RU2363109C1 - Method of adaptive data multiplexing in ofdma system and transmitting/receiving device thereof - Google Patents

Abstract

FIELD: communication devices. ^ SUBSTANCE: invention relates to a communication system which uses multi-accessing. Provided is a method and device for transmitting/receiving in a wireless communication system based on orthogonal frequency-division multiplexing (OFDM), in which the data transmitting device adaptively selects a multiplexing scheme in accordance with code rate of the transmission packet or actual signal-to-noise ratio (SNR) of the wireless channel for the corresponding terminal during transmission of the data packet channel. The adaptive multiplexing scheme has the same concept as the scheme for adaptive unitary precoding. Multiplexing with unitary precoding involves orthogonal frequency and code division multiplexing (OFCDM), fast Fourier transformation with spectrum broadening OFDM (FFT-S-OFDM), fast frequency hopping OFDM (FFH-OFDM) etc. The method and device adaptively select the multiplexing scheme and transmit/receive data using the selected multiplexing scheme, thereby increasing efficiency of receiving data packets. ^ EFFECT: increased efficiency of receiving data packets at high code rate. ^ 14 cl, 14 dwg

Description

FIELD OF THE INVENTION

The present invention generally relates to a communication system using a multiple access scheme. More specifically, the present invention relates to a transmission / reception method and apparatus for selecting an optimal multiplexing scheme according to the conditions of data transmission and data transmission using the selected multiplexing scheme, in order to increase the reception efficiency of data transmitted in a system that transmits / receives data using a multiple access scheme based on orthogonal frequency division multiplexing (OFDM).

State of the art

Recently, in the field of technology of wireless communication systems, active research is conducted on orthogonal frequency division multiplexing (OFDM), which is useful for high-speed data transmission over wireless channels. OFDM, a multi-carrier data transmission scheme, is a type of multi-carrier modulation that converts a stream of consecutive input symbols into parallel symbols and modulates each of the symbols with a plurality of orthogonal subcarriers, such as subcarrier channels, prior to transmission.

Figure 1 is a block diagram illustrating the structure of a transmitter for a common OFDM system.

As shown in FIG. 1, a transmitter for a common OFDM system includes a channel encoder 101, a modulator 102, a serial to parallel (S / P) converter 103, an inverse fast Fourier transform (IFFT) block 104, a converter 105 of parallel form to serial (P / S) and cyclic prefix insertion (CP) block 106.

The channel encoder 101 performs channel coding of the input information bit stream. Typically, a convolutional encoder, turbo encoder, or diluted parity check (LDPC) encoder is used as the channel encoder 101.

Modulator 102 performs quadrature (quadruple) phase shift keying (QPSK), octal phase shift keying (PSK), or hexadecimal quadrature amplitude modulation (QAM) to output the channel encoder 101. Although not illustrated in FIG. 1, it will be apparent to those skilled in the art that a speed matching unit for performing repetition and perforation functions can be added between elements 101 and 102.

The S / P converter 103 has the function of converting a signal output from the modulator 102 into a parallel signal. The IFFT block 104 performs IFFT calculation for outputting the S / P converter 103.

The P / S converter 105 converts the output of the IFFT block 104 back into a serial signal. The CP insertion unit 106 has the function of attaching a cyclic prefix (CP) to the output of the P / S converter 105.

There is a modified OFDM multiplexing scheme in which the transmitting device performs Hadamard transform on the modulation symbols in the frequency domain before transmission. This design is generally referred to as multi-carrier code domain multiplexing (MC-CDM) or orthogonal frequency domain code multiplexing (OFCDM).

FIG. 2 is a block diagram illustrating a structure of a common transmitter in unitary precoding in OFDM.

As shown in FIG. 2, a common unitary transmitter in OFDM with unitary precoding includes a channel encoder 201, a modulator 202, a unitary precoder 203, an S / P converter 204, an inverse fast Fourier transform (IFFT) block 205, P / S-converter 206 and CP insertion unit 207.

The channel encoder 201 performs channel coding of the input information bit stream. Typically, a convolutional encoder, turbo encoder, or LDPC encoder is used as the channel encoder 201.

Modulator 202 performs QPSK, 8PSK, or 16QAM to output channel encoder 201. Although not illustrated in FIG. 2, it should be apparent to those skilled in the art that a rate matching unit for performing repetition and perforation functions can be added between elements 201 and 202 .

Unitary precoder 203 is a standard unitary precoder, and various examples of unitary precodes are described below with reference to FIGS. 3A-3C.

S / P converter 204 has the function of converting the output of modulator 202 to a parallel signal. The IFFT unit 205 performs IFFT calculation for outputting the S / P converter 204.

