Method, apparatus, and system for transmitting and receiving information of an uncoded channel in an orthogonal frequency division multiplexing system

(54) Title: METHOD, APPLIANCE AND SYSTEM FOR TRANSMISSION Ε RECEPTION OF INFORMATION FROM AN UNCODED CHANNEL INTO AN ORTHOGONAL FREQUENCY DIVISION MULTIPLEXATION SYSTEM (30) Unionist Priority: 05/04/2005 kr 10-2005- 0037777 (73) Holder (s): Samsung Electronics co., Ltd.

(72) Inventor (s): Dong-Hee Kim, hwan-joon kwon, ju-ho LEE, Jin-Kyu Han, Joon-Young Cho, Yun-Ok Cho (74) Attorney (s): ORLANDO DE SOUZA (86 ) International Request: pct KR2006001696 of 05/04/2006 (87) International Publication: W0 2006 / iis432de09 / u / 2006 (57) Summary: method, apparatus and system for TRANSMISSION Ε RECEPTION OF INFORMATION FROM A NON-ENCODED CHANNEL IN AN ORTHOGONAL FREQUENCY DIVISION MULTIPLEXATION SYSTEM. A method, an apparatus and a system for the efficient transmission and reception of channels are provided in a wireless communication system based on an Orthogonal Frequency Division Multiplexing (OFDM). A multiplexing scheme differs according to a channel, when a transmitter transmits a packet data channel, a common control channel and a control channel designated for a particular user. Uncoded 1-bit information is widely dispersed across frequency and time domains using multiplexing technology to maximize diversity gain on a channel for transmitting information of at least one bit to a particular user as a recognition channel (ACK). The transmitter converts a sequence obtained by multiplexing multiple bits to be transmitted to a plurality of users in parallel signals and widely disperses the parallel signals in the time and frequency domains. When 1-bit unencrypted information is transmitted, reception reliability is improved, because channel encoding and transmission are efficiently performed using a small amount of resources.

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METHOD, APPLIANCE AND SYSTEM FOR TRANSMISSION Ε RECEPTION OF INFORMATION FROM A CHANNEL UNCODED IN A SYSTEM

OF ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING

BACKGROUND OF THE INVENTION 5 Field of the Invention

The present invention generally relates to a method and apparatus for transmitting and receiving data in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM). More particularly, the present invention relates to a method and apparatus for efficiently transmitting and receiving channel data for which an encoding process is not required.

Description of the Related Art

Recently, a great deal of research is being conducted on an Orthogonal Frequency Division Multiplexing (OFDM) transmission method serving as a useful scheme for high-speed data transmission using a radio channel in a mobile communication system. The OFDM scheme is a type of Multiple Carrier Modulation (MCM) for converting an input symbol stream serially into parallel and then modulating and transmitting parallel signals through a plurality of orthogonal subcarriers, in other words, a plurality of subcarrier channels. 0 OFDM transmission scheme copies a second half part of an OFDM symbol, attaches the copied part as a cyclic prefix (CP) before the OFDM symbol, and transmits the OFDM symbol, thereby removing an inter-symbol interference (ISI) previous symbol. The scheme of

2/21 OFDM transmission, robust for a multi-path fading channel, is suitable for high-speed broadband communication.

FIG. 1 is a block diagram illustrating a conventional transmitter structure in a wireless communication system, based on OFDM.

With reference to FIG. 1, a channel encoder 101 receives a predetermined information bit stream and then performs a channel encoding process for the received information bit stream. Conventionally, channel encoder 101 can use a convolution encoder, a turbocoder, a Low Density Parity Check (LDPC) encoder, and so on. The information bit stream encoded from channel encoder 101 is input into a modulator 103. Modulator 103 modulates the information bit stream encoded in a predetermined modulation scheme, such as a Quadrature Phase Shift Switch ( QPSK), a Phase 8 Shift Switch (8PSK), a 16 Quadrature Amplitude Modulation (16QAM), and so on. It is obvious that a rate combiner (not shown) for performing puncturing and repetition functions and so on can be additionally inserted between the channel encoder

101 and modulator 103.

A Serial to Parallel Converter (SPC) converts a modulator 103 output signal into parallel signals and then introduces the parallel signals into a Fast Inverse Fourier Transform (IFFT) processor 107. The IFFT 107 processor transforms the signals parallels of

3/21 according to an IFFT. A Parallel to Serial Converter (PSC) 109 converts the transformed parallel signals into a serial signal. A CP 111 inserter inserts a CP to prevent interference in the serial signal (or symbol) and then extracts the symbol with the CP. A brake system stream into which the CP was introduced is transmitted to a wireless network via a Frequency processor

Radio (RF) 113 and an antenna 115.

