CN102780510B - Block mixing multiple access method - Google Patents

Abstract

Block mixing multiple access method, relates to a kind of multiple access method, and it is to overcome in ofdm system the shortcoming utilizing CP to suppress multi-path jamming.Down link: transmitting terminal: will the data of different user be sent to process in different blocks respectively, modulates output after the data of different user export from block.Receiving terminal: carry out again after the signal receiving received with the process of transmitting terminal inverse transformation after adjudicate output.Up link: transmitting terminal: modulate after the data of each bit stream of user are multiplied with code sequence respectively and export.Receiving terminal: base station by carry out again after the signal receiving received with the process of transmitting terminal inverse transformation after adjudicate output.The present invention proposes a kind of new multiple access system model, overcomes in ofdm system the shortcoming utilizing CP to suppress multi-path jamming, can suppress multi-path jamming while increasing substantially band efficiency.The present invention is applicable to carry out radio communication.

Description

Block hybrid multiple access method

Technical Field

The invention relates to a multiple access method.

Background

In an Orthogonal Frequency Division Multiplexing (OFDM) system, if multipath Interference is to be overcome, a Cyclic Prefix (CP) needs to be added to a transmitted symbol, and the length of the CP is also strictly limited, so that if the length of the CP is smaller than the maximum delay, very serious Inter-symbol Interference (ISI) and Inter-Carrier Interference (ICI) are caused. The frequency band utilization is lowered due to the addition of the CP.

Disclosure of Invention

The invention provides a block hybrid multiple access method for overcoming the defect of using CP to restrain multipath interference in an OFDM system.

Block hybrid multiple access method, which is based on the conventional implementation of OFDM systems,

the signal transmitting method of the transmitting terminal in the downlink of the system comprises the following steps:

step A1, inputting data into K blocks by K users respectively, and performing serial/parallel conversion in the K blocks respectively, wherein each user obtains M paths of parallel data;

step A2, multiplying M paths of parallel data obtained by each user in the step A1 by M paths of subcarriers respectively, and obtaining M paths of processed data by each user; the M paths of subcarriers are discrete data output by the M paths of code sequences through FFT;

step A3, performing parallel/serial conversion on the M paths of processed data obtained by each user in the step A2, and obtaining K paths of serial data by K users;

step A4, performing digital-to-analog conversion on the K paths of serial data obtained in the step A3 respectively to obtain converted K paths of analog signals;

step A5, respectively carrying out carrier modulation on the K paths of analog signals obtained in the step A4 to obtain modulated K paths of modulation signals;

step A6, respectively carrying out band-pass filtering on the K paths of modulation signals obtained in the step A5 to obtain K paths of signals subjected to band-pass filtering;

step A7, merging the K-path signals obtained in the step A6 after band pass filtering into one path, and transmitting the path to a channel;

the signal receiving method of the receiving end in the downlink of the system comprises the following steps:

step B1, receiving a modulation signal sent by a downlink transmitting end by using a receiving antenna, and performing band-pass filtering on the signal to obtain a path of signal after band-pass filtering;

b2, demodulating the path of signal after band-pass filtering obtained in the step B1 to obtain a path of demodulated signal;

b3, performing low-pass filtering on the demodulated signal obtained in the step B2 to obtain a low-pass filtered signal;

b4, performing analog-to-digital conversion on the low-pass filtered signal obtained in the step B3 to obtain a path of digital data;

b5, performing serial/parallel conversion on the path of digital data obtained in the step B4 to obtain M paths of parallel data;

b6, multiplying the M paths of parallel data obtained in the B5 by the M paths of subcarriers to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through IFFT;

b7, performing low-pass filtering on the M paths of processed data obtained in the B6 to obtain M paths of low-pass filtered data;

step B8, judging the M paths of low-pass filtered data obtained in the step B7, and outputting;

the M-way code sequence in the step A2 is the same as the M-way code sequence in the step B6;

the signal transmitting method of the transmitting terminal in the uplink of the system comprises the following steps:

