KR101872110B1 - Method and apparatus for channel estimation in communication system - Google Patents
Method and apparatus for channel estimation in communication system Download PDFInfo
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- KR101872110B1 KR101872110B1 KR1020160127603A KR20160127603A KR101872110B1 KR 101872110 B1 KR101872110 B1 KR 101872110B1 KR 1020160127603 A KR1020160127603 A KR 1020160127603A KR 20160127603 A KR20160127603 A KR 20160127603A KR 101872110 B1 KR101872110 B1 KR 101872110B1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/022—Channel estimation of frequency response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0003—Two-dimensional division
- H04L5/0005—Time-frequency
- H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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Abstract
A method and apparatus for channel estimation in a communication system are disclosed. The wireless transmission apparatus can detect a channel environment, calculate a channel change amount based on the detected channel environment, and assign the pilot symbol to the frequency domain according to the channel change amount.
Description
The following description relates to a channel estimation technique using a pilot symbol among channel estimation methods of a communication system.
In wireless communication, performance degradation may occur due to multipath or fading due to movement of a terminal. Therefore, stable transmission and reception can be performed only when accurate channel estimation is performed. In the next generation mobile communication system, the channel variation due to the wide band and the high-speed movement is increased, and the importance of the channel estimation is further increased.
The transmitter according to the present invention provides an apparatus for reducing unnecessary waste of channel resources by adjusting the density of pilot symbols allocated to the frequency domain in response to channel changes and assigning pilot symbols only to necessary areas with high density.
In the present invention, the receiver needs a position of a pilot symbol allocated for channel estimation and a channel estimation using the pilot symbol. The receiver provides a device for reducing the number of samples in the time domain required for channel estimation by estimating the pilot symbol positions and channels through compression sensing utilizing an average of a plurality of samples in the time domain.
A wireless transmission apparatus using orthogonal frequency-division multiplexing (OFDM) according to an exemplary embodiment of the present invention includes a sensor for detecting a channel environment, and a controller for calculating a channel change amount based on the detected channel environment, And then allocating the pilot symbols to the frequency domain.
The processor may allocate more pilot symbols to the second frequency domain corresponding to the second channel change rate than the first channel change rate than the first frequency domain corresponding to the first channel change rate.
A channel estimation apparatus using an orthogonal frequency division multiplexing method according to an embodiment includes a receiver for receiving a plurality of OFDM symbols from a wireless transmission apparatus through a channel and a plurality of samples in a time domain included in each of the plurality of OFDM symbols Obtaining a pilot symbol vector obtained by channel-shifting a pilot symbol vector with a position of a pilot symbol while obtaining a symbol vector of a frequency domain through compression sensing with respect to the average of the plurality of samples, And estimating the channel based on the channel estimate.
The processor may average samples having the same time index included in each OFDM symbol among samples of the plurality of time domains included in each of the plurality of OFDM symbols.
The processor may use the compression sense to obtain a symbol vector of the frequency domain from an average of the samples having the same time index.
The symbol vector may be a sparse vector. An element corresponding to a data symbol occupying most of the elements of the symbol vector may be zero.
The processor may average samples with the same time index for some time index.
The processor may calculate the solution of the optimization problem based on an average of a plurality of samples in the time domain to obtain the symbol vector in the frequency domain.
The processor may obtain the symbol vector by calculating a vector having a minimum sum of absolute values of all elements of the average of the frequency-converted samples.
According to an embodiment of the present invention, there is provided a radio transmission method using an orthogonal frequency division multiplexing method, comprising: calculating a channel variation amount of an entire frequency domain based on a sensed channel environment; And allocating symbols.
The channel estimation method using the orthogonal frequency division multiplexing method according to an embodiment includes a step of averaging a plurality of samples of a time domain included in each of a plurality of OFDM symbols received through a channel from a wireless transmission apparatus for each OFDM symbol Obtaining a symbol vector of the frequency domain using compression sensing from an average of the plurality of samples, and estimating the channel based on the symbol vector.
