CN107889124B - Flood monitoring data transmission method based on non-orthogonal multiple access - Google Patents

Abstract

The invention discloses a flood monitoring data transmission method based on non-orthogonal multiple access. In a water level monitoring system, there are multiple water level monitoring points in the same river, and the distance from each monitoring point to a base station is different. After estimating the channel conditions, grouping is performed, and the frequency domain of the multiple access channel is divided into multiple orthogonal sub-channels, each of which is shared by at least two monitoring points, and non-orthogonal transmission is used between them. The base station allocates power to monitoring points on each sub-channel according to a certain power allocation algorithm, and the receivers of each monitoring point complete message decoding through serial interference cancellation technology. The solution provided by the implementation of the present invention does not affect the monitoring quality of the water level system, and at the same time creatively solves the problem of insufficient frequency spectrum resources during floods.

Description

A flood monitoring data transmission method based on non-orthogonal multiple access

technical field

The invention relates to the technical field of flood disaster emergency communication, in particular to a flood monitoring data transmission method based on non-orthogonal multiple access.

Background technique

Due to the rapid development of wireless communications, the shortage of spectrum resources has always been the bottleneck for the improvement of data rate and service quality. It is imperative to find a mobile technology that can not only meet user experience requirements but also improve spectrum efficiency. Multiple access technology came into being. The multiple access technologies used in the traditional wireless communication system model include time division multiple access, code division multiple access, frequency division multiple access, etc. These technologies divide the dimension of the signal space into orthogonal ones according to the time axis, code word axis and frequency axis. user. The non-orthogonal multiple access technology breaks the confinement of the orthogonal multiple access technology, and uses the channel difference between users to realize the same frequency and simultaneous data transmission. Non-orthogonal multiple access allocates different powers to users through a certain power allocation algorithm at the transmitting end, and uses superposition coding technology to actively introduce interference information.

When the superposition code is used for data transmission, the serial interference cancellation technology is used at the receiving end to demodulate the superimposed signals of multiple users in turn, and the interference of the demodulated signals to the subsequent users is eliminated in turn. Therefore, the decoding order of users with different channel conditions is also different. Different. Compared with the orthogonal multiple access technology, although the receiver complexity in the non-orthogonal multiple access system needs to be improved, higher spectral efficiency and system capacity are obtained.

In the event of a flood disaster, there is a shortage of spectrum resources in the existing technology. When a flood disaster occurs, a large number of users suddenly access the base station and occupy a large amount of spectrum resources, which seriously affects the flood control alarm and monitoring data transmission of key river monitoring sites. The existing data method adopts the orthogonal multiple access technology, and each sub-channel is occupied by only one user, ignoring the full utilization of spectrum resources, and cannot guarantee the burst access of a large number of users. works fine.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a flood monitoring data transmission method based on non-orthogonal multiple access, which greatly improves the spectrum utilization rate.

The present invention adopts the following technical solutions for solving the above-mentioned technical problems:

According to a non-orthogonal multiple access-based flood monitoring data transmission method proposed in the present invention, the method includes the following steps:

Step 1. There are multiple monitoring points on each river channel, the multiple monitoring points are distributed at intervals, and the distances between the monitoring points and the base station are different; the base station receives the water level monitoring data collected by different monitoring points on the river channel, and then sends it to the back end data processing center;

Step 2, the back-end data processing center analyzes the water level monitoring data, if the water level exceeds the set early warning water level threshold, the back-end data processing center sends a control signal to the base station;

Step 3: After the base station receives the control signal sent by the back-end data processing center, the non-orthogonal multiple access technology is used to send the control signal to each monitoring point; the non-orthogonal multiple access technology is used to send the control signal to each monitoring point. The specific method of monitoring points is as follows: The base station performs grouping and matching of monitoring points according to the distance from each monitoring point to the base station. Each group has at least two monitoring points and the distances from the monitoring points in the same group to the base station are different. According to the principle that the power allocated from far to near is from large to small, the base station modulates the control signal sent to different monitoring points into a superimposed coded signal and sends it to each monitoring point;

Step 4. Each monitoring point demodulates the superimposed coded signal through serial interference elimination technology.

