WO2015046907A1

WO2015046907A1 - Transceiving method and apparatus for modulation signal transmission in filter bank multi-carrier communication system

Info

Publication number: WO2015046907A1
Application number: PCT/KR2014/008949
Authority: WO
Inventors: 남형주; 최수용; 김찬홍; 최문창; 김상우
Original assignee: 삼성전자 주식회사; 연세대학교 산학협력단
Priority date: 2013-09-27
Filing date: 2014-09-25
Publication date: 2015-04-02

Abstract

The present invention relates to a transceiving method and apparatus that enable QAM signal transmission in a filter bank multi-carrier (FMBC) communication system and provides, in particular, a transceiving method and apparatus that enable quadrature amplitude modulation (QAM) signal transmission without intrinsic interference by separating filtering between a sub-carrier having an even index and a sub-carrier having an odd index, and superimposing and transmitting sub-carriers filtered by means of separation. The thus-rendered present invention is a transmission method in the FBMC communication system, the method comprising the steps of: dividing at least two QAM signals into a plurality of groups; performing filtering on each of the plurality of groups; and superimposing and transmitting the QAM signal in the plurality of groups filtered on a time axis. The present invention relates to a transmission method and apparatus, and a corresponding reception method and apparatus.

Description

Transmitting / receiving method and apparatus for modulating signal transmission in filterbank based multicarrier communication system

The present invention relates to a transmission and reception method and apparatus capable of transmitting a QAM signal in a filter bank multicarrier (FBMC) communication system, and in particular, to separate filtering between subcarriers having an even index and subcarriers having an odd index. In addition, the present invention provides a transmission and reception method and apparatus for transmitting QAM signals without intrinsic interference by overlapping transmission of separated and filtered subcarriers using orthogonality of a filter.

Recently, a research on a filter bank multicarrier (FBMC) communication system as a next-generation communication technology that can replace orthogonal frequency division multiplexing (OFDM) transmission technology to transmit high quality data at high speed has been conducted. Actively done. FBMCs generate relatively lower out-of-band radiation than OFDM, so that the number of guard subcarriers for satisfying the same spectrum mask can be relatively reduced compared to OFDM. Modulation and demodulation of the signal without cyclic prefix increases the spectral efficiency and has strong characteristics against frequency synchronization error.

The conventional FBMC communication system includes (1) a transmission and reception method that applies a polyphase network (PPN) on the time axis after the IFFT, and (2) a frequency spreader and overlap / overlap on the frequency axis before the IFFT. / sum) can be divided into a transmission and reception method applying the structure. Technique (1) implements the convolution operation on the time axis using PPN as a filtering consisting of the sum of weighted sums of length M, and then applies two PPN modules with time difference to offset-QAM. Implement (OQAM). At this time, since the time axis filtering is performed at the transmitter, the receiver uses an equalizer on the time axis. The technique (2) performs oversampling and filtering by the prototype filter on the frequency axis before the IFFT, and performs the overlapping transmission using the adder and the memory after performing the IFFT of KM length. At this time, since the filtering is performed on the frequency axis at the transmitter, the receiver uses a frequency axis one-tap equalizer.

The above-described technique (2) will be described in more detail.

FIG. 1 is a block diagram showing a transmitting device in a conventional FBMC communication system, and FIG. 2 is a view showing a signal flow in detail when K = 4 in a transmitting device in a conventional FBMC communication system.

Referring to FIG. 1, the transmission signal d (n) is composed of M Offset Quadrature Amplitude Modulation (OQAM) signals d (mM) as shown in FIG. 2. The OQAM signal is converted by a serial-to-parallel (S / P) converter 110, and each converted OQAM signal d _i (mM) is represented by a frequency spreader 120, as shown in FIG. As spread out on the frequency axis. The spreader 120 uses a prototype filter to multiply each OQAM signal by 2K-1 frequency axis filter coefficients, thereby spreading the entire OQAM signal into KM signals over the entire frequency band. This is called frequency axis filtering.

The filtered signal is subjected to an inverse Fourier transform process by an inverse fast fourier transform (IFFT) 130. Lastly, the IFFT 130 output signal is transmitted through a superposition process by a paralleller-to-serial (P / S) and overlap / sum block 140.

