WO2009039712A1

WO2009039712A1 - Method and system for realizing covering sectors by using enantiomorphous radio units

Info

Publication number: WO2009039712A1
Application number: PCT/CN2008/000194
Authority: WO
Inventors: Meiling Ding; Linjiang Chen; Jufeng Gu
Original assignee: Zte Corporation
Priority date: 2007-09-25
Filing date: 2008-01-28
Publication date: 2009-04-02
Also published as: CN101141778A

Abstract

The present invention provides a method and a system for realizing covering sectors by using enantiomorphous radio units. The method includes: a plurality of radio units being connected to a baseband unit after the radio units are concatenated with each other, except for a remotest radio unit, the other radio units being all the enantiomorphous radio units; each enantiomorphous radio unit independently converting uplink analog signals received from the corresponding coverage sector to digital signals, the remotest radio unit transferring the obtained digital signals to the next stage enantiomorphous radio unit; each stage enantiomorphous radio unit adding the digital signals transferred from the upper stage enantiomorphous radio unit to the digital signals obtained by sampling locally, then transferring the added digital signals to the next stage, transferring stage by stage as such until the last enantiomorphous radio unit transfers the added digital signals to the baseband unit to perform baseband processes. By using the method of the present invention, a plurality of covered sectors in a same cell could be obtained to satisfy the coverage need for a network, reduce the need for process abilities of the baseband process unit, and reduce costs for establishing the network.

Description

Method and system for realizing partition coverage by using mirrored radio unit

Technical field

The present invention relates to a partition coverage technique based on a baseband unit (BBU) and a radio frequency unit (RRU) structure in a mobile communication system, and more particularly to a method and system for implementing partition coverage using a mirrored RRU.

Background technique

Partition coverage of wireless communication systems is a basic requirement for providing continuous services. Due to the wireless signal propagation characteristics of the coverage area and the limited power amplifier of the wireless system, multi-channel technology has become an important means of solving the coverage of the partition.

An omni-directional transmission is disclosed in the international patent application entitled "Cellular Telecommunications Network with an OMNI Directional Transmitter Type and a Sectored Receiver Type" (OTSR), which is filed on December 20, 2000, with the patent number WO/2001/047148. A method of sectorized reception to increase the coverage area of the uplink and downlink, and the OTSR system transmits the omnidirectional transmission. In the Chinese Patent Application No. 200410001028.3, "A Method for Effectively Covering Expressways", which was filed on January 16, 2004, discloses the use of dual antennas of the same sector to cover different directions to improve the performance of the covered highway. . In the TD-SCDMA system, an existing technical solution is to combine the multi-channel technology with the smart antenna technology to increase the coverage area of the uplink and downlink. As shown in FIG. 1, the smart antenna is also called The array antenna is capable of adaptively beamforming the mobile user signal and tracking the motion of the user; another prior art technique is to place different antennas on different floors to provide indoor coverage, as shown in FIG.

In addition, as the digital signal processing capability of the device is enhanced, centralized baseband signal processing becomes possible. Therefore, a baseband unit (BBU) can be connected to a plurality of radio frequency units (RRUs) to fully utilize the processing capabilities of the BBU.

In the OTSR system, each antenna needs to have a separate uplink channel processing unit in the baseband and intermediate frequency parts, so the number of channels occupied is larger; and the downlink power is equally distributed to multiple antennas. Can cause signal distortion and shorten the antenna coverage distance. In a conventional multi-channel system, each antenna corresponds to a separate uplink and downlink channel processing unit; and if a coupler is used to combine multiple antenna analog signals into one channel processing unit, it is not conducive to multi-antenna management. At the same time, since the analog signal may be distorted during the transmission process, the signal coverage distance of the uplink and downlink RRUs may be shortened, and the smart antenna technology may not be utilized.

It can be seen that the implementation of partition coverage in a wireless communication system faces various challenges. On the one hand, it is desirable to cover as much as possible. On the other hand, it is desirable to occupy the least amount of uplink and downlink channel processing resources while ensuring normal signal processing. If the system can achieve equalization in channel processing power and antenna processing capability, it will play an important role in system application and performance improvement. The transmission of digital signals between the baseband processing section and the RF processing section will increase the reliability and flexibility of signal transmission and reduce the complexity of the construction, especially for wireless communication systems employing multiple antenna techniques.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method and system for realizing partition coverage by using a mirrored radio unit, which not only expands the coverage capability of the cell but also increases the requirement for the BBU processing capability.