The P / S converter 206 converts the output of the IFFT block 205 back into a serial signal. The CP insertion unit 207 has the function of attaching a cyclic prefix (CP) to the output of the P / S converter 206.

3A-3C are diagrams illustrating several examples of the unitary precoder of FIG. 2. 3A is a diagram illustrating a unitary precoder that uses the Hadamard transform.

As shown in FIG. 3A, the unitary precoder includes a symbol demultiplexer (DEMUX) 311 and a Walsh function superposition unit 312 and a Walsh adder 313.

A symbol demultiplexer 311 converts the serial signal output from the modulator 202 of FIG. 2 into a parallel signal. The Walsh function overlay unit 312 performs a Walsh overlay or spreading coding process with a spreading spectrum of modulation symbols outputted from the symbol demultiplexer 311 by a Walsh code with a predetermined length. The Walsh adder 313 performs the process of summing the conclusions (i.e., the outputs encoded by spreading the spectrum by each Walsh function) of the Walsh function superposition block 312.

FIG. 3B is a diagram illustrating a unitary precoder that uses Fast Fourier Transform (FFT).

As shown in FIG. 3B, the unitary precoder includes a symbol demultiplexer 321, an FFT block 322, and a P / S converter 323.

A symbol demultiplexer 321 converts the serial signal output from the modulator 202 of FIG. 2 into a parallel signal. The FFT block 322 performs FFT conversion to output the demultiplexer 321 characters. The P / S converter 323 converts the parallel signal output from the FFT block 322 into a serial signal.

3C is a diagram illustrating a unitary precoder that uses fast frequency hopping (FFH).

Referring to FIG. 3C, the unitary precoder includes a character demultiplexer 331, a linear FFH processor 332, and a P / S converter 333.

A symbol demultiplexer 331 converts the serial signal output from the modulator 202 of FIG. 2 into a parallel signal. The linear FFH processor 332 performs linear FFH conversion to output a demultiplexer of 331 characters. FFH is a technology for matching different subcarriers of each OFDM sample.

The P / S converter 333 converts the parallel signal output from the linear FFH processor 332 into a serial signal.

Of the above conventional unitary precoding OFDM multiplexing schemes, the Hadamard precoding OFDM scheme of FIG. 3A is referred to as orthogonal frequency and code division multiplexing (OFCDM) multiplexing scheme, and the FFT precoding OFDM of FIG. 3B is referred to as Spread Spectrum FFT-coding (FFT-S-OFDM) OFDM. In addition, the FFH precoding OFDM scheme of FIG. 3C is referred to as the Fast Frequency Hopping OFDM (FFH-OFDM) scheme.

FIG. 4 is a diagram for briefly explaining the concept of general FFH introduced in FIG. 3A.

As shown in FIG. 4, the FFH technique is described by comparing the existing frequency hopping technique with the FFH technique for a period of one OFDM symbol with an FFT size of M = 4.

4, reference 401 denotes a multi-carrier modulation device for implementing an existing frequency hop technique per symbol for a period of 4 OFDM samples. References 405-408 refer to multi-carrier FFH modulation devices.

In the existing frequency hopping technique shown on the left in FIG. 4, the input data is identical for a period of 4 OFDM samples, and the output signals are output one at a time each sample period. Since the current frequency hopping technique maps fixed subcarriers in the period of one OFDM symbol, the blocks denoted by reference numbers 401-404 are identical for period 4 of the OFDM samples.

However, in the FFH technique shown on the right in FIG. 4, the mapping between the subchannel data and the actual subcarriers is changed by switching M: M each sampling period. The subcarriers with which the first subchannel, indicated by reference number 405 is mapped, are mapped in the order [1 4 2 3]; subcarriers with which the second subchannel, indicated by reference number 406, is mapped in the order [4 3 1 2]; the subcarriers with which the third subchannel, indicated by reference number 407, is mapped in the order [2 1 3 4], and the subcarriers with which the fourth subchannel, indicated by the reference number 408, is mapped in the order [3 2 4 1]. This mapping pattern is called a hop pattern for each subchannel.

As described above, in comparison with unitary precoding OFDM technology, OFDM technology shows higher efficiency at a low code rate.

However, in comparison with OFDM technology, unitary precoding OFDM technology demonstrates higher efficiency at a very high code rate, such as a 4/5 code rate. Despite these characteristics, the standard mobile communication system disadvantageously uses one of the OFDM and OFDM technologies with unitary precoding for packet data transport channels.