As a further optimization scheme of the flood monitoring data transmission method based on non-orthogonal multiple access described in the present invention, the control signal includes a control signal used to control the alarm whistle, a control signal used to control multiple cameras in the monitoring point The control signal for angular rotation, the control signal for setting the shooting duration of the camera in the monitoring point, and the control signal for setting the shooting range of the camera in the monitoring point.

As a further optimization scheme of the flood monitoring data transmission method based on non-orthogonal multiple access described in the present invention, in step 3, the superimposed coded signal x is:

Among them, P(i) is the power allocated by the ith monitoring point, m is the number of monitoring points; x(i) is the superimposed coded signal sent by the base station to the ith monitoring point.

As a kind of further optimization scheme of the flood monitoring data transmission method based on non-orthogonal multiple access of the present invention, the signal received by the i-th monitoring point in step 4 is:

y _i =h _i x+n _i (2)

Among them, hi is the channel coefficient between the _ith monitoring point and the base station, and _ni is the sum of Gaussian noise and interference received by the monitoring point.

As a further optimization scheme of the flood monitoring data transmission method based on non-orthogonal multiple access described in the present invention, the number of monitoring points is greater than 2.

Compared with the prior art, the present invention adopts the above technical scheme, and has the following technical effects:

(1) The flood disaster data transmission method based on the non-orthogonal multiple access technology proposed by the present invention can improve the spectrum utilization rate;

(2) Using the different distances from the monitoring point to the base station, the monitoring points with significantly different channel conditions are grouped and paired to share a sub-channel; compared with the traditional orthogonal multiple access transmission method, the spectrum utilization rate is greatly improved.

Description of drawings

Fig. 1 is the data transmission flow chart of flood monitoring based on non-orthogonal multiple access technology;

2 is a schematic diagram of data transmission for flood monitoring based on non-orthogonal multiple access;

Fig. 3 is the scheme comparison diagram of orthogonal multiple access and non-orthogonal multiple access; wherein, (a) is the orthogonal multiple access technology transmission scheme; (b) is the non-orthogonal multiple access technology transmission Program;

Fig. 4 is the SIC decoding process diagram of two monitoring points.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The present invention performs flood monitoring data transmission according to the process shown in FIG. 1, and the specific steps are as follows:

Step 1: Each river channel in the city is equipped with multiple monitoring points, the multiple monitoring points are distributed at intervals, and the distance to the base station is different. After each rainstorm, the cameras at each monitoring point collect the water level monitoring data, and the base station transmits it to the background data processing center.

Step 2: The background data processing center receives the water level monitoring data sent by the base station, and the staff judges whether floods will occur in the river with reference to the set warning water level threshold. If the water level is close to the warning water level threshold, the background data processing center should send out more cameras. Control signals such as angle shooting and camera shooting range expansion are sent to the base station. If the water level exceeds the warning water level threshold, the background data processing center will send an alarm control signal to the base station.

Step 3: After the base station receives the control signal sent by the data processing center in the background, the base station estimates the distance of different monitoring points in the river, and groups and matches the monitoring points according to the difference in channel conditions to ensure that the distances from the monitoring points in the same group to the base station are different. . As shown in Figure 2, it is assumed that two monitoring points 1 and 2 in the same river channel are separated by a certain distance. Monitoring point 1 is closer to the base station and has better channel conditions, while monitoring point 2 is far from the base station and has poor channel conditions. Points are grouped together. Using the method (a) in Figure 3 cannot make full use of the spectrum resources. In order to ensure that each monitoring point can work normally under the limited spectrum resources, the method shown in (b) in Figure 3 is now used. Monitoring point 2 allocates more power, while monitoring point 1, which is closer to the base station, allocates less power. Let the superposition coded signal sent by the base station be:

其中m是监测点的个数；x(i)是基站发送给第i个监测点的叠加编码信号。Among them, P(i) is the power allocated by the i-th monitoring point; the base station transmits the total power

Where m is the number of monitoring points; x(i) is the superimposed coded signal sent by the base station to the i-th monitoring point.

