CN114157542A - CE-OFDMA system signal transceiving method based on direct current component separation - Google Patents

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to a signal transceiving method of a CE-OFDMA system based on direct-current component separation. The method mainly comprises the steps of placing modulated signals generated after modulation according to a conjugate symmetric format, then mapping, obtaining a transmitting signal after phase modulation, wherein the mapped frequency domain data still needs to meet the conjugate symmetric format. The invention provides a signal receiving and transmitting method based on a direct current component separation CE-OFDMA system, which is applied to an uplink, and a transmitter can solve the problem that the carrier frequency power of each user is gathered at a carrier frequency point to cause the information loss of each user, thereby ensuring the final BER performance of each user.

Description

CE-OFDMA system signal transceiving method based on direct current component separation

Technical Field

The invention belongs to the technical field of wireless communication, and particularly relates to a method for receiving and transmitting a signal of a CE-OFDMA (Constant Orthogonal Frequency Division Multiple Access) system based on direct-current component separation.

Background

Orthogonal Frequency Division Multiple Access (OFDMA) is a commonly used Multiple Access technique in wireless digital communication, and can transmit data at a high rate on a severe wireless channel with severe multipath fading. However, the main drawback of OFDMA is that the modulation waveform has high amplitude fluctuations, resulting in a large Peak to Average Power Ratio (PAPR). The high PAPR makes OFDMA very sensitive to nonlinear distortion caused by the transmitter Power Amplifier (PA), and if there is not enough Power back-off, the spectrum of the system will be broadened and thus performance will be degraded, and solving this problem by increasing the Power back-off will reduce PA efficiency. Unlike the downlink, where the transmit power of each user is affected by the total transmit power of the base station and the transmit power of other individual users, the uplink, where the transmit power of each user is affected only by the maximum transmit power of its device. The PA efficiency problem is more severe for uplinks where power consumption is a critical requirement, and efficient amplification can be seen as a key factor for future systems operating in the future ultra-high frequency band.

A constant-envelope orthogonal frequency division multiple access (CE-OFDMA) system transmit side baseband signal has a constant-envelope characteristic with a lowest PAPR of 0dB, so that the signal can be transmitted through a saturated amplifier without amplitude distortion and spectral regeneration. In addition, compared with the OFDM signal, CE-OFDM generates correlation among subcarriers through phase modulation, can obtain certain diversity gain of multipath fading, and generates better error rate performance when the modulation index is greater than 1. However, compared to OFDMA, there is interference in subcarriers between CE-OFDMA users, and the dc components of all users are completely superimposed at the receiving end, which brings a new problem to multi-user detection.

The existing CE-OFDMA system is basically designed for downlink multi-user and mainly adopts multi-user joint detection.

Disclosure of Invention

The invention provides a signal receiving and transmitting method based on direct current component separation aiming at a CE-OFDMA system of an uplink, solves the problem that direct current components of each user of the CE-OFDMA are gathered at a carrier frequency point to cause user information loss, and improves the error rate performance of the system.

The technical scheme of the invention is as follows:

a CE-OFDMA uplink signal transceiving method based on direct current component separation sets the number of users to be U, the modulation index to be 2 pi h, the digital modulation mode to be M-QAM, and the cyclic prefix length to be N in the CE-OFDMA system_CPTotal number of subcarriers is N_DFTThe number of subcarriers of each user is N_i＝N_DFTU, then each user can transmit digital modulation as N_QAM＝(N_DFTU-2)/2, where i ═ 1, 2.

The system comprises:

transmitting end, as shown in fig. 1:

s1, modulation and mapping:

ith user bit data b_i(n),n＝1,2,...,N_QAMlog₂M generates a modulation signal X after being modulated by M-QAM_i[k],k＝1,2,...,N_QAMThen placed according to the following conjugate symmetry format:

X_i[k]＝[0,X[1],X[2],…,X[N_QAM],0,X^*[N_QAM],…,X^*[2],X^*[1]]

then sub-carrier mapping is carried out on the modulated data; then through N_DFTIFFT transformation of point length is carried out, and time domain signals are generated after parallel/serial transformation:

wherein

Is a normalization factor;

s2, phase modulation:

multiplying the time domain signal by the modulation index 2 pi h for modulation, and generating a phase modulation signal s of the user i through phase modulation_i：

s_i(n)＝Aexp[j2πhx_i(t)]

Where A is the amplitude parameter of the CE-OFDM signal. Finally, inserting the phase modulation signal into a protection prefix to obtain:

s_{CP_i}(n)＝[s_i(N_DFT-N_CP),s_i(N_DFT-N_CP+1),...,s_i(N_DFT-1),s_i(0),s_i(1),...,s_i(N_DFT-1)]

then the signal s_{CP_i}And (n) sending.