According to an embodiment, it is possible to reduce waste of unnecessary resources by adjusting the density of pilot symbols allocated to the frequency domain corresponding to the change of the channel and allocating the pilot symbols to the required domain only at a high density.
According to one embodiment, by using the average of the samples in some time domain using the compression sense, it is possible to estimate the complexity of the implementation of the time domain sampling system and the calculation amount for the sample average by estimating the frequency domain pilot symbol positions and channels have.
FIG. 1 is a diagram illustrating a general configuration of a system for allocating pilot symbols and estimating channels according to an embodiment. Referring to FIG.
2 is a diagram illustrating an example of allocating pilot symbols according to a rate of change of a channel according to an embodiment.
3 is a diagram illustrating an example of an assigned pilot symbol according to one embodiment.
4A is a diagram showing a correspondence relationship of OFDM symbols with respect to frequency and time.
4B is a diagram illustrating a structure in which one OFDM symbol including a CP is analyzed in a time domain.
5 is a flowchart of a wireless transmission method according to an embodiment.
6 is a flowchart of a channel estimation method according to an embodiment.
Specific structural or functional descriptions of embodiments are set forth for illustration purposes only and may be embodied with various changes and modifications. Accordingly, the embodiments are not intended to be limited to the particular forms disclosed, and the scope of the present disclosure includes changes, equivalents, or alternatives included in the technical idea.
The terms first or second, etc. may be used to describe various elements, but such terms should be interpreted solely for the purpose of distinguishing one element from another. For example, 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.
It is to be understood that when an element is referred to as being "connected" to another element, it may be directly connected or connected to the other element, although other elements may be present in between.
The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises ", or" having ", and the like, are used to specify one or more of the described features, numbers, steps, operations, elements, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.
Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.
Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention with reference to the accompanying drawings, the same components are denoted by the same reference numerals regardless of the reference numerals, and a duplicate description thereof will be omitted.
FIG. 1 is a diagram illustrating a general configuration of a system for allocating pilot symbols and estimating channels according to an embodiment. Referring to FIG.
1 illustrates a situation where a
OFDM is a communication scheme that uses multi-carrier for high-speed data transmission. OFDM is a method of dividing a wideband signal into a plurality of orthogonal subcarriers and transmitting them in parallel. OFDM has the effect that the frequency selective fading channel characteristic of a wide band is changed to the frequency flat fading channel characteristic of a narrow band per subcarrier. In addition, the transmission symbols are modulated with a plurality of orthogonal subcarriers having different frequencies and transmitted at the same time, so that the transmission symbols are longer than the original data period, and the influence of ISI (Inter Symbol Interference) can be greatly reduced.
Thus, while OFDM has robust features for frequency selective attenuation, modulated symbols may experience attenuation of magnitude and phase due to channel traversal. Particularly, in the next generation wireless communication system, since the broadband band is used and the high-speed movement is frequent, the influence of the attenuation is large, and the change of the channel is more severe.
The
The
According to one embodiment, the
A pattern of pilot symbols of various patterns can be formed according to the change of the channel. In this case, since the amount of information on the pilot symbol pattern can be very large, the
2 is a diagram illustrating an example of allocating pilot symbols according to a rate of change of a channel according to an embodiment.
The
The
According to one embodiment, the
According to one embodiment, the
According to one embodiment, the
In the
3 is a diagram illustrating an example of an assigned pilot symbol according to one embodiment.
In FIG. 3, a channel environment of a frequency domain with a high pilot symbol density is high, and a channel environment of a frequency domain with a low pilot symbol density is small. As described above, by allocating the pilot symbols at a high density only to the required region, the
According to one embodiment, the
4A is a diagram showing a correspondence relationship of OFDM symbols with respect to frequency and time. 4B is a diagram illustrating a structure in which one OFDM symbol is analyzed in the time domain.