When the conventional OFDM transmitter described above performs a transmission operation, a modified multiplexing scheme performs a Hadamard transform on the modulated symbols to be transmitted from the OFDM transmitter in a frequency domain, and transmits the transformed symbols without transmitting directly a symbol modulated through a subcarrier. This scheme is referred to as Multiple Carrier Code Division Multiplexing (MC-CDM) or Orthogonal Frequency Code Division Multiplexing (OFCDM). From this point on, MC-CDM and OFCDM are referred to as the OFCDM scheme.

FIG. 2 is a block diagram illustrating a structure of an OFCDM transmitter in the OFDM-based wireless communication system. The OFCDM transmitter of FIG. 2 is configured by adding a well-known Hadamard transform processor 210 to the OFDM transmitter of FIG. 1, so that a CDM transmission scheme is applied to the OFDM transmission scheme.

With reference to FIG. 2, a channel encoder 201 receives a predetermined bit stream of information and performs a conventional channel encoding process,

4/21 such as a convolution encoding, a turbocoding, a Low Density Parity Check (LDPC) encoding and so on. The information bit stream encoded from channel encoder 201 is introduced into a modulator 203. Modulator 203 modulates the information bit stream encoded in a predetermined modulation scheme. A demultiplexer (DEMUX) 205 of the Hadamard transform processor 210 demultiplexes the modulated signal (or the symbol stream) into N outputs. A plurality of covers with Walsh functions, in other words, Walsh covers 0 to N, 207 over the N output signals with predefined Walsh codes. An adder 209 computes a sum of the signals covered with the Walsh codes, and extracts the signal sum to one, SPC 211. An SPC 211 output is transmitted to a wireless network via an IFFT 213 processor, a PSC 215, a CP 217 inserter, a

RF 219 and an antenna 221.

In the two multiplexing transmission techniques mentioned above, in other words, the OFDM and OFCDM schemes, one scheme does not always outperform the other scheme. Relative performances of the OFDM and OFCDM schemes can differ according to many factors. The main factors capable of varying the performances of the OFDM and OFCDM schemes are the code rate of transmitted data, the channel frequency selectivity and so on. As described above, the simulation results of a performance comparison between the OFDM and OFCDM schemes according to the transmitted data code rate, the channel frequency selectivity and

5/21 and so on are illustrated in FIG. 3 to 5. In FIG. 3 to 5, the horizontal axis represents a signal-to-noise ratio (Eb / Nt) when transmitted data is received, the vertical axis represents a Packet Error Rate (PER), EG represents equal gain paths, and UEG represents paths unequal gains.

FIG. 3 to 5 illustrate results of a performance comparison between the OFDM and OFCDM schemes, for example, when the transmitted data code rates are and⁴/₅, respectively. It can be seen that the OFDM scheme outperforms an OFCDM (or MC-CDM) scheme, when the code rates of the transmitted data are low (1/4 and 1/2), as illustrated in FIG. 3 and 4. Furthermore, it can be seen that a performance differs according to the number of equal / unequal gain paths, even when the frequency selectivity is varied. As illustrated in FIG. 5, it can be seen that the OFCDM scheme outperforms the OFDM scheme, when the code rate of transmitted data is high (4/5).

Due to the fact that performance differs according to a code or coding rate of a channel transmitted in the OFDM-based wireless communication system, there is a need for a method, a device and a system for efficient data transmission, while considering this difference.

SUMMARY OF THE INVENTION

Therefore, it is an example objective of the present invention to provide a method, apparatus and system for the transmission and reception of unencrypted information in a Frequency Division Multiplexing system

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Orthogonal (OFDM) for transmitting varied control information using a radio channel.

It is another example objective of the present invention to provide a method, an apparatus and a system for the transmission and reception of 1-bit information in an Orthogonal Frequency Division Multiplexing (OFDM) system for the transmission of information from varied control using a radio channel.

It is another example objective of the present invention to provide a method, a device and a transmission / reception system that can improve a diversity gain when 1 bit information is transmitted to a plurality of users in a Division of Multiplexing system. Orthogonal Frequency (OFDM) for transmitting varied control information using a radio channel.