In order to solve the above technical problem, the present invention provides a method for implementing partition coverage by using a mirrored radio unit, including:

Multiple radio frequency units are cascaded and connected to the baseband unit. Except for the farthest radio frequency unit, the other radio frequency units are mirrored radio frequency units;

Each of the radio frequency units independently converts the uplink analog signal received from the corresponding coverage area into a digital signal, and the far-end radio frequency unit transmits the obtained digital signal to the mirrored radio frequency unit of the next stage;

Each level of the mirrored RF unit superimposes the digital signal transmitted from the upper-level RF unit with the locally sampled digital signal and then transmits it to the next stage, so that it is transmitted step by step until the last mirrored RF unit will superimpose the number. The signal is transmitted to the baseband unit for baseband processing.

Further, in the downlink direction, the baseband unit separately transmits downlink digital signals to each of the cascaded radio frequency units, and each radio frequency unit independently converts the downlink digital signals into analog signals and transmits the signals to the corresponding coverage areas. Further, the digital signal transmission adopts a single channel transmission manner.

Further, the radio frequency unit adopts multiple antennas, and adopts multi-channel transmission mode in digital signal transmission; in the uplink direction, each cascaded mirror radio frequency unit correspondingly receives signals of multiple antennas from corresponding coverage areas. The analog-to-digital conversion is performed on each signal channel, and the digital signals transmitted from the upper-level radio frequency unit are superimposed and superimposed according to the identifiers of the respective signal channels, and are transmitted to the next stage until the last-level mirrored radio frequency unit is superposed on the alignment. The digital signals are transmitted to respective corresponding signal channels in the baseband unit for baseband processing.

Further, the superimposing the digital signal transmitted from the upper-level radio frequency unit and the digital signal obtained by the local sampling is a saturated superposition method.

Further, when the multi-channel transmission mode is adopted, in the downlink direction, the baseband unit separately transmits the downlink digital signals from the respective signal channels to the respective radio frequency units, and each of the radio frequency units independently converts the downlink digital signals into analog signals and Each antenna corresponding to each signal channel is separately transmitted to a corresponding coverage area.

Further, the radio frequency unit independently performs power calibration in the associated coverage area.

Further, the cascaded plurality of radio frequency units include at least two radio frequency units, and each of the two radio frequency units is respectively connected to a set of linear array smart antennas, and the two sets of linear array smart antennas are respectively oriented in different directions. And the mirror beam shaping method is adopted, and when the user passes the intersection of two sectors corresponding to the two radio frequency units, the main beams of the two sets of beams face the same position.

In order to solve the above technical problem, the present invention further provides a system for realizing partition coverage by using a mirrored radio unit, the system comprising a plurality of cascaded radio frequency units, and a baseband unit connected to one of the radio frequency units, the cascade Except for the most remote primary RF unit, the rest of the RF units are mirrored RF units, where:

The baseband unit is configured to receive, in an uplink direction, an uplink digital signal transmitted by a mirrored radio frequency unit of a first level and perform baseband processing;

The main radio unit is configured to convert the received analog signal into a digital signal in an uplink direction, and transmit the signal to the mirror radio unit of the next stage;

The mirrored radio unit is configured to convert the received analog signal into a digital value in an uplink direction The signal is superimposed with the digital signal obtained by the local sampling and transmitted to the mirrored radio unit or baseband unit of the next stage.

Further, the baseband unit is further configured to separately transmit downlink digital signals to the cascaded radio frequency units in a downlink direction;

The primary radio frequency unit and the mirrored radio frequency unit are further configured to independently convert the downlink digital signal into an analog signal in a downlink direction and transmit the signal to the corresponding coverage area.

Further, the primary radio unit includes an antenna unit, an uplink signal conversion unit, and a downlink signal conversion unit, where:

The antenna unit is configured to send the downlink signal output by the downlink signal conversion unit in a corresponding coverage area, and receive an uplink signal in a corresponding coverage area and output the signal to the uplink signal conversion unit;

The uplink signal conversion unit is configured to convert an analog signal received by the antenna unit into a digital signal, and output the image to a mirrored radio frequency unit of a next stage;

The downlink signal conversion unit is configured to convert the digital signal transmitted by the baseband unit into an analog signal, and output the signal to the antenna unit;

The mirrored radio unit includes an antenna unit, an uplink signal conversion unit, a downlink signal conversion unit, and a digital synthesis unit, where:

The uplink signal conversion unit is configured to convert an analog signal received by the antenna unit into a digital signal, and output the signal to a digital synthesis unit;

The digital synthesizing unit is configured to superimpose the digital signal transmitted by the upper-level radio frequency unit and the digital signal output by the uplink signal converting unit.

