Air interface calibration method and device of indoor distributed system, network equipment and medium

Abstract

The invention discloses an air interface calibration method and device of an indoor distributed system, network equipment and a medium, and relates to the technical field of communication, and the indoor distributed system comprises a BBU, at least one Hub connected with the BBU, and a plurality of RRUs connected with the Hub. According to the implementation scheme, the method comprises the following steps: performing calibration measurement on a first calibration sequence mutually sent by a plurality of antennas in the same RRU through a set sending mode to obtain a first phase offset calibration factor of each antenna in the same RRU; performing phase offset calibration on each antenna based on the first phase offset calibration factor of each antenna in the same RRU; performing calibration measurement on second calibration sequences mutually sent between different RRUs to obtain a second phase offset calibration factor of each RRU; performing phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU; wherein the first or second calibration sequence is sent by the BBU to the RRU through the Hub. Therefore, the application scene of air interface calibration can be widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, in particular to an air interface calibration method and device for an indoor distributed system, a network device and a medium. BACKGROUND

[0002] Hub merging is a very important deployment means in an indoor distributed system. By introducing a Hub node between a BBU (Baseband Unit) and an RRU (Radio Remote Unit), the system can more flexibly manage signal transmission. The main function of the Hub is to combine the uplink signals of multiple RRUs and then transmit the combined uplink signals to the BBU for processing. Meanwhile, the Hub also distributes the downlink signals sent by the BBU to different RRUs to achieve distributed transmission of signals.

[0003] In an indoor distributed system, in order to ensure the quality and efficiency of signal transmission, coordinated downlink transmission between RRUs becomes particularly critical, and to achieve such coordinated transmission, the phase offset (i.e., phase deviation) between channels must be calibrated.

[0004] In related technologies, only the scenario where Hub channel merging is not performed between RRUs (i.e., the direct connection mode of RRU and BBU) is proposed. The phase offset of the RRU is measured by the BBU, and the baseband signal is directly compensated based on the phase offset of the RRU. However, this method cannot be applied to the Hub merging scenario. SUMMARY

[0005] The present application provides an air interface calibration method and device for an indoor distributed system, a network device and a medium.

[0006] According to a first aspect of the present application, an air interface calibration method for an indoor distributed system is provided, the indoor distributed system comprising a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to the Hub, comprising: performing calibration measurement on a first calibration sequence transmitted between multiple antennas in the same RRU through a set transmission mode to obtain a first phase offset calibration factor of each antenna in the same RRU; performing phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU; performing calibration measurement on a second calibration sequence transmitted between different RRUs to obtain a second phase offset calibration factor of each RRU, and performing phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU; wherein the first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

[0007] According to a second aspect of the present application, a network device is provided, comprising a memory, a transceiver, and a processor;

[0008] The memory is configured to store a computer program; the transceiver is configured to transceive data under control of the processor; and the processor is configured to read the computer program in the memory and perform the following operations: performing calibration measurement on first calibration sequences transmitted between multiple antennas in a same RRU by a set transmission mode, to obtain a first phase offset calibration factor of each antenna in the same RRU; wherein the RRU is deployed in an indoor distributed system, the indoor distributed system comprising a BBU, at least one Hub connected to the BBU, and multiple RRUs connected to the Hub; performing phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU; performing calibration measurement on second calibration sequences transmitted between different RRUs, to obtain a second phase offset calibration factor of each RRU, and performing phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU; wherein the first calibration sequences or the second calibration sequences are transmitted from the BBU to the RRUs via the Hub.

[0009] According to a third aspect of the present application, an air interface calibration apparatus of an indoor distributed system is provided, the indoor distributed system comprising a BBU, at least one Hub connected to the BBU, and multiple RRUs connected to the Hub, comprising: a measurement unit configured to perform calibration measurement on first calibration sequences transmitted between multiple antennas in a same RRU by a set transmission mode, to obtain a first phase offset calibration factor of each antenna in the same RRU; a calibration unit configured to perform phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU; and a processing unit configured to perform calibration measurement on second calibration sequences transmitted between different RRUs, to obtain a second phase offset calibration factor of each RRU, and perform phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU; wherein the first calibration sequences or the second calibration sequences are transmitted from the BBU to the RRUs via the Hub.