In the conventional FBMC system, in order to perform frequency axis filtering, since spreading results between adjacent QAM signals overlap in a spreading process, interference with each other may cause interference and signal recovery may not be possible. In order to prevent this, the conventional FBMC system uses OQAM, which interposes in-phase and real-phase quadrature components with time-frequency resources.

In addition, in order to perform frequency axis filtering in the conventional FBMC system, since the size of the IFFT 130 must be increased by K times the overlapping factor of the prototype filter compared to the OFDM, the complexity of the entire system is increased. Since the same problem appears in the receiving apparatus, the FFT size in the receiving apparatus must also be increased by a multiple of K, thereby increasing the complexity of the receiving apparatus.

4 is a block diagram showing a receiving apparatus in a conventional FBMC communication system.

Referring to FIG. 4, the received signal x (n) is converted into a parallel signal by the S / P converter 210 and undergoes a Fourier transform process through a fast fourier transform (FFT) 220. Next, the signal is equalized through a frequency equalizer 230 and filtered through a frequency de-spreader 240 to recover the frequency axis. When the QAM signal is used as described above in the frequency axis filtering process, there is a problem that internal interference cannot be removed.

In the above-described conventional FBMC communication system, in the case of both (1) and (2) techniques, the filtering result between adjacent signals overlaps, so that the QAM signal should not be used and the OQAM signal should be used. As a result, the conventional FBMC communication system has a disadvantage that it is not easy to combine with multiple-input and multiple-output (MIMO).

In particular, in the case of (2), there is an advantage that one-tap frequency axis equalizer can be used in the receiving device due to frequency axis filtering, while complexity increases by increasing the size of IFFT and FFT by K times. .

The present invention separates filtering of a signal corresponding to an even index subcarrier and an signal corresponding to an odd index subcarrier, and superimposes a filtered signal by using the orthogonality of the filter. The present invention provides a method and apparatus for transmitting a QAM signal in an FBMC communication system.

In addition, the present invention overcomes the disadvantage that the size of the IFFT and FFT increases by the overlapping factor K in the conventional OQAM-based FBMC communication system, and by using a frequency axis one-tap equalizer in the receiving device, an efficient transmission and reception method with low complexity And an apparatus.

In order to solve the above problems, a transmission method according to the present invention is a transmission method in a filter bank based multi-carrier (FBMC) communication system, at least two Quadrature Amplitude Modulation (QAM) signal Dividing into a plurality of groups; Performing filtering on the plurality of groups, respectively; And overlapping and transmitting the QAM signals included in the filtered plurality of groups on a time axis.

In addition, the reception method according to the present invention is a reception method in a filter bank based multi-carrier (FBMC) communication system, comprising: dividing a received signal into a plurality of groups; Performing filtering on the plurality of groups, respectively; And restoring at least two Quadrature Amplitude Modulation (QAM) signals by equalizing the filtered result on the frequency axis.

In addition, the transmission apparatus according to the present invention is a transmission apparatus in a filter bank based multicarrier (FBMC) communication system, at least two quadrature amplitude modulation (QAM) signal divided into a plurality of groups Filtering unit for performing the respective filtering; An overlapping unit overlapping QAM signals included in the filtered plurality of groups on a time axis; And a communication unit for transmitting the superimposed signal to the outside.

In addition, the receiving apparatus according to the present invention, a filter bank based multi-carrier (Filter Bank Multicarrier (FBMC)) communication device in the receiving device, the communication unit for receiving a signal; A filtering unit dividing the received signal into a plurality of groups and performing filtering respectively; And an equalizer for equalizing the filtered result on the frequency axis to restore at least two Quadrature Amplitude Modulation (QAM) signals.

The transmission and reception method and apparatus for enabling QAM signal transmission according to the present invention can suppress generation of internal interference by filtering separation.

In addition, the transmission and reception method and apparatus for enabling the transmission of the QAM signal according to the present invention can process a complex signal (complex signal) can be easily combined with the MIMO system while applying the QAM-based technique in the OFDM as it is in the FBMC Has

1 is a block diagram showing a transmission apparatus in a conventional FBMC communication system.

2 is a diagram illustrating in detail a signal flow in a transmitting apparatus in a conventional FBMC communication system.