Further, the radio frequency unit uses a plurality of antennas; the uplink signal conversion unit performs analog-to-digital conversion on signals corresponding to the plurality of antennas from the corresponding coverage areas, and inputs And outputting to the digital synthesizing unit; the digital synthesizing unit superimposes the digital signal transmitted from the upper-level radio frequency unit and the digital signal outputted by the uplink signal converting unit according to the identification of each signal channel and transmits to the next stage; The unit performs baseband processing on each downlink signal channel signal;

The baseband unit separately transmits downlink digital signals from its respective signal channels to the respective radio frequency units; the downlink signal conversion unit converts the downlink digital signals transmitted by the baseband unit into analog signals and respectively through respective antennas corresponding to the respective signal channels. Send to the appropriate coverage area.

Further, the superposition performed by the mirrored radio frequency unit adopts a saturated superposition manner. Further, the cascaded plurality of radio frequency units include at least two radio frequency units, and each of the two radio frequency units is respectively connected to a set of linear array smart antennas, and the two sets of linear array smart antennas are respectively oriented in different directions. And adopting the mirror beamforming manner, when the user passes the intersection of two sectors corresponding to the two radio frequency units, the main beams of the two sets of beams face the same position.

The main advantages and features of the present invention are as follows:

1. Maintain the coverage radius of each RRU. If the capacity is not limited, the coverage capacity of the cell can be extended, and the processing capacity of the BBU can be reduced to achieve cost savings. Compared with the method of partition coverage by power splitter, it has the advantage of coverage radius. At the same time, the digital signal processing between different RRU signals in the uplink direction avoids the noise introduced by the combiner, and the digital signal transmission in the downlink direction avoids the introduction of the power splitter. Noise and attenuation.

2. The mirrored RRU is also applicable to some special networking scenarios, such as applying to highway/railway coverage scenarios to reduce dropped call drops, and applying to indoor coverage scenarios to support more coverage areas with fewer BBU channels. Wait.

3. In the future network construction, the mirrored RRU is changed to the primary RRU, and the RRU signal is processed independently in the BBU to achieve the purpose of capacity expansion. BRIEF abstract

1 is a schematic diagram of a conventional smart antenna in road coverage;

2 is a schematic diagram of an existing indoor coverage based on BBU plus RRU; 3 is a structural diagram of a system for implementing partition coverage by using a mirrored RRU according to the present invention; FIG. 4 is a schematic diagram of a multi-mirror RRU according to Embodiment 1 of the present invention;

5 is a schematic diagram of applying a mirrored RRU to a highway coverage according to Embodiment 2 of the present invention; FIG. 6 is a schematic diagram of applying a mirrored RRU to an indoor coverage according to Embodiment 3 of the present invention. Preferred embodiment of the invention

Referring to Figure 3, a method and system for implementing partition coverage using mirror R U proposed by the present invention will be described.

In this document, the primary RRU refers to the most remote RRU, and the mirrored RRU refers to each RRU that is cascaded in the uplink direction to the primary RRU or to another mirrored RRU.

In the downlink direction, the BBU transmits a downlink digital signal to each of the cascaded RRUs, and each RRU independently acquires and converts the downlink digital signal into an analog signal and transmits it to the corresponding coverage area through the antenna. Here, the primary RRU and each mirrored RRU obtain the same downlink data from the same signal transmitted from the BBU.

In the uplink direction, each cascaded mirrored RRU converts the signal received by the antenna from the corresponding coverage area into an analog signal, and superimposes the digital signal transmitted by the upper stage RU with the locally sampled digital signal. The next level of transmission, and finally transmitted to the BBU for unified processing, where only one uplink digital signal is transmitted to the BBU. Here, the superposition may adopt a saturated superposition method, that is, whether the digital signal transmitted from the upper RRU and the locally sampled digital signal are added to exceed the maximum threshold value, and if the superposition is exceeded, the superposition result is the maximum threshold value, if If there is no more than the superimposed result is the actual sum of the digital signals. Since the digital signals are superimposed, the bandwidth of the data transmission in the uplink and downlink directions is independent of the number of RRUs.