step C1, performing serial/parallel conversion on the uplink data of the Kth user to obtain M paths of parallel data;

step C2, multiplying the M paths of parallel data obtained in the step C1 by the M paths of subcarriers respectively to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through FFT;

step C3, performing parallel/serial conversion on the M paths of processed data obtained in the step C2 respectively to obtain a path of serial signals;

step C4, performing digital-to-analog conversion on the path of serial signals obtained in the step C3 to obtain a path of analog signals;

step C5, carrying out carrier modulation on the one-path analog signal obtained in the step C4 to obtain one-path modulation signal;

step C6, performing band-pass filtering on the path of modulation signal obtained in the step C5 to obtain a path of signal subjected to band-pass filtering, and transmitting the signal to a channel;

the uplink signal receiving method of the system comprises the following steps:

step D1, receiving the modulation signal transmitted by the uplink transmitting end by adopting a receiving antenna, and carrying out band-pass filtering on the modulation signal to obtain a signal after band-pass filtering;

d2, demodulating the band-pass filtered signal obtained in the step D1 to obtain a path of demodulated signal;

d3, performing low-pass filtering on the demodulated signal obtained in the step D2 to obtain a low-pass filtered signal;

d4, performing analog-to-digital conversion on the low-pass filtered signal obtained in the step D3 to obtain a path of digital data;

d5, performing serial/parallel conversion on the path of digital data obtained in the step D4 to obtain M paths of parallel data;

d6, multiplying the M paths of parallel data obtained in the step D5 by the M paths of subcarriers to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through IFFT;

d7, performing low-pass filtering on the M paths of processed data obtained in the step D6 to obtain M paths of low-pass filtered data;

d8, judging the M paths of low-pass filtered data obtained in the step D7, and outputting;

the M-way code sequence in the step C2 is the same as the M-way code sequence in the step D6;

K. m is a positive integer.

In step a3, a path of serial signal obtained by each user can be divided into a real part and a virtual part for digital-to-analog conversion, carrier modulation and band-pass filtering, and then added together to form a path of band-pass filtered signal.

The invention provides a new data transmission mode of a multiple access system, overcomes the defect that the CP is used for inhibiting the multipath interference in an OFDM system, greatly improves the utilization rate of a frequency band and can inhibit the multipath interference at the same time.

Drawings

Fig. 1 is a schematic diagram of the downlink; fig. 2 is a schematic diagram of the signal processing flow of the transmitting end in the downlink of the present invention; FIG. 3 is a signal processing flow diagram of the k block in the downlink; fig. 4 is a schematic diagram of the signal processing flow at the receiving end in the downlink of the present invention; fig. 5 is a schematic diagram of the uplink principle; fig. 6 is a schematic diagram of the signal processing flow of the transmitting end in the uplink according to the present invention; fig. 7 is a schematic diagram of the signal processing flow at the receiving end in the uplink according to the present invention; FIG. 8 is a schematic diagram of a system bit error rate simulation in a first embodiment; FIG. 9 is a schematic diagram of a signal processing flow at a transmitting end of the present invention for processing signals using a real part and an imaginary part respectively; FIG. 10 is a schematic diagram of a signal processing flow at a receiving end corresponding to a method of processing signals respectively by using a real part and an imaginary part; fig. 11 is a schematic diagram in simplified form of an FFT module at a receiving end in downlink; fig. 12 is a schematic diagram of a signal processing flow of a transmitting end in an uplink when a user k transmits an ith symbol according to the first embodiment; fig. 13 is a schematic diagram of a signal processing flow at a receiving end in an uplink when a user k transmits an ith symbol according to the first embodiment.