Therefore, there is a need for an improved method for adaptively multiplexing data in an OFDMA system and a transmitter / receiver that utilizes unitary precoding OFDM and OFDM technologies.

Disclosure of invention

Exemplary embodiments of the present invention are directed to solving at least the above-described problems and / or disadvantages and providing at least the advantages described below. Accordingly, it is an object of exemplary embodiments of the present invention to provide a transmit / receive method and apparatus for adaptively using both, and not just one of the unitary precoding OFDM and OFDM technologies according to the situation, in order to increase the reception efficiency of packet data transmission / reception in an OFDM wireless communication system.

According to one aspect of exemplary embodiments of the present invention, there is provided a method for adaptively multiplexing data transmission in a base station for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station; the base station transmits packet data to the terminal, information required for scheduling is collected, scheduling is performed using the collected information, the code rate of the data to be transmitted to the selected terminal is compared with a predetermined threshold, the proper multiplexing scheme is selected according to the comparison result, and packet data is transmitted using the selected multiplexing scheme.

According to another aspect of exemplary embodiments of the present invention, there is provided a method for adaptively multiplexing data transmission in a base station for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station; the base station transmits packet data to the terminal, information required for scheduling is collected, scheduling is performed using the collected information, the actual signal-to-noise ratio (SNR) corresponding to the transmission packet of the selected terminal is obtained for orthogonal frequency division multiplexing (OFDM) with unitary precoding and OFDM, the actual SNR for OFDM with unitary precoding is compared with the actual SNR for OFDM, a multiplexing circuit suitable for brane terminal is selected according to the comparison result, and packet data is transmitted using the selected multiplexing scheme.

According to a further aspect of exemplary embodiments of the present invention, there is provided a method for receiving adaptively multiplexing data in a base station for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station; the base station transmits packet data to the terminal, a determination is made whether the packet data of the terminal is received, the multiplexing circuit used for the packet data of the terminal is found, the packet data is demultiplexed using the found multiplexing circuit.

According to another aspect of exemplary embodiments of the present invention, there is provided a base station apparatus for an orthogonal frequency division multiple access (OFDMA) system in which a terminal performs packet communication in the coverage area of a base station; the base station transmits packet data to the terminal by adaptive data multiplexing, the unitary conversion unit performs unitary conversion of the modulation symbols to be transmitted in the frequency domain, the switching unit switches to the unitary conversion unit, and the controller determines whether to switch the switching unit according to the scheme multiplexing.

According to another aspect of exemplary embodiments of the present invention, there is provided a terminal device for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of a base station; the base station transmits packet data to the terminal by adaptive data multiplexing, the inverse unitary transform unit performs the inverse unitary transformation of the received modulation symbols in the frequency domain, and the controller determines whether to activate the inverse unitary transform unit according to the multiplexing scheme.

According to another aspect of exemplary embodiments of the present invention, there is provided an orthogonal frequency division multiple access (OFDMA) system in which a terminal performs packet communication in the coverage area of a base station; the base station transmits packet data to the terminal by adaptive data multiplexing, collects the information required for scheduling, performs scheduling using the collected information, compares the code rate of the data to be transmitted to the selected terminal with a predetermined threshold, selects the appropriate multiplexing scheme according to the result comparing and transmitting packet data using the selected multiplexing scheme; the terminal determines whether the packet data is received, if the packet data is received, finds the multiplexing circuit used for its packet data, and demultiplexes the packet data using the found multiplexing circuit.

According to another aspect of exemplary embodiments of the present invention, there is provided an orthogonal frequency division multiple access (OFDMA) system in which a terminal performs packet communication in the coverage area of a base station; the base station transmits packet data to the terminal by adaptive data multiplexing, collects the information required for scheduling, performs scheduling using the collected information, obtains the actual signal-to-noise ratio (SNR) corresponding to the transmission packet of the selected terminal for multiplexing with orthogonal frequency division multiplexing (OFDM) with unitary precoding and OFDM compares the actual SNR for OFDM with unitary precoding with the actual SNR for OFDM, ybiraet multiplexing scheme appropriate for the selected terminal according to the comparison result, and transmits packet data using the selected multiplexing scheme; the terminal determines whether the packet data is received, if the packet data is received, finds the multiplexing circuit used for its packet data, and demultiplexes the packet data using the found multiplexing circuit.

Other objectives, advantages and pronounced features of the invention should become apparent to those skilled in the art from the following detailed description, which, when considered together with the accompanying drawings, discloses exemplary embodiments of the invention.