It is yet another example objective of the present invention to provide a method, an apparatus and a system for the transmission and reception of unencoded control information in an Orthogonal Frequency Division Multiplexing (OFDM) system in which an information of Varied control is transmitted using a radio channel and a multiplexing scheme differs according to a type of channel.

According to an example aspect of the present invention, a method is provided for transmitting information from an unencrypted channel from a base station in an Orthogonal Frequency Division Multiplexing (OFDM) system, comprising the steps of realization of a unitary transformation into information

7/21 of unencrypted channel, mapping of subcarriers in a pattern to increase the diversity gain of unencrypted channel information in which the unit transform was performed, and multiplexing and transmission of other channel information with non-channel information coded mapped to the subcarriers.

According to another example aspect of the present invention, an apparatus is provided for the transmission of an Orthogonal Frequency Division Multiplexing (OFDM) system, which comprises a unit transform processor for the realization of a unit transform in an information unencoded channel, a subcarrier mapper for mapping subcarriers in a pattern to increase the gain in diversity of the non-coded channel information in which the unit transform was

<td>performed, a</td><td>multiplexer for</td><td>multiplexing</td><td>and the</td>

<td>transmission of</td><td>another information</td><td>channel with</td><td>an</td>

<td>information</td><td>uncoded channel</td><td>mapped to</td><td>at</td>

<td>subcarriers,</td><td>and a controller for</td><td>Control of</td><td>an</td>

subcarrier mapper operation.

According to another example aspect of the present invention, a method is provided for receiving information from an unencrypted channel at a terminal of an Orthogonal Frequency Division Multiplexing (OFDM) system, which comprises the reception steps of the unencrypted channel information from a radio channel, and carrying out an inverse unit transform in the received unencrypted channel information.

According to another example aspect of the present invention, an apparatus is provided for receiving a

8/21 information of an unencrypted channel in a terminal of an Orthogonal Frequency Division Multiplexing (OFDM) system, which comprises a reception module for receiving unencrypted channel information from a radio channel, a reverse unit transform processor for performing an inverse unit transform on the received non-coded channel information, and a controller for controlling an operation of the reverse unit transform processor.

In accordance with yet another example aspect of the present invention, an Orthogonal Frequency Division Multiplexing (OFDM) system is provided for transmitting and receiving information from an unencrypted channel, which comprises a transmitter for carrying out of a unitary transform of unencoded channel information, mapping of subcarriers in a pattern to increase the diversity gain of the non-coded channel information in which the unit transform was performed, and multiplexing and transmission of another channel information with the non-coded information mapped to the subcarriers, and a receiver for demultiplexing the unencrypted channel information received from a radio channel to a designated receiving path, and the realization of an inverse unit transform in the non-coded channel information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objectives and aspects of the present invention will be more clearly understood from the following detailed description taken in conjunction with the associated drawings, in which:

9/21 to FIG. 1 is a block diagram illustrating a conventional transmitter structure in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM);

<td>FIG.</td><td> 2</td><td>ti Uni d J.ci.y xci-ulci.</td><td>of blocks that</td><td>illustrates</td><td>one</td>

<td>transmitter</td><td>in</td><td>Multiplexing</td><td>Division</td><td>Code</td><td>in</td>

<td>Frequency</td><td colspan="2">Orthogonal (OFCDM)</td><td>conventional in</td><td>system</td><td>in</td>

<td>Communication</td><td>without</td><td>wire based</td><td>an OFDM;</td><td></td><td></td>

FIG. 3 to 5 illustrate results of simulation of a performance comparison between OFDM and OFCDM schemes;

FIG. 6 illustrates results of simulation of reception reliability, when a 1-bit unencrypted information is transmitted to a particular user in the wireless communication system based on the OFDM OR OFCDM scheme;

FIG. 7 is a flow chart illustrating a method for transmitting uncoded information in an OFDM system according to an example embodiment of the present invention;

FIG. 8 is a block diagram illustrating a structure of an apparatus for transmitting uncoded information in an OFDM system according to an example embodiment of the present invention;

FIG. 9 is a block diagram illustrating a structure of an apparatus for transmitting uncoded information in an OFDM system according to an example embodiment of the present invention;

FIG. 10A and 10B illustrate an example of subcarriers mapped according to an example modality of

10/21 the present invention;

FIG. 11 is a block diagram illustrating a structure of an apparatus for receiving non-coded information in the OFDM system according to an example embodiment of the present invention;

FIG. 12 is a flowchart illustrating a method for receiving uncoded information according to an example embodiment of the present invention; and FIG. 13 is a flowchart illustrating a channel allocation process and a system parameter adjustment process, when unencoded information is transmitted in the OFDM system according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXAMPLE MODALITIES

The exemplary embodiments of the present invention will be described in detail here below, with reference to the associated drawings. In the following description, detailed descriptions of functions and configurations incorporated here that are well known to those skilled in the art are omitted, for clarity and conciseness.

