CN102780510B - Block mixing multiple access method - Google Patents

Abstract

The block hybrid multiple access method relates to a multiple access method, which aims to overcome the shortcoming of using CP to suppress multipath interference in an OFDM system. Downlink: Transmitter: Process the data sent to different users in different blocks, and modulate and output the data of different users after outputting from the block. Receiver: After the received signal is demodulated, it is inversely transformed with the transmitter and then judged and output. Uplink: Transmitter: The data of each bit stream of the user is multiplied by the code sequence and then modulated and output. Receiving end: The base station demodulates the received signal and then performs inverse transformation processing with the transmitting end to make a judgment output. The invention proposes a new multi-access system model, which overcomes the shortcoming of using CP to suppress multi-path interference in the OFDM system, and can suppress multi-path interference while greatly improving frequency band utilization. The invention is suitable for wireless communication.

Description

Block Hybrid Multiple Access Method

technical field

The invention relates to a multiple access method.

Background technique

In an Orthogonal Frequency Division Multiplexing (OFDM) system, to overcome multipath interference, it is necessary to add a cyclic prefix (Cyclic Prefix, CP) to the transmitted symbols, and the length of the CP is also strictly limited , if the length of the CP is less than the maximum delay, it will cause very serious inter-symbol interference (Inter-Symbol Interference, ISI) and inter-carrier interference (Inter-Carrier Interference, ICI). Due to the addition of the CP, the utilization rate of the frequency band will be reduced.

Contents of the invention

The present invention aims to overcome the shortcoming of using CP to suppress multipath interference in the OFDM system, thereby providing a block hybrid multiple access method.

block hybrid multiple access method, which is traditionally implemented based on the OFDM system,

The signal transmission method of the transmitting end in the downlink of the system:

Step A1. K users input data into K blocks respectively, and perform serial/parallel conversion in K blocks respectively, and each user obtains M channels of parallel data;

Step A2. Multiply the M parallel data obtained by each user in step A1 by the M subcarriers respectively, and each user obtains M processed data; the M subcarriers are the discrete output of the M code sequence through FFT data;

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

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

Step A5, respectively performing carrier modulation on the K-channel analog signals obtained in step A4, to obtain modulated K-channel modulation signals;

Step A6, performing band-pass filtering on the K-channel modulation signals obtained in step A5, respectively, to obtain K-channel band-pass filtered signals;

Step A7, combining the K-channel band-pass filtered signals obtained in step A6 into one channel, and transmitting to the channel;

The signal receiving method of the receiving end in the downlink of the system:

Step B1, using the receiving antenna to receive the modulated signal sent by the downlink transmitter, and performing band-pass filtering on the signal to obtain a band-pass filtered signal;

Step B2, demodulating the one-way band-pass filtered signal obtained in step B1 to obtain one-way demodulated signal;

Step B3, performing low-pass filtering on the demodulated signal obtained in step B2 to obtain a low-pass filtered signal;

Step B4, performing analog-to-digital conversion on the one-way low-pass filtered signal obtained in step B3, to obtain one-way digital data;

Step B5, performing serial/parallel conversion on one channel of digital data obtained in step B4 to obtain M channels of parallel data;

Step B6, multiplying the M-path parallel data obtained in step B5 with the M-path subcarriers to obtain the M-path processed data; the M-path sub-carriers are the discrete data output by the M-path code sequences through IFFT;

Step B7, performing low-pass filtering on the M channels of processed data obtained in step B6 to obtain M channels of low-pass filtered data;

Step B8, judge the data obtained in step B7 after the low-pass filtering of M channels, and output;

The M road code sequence is identical with the M road code sequence in the step B6 among the step A2;

The signal transmission method of the transmitting end in the uplink of the system:

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

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

Step C3, performing parallel/serial conversion on the M channels of processed data obtained in step C2, respectively, to obtain one channel of serial signals;

Step C4, performing digital/analog conversion on one serial signal obtained in step C3 to obtain one analog signal;

Step C5, performing carrier modulation on one analog signal obtained in step C4 to obtain one modulated signal;

Step C6, performing band-pass filtering on one modulation signal obtained in step C5, obtaining one band-pass filtered signal, and transmitting it to the channel;

The signal reception method of the uplink of the system:

Step D1, using the receiving antenna to receive the modulated signal transmitted by the uplink transmitter, and performing band-pass filtering on the modulated signal to obtain a band-pass filtered signal;

Step D2, demodulating the band-pass filtered signal obtained in step D1 to obtain a demodulated signal;

Step D3, performing low-pass filtering on the demodulated signal obtained in step D2 to obtain a low-pass filtered signal;