Brief Description of the Drawings

The above and other objectives, features and advantages of specific exemplary embodiments of the present invention should become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, of which:

figure 1 is a block diagram illustrating the structure of a transmitting device in a common OFDM system;

FIG. 2 is a block diagram illustrating a structure of a common transmitting device in OFDM with unitary precoding; FIG.

figa is a diagram illustrating a unitary precoder that uses the Hadamard transform;

figv is a diagram illustrating a unitary precoder that uses fast Fourier transform (FFT);

figs is a diagram illustrating a unitary pre-encoder that uses fast frequency hopping (FFH);

4 is a diagram for briefly explaining the concept of a common FFH introduced in FIG. 3A;

5 is a diagram illustrating the results of comparing performance between OFDM and OFCDM for code rate = 1/4 of a transport block;

6 is a diagram illustrating the results of comparing performance between OFDM and OFCDM for code rate = 1/2 of a transport block;

7 is a diagram illustrating the results of comparing performance between OFDM and OFCDM for code rate = 4/5 of a transport block;

8 and 9 are diagrams illustrating a method in which a transmitting device adaptively selects a multiplexing scheme based on a predetermined criterion each time it transmits a packet data channel, and transmits packets using a selected multiplexing scheme in an OFDM wireless communication system according to an exemplary embodiment of the present invention;

10 is a diagram illustrating a structure of a transmitter based on the adaptive multiplexing method of FIGS. 8 or 9 according to an exemplary embodiment of the present invention;

11 is a diagram illustrating a method in which a receiving device receives packets using the proposed adaptive multiplexing method according to an exemplary embodiment of the present invention; and

12 is a diagram illustrating a structure of a receiving device according to an exemplary embodiment of the present invention.

The implementation of the invention

Aspects indicated in the description, such as a detailed structure and elements, are provided in order to help in a comprehensive understanding of embodiments of the invention. Therefore, those skilled in the art should recognize that various changes and modifications to the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

In a broad sense, the concept of “Unitary Precoded OFDM” includes all of OFCDM, FFT-S-OFDM and FFH-OFDM. Although FIGS. 5-7 illustrate comparison data between OFDM and OFCDM, all of OFCDM, FFT-S-OFDM and FFH-OFDM have the same characteristics. Therefore, it can be considered that FIGS. 5-7 are simulation data between OFDM and unitary precoding OFDM.

The relative effectiveness of the two above technologies, i.e. Unitary precoding OFDM and OFDM is not a constant, but a variable according to several factors. Important factors from several factors may include the code rate of the data transport block and the frequency selectivity of the channel. Therefore, the following is a description with reference to FIGS. 5-7 of the results of comparing the efficiencies between OFDM and OFCDM in terms of code rate and channel frequency selectivity.

5 is a diagram illustrating the results of comparing the performance between OFDM and OFCDM (designated as MC-CDM in FIGS. 5-7) for code rate = 1/4 of a transport block. 5-7, EG denotes equal gain paths, and UEG denotes unequal gain paths. In the plots, the X axis represents the bit energy / total noise (Eb / Nt), and the Y axis represents the packet error rate (PER).

5, OFDM is superior in efficiency to OFCDM (MC-CDM) at code rate = 1/4 of a transport block. In addition, the level of the difference in efficiency varies according to variations in frequency selectivity, i.e. variations in the number of paths.

6 is a diagram illustrating the results of comparing performance between OFDM and OFCDM for code rate = 1/2 of a transport block.

6, OFDM is superior in performance to OFCDM (MC-CDM) at code rate = 1/2 of the transport block. In addition, the level of the difference in efficiency varies according to variations in frequency selectivity, i.e. variations in the number of paths.

7 is a diagram illustrating the results of comparing the performance between OFDM and OFCDM for code rate = 4/5 of a transport block.

7, OFDM is superior in OFCDM efficiency at code rate = 4/5 of the transport block. In addition, the level of the difference in efficiency varies according to variations in frequency selectivity, i.e. variations in the number of paths.

8 and 9 are diagrams illustrating a method in which a transmitting device adaptively selects a multiplexing scheme based on a predetermined criterion each time it transmits a packet data channel and transmits packets using a selected multiplexing scheme in an OFDM wireless communication system according to an exemplary an embodiment of the present invention.

In other words, FIGS. 8 and 9 are diagrams illustrating a method for transmitting direct data from a base station to a terminal according to an exemplary embodiment of the present invention. The direct data transmission method can be divided into the methods of FIGS. 8 and 9 according to criteria based on which the base station adaptively selects a multiplexing scheme. The method of FIG. 8 is described first below.

As shown in FIG. 8, in step 801, the packet transmitting device manager collects the information required for scheduling. The information required for scheduling, in General, may include the level of quality of service (QoS) for the traffic of each user, the current channel status of each user and the amount of current transmitted traffic for each user.