Detailed Description

Description of the embodiments in conjunction with fig. 1 to 13, a block hybrid multiple access method, which is based on the conventional implementation of OFDM systems,

the signal transmitting method of the transmitting terminal in the downlink of the system comprises the following steps:

step A1, inputting data into K blocks by K users respectively, and performing serial/parallel conversion in the K blocks respectively, wherein each user obtains M paths of parallel data;

step A2, multiplying M paths of parallel data obtained by each user in the step A1 by M paths of subcarriers respectively, and obtaining M paths of processed data by each user; the M paths of subcarriers are discrete data output by the M paths of code sequences through FFT;

step A3, performing parallel/serial conversion on the M paths of processed data obtained by each user in the step A2, and obtaining K paths of serial data by K users;

step A4, performing digital-to-analog conversion on the K paths of serial data obtained in the step A3 respectively to obtain converted K paths of analog signals;

step A5, respectively carrying out carrier modulation on the K paths of analog signals obtained in the step A4 to obtain modulated K paths of modulation signals;

step A6, respectively carrying out band-pass filtering on the K paths of modulation signals obtained in the step A5 to obtain K paths of signals subjected to band-pass filtering;

step A7, merging the K-path signals obtained in the step A6 after band pass filtering into one path, and transmitting the path to a channel;

the signal receiving method of the receiving end in the downlink of the system comprises the following steps:

step B1, receiving a modulation signal sent by a downlink transmitting end by using a receiving antenna, and performing band-pass filtering on the signal to obtain a path of signal after band-pass filtering;

b2, demodulating the path of signal after band-pass filtering obtained in the step B1 to obtain a path of demodulated signal;

b3, performing low-pass filtering on the demodulated signal obtained in the step B2 to obtain a low-pass filtered signal;

b4, performing analog-to-digital conversion on the low-pass filtered signal obtained in the step B3 to obtain a path of digital data;

b5, performing serial/parallel conversion on the path of digital data obtained in the step B4 to obtain M paths of parallel data;

b6, multiplying the M paths of parallel data obtained in the B5 by the M paths of subcarriers to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through IFFT;

b7, performing low-pass filtering on the M paths of processed data obtained in the B6 to obtain M paths of low-pass filtered data;

step B8, judging the M paths of low-pass filtered data obtained in the step B7, and outputting;

the M-way code sequence in the step A2 is the same as the M-way code sequence in the step B6;

the signal transmitting method of the transmitting terminal in the uplink of the system comprises the following steps:

step C1, performing serial/parallel conversion on the uplink data of the Kth user to obtain M paths of parallel data;

step C2, multiplying the M paths of parallel data obtained in the step C1 by the M paths of subcarriers respectively to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through FFT;

step C3, performing parallel/serial conversion on the M paths of processed data obtained in the step C2 respectively to obtain a path of serial signals;

step C4, performing digital-to-analog conversion on the path of serial signals obtained in the step C3 to obtain a path of analog signals;

step C5, carrying out carrier modulation on the one-path analog signal obtained in the step C4 to obtain one-path modulation signal;

step C6, performing band-pass filtering on the path of modulation signal obtained in the step C5 to obtain a path of signal subjected to band-pass filtering, and transmitting the signal to a channel;

the uplink signal receiving method of the system comprises the following steps:

step D1, receiving the modulation signal transmitted by the uplink transmitting end by adopting a receiving antenna, and carrying out band-pass filtering on the modulation signal to obtain a signal after band-pass filtering;

d2, demodulating the band-pass filtered signal obtained in the step D1 to obtain a path of demodulated signal;

d3, performing low-pass filtering on the demodulated signal obtained in the step D2 to obtain a low-pass filtered signal;

d4, performing analog-to-digital conversion on the low-pass filtered signal obtained in the step D3 to obtain a path of digital data;

d5, performing serial/parallel conversion on the path of digital data obtained in the step D4 to obtain M paths of parallel data;

d6, multiplying the M paths of parallel data obtained in the step D5 by the M paths of subcarriers to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through IFFT;

d7, performing low-pass filtering on the M paths of processed data obtained in the step D6 to obtain M paths of low-pass filtered data;

d8, judging the M paths of low-pass filtered data obtained in the step D7, and outputting;

the M-way code sequence in the step C2 is the same as the M-way code sequence in the step D6;

K. m is a positive integer.

In step a3, a path of serial signal obtained by each user can be divided into a real part and a virtual part for digital-to-analog conversion, carrier modulation and band-pass filtering, and then added together to form a path of band-pass filtered signal.