[0010] According to a fourth aspect of the present application, a processor readable storage medium is provided, the processor readable storage medium storing a computer program, the computer program being configured to cause a processor to perform any of the air interface calibration methods of the indoor distributed system according to the first aspect.

[0011] According to another aspect of the present application, a computer program product is provided, when instructions in the computer program product are executed by a processor, performing any of the air interface calibration methods of the indoor distributed system according to the first aspect.

[0012] The application has the following technical effects: in the Hub merging scene, the same RRU can be used to send calibration sequences between different antennas in the same RRU by setting the sending mode, to realize targeted or independent calibration compensation of different antennas in the same RRU, and the different RRU can be used to send calibration sequences between different antennas in the same RRU, to realize targeted or independent calibration compensation of each antenna in the different RRU, which not only can reduce the error and distortion of the signal in the transmission process, improve the communication quality, but also can widen the application scene of the air interface calibration, and improve the applicability of the method.

[0013] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the application, nor is it used to limit the scope of the application. Other features of the application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0014] The accompanying drawings are used to better understand the present application, and do not constitute a limitation of the present application. Among them:

[0015] Figure 1 is the existing frequency domain resource occupation schematic diagram;

[0016] Figure 2 is the structure schematic diagram of the direct connection scene of the existing RRU and BBU;

[0017] Figure 3 is the structure schematic diagram of the Hub merging scene or indoor distributed system provided by the embodiment of the application Figure 1 ;

[0018] Figure 4 is the structure schematic diagram of the Hub merging scene or indoor distributed system provided by the embodiment of the application Figure 2 ;

[0019] Figure 5 is the flowchart of the air interface calibration method of the first indoor distributed system provided by the embodiment of the application;

[0020] Figure 6 is the flowchart of the air interface calibration method of the second indoor distributed system provided by the embodiment of the application;

[0021] Figure 7 is the frequency domain resource schematic diagram of the different RRU frequency division multiplexing in the RRU calibration provided by the embodiment of the application;

[0022] Figure 8 is the structure of the indoor distributed system and the sending timing schematic diagram of the different RRU frequency division multiplexing in the RRU calibration provided by the embodiment of the application;

[0023] Figure 9is a flowchart of a third air interface calibration method of an indoor distributed system provided by embodiments of the present application;

[0024] Figure 10 is a frequency domain resource diagram of different antenna frequency division multiplexing when RRU calibration is performed according to embodiments of the present application Figure 1 ;

[0025] Figure 11 is a structure diagram of an indoor distributed system and a time division multiplexing diagram of different RRUs when RRU calibration is performed according to embodiments of the present application

[0026] Figure 12 is a frequency domain resource diagram of different antenna frequency division multiplexing when RRU calibration is performed according to embodiments of the present application Figure 2 ;

[0027] Figure 13 is a flowchart of a fourth air interface calibration method of an indoor distributed system provided by embodiments of the present application;

[0028] Figure 14 is a structure diagram of an indoor distributed system and a code division multiplexing diagram of different RRUs when RRU calibration is performed according to embodiments of the present application

[0029] Figure 15 is a flowchart of a fifth air interface calibration method of an indoor distributed system provided by embodiments of the present application;

[0030] Figure 16 is a flowchart of a sixth air interface calibration method of an indoor distributed system provided by embodiments of the present application;

[0031] Figure 17 is a flowchart of a seventh air interface calibration method of an indoor distributed system provided by embodiments of the present application;

[0032] Figure 18 is a flowchart of a calibration sequence transmission and data transmission process in an air interface calibration process according to embodiments of the present application;

[0033] Figure 19 is a schematic diagram of an implementation principle of an air interface calibration process according to embodiments of the present application;

[0034] Figure 20 is a structure diagram of a network device according to embodiments of the present application;

[0035] Figure 21 is a structure diagram of an air interface calibration device of an indoor distributed system according to embodiments of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the scope of the present application.