In the OFDM scheme, frequency utilization is relatively high because adjacent carriers maintain orthogonality with each other. Modulation and demodulation of OFDM symbols may be implemented with simple signal processing, e.g., IFFT and FFT.
In Fig. 4A, one OFDM symbol is composed of a plurality of subcarriers in relation to the frequency domain. Since each subcarrier is arranged at a minimum interval that can maintain orthogonality with each other, utilization of the available frequency band is high. Subcarriers may be referred to as subcarriers. The available frequency band may be referred to as the channel bandwidth.
In addition, the OFDM symbol has a time-dispersive characteristic. Each OFDM symbol is composed of samples of N time domains with respect to the time domain. The OFDM scheme uses a plurality of OFDM symbols in a time domain, and interference between OFDM symbols can be minimized by inserting guard intervals between OFDM symbols.
4B is a diagram showing an OFDM symbol in a time domain in more detail. For example, one OFDM symbol includes N time-domain samples and may include L CPs (cyclic prefix) to mitigate inter-symbol interference. Here, L CPs can constitute the guard interval of FIG. 4A. Samples of each time domain included in each OFDM symbol may correspond to a time index from 0 to N-1.
One of the samples in the time domain of FIG. 4B
And the frequency domain Can have a relationship as shown in Equation (1). Equation (1) Of an inverse discrete fourier transform (IDFT).
According to one embodiment, the
According to one embodiment, the
A sparse vector means a case where most of the elements constituting the vector are zero.
According to one embodiment, the
Equation (2) can be expressed in the form of a matrix as shown in Equation (3). Equation (3)
Wow And Using the expressed . For example, if a pilot symbol is assigned Carrier indexes of 0, 5, and 20 (20 < = N-1) The average value of the symbols located in the remaining subcarriers of the subcarrier becomes 0. The average value of the symbols located in a small number of subcarriers is not zero and the average value of the remaining subcarriers is zero. As such, the element corresponding to the data symbol among the elements of the symbol vector can be zero.The
Compression sensing is a theory that a sparse vector can be obtained with only a signal with a small amount of information. According to compression sensing,
In vector Is a rare vector, To save All elements of < RTI ID = 0.0 > If you only use Can be restored. Where P is the number of pilot symbols, N is the size of the whole vector, and N is a very small value compared to P.A vector composed of the mean of samples in the time domain
Vector that takes only m random elements from , And in the DFT matrix Made by taking m rows corresponding to the element of Matrix We can obtain the simultaneous equations as shown in Equation (4).
In Equation (4), since m is a very small value compared to N, the number of samples to be averaged in the time domain becomes small. Thus, the
According to one embodiment, the
Using equation (5), the
5 is a flowchart of a wireless transmission method according to an embodiment.
According to one embodiment, the
6 is a flowchart of a channel estimation method according to an embodiment.
According to one embodiment, the
The embodiments described above may be implemented in hardware components, software components, and / or a combination of hardware components and software components. For example, the devices, methods, and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, such as an array, a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.
The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.
The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. Program instructions to be recorded on a computer-readable medium may be those specially designed and constructed for an embodiment or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.
Although the embodiments have been described with reference to the drawings, various technical modifications and variations may be applied to those skilled in the art. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.
110: Transmitter
111: Processor
112: sensor
120: receiver
121: Receiver
122: Processor
Claims (5)
A receiver for receiving a plurality of OFDM symbols from a wireless transmission device via a channel; And
Averaging a plurality of samples of the time domain included in each of the plurality of OFDM symbols for each OFDM symbol and performing frequency conversion on the average of the plurality of samples to obtain a symbol vector of the frequency domain, A channel estimation method using a compression sensing technique,
Lt; / RTI >
Wherein the processor averages samples having the same time index included in each OFDM symbol among samples of the plurality of time domains included in each of the plurality of OFDM symbols,
Wherein the symbol vector is a scalar vector.
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