At 802, a packet transmitter manager performs scheduling after collecting the information required for scheduling. In the process of scheduling, the dispatcher determines the user packet data that he will transmit at the data rate at the appropriate time. With respect to the selected user, one or many users may be selected according to the state of the system. Determining the data rate means determining how much data should be transmitted over how long. In this process, the overall mobile communication system determines the modulation order (e.g., QPSK, 8PSK, 16QAM, etc.) and the code rate along with the data rate of each individual user.

After scheduling is determined, the multiplexing scheme that should be used to transmit packet data by the selected user is determined at steps 803-805.

The operations of steps 803-805 can be considered the essence of an exemplary embodiment of the present invention. At 803, the packet transmitter determines whether the code rate for packet data determined by the scheduling is greater or less than the predetermined threshold T_r. The reason for choosing a multiplexing scheme according to the code rate is because the efficiency of the unitary precoding OFDM and OFDM is sensitive to the code rate, as shown in the simulation results in FIGS. 5 and 7. Therefore, specific exemplary embodiments of the invention choose a threshold based multiplexing scheme code rate previously determined in the packet transmitting device.

If it is determined in step 803 that the code rate is higher than T_r, the packet transmitter determines OFDM as the multiplexing circuit at block 804. On the other hand, the packet transmitter determines the unitary precoding OFDM as the multiplexing circuit in block 805. Next, at step 806, the packet transmitter transmits the packet data according to the multiplexing scheme determined in steps 803-805.

FIG. 9 is a diagram illustrating a process for adaptively determining a multiplexing circuit using a different criterion than the criterion in FIG. 8, according to an exemplary embodiment of the present invention.

As shown in FIG. 9, in step 901, the packet transmitting device manager collects the information required for scheduling. The information required for scheduling can generally include a QoS level for each user’s traffic, the current channel status of each user, and the amount of current transmitted traffic for each user.

At 902, the packet transmitter manager performs scheduling after collecting the information required for scheduling. In the process of scheduling, the dispatcher determines the user packet data that he will transmit at the data rate at the appropriate time. With respect to the selected user, at least one of the users may be selected according to the state of the system. Determining the data rate means determining how much data should be transmitted over how long. In this process, the overall mobile communication system determines the modulation order (e.g., QPSK, 8PSK, 16QAM, etc.) and the code rate along with the data rate of each individual user.

After scheduling is determined, the multiplexing scheme that should be used to transmit packet data by the selected user is determined at steps 903-905.

The operations of steps 903-905 can be considered the essence of the present invention. Another criterion according to an exemplary embodiment of the present invention for adaptively determining a multiplexing scheme includes an actual signal-to-noise ratio (SNR). Those. the proposed method determines higher or lower OFDM than OFDM with unitary precoding in relation to the actual SNR for the current channel of the selected user and then selects a multiplexing scheme having a higher actual SNR.

The actual SNR for OFDM is denoted as SNReff_OFDM, and the actual SNR for OFDM with unitary precoding is denoted as SNReff_Unitary. In general, each user's wireless channel can be measured at each terminal so that the terminal knows SNReff_OFDM and SNReff_Unitary. Therefore, in order to enable the base station to know SNReff_OFDM and SNReff_Unitary, a possible method is provided in which the terminal sends both SNReff_OFDM and SNReff_Unitary to the base station. There is another possible way in which each terminal sends one of SNReff_OFDM and SNReff_Unitary to the base station along with information about the preferred multiplexing scheme.

Step 903 corresponds to a process in which the base station receives SNReff_OFDM and SNReff_Unitary for each terminal in the manner described above. The general method used to calculate SNReff_OFDM and SNReff_Unitary is given below as an example.

Equation (1) represents a general way to find SNReff_Unitary.

Equation (2) represents a general method for finding SNReff_OFDM. In equation (2), Ndata denotes the number of subcarriers used to transmit data in one OFDM symbol, SNR [k] denotes the SNR of each subcarrier, C (SNR [k]) denotes the bandwidth formula AWGN, and C-1 (Rsum) indicates the inverse function of C (SNR [k]).

(3)

(3)

Equation (3) represents another general way to find SNReff_OFDM. In equation (3), β is a constant, Nu is the total number of subcarriers, and γk is the SNR of subcarrier k. At step 904, the packet transmitter receives SNReff_OFDM and SNReff_Unitary and compares the SNReff_OFDM and SNReff_Unitary levels.