The principle is as follows: the Block multiplexing Multiple Access (BSMA) system of the invention provides a new Multiple Access system model, aiming at avoiding the defect that the CP is utilized to inhibit the multipath interference in the OFDM system, greatly improving the frequency band utilization rate and inhibiting the multipath interference.

The downlink is schematically shown in fig. 1, in which BS represents a base station, and users 1-K represent K User terminals, such as mobile phones. In downlink, the BS acts as the transmitter and uses T_xAnd (4) showing. User as receiving end, using R_xAnd (4) showing.

A transmitting end: when the transmitting end transmits the ith symbol, the signal processing process is as shown in fig. 2, the data transmitted to different users are processed in different blocks, and the data of K users are processed by Scrambler 1 to Scrambler K respectively. When data of different usersAfter the block outputs, digital-to-analog conversion is carried out in sequence, carrier modulation and band-pass filtering are respectively adopted, and finally the signals are combined together for transmission.

The specific structure of each block is the same, taking the K (K =1, 2.. K) block as an example, the signal processing procedure is as shown in fig. 3:is the data of the ith symbol of the kth user. After serial-to-parallel conversion (S/P), obtaining Refers to the data of the mth bit stream in the ith symbol of the kth user, where M =1,2, … M. Data of each bit stream andmultiply to obtainWherein,is a code sequenceResults after FFT.

Wherein the first data of the FFT outputAre not used.

The code sequences are different from user to user. The code sequence of user k isIn order to overcome the multiple access interference, a guard interval needs to be added between code sequences, the guard interval is recorded as alpha, and alpha is required to be larger than the maximum delay spread. It should be noted that the guard interval α is added between code sequences and is not added to the user's data, so that the effective transmission rate of the data is not reduced, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. Code sequence is defined as

Then the code sequence of user k +1 adjacent to user k isAs shown in formula (2):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(k\right)}\right\}}_{m=0}^M=\{X_0^{\left(k\right)},X_1^{\left(k\right)},X_2^{\left(k\right)},...,X_M^{\left(k\right)}\};$

receiving end: in downlink, a user acts as a receiving end, and the system architecture is shown in fig. 4. In fig. 4, r (t) is the signal received by user q, after bandpass filtering, the signal becomes η (t), and then the η (t) is compared with the signalMultiplying, low-pass filtering and A/D converting the signal to obtain beta_i. After serial-to-parallel conversion, each bit stream is compared withMultiplication.Andis a set of conjugate transform pairs, andis a code sequenceResults after performing FFT. The demodulated signalThe decision variable is obtained by low-pass filtering. And finally, recovering the useful signal after passing through the decision device.

Wherein: first data of FFT outputAre not used. ② the whole process does not consider the synchronization problem, i.e. the explanation of the system is carried out under the condition of complete synchronization.

The code sequences are different from user to user. The code sequence of user q isIn order to overcome the multiple access interference, a guard interval needs to be added between code sequences, which is marked as α, and α is required to be larger than the maximum delay spread. It should be noted that the guard interval α between code sequences does not reduce the effective transmission rate of data, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. The code sequence is defined as:

then the code sequence of user q +1 adjacent to user q isAs shown in formula (6):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(q\right)}\right\}}_{m=0}^M=\{X_0^{\left(q\right)},X_1^{\left(q\right)},X_2^{\left(q\right)},...,X_M^{\left(q\right)}\};$

the uplink is schematically illustrated in fig. 5: in the figure, BS represents a base station, and users 1-K represent K User terminals, such as mobile phones. In the uplink, User is used as the transmitting end and T is used_xRepresents; BS as receiving end, using R_xAnd (4) showing.

A transmitting end: when user k transmits the ith symbol, the signal processing procedure is as shown in fig. 6.

In the context of figure 6 of the drawings,is the data of the ith symbol of user k. After serial-to-parallel conversion (S/P), is easy to obtain Refers to the data of the mth bit stream in the ith symbol of user k, where M =1,2, … M. Data of each bit stream andmultiply to obtainWherein,is a code sequenceResults after FFT.