Step D4, performing analog-to-digital conversion on the one-way low-pass filtered signal obtained in step D3, to obtain one-way digital data;

Step D5, performing serial/parallel conversion on one channel of digital data obtained in step D4 to obtain M channels of parallel data;

Step D6, multiplying the M parallel data obtained in step D5 by the M subcarriers to obtain the M processed data; the M subcarriers are discrete data output by the M code sequences through IFFT;

Step D7, performing low-pass filtering on the M channels of processed data obtained in step D6 to obtain M channels of low-pass filtered data;

Step D8, judging the data obtained in step D7 after the low-pass filtering of M paths, and outputting it;

In the step C2, the M code sequence is identical to the M code sequence in the step D6;

K and M are both positive integers.

A serial signal obtained by each user in step A3 can be divided into a real part and an imaginary part for digital/analog conversion, carrier modulation and band-pass filtering respectively, and then added together to form a band-pass filtered signal.

The invention proposes a new data transmission mode of a multiple access system, which overcomes the shortcoming of suppressing multipath interference by using CP in an OFDM system, and can suppress multipath interference while greatly improving frequency band utilization.

Description of drawings

Fig. 1 is a schematic diagram of the principle 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 schematic diagram of the signal processing flow of the kth block in the downlink; Fig. 4 is a schematic diagram of the signal processing 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 of the present invention; Fig. 7 is a schematic diagram of the receiving end in the uplink of the present invention Schematic diagram of the signal processing flow; FIG. 8 is a schematic diagram of the simulation of the system bit error rate in the specific embodiment one; FIG. A schematic diagram of the signal processing flow at the receiving end corresponding to the way the imaginary part processes the signal separately; FIG. 11 is a schematic diagram of the simplified form of the FFT module at the receiving end in the downlink; FIG. 12 is a schematic diagram of when user k sends the i-th symbol, a schematic diagram of the signal processing flow at the sending end in the uplink; FIG. 13 is a schematic diagram of the signal processing flow at the receiving end in the uplink when user k sends the i-th symbol described in Embodiment 1.

Detailed ways

Specific embodiments 1. This specific embodiment is described in conjunction with FIG. 1 to FIG. 13 , a block hybrid multiple access method, which is traditionally implemented based on the OFDM system,

The signal transmission method of the transmitting end in the downlink of the system:

Step A1. K users input data into K blocks respectively, and perform serial/parallel conversion in K blocks respectively, and each user obtains M channels of parallel data;

Step A2. Multiply the M parallel data obtained by each user in step A1 by the M subcarriers respectively, and each user obtains M processed data; the M subcarriers are the discrete output of the M code sequence through FFT data;

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

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

Step A5, respectively performing carrier modulation on the K-channel analog signals obtained in step A4, to obtain modulated K-channel modulation signals;

Step A6, performing band-pass filtering on the K-channel modulation signals obtained in step A5, respectively, to obtain K-channel band-pass filtered signals;

Step A7, combining the K-channel band-pass filtered signals obtained in step A6 into one channel, and transmitting to the channel;

The signal receiving method of the receiving end in the downlink of the system:

Step B1, using the receiving antenna to receive the modulated signal sent by the downlink transmitter, and performing band-pass filtering on the signal to obtain a band-pass filtered signal;

Step B2, demodulating the one-way band-pass filtered signal obtained in step B1 to obtain one-way demodulated signal;

Step B3, performing low-pass filtering on the demodulated signal obtained in step B2 to obtain a low-pass filtered signal;

Step B4, performing analog-to-digital conversion on the one-way low-pass filtered signal obtained in step B3, to obtain one-way digital data;

Step B5, performing serial/parallel conversion on one channel of digital data obtained in step B4 to obtain M channels of parallel data;

Step B6, multiplying the M-path parallel data obtained in step B5 with the M-path subcarriers to obtain the M-path processed data; the M-path sub-carriers are the discrete data output by the M-path code sequences through IFFT;

Step B7, performing low-pass filtering on the M channels of processed data obtained in step B6 to obtain M channels of low-pass filtered data;

Step B8, judge the data obtained in step B7 after the low-pass filtering of M channels, and output;

The M road code sequence is identical with the M road code sequence in the step B6 among the step A2;

The signal transmission method of the transmitting end in the uplink of the system:

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

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

Step C3, performing parallel/serial conversion on the M channels of processed data obtained in step C2, respectively, to obtain one channel of serial signals;

Step C4, performing digital/analog conversion on one serial signal obtained in step C3 to obtain one analog signal;

