KR20070061687A - Apparatus and method of ofdma system with channel capacity increment using group orthogonal code and binary value - Google Patents

Abstract

An OFDMA apparatus having effect on increase in a channel capacity using a grouped orthogonal code signal value and a method thereof are provided to reduce a PAPR(Peak-to-Average Power Ratio) in the OFDMA and improve a performance efficiently by grouping a binary code having orthogonality. An OFDMA apparatus having effect on increase in a channel capacity using a grouped orthogonal code signal value includes the steps of: grouping a binary code having orthogonality in the same subchannel, and using the same in a channel capacity increase; reducing an interference of a similar neighboring subchannel; using a subchannel having a predetermined gap for a grouped orthogonal characteristic; re-using the same orthogonal code by grouping the binary code having the orthogonality and using the same orthogonal group at the subchannel having a gap which is not neighbored; reducing a PAPR in the OFDMA by grouping the orthogonal code; lessening MAI(Multiple Access Interface) by an MUD(Multi User Detection); and performing channel estimation by using a preamble.

Description

FIELD OF METHOD OF OFDMA SYSTEM WITH CHANNEL CAPACITY INCREMENT USING GROUP ORTHOGONAL CODE AND BINARY VALUE}

1 to 6 are diagrams showing the entire OFDMA method and apparatus having a channel capacity increasing effect using the grouped orthogonal code signal values proposed in the present invention.

The present invention applies a method of distinguishing different signals from different users and the same user using a grouped orthogonal code and a unique spreading code to OFDMA, grouping binary codes having orthogonality into the same subchannel and Orthogonal group that has the same subchannel with non-neighboring distance by using subchannels to increase capacity, reduce interference of similar neighboring subchannels, and use grouped orthogonal characteristics more than a certain distance for differentiation. Recycle the same orthogonal code. In addition, PAPR can be reduced in OFDMA by grouping orthogonal codes, and by classifying into orthogonal groups, MAI can be alleviated by multi-user detection (MUD), and channel estimation is also performed by using preamble to improve performance. Belongs to.

Although OFDMA enhances the diversity effect by using multiple subcarriers, it is difficult to efficiently use a frequency band because one user uses multiple subcarriers, and in the modulation and demodulation scheme to support increasing data rates in a limited frequency band, Although the data rate is increased by using the QAM modulation method, there is a problem in terms of performance in terms of performance and more than 16-QAM at a certain distance apart from mobility. Recently, after the announcement that the channel capacity is proportional to the number of transmit / receive antennas in the same bandwidth by using multiple input / receive antennas (MIMO: Multiple Input Multiple Output) in a channel having rich scattering characteristics, various received signal detection methods have been described. It is known that the utilization method is studied, and this method is known to maintain the channel (rich scattering), and because the state of the channel is changed, the performance is improved by using the transmission rate suitable for the channel state.

In order to improve the diversity effect by using multiple subcarriers in OFDMA, the use of multiple subcarriers by one user requires the efficient use of frequency bands.

Accordingly, in order to solve the above problem, a binary code having orthogonality is applied to OFDMA by applying a method of distinguishing different signals from different users and the same user using a grouped orthogonal code and a unique spreading code. Are used to increase the channel capacity by grouping them in the same subchannel, using subchannels that have grouped orthogonal characteristics more than a certain distance to reduce interference of similar neighboring subchannels and differentiate, and grouping binary codes with orthogonality to distance that is not neighbors. Since subchannels with are using the same orthogonal group, the same orthogonal code is recycled. In addition, PAPR in OFDMA can be reduced by grouping orthogonal codes, and MAI due to multi-user detection (MUD) can be mitigated by classifying into orthogonal groups, and channel estimation is also performed by using preamble to improve performance. There is a purpose.

OFDMA using orthogonal sequence in channel capacity increase using grouped orthogonal code signal values according to the present invention for achieving the above object is a binary signal and an orthogonal code block, a unique spread code synthesizer, a subchannel group and a unique spread code pseudo noise sequence It consists of an orthogonal frequency division multiplex (OFDM) block having a channel function using a (PN sequence), a modulation control block, and a transmission / reception processing block.

OFDMA with sub-carrier grouping provides diversity gain to mitigate frequency-selective fading, but the number of users who can actually serve it is reduced to, and the available frequency tone of OFDMA is N and the group When the number of sub-carriers to be formed is called, the peak-to-average power ratio (PAPR) increases. To improve system capacity and PAPR

OFDMA has an effect of increasing channel capacity using grouped orthogonal code signal values. In order to increase the number of users that can be supported, the subcarrier group is shared and the orthogonal code signal value having the channel capacity increase effect is considered. Data from supportable users is divided into a number of sub streams not larger than the maximum sub carrier, and each sub stream data is divided in the frequency domain.

It is spread by an orthogonal code having a channel capacity increasing effect and transmitted on subcarrier channels in the same group.

