KR20150000820A - Apparatus and method for compressing/decompressing data - Google Patents

Abstract

A technique relating to an apparatus and a method for sampling data at a sampling rate or lower of the Nyquist sampling theory to compress data is disclosed. The data compression apparatus includes a domain conversion unit for performing domain conversion on input data, data for generating compressed data by down-sampling the domain-converted input data to a Nyquist Sampling Rate or less, And a compression section. Therefore, it is possible to compress the data at a high compression rate by transmitting the data at a rate lower than the Nyquist sampling rate, compressing the data and restoring it at the receiving side.

Description

[0001] APPARATUS AND METHOD FOR COMPRESSING / DECOMPRESSING DATA [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission interface for a wired / wireless network, and more particularly, to an apparatus and a method for data compression by sampling at a sampling rate lower than a Nyquist sampling theory.

The Industry Specification Group (ETSI) under the European Standardization Organization (ETSI) will be responsible for the development of next-generation mobile radio networks, such as Radio Equipment Control (REC) (Open Radio Equipment Interface) standard that defines the interface between radio equipment (RE). ORI is a standard for solving compatibility problems between devices based on the existing Common Public Radio Interface (CPRI) standard, and standardization of IQ data compression is underway.

Currently, telecommunication carriers and equipment manufacturers require more separated base stations for LTE-TDD and MHN (Mobile Hotspot Network) systems. In addition, since a bandwidth of several tens Gbps is required beyond the bandwidth of 9.8 Gbps, which is already provided through CPRI standardization, efforts are being made to reduce the construction and maintenance cost of the system through application of the compression technology.

Alcatel-Lucent (ALU) proposed a compression algorithm based on the CPRI, a transmission standard for separate base stations.

Referring to FIG. 1, the compression technique for the IQ data of the ALU will be described below. In step S110, the signal can be sampled and filtered. For example, a 10 MHz LTE signal can be sampled using a 15.36 MHz clock to match the CPRI standard (S111), and the frequency characteristics that the major data components are less distributed in the components above 10.24 MHz, A low pass filtering process is performed (S112).

The second step S120 may be referred to as a block scaling step. For example, in step S120, only 11 bits of 15-bit IQ data are taken as valid bits (S121), and the calculated scaling factor (S122, S123). In this case, it is possible to transmit EVM (Error Vector Magnitude) within 1% with only 3/4 of the total signal. Therefore, the ALU suggests a final compression ratio of 50% through the above two steps.

The ALU technology has an advantage in that the system configuration is easy, and delay time due to compression and restoration is limited, but there is a disadvantage in that the compression rate is limited.

On the other hand, IDT (Integrated Device Technology) (US Pat. No. 8,331,461, 2012.12, " Compression of Baseband Transceiver System Radio Units ") provides a device for compression technology usable in a mobile communication system.

According to the IDT patent, less than 20 bits of IQ data used in the LTE mobile communication system are transmitted by sending only less than half of the valid bits. Specifically, referring to the size and phase of each data, an entire 360-degree interval is divided into five intervals of 10 degrees, 60 degrees, 90 degrees, 120 degrees, and 180 degrees, It is possible to select the section having the smallest difference from the position of the data and to send only the function number and the difference information of the selected section. In this case, it is possible to restore the original signal even if all the data strings of the original signal are sent, and to achieve a compression rate of 50% or more even if less data strings are sent.

However, in order to increase the compression ratio, it is disadvantageous to suffer a loss of an allowable error value size.

An object of the present invention is to provide an apparatus for compressing data at an improved compression rate for a data transmission interface for a wire / wireless network.

Another object of the present invention is to provide an apparatus for restoring data compressed at an improved compression ratio for a data transmission interface for a wired / wireless network.

Another object of the present invention is to provide a network system for compressing data with an improved compression rate and restoring compressed data for a data transmission interface for a wire / wireless network.

According to an aspect of the present invention, there is provided a data compression apparatus including a domain conversion unit for performing a domain conversion on input data, a data conversion unit for converting domain-converted input data to a Nyquist Sampling Rate And a data compression unit for generating compressed data by down-sampling.

Here, the domain converter may perform domain conversion on input data using any one of Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT).

Here, the domain conversion unit may calculate a sparsity value of the domain-converted input data.

Here, the data compressing unit may downsample the domain-converted input data using any one of a low pass filter, a random sampling, and a nonlinear vector function.

Here, the data compression unit may process the domain-converted input data in a vector format.

Here, the data compression unit may generate compressed data by multiplying domain-converted input data by a downsampling vector capable of downsampling domain-converted input data to a Nyquist sampling rate or less.