For multiple antennas on each RU, each antenna connected to each RRU can achieve independent power calibration. The mirrored RRU technology can also be used in combination with traditional multi-channel technology. At this time, each RRU implements independent antenna correction. Conducive to the application of smart antennas. The solution of mirroring RRU technology combined with multi-channel technology is as follows:

In the downlink direction, the BBU transmits downlink digital signals from its respective signal channels to the cascaded RRUs, and each RRU independently converts the downlink digital signals into analog signals and passes each The antennas corresponding to the signal channels are respectively sent to the corresponding coverage areas. In the uplink direction, each cascaded RRU performs analog-to-digital conversion on signals corresponding to the plurality of antennas from the respective coverage areas, and the digital signals transmitted from the upper-level RUs are in accordance with the respective signal channels. The identifier is superimposed and transferred to the next stage until the last stage mirror RU transmits the digital signal after the bit superposition to each corresponding signal channel in the BBU for baseband processing.

In the solution combining the mirror RRU technology and the multi-channel technology, the digital signals are composed of the split signals on the respective signal channels, and the processing of each of the split signals is treated as the processing of the above one signal, so each RRU is locally sampled. The obtained digital signal is superposed with the digital signal transmitted by the upper-level RU according to the channel number, that is, the sampling signal of the channel N is superimposed with the channel N signal transmitted by the previous stage, and the superposition method may adopt a saturated superposition. The superposition method can also be an unsaturated superposition, but the unsaturated superposition complexity is low, which is suitable for the case where the signal superposition is unsaturated. This alignment is beneficial to the use of smart antennas, but introduces certain uplink noise, which amplifies the thermal noise of the RRU coverage area of the user and has a certain negative impact on the system capacity, but introduces relatively few interference sources. Therefore, it is suitable for applications where capacity is not limited.

In the RRU that can be independently maintained, in the uplink direction, each RRU includes an antenna unit and an uplink signal conversion unit, and each of the mirrored RRUs further includes a digital synthesis unit. In the downlink direction, each RRU includes a downlink signal conversion unit. among them:

The antenna unit on each RRU is configured to send the downlink signal outputted by the downlink signal conversion unit in the corresponding coverage area, and receive the uplink signal in the corresponding coverage area and output to the uplink signal conversion unit, which is composed of one or more antennas. ;

An uplink signal conversion unit on each RRU is configured to convert an uplink signal received by the antenna unit from an analog signal to a digital signal, and the uplink signal conversion unit may be composed of an analog-to-digital converter (A/D converter), A/D The number of converters is equal to the number of signal channels;

a digital synthesizing unit on each of the mirrored RRUs for superimposing the digital signal transmitted by the upper-level RRU with the digital signal obtained by the local sampling (that is, output by the uplink signal converting unit), and the digital synthesizing unit may be added by an adder or Similar to the device composition, the number of adders is equal to the number of signal channels; A downlink signal conversion unit on each RRU is configured to convert the digital signal transmitted by the BBU into an analog signal output to the antenna unit, and the downlink signal conversion unit may be composed of a digital-to-analog converter (D/A converter), D/ The number of A converters is equal to the number of signal channels.

The scheme for realizing the partition coverage by using the mirror RRU can meet the network coverage of the cell and some special scenarios. In the following, the technical features and functional features of the present invention will be further described in detail through three embodiments. Embodiment 1 is a scenario in which the technical solution of the present invention is applied to a cell covering multiple areas to reduce the network construction cost, as shown in FIG. 4 . The antennas of the N independent areas are respectively connected to the respective RRUs.

In the downstream direction, the BBU transmits the baseband digital domain signal that needs to be transmitted to the RRU, to N

The signal sent by the RRU is exactly the same; in the uplink direction, the RRU processes the received signal of the antenna independently, and outputs the baseband digital domain signal. The mirrored RRU digitally superimposes the signal transmitted by the previous RRU and the local sampled signal according to the identifier of the signal channel. The superimposed signal is subjected to baseband processing by the BBU.

At the same time, the RRU independently performs power calibration in the coverage area, so that one cell can cover N different coverage areas, thereby achieving wide coverage, reducing the need for BBU processing capability, and saving network construction cost. . If the network is to be expanded, the RRU (including the primary RRU and the mirrored RRU) directly outputs signals to the BBU, that is, no signal superposition is performed in the middle to form a multi-cell signal, and the corresponding baseband needs to separately process the multiple signals, and appropriately increase Transmission bandwidth between the BBU and the RRU. In this way, N different coverage areas belonging to the same cell can be split into N or N different cells, thereby achieving the purpose of improving network capacity. Therefore, the mirrored RRU technology has good scalability.