Before the exemplary embodiments of the present invention are described, an exemplary concept of the present invention will be briefly described.

When different types of channels, for example, a packet data channel, a common control channel and a control channel designated for a particular user, are configured in a wireless communication system, reception performance can be degraded , according to a transmission scheme, if only one particular multiplexing scheme is used. This degradation of

11/21 reception performance can occur when information of at least one bit is transmitted in a channel for transmission of Acknowledgment / Non-Acknowledgment (ACK / NACK) information to a particular user and a channel for transmission of a bit of power control or when unencrypted information is transmitted. Conventionally, 1-bit control information is transmitted as unencrypted information.

That is, FIG. 6 illustrates results of simulation of reception reliability when an unencrypted 1-bit information is transmitted to a particular user in a wireless communication system using an Orthogonal Frequency Division Multiplexing (OFDM) or Multiplexing scheme. Orthogonal Frequency Code Division (OFCDM). In the simulation results of FIG. 3 to 5, it can be seen that the superiority of relative reception performance between the OFDM and OFCDM schemes differs according to a code rate. Furthermore, it can be seen that the performance of the OFCDM scheme is superior when a code rate of a transmission packet is high in a data channel, and the performance of the OFDM scheme is superior when a code rate of a packet transmission rate is low in the data channel. Furthermore, it can be seen that the reception performance of the OFCDM scheme is superior when an uncoded 1 bit information is transmitted at an uncoded Bit Error Rate (BER), as illustrated in FIG. 6.

The exemplary modalities of the present invention propose a technology for transmitting and receiving information by widely dispersing information from 1

12/21 bit to be transmitted to a plurality of users in frequency and time domains, using a unit transform technique, such as a Hadamard transform or a Fast Fourier Transform (FFT), so that a gain diversity can be maximized when 1-bit information and / or unencrypted information is transmitted to a particular user.

For convenience, an ACK channel corresponding to a 10 channel for transmitting the 1-bit non-coded information according to an example embodiment of the present invention will be described in detail. One of ordinary skill in the art will appreciate that the transmit / receive method and apparatus of the present invention described below can be applied to other channels for 1 bit transmission to a particular user, which are similar to the ACK channel or a channel uncoded (for example, a channel for transmitting a power control bit).

FIG. 7 is a flowchart illustrating a method for transmitting uncoded information in an OFDM system according to an example embodiment of the present invention.

Using the transmission method of an example embodiment of the present invention, a base station determines whether an associated channel is an encrypted channel or an unencrypted channel, when information from each channel is transmitted in step 701. If the associated channel is a unencrypted channel, such as an ACK channel as a result of the determination in step 701, the base station will perform a

13/21 unit transformation in the 1-bit information to be transmitted to a plurality of users, using a Hadamard or FFT transform technique in step 703. After the 1-bit information in which the unit transform was carried out is mapped to subcarriers, so that the maximum diversity gain can be obtained in step 705, they are multiplexed with another channel information and are dispersed in the time and frequency domains in step 707. On the other hand, if it is determined in step 701 that the associated channel is an encoded channel, information from the associated channel is transmitted in the OFDM scheme using the transmitter structure, as illustrated in FIG. 1. An information to be transmitted in the OFDM scheme can be information from a control channel carrying control information to be commonly transmitted to users or information from a data channel with characteristics different from those of the ACK channel.

FIG. 13 is a flowchart illustrating a channel allocation process and a system parameter adjustment process, when unencoded information is transmitted in the OFDM system according to an example embodiment of the present invention. As an example of the unencrypted information, an ACK / NACK bit will be described.

In step 1301 of FIG. 13, a base station controls a subcarrier mapper on a transmitter described below, so that an ACK channel is mapped to subcarriers in a transmission unit in the time and frequency domains. In step 1303, the base station regulates an ACK channel system parameter according to a type

14/21 of a used unit transform processor. For example, when a Hadamard transform processor is used as the unit transform processor, a dispersion factor (SF_ACKCH) is regulated as the system parameter. When an FFT processor is used, an FFT size is set as the system parameter. Subsequently, the base station allocates an ACK channel index for each terminal at a call set-up time in step 1305. At this point, when the Hadamard transform processor is used as the unit transform processor, a Walsh code index is allocated to each terminal. When an FFT processor is used as the unit transform processor, an FFT input position for each terminal is allocated.