Step 4: The signal received by the i-th monitoring point is:

y _i =h _i x+n _i (2)

因为弱信号x(1)对于监测点2来说相当于噪声，因此可以先解码出强信号x(2)，再通过接收到的信号y₁减去x(2)得到无干扰的x(1)，因此监测点1解码x(1)时就已经去除了x(2)的干扰，监测点1就可以正确解码，完成水位监测的数据传输。Where h _i is the channel coefficient between the ith monitoring point and the base station, n _i is the sum of Gaussian noise and interference received by the monitoring point receiver, and its power spectral density is N _0,i . In the downlink of non-orthogonal multiple access, the serial interference elimination is completed by the monitoring point receiver at the receiving end. When other monitoring points are decoded, the interference to this monitoring point can be eliminated, and this monitoring point can be decoded correctly. Here, as shown in Figure 4, since the signal power allocated to monitoring point 2 is greater than the signal power allocated to monitoring point 1, the signal received by the receiver of monitoring point 2 according to formula (2) is:

Because the weak signal x(1) is equivalent to noise for monitoring point 2, the strong signal x(2) can be decoded first, and then the interference-free x(1) can be obtained by subtracting x(2) from the received signal _y1 ), so when monitoring point 1 decodes x(1), the interference of x(2) has been removed, and monitoring point 1 can decode it correctly to complete the data transmission of water level monitoring.

Here is an overview of the above steps:

step one:

Step 1: Collect water level monitoring data at each monitoring point and perform step 2.

Step 2: Each monitoring point sends the water level monitoring data to the base station.

Step 2:

Step 3: The base station receives the water level monitoring data and then sends it to the background data processing center, and performs step 4.

Step 4: The background data processing center analyzes the water level monitoring data of different monitoring points, and sends the control signal to the base station.

Step 3:

Step 5: After the base station receives the control signal, the monitoring points are grouped and paired, the power is allocated according to formula (1), and step 6 is performed.

Step 6: The base station sends superimposed coded signals to each monitoring point.

Step 4:

Step 7: Calculate the superimposed coded signal received by monitoring point 2 according to formula (2), and perform step 8.

Step 8: serially decode the signal sent to monitoring point 2, and then decode the signal sent to monitoring point 1.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical scope disclosed by the present invention can easily think of changes or substitutions. All should be covered within the protection scope of the present invention.

Claims (5)

1. A flood monitoring data transmission method based on non-orthogonal multiple access is characterized by comprising the following steps:

step one, a plurality of monitoring points are arranged on each river channel and distributed at intervals, and the distances from the monitoring points to a base station are different; the base station receives water level monitoring data collected by different monitoring points on the river channel and then sends the water level monitoring data to the rear-end data processing center;

step two, the back-end data processing center analyzes the water level monitoring data, and if the water level exceeds a set early warning water level threshold, the back-end data processing center sends a control signal to the base station;

thirdly, after receiving the control signal sent by the back-end data processing center, the base station sends the control signal to each monitoring point by adopting a non-orthogonal multiple access technology; the specific method for sending the control signal to each monitoring point by adopting the non-orthogonal multiple access technology is as follows: the base station carries out monitoring point grouping and pairing according to the distance from each monitoring point to the base station, each group is provided with at least two monitoring points, the distances from the monitoring points in the same group to the base station are different, and according to the principle that the distance from the monitoring points in the group to the base station is from far to near, the distributed power is from large to small, the base station modulates the control signals sent to different monitoring points in the group into a superposition coding signal and sends the superposition coding signal to each monitoring point in the group;

and step four, demodulating the superposed coded signals by each monitoring point through a serial interference elimination technology.

2. The flood monitoring data transmission method based on the non-orthogonal multiple access, according to claim 1, wherein the control signals comprise a control signal for controlling alarm whistle, a control signal for controlling multi-angle rotation of a camera in a monitoring point, a control signal for setting shooting duration of the camera in the monitoring point, and a control signal for setting shooting range of the camera in the monitoring point.

3. The method for flood monitoring data transmission according to claim 1, wherein the code signal x is superimposed in three steps:

wherein, P (i) is the power divided by the ith monitoring point, and m is the number of the monitoring points; x (i) is the superposition coded signal sent by the base station to the ith monitoring point.

4. The method for flood monitoring data transmission according to claim 3, wherein the signal received by the ith monitoring point in the fourth step is:

y_i＝h_ix+n_i(2)

wherein h is_iIs the channel coefficient between the ith monitoring point and the base station, n_iIs the sum of the Gaussian noise and the interference received by the monitoring point.

5. The method for flood monitoring data transmission according to claim 1, wherein the number of monitoring points is greater than 2.

Images