According to another aspect of the present invention, there is provided a data decompression apparatus that receives compressed data generated by down-sampling a Nyquist sampling rate or less as an input signal, A channel equalizer for equalizing compressed data to compensate for channel distortion, a data restoring unit for generating domain-converted restored data by up-sampling the equalized compressed data, And a domain inversion unit for performing inverse domain transform of the domain to generate reconstruction data.

Here, the data decompression unit may generate the domain-converted restored data by calculating an up-sampling vector capable of up-sampling the equalized compressed data and multiplying the equalized compressed data.

Here, the upsampling vector may be computed based on an Ll minimization technique.

Here, the domain inversion unit may perform inverse domain conversion corresponding to the domain transformation performed based on any one of Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform .

According to another aspect of the present invention, there is provided a network system for performing domain conversion on input data and down-sampling domain-converted input data to a Nyquist Sampling Rate A transmission apparatus for generating and transmitting compressed data by down-sampling the received compressed data; an equalizer for receiving and compressing the compressed data from the transmission apparatus; up-sampling the equalized compressed data to generate domain-converted restored data; And a receiving device for performing inverse domain conversion of the domain-converted restored data to generate restored data.

The data compression apparatus and the data decompression apparatus according to the present invention as described above can sample the transmission data at a rate lower than the Nyquist sampling rate, compress the data, and restore it at the receiving end.

Further, there is an advantage that data can be compressed and transmitted at a high compression ratio.

In addition, various capex and operating expenses (OPEX) due to the additional investment in the network caused by the explosion of wireless traffic can be reduced.

1 is a flow chart illustrating the technique of Alcatel-Lucent (ALU) for compression on IQ data.
2 is a block diagram for explaining a data compression apparatus according to an embodiment of the present invention.
3 is a block diagram for explaining a data restoration apparatus according to an embodiment of the present invention.
4 is a conceptual diagram illustrating a network 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.

2 is a block diagram for explaining a data compression apparatus 100 according to an embodiment of the present invention.

Referring to FIG. 2, a data compression apparatus 100 according to an embodiment of the present invention includes a domain conversion unit 110 and a data compression unit 120. In addition, the data compression apparatus 100 may be provided in a transmission apparatus (stage) of the network system 300.

The domain conversion unit 110 may perform domain conversion on the received input data. Herein, the input data may be an original signal before data compression, and may denote all binary signals used in the wire / wireless network system 300. For example, in a mobile communication system based on an LTE signal, input data can be expressed as binary data about 15 bits in IQ data. Here, IQ data refers to data modulated in In-Phase and Quadrature (IQ).

In addition, the input data may refer to a whole transmission frame defined in various transmission fields, and may only mean a specific field value within a transmission frame.

In detail, the domain conversion unit 110 can perform domain conversion on input data using any one of Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform .

FFT is a technique for converting time domain data into frequency domain, and enables selection of a valid frequency component of data that can not be observed in the time domain.

DCT is a representation of a given data as a sum of several cosine functions with different frequencies. Since DCT has a 'energy concentration phenomenon' in which most of energy components of a multimedia signal are concentrated on a part of low frequency components, it can be widely used for lossy compression. For example, DCT is used in JPEG image compression, MPEG, and the like.

The DWT is similar to the FFT method, but it has the advantage that the conversion efficiency is high because it is less loss than the FFT because it transforms not only the frequency component of the signal but also the position component of the signal in the time domain.

Also, the domain conversion unit 110 may calculate a sparsity value of the domain-converted input data. Here, the spatiotemt value may represent the occupancy rate of the data showing a value close to 0 or 0 in the entire data, and can be calculated by the following equation (1).

The existing information / communication system has been developed based on the digital system designed based on the Sampling Theorem by Shannon and Nyquist. Generally, a digital system starts by converting an analog signal into a digital signal.

In other words, after converting an analog signal such as a photograph or voice into a digital signal, the signal can be represented by an integer system, not a real system, so that it can be stored or copied through a computer that calculates and memorizes by a binary method. It can be transmitted without error through the communication network.

Since the process of converting an analog signal to a digital signal is performed by a device called an analog-to-digital converter (ADC), the technology of the ADC is an indispensable element for implementing a digital system.

These ADC devices are based on the Nyquist-Shannon sampling theory. In an ADC device, the sampling rate is proportional to the amount of information that can be represented. More precisely, sampling at more than twice the highest frequency of the signal can restore the signal back to the analog signal precisely. This is the Nyquist-Shannon sampling theory, which until today has been used as a basic theory for building digital systems.

In comparison, the data compressing unit 120 according to the embodiment of the present invention may down-sample the domain-converted input data to a Nyquist Sampling Rate or less to generate compressed data have. Here, the Nyquist sampling rate may mean sampling at more than twice the highest frequency of the signal. Therefore, according to the embodiment of the present invention, compressed data can be generated by sampling at less than twice the maximum frequency of the signal.

