KR101221751B1 - Apparatus and method for transmitting/receiving data in orthogonal frequency division multiple access system - Google Patents

Abstract

The present invention provides a transmission apparatus for transmitting packet data in a forward link of an orthogonal frequency division multiple access system, comprising: a slot determiner for checking whether a slot to be transmitted currently includes a preamble for channel estimation, and a pilot tone or data in the slot; A pilot tone inserter for inserting a tone, and when the slot determiner determines that the current transmission slot includes the preamble, the pilot tone inserter nulls a resource corresponding to a position of a predetermined pilot tone in the slot. A pilot tone controller, and a transmitter for transmitting the slot.

Pilot tone, data tone, OFDM, slot, preamble

Description

APPARATUS AND METHOD FOR TRANSMITTING / RECEIVING DATA IN ORTHOGONAL FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM}

1 illustrates a prior art preamble slot structure of a forward link in a typical frequency orthogonal multiplex (OFDM) system, FIG.

2 is a diagram illustrating a proposed preamble slot structure of a forward link in a frequency orthogonal multiplex (OFDM) system according to a first embodiment of the present invention;

3 is a diagram illustrating a proposed preamble slot structure of a forward link in a frequency orthogonal multiplex (OFDM) system according to a second embodiment of the present invention;

4 is a diagram illustrating a structure of a transmitting apparatus in a frequency orthogonal multiplexing (OFDM) system according to the first and second embodiments of the present invention;

5 is a flowchart illustrating a transmission process according to whether a transmission device is a preamble slot in a forward link of a frequency orthogonal multiplexing (OFDM) system according to the first and second embodiments of the present invention;

FIG. 6 is a diagram illustrating a structure of a receiving apparatus in a frequency orthogonal multiplexing (OFDM) system according to first and second embodiments of the present invention; FIG.

FIG. 7 is a flowchart illustrating a receiving process according to whether a receiving device is a preamble slot in a forward link of a frequency orthogonal multiplexing (OFDM) system according to the first and second embodiments of the present invention.

The present invention relates to an apparatus and method for transmitting and receiving data in a wireless communication system, and more particularly, to an apparatus and method for transmitting and receiving data in an orthogonal frequency division multiplexing (OFDM) system.

In general, a wireless communication system is a system developed for a case in which a fixed wired network cannot be connected to a terminal and used. Representative systems of such a wireless communication system include a mobile communication system, a wireless LAN, Wibro, a mobile ad hoc, and the like.

 Unlike general wireless communication, mobile communication assumes mobility of a user. The ultimate goal of mobile communication is to exchange information media at any time, anywhere, and anywhere using terminals such as mobile phones and pagers.

With the rapid development of the communication technology, the mobile communication system is providing a high speed data service capable of transmitting a large amount of digital data such as an e-mail or a still image as well as a video using a mobile terminal as well as a general voice call service. Is coming.

Representative examples of mobile communication systems that provide high speed data services are as follows. An orthogonal frequency division multiplexing (OFDM) transmission scheme is one of wireless communication systems employing a multicarrier transmission scheme. The OFDM transmission method converts symbol strings that are serially input in parallel, modulates each of them through a plurality of subcarriers having mutual orthogonality, and transmits them. The VLSI technology has been introduced since the early 1990s. As development progressed, it began to attract attention.

The OFDM transmission scheme modulates data using a plurality of subcarriers, and each subcarrier maintains orthogonality to each other so that frequency-selective multipath fading channel is compared with a conventional single carrier modulation scheme. It has a strong characteristic on frequency selective multipath fading channel and is suitable for high speed packet data service such as broadcasting service.

In FIG. 1, a slot structure of a forward link of a typical OFDM system will be briefly described. In a typical OFDM system such as that shown in FIG. 1, the subcarrier 102 allocated to the pilot signal and the data subcarrier 106 assigned to the data signal are scattered and transmitted in every slot. In the OFDM system, slots may be classified into slots including a preamble 100 and slots not including a preamble. In the conventional OFDM system, the pilot tone 102 is inserted and transmitted in the slot including the preamble, and the receiver performs channel estimation based on the pilot tone 102. However, in the case of the slot 104 including the preamble 100, since the preamble itself provides sufficient information for channel estimation, it is not efficient to insert the pilot tone 102 in the slot including the preamble. .