[0037] That is, the term "and / or" in the embodiments of the present application describes the association relationship of the associated objects, and indicates that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0038] For ease of understanding, the terms involved in the present application are first introduced.

[0039] 1. Air interface calibration.

[0040] The air interface calibration obtains the difference of the transmission-reception phase difference between different channels by transmitting and receiving calibration sequences between multiple channels (or antennas) to each other, compensates for the corresponding difference in the downlink signal transmission or reception process, achieves the effect that the reception end of different channels and the transmission end have consistent phase differences, and thus implements downlink non-codebook beamforming transmission.

[0041] Taking the transmission of calibration sequences between two antennas (such as antenna 1 and antenna 2) to each other as an example, for the kth subcarrier (or frequency domain sample, frequency point) in the bandwidth occupied by the calibration sequence, it is assumed that the channel estimation (or channel gain or channel response) of the calibration sequence transmitted by antenna 2 and received by antenna 1 is represented as: H 2→1 (k), and the channel estimation of the calibration sequence transmitted by antenna 1 and received by antenna 2 is represented as: H 1→2 (k), the transmission-reception phase difference calibration factor (that is, the phase offset calibration factor) C between antenna 1 and antenna 2 can be obtained by point division:

[0042] Taking antenna 1 as the reference: C1 = 1, for the kth subcarrier (or frequency domain sample), the phase offset calibration factor C2 of antenna 2 is:

[0043]

[0044] wherein, H TX,2 (k) represents the phase offset introduced by the transmission end of antenna 2; H AIR,(2,1) (k) represents the channel gain or channel response of the air interface channel between antenna 2 and antenna 1 for the kth subcarrier; H RX,1 (k) represents the phase offset introduced by the reception end of antenna 1 for the kth subcarrier; and the reverse expression is the same. TX,1(k) represents the phase offset introduced by the transmitting end of antenna 1 at the kth subcarrier; H AIR,(1,2) (k) represents the channel gain or channel response of the air interface channel between antenna 1 and antenna 2 at the kth subcarrier; H RX,2 (k) represents the phase offset introduced by the receiving end of antenna 2 at the kth subcarrier.

[0045] In formula (1), the channel gain H AIR,(2,1) (k) and H AIR,(1,2) (k) are the same, so they can be eliminated.

[0046] After obtaining the phase offset calibration factor C2 of antenna 2, compensation of the factor C2 can be performed at the receiving end or the transmitting end of antenna 2 to ensure that the transmission and reception phase differences of antenna 1 and antenna 2 are consistent, and are all aligned to If the compensation is performed at the transmitting end, the compensation is performed at the last step of baseband signal processing at the BBU side.

[0047] It should be noted that, since the transmission and reception phase differences of different subcarriers (or frequency domain samples, frequency points) vary in frequency, the subcarrier k needs to traverse the entire bandwidth occupied by the calibration sequence, but all REs (Resource Element) do not need to be traversed, and one RE can be extracted in every several REs in the frequency domain for measurement, for example, RE6 in the following formula can be extracted for measurement. Figure 1 The time domain position of the transmission calibration sequence can be a Gp (Guard Period) symbol at which uplink and downlink are switched.

[0048] wherein, Figure 1 RB in the formula is an abbreviation of Resource Block.

[0049] It should be further noted that the calibration method of more antennas, or the calibration method between different RRUs, is the same as the calibration method of two antennas. For example, air interface calibration between multiple RRUs needs to be performed on the basis of alignment of multiple channels (i.e., multiple antennas inside the RRU) inside the RRU, and one channel of each RRU is used as a representative to exchange calibration sequences with other RRUs to obtain a phase offset calibration factor between the RRUs. The phase offset calibration factor between the RRUs obtained by a single channel can be used for all channels inside the RRU, for example, for any one channel inside the RRU, the phase offset calibration factor between the RRUs can be multiplied by the phase offset calibration factor of the channel inside the RRU to achieve the effect of alignment of all channels inside the RRU and between the RRUs.