Embodiment 2 is a scenario in which the technical solution of the present invention is applied to highway coverage, as shown in FIG. Taking TD-SCDMA technology as an example, it is assumed that each group consists of two sets of linear array smart antennas including M antennas, which are respectively oriented in two directions of the highway, and each set of smart antennas is respectively connected to one RRU.

In such applications, when two or more sets of smart antennas are included, the orientation of each set of antennas is different. The orientation of the antenna itself corresponds to different coverage areas, but due to the directional shaping, the signal can follow The weight changes direction. In the different directions, the shield is used to enlarge the coverage area, and at the same time, the effect of simultaneously forming the overlapping area can be achieved.

Similar to the existing RRU function, the RRU performs power calibration and antenna correction on the respective smart antennas. Different from the existing RRU function: In the downlink direction, the digital baseband signal output by the BBU is simultaneously transmitted to the cascaded RRU, and the two RRUs acquire the same baseband signal and perform subsequent downlink signal processing; in the uplink direction, each RRU pair The signals received on the M antennas are independently processed in the corresponding M signal channels, and the baseband data of the M antennas are sampled, and the mirrored RRUs transmit the digital signals and the local sampled signals transmitted by the upper RRU according to the signal channels. The identifier is superimposed and transmitted to the next-level RRU, and finally the B-band performs the baseband signal processing of the M-channel, including the processing related to the smart antenna, and M is greater than or equal to 1. Assuming that each set of smart antennas has M antennas, the above-mentioned alignment superposition means that the signals of the first antenna of the first set of smart antenna antennas and the signals of the first antenna of the second set of smart antennas are superimposed, or, finally, the baseband The first channel of the resulting signal is the sum of the signals of the first antennas of all smart antennas, the second channel is the sum of the signals of the second antennas of all smart antennas, and so on. It can be seen from Fig. 5 that the smart antenna array composed of M ^ L antennas has the same data input from the RRU channel, so that the two sets of downlink beams are exactly the same, that is, the mirror beam is shaped. When the user passes through the intersection of two sectors, the main beams of the two sets of beams face the same position (ie, the position where the user is located), which is the edge covered by the two sets of smart antennas, and the signal quality is poor, so the two sets of antennas At the same time, the position is shaped to enhance the signal shield, thereby reducing the dropped calls in the overlapping area. Since the two sectors belong to the same cell, the user does not have a cell handover, which avoids the problem that the user moves too fast, resulting in insufficient time for switching, resulting in call drop rate. This technical solution is also applicable to the coverage of high-speed railways.

Embodiment 3 is a scenario in which the technical solution of the present invention is applied to indoor coverage, as shown in FIG. 6. Taking WCDMA technology as an example, it is assumed that each antenna covers different areas separately, and each antenna is connected to one RRU.

In the downlink direction, the digital baseband signal output by the BBU is transmitted to all the cascaded RRUs, and each RRU acquires the same baseband signal and performs subsequent downlink signal processing; in the uplink direction, each RRU receives the signal independently on the antenna, And sample the antenna baseband data, and then The data transmitted by the previous RU is saturated and superimposed with the local antenna sample data, and transmitted to the next RRU. The last stage RRU transfers the superimposed data to the BBU for baseband processing.

It can be seen that the mirrored R U technology is used in multiple unrelated areas to obtain multiple coverage zones of the same cell, which meets the network coverage requirements, reduces the need for processing power of the baseband processing unit, and reduces the network construction cost. In addition, the mirrored RRU is also applicable to some special networking scenarios, such as applying to highway/railway coverage scenarios to reduce dropped call drops, and applying to indoor coverage scenarios to support more coverage areas with fewer BBU channels. Wait.

The present invention has been disclosed in the foregoing preferred embodiments, which are intended to be illustrative only and not to limit the scope of the present invention. Within the scope of this application.

INDUSTRIAL APPLICABILITY The method and system of the present invention can obtain multiple coverage zones of the same cell, satisfy the network coverage requirements, reduce the need for the processing capability of the baseband processing unit, and reduce the network construction cost; the method and method of the present invention The system is also suitable for some special networking scenarios, such as applying to highway/railway coverage scenarios to reduce dropped call drops, to indoor coverage scenarios to support more coverage areas with fewer BBU channels.