3 is a diagram illustrating a filtering process on a frequency axis in a conventional FBMC communication system.

5 is a block diagram showing a transmission apparatus according to the present invention.

6 is a diagram illustrating a filtering process on a frequency axis in a transmission apparatus according to the present invention.

7 is a diagram illustrating an example of transforming a convolution operation of a frequency axis into a multiplication operation of a time axis.

8 is a diagram illustrating an example of transforming a convolution operation of a QAM signal into a multiplication operation of a time axis according to the present invention.

9 is a diagram illustrating an example of overlapping IFFT output signals in a transmission apparatus according to the present invention.

10 is a block diagram showing the configuration of a receiving apparatus according to the present invention.

11 is a view showing in detail the flow of signals in the transmitting apparatus according to the present invention.

12 is a diagram illustrating an example of overlap & sum of consecutive FBMC symbols.

13 is a view showing in detail the flow of the signal in the receiving apparatus according to the present invention.

14 is a flowchart illustrating a transmission method according to the present invention.

15 is a flowchart illustrating a receiving method according to the present invention.

Embodiments according to the present invention are described in connection with a transmitting device and a receiving device. The transmitting device and the receiving device are referred to as a system, subscriber unit, subscriber station, mobile station, mobile, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent, user device, or user equipment (UE). Can be. The transmitting device and the receiving device may be cellular telephones, personal digital assistants (PDAs), handheld devices with wireless connection capabilities, computing devices or other processing devices connected to a wireless modem.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments and are not intended to limit the spirit of the present invention. In addition, technical terms used herein should be interpreted as meanings generally understood by those of ordinary skill in the art to which the present invention belongs, unless specifically defined otherwise in the present specification, and excessively comprehensive It should not be construed in meaning or in excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In this specification, "configured." Or "includes." And the like should not be construed as including all of the various elements or steps described in the specification.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

5 is a block diagram showing the configuration of a transmission apparatus according to the present invention.

Referring to FIG. 5, the transmission apparatus 300 according to the present invention includes a plurality of S /

P converters

311 and 312, a plurality of

IFFTs

321 and 322, and a plurality of weighted sum blocks 331 and 332. It is composed. The plurality of S /

P converters

311 and 312, the plurality of

IFFTs

321 and 322, and the plurality of weighted sum blocks 331 and 332 may participate in the filtering operation on the QAM signal. Accordingly, the plurality of S /

P converters

311 and 312, the plurality of

IFFTs

321 and 322, and the plurality of weighted sum blocks 331 and 332 may be named as filtering units, respectively or in combination.

As shown in FIG. 5 and FIG. 6, the transmitting apparatus 300 according to the present invention divides the M QAM signals into a first group and a second group, and performs filtering of each group separately. In this case, the transmitter 300 may classify the QAM signals so that adjacent QAM signals belong to different groups. For example, the transmitter 300 may divide the M QAM signals into two groups, a signal having an even index and a signal having an odd index. As a result, the transmitter 300 according to the present invention prevents internal interference between adjacent QAM signals as shown in FIG. 6.

According to various embodiments of the present disclosure, when filtering each group separately, filters applied to each group may be configured to have a complex relationship with each other. For example, when filtering the first group and the second group separately, the first group is filtered using the first filter and the second group is filtered using the second filter. The two filters can be configured to have a complex relationship. That is, the filter coefficients of the filter applied to the second group may be composed of complex values of the filter coefficients of the filter applied to the first group. In one embodiment, when the coefficients of the filter applied to the first group are configured with a real domain, the coefficients of the filter applied to the second group may be configured with a complex domain. That is, the first filter applied to the first group

If you have a real domain filter coefficient consisting of the second filter applied to the second group

It may have a complex domain filter coefficient consisting of.

In addition, according to the present invention, the transmitting apparatus 300 may perform separate filtering by a frequency spreading method before the IFFT, and in one embodiment, convolution on the time axis after the IFFT in order to prevent the complexity from increasing. Filtering can be performed by multiplication rather than by).