If it is determined in step 904 that SNReff_Unitary is higher than SNReff_OFDM, the packet transmitting device selects a unitary precoding OFDM as the multiplexing circuit in step 906. Otherwise, the packet transmitting device selects OFDM as the multiplexing circuit in step 905. Next, in step 907, the packet the transmitter transmits packet data according to the selected multiplexing scheme.

10 is a diagram illustrating a structure of a transmitter based on the adaptive multiplexing method of FIGS. 8 or 9 according to an exemplary embodiment of the present invention.

As shown in FIG. 10, a transmitter based on an adaptive multiplexing method includes a channel encoder 1001, a modulator 1002, a unitary conversion unit 1003, a switching unit 1004, a controller 1005, an S / P converter 1006, an IFFT unit 1007, P / S converter 1008 and CP insertion unit 1009.

Channel encoder 1001 performs channel coding of the input information bit stream. Typically, a convolutional encoder, turbo encoder, or LDPC encoder is used as the channel encoder 1001. Modulator 1002 performs QPSK, 8PSK, or 16QAM to output the channel encoder 1001. Although not illustrated in FIG. 10, it should be apparent to those skilled in the art that a speed matching unit for performing repetition and perforation functions may be added between elements 1001 and 1002.

The switching unit 1004, under the control of the controller 1005, performs switching to use one of the unitary precoding OFDM and OFDM as a multiplexing scheme. The controller 1005 controls the switching unit 1004 in the process of FIGS. 8 or 9. If the switching unit 1004 switches to the unitary conversion unit 1003 under the control of the controller 1005, the unitary precoder is activated. Those. data is transmitted by OFCDM, FFT-S-OFDM or FFH-OFDM described with reference to FIG. 2.

Unitary conversion unit 1003 is identical in structure and operation to any of the preliminary unitary encoders shown in FIGS. 3A-3C. If the switching unit 1004 switches to the S / P converter 1006 under the control of the controller 1005, the transmitting device does not activate the unitary conversion unit 1003.

The S / P converter 1006 has the function of converting a serial input signal to a parallel signal. The IFFT unit 1007 performs IFFT calculation for outputting the S / P converter 1006. The P / S converter 1008 converts the parallel output of the IFFT unit 1007 into a serial signal. The CP insertion unit 1009 has the function of attaching a CP to the output of the P / S converter 1008.

Although not illustrated in FIG. 10, the size of the matrix corresponding to the unitary transform unit 1003 is variable according to a given output size of the S / P converter 1006. In addition, since the size of the matrix is variable, a plurality of preliminary unitary encoders can be used. However, the transmitting device does not have to include a plurality of preliminary unitary encoders, but can perform iterative calculations with a single unitary preliminary encoder.

For example, if the output dimension of the S / P converter 1006 is 16 (which means that the number of subcarriers allocated to the transmitter is 16), this means that the size of the input to the S / P converter 1006 is 16. In this case, the matrix of the precoder size 16, two matrices of a preliminary encoder of size 8 (or two calculations with one matrix of a preliminary encoder of size 8), four matrices of a preliminary encoder of size 4 (or four calculations with one matrix of a preliminary encoder of size 4), or eight matrices of preliminary of a second encoder of size 2 (or eight computations with one precoding encoder matrix of size 2) can be used for unitary transform unit 1003.

Meanwhile, specific exemplary embodiments of the present invention need not be limited to direct transmission. The proposed method can also be applied to reverse gear, i.e. data transmission from the terminal to the base station. However, in most systems, since the subject of the scheduling operation is the base station, the terminal after directly scheduling in the manner of Figs. 8 or 9 receives scheduling information from the base station to the reverse transmission instead of using the adaptive multiplexing method. Further, the transmitting device selects a multiplexing scheme in a slightly different way according to the same criterion as described above at the permitted time when the transmitting device transmits data.

11 is a diagram illustrating a method in which a receiving device receives packets using the proposed adaptive multiplexing method according to an exemplary embodiment of the present invention.

Although the method of FIG. 11 is described with reference to direct packet transmission from a base station to a terminal, the method can also be applied to reverse packet transmission.

As shown in FIG. 11, in step 1101, the terminal constantly determines whether its packet has been received. The operation in step 1101 is identical to the corresponding operation in a standard packet data system. Those. in this process, the terminal constantly monitors the packet data control channel transmitted in the forward direction and determines if it contains any packet intended for the terminal.

If it is determined in step 1101 that the terminal packet has been received, the terminal performs the process of receiving the packet data channel in step 1102. At this point, the terminal should search for the multiplexing scheme (one of OFDM and unitary precoding OFDM) used for the packet transmission.

