阅读说明：本技术 一种基于多普勒效应的上行空分多址系统及实现方法 (Uplink space division multiple access system based on Doppler effect and implementation method ) 是由 马猛 冯浩 于 2020-03-30 设计创作，主要内容包括：本发明公布了一种基于多普勒效应的上行空分多址系统及实现方法,包括一个基站和多个用户；基站中固定在转动圆盘上等间隔分布N根天线,圆盘以ω的角速度旋转,在某时刻仅有一根天线与接收链路联通；系统还包括解调器、带通滤波器、调频模块、电子开关和天线选择单元；只需为不同用户分配相同频率,当用户向基站采用相同频率发送数据时,在基站处通过转动的天线产生多普勒效应,再通过滤波器来分离不同用户采用相同频率发送的数据,实现基于多普勒效应的上行空分多址移动通信。本发明技术方案配置灵活、使用灵活,能够有效解决移动通信系统的频率资源不足问题,有效增加用户容量。(The invention discloses an uplink space division multiple access system based on Doppler effect and a realization method thereof, comprising a base station and a plurality of users; n antennas are distributed in a base station and fixed on a rotating disc at equal intervals, the disc rotates at an angular speed of omega, and only one antenna is communicated with a receiving link at a certain time; the system also comprises a demodulator, a band-pass filter, a frequency modulation module, an electronic switch and an antenna selection unit; only the same frequency needs to be allocated to different users, when the users transmit data to the base station by adopting the same frequency, the Doppler effect is generated at the base station through the rotating antenna, and then the data transmitted by the different users by adopting the same frequency is separated through the filter, so that the uplink space division multiple access mobile communication based on the Doppler effect is realized. The technical scheme of the invention has flexible configuration and flexible use, can effectively solve the problem of insufficient frequency resources of a mobile communication system, and effectively increases the user capacity.)

1. A method for realizing up-line space division multiple access mobile communication based on Doppler effect is characterized in that only the same frequency is needed to be distributed to different users, when different users adopt the same frequency to transmit data to a base station, the Doppler effect is generated at the base station through a rotating antenna, so that the base station receiver considers that the frequencies adopted by different users are different, and then a filter is used for separating the data transmitted by different users by adopting the same frequency, thereby realizing up-line space division multiple access mobile communication based on Doppler effect; the method comprises the following steps:

1) establishing a cellular system of uplink space division multiple access mobile communication based on Doppler effect: comprises a base station and a plurality of users; the receiver in the base station comprises an antenna and a receiving chain; n antennas are distributed in a base station and fixed on a rotating disc at equal intervals, the disc rotates at an angular speed of omega, the radius of the disc is R, and only one antenna is communicated with a receiving link at a certain moment; the system also comprises a demodulator, a band-pass filter, a frequency modulation module, an electronic switch and an antenna selection unit;

2) m users in the system are simultaneously centered on the frequency f_cSending data to a base station, wherein the signal bandwidth is W; different users are in different directions of the base station;

3) at the jth antenna of the base station at the time t, signals of different users generate different Doppler frequency offsets; calculating to obtain the Doppler frequency offset generated by each user at each antenna;

the included angle between the instantaneous movement speed direction of the jth antenna at the moment t and the incident direction of the ith user signal, namely the arrival angle, is expressed as theta_i,j(t); calculating according to the formula (1) to obtain the Doppler frequency offset f generated by the ith user signal at the jth antenna_i,j(t)：

Wherein C is the speed of light;

4) then, the minimum value of the signal frequency deviation absolute value of the target user and other interference users on each antenna is obtained through calculation and is marked as delta f_n；

Knowing the arrival angles of signals of all users at all antennas, calculating the Doppler frequency offset generated by each user at each antenna according to the formula (1);

at the moment t, when the signal of a certain target user M is demodulated, other M-1 users are interference users, frequency offset generated by the target user M and the M-1 interference users on each antenna is calculated through a formula (2), and the minimum value of the signal frequency deviation absolute value of the target user M and the M-1 interference users on each antenna is obtained and is marked as delta f_nAnd n is the antenna serial number:

5) by usingElectronic switch for selecting delta f in all antennas_nThe largest antenna is connected with a receiving link, and signals of interference users are easily separated through a filter;

6) transmitting the received signal to a frequency modulation module to generate a frequency opposite to the Doppler frequency shift of a target user; multiplying the received signal by a time-varying frequency signal generated by a frequency synthesizer of the frequency modulation module so that the center frequency of the target user in the received signal does not change with time any more, thereby allowing the signal of the target user to pass;

7) the signals of the target user and other interference users can be separated through a band-pass filtering module;

through the steps, the uplink space division multiple access mobile communication based on the Doppler effect is realized.

2. The method for implementing uplink space division multiple access mobile communication based on the doppler effect as claimed in claim 1, wherein a frequency modulation module and a filter are disposed before or after the down-conversion module; for the signals which cannot completely filter the interference part, an interleaving technology and a forward error correction code technology can be adopted to completely filter the signals of the interference part.

3. The method as claimed in claim 1, wherein the plurality of users are in different directions of the base station, and transmit data using the same frequency, and the users are in a stationary or low-speed moving state.

4. The method of claim 1, wherein the demodulator is used for demodulating the signal of the target user; the band-pass filtering module is used for separating signals of a target user and an interference user; the frequency modulation module uses a frequency synthesizer to generate a frequency opposite to the Doppler frequency shift of the target user, and multiplies the received signal by a time-varying frequency signal generated by the frequency synthesizer, so that the central frequency of the target user in the received signal does not change along with the time; the electronic switch is used for opening the antenna to switch on the receiving link or closing the antenna; the antenna selection unit is used for controlling the antenna which should be switched off or switched on by the electronic switch.

5. The method of claim 1 in which multiple users simultaneously use a central frequency f for uplink space division multiple access mobile communication_cTransmitting data to a base station; the frequency band used by each user is

6. An uplink space division multiple access mobile communication system based on Doppler effect comprises a base station and a plurality of users; the receiver in the base station comprises an antenna and a receiving chain; the system is characterized in that the system is an uplink space division multiple access technology based on Doppler effect and comprises a base station and an uplink cellular system of a plurality of users; n antennas are distributed in a base station and fixed on a rotating disc at equal intervals, the disc rotates at an angular speed of omega, the radius of the disc is R, and only one antenna is communicated with a receiving link at a certain moment;

a plurality of users are positioned in different directions of the base station, the same frequency is used for transmitting data, and the users are in a static or low-speed motion state; the receiver in the base station comprises an antenna and a receiving link, and the antennas in the base station are all receiving antennas;

the uplink space division multiple access mobile communication system based on the Doppler effect distributes the same frequency for different users, when the different users transmit data to the base station by adopting the same frequency, the Doppler effect is generated at the base station through the rotating antenna, so that the base station receiver considers that the frequencies adopted by the different users are different, and then the data transmitted by the different users by adopting the same frequency is separated through the filter, thereby realizing the uplink space division multiple access mobile communication based on the Doppler effect.

7. The doppler-based uplink sdma mobile communication system as claimed in claim 1, wherein the system further comprises a demodulator, a band pass filter, a fm module, an electronic switch, and an antenna selecting unit;

the demodulator is used for demodulating the signal of a target user; the band-pass filtering module is used for separating signals of a target user and an interference user; the frequency modulation module uses a frequency synthesizer to generate a frequency opposite to the Doppler frequency shift of the target user, and multiplies the received signal by a time-varying frequency signal generated by the frequency synthesizer, so that the central frequency of the target user in the received signal does not change along with the time; the electronic switch is used for opening the antenna to switch on the receiving link or closing the antenna; the antenna selection unit is used for controlling the antenna which should be switched off or switched on by the electronic switch.