Subsequently, the base station determines whether the number of terminals located in an associated region exceeds a system parameter value in step 1307. If the number of terminals exceeds the spread factor or FFT size, the base station will proceed to the step 1309 to additionally allocate an ACK channel. Here, additional ACK channel allocation is performed whenever the number of terminals exceeds the system parameter value. For example, when the scatter factor (SF_ACKCH) is 16, the number of terminals for which one channel can be supported will be 16. If the number of terminals is greater than 16, it means that another ACK channel is to be allocated. In step 1311, the base station transmits an ACK / NACK bit to each terminal via the allocated ACK channel, as described above.

FIG. 8 is a block diagram that illustrates a

15/21 structure of an apparatus for transmitting information not encoded in the OFDM system according to an example embodiment of the present invention. This device is provided in a base station or similar.

In FIG. 8, Walsh covers (Walsh covers) 801 receive ACK / NACK bits to be transmitted to multiple N ° 1 to N ° users and cover (or broadcast) the ACK / NACK bits received with Walsh codes (or Walsh) allocated to them. Walsh codes (or Walsh functions) can use codes agreed between the base station and user user terminals using L3 signaling or similar. An adder 803 computes a sum of the ACK / NACK bits covered with the Walsh codes, and introduces the ACK / NACK bit sum into a subcarrier mapper 807. The Walsh covers 801 and the adder 803 configure a transform processor of Hadamard 805 for the realization of a unitary transform.

Under the control of a controller 08 08, the subcarrier mapper 807 maps the ACK / NACK bits to subcarriers, so that the maximum diversity gain can be obtained. For example, the subcarrier mapper 8 07 performs the mapping process so that the subcarriers are dispersed along the time and frequency axes, as illustrated in FIG. 10A. Controller 808 controls the system parameter regulation process and the channel allocation process for an ACK / NACK bit transmission, as described with reference to FIG. 13.

FIG. 10A illustrates an example of subcarriers

16/21 mapped 11 in shaded regions. The mapped subcarriers, as illustrated in FIG. 10A ,. they are dispersed for the transmission of the ACK / NACK bits, so that the maximum diversity gain can be obtained in the time and frequency axes. It is to be noted that the subcarrier mapper 807 operates on a unit of multiple OFDM symbols, rather than an OFDM symbol. In one example, a pattern of an ACKCH No. 1 illustrated in FIG. 10A, in other words, frequency and time positions of subcarriers in a transmission unit, can be predefined through the ACK channel index, as described with reference to FIG. 13, and can be agreed between the base station and the terminals. In the case where the subcarrier allocation pattern sets up an ACK channel as illustrated in FIG. 10A, a different subcarrier allocation pattern for an additionally allocated ACK channel is distinguished and indicated by the ACK channel index, as described with reference to FIG. 13.

A Multiplexer (MUX) 815 multiplexes an output from subcarrier mapper 807 with information from other control channels and then extracts a multiplexing result. Here, the other control channels are control channels with characteristics different from those of the ACK channel, for example, non-coded channels or coded channels for the transmission of a multi-bit control information, instead of a bit. A transmission from the other control channels conforms to the OFDM transmission scheme, as described with reference to FIG. 1. A channel encoder 809, a modulator 811 and an SPC 813 of FIG. 8 are used for

17/21 transmission of the other control channel information.

That is, channel encoder 809 encodes other control channel information (or multi-bit channel information). Modulator 811 modulates the encoded information. The SFC 813 converts the modulated information into parallel signals. The parallel signals are multiplexed together with an output from the subcarrier mapper 807. A multiplexing result is introduced into a Fast Reverse Fourier Transform (IFFT) processor 817. The IFFT signals are converted to a serial signal on a PSC (not shown). A CP 819 inserter inserts a CP to prevent interference to the serial signal, and transmits the signal at which the CP was inserted to a wireless network via an RF 821 processor and an 823 antenna.

FIG. 9 is a block diagram illustrating a structure of an apparatus for transmitting information not encoded in the OFDM system according to another exemplary embodiment of the present invention. This device is provided in a base station and the like. Due to the fact that the remaining components 903 to 919, except for the FFT processor 901 in the structure of FIG. 9, perform the same operations as those of FIG. 8, its description is omitted.