To perform the operation of step 1102, there are two possible methods. In a first possible method, the base station provides information indicating the used multiplexing scheme to the terminal via the packet data control channel.

In another possible method, the multiplexing schemes used, taking into account the specific code rate, are predefined between the transmitting and receiving devices. In an exemplary implementation, the receiving device, after it recognizes the code rate, can determine which multiplexing scheme the transmitter used to transmit the packet. For example, it is predefined that OFDM is used at a code rate less than or equal to a code rate of 1/2, and OFCDM is used at a code rate above a code rate of 1/2.

In step 1103, the terminal demodulates the packet data channel transmitted to it according to the multiplexing scheme detected in step 1102.

12 is a diagram illustrating a structure of a receiving device according to an exemplary embodiment of the present invention.

As shown in FIG. 12, the receiver includes a CP removal unit 1201, an S / P converter 1202, a Fast Fourier Transform (FFT) block 1203, a P / S converter 1204, a unitary inverse transform unit 1205, a controller 1206, a demodulator 1207 and channel encoder 1208.

A CP removal unit 1201 removes the CP from the received signal. An S / P converter 1202 converts the received signal with the remote CP to a parallel signal and outputs the parallel signal to the FFT block 1203. The P / S converter 1204 converts the output of the FFT block 1203 into a serial signal. Unit 1205 inverse unit conversion is a unit for performing inverse unitary conversion. Unit 1205 inverse unit conversion under the control of controller 1206 determines whether to activate or deactivate the inverse unitary converter. The output of the inverse unit transform unit 1205 is the input to the demodulator 1207, and the output of the demodulator 1207 is the input to the channel decoder 1208. The channel decoder 1208 obtains the final information using the channel decoding process.

Although not illustrated in FIG. 12, in a method similar to that of FIG. 10, the size of the matrix corresponding to the unitary inverse transform unit 1205 is variable according to a given output size of the S / P converter 1204, and since the size of the matrix is variable, there may be used a lot of preliminary unitary encoders. However, the receiving device does not have to include a plurality of unitary precoders, but can perform iterative calculations using a single unitary precoder. For example, if we assume that the output size of the P / S converter 1204 is 16, the matrix of the preliminary encoder is 16, two matrices of the preliminary encoder are 8 (or two calculations using one matrix of the preliminary encoder are 8), four matrices of the preliminary encoder are 4 ( or four calculations using a single matrix of a preliminary encoder of size 4), or eight matrices of a preliminary encoder of size 2 (or eight calculations with a single matrix of a preliminary encoder of size 2) can be used unit 1205 inverse unitary transformation.

The adaptive multiplexing method of the present invention can also be applied to a system using a hybrid automatic retransmission request (HARQ). In general, in a burst process in a system using HARQ, in many cases, the code rate is high for the initial transmission. Therefore, if the receiver uses OFDM for OFDM-based HARQs with unitary precoding during the initial transmission according to the proposed rule, it can effectively improve reception efficiency. In addition, the rule for determining multiplexing can be used by adaptively changing the multiplexing scheme in the initial transmission and retransmission according to the actual SNR instead of the code rate.

To simplify the HARQ operation, a possible method is provided in which, after the multiplexing scheme is determined based on the code rate or the actual SNR at the initial transmission, the same multiplexing scheme as determined at the initial transmission can be used for retransmission. It will be apparent to those skilled in the art that, as described above, the adaptive multiplexing method proposed in an exemplary embodiment of the present invention can be used for HARQ, and the multiplexing scheme can be determined even for other purposes using one of two selected criteria. , i.e. code rate and actual SNR, helping to increase the efficiency of receiving transmitted packets.

From the above description, it can be understood that in a communication system using an OFDM-based multiple access scheme, specific exemplary embodiments of the present invention can improve the reception efficiency of transmitted wireless packet data using an adaptive multiplexing method.

Although the present invention is shown and described with reference to its specific exemplary embodiments, specialists in the art should understand that various changes in form and content can be made without departing from the spirit and scope of the invention defined by the attached claims and its equivalents.