Wherein: first data of FFT outputAre not used.

The code sequences are different from user to user. The code sequence of user k isIn order to overcome multipath interference, a guard interval α needs to be added between code sequences, and α is required to be larger than the maximum delay spread. It should be noted that the guard interval α between code sequences does not reduce the effective transmission rate of data, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. The code sequence is defined as:

then the code sequence of user k +1 adjacent to user k isAs shown in formula (10):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>.</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>11</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(k\right)}\right\}}_{m=0}^M=\{X_0^{\left(k\right)},X_1^{\left(k\right)},X_2^{\left(k\right)},...,X_M^{\left(k\right)}\}---\left(12\right)$

receiving end: in uplink, the base station serves as a receiving end, and the system architecture thereof is shown in fig. 3. In fig. 3, r (t) is a signal received by the base station, after band-pass filtering, the signal becomes η (t), and then the η (t) is compared with the signalMultiplying, low-pass filtering and A/D converting the signal to obtain beta_i. After serial-to-parallel conversion, each bit stream is compared withMultiplication.Andis a set of conjugate transform pairs, andis a code sequenceResults after performing FFT. Will solveModulated signalThe decision variable is obtained by low-pass filtering. And finally, recovering the useful signal after passing through the decision device.

Wherein: first data of FFT outputAre not used. ② the whole process does not consider the synchronization problem, i.e. the explanation of the system is carried out under the condition of complete synchronization.

The code sequences are different from user to user. The code sequence of user q isIn order to overcome the multiple access interference, a guard interval needs to be added between code sequences, which is marked as α, and α is required to be larger than the maximum delay spread. It should be noted that the guard interval α between code sequences does not reduce the effective transmission rate of data, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. The code sequence is defined as:

then the code sequence of user q +1 adjacent to user q isAs shown in formula (14):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>15</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(q\right)}\right\}}_{m=0}^M=\{X_0^{\left(q\right)},X_1^{\left(q\right)},X_2^{\left(q\right)},...,X_M^{\left(q\right)}\}---\left(16\right)$

the BSMA system is theoretically practicable, but may have certain difficulties in some specific aspects if the BSMA system is put into practical engineering application. For example, the output of the FFT contains a complex exponential function. Therefore, in order to make the system have practical application value, the following description will be made with respect to specific embodiments thereof.

Downlink: a transmitting end: first, in the downlink, an embodiment of the BSMA transmitting end will be described, see fig. 9. In the context of figure 9 of the drawings,is the data of the ith symbol to be sent to user k. After serial-to-parallel conversion (S/P), is easy to obtain Refers to the data of the mth bit stream in the ith symbol of user k, where M =1,2, … M. Data of each bit stream andmultiply to obtainWherein,is a code sequenceResults after FFT. The result of the FFT output contains a complex exponential function,the transmission can be divided into a real part and an imaginary part, wherein the real part is called in-phase component and the imaginary part is called quadrature component. After D/A conversion, use A_c cos(2πf_ct) multiplied by the in-phase componentwith-A_c sin(2πf_ct) multiplied by the orthogonal componentAfter band pass filtering, the two signals are added together. Finally, the data of all users are added together for transmission.

Wherein the first data of the FFT outputAre not used.

The code sequences are different from user to user. The code sequence of user k isIn order to overcome multiple access interference, a guard interval α needs to be added between code sequences, and α is required to be larger than the maximum delay spread. It should be noted that the guard interval α between code sequences does not reduce the effective transmission rate of data, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. The code sequence is defined as:

then the code sequence of user k +1 adjacent to user k isAs shown in formula (23):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>24</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(k\right)}\right\}}_{m=0}^M=\{X_0^{\left(k\right)},X_1^{\left(k\right)},X_2^{\left(k\right)},...,X_M^{\left(k\right)}\}---\left(25\right)$