The present invention provides a transmission apparatus and method for nulling a pilot tone or inserting a data tone in a slot into which a preamble is inserted in order to efficiently use frequency resources in an OFDM system.
An apparatus according to an embodiment of the present invention is a transmitting apparatus for transmitting packet data in a forward link of an orthogonal frequency division multiple access system, comprising: a slot determiner for checking whether a slot to be transmitted currently includes a preamble for channel estimation; A pilot tone inserter for inserting a pilot tone or data tone into the slot, and if the slot to be transmitted currently includes the preamble as a result of the check by the slot determiner, the pilot tone inserter determines the position of a predetermined pilot tone in the slot And a pilot tone controller for controlling to null the corresponding resource, and a transmitter for transmitting the slot.

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According to an embodiment of the present invention, a method for transmitting packet data by a transmitting device in a forward link of an orthogonal frequency division multiple access system includes: checking whether a slot to be transmitted currently includes a preamble for channel estimation; And when the current transmission slot includes the preamble, nulling a resource corresponding to a location of a predetermined pilot tone in the slot and transmitting the slot.
According to another aspect of the present invention, an apparatus for receiving packet data in a forward link of an orthogonal frequency division multiple access system, the apparatus comprising: a receiver for receiving physical layer packet data and a slot of the received signal is a preamble And a preamble extractor for detecting the preamble if the slot includes the preamble, and a channel estimator for performing channel estimation using the preamble detected by the preamble extractor. Resource corresponding to the position of the predetermined pilot tone in the slot is characterized in that nulling.
According to another exemplary embodiment of the present invention, there is provided a method of receiving packet data by a receiving device in a forward link of an orthogonal frequency division multiple access system, the method comprising: receiving physical layer packet data and a slot of the received signal Checking whether the slot includes the preamble, if the slot includes the preamble, detecting the preamble, and performing channel estimation using the detected preamble; The resource corresponding to the location of the predetermined pilot tone in is nulled.

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Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. And in describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

2 is a diagram illustrating a slot structure in which a preamble is included in a data transmission interval in a forward link of a frequency orthogonal multiplexing system according to a first embodiment of the present invention.

In the case of the first slot 200, which is a slot including the preamble 100, it can be seen that the pilot tone 202 is not included. Accordingly, the reception apparatus according to the first embodiment of the present invention detects a preamble and uses the detected preamble to use channel estimation for demodulating the data subcarriers 204 of the corresponding slot 200.

Accordingly, the transmitting apparatus according to the first embodiment of the present invention does not insert a pilot tone (pilot subcarrier 202) in the slot 200 including the preamble, and instead replaces the data tone (data) at the pilot tone insertion position. Filling subcarrier 204 allows more data to be sent to that slot. Common Control Channel (CCCH) information may be included for 3-4 OFDM symbols after the first 2 OFDM symbol intervals in which the preamble is inserted. The CCCH is a common control channel and contains control information that is broadcast to all users. CCCH can also be included in the second embodiment.

3 is a diagram illustrating a slot structure in which a preamble is inserted into a data transmission interval in a forward link of a frequency orthogonal multiplexing system according to a second embodiment of the present invention.

As described above, in the case of the slot into which the preamble is inserted, the receiver detects the preamble without transmitting the pilot tone 302 as in the other slots, and then demodulates the data subcarrier 304 of the slot using the detected preamble. Channel estimation can be performed. In the transmitting apparatus according to the second exemplary embodiment of the present invention, an overhead of performing transmission / reception in an OFDM system can be reduced by leaving the original pilot tone insertion position in another empty space 306.

4 is a diagram illustrating a structure of a transmitter 400 in a frequency quadrature multiplexing system according to the first and second embodiments of the present invention.

The transmitter 400 in FIG. 4 includes a channel encoder 401 for channel encoding packet data received from a physical layer (not shown), a channel interleaver 402 for interleaving the encoded packet data, and interleaving. A modulator 403 for modulating the packet data, a boundary tone inserter 404 for inserting a boundary tone for reducing the influence of the out-of-band signal from interference, and a pilot tone for inserting a pilot tone for channel estimation in the terminal Inserter 405.

In addition, the transmitter 400 includes a QPSK spreader 406, an IFFT processor 407 for converting a signal in a time domain into a signal in a frequency domain, and a CP (Cyclic Prefix) in front of OFDM data to prevent signal interference. CP inserter 408 for inserting the (), and a transmission device 409 and a pilot tone controller 410 for transmitting a radio signal processed as described above. The diffuser 406 may use, for example, a quadrature phase shift keying (QPSK) diffuser.

In addition, in the present invention, the transmitting device 400 is a pilot tone controller 410 for controlling the pilot tone inserter 405 by using the information on the slot determiner 411 and the slot determiner to determine the slot to include the preamble. It consists of. That is, in the present invention, the slot determiner 411 informs the pilot tone controller 410 whether the preamble is included in the current slot, and the pilot tone controller 410 is based on the information transmitted by the slot determiner 411. Accordingly, the operation according to the embodiment of the present invention is performed. According to the first embodiment of the present invention, the pilot tone controller 410 controls the pilot tone inserter 405 to insert and send data to the pilot tone position of the slot including the preamble. The pilot tone position is nulled and transmitted. If no preamble is included, the pilot tone controller 410 instructs the pilot tone inserter 405 to insert a pilot tone in the slot.