Technical Field

The invention belongs to the technical field of mobile communication, and particularly relates to an uplink space division multiple access mobile communication system based on a Doppler effect and an implementation method thereof.

Background

The doppler effect is the change in the wavelength of the object radiation due to the relative motion of the source and the observer. In front of the moving wave source, the wavelength becomes shorter and the frequency becomes higher (blue shift); the opposite effect occurs when the moving wave source is behind. The wavelength becomes longer and the frequency becomes lower (red shift); the higher the velocity of the wave source, the greater the effect produced.

In mobile communication, when a mobile station moves to a base station, the frequency becomes high; the frequency becomes lower when away from the base station. In general, because the performance of the system is impaired by the doppler effect, the doppler effect is avoided as much as possible in a mobile communication system, or the influence of the doppler effect is eliminated by using some techniques.

Conventional multiple access techniques, such as Frequency Division Multiple Access (FDMA), in which different users are allocated different frequencies, and when a user transmits data to a base station, the base station separates the different users by the different frequencies, require allocation of spectrum resources to each user. Similarly, there are Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and the like. These multiple access techniques essentially allocate time-frequency resources that are orthogonal to each other to different users, thereby avoiding interference between the users' signals. In addition, Space Division Multiple Access (SDMA) utilizes channel differences caused by users distributed at different spatial locations, and adopts antennas with spatial resolution, such as directional antennas or antenna arrays, and typical technologies include multi-user MIMO (MU-MIMO) technologies, and the like, which further improve spectrum utilization efficiency, but at the cost of requiring multiple radio frequency links, increasing complexity and cost of the device.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides an uplink space division multiple access mobile communication system based on the Doppler effect and an implementation method thereof. The Doppler effect can be utilized to realize that different users are distributed with the same frequency, when the users transmit data to the base station, the Doppler effect is generated at the base station through the rotating antenna, so that the frequencies of different users are different from the receiver of the base station, and the data transmitted by different users are separated through the filter.

The technical scheme of the invention is as follows:

an uplink space division multiple access mobile communication system based on Doppler effect is an uplink space division multiple access technology based on Doppler effect, and comprises a base station and an uplink cellular system of a plurality of users. The user sends data, the base station receives the data, a receiver in the base station comprises an antenna and a receiving link, and the antennas in the base station are all receiving antennas. A plurality of users are in different directions of the base station, the same frequency is used for transmitting data, and the users are in a static state or a low-speed moving state. N antennas are distributed in a base station and fixed on a rotating disc at equal intervals, the disc rotates at an angular speed of omega, the radius of the disc is R, only one antenna is communicated with a receiving link at a certain moment, and other antennas are disconnected with the receiving link. The system also comprises a demodulator, a band-pass filter module, a frequency modulation module, an electronic switch and an antenna selection unit; the demodulator is used for demodulating the signal of a target user; the band-pass filtering module is used for separating signals of a target user and an interference user; the frequency modulation module uses a frequency synthesizer to generate a frequency opposite to the Doppler frequency shift of the target user, and multiplies the received signal by a time-varying frequency signal generated by the frequency synthesizer, so that the central frequency of the target user in the received signal does not change along with time any more; the electronic switch is used for opening the antenna (connecting a receiving chain) or closing the antenna; the antenna selection unit is used for controlling the antenna which should be switched off or switched on by the electronic switch.

The implementation of the uplink space division multiple access mobile communication system based on the Doppler effect comprises the following processes:

1) a plurality of users in the system simultaneously transmit data to the base station at a central frequency;

user 1, user 2, user M in the system are simultaneously at a central frequency f_cTransmitting data to the base station, wherein the signal bandwidth is W, so that each user uses the frequency band range of WDifferent users are located in different directions of the base station, and on a certain receiving antenna, signals of different users generate different Doppler frequency offsets due to circular motion of the antenna.