receiving end: in the downlink, a specific trial scheme of the receiving end of the BSMA system is shown in fig. 10. At the transmitting end, due to the existence of the complex exponential function, the signal is divided into a real part and an imaginary part. Transmitting the real part of the signal by using a cosine function; the imaginary part of the signal is transmitted with a sinusoidal function. Then at the receiving end, the received signal also needs to be divided into two parts. Will signal withMultiplying and then low-pass filtering to obtain beta_I(t); will signal withMultiplying and then low-pass filtering to obtain beta_Q(t); then, β_Q(t) is multiplied by-j and then by β_I(t) are added to obtain beta (t), and after D/A conversion, beta [ n ] is obtained]. After serial-to-parallel conversion, each bit stream is compared withMultiplication.Andis a set of conjugate transform pairsIs a code sequenceResults after performing FFT. The demodulated signalThe decision variable is obtained by low-pass filtering. And finally, recovering the useful signal after passing through the decision device.

Wherein: first data of FFT outputAre not used. ② the whole process does not consider the synchronization problem, i.e. the explanation of the system is carried out under the condition of complete synchronization.

In addition, at the receiving end of BSMA in downlink, the two blocks of FFT and conjugate transform can be replaced with one IFFT block, see fig. 11.

In fig. 11, it can be found that in the demodulation of the signal, the conjugate transformation is no longer needed, and the FFT module is replaced with the IFFT module. In the figureAs shown in the following formula:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>26</mn> <mo>)</mo> </mrow> </mrow> </math>

the code sequences are different from user to user. The code sequence of user q isIn order to overcome the multiple access interference, a guard interval needs to be added between code sequences, which is marked as α, and α is required to be larger than the maximum delay spread. It should be noted that the guard interval α between code sequences does not reduce the effective transmission rate of data, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. The code sequence is defined as:

then the code sequence of user q +1 adjacent to user q isAs shown in formula (28):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>q</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>29</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(q\right)}\right\}}_{m=0}^M=\{X_0^{\left(q\right)},X_1^{\left(q\right)},X_2^{\left(q\right)},...,X_M^{\left(q\right)}\}---\left(30\right)$

and uplink: a transmitting end: when user k transmits the ith symbol, the system architecture is as shown in fig. 12.

In the context of figure 12 of the drawings,is the data of the ith symbol of the kth user. After serial-to-parallel conversion (S/P), is easy to obtain Refers to the data of the mth bit stream in the ith symbol of the kth user, where M =1,2, … M. Data of each bit stream andmultiplication by multiplicationCan obtainWherein,is a code sequenceResults after FFT.

It should be noted that the first data of the FFT outputAre not used.

The code sequences are different from user to user. The code sequence of user k isIn order to overcome the multipath interference, a guard interval needs to be added between code sequences, and the guard interval is required to be larger than the maximum delay spread. It should be noted that the guard interval α between code sequences does not reduce the effective transmission rate of data, which is different from the guard interval in the OFDM system. Below, in order toThe description is for the study subject. The code sequence is defined as:

then the code sequence of user k +1 adjacent to user k isAs shown in formula (32):

FFT processing is performed on the code sequence of the user, and the result is as follows:

<math> <mrow> <msubsup> <mi>X</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mi>M</mi> </munderover> <msubsup> <mi>x</mi> <mi>n</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;</mi> </mrow> <mi>M</mi> </mfrac> <mi>mn</mi> </mrow> </msup> <mo>,</mo> <mi>m</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mi>M</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>33</mn> <mo>)</mo> </mrow> </mrow> </math>

the result of the FFT output is:

${\left\{X_m^{\left(k\right)}\right\}}_{m=0}^M=\{X_0^{\left(k\right)},X_1^{\left(k\right)},X_2^{\left(k\right)},...,X_M^{\left(k\right)}\}---\left(34\right)$

receiving end: next, a method of implementing the BSMA receiving side will be described, as shown in fig. 13. At the transmitting end, due to the existence of the complex exponential function, the signal is divided into a real part and an imaginary part. Transmitting the in-phase component of the signal with a cosine function; the quadrature components of the signal are transmitted with a sinusoidal function. Then at the receiving end, the received signal also needs to be divided into two parts. Will signal withMultiplying and then low-pass filtering to obtain beta_I(t); will signal withMultiplying and then low-pass filtering to obtain beta_Q(t); then, β_Q(t) is multiplied by-j and then by β_I(t) are added to obtain beta (t), and after D/A conversion, beta [ n ] is obtained]. After serial-to-parallel conversion, each bit stream is compared withMultiplication.Andis a set of conjugate transform pairs, andis a code sequenceResults after performing FFT. The demodulated signalThe decision variable is obtained by low-pass filtering. And finally, recovering the useful signal after passing through the decision device.