[0050] 2, Hub merging.

[0051] In the scenario where RRU and BBU are directly connected, the number of RRUs is 4 and each RRU contains 4 antennas. The structure of the direct connection scenario between RRU and BBU can be as follows: Figure 2 As shown in the figure, each channel (i.e., antenna) under each RRU is directly connected to a channel of the BBU. The BBU needs to process the uplink data of the total number of channels under all RRUs and can independently control the downlink transmission signal of each channel in each RRU. This requires higher processing power of the BBU when the RRU deployment density is high, and the deployment cost is also high.

[0052] Hub merging is a common deployment method in indoor distributed systems. By introducing a hub node between the BBU and RRU, the hub merges the uplink signals from multiple RRUs and distributes the downlink signals to different RRUs, enabling flexible deployment of indoor distributed systems. The channel between the hub and the BBU is typically called a "logical channel," while the channel between the hub and the RRU is typically called a "physical channel."

[0053] Assume that there are two hubs, each connected to four RRUs, and different hubs do not overlap. The structure of the hub merging scenario can be as follows: Figure 3 shown.

[0054] exist Figure 3 In the process, the Hub directly accumulates the digital signals of the uplink signals of multiple RRUs (i.e., pico). For example, the received signal of the physical channel 1 of pico1 is recorded as the received signal RX 1,1 , the received signal of physical channel 2 is recorded as RX 1,2 , the received signal of physical channel 3 is recorded as RX 1,3 , the received signal of physical channel 4 is recorded as RX 1,4 ;Record the received signal of physical channel 1 of pico2 as received signal RX 2,1 , the received signal of physical channel 2 is recorded as RX 2,2 , the received signal of physical channel 3 is recorded as RX 2,3 , the received signal of physical channel 4 is recorded as RX 2,4 ;Record the received signal of physical channel 1 of pico3 as received signal RX 3,1 , the received signal of physical channel 2 is recorded as RX 3,2 , the received signal of physical channel 3 is recorded as RX 3,3 , the received signal of physical channel 4 is recorded as RX 3,4 ;Record the received signal of physical channel 1 of pico4 as received signal RX 4,1 , the received signal of physical channel 2 is recorded as RX 4,2 , the received signal of physical channel 3 is recorded as RX4,3 , the received signal of physical channel 4 is recorded as RX 4,4 , then for Hub1, the uplink signals of the four logical channels sent by Hub1 to the BBU side are formed by combining the uplink signals of multiple physical channels, which are:

[0055] The uplink signal of the first logical channel is: RX1 = RX 1,1 +RX 2,1 +RX 3,1 +RX 4,1 ;

[0056] The uplink signal of the second logical channel is: RX2 = RX 1,2 +RX 2,2 +RX 3,2 +RX 4,2 ;

[0057] The uplink signal of the third logical channel is: RX3 = RX 1,3 +RX 2,3 +RX 3,3 +RX 4,3 ;

[0058] The uplink signal of the fourth logical channel is: RX4 = RX 1,4 +RX 2,4 +RX 3,4 +RX 4,4 .

[0059] The Hub can also send data to multiple RRUs (i.e. Figure 3 pico) distributes downlink signals, for example, BBU to Figure 3 The downlink data of the four logical channels sent by Hub1 are TX1, TX2, TX3, and TX4 respectively. The downlink data received by the four physical channels of pico1 are TX1, TX2, TX3, and TX4 respectively; the downlink data received by the four physical channels of pico2 are TX1, TX2, TX3, and TX4 respectively; and so on. In other words, the downlink data received by each RRU is consistent.

