KR20070091855A - Apparatus and method for transmitting/receiving data in orthogonal frequency division multiple access system - Google Patents

Abstract

A method and an apparatus for transmitting/receiving data in an orthogonal frequency division multiple access system are provided to use effectively restricted resources by using a preamble instead of a pilot tone for a channel estimation in case that slot including the preamble is received/transmitted in a forward direction link. An apparatus for transmitting/receiving data in an orthogonal frequency division multiple access system includes a transmitter, a pilot inserting unit(405), a pilot tone controller(410), and a slot determining unit(411). The transmitter modulates physical layer data to be transmitted according to a predetermined transmission scheme to generate a wireless signal, and transmits the wireless signal through a wireless network. The pilot inserting unit inserts a pilot tone for channel estimation into a slot for transmitting the wireless signal. The pilot tone controller determines whether the pilot inserting unit inserted the pilot tone to the corresponding slot. The slot determining unit controls the pilot tone controller, such that the pilot tone is not inserted into the slot containing a 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. 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 communication technology, the mobile communication system has reached a stage of 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.

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.

A transmitter for transmitting packet data in a forward link of a frequency orthogonal division multiple access system according to the present invention includes a transmitter for modulating a physical layer packet data to be transmitted into a radio signal according to a predetermined transmission method and transmitting the radio signal to a radio network; A pilot inserter for inserting a pilot tone for channel estimation in a slot where a signal is transmitted, a pilot tone controller for controlling whether the pilot inserter inserts a pilot tone in a corresponding slot, and controlling an operation of the pilot tone controller In addition, the slot including the preamble includes a slot determiner for controlling to null the pilot tone without inserting a pilot tone.

A method for transmitting packet data by a transmitting apparatus on a forward link of a frequency orthogonal division system according to the present invention may include: checking whether a slot to be transmitted is a slot including a preamble for channel estimation; and as a result of the checking, the preamble is included. In this case, the process includes nulling and transmitting pilot tones in a corresponding slot according to a predetermined transmission scheme.

A receiving apparatus for receiving packet data in a forward link of an orthogonal frequency division multiple access system according to the present invention includes a receiver for receiving physical layer packet data transmitted through a radio signal according to a predetermined transmission scheme, and a slot of the received signal. Checking whether a preamble is included, and if the preamble is included in a slot currently received, a preamble extractor for transmitting the preamble information to a channel estimator and a pilot tone extractor, and performing channel estimation based on the preamble information. A channel tone estimator, a pilot tone selector for determining whether to process a pilot tone in a current slot based on the preamble information, and notifying a pilot tone extractor to control information to be used for channel estimation by the channel estimator; and control information of the pilot tone selector. The file in the currently received slot based on And a pilot tone extractor for determining whether or not to extract the tone.

According to the present invention, a method for receiving packet data in a forward link in a receiving apparatus of a frequency quadrature division system includes receiving physical layer packet data transmitted through a wireless signal according to a predetermined transmission method, and receiving a slot of the received signal. Checking whether a preamble is included; if the preamble is included in a slot currently received as a result of the check; performing channel estimation based on the preamble information; and using the channel estimation result, Restoring the data.

Hereinafter, exemplary 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 the time domain into a signal in the frequency domain, and a CP (Cyclic Prefix) at the front of the 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 the QPSK spreading 405 to the generated OFDM symbol. In operation 506, the transmitter 400 generates an OFDM signal 406 to which the CP is attached, and transmits the generated OFDM signal in operation 507. Done.

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 transmitter 400 inserts a guard tone to the generated data tone, and then inserts a data tone at the position where the pilot tone is inserted 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 receiving device 600 estimates the despread signal using a pilot tone. 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 transmitter for transmitting packet data in a forward link of a frequency orthogonal division multiple access system, A transmitter for modulating a physical layer packet data to be transmitted into a wireless signal according to a predetermined transmission method and transmitting the same to a wireless network; A pilot inserter for inserting a pilot tone for channel estimation into a slot in which the radio signal is transmitted; A pilot tone controller for controlling whether the pilot inserter inserts a pilot tone in a corresponding slot; Orthogonal frequency division multiple access system characterized in that it comprises a slot determiner to control the operation of the pilot tone controller and to control the nulling of the pilot tone without inserting a pilot tone in the slot including the preamble. Data transmission device. The method of claim 1, And the slot determiner controls to insert a data tone in the pilot tone position when the current slot is a slot including the specific preamble. The method of claim 1, And the information on the slot including the specific preamble is fixed information that the base station and the terminal know from each other. A method for transmitting packet data by a transmitting device on a forward link of a frequency orthogonal division system, Determining whether a slot to be transmitted currently is a slot including a preamble for channel estimation; And if the preamble is included as a result of the checking, nulling and transmitting a pilot tone in a corresponding slot according to a predetermined transmission method. The method of claim 4, wherein And transmitting the data tone by inserting the data tone in the pilot tone position of the corresponding slot according to a predetermined transmission scheme when the preamble is included as a result of the checking. The method of claim 4, wherein And if the preamble is not included as a result of the checking, inserting and transmitting a pilot tone in a corresponding slot, and transmitting the data in the orthogonal frequency division multiple access system. 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 transmitted through a wireless signal according to a predetermined transmission method; A preamble extractor for checking whether a preamble is included in the slot of the received signal and transmitting the preamble information to a channel estimator and a pilot tone extractor if the preamble is included in the currently received slot as a result of the check; A channel estimator for performing channel estimation based on the preamble information; A pilot tone selector for determining whether to process a pilot tone in a current slot based on the preamble information and informing a pilot tone extractor to control information to be used for channel estimation by the channel estimator; And a pilot tone extractor for determining whether to extract pilot tones of currently received slots based on the control information of the pilot tone selector. The method of claim 7, wherein The pilot tone selector controls the pilot tone extractor to extract a data tone inserted at a pilot tone position of the current slot when the preamble is included in the current slot, the data in the orthogonal frequency division multiple access system. Receiving device. The method of claim 7, wherein The pilot tone selector controls the pilot tone extractor not to perform pilot tone extraction because the pilot tone position of the current slot is nulled when the preamble is included in the current slot. Data receiving device in multiple access system. A method for receiving packet data on a forward link in a receiving apparatus of a frequency orthogonal division system, Receiving physical layer packet data transmitted through a wireless signal according to a predetermined transmission method; Checking whether a preamble is included in a slot of the received signal; Performing channel estimation based on the preamble information if the preamble is included in the slot currently received as a result of the check; And restoring data of the received signal using the channel estimation result. The method of claim 10, And extracting a data tone inserted at a pilot tone position of the current slot including the preamble. The method of claim 10, And not performing pilot tone extraction because the pilot tone of the current slot including the preamble is nulled.

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