The existing filtering process using multiplication after spreading on the frequency axis shown in FIG. 6 may be reinterpreted as a convolution of a signal having 0 inserted between QAM signals and filter coefficients for one QAM signal. In this case, when the original QAM signals to be filtered are transformed into the time axis due to zero interpolation between the signals, the IFFT output signal of the original signal is repeated K-1 times. Therefore, the filtering process may be reinterpreted by calculating weighted sum of IFFT output data for the M signals and KM time-axis filter coefficients in block units, as shown in FIG. 7. 7 shows an example where K is four.

Referring to FIG. 8, when M QAM signals are divided into two groups, M / 2 QAM signals having an even index and M / 2 QAM signals having an odd index, K-1 between signals in FIG. 7. Unlike the 0 zeros, 2K-1 zeros are inserted between the signals. Therefore, if the IFFT operation is reinterpreted as the convolution law, the IFFT output signal has a form in which the IFFT output block of the signal is repeated 2K-1 times, and the size is M / 2. The transmitter 300 may perform filtering by multiplying the IFFT output signal by KM time-axis filter coefficients. In this case, a block that performs a multiplication operation may be called a multiplier.

In addition, in the present invention, the transmission device 300 performs an overlap / sum operation of a unit of 2K blocks on the time axis through the overlap / sum block 340 and the P / S converter 350. Referring to FIG. 9, the transmitting apparatus shows an IFFT output block for the first group and the second group in FIG. 6, for example, an IFFT output block for the even signal and the odd signal. The transmission is overlapped as shown. In particular, in an embodiment of the present invention, when the IFFT output signal overlaps, the transmitting device 300 arranges and overlaps any one of the IFFT output signal of the first group and the IFFT output signal of the second group in reverse order. The overlap / sum block 340 may be referred to as an overlap in one example. In the FBMC transmission / reception scheme, when the overlapping transmission is performed using the orthogonality between the filters as shown in FIG. 9, since the even and odd signals do not affect each other, the QAM signal may be transmitted.

The superimposed signal may be transmitted to the receiving device through the communication unit of the transmitting device.

Referring to FIG. 10, the receiving device 400 according to the present invention obtains a received signal through a communication unit. The received signal passes through the S / P converter 410, the weighted sum blocks 421 and 422, and the

FFT converters

431 and 432, and then through the one-

tap equalizer

441 and 442 one on the frequency axis. Tap equalization The received signal is then restored to the final signal via the P /

S converters

451 and 452.

Hereinafter, a detailed signal conversion process in the transmitter and the receiver according to the present invention will be described.

Referring to FIG. 11, the transmission signal d (n) is composed of M signals. According to the invention, the signal is classified into a first group and a second group. Accordingly, the signals d ₁ (n) and d ₂ (n) included in each group have a size of M / 2. In an embodiment of the present invention, adjacent signals are classified into different groups. For example, the signal may be classified into a first group consisting of a signal having an even index (hereinafter, even signal) and a second group consisting of a signal having an odd index (hereinafter, an odd signal).

Signals included in the first group and the second group are transformed into time axis data as shown in FIG. 6 through separate S / P and IFFT conversion processes, respectively. 6 is a diagram illustrating an example in which filtering is performed by separating the even signal (upper) and the odd signal (lower), respectively. Referring to FIG. 6, when adjacent signals are classified into different groups, the classified signals undergo S / P conversion and IFFT conversion, respectively, so that internal interference as shown in FIG. 3 does not occur.

The output signal by the IFFT conversion of FIG. 11 is stored in order from the first memory to the 2K-2nd memory. Thereafter, the signals stored in the memory are superimposed by KM time-axis filter coefficients and M / 2 block unit addition operations and transmitted to the outside via P / S. In an embodiment of the present invention, the time axis filter coefficients may have different values according to K values.

Referring to Figure 12, the horizontal axis means the time axis. One sub block represents a signal to which M / 2-IFFT is applied to M / 2 QAM signals. The M / 2 QAM signals with M / 2-IFFT are extended 2K-1 times and multiplied by the KM time axis filter coefficients. For the Odd signal, the 2K blocks after multiplication are reordered in reverse order with the sign changed to (-+-+ ...). Accordingly, the K FBMC symbols arranged in the same vertical column overlap each other and are finally summed and transmitted to the receiver.