2) At the jth antenna of the base station at the time t, signals of different users generate different Doppler frequency offsets; calculating to obtain the Doppler frequency offset generated by each user at each antenna;

at time t, the angle between the instantaneous moving speed direction of the jth antenna and the incident direction of the ith user signal, namely the arrival angle, is represented as theta_i,j(t) Doppler frequency offset f of ith user signal generated at jth antenna_i,j(t) may be represented by formula (1), wherein C is the speed of light.

3) Then, the minimum value of the signal frequency deviation absolute value of the target user and other interference users on each antenna is obtained through calculation and is marked as delta f_n；

Assuming that the arrival angles of signals at all antennas of all users are known, the doppler frequency offset generated at each antenna of each user can be calculated according to equation (1). When demodulating the signal of a certain target user M at time t, other M-1 users are interfering users, and the minimum value of the absolute value of the frequency deviation between the target user M and the M-1 interfering users on each antenna can be obtained by calculating the frequency deviation between the target user M and the M-1 interfering users on each antenna and is marked as delta f_nAnd n is the antenna serial number:

4) electronic switch for selecting delta f in all antennas_nThe largest antenna is connected with a receiving chain;

electronic switch for selecting delta f in all antennas_nThe largest antenna is connected to the receiving chain, where the interfering user signals are most easily separated by a filter.

5) Will be Δ f in all antennas_nAfter the receiving chain is connected with the maximum antenna, the received signal is transmitted to the frequency modulation module to generate a frequency opposite to the Doppler frequency shift of the target user, and the received signal is transmittedMultiplying the time-varying frequency signal generated by a frequency synthesizer of the frequency modulation module so that the center frequency of the target user in the received signal does not change with time any more, thereby passing the signal of the target user;

electronic switch will switch Δ f in all antennas_nAfter the maximum antenna is connected with a receiving link, in order to enable a signal of a target user m to pass through, a received signal is required to be transmitted into a frequency modulation module, the module uses a frequency synthesizer to generate a frequency opposite to the Doppler frequency shift of the target user m, the received signal is multiplied by a time-varying frequency signal generated by the frequency synthesizer, so that the central frequency of the target user m in the received signal does not change along with time, and at the moment, after passing through a band-pass filtering module, the signals of the target user m and an interference user can be separated.

6) The signals of the target user and other interference users can be separated through the band-pass filtering module.

Through the process, only the same frequency needs to be distributed to different users, when different users transmit data to the base station by adopting the same frequency, the Doppler effect is generated at the base station through the rotating antenna, so that the frequencies of different users are different from the receiver of the base station, and then the data transmitted by different users by adopting the same frequency are separated through the filter.

The frequency modulation module and the filter can be used at radio frequency, before intermediate frequency or baseband, namely before the frequency down-conversion module, or after the frequency down-conversion module. For the signals which cannot completely filter the interference part, the technologies of interleaving, forward error correction code and the like can be adopted to completely filter the signals of the interference part.

Compared with the prior art, the invention has the technical advantages that:

the method comprises the following steps of (I) effectively solving the problem of insufficient frequency resources of the mobile communication system;

in the field of mobile communication, different users use the same frequency to send data to a base station, the Doppler effect is generated by the rotation of an antenna to distinguish different users, the gradually exhausted frequency spectrum resources can be fully utilized, and compared with the situation that different users are distributed with different frequencies, the problem of insufficient frequency resources can be effectively solved.

(II) the system is flexible in configuration and use;

another advantage of the present invention is that it is flexible to use, and the areas of different user capacity can be flexibly configured. The user capacity that the base station can hold is determined by the area of the disk, the angular velocity omega of the rotation of the disk and the number N of the antennas, and when the area of the disk, the angular velocity omega of the rotation of the disk and the number N of the antennas are increased, the user capacity is correspondingly increased, so that the problem of the user capacity can be effectively solved.