Wherein: first data of FFT outputAre not used. ② the whole process does not consider the synchronization problem, i.e. the explanation of the system is carried out under the condition of complete synchronization.

In addition, at the receiving end of BSMA in downlink, the two modules of FFT and conjugate transform can be replaced by one IFFT module, please refer to fig. 11 for details.

The performance of the invention was verified by simulation experiments as follows:

for the performance of the BSMA system, two aspects of the frequency band utilization rate and the anti-interference performance are mainly explained.

1. Frequency band utilization rate:

the band utilization of an OFDM system is defined as follows:

in the above formula, T_sIs the symbol time, T_CPThe time of the cyclic prefix. In an OFDM system, Q =4, if T_s=16T_CP. Then it is determined that,

η_OFDM≈1.88(bit/s/Hz) (18)

the band utilization of a BSMA system is defined as follows:

in the above formula, T_bIs the bit duration. When the maximum multipath delay is extended to 40 bits, α =40, and if the length M of the code sequence is 2048:

η_BSMA≈48(bit/s/Hz) (20)

wherein the length of the M-code sequence. When the value of M is large, the band utilization of BSMA is about M/α.

2. Noise immunity performance:

the BSMA system has good inhibition effect on Gaussian white noise, and the longer the FFT length is, the stronger the inhibition capability on noise is. The signal-to-noise ratio is expressed as follows:

<math> <mrow> <mi>&gamma;</mi> <mo>=</mo> <mfrac> <msub> <mi>E</mi> <mi>b</mi> </msub> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>=</mo> <mfrac> <mrow> <msubsup> <mi>A</mi> <mi>c</mi> <mn>2</mn> </msubsup> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mrow> <mn>2</mn> <msub> <mi>MN</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>21</mn> <mo>)</mo> </mrow> </mrow> </math>

the variation curve of the bit error rate with the signal-to-noise ratio is shown in fig. 8: in fig. 8, the abscissa represents the signal-to-noise ratio; the ordinate represents the bit error rate. The frequency bandwidth is 8MHz, the number of users is 1, a 6-tap typical urban (6-tap typical urban, 6-TU) channel model is adopted, and specific parameters are shown in table 1.

TABLE 1

The performance of the system of the invention is demonstrated by simulation tests: the invention overcomes the defect that the CP is used for restraining the multipath interference in the OFDM system, greatly improves the utilization rate of the frequency band and can restrain the multipath interference at the same time.

Claims (2)

1. The block mixed multiple access method is realized based on OFDM system, which is characterized in that:

the signal transmitting method of the transmitting terminal in the downlink of the system comprises the following steps:

step A1, inputting data into K blocks by K users respectively, and performing serial/parallel conversion in the K blocks respectively, wherein each user obtains M paths of parallel data;

step A2, multiplying M paths of parallel data obtained by each user in the step A1 by M paths of subcarriers respectively, and obtaining M paths of processed data by each user; the M paths of subcarriers are discrete data output by the M paths of code sequences through FFT; a guard interval alpha is added into the M paths of sequence codes, and the guard interval alpha is larger than the maximum delay spread;

step A3, performing parallel/serial conversion on the M paths of processed data obtained by each user in the step A2, and obtaining K paths of serial data by K users;

step A4, performing digital-to-analog conversion on the K paths of serial data obtained in the step A3 respectively to obtain converted K paths of analog signals;

step A5, respectively carrying out carrier modulation on the K paths of analog signals obtained in the step A4 to obtain modulated K paths of modulation signals;