FIG. 5 is a flowchart illustrating a transmission process in a transmission apparatus 400 according to whether a preamble is included in a forward link of a frequency orthogonal multiplexing system according to the first and second embodiments of the present invention.

In operation 501, the transmitting apparatus 400 determines whether the current slot is a slot including a preamp. In operation 501, if the current slot is a slot that does not include a preamble, the transmitter 400 proceeds to step 502 and generates a data tone by encoding and modulating data to be transmitted to the receiver. In operation 503, the transmitter 400 inserts a guard tone into the generated data tone, and then inserts a pilot tone in operation 504.

In operation 505, the transmitting apparatus 400 applies QPSK spreading to the generated OFDM symbol. In operation 506, the transmitter 400 generates the OFDM signal 406 to which the CP is attached and transmits the generated OFDM signal.

In contrast, if the preamble is included in the current slot in step 501, the apparatus 400 proceeds to step 508 to generate a data tone by encoding and modulating data to be transmitted to the receiving device. In step 509, the transmitting device 400 inserts a guard tone into the generated data tone, and then inserts a data tone at the position where the pilot tone is inserted in step 510 or nulls the pilot of the corresponding slot. . In the OFDM symbol generated through step 510, the transmitting apparatus 400 performs QPSK spreading in step 511, generates an OFDM signal by attaching a CP to the QPSK spread symbol in step 512, and transmits it in step 513. do.

Hereinafter, the structure and operation of the receiving apparatus 600 according to the present invention will be described with reference to FIGS. 6 to 7.

6 is a block diagram illustrating a structure of a receiving device 600 in a forward link of a frequency quadrature division system according to an embodiment of the present invention.

In the receiving apparatus 600 of FIG. 6, the downconversion and analog / digital conversion block 601 converts a transmitted signal into a baseband, converts an analog signal into a digital signal, and then removes a CP remover ( 602). The CP remover 602 removes the CP contaminated due to propagation delay, multipath, and the like from the received signal. The FFT processor 603 converts an input time domain signal into a frequency domain signal and outputs the signal. The QPSK despreader 604 despreads the signal in the frequency domain and outputs the tones of each signal. This is a case where it is assumed that a signal is transmitted by QPSK spreading in the transmitting apparatus 400. Therefore, when the spreading scheme is different in the transmitting apparatus 400, a despreader corresponding to the spreading scheme is provided.

The QPSK despreader 604 transfers the tones of each despread signal to the preamble extractor 605. The preamble extractor 605 detects a preamble in the case of a slot including a preamble among the received OFDM slots and transmits the preamble information to the pilot tone selector 612 and the channel estimator 608.

The pilot tone selector 612 informs the tonal extractor 606 whether the preamble is included in the currently received slot, and the pilot tone extractor 606 preambles the current slot according to the information provided by the pilot tone selector 612. If is included, the channel estimator 608 instructs the preamble channel to estimate without performing pilot tone extraction. On the other hand, if the preamble is not included in the current slot, the pilot tone selector 612 controls the pilot tone extractor 606 to extract the pilot tone in the current slot. The pilot tone extracted by the pilot tone extractor 606 is input to the channel estimator 608 and used to estimate the channel.

The pilot tone extractor 606 performing the above-described process transmits the received signal to the data tone extractor 607. The data tone extractor 607 extracts the data tone from the received signal and sends it to the demodulator 609. Meanwhile, the channel estimator 608 estimates a channel from the transmitted pilot signal or preamble information, and the channel estimate is transmitted to the demodulator 609. The demodulator 609 demodulates the data tone using the channel estimate received from the channel estimator 608, and the demodulated signal is deinterleaved through the deinterleaver 610 and input to the decoder 611. The decoder 611 decodes the input signal and restores the transmitted signal.

7 is a flowchart illustrating operations of the reception device 600 according to the first and second embodiments of the present invention. First, the receiving apparatus 600 determines whether the signal received in step 701 is a slot including a preamble. If the current slot is a slot that does not include a preamble as a result of the check in step 701, the receiver 600 proceeds to step 702, extracts an OFDM symbol, and performs QPSK despreading in step 703. In operation 704, the receiver 600 estimates a channel using a pilot tone on the despread signal. After the channel estimation in step 704, the receiving device 600 performs data tone extraction and demodulation in step 705, and recovers the signal through decoding in step 706.