Drawings

Fig. 1 is a schematic diagram of a composition structure of an uplink sdma system based on the doppler effect according to the present invention. In the figure, the base station has N antennas fixed on a rotating disk at equal intervals, the disk rotates at an angular speed of omega, the radius of the disk is R, and the user 1, the user 2 and the user M in the system simultaneously use a central frequency f_cAnd transmitting the data to the base station.

Fig. 2 is a diagram of a system embodiment of an uplink spatial division multiple access technique based on the doppler effect according to the present invention. In the figure, the base station has 2 antennas fixed on a rotating disc and distributed at equal intervals, the disc rotates at an angular speed of omega, the radius of the disc is R, and a user 1 and a user 2 in the system simultaneously have a central frequency f_cAnd transmitting the data to the base station. The arrival angles of the user 1 and the user 2 with respect to the antenna 1 are θ_1,1And theta_2,1Angles of arrival with respect to the antenna 2 are respectively θ_1,2And theta_2,2。

Fig. 3 is a schematic diagram of an electronic switch selecting antenna of the uplink space division multiple access technology based on the doppler effect. (a) the graph is a frequency curve of signals received by a user 1 and a user 2 at an antenna 1, wherein a solid line is a frequency curve of the user 1, and a dotted line is a frequency curve of the user 2; (b) fig. is a frequency curve of signals received by the antenna 2 for the user 1 and the user 2, wherein the solid line is the frequency curve of the user 1 and the dotted line is the frequency curve of the user 2; (c) the figure shows the frequency offset curves and antenna selection for user 1 and user 2, and the solid line shows the absolute value of the frequency offset when user 1 and user 2 open a specific antenna.

Fig. 4 is a schematic diagram of a frequency modulation module of an uplink sdma technique based on the doppler effect according to the present invention. When a specific antenna is turned on, the solid line is the frequency curve of the user 1, the dotted line is the frequency curve generated by the frequency synthesizer and opposite to the Doppler frequency shift of the user 1, the dashed line is the frequency curve generated by multiplying the user 2 signal and the time-varying frequency signal generated by the frequency synthesizer, and the thick solid line is the frequency curve of the user 1 after passing through the frequency modulation module, so that the center frequency of the user 1 in the received signal does not change along with time any more.

Detailed Description

The invention will be further elucidated by means of specific embodiments in the following description, without in any way limiting the scope of the invention.

As shown in fig. 1, the uplink sdma system based on the doppler effect provided by the present invention is a cellular system, and includes a base station and a scenario of multiple users. A plurality of users are in different directions of the base station, the same frequency is used for transmitting data, and the users are in a static state or a low-speed moving state. The base station is internally provided with N antennas which are fixed on a rotating disc and distributed at equal intervals, the disc rotates at an angular speed of omega, the radius of the disc is R, only one antenna is communicated with a receiving link at a certain moment, and other antennas are disconnected with the receiving link.

User 1, user 2, user M in the system are simultaneously at a central frequency f_cTransmitting data to the base station, wherein the signal bandwidth is W, so that each user uses the frequency band range of WDifferent users are located in different directions of the base station, and on a certain receiving antenna, signals of different users generate different Doppler frequency offsets due to circular motion of the antenna.

At time t, the angle between the instantaneous moving speed direction of the jth antenna and the incident direction of the ith user signal, namely the arrival angle, is represented as theta_i,j(t), Doppler frequency offset f generated by ith user signal at jth antenna at time t_i,j(t) may be represented by formula (1), wherein C is the speed of light.

Assuming that the arrival angles of signals at all antennas of all users are known, the frequency offset generated at each antenna by each user can be calculated according to equation (1). When the signal of a certain target user M is demodulated at the time t, other M-1 users are interference users, and the minimum value of the signal frequency deviation absolute values of the target user M and the M-1 interference users on each antenna can be obtained by calculating the frequency deviation generated by the target user M and the M-1 interference users on each antenna and is marked as delta f_nAnd n is an antenna number and is represented by formula (2).