Orthogonal codes with channel capacity enhancements within a subcarrier group can distinguish sub streams, and because subcarrier groups are orthogonal, they can be used in other subcarrier groups and can be reused in other subcarrier groups. Indicates. Since the data sub streams of the same user are transmitted on the same sub carrier channel, a maximum-likelihood multi-user detection method may be used to recover user data in a single sub carrier group at the receiver.

First, a method for realizing a rate capacity increase will be described as follows, and a capacity increase using a basic structure value of a single binary signal for realizing a capacity increase using an orthogonal code used for capacity increase will be described.

In the present invention, the OFDM having the channel capacity increasing effect using the grouped orthogonal code signal values in the channel capacity increase using the orthogonal code and binary signal values is as follows. (Figure 1-1), (Figure 1-2) and (Figure 1-3) are the basic structure diagram of single binary signal to realize the capacity increase by using the orthogonal code used for the capacity increase. The capacity increase will be described.

In the figure of channel capacity increase using orthogonal code and binary signal value of (Figure 1), if input data exists, it is passed through single orthogonal code block (TOC) and unique spread code to realize capacity increase using orthogonal code (Figure 1). -4) is output to the serial / parallel converter, and this process is shown in (Figure 1) to (S / P) and (S-P) of (Figure 1-1) and Sub-W (4 X 4) of (Figure 1-2). ), Using the binary input signal values in the diffusion code of (Figure 1-3).

In (Figure 1), binary signals output from the serial / parallel (S / P) of (Figure 1-1) are respectively d (1) = (d, -d, d, d), where d is the signal point ( The minimum distance of the constellation). In the TOC block of (Figure 1-1) and (1-2), (Figure 1-2-1), (Figure 1-2-2), (Figure 1-2-3), (Figure 1-2-2) ) Shows the orthogonal codes Sub-w (1), Sub-w (2), Sub-w (3), and Sub-w (4), respectively, and Figure 1-3 shows the unique diffusion code. Each orthogonal code, a unique spread code, and binary signal data will be described as follows. 0 is represented by-and 1 by +.

Orthogonal code

 Sub-w (1) = (1 1 1 1)-> (+ + + +),

 Sub-w (2) = (1 0 1 0)-> (+-+-),

Sub-w (3) = (1 1 0 0)-> (+ +--),

   Sub-w (4) = (1 0 0 1)-> (+--+) and

Unique spreading code

W1 = (0 1 0 1 0 1 0 1)-> (-+-+-+-+)

Input data binary signal passing through S / P of (Figure 1-1)

d (1) = (d, -d, d, d)

d is considered a constant and eliminated and later multiplied by d (1) = (+1 -1 +1 +1).

In this case, multiply Sub-w (1), Sub-w (2), Sub-w (3), Sub-w (4) and the non-binary signal d (1) in (Figure 1-2).

C (1) = (+1 + 1 + 1 +1)

C (2) = (-1 +1 -1 +1)

C (3) = (+1 +1 -1 -1)

C (4) = (+1 -1 -1 +1),

The sum of these values is respectively

 (+2 +2 0 2)

Multiply the sum by W1

(-2 +2 -2 +2 0 0 -2 2)

The above values are the output values just before the serial / parallel conversion in Figure 1-5.

The serialized signal is grouped into n1 subchannel groups as needed in the user subcarrier channel OFDMA processing of (Figure 1-6) and allows user data to be transmitted to the subcarrier channel available to each user. After subchannel grouping to the grouped user group, the output is inputted in parallel / serial with IFFT of (Figure 1-8) after the guard interval processing of (Figure 1-7).

After performing parallel / serial conversion with IFFT in (Figure 1-8), data processed by the modulator in (Figure 1-9) is transmitted through each antenna.

The process of finding the original signal by demodulation is as follows.

The received data S (t) is processed through the demodulator of (Figure 3-2) through the antenna of (Figure 3-1) and then output to the analog-to-digital converter and guard block eliminator of (Figure 3-3).

The analog-to-digital converter, guard interval elimination and FFT / frame start point estimator in Figure 3-3 convert the analog signal to digital and then remove the guard interval and output it to the FFT in Figure 3-4. Here, the frame / FFT starting point estimation signals (Fig. 3-14) and (Fig. 3-13) are the complex FFT of Fig. 3-4 and the channel estimation and phase delay compensator parts of Fig. 5, respectively. 5-5) is connected to (Fig. 3-13), the signal is input to the fast Fourier transducer (Fig. 3-14) and the signal is connected to (Fig. 5-5), and the channel signal input of each subchannel group ( Through the correlator correlated with Figure 5-4), phase compensation and channel characteristics are estimated by correlated output values. In this case, the estimated value of each subchannel is estimated by using the interpolation and extrapolation of each grouped data subchannel and phase delay. The estimated outputs are plotted in n1 groups of equalization demodulators (Figure 3-6-1), (Figure 3-6-2) and (Figure 3-6-n1) that equalize and demodulate each grouped subchannel data. After the input and equalization and demodulation of the input data of the sub data channel are performed, the OFDMA process processes each available user sub carrier channel in (Figure 3-7), and the output data is shown in each of (Fig. 3-8). This is output to the eigenspread multiplier of. The output value is output to the De-TOC block of (Figure 3-9). In the De-TOC block, the input data is multiplied by Sub-w (1) ~ (4), respectively.