[0060] Currently, the common method for phase offset calibration is to perform phase offset calibration by sending calibration sequences over the air interface within and between RRUs. In scenarios where hub channel merging is not performed between RRUs (i.e., the RRUs are directly connected to the BBU), this calibration function can be performed directly on the BBU side, and the phase offset obtained after calibration can be directly compensated using the baseband signal on the BBU side, which is more convenient. However, in hub merging scenarios, since the calibration sequences sent between multiple RRUs are merged before reaching the BBU, the BBU side cannot obtain the independent channel phase offset information of each RRU before merging.

[0061] That is, in the related art, only for the scenario that each RRU is directly connected with the BBU, the BBU acquires the uplink signal of each channel inside each RRU, and independently controls the downlink transmission of each channel inside each RRU, and the measurement of the phase offset calibration factor (for example, the phase offset calibration factor of each channel (that is, antenna) is measured by using formula (1)), and the compensation are all completed by the BBU side. However, the related art does not involve how to apply in the Hub merging scenario. If the four logical channels under the Hub are directly applied to the existing scheme as the four channels under a single RRU, formula (2) can be used to calculate the phase offset calibration factor C2 of antenna 2:

[0062]

[0063]

[0064] wherein H DL(2→1) (k) represents the channel estimation (or channel gain or channel response) of the downlink link transmitted by antenna 2 and received by antenna 1 for the kth subcarrier in the occupied bandwidth of the calibration sequence; H UL(1→2) (k) represents the channel estimation (or channel gain or channel response) of the uplink link transmitted by antenna 1 and received by antenna 2 for the kth subcarrier.

[0065] wherein H TX,rru1ant2 (k) represents the phase offset introduced by the transmitting end of antenna 2 of RRU1 for the kth subcarrier; H AIR,(rru1ant2,rru1ant1 )(k) represents the channel gain or channel response of the air interface channel between antenna 2 of RRU1 and antenna 1 of RRU1 for the kth subcarrier; H RX,rru1ant1 (k) represents the phase offset introduced by the receiving end of antenna 1 of RRU1 for the kth subcarrier.

[0066] wherein H TX,rru2ant2 (k) represents the phase offset introduced by the transmitting end of antenna 2 of RRU2 for the kth subcarrier; H AIR,(rru2ant2,rru2ant1) (k) represents the channel gain or channel response of the air interface channel between antenna 2 of RRU2 and antenna 1 of RRU2 for the kth subcarrier; H RX,rru2ant1 (k) represents the phase offset introduced by the receiving end of antenna 1 of RRU2 for the kth subcarrier.

[0067] wherein H TX,rru1ant1 (k) represents the phase offset introduced by the transmitting end of antenna 1 of RRU1 for the kth subcarrier; H AIR,(rru1ant1,rru1ant2) (k) represents the channel gain or channel response of the air interface channel between antenna 1 of RRU1 and antenna 2 of RRU1 for the kth subcarrier; H RX,rru1ant2(k) represents the phase offset introduced by the receiving end of the antenna 2 of the RRU 1 for the kth subcarrier.

[0068] wherein H TX,rru2ant1 (k) represents the phase offset introduced by the transmitting end of the antenna 1 of the RRU 2 for the kth subcarrier; H AIR,(rru2ant1,rru2ant2 (k) represents the channel gain or channel response of the air interface channel between the antenna 1 of the RRU 2 and the antenna 2 of the RRU 2 for the kth subcarrier; H RX,rru2ant2 (k) represents the phase offset introduced by the receiving end of the antenna 2 of the RRU 2 for the kth subcarrier.

[0069] Although H AIR,(rru1ant2,rru1ant1) (k) in D is equal to H AIR,(rru1ant1,rru1ant2) (k) in B, and H AIR,(rru2ant2,rru2ant1) (k) in E is equal to H AIR,(rru2ant1,rru2ant2) (k) in A, but due to the accumulation of the Hub, it cannot be directly divided as formula (1), so the transceiving phase difference between channels cannot be aligned through C2 in formula (2), and the uplink and downlink channel reciprocity cannot be ensured through air interface calibration, and the effect of non-codebook transmission cannot be ensured.