Claims (14)

1. A method for transmitting with adaptive multiplexing data in a base station for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station and the base station transmits packet data to the terminal, the method comprising the steps , where:
collect information required for scheduling;
perform scheduling using the collected information;
comparing the code rate of the data to be transmitted to the selected terminal with a threshold;
select the appropriate multiplexing scheme according to the comparison result; and
transmit packet data using the selected multiplexing scheme. 2. The adaptive data multiplexing transmission method according to claim 1, wherein the multiplexing scheme comprises selected orthogonal frequency division multiplexing (OFDM) multiplexing with unitary precoding if the data code rate is below a threshold and OFDM if the data code rate is above a threshold. 3. Adaptive multiplexing data transmission method in a base station for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station and the base station transmits packet data to the terminal, the method comprising the steps , where:
collect information required for scheduling;
perform scheduling using the collected information;
obtaining an actual signal-to-noise ratio (SNR) corresponding to a transmission packet of a selected terminal for orthogonal frequency division multiplexing (OFDM) with unitary precoding and OFDM;
comparing the actual SNR for OFDM with unitary precoding with the actual SNR for OFDM;
selecting a multiplexing scheme suitable for the selected terminal according to the comparison result; and
transmit packet data using the selected multiplexing scheme. 4. The adaptive data multiplexing transmission method of claim 3, wherein the multiplexing circuit comprises a selected OFDM with unitary precoding if the actual SNR for OFDM with unitary precoding is higher than the actual SNR for OFDM, and OFDM if the actual SNR for OFDM with unitary precoding below the actual SNR for OFDM. 5. A method for receiving adaptive multiplexing data in a terminal for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station and the base station transmits packet data to the terminal, the method comprising the steps of where:
determining whether terminal packet data has been received;
if the packet data of the terminal is received, find the multiplexing scheme used for the packet data of the terminal; and
demultiplex the packet data using the found multiplexing scheme. 6. The adaptive multiplexing data reception method according to claim 5, wherein the multiplexing circuit comprises at least one of a selected orthogonal frequency division multiplexing (OFDM) with unitary precoding and OFDM. 7. A base station device for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station and the base station transmits packet data to the terminal by adaptive data multiplexing, the device comprising:
unitary conversion unit for performing unitary conversion of modulation symbols to be transmitted in the frequency domain;
a switching unit for switching to a unitary conversion unit; and
a controller for determining whether to switch the switching unit according to the multiplexing scheme. 8. The base station device according to claim 7, in which the multiplexing circuit comprises at least one of a selected orthogonal frequency division multiplexing (OFDM) multiplexing with unitary precoding and OFDM. 9. A terminal device for an orthogonal frequency division multiple access (OFDMA) system in which the terminal performs packet communication in the coverage area of the base station and the base station transmits packet data to the terminal by adaptive data multiplexing, the device comprising:
an inverse unitary transform unit for performing inverse unitary transformations of received modulation symbols in the frequency domain; and
a controller for determining whether to activate the inverse unitary conversion unit according to the multiplexing scheme. 10. The terminal device according to claim 9, in which the multiplexing circuit comprises at least one of a selected orthogonal frequency division multiplexing (OFDM) with unitary precoding and OFDM. 11. Orthogonal frequency division multiple access (OFDMA) system, comprising:
a base station for collecting information required for scheduling, performing scheduling using the collected information, comparing the code rate of the data to be transmitted to the selected terminal with a threshold for selecting the appropriate multiplexing circuit according to the comparison result, and transmitting packet data using the selected multiplexing circuit; and
a terminal for performing packet communication in the coverage area of the base station, wherein the base station transmits packet data to the terminal by adaptive data multiplexing, determining whether packet data is received, determining the multiplexing schemes used for its packet data if packet data is received, and demultiplexing the packet data using the found multiplexing scheme. 12. The OFDMA system according to claim 11, in which the multiplexing circuit comprises at least one of a selected orthogonal frequency division multiplexing (OFDM) multiplexing with unitary precoding if the data code rate is below a threshold and OFDM if the code rate data above the threshold. 13. Orthogonal frequency division multiple access (OFDMA) system, comprising:
a base station for collecting information required for scheduling, performing scheduling using the collected information, obtaining the actual signal-to-noise ratio (SNR) corresponding to the transmission packet of the selected terminal for each of the orthogonal frequency division multiplexing (OFDM) with unitary precoding and OFDM, comparing the actual SNR for OFDM with unitary precoding with the actual SNR for OFDM, selecting a multiplexing scheme suitable for the selected terminal, with to pulley comparison result, and transmitting packet data using the selected multiplexing scheme; and
a terminal for performing packet communication in the coverage area of the base station, wherein the base station transmits packet data to the terminal by adaptively multiplexing the data, determining whether packet data is received, finding the multiplexing scheme used for its packet data if packet data is received, and demultiplexing the packet data using the found multiplexing scheme. 14. The OFDMA system of claim 13, wherein the multiplexing circuit comprises at least one of a selected OFDM with unitary precoding if the actual SNR for OFDM with unitary precoding is higher than the actual SNR for OFDM, and OFDM if the actual SNR for OFDM with unitary precoding below the actual SNR for OFDM.

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