Electronic switch for selecting delta f in all antennas_nThe largest antenna is connected to the receiving chain, where the interfering user signals are most easily separated by a filter.

Electronic switch will switch Δ f in all antennas_nAfter the maximum antenna is connected with a receiving link, in order to enable a signal of a target user m to pass through, a received signal is required to be transmitted into a frequency modulation module, the module uses a frequency synthesizer to generate a frequency opposite to the Doppler frequency shift of the target user m, the received signal is multiplied by a time-varying frequency signal generated by the frequency synthesizer, so that the central frequency of the target user m in the received signal does not change along with time, and at the moment, after passing through a band-pass filtering module, the signals of the target user m and an interference user can be separated.

Taking two users, two antennas as an example, as shown in (a) and (b) of fig. 3, the solid line in the figure is the doppler frequency of the signal of user 1 at antenna 1 and antenna 2, the dotted line in the figure is the doppler frequency of the signal of user 2 at antenna 1 and antenna 2, and at t₁At the moment when the antenna 2 is switched on, the user 1 and the user 2 are at the same frequency f_cAnd transmitting the data to the base station. The arrival angles of the user 1 and the user 2 with respect to the antenna 1 are θ_1,1And theta_2,1Angles of arrival with respect to the antenna 2 are respectively θ_1,2And theta_2,2Doppler frequency offset generated by user 1 at antenna 1Is composed ofP in FIG. 3(a)₁At the point, user 2 generates a Doppler frequency offset at antenna 1 ofP in FIG. 3(a)₂Point, the frequency offset difference Δ f between user 1 and user 2 at antenna 1 at this time can be obtained from equation (2)₁＝|f_1，1-f_2，1L, |; the Doppler frequency offset generated by the user 1 at the antenna 2 is as follows P in FIG. 3(b)₃At this point, user 2 generates a Doppler frequency offset at antenna 2 ofP in FIG. 3(b)₄Point, which is obtained from equation (2) when user 1 and user 2 have the maximum frequency deviation Δ f at antenna 2₂＝|f_1,2-f_2,2At t |₁At a time of Δ f₁＝Δf₂。

As shown in FIG. 3(a) (b) at t₁At the next time instant Δ f₁>Δf₂When the frequency deviation difference is required to be maximum by the formula (2), the antenna selection unit controls the electronic switch to close the antenna 2 and open the antenna 1 until t₂Time of day, Δ f₁And Δ f₂Again equal, at t₂At the next time instant Δ f₁<Δf₂When the maximum frequency offset is required by equation (2), the antenna selection unit controls the electronic switch to turn off the antenna 1 and turn on the antenna 2, and so on, the solid line in fig. 3(c) is the absolute value of the frequency offset between the user 1 and the user 2 and the antenna selection case separated by the dotted line.

After the electronic switch selects the antenna with the largest frequency deviation, in order to enable the signal of the user 1 to pass through, as shown by a solid line in fig. 4, a received signal is required to be transmitted to a frequency modulation module, the module uses a frequency synthesizer to generate a frequency opposite to the doppler frequency shift of the user 1, as shown by a dotted line time-varying frequency curve in fig. 4, the received signal is multiplied by a time-varying frequency signal generated by the frequency synthesizer, as shown by a user 1 frequency curve after a thick solid line in fig. 4 passes through the frequency modulation module, so that the central frequency of the user 1 in the received signal does not change along with time, as shown by a dashed line in fig. 4, the user 2 signal is multiplied by a time-varying frequency signal generated by the frequency synthesizer, as shown by a dashed line in fig. 4, the user 2 signal and the user 1 signal generate a larger frequency interval, at this time, after passing through a band-pass filtering module, the signals of the user 1 and the user 2 can be separated.

The frequency modulation module and the filter can be at radio frequency, intermediate frequency or baseband, namely before or after the down-conversion module. For signals which cannot completely filter out interference parts, the method can also adopt technologies such as interleaving, forward error correction codes and the like to solve the problem.

Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.