The exemplary embodiment of FIG. 9 uses the FFT processor 901 in place of the Hadamard transform processor 805 of FIG. 8 for the realization of the unitary transform. Therefore, the ACK / NACK bits of multiple users N ° 1 to N ° N in which the unit transform was performed through the FFT 901 processor are mapped to the

18/21 subcarriers. The MUX 911 multiplexes the ACK / NACK bits with information from other control channels for the transfer of multi-bit channel information, so that the channel information is transmitted to a wireless network.

The exemplary embodiments of FIG. 8 and 9 use unit transform processors, such as unit transform processor 805 and FFT processor 901. Also, transform processors with quasi-unit characteristics can be used, in other words, transform processors in which multiple sets are used. provided, elements of the same set are orthogonal to each other, and crosstalk is minimized between the elements of different sets.

In the exemplary embodiment of FIG. 8 and 9, subcarrier mappers 807 and 903 map subcarriers as illustrated in FIG. 10A, so that a gain in diversity of the ACK / NACK bits in which the unit transform was performed can be maximized. Also, the subcarriers can be mapped, so that a high diversity gain is obtained, as illustrated in FIG. 10B. It may be useful for a diversity to be obtained in a particular sub-band 13, as illustrated in FIG. 10B, when a terminal prefers a particular subband, in other words, a base station transmitter knows that a channel state of the particular subband is good and channel states of the remaining subbands are bad.

In the following, a receiver of an example embodiment of the present invention will be described with reference to FIG. 11 and 12. For convenience, an operation for receiving

19/21 bits of ACK / NACK will also be described in an example receiver mode.

FIG. 11 is a block diagram illustrating a structure of an apparatus for receiving non-coded information in the OFDM system according to an example embodiment of the present invention. This device is provided in a user terminal and so on.

In the receiver structure of FIG. 11, the remaining components 1101 to 1109 and 1113 to 1117, except for a Demultiplexer (DEMUX) 1111, a unit transform processor 1119, and a controller 1121 have the same configurations as those of a conventional OFDM receiver. In FIG. 11, an OFDM symbol received through antenna 1101 and RF processor 1103 includes the ACK / NACK bits. CP remover 1105 removes a CP from the received OFDM symbol. The SPC 1107 converts a signal from which the CP has been removed to parallel signals. Parallel signals are input to the FFT 1109 processor. The DEMUX 1111 demultiplexes an output from the FFT 1109 processor according to a type of channel received, and extracts a demultiplex result for a predefined path.

For channels for transferring multi-bit control information, a reception path is set to a first path connected to the PSC 1113. The channels are demodulated and decoded according to the conventional OFDM reception operation. For channels for the transfer of unencrypted 1-bit information, such as an ACK / NACK bit, a receiving path is set to a second path connected to the data processor.

20/21 unit transformed 1119. Under the control of the controller

1121, the channels undergo an inverse Hadamard transform or IFFT, so that the ACK / NACK bit and the like are extracted.

When a reverse Hadamard transform processor is used as the 1119 unit transformation processor, it can be implemented with, for example, a component for performing a Walsh cover removal. In this case, controller 1121 performs a control operation so that a Walsh cover removal can operate using a Walsh code allocated to an associated terminal.

FIG. 12 is a flow chart illustrating a method for receiving uncoded information according to an example embodiment of the present invention. This method indicates a terminal receiving operation and so on.

When the terminal receives information from a particular channel over a wireless network in step 1201, the

DEMUX 1111 demultiplexes the received channel information for a pre-defined path according to a type of channel received in step 1203. Upon determining that the received channel is a channel for the transmission of unencrypted information, such as a data bit. ACK / NACK in step 1205, the terminal performs an inverse unit transform in the received information and extracts the information transformed in step 1207. Upon a determination that the received channel is a coded channel for the transmission of multiple bits in step 1205, the terminal processes the received information according to a reception operation

21/21 OFDM in step 1209.

As is evident from the above description, the exemplary embodiments of the present invention can improve the reliability of receiving associated channels by providing an efficient transmission / reception method and an apparatus, when unencrypted information or 1 bit information is transmitted to a user via a radio channel in a wireless communication system, based on OFDM.

Furthermore, the exemplary embodiments of the present invention can improve a gain in diversity when 1-bit control information is transmitted to a plurality of users in an OFDM system.

Although exemplary embodiments of the present invention have been shown for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the present invention. Therefore, the present invention is not limited to the modalities described above, but is defined by the following claims, together with its full scope of equivalents.

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