Step C5, performing carrier modulation on one analog signal obtained in step C4 to obtain one modulated signal;

Step C6, performing band-pass filtering on one modulation signal obtained in step C5, obtaining one band-pass filtered signal, and transmitting it to the channel;

The signal reception method of the uplink of the system:

Step D1, using the receiving antenna to receive the modulated signal transmitted by the uplink transmitter, and performing band-pass filtering on the modulated signal to obtain a band-pass filtered signal;

Step D2, demodulating the band-pass filtered signal obtained in step D1 to obtain a demodulated signal;

Step D3, performing low-pass filtering on the demodulated signal obtained in step D2 to obtain a low-pass filtered signal;

Step D4, performing analog-to-digital conversion on the one-way low-pass filtered signal obtained in step D3, to obtain one-way digital data;

Step D5, performing serial/parallel conversion on one channel of digital data obtained in step D4 to obtain M channels of parallel data;

Step D6, multiplying the M parallel data obtained in step D5 by the M subcarriers to obtain the M processed data; the M subcarriers are discrete data output by the M code sequences through IFFT;

Step D7, performing low-pass filtering on the M channels of processed data obtained in step D6 to obtain M channels of low-pass filtered data;

Step D8, judging the data obtained in step D7 after the low-pass filtering of M paths, and outputting it;

In the step C2, the M code sequence is identical to the M code sequence in the step D6;

K and M are both positive integers.

A serial signal obtained by each user in step A3 can be divided into a real part and an imaginary part for digital/analog conversion, carrier modulation and band-pass filtering respectively, and then added together to form a band-pass filtered signal.

Principle: The Block Scrambling Multiple Access (BSMA) system of the present invention proposes a new multiple access system model, which aims to avoid the disadvantage of using CP to suppress multipath interference in the OFDM system, greatly Suppress multipath interference while improving frequency band utilization.

The schematic diagram of the downlink is shown in Fig. 1, in which BS represents a base station, and User1~User K represent K user terminals, such as mobile phones. In the downlink, the BS acts as the sending end, denoted _by Tx. User is the receiving end, represented by R _x .

Transmitter: When the transmitter sends the i-th symbol, its signal processing process is shown in Figure 2. The data sent to different users are processed in different blocks, and Scrambler 1~Scrambler K respectively process K users The data. When data from different users After output from the block, digital-to-analog conversion is carried out sequentially, carrier modulation is used respectively, band-pass filtering is used, and finally combined for transmission.

The specific structure of each block is the same, taking the kth (k=1,2,...K) block as an example, its signal processing process is shown in Figure 3: is the data of the i-th symbol of the k-th user. After serial-to-parallel conversion (S/P), get refers to the data of the m-th bit stream in the i-th symbol of the k-th user, where m=1,2,...M. Each bit stream data with multiplied, you get in, is the code sequence The result after FFT.

Among them, the first data output by FFT Not used.

Different users have different code sequences. The code sequence of user k is In order to overcome multiple access interference, it is necessary to add a guard interval between the code sequences, denote the guard interval as α, and require α to be greater than the maximum delay extension. It should be noted that the guard interval α is added between the code sequences but not in the user data, so the effective transmission rate of data is not reduced, which is different from the guard interval in the OFDM system. Below, with Describe the research object. The code sequence is defined as

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

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; ;</span>$

Receiver: In the downlink, the user acts as the receiver, and its system architecture is shown in Figure 4. In Figure 4, r(t) is the signal received by user q. After bandpass filtering, the signal becomes η(t), and then combined with Multiply, and then perform low-pass filtering and analog-to-digital conversion on the signal in turn to obtain β _i . After serial-to-parallel conversion, each bit stream is compared with multiplied. and is a set of conjugate transformation pairs, and is the code sequence The result after performing the FFT. The demodulated signal will be By performing low-pass filtering, the decision variable can be obtained. Finally, after passing through the decision device, the useful signal can be recovered.

Among them: ①The first data output by FFT Not used. ② The synchronization problem is not considered in the whole process, that is, the description of the system is carried out under the condition of complete synchronization.

Different users have different code sequences. The code sequence of user q is In order to overcome multiple access interference, it is necessary to add a guard interval between code sequences, which is denoted as α, and α is required to be greater than the maximum delay extension. 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, with Describe the research object. The code sequence is defined as:

Then the code sequence of user q+1 adjacent to user q is As shown in formula (6):

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; ;</span>$

The schematic diagram of the uplink is shown in FIG. 5 : in the figure, BS represents a base station, and User1~User K represent K user terminals, such as mobile phones. In the uplink, the User acts as the sending end, represented by T _x ; the BS acts as the receiving end, represented by R _x .