step A6, respectively carrying out band-pass filtering on the K paths of modulation signals obtained in the step A5 to obtain K paths of signals subjected to band-pass filtering;

step A7, merging the K-path signals obtained in the step A6 after band pass filtering into one path, and transmitting the path to a channel;

the signal receiving method of the receiving end in the downlink of the system comprises the following steps:

step B1, receiving a modulation signal sent by a downlink transmitting end by using a receiving antenna, and performing band-pass filtering on the signal to obtain a path of signal after band-pass filtering;

b2, demodulating the path of signal after band-pass filtering obtained in the step B1 to obtain a path of demodulated signal;

b3, performing low-pass filtering on the demodulated signal obtained in the step B2 to obtain a low-pass filtered signal;

b4, performing analog-to-digital conversion on the low-pass filtered signal obtained in the step B3 to obtain a path of digital data;

b5, performing serial/parallel conversion on the path of digital data obtained in the step B4 to obtain M paths of parallel data;

b6, multiplying the M paths of parallel data obtained in the B5 by the M paths of subcarriers to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through IFFT; a guard interval alpha is added into the M paths of sequence codes, and the guard interval alpha is larger than the maximum delay spread;

b7, performing low-pass filtering on the M paths of processed data obtained in the B6 to obtain M paths of low-pass filtered data;

step B8, judging the M paths of low-pass filtered data obtained in the step B7, and outputting;

the M-way code sequence in the step A2 is the same as the M-way code sequence in the step B6;

the signal transmitting method of the transmitting terminal in the uplink of the system comprises the following steps:

step C1, performing serial/parallel conversion on the uplink data of the Kth user to obtain M paths of parallel data;

step C2, multiplying the M paths of parallel data obtained in the step C1 by the M paths of subcarriers respectively to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through FFT; a guard interval alpha is added into the M paths of sequence codes, and the guard interval alpha is larger than the maximum delay spread;

step C3, performing parallel/serial conversion on the M paths of processed data obtained in the step C2 respectively to obtain a path of serial signals;

step C4, performing digital-to-analog conversion on the path of serial signals obtained in the step C3 to obtain a path of analog signals;

step C5, carrying out carrier modulation on the one-path analog signal obtained in the step C4 to obtain one-path modulation signal;

step C6, performing band-pass filtering on the path of modulation signal obtained in the step C5 to obtain a path of signal subjected to band-pass filtering, and transmitting the signal to a channel;

the uplink signal receiving method of the system comprises the following steps:

step D1, receiving the modulation signal transmitted by the uplink transmitting end by adopting a receiving antenna, and carrying out band-pass filtering on the modulation signal to obtain a signal after band-pass filtering;

d2, demodulating the band-pass filtered signal obtained in the step D1 to obtain a path of demodulated signal;

d3, performing low-pass filtering on the demodulated signal obtained in the step D2 to obtain a low-pass filtered signal;

d4, performing analog-to-digital conversion on the low-pass filtered signal obtained in the step D3 to obtain a path of digital data;

d5, performing serial/parallel conversion on the path of digital data obtained in the step D4 to obtain M paths of parallel data;

d6, multiplying the M paths of parallel data obtained in the step D5 by the M paths of subcarriers to obtain M paths of processed data; the M paths of subcarriers are discrete data output by the M paths of code sequences through IFFT; a guard interval alpha is added into the M paths of sequence codes, and the guard interval alpha is larger than the maximum delay spread;

d7, performing low-pass filtering on the M paths of processed data obtained in the step D6 to obtain M paths of low-pass filtered data;

d8, judging the M paths of low-pass filtered data obtained in the step D7, and outputting;

the M-way code sequence in the step C2 is the same as the M-way code sequence in the step D6;

K. m is a positive integer.

2. The block hybrid multiple access method according to claim 1, wherein the one-path serial signal obtained by each user in step a3 can be divided into real and virtual parts for digital-to-analog conversion, carrier modulation and band-pass filtering, and then added together to form one-path band-pass filtered signal.