to compute the output power.

의 결과 정보 비트들의 주어진 LLR값들을 이용하여 최대 우도(Maximum Likelihood;ML)를 검출할 수 있으며, 그 결정 기준은 아래의 <수학식 11>을 이용할 수 있다.Meanwhile, the maximum likelihood (ML) detector 250 detects the maximum likelihood (ML)

The maximum likelihood (ML) can be detected using the given LLR values of the result information bits of Eq. (11).

Equation (11)

는 패리티 체크 부분을 제거함으로써

로부터 추출된 정보에 대한 LLR이다. 결과적으로,

는 hard detecion 후에 나온 결과 값이다.In Equation (11)

By removing the parity check portion

Lt; RTI ID = 0.0 &gt; LLR &lt; / RTI &gt; As a result,

Is the result after hard detecion.

4 is a flowchart illustrating an operation of a transmitter according to an exemplary embodiment of the present invention.

First, the transmitter 100 encodes the precoded signal to generate a channel code bit (S401).

At this time, the transmitter 100 can encode the information bit stream using an LDPC having a channel code of a specific data rate, and the code bits per information bit can sequentially generate channel code bits which are reciprocals of a specific data rate .

After S401, the transmitter 100 converts the encoded channel code bits into a specific sequence (S402).

After S402, the transmitter 100 modulates the converted sequence into transmission symbols (S403).

At this time, the transmitter 100 may modulate the sequence transformed in S402 into a transmission symbol in consideration of the symbol index and the decoding signal constellation.

After S403, the transmitter 100 multiplies the transmission symbols modulated in S403 by a unitary precoding vector, and transmits the result through a plurality of antennas (S404).

5 is a flowchart illustrating an operation of a receiver according to an embodiment of the present invention.

First, the receiver 200 removes the interference symbols from the signals received from the plurality of antennas and detects a target symbol (S501).

At this time, the receiver 200 multiplies the received signal by Hermit's computation of the unitary vector, and can remove the interference symbol.

After step S501, the receiver 200 determines an effective channel to which the noise magnitude weight for the received signal is to be applied, and calculates a log-likelihood ratio (LLR) for the interleaved channel code bits (S502).

After step S502, the receiver 200 refers to the reliability value of the channel code bits calculated in step S502, and decodes the channel code bit of the effective channel using the LDPC code to restore the signal (step S503).

At this time, the receiver 200 may use various soft-output channel decoder algorithms such as a sum-product algorithm (SPA) and a min-sum algorithm (MSA).

For reference, the receiver 200 calculates the maximum likelihood of the LLR values of the decoded result information bits in step S503, and may reflect the maximum likelihood of the LLR values in the signal restoration.

6A and 6B are graphs showing experimental results according to an embodiment of the present invention.

The graphs of FIGS. 6A and 6B show performance evaluations of the conventional frequency-shared SISO (hereinafter referred to as 'Profile-I') and the frequency-shared MIMO technology of the present invention (hereinafter referred to as 'Profile-II' Results.

For reference, it is assumed that each transmitter in Profile-I has one transmit antenna, and each transmitter in Profile-II has two transmit antennas. In addition, the receiver has two receive antennas and assumes perfect time synchronization and perfect channel estimation.

In the transmitter, an uncorrelated Rayleigh fading environment is assumed, a constellation Gray Mapping is used, and a signal transmitted by the transmitter is set according to a defined operation mode of DVB-T2.

로 환경이 제일 안 좋은 경우를 가정한 것이다.In addition, an LDPC parity check matrix with a block size of 64,800 is used, the maximum number of iterations in the LDPC decoding is set to 50, and the imbalance of the transmission period power is set to 0 dB,

And it is assumed that the environment is the worst.

We also simulated the combination of 4- / 16- / 64- / 256-QAM as defined in the DVB-T2 standard and code rates of 1/3 and 5/6.

6A and 6B show the coded bit error rate (BER) according to the SINR and SNR. The code rates are 1/3 and 5/6, respectively, and the coded BER performance after the LDPC decoding is respectively shown.

For reference, the SINR can be defined as Equation (12) below.

&Quot; (12) &quot;

은 파워 비균형 함수에 의한 간섭의 파워이며

은 잡음의 파워를 나타낸다.In Equation (12) above,

Is the power of the interference due to the power unbalance function

Represents the power of noise.

As shown in FIG. 6A, the frequency-shared technologies of Profile-I and Profile-II can be seen to work well in negative SINR, and the performance is also the same.

That is, the performance difference between the Profile-I and the Profile-II is not significant from the SINR point of view. Referring to FIG. 6A, it can be seen that the difference is less than 2 dB when the code rate is 1/3.

However, in FIG. 6B, when the code rate is 5/6, Profile-I does not operate at high SNR, but Profile-II works well with performance difference within 0.25dB.

4-QAM with a code rate of 1/3 has better performance than Profile-I with the same transmission parameters up to 1.43 dB and 16-QAM with a code rate of 1/3 has a code rate of 1/3 It exhibits better performance than 4-QAM because the orthogonality of spatial resources can eliminate interference.

7A and 7B are graphs showing experimental results according to another embodiment of the present invention.

FIGS. 7A and 7B show coded BER performance after LDPC decoding in code raterk 1/3 and 5/6.

In order to more clearly visualize the difference in performance, the x-axis is re-measured with respect to the SNR according to the definition of Equation (13) below.

&Quot; (13) &quot;

In the above equations, the interference power is not included in the calculation in order to clearly measure noise-robust performance.

Referring to FIG. 7A, it can be seen that the conventional 4-QAM having a code rate of 1/3 from the viewpoint of SNR operates at 9.4-dB.

6A and 6B, it can be seen that the performance difference between Profile-I and Profile-II is not large, indicating that the interference between Profile-I and Profile-II is completely removed by orthogonality of spatial polygons.

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.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: Transmitter
110: encoder, 120: interleaver
130: mapper, 140: transmitter
200: receiver
210: ZF equalization and unitary decoder, 220: demapper
230: deinterleaved decoder, 240: LDPC decoder
250: maximum likelihood detector

Claims (12)

delete delete delete delete delete delete In a receiver in which a base station receives a signal in a cloud environment using the same frequency,
An equalization and unitary decoder for removing an interference symbol from a signal received from a plurality of antennas and detecting a target symbol;
A demapper for determining an effective channel to which a noise magnitude weight for the received signal is to be applied, and calculating a log-likelihood ratio (LLR) for the interleaved channel code bits;
An LDPC decoder for decoding the channel code bits using an LDPC code,
, &Lt; / RTI &
The demapper includes:
Wherein the noise size weight is determined at a low Signal-to-Interference Noise Ratio (SINR) when the signal to noise ratio (SNR) is inadequate at the time of performing the cyclic recovery.
8. The method of claim 7,
The equalization and unitary decoder comprises:
Wherein the interference symbol is multiplied by a Hermitian operation of a unitary vector to remove the interference symbol.
delete 8. The method of claim 7,
The LDPC decoder,
Wherein the decoding is performed using a soft-output channel decoding algorithm including a Sum-Product Algorithm (SPA) and a Min-Sum Algorithm (MSA).
8. The method of claim 7,
A maximum likelihood detector for detecting a maximum likelihood of the reliability value of the decoded channel code bits,
Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &gt;
delete

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