(1) (+2 +2 +2 +2 0 0 2 2)

(2) (-2 -2 2 2 0 0 2 2)

(3) (+2 +2 +2 +2 0 0 2 2)

(4) (+ 2 + 2 -2 -2 0 0 2 2)

Multiply each value by d for one period and divide by the value for one period (wherein one period of W1 is integrated by 1/8 period intervals each to be the total integration interval)

It returns to (d, -d, d, d) and returns the original value through a parallel / serial process.

In the correlation process of (Figure 5-1), in order to measure the reception channel status, it is received at (Fig. 5-5) periodically in accordance with the FFT / frame start point in (Figure 3-14) and each grouping sub-channel (Figure 3). -5-1), (Figure 3-5-2) and (Figure 3-5-n1) input the received signals to (Figure 5-4) and use these signals to correlate some of the sub channels among the sub channels. The value is obtained to perform phase compensation and channel state estimation. Estimated output is output as (Figure 5-3), n1 group equalization demodulator (Figure 3-6-1), (Figure 3-6-2), (which equalizes and demodulates each grouped subchannel data. It is input in Figure 3-6-n1) to equalize and demodulate the input data of sub data channel.

 In Figure 6, the orthogonal code binary signal value and channel capacity increase principle shows the time domain, frequency domain, preamble, subcarrier channel and grouping relationship of OFDMA in (Grip 6-1). 2 shows the use of orthogonal codes for increasing channel capacity in each subcarrier channel.

The OFDMA system bandwidth, which is divided into many orthogonally overlapped subcarriers, can be shared among several users. With sufficiently narrow bandwidth, each subcarrier can be seen as flat fading, even when selective fading occurs at full system bandwidth. Accordingly, modulation and coding with bandwidth and efficient power can be applied adaptively to signal-to-noise ratio (SNR) applicable to different subcarriers. The orthogonality of the sun carriers is maintained by inserting a cyclic prefix guard time longer than the channel delay thread into the transmission signal data. Nevertheless, deep fading can occur, resulting in data loss and performance degradation, resulting in low SNR. Multiple subcarriers can be divided and used by many users for high bandwidth usage. Multiple access interference (MAI) can be reduced by effective diversity using multiple subcarriers. It is difficult to accurately up-to-date channel information in a transmitter in a frequency selective channel that changes rapidly in time.

In order to solve this problem and efficiently increase the channel capacity, the OFDMA is applied to the OFDMA by using a grouping orthogonal code and a unique spreading code to distinguish different signals of different users from the same user. Grouping codes in the same subchannel is used to increase channel capacity, and subchannels that have grouped orthogonal characteristics over a certain distance for reducing interference and differentiation of similar neighboring subchannels, and grouping binary codes with orthogonality are not neighbors. Since subchannels with distance use the same orthogonal group, the same orthogonal code is reused. In addition, PAPR in OFDMA can be reduced by grouping orthogonal codes, and MAI due to multi-user detection (MUD) can be alleviated by classifying into orthogonal groups, and more efficient performance should be improved.

Claims (2)

In the present invention, a method of distinguishing different signals from different users and the same user using a grouped orthogonal code and a unique spreading code is applied to OFDMA, and grouping binary codes having orthogonality in the same subchannel and channel Orthogonal group that has the same subchannel with non-neighboring distance by using subchannels to increase capacity, reduce interference of similar neighboring subchannels, and use grouped orthogonal characteristics more than a certain distance for differentiation. Recycle the same orthogonal code. In addition, PAPR can be reduced in OFDMA by grouping orthogonal codes, and by classifying orthogonal groups, MAI can be mitigated by multi-user detection (MUD), and channel estimation can also be performed by using preamble to improve performance. Way In the present invention, a method of distinguishing different signals from different users and the same user using a grouped orthogonal code and a unique spreading code is applied to OFDMA, and grouping binary codes having orthogonality in the same subchannel and channel Orthogonal group that has the same subchannel with non-neighboring distance by using subchannels to increase capacity, reduce interference of similar neighboring subchannels, and use grouped orthogonal characteristics more than a certain distance for differentiation. Recycle the same orthogonal code. In addition, PAPR can be reduced in OFDMA by grouping orthogonal codes, and by classifying orthogonal groups, MAI can be mitigated by multi-user detection (MUD), and channel estimation can also be performed by using preamble to improve performance. Device

Images