Referring to FIG. 13, the signal flow in the receiving apparatus according to the present invention has a structure symmetrical with the transmitting apparatus until it passes through the equalizer. Specifically, the receiving device stores the received signals of size M in order in the memory. Thereafter, the receiving device performs a block unit multiplication operation between the KM time axis filter coefficients and the signals stored in each memory, and generates an FFT input signal of size M through a block unit add operation. The receiving device then performs an FFT operation of size M / 2 and restores the original signal using a one-tap equalizer on the frequency axis.

Referring to FIG. 14, first, a transmission apparatus divides at least two modulated signals into a plurality of groups (1401). The transmitting apparatus may divide the M modulated signals into a plurality of groups, for example, a first group and a second group. In this case, the transmitting device may divide the group such that adjacent modulated signals belong to different groups. According to an embodiment, the transmitting apparatus may divide a modulated signal into two groups, a modulated signal having an even index and a modulated signal having an odd index.

Next, the transmitting apparatus performs filtering on each of the plurality of groups (1403). The transmitting apparatus performs inverse Fourier transform on the modulated signals included in each of the plurality of groups (1405), expands the inverse Fourier transformed output signals to MK (1407), and then expands the MK output signals and the time axis filter. Filtering is performed by multiplying the coefficients (1409).

Thereafter, the transmitting apparatus overlaps each of the filtered modulated signals of each group (1411). According to an embodiment of the present disclosure, the transmitting apparatus may sort the modulated signals included in the group in reverse order (1413) for at least one group of the plurality of groups, and overlap the filtered modulated signals included in the plurality of groups. There is (1415).

The transmitting device finally transmits the superimposed signal (1417).

Referring to FIG. 15, a receiving device first receives a signal (1501).

Next, the receiving apparatus divides the received signal into a plurality of groups (1503). The receiving device performs inverse filtering on the plurality of divided groups, in operation 1505. That is, the receiving device multiplies the received signals included in each of the plurality of groups by the time axis filter coefficients (1507), and performs a Fourier transform on the output signal multiplied by the filter coefficients (1509).

As described above, the receiving apparatus processes the Fourier transformed output signal as a restored signal.

According to the above-described feature of the present invention, the transmitting apparatus divides the QAM signal into a plurality of groups to separate the filtering process for each group, and transmits the QAM signal through overlapping transmission utilizing the orthogonality of the filter. The complexity of IFFT and FFT can also be used to implement filtering through weighted sum on the time axis.

The embodiments disclosed in the specification and the drawings are only specific examples to easily explain the contents of the present invention and assist in understanding, and are not intended to limit the scope of the present invention. Therefore, the scope of the present invention should be construed that all changes or modifications derived based on the technical spirit of the present invention are included in the scope of the present invention in addition to the embodiments disclosed herein.

Claims

A transmission method in a filter bank multicarrier (FBMC) communication system,

Dividing at least two modulated signals into a plurality of groups;

Performing filtering on the plurality of groups, respectively; And

And transmitting the modulated signals included in the filtered plurality of groups overlapping each other on a time axis.
The method of claim 1, wherein the dividing into a plurality of groups comprises:

Dividing adjacent modulated signals into different groups.
The method of claim 1, wherein the dividing into a plurality of groups comprises:

And dividing into a first group consisting of a modulated signal having an even index and a second group consisting of a modulating signal having an odd index.
The method of claim 1, wherein performing the filtering comprises:

Performing inverse Fourier transform on each of the plurality of groups; And

And performing a multiplication operation using the inverse Fourier transformed output signal and a time axis filter coefficient.
The method of claim 4, wherein performing the multiplication operation,

Expanding M / 2 of the inverse Fourier transformed output signals for each group to M / 2 * 2K; And

And multiplying the M / 2 * 2K output signals by a time axis filter coefficient of M / 2 * 2K.
The method of claim 5, wherein the expanding step,

And repeatedly extending the inverse Fourier transform output signal for the M / 2 modulated signals included in each group by 2K times.
The method of claim 5, wherein the expanding step,

And inserting 2K-1 zero symbols between the M / 2 of the inverse Fourier transformed output signals.
The method of claim 1, wherein the step of transmitting in a superimposed manner,

Sorting the modulated signals included in at least one of the filtered plurality of groups in reverse order; And