Transmitter: When user k sends the i-th symbol, its signal processing process is shown in Figure 6.

In Figure 6, is the data of the i-th symbol of user k. After serial-to-parallel conversion (S/P), it is easy to obtain refers to the data of the m-th bit stream in the i-th symbol of user k, where m=1,2,...M. Each bit stream data with multiplied, you get in, is the code sequence The result after FFT.

Among them: the first data output by FFT Not used.

Different users have different code sequences. The code sequence of user k is In order to overcome multipath interference, a guard interval α needs to be added between code sequences, and α is required to be greater than the maximum delay extension. 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, with Describe the research object. The code sequence is defined as:

Then the code sequence of user k+1 adjacent to user k is As shown in formula (10):

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Receiver: In the uplink, the base station acts as the receiver, and its system architecture is shown in Figure 3. In Fig. 3, r(t) is the signal received by the base station, after band-pass filtering, the signal becomes η(t), and then with Multiply, and then perform low-pass filtering and analog-to-digital conversion on the signal in turn to obtain β _i . After serial-to-parallel conversion, each bit stream is compared with multiplied. and is a set of conjugate transformation pairs, and is the code sequence The result after performing the FFT. The demodulated signal will be By performing low-pass filtering, the decision variable can be obtained. Finally, after passing through the decision device, the useful signal can be recovered.

Among them: ①The first data output by FFT Not used. ② The synchronization problem is not considered in the whole process, that is, the description of the system is carried out under the condition of complete synchronization.

Different users have different code sequences. The code sequence of user q is In order to overcome multiple access interference, it is necessary to add a guard interval between code sequences, which is denoted as α, and α is required to be greater than the maximum delay extension. 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, with Describe the research object. The code sequence is defined as:

Then the code sequence of user q+1 adjacent to user q is As shown in formula (14):

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 15</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

The BSMA system is theoretically implementable, but if it is put into practical engineering application, there may be certain difficulties in some specific links. For example, the output of FFT contains a complex exponential function. Therefore, in order to make the system have practical application value, the following description is specially made for its specific implementation.

Downlink: Transmitter: First, in the downlink, the implementation of the BSMA transmitter is described, see FIG. 9 . In Figure 9, is the data of the ith symbol to be sent to user k. After serial-to-parallel conversion (S/P), it is easy to obtain refers to the data of the m-th bit stream in the i-th symbol of user k, where m=1,2,...M. Each bit stream data with multiplied, you get in, is the code sequence The result after FFT. The result of the FFT output contains a complex exponential function, It can be divided into real part and imaginary part for transmission respectively, the real part is called the in-phase component, and the imaginary part is called the quadrature component. After digital-to-analog conversion, multiply the in-phase component by A _c cos(2πf _c t) Multiply the quadrature component by -A _c sin(2πf _c t) After bandpass filtering, the two signals are added together. Finally, all users' data is added together for transmission.

Among them, the first data output by FFT Not used.

Different users have different code sequences. The code sequence of user k is In order to overcome multiple access interference, it is necessary to add a guard interval α between the code sequences, requiring α to be greater than the maximum delay extension. 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, with Describe the research object. The code sequence is defined as:

Then the code sequence of user k+1 adjacent to user k is As shown in formula (23):

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; four</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 25</span>}<span\; class="notranslate">\; )</span>$

Receiving end: in the downlink, the specific trial scheme of the receiving end of the BSMA system is shown in Figure 10 . At the sending end, due to the existence of complex exponential function, the signal is divided into real part and imaginary part. The real part of the signal is transmitted with the cosine function; the imaginary part of the signal is transmitted with the sine function. Then at the receiving end, it is also necessary to divide the received signal into two parts. Combine the signal with Multiplied together, and then after low-pass filtering, β _I (t) can be obtained; the signal and β _Q (t) can be obtained after low-pass filtering; then, β _Q (t) is multiplied by -j, and then added to β _I (t) to obtain β (t). After number conversion, β[n] is obtained. After serial-to-parallel conversion, each bit stream is compared with multiplied. and is a set of conjugate transformation pairs and is the code sequence The result after performing the FFT. The demodulated signal will be By performing low-pass filtering, the decision variable can be obtained. Finally, after passing through the decision device, the useful signal can be recovered.

Among them: ①The first data output by FFT Not used. ② The synchronization problem is not considered in the whole process, that is, the description of the system is carried out under the condition of complete synchronization.

In addition, at the receiving end of BSMA in the downlink, the two modules of FFT and conjugate transformation can be replaced by one IFFT module, as shown in Fig. 11 .