On the other hand, if the current slot is a slot including the preamble as a result of the check in step 701, the receiving device 600 proceeds to step 707, after QPSK despreading after OFDM symbol extraction, using the preamble in step 709. Make channel estimates. After the channel estimation in step 709, the receiving device 600 extracts and demodulates the dayton in steps 710 and 711 and recovers the signal through decoding.

In the above detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. For example, the arrangement of pilot tones described with reference to FIGS. 2 to 3 is one example, and various forms of arrangement may be possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention uses the preamble for channel estimation instead of using the pilot tone for channel estimation and transmits and receives a slot including the preamble in the forward link of the frequency-division multiplexing system. You can use resources efficiently by adding data.

Claims (12)

A transmitting apparatus for transmitting packet data in a forward link of an orthogonal frequency division multiple access system, A slot determiner for checking whether a slot to be transmitted currently includes a preamble for channel estimation; A pilot tone inserter for inserting a pilot tone or data tone into the slot; A pilot tone controller for controlling the pilot tone inserter to null a resource corresponding to a position of a predetermined pilot tone in the slot when the slot to be transmitted includes the preamble as a result of the check by the slot determiner; And a transmitter for transmitting the slot. A transmitting apparatus for transmitting packet data in a forward link of an orthogonal frequency division multiple access system, A slot determiner for checking whether a slot to be transmitted currently includes a preamble for channel estimation; A pilot tone inserter for inserting a pilot tone or data tone into the slot; A pilot tone controller configured to control the pilot tone inserter to insert a data tone at a predetermined pilot tone position in the slot when the slot to be transmitted includes the preamble as a result of the check by the slot determiner; And a transmitter for transmitting the slot. The method according to claim 1 or 2, When the slot determiner determines that the current transmission slot does not include the preamble, the pilot tone controller controls the pilot tone inserter to insert a pilot tone at a predetermined position in the slot. Transmitting device. A method for transmitting packet data by a transmitting device in a forward link of an orthogonal frequency division multiple access system, Determining whether a slot to be transmitted currently includes a preamble for channel estimation; And when the current transmission slot includes the preamble, nulling a resource corresponding to a location of a predetermined pilot tone in the slot, and transmitting the slot. . A method for transmitting packet data by a transmitting device in a forward link of an orthogonal frequency division multiple access system, Determining whether a slot to be transmitted currently includes a preamble for channel estimation; And if the current transmission slot includes the preamble, inserting a data tone at a predetermined pilot tone position in the slot and transmitting the slot. The method according to claim 4 or 5, And if the current transmission slot does not include the preamble, inserting a pilot tone at a predetermined position in the slot and transmitting the slot. A receiving apparatus for receiving packet data in a forward link of an orthogonal frequency division multiple access system, A receiver for receiving physical layer packet data; A preamble extractor for checking whether the slot of the received signal includes a preamble, and detecting the preamble if the slot includes the preamble; A channel estimator for performing channel estimation using the preamble detected by the preamble extractor, And a resource corresponding to a location of a predetermined pilot tone in the slot is nulled. A receiving apparatus for receiving packet data in a forward link of an orthogonal frequency division multiple access system, A receiver for receiving physical layer packet data; A preamble extractor for checking whether the slot of the received signal includes a preamble, and detecting the preamble if the slot includes the preamble as a result of the checking; A channel estimator for performing channel estimation using the preamble detected by the preamble extractor, And a data tone is inserted into a predetermined position of the pilot tone in the slot. The method according to claim 7 or 8, Further includes a pilot tone selector, The pilot tone selector controls the pilot tone extractor to detect a pilot tone from the slot if the slot does not include the preamble, and the channel estimator uses the pilot tone detected by the pilot tone extractor. Receiving apparatus characterized in that for performing channel estimation. A method for receiving packet data in a forward link of an orthogonal frequency division multiple access system by Receiving physical layer packet data; Checking whether the slot of the received signal includes a preamble; If the slot includes the preamble, detecting the preamble; Performing channel estimation using the detected preamble, And a resource corresponding to a location of a predetermined pilot tone in the slot is nulled. A method for receiving packet data in a forward link of an orthogonal frequency division multiple access system by Receiving physical layer packet data; Checking whether the slot of the received signal includes a preamble; If the slot includes the preamble, detecting the preamble; Performing channel estimation using the detected preamble, And a data tone is inserted into a position of a predetermined pilot tone in the slot. The method according to claim 10 or 11, wherein If the slot does not include the preamble, detecting a pilot tone from the slot; The method of claim 1, further comprising performing channel estimation using the detected pilot tone.

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