And superposing a modulation signal included in the at least one group arranged in the reverse order and a modulation signal included in the remaining group.
The method of claim 1, wherein the modulated signal,

Transmission method characterized in that the Quadrature Amplitude Modulation (QAM) signal.
The method of claim 1, wherein the dividing into a plurality of groups comprises:

Dividing the at least two modulated signals into a first group and a second group,

Performing the filtering,

And performing filtering on the first group and the second group by using a first filter and a second filter, respectively.
The method of claim 1, wherein the plurality of groups,

Transmitting the same number of modulated signals.
A reception method in a filter bank based multicarrier (FBMC) communication system,

Dividing the received signal into a plurality of groups;

Performing filtering on the plurality of groups, respectively; And

Recovering at least two modulated signals by equalizing the filtered result on a frequency axis.
The method of claim 12, wherein the dividing into a plurality of groups comprises:

And dividing into a first group consisting of a received signal having an even index and a second group consisting of a received signal having an odd index.
The method of claim 12, wherein performing the filtering comprises:

Performing a multiplication operation using the received signal and the time axis filter coefficients included in each group; And

Fourier transforming the multiplied output signal.
The method of claim 12, wherein the modulated signal,

Receive method characterized in that the Quadrature Amplitude Modulation (QAM) signal.
The method of claim 12, wherein the plurality of groups,

Receiving method comprising the same number of modulated signals.
A transmission device in a filter bank based multi-carrier (FBMC) communication system,

A filtering unit for filtering at least two modulated signals divided into a plurality of groups;

An overlapping unit overlapping the modulated signals included in the filtered plurality of groups on a time axis; And

And a communication unit for transmitting the superimposed signal to the outside.
The method of claim 17, wherein the at least one modulated signal,

And wherein adjacent modulated signals are divided so that they belong to different groups.
The method of claim 17, wherein the at least one modulated signal,

And a first group consisting of modulated signals having an even index and a modulating signal having an odd index.
The method of claim 17, wherein the filtering unit,

An inverse Fourier transformer for performing inverse Fourier transform on each of the plurality of groups; And

And a multiplier for performing a multiplication operation by using the output signal of the inverse Fourier transform unit and a time axis filter coefficient.
The method of claim 20, wherein the multiplier,

M / 2 output signals of the inverse Fourier transform unit for each group are expanded to M / 2 * 2K, and the M / 2 * 2K output signals are multiplied by M / 2 * 2K time axis filter coefficients. Transmission device.
The method of claim 21, wherein the multiplier,

And inversely extending an inverse Fourier transform output signal for the M / 2 QAM signals included in each group by 2K times.
The method of claim 21, wherein the multiplier,

And a 2K-1 zero symbol is inserted between the M / 2 of the inverse Fourier transformed output signals to expand the output signal of the inverse Fourier transform unit.
The method of claim 17, wherein the overlapping portion,

Modulating signals included in at least one group of the filtered plurality of groups in reverse order, and overlapping modulation signals included in the at least one group arranged in the reverse order and modulation signals included in the remaining groups Transmission device.
The method of claim 17, wherein the modulated signal,

Transmitter characterized in that the Quadrature Amplitude Modulation (QAM) signal.
The method of claim 17, wherein the filtering unit,

And transmitting the at least two modulated signals into a first group and a second group, and filtering the first group and the second group by using a first filter and a second filter, respectively. .
The method of claim 17, wherein the plurality of groups,

And a transmission device comprising the same number of modulated signals.
A receiver for a filter bank based multi-carrier (FBMC) communication system,

Communication unit for receiving a signal;

A filtering unit dividing the received signal into a plurality of groups and performing filtering respectively;

And an equalizer for recovering at least two modulated signals by equalizing the filtered result on the frequency axis.
The method of claim 28, wherein the received signal,

And a second group consisting of a reception signal having an even index and a second group consisting of a reception signal having an odd index.
The method of claim 28, wherein the filtering unit,

And performing a multiplication operation using a received signal included in each group and a time axis filter coefficient, and Fourier transforming the multiplied output signal.
The method of claim 28, wherein the modulated signal,

Receiving device, characterized in that the Quadrature Amplitude Modulation (QAM) signal.
The method of claim 28, wherein the plurality of groups,

A receiving device comprising the same number of modulated signals.