[0070] And the existing calibration scheme between RRUs only involves how to mutually send calibration sequences and related calibration processing between 2 RRUs, and does not involve the sending order and related strategies in the calibration process of more RRUs in the actual networking scenario.

[0071] In view of at least one of the above problems, the air interface calibration method, device, network equipment and medium of the indoor distributed system are provided in the present application.

[0072] The air interface calibration method, device, network equipment and medium of the indoor distributed system of the present embodiment are described below with reference to the accompanying drawings. Before specifically describing the embodiments of the present application, in order to facilitate understanding, first introduce the commonly used technical words:

[0073] The set sending mode refers to a pre-set sending mode. The set sending mode includes but is not limited to frequency division multiplexing sending mode, time division multiplexing sending mode, code division multiplexing sending mode, etc.

[0074] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to each Hub.

[0075] As an example, the number of Hubs is 2, each Hub is connected to 4 RRUs, and different Hub non-cross coverage is exemplified. The structure of the indoor distributed system can be as shown in Figure 3 .

[0076] As another example, taking the number of Hubs as multiple, and each Hub being connected with 4 RRUs, the structure of the indoor distributed system can be as shown in Figure 4

[0077] The first set threshold refers to a pre-set SNR (SIGNAL-NOISE RATIO) threshold.

[0078] The second set threshold refers to a pre-set distance threshold.

[0079] The third set threshold refers to a pre-set index threshold.

[0080] Figure 5 FIG. 1 is a flow diagram of a first air interface calibration method of an indoor distributed system provided by an embodiment of the present application.

[0081] The air interface calibration method of the indoor distributed system of the embodiment of the present application can be applied to a network device. For example, it can be applied to a BBU in the network device, or it can be applied to a Hub in the network device.

[0082] ​In some embodiments, the network device is a base station. A base station can include multiple cells that serve terminals. Depending on the application, the base station can also be referred to as an access point, or can be a device that communicates with wireless terminals over one or more sectors on an air interface, or other names. The base station can be used to exchange received air frames with Internet Protocol (IP) packets, as a router between the wireless terminals and the rest of the access network, which can include an Internet Protocol (IP) communication network. The base station can also coordinate the management of the properties of the air interface. For example, the base station involved in the embodiments of the present application can be a base station (BTS) in the Global System for Mobile Communications (GSM) or Code Division Multiple Access (CDMA), or a base station (NodeB) in Wide-band Code Division Multiple Access (WCDMA), or an evolved base station (eNB or e-NodeB) in the long term evolution (LTE) system, or a 5G base station (gNB) in the next generation system (5G network architecture), or a home evolved base station (HeNB), a relay node, a femto, a pico, etc., which are not limited in the embodiments of the present application. In some network structures, the base station can include a centralized unit (CU) node and a distributed unit (DU) node, and the centralized unit and the distributed unit can also be geographically separated.

[0083] The terminal device may be a device that provides voice and / or data connectivity to a user, a handheld device with wireless connection capabilities, or other processing devices connected to a wireless modem. The names of terminal devices may vary in different systems. For example, in a 5G system, a terminal device may be referred to as a user equipment (UE). A wireless terminal device may communicate with one or more core networks (CNs) via a radio access network (RAN). A wireless terminal device may be a mobile terminal device, such as a mobile phone (or "cellular" phone) and a computer with a mobile terminal device. For example, a portable, pocket-sized, handheld, computer-built-in, or vehicle-mounted mobile device may exchange voice and / or data with a radio access network. Examples include personal communication service (PCS) phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, and personal digital assistants (PDAs). The wireless terminal device may also be referred to as a system, a subscriber unit, a subscriber station, a mobile station, a mobile station, a remote station, an access point, a remote terminal device, an access terminal device, a user terminal device, a user agent, or a user device, but is not limited in the embodiments of the present application.