In detail, the data compressing unit 120 may downsample the domain-converted input data using any one of a low pass filter, a random sampling, and a nonlinear vector function. have.

The data compression unit 120 may represent the domain-converted input data in a vector format and process it. That is, the data compressing unit 120 may generate the compressed data by multiplying the domain-converted input data by a downsampling vector capable of downsampling the domain-converted input data to a Nyquist sampling rate or less.

For example, assuming that the size of the domain-converted input data is represented by N and expressed in a vector format, the domain-converted input data can be expressed by 1xN. Also, a downsampling vector capable of downsampling domain-converted input data below the Nyquist sampling rate can be expressed as NxM. Here, M can always be smaller than N (M < N).

The data compression process performed by the data compression unit 120 may be expressed as Equation (2).

According to Equation (2), when vector multiplication is performed between the vector representation (1xN) of the domain-converted input data and the downsampling vector (NxM), compressed data of 1xM size can be generated.

The compression ratio according to Equation (2) can be expressed by the following Equation (3).

For example, if the vector representation (1xN) of the domain-transformed input data is 1x10 and the downsampling vector (NxM) is 10x5, the compressed data can be represented by 1x5, Can be 50%. On the basis of the LTE signal, for a 15-bit input data, the compression rate becomes 50% when the compressed data is 7.5 bits.

3 is a block diagram for explaining a data restoration apparatus according to an embodiment of the present invention.

Referring to FIG. 3, a data recovery apparatus 200 according to an embodiment of the present invention includes a channel equalizer 210, a data decompressor 220, and a domain inverting unit 230. In addition, the data restoration apparatus 200 may be provided in a receiving apparatus (stage) of the network system 300.

The channel equalizer 210 receives the compressed data generated by down-sampling at a Nyquist Sampling Rate or less as an input signal and equalizes the compressed data to compensate for channel distortion. )can do. Here, the channel equalizer 210 may receive the compressed data through the wired / wireless medium 400.

The data restoring unit 220 may up-sample the equalized compressed data to generate domain-converted restored data.

In detail, the data restoring unit 220 may generate an upsampling vector capable of upsampling the equalized compressed data, multiply the equalized compressed data, and generate domain-converted restored data. Here, the upsampling vector can be calculated as an inverse matrix of the downsampling vector and can be calculated based on the L1 minimization technique.

The domain-transformed restoration data may have the same sparsity value as the sparsity value of the domain-transformed input data, which is data before the compression process is performed in the data compression apparatus 100 described above. Therefore, the data restoration apparatus 200 according to the embodiment of the present invention can restore data within an allowable error range.

The domain inversion unit 230 may perform inverse domain conversion of the domain-converted restored data to generate restored data. That is, the domain inversion unit 230 can perform the domain inversion corresponding to the domain conversion performed based on any one of Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform have.

The data compressing apparatus 100 and the data decompressing apparatus 200 according to the embodiment of the present invention are not limited to those applied to the environment of the separate wireless base station. For example, an embodiment of the present invention may be applied to a system applying time division, frequency division, wavelength division, code division, OFDMA, etc. as a multiplexing system of an access network, a backbone network and a network device, . In addition, embodiments of the present invention can be widely applied to various communication systems such as hardware, software, and the like, which require a function of compressing and restoring data to be transmitted through satellite communication, fixed wireless communication, wireless mobile communication, and a network.

4 is a conceptual diagram illustrating a network system according to an embodiment of the present invention.

Referring to FIG. 4, a network system 300 according to an embodiment of the present invention may include a transmitting apparatus and a receiving apparatus.

Here, the transmitting apparatus may be a concept equivalent to the data compressing apparatus 100 shown in FIG. 2 or a concept including the data compressing apparatus 100, and the receiving apparatus may be equivalent to the data restoring apparatus 200 shown in FIG. 3 Or a concept including the data restoration apparatus 200. [

Also, the transmitting device and the receiving device may be connected by various wired and wireless mediums (400). Wired media such as, for example, optical cables, coaxial cables, and the like, and wireless media such as radio waves, terrestrial microwaves, and the like.

The network system 300 according to the embodiment of the present invention uses a characteristic in which the majority of the data values are 0 and only a small number of data values are non-zero when the signal characteristic is converted into the frequency domain instead of the time domain , The original signal can be reconstructed with only a small number of linear measurements.

The transmitting apparatus performs domain conversion on the input data and generates and transmits compressed data by down-sampling the domain-converted input data to a Nyquist sampling rate or less.

The transmitting apparatus can down-sample the domain-converted input data using any one of a low pass filter, a random sampling, and a nonlinear vector function.