Claims

K A method for realizing partition coverage by using a mirrored radio unit, wherein a plurality of radio frequency units are cascaded and connected to a baseband unit, and other radio frequency units are mirrored radio frequency units except for the farthest radio frequency unit;

2. The method of claim 1 wherein:

In the downlink direction, the baseband unit separately transmits downlink digital signals to the cascaded radio frequency units, and each radio frequency unit independently converts the downlink digital signals into analog signals and transmits them to corresponding coverage areas.

3. The method according to claim 1, wherein the digital signal is transmitted by using a single channel transmission.

4. The method of claim 1 wherein:

The radio frequency unit adopts multiple antennas, and adopts multi-channel transmission mode in digital signal transmission; in the uplink direction, each cascaded mirror radio frequency unit transmits signals of multiple antennas from corresponding coverage areas in corresponding signals. The analog-to-digital conversion is performed on the channel, and the digital signals transmitted from the upper-level radio frequency unit are superposed and superimposed according to the identifiers of the respective signal channels, and are transmitted to the next stage until the last-stage mirrored radio frequency unit will superimpose the digital signals after the alignment. Transfer to each corresponding signal channel in the baseband unit for baseband processing.

The method according to any one of claims 1 to 4, wherein the superimposing the digital signal transmitted from the upper-level radio frequency unit and the digital signal obtained by the local sampling is saturated superimposed. the way.

6. The method of claim 4, wherein

In the multi-channel transmission mode, in the downlink direction, the baseband unit separately transmits downlink digital signals from its respective signal channels to the respective radio frequency units, and each radio frequency unit independently converts the downlink digital signals into analog signals and passes through each The antennas corresponding to the signal channels are respectively sent to the corresponding coverage areas.

7. A method according to any one of claims 1 to 4, characterized in that the radio frequency unit independently performs power calibration in the associated coverage area.

8. The method of claim 6 wherein:

Each of the plurality of cascaded radio frequency units includes at least two radio frequency units, and each of the two radio frequency units is respectively connected to a set of linear array smart antennas, and the two sets of linear array smart antennas are respectively oriented in different directions and adopted The way the mirror beam is shaped, and when the user passes the intersection of the two sectors corresponding to the two radio units, the main beams of the two sets of beams face the same position.

A system for realizing partition coverage by using a mirrored radio unit, wherein the system comprises a plurality of cascaded radio frequency units, and a baseband unit connected to one of the radio frequency units, wherein the cascaded radio frequency units are Outside the most remote primary RF unit, the rest are mirrored RF units, where:

The mirrored radio frequency unit is configured to convert the received analog signal into a digital signal in an uplink direction, superimpose the digital signal transmitted by the upper-level radio frequency unit and the digital signal obtained by the local sampling, and then go to the next level. Mirror RF unit or baseband unit transmission.

10. The system of claim 9 wherein:

The baseband unit is further configured to separately transmit downlink digital signals to the cascaded radio frequency units in a downlink direction; The primary radio frequency unit and the mirrored radio frequency unit are further configured to independently convert the downlink digital signal into an analog signal in a downlink direction and send the signal to a corresponding coverage area.

11. The system of claim 10, wherein:

The primary radio unit includes an antenna unit, an uplink signal conversion unit, and a downlink signal conversion unit, where:

12. The system of claim 10, wherein:

The radio frequency unit uses a plurality of antennas; the uplink signal conversion unit performs analog-to-digital conversion on signals corresponding to the plurality of antennas from the corresponding coverage areas, and outputs the signals to the digital synthesis unit; the digital synthesis unit Digital signal and uplink signal transmitted from the upper-level radio unit The digital signals output by the number conversion unit are superimposed and superimposed according to the identification of each signal channel and transmitted to the next stage; the baseband unit performs baseband processing on each of the corresponding signal channel signals of the downlink;

The system according to any one of claims 9 to 12, wherein the superimposition performed by the mirrored radio frequency unit is in a saturated superposition manner.

14. The system of claim 12, wherein:

Each of the plurality of cascaded radio frequency units includes at least two radio frequency units, and each of the two radio frequency units is respectively connected to a set of linear array smart antennas, and the two sets of linear array smart antennas are respectively oriented in different directions and adopted In the manner of mirror beamforming, when the user passes the intersection of two sectors corresponding to the two radio units, the main beams of the two sets of beams face the same position.