[0084] like Figure 5 As shown, the air interface calibration method of the indoor distributed system may include the following steps:

[0085] Step S501 : Calibrate and measure a first calibration sequence sent between multiple antennas in the same RRU via a set transmission mode to obtain a first phase offset calibration factor for each antenna in the same RRU. The first calibration sequence is sent from the BBU to the RRU via the Hub.

[0086] In the embodiment of the present application, the multiple antennas in the same RRU can transmit the first calibration sequence to each other by setting the transmission mode, so that the first calibration sequence transmitted by the multiple antennas to each other can be calibrated and measured to obtain the phase offset calibration factor (or phase offset calibration coefficient, denoted as the first phase offset calibration factor in the present application) of each antenna in the multiple antennas.

[0087] In step S502, the phase offset of each antenna in the same RRU is calibrated based on the first phase offset calibration factor of each antenna in the same RRU.

[0088] In the embodiment of the present application, the phase offset of each antenna in the same RRU can be calibrated based on the first phase offset calibration factor of each antenna in the same RRU.

[0089] In any one of the embodiments of the present application, the phase offset calibration mode can be, for example, for any one antenna in the same RRU, it can be judged whether the downlink signal transmitted by the BBU to the same RRU is a frequency domain signal, if the downlink signal transmitted by the BBU to the same RRU is a frequency domain signal, the phase offset compensation of the antenna can be directly based on the first phase offset calibration factor of the antenna; and if the downlink signal transmitted by the BBU to the same RRU is a time domain signal, the time offset information and the phase offset information can be extracted from the first phase offset calibration factor of the antenna based on the existing mode, so that the antenna can be calibrated and compensated based on the time offset information and the phase offset information.

[0090] In step S503, the second calibration sequence transmitted by different RRUs to each other is calibrated and measured to obtain the second phase offset calibration factor of each RRU, and the phase offset of each antenna in each RRU is calibrated based on the second phase offset calibration factor of each RRU.

[0091] The second calibration sequence is transmitted by the BBU to the RRU through the Hub. Only one antenna in each RRU transmits the second calibration sequence, for example, one antenna in each RRU can be selected as a representative antenna (for example, the representative antenna can be a designated antenna, or it can also be any one antenna), so that the second calibration sequence can be transmitted by the representative antennas in different RRUs to each other.

[0092] In the embodiment of the present application, the second calibration sequence transmitted by the representative antennas in different RRUs to each other can be calibrated and measured to obtain the phase offset calibration factor of the representative antenna in each RRU, and for any one representative antenna, the phase offset calibration factor of the representative antenna can be taken as the second phase offset calibration factor of the RRU to which the representative antenna belongs.

[0093] In the embodiments of the present application, the phase offset calibration can be performed on all antennas in each RRU according to the second phase offset calibration factor of the RRU.

[0094] In any of the embodiments of the present application, the phase offset calibration manner can be, for example, that for any antenna, the target phase offset calibration factor of the antenna can be determined according to the product of the second phase offset calibration factor of the RRU to which the antenna belongs and the first phase offset calibration factor of the antenna, so that the phase offset calibration can be performed on the antenna based on the target phase offset calibration factor of the antenna.

[0095] As an example, in the case where the downlink signal sent by the BBU to the RRU to which the antenna belongs is a frequency domain signal, the phase offset compensation can be directly performed on the antenna based on the target phase offset calibration factor of the antenna; and in the case where the downlink signal sent by the BBU to the RRU to which the antenna belongs is a time domain signal, the time offset information and the phase offset information can be extracted from the target phase offset calibration factor of the antenna based on the existing manner, so that the calibration compensation can be performed on the antenna based on the time offset information and the phase offset information.