In Fig. 11, it can be found that in the demodulation of the signal, the link of conjugate transformation is no longer needed, and the module of FFT is replaced by the module of IFFT. in the picture As shown in the following formula:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 26</span>}<span\; class="notranslate">\; )</span>$

Different users have different code sequences. The code sequence of user q is In order to overcome multiple access interference, it is necessary to add a guard interval between code sequences, which is denoted as α, and α is required to be greater than the maximum delay extension. 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, with Describe the research object. The code sequence is defined as:

Then the code sequence of user q+1 adjacent to user q is As shown in formula (28):

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 29</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 30</span>}<span\; class="notranslate">\; )</span>$

Uplink: Transmitter: When user k sends the i-th symbol, its system architecture is shown in Figure 12.

In Figure 12, is the data of the I-th symbol of the k-th user. After serial-to-parallel conversion (S/P), it is easy to obtain refers to the data of the m-th bit stream in the i-th symbol of the k-th user, where m=1,2,...M. Each bit stream data with multiplied, you get in, is the code sequence The result after FFT.

It should be noted that the first data output by FFT Not used.

Different users have different code sequences. The code sequence of user k is In order to overcome multipath interference, a guard interval needs to be added between the code sequences, and the guard interval is required to be larger than the maximum delay extension. 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, with Describe the research object. The code sequence is defined as:

Then the code sequence of user k+1 adjacent to user k is As shown in formula (32):

Perform FFT processing on the user's code sequence, the result is as follows:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 33</span>}<span\; class="notranslate">\; )</span>$

The result of the FFT output is:

${<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span>}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 34</span>}<span\; class="notranslate">\; )</span>$

Receiving end: Next, the implementation method of the BSMA receiving end will be described, as shown in FIG. 13 . At the sending end, due to the existence of complex exponential function, the signal is divided into real part and imaginary part. Use the cosine function to transmit the in-phase component of the signal; use the sine function to transmit the quadrature component of the signal. Then at the receiving end, it is also necessary to divide the received signal into two parts. Combine the signal with Multiplied together, and then after low-pass filtering, β _I (t) can be obtained; the signal and β _Q (t) can be obtained after low-pass filtering; then, β _Q (t) is multiplied by -j, and then added to β _I (t) to obtain β (t). After number conversion, β[n] is obtained. After serial-to-parallel conversion, each bit stream is compared with multiplied. and is a set of conjugate transformation pairs, and is the code sequence The result after performing the FFT. The demodulated signal will be By performing low-pass filtering, the decision variable can be obtained. Finally, after passing through the decision device, the useful signal can be recovered.

Among them: ①The first data output by FFT Not used. ② The synchronization problem is not considered in the whole process, that is, the description of the system is carried out under the condition of complete synchronization.

In addition, at the receiving end of the BSMA in the downlink, the two modules of FFT and conjugate transformation can be replaced by one IFFT module, see Figure 11 for details.

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

As for the performance of the BSMA system, two aspects, the frequency band utilization rate and the anti-jamming performance, are mainly described.

1. Band utilization:

The frequency band utilization of OFDM system is defined as follows:

In the above formula, T _s is the symbol time, and T _CP is the time of the cyclic prefix. In OFDM system, Q=4, if T _s =16T _CP . So,

η _OFDM ≈1.88(bit/s/Hz) (18)

The frequency band utilization ratio of BSMA system is defined as follows:

In the above formula, T _b is the bit duration. When the maximum multipath delay is extended to 40 bits, α=40, if the length of the code sequence M=2048, then:

η _BSMA ≈48(bit/s/Hz) (20)

Among them, the length of the M code sequence. When the value of M is large, the frequency band utilization ratio of BSMA is about M/α.

2. Anti-noise performance:

The BSMA system also has a good suppression effect on Gaussian white noise. The longer the length of FFT, the stronger the suppression ability to noise. The signal-to-noise ratio is expressed as follows:

$\mathrm{<span\; class="notranslate">\; \&gamma;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; MN</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; )</span>$

The change curve of the bit error rate with the signal-to-noise ratio is shown in Figure 8: In Figure 8, the abscissa represents the signal-to-noise ratio; the vertical axis represents the bit error rate. The frequency bandwidth is 8MHz, the number of users is 1, and a 6-tap typical urban (6-TU) channel model is adopted. For specific parameters, please refer to Table 1.

Table 1

The performance of the system of the present invention is proved by a simulation test: the present invention overcomes the shortcoming of using CP to suppress multipath interference in an OFDM system, and can suppress multipath interference while greatly improving frequency band utilization.

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.