Specifically, the transmitting apparatus processes the domain-converted input data in a vector format and processes the downsampled vector capable of downsampling the domain-converted input data to a Nyquist sampling rate or less by multiplying the domain- Thus, compressed data can be generated. That is, the transmitting apparatus can perform a data compressing function performed by the data compressing apparatus 100 of FIG.

The receiving apparatus receives compressed data from the transmitting apparatus and equalizes the data, up-samples the equalized compressed data to generate domain-converted restored data, and performs domain inversion of the domain-converted restored data So that the restored data can be generated.

In particular, the reconstructed data may have characteristics within an Error Vector Magnitude (EVM). For example, if the loss is within 3% in the process of restoring the compressed data, the restored data can be recognized as being the same signal as the original signal (input data).

Specifically, the receiving apparatus can generate the domain-converted restored data by calculating the up-sampling vector capable of up-sampling the equalized compressed data and multiplying the equalized compressed data. Here, the upsampling vector can be calculated as an inverse matrix of the downsampling vector and can be calculated based on the L1 minimization technique. That is, the receiving apparatus can perform a data restoration function performed by the data restoring apparatus 200 of FIG.

The network system 300 according to the embodiment of the present invention can sample the transmission-side data at a rate lower than the Nyquist sampling rate, compress the data, and restore it at the receiving end. Therefore, the present invention can compress data with a high compression ratio as compared with the prior art. That is, compared with the prior art showing a compression ratio of about 50%, the present invention can compress data at a maximum compression rate such as 75%.

Also, according to the embodiment of the present invention, it is possible to reduce various types of facility investment costs (OPEX) and operating expenses (OPEX) due to the additional investment in the network caused by the explosion of wireless traffic.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

100: Data compression apparatus 110: Domain conversion unit
120: Data compression unit 200: Data restoration device
210: channel equalizer 220:
230: domain inverting unit 300: network system
400: Wired and wireless medium

Claims (15)

A data compression apparatus for a network interface,
A domain conversion unit for performing domain conversion on input data; And
And a data compression unit for generating compressed data by down-sampling the domain-converted input data to a Nyquist sampling rate or less. The method according to claim 1,
The domain converter may include:
Wherein the data conversion unit performs domain conversion on the input data using any one of Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT). The method according to claim 1,
The domain converter may include:
And calculates a sparsity value for the domain-converted input data. The method according to claim 1,
Wherein the data compression unit comprises:
Sampling the domain-converted input data using any one of a low pass filter, a random sampling, and a nonlinear vector function. The method according to claim 1,
Wherein the data compression unit comprises:
And transforming the domain-converted input data in a vector format. The method of claim 5,
Wherein the data compression unit comprises:
Wherein the compressed data is generated by multiplying the domain-converted input data by a downsampling vector capable of downsampling the domain-converted input data to a Nyquist sampling rate or less. A data restoration apparatus for a network interface,
A channel equalizer for receiving the compressed data generated by down-sampling at a Nyquist sampling rate or lower and receiving the input data as an input signal and equalizing the compressed data to compensate for channel distortion;
A data restoring unit for up-sampling the equalized compressed data to generate domain-converted restored data; And
And a domain inversion unit for performing domain inversion of the domain-converted restored data to generate restored data. The method of claim 7,
Wherein the data restoring unit comprises:
Wherein the up-sampled vector capable of up-sampling the equalized compressed data is calculated and multiplied by the equalized compressed data to generate the domain-converted restored data. The method of claim 8,
The up-
(Ll) minimization technique. &Lt; RTI ID = 0.0 &gt; 31. &lt; / RTI &gt; The method of claim 7,
Wherein the domain inversion unit comprises:
And performs inverse domain conversion corresponding to the domain transform performed based on any one of Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT). In data compression and decompression for a network interface,
A transmitter for performing domain conversion on input data and generating and transmitting compressed data by down-sampling the domain-converted input data to a Nyquist sampling rate or less; And
Receiving the compressed data from the transmitting apparatus and equalizing the compressed data, up-sampling the equalized compressed data to generate domain-converted restored data, and performing domain inversion on the domain-converted restored data And generates a restoration data by performing a restoration process. The method of claim 11,
The transmitting apparatus includes:
Sampling the domain-converted input data using any one of a low pass filter, a random sampling, and a nonlinear vector function. The method of claim 11,
The transmitting apparatus includes:
Converting the domain-converted input data into a vector format,
Wherein the compressed data is generated by multiplying the domain-converted input data by a downsampling vector capable of downsampling the domain-converted input data to a Nyquist sampling rate or less. The method of claim 11,
The receiving apparatus includes:
Sampling the equalized compressed data, and multiplying the equalized compressed data by the up-sampling vector to generate the domain-converted restored data. 15. The method of claim 14,
The up-
And is calculated based on an L1 minimization technique.

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