Receiving end, as shown in fig. 2:

s3, setting time domain receiving signal y_CP(n) is:

y_CP(n)＝[y_CP(0),y_CP(1),...,y_CP(N_DFT+N_CP-1)]

removing the cyclic prefix and performing serial-to-parallel conversion to obtain y (n):

y(n)＝[y(0),y(1),...,y(N_DFT-1)]

s4, channel equalization:

and the signal is changed into a frequency domain signal Y through an FFT module:

and then carrying out channel equalization on the signals, wherein the equalization method is zero-forcing equalization or minimum mean square error equalization. The equalized signal is represented as

S5, multi-user signal separation:

separating user signals according to sub-carrier mapping position

Converting the frequency domain signal to the time domain through an IFFT module to obtain a time domain signal

Calculating user signals

Average power of

Calculating a power change factor λ:

according to

And lambda, calculating the DC component C of each user_i：

Updating the time domain signal according to the direct current component:

s6, phase demodulation:

the time domain updating signal passes through a phase demodulator to obtain phase information:

wherein

And

are respectively

The real and imaginary components of (a).

S7, acquiring transmission bits:

the signal after phase demodulation is processed by an FFT module to obtain a frequency domain signal

And finally, carrying out M-QAM demodulation on the data subjected to digital modulation to obtain bit data sent by each user.

The invention has the beneficial effects that the signal receiving and transmitting method based on the direct current component separation CE-OFDMA system applied to the uplink is provided, and the transmitter can solve the problem that the carrier frequency power of each user is gathered at the carrier frequency point to cause the information loss of each user, thereby ensuring the final BER performance of each user.

Drawings

Fig. 1 is a block diagram of a transmitting end of an uplink CE-OFDMA system.

Fig. 2 is a block diagram of a receiving end of an uplink CE-OFDMA system.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.

Examples

In this example, the number of users is U-2, the modulation index is 2 pi h-0.5, the digital modulation scheme is QPSK (4-QAM), and the cyclic prefix length is N_CPTotal number of subcarriers is N as 3_DFT64, each user subcarrier number is N₁＝N₂Each user can transmit digital modulation symbol with number N as 32_QAM15, the channel parameter is the EVA channel, MMSE equalization is adopted, and ideal channel estimation is taken as an example.

A transmitting end:

step 1-1: determining parameters of the system to be selected, namely determining the number of users as U-2, the modulation index as 2 pi-h as 0.5, the digital modulation mode as QPSK, the total number of subcarriers as N_DFT64, each user subcarrier number is N₁＝N₂Each user can transmit digital modulation symbol with number N as 32_QAM15, the signal amplitude parameter a is 1. And then calculating the bit number required to be transmitted by each user according to a formula.

Step 1-2: and (4) OFDM modulation. Firstly, QPSK modulation is carried out on bit information of two users, and then the bit information is mapped to corresponding subcarrier positions according to a conjugate symmetric format and a centralized distribution mode:

user 1: x₁[k]＝[0,X₁[1],X₁[2]…,X₁[15],0_1×32,0,X₁ ^*[15],…,X₁ ^*[1]],k＝1,2,...,64

And (4) a user 2: x₂[k]＝[0_1×16,X₂[1],X₂[2]…,X₂[15],0,X₂ ^*[15],…,X₂ ^*[2],X₂ ^*[1],0_1×16],k＝1,2,...,64

Then, after IFFT conversion with the length of 64 points, generating a time domain signal after parallel/serial conversion:

wherein

Step 1-3: and (4) phase modulation. The time domain signal is multiplied by a modulation index 2 pi h which is 0.5 to modulate, and a phase modulation signal s of a user i is generated through phase modulation_iAssume that user 1 and user 2 are transmitting at equal power:

finally, inserting the phase modulation signal into a protection prefix to obtain:

s_{CP_i}(n)＝[s_i(61),s_i(62),s_i(63),s_i(0),s_i(1),...,s_i(63)]

then the signal s_{CP_i}And (n) sending.

Receiving end:

step 2-1: time domain received signal y_CP(n) is:

y_CP(n)＝[y_CP(0),y_CP(1),...,y_CP(N_DFT+N_CP-1)]

step 2-2: and (4) channel equalization. Removing the cyclic prefix and performing serial-to-parallel conversion to obtain y (n):

y(n)＝[y(0),y(1),...,y(N_DFT-1)]

and the signal is changed into a frequency domain signal Y through an FFT module:

then estimating the obtained channel parameters according to the ideal channel

And then carrying out channel equalization on the signals, wherein the equalization method is zero-breaking equalization. The equalized signal is represented as

Wherein { }^HIs a conjugate symmetric transpose transform.

Step 2-3: and (4) separating multi-user signals. Separating user signals according to sub-carrier mapping position

User 1:

and (4) a user 2:

then, the frequency domain signal is converted into a time domain signal through an IFFT module to obtain the time domain signal

Calculating user signals

Average power of

P₁＝P₂＝1

Calculating a power change factor λ:

λ＝1.77

according to

And lambda, calculating the DC component C of each user_i：

C₁＝C₂＝0.885e^-1/8

Updating the time domain signal according to the direct current component:

step 4-1: and (4) phase demodulation. The time domain updating signal passes through a phase demodulator to obtain phase information:

wherein

And

are respectively

In the form of a plurality of

The real and imaginary components of (a).

Step 4-2: the transmission bits are obtained. The signal after phase demodulation is processed by an FFT module to obtain a frequency domain signal

And

and finally, carrying out M-QAM demodulation on the data subjected to digital modulation to obtain bit data sent by each user.

The invention provides a signal transceiving method based on a direct current component separation CE-OFDMA system, which is applied to an uplink, wherein the method is applied to the uplink according to the advantage of 0dB PAPR of a CE-OFDM signal baseband, and a transmitter can solve the problem that the carrier frequency power of each user is gathered at a carrier frequency point to cause the information loss of each user, thereby ensuring the final BER performance of each user.

Claims (1)

1. A CE-OFDMA system signal transceiving method based on direct current component separation is disclosed, in the CE-OFDMA system, the number of users is U, the modulation index is 2 pi h, the digital modulation mode is M-QAM, the length of cyclic prefix is N_CPTotal number of subcarriers is N_DFTThe number of subcarriers of each user is N_i＝N_DFTU, then each user can transmit digital modulation as N_QAM＝(N_DFTU-2)/2, wherein i is 1,2, U, representing the ith user; it is characterized by comprising:

s1, modulation and mapping:

ith user bit data b_i(n),n＝1,2,...,N_QAMlog₂M generates a modulation signal X after being modulated by M-QAM_i[k],k＝1,2,...,N_QAMM is the modulation order, and then placed according to the following conjugate symmetry format:

X_i[k]＝[0,X[1],X[2],…,X[N_QAM],0,X^*[N_QAM],…,X^*[2],X^*[1]]

then sub-carrier mapping is carried out on the modulated data; then through N_DFTIFFT transformation of point length is carried out, and time domain signals are generated after parallel/serial transformation:

wherein

Is a normalization factor;

s2, phase modulation:

multiplying the time domain signal obtained in the step S1 by a modulation index 2 pi h, and generating a phase modulation signal S of the user i through phase modulation_i：

s_i(n)＝Aexp[j2πhx_i(t)]

Wherein A is an amplitude parameter of the CE-OFDM signal; inserting the phase modulation signal into the cyclic prefix to obtain a transmitting signal:

s_{CP_i}(n)＝[s_i(N_DFT-N_CP),s_i(N_DFT-N_CP+1),...,s_i(N_DFT-1),s_i(0),s_i(1),...,s_i(N_DFT-1)]

then will transmit signal s_{CP_i}(n) transmitting;

s3, setting time domain receiving signal y_CP(n) is:

y_CP(n)＝[y_CP(0),y_CP(1),...,y_CP(N_DFT+N_CP-1)]

removing the cyclic prefix and performing serial-to-parallel conversion to obtain y (n):

y(n)＝[y(0),y(1),...,y(N_DFT-1)]

s4, channel equalization:

and the FFT module converts Y (n) into a frequency domain signal Y:

then, the signal is subjected to channel equalization, and the equalized signal is represented as

S5, multi-user signal separation:

separating user signals according to sub-carrier mapping position

Converting the frequency domain signal to the time domain through an IFFT module to obtain a time domain signal

Calculating user signals

Average power of

Calculating a power change factor λ:

according to

And lambda, calculating the DC component C of each user_i：

Updating the time domain signal according to the direct current component:

s6, phase demodulation:

the time domain updating signal passes through a phase demodulator to obtain phase information:

wherein

And

are respectively

The real and imaginary components of (a);

s7, acquiring transmission bits:

the signal after phase demodulation is processed by FFT to obtain a frequency domain signal

And finally, carrying out M-QAM demodulation on the data subjected to digital modulation to obtain bit data sent by each user.

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