[0096] The air interface calibration method of the indoor distributed system in the embodiments of the present application can realize the targeted or independent calibration compensation of different antennas in the same RRU by using the setting transmission manner to mutually send calibration sequences between different antennas in the same RRU, and can realize the targeted or independent calibration compensation of each antenna in different RRUs by using the setting transmission manner to mutually send calibration sequences between different RRUs, so as to not only reduce the error and distortion of signals in the transmission process and improve the communication quality, but also widen the application scenarios of the air interface calibration and improve the applicability of the method.

[0097] The embodiments of the present application provide another air interface calibration method, Figure 6 is a flowchart of the second air interface calibration method of the indoor distributed system provided by the embodiments of the present application. It should be noted that the air interface calibration method can be executed independently, or can be executed in combination with any of the embodiments or the possible implementation manners in the embodiments of the present application, or can be executed in combination with any of the technical solutions in the related art, and the embodiments of the present application do not limit this.

[0098] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to each Hub.

[0099] The plurality of RRUs connected to the same Hub occupy different REs, and the first calibration sequence sent by each antenna in the same RRU is a calibration sequence generated by the BBU according to the first RE occupied by the same RRU.

[0100] As an example, taking an example of a Hub connected with 4 RRUs (RRU1, RRU2, RRU3 and RRU4 respectively), the REs occupied by the 4 RRUs can be as shown in Figure 7 , i.e., RRU1 occupies RE3, RRU2 occupies RE6, RRU3 occupies RE9, and RRU4 occupies RE12.

[0101] In the embodiments of the present application, each RRU can generate a first calibration sequence corresponding to each RRU according to the RE occupied by each RRU, and send the first calibration sequence corresponding to each RRU to the Hub.

[0102] The Hub can agree with the BBU on the RRU corresponding to each calibration sequence, so that the Hub can send each first calibration sequence to the corresponding RRU.

[0103] As shown in Figure 6 , in the case of setting the transmission mode as a frequency division multiplexing transmission mode, the air interface calibration method of the indoor distributed system can include the following steps:

[0104] Step S601, in the case of reaching the ith moment, sending a first calibration sequence to the remaining antennas through the ith antenna in the same RRU.

[0105] In the embodiments of the present application, each time the ith moment is reached, a first calibration sequence can be sent to the remaining antennas through the ith antenna in the same RRU. Wherein, i is a positive integer, the first calibration sequence is sent by the ith antenna using the first RE, and the remaining antennas are the antennas in the same RRU except the ith antenna.

[0106] Step S602, performing calibration measurement on the first calibration sequence received by the remaining antennas and the first calibration sequence received by the ith antenna at different moments to obtain a first phase offset calibration factor of each antenna in the same RRU.

[0107] In the embodiments of the present application, calibration measurement can be performed on the first calibration sequence received by the remaining antennas and the first calibration sequence received by the ith antenna at different moments to obtain a first phase offset calibration factor of each antenna in the same RRU.

[0108] As an example, taking an example of the RE occupied by each RRU as shown in Figure 7 , and the structure of the indoor distributed system as shown in Figure 8As shown, and each RRU contains 4 antennas for example, for any one RRU, such as RRU1, at time 1, Ant1 in RRU1 can occupy RE3 to send the first calibration sequence to Ant2, Ant3 and Ant4 in RRU1; at time 2, Ant2 in RRU1 can occupy RE3 to send the first calibration sequence to Ant1, Ant3 and Ant4 in RRU1; at time 3, Ant3 in RRU1 can occupy RE3 to send the first calibration sequence to Ant1, Ant2 and Ant4 in RRU1; at time 4, Ant4 in RRU1 can occupy RE3 to send the first calibration sequence to Ant1, Ant2 and Ant3 in RRU1.

[0109] For the 2nd time, based on Ant1, according to the first calibration sequence sent by Ant2 to Ant1 at the 2nd time and the first calibration sequence sent by Ant1 to Ant2 at the 1st time, the phase offset calibration factor C2 corresponding to Ant2 is calculated according to formula (1), so that Ant2 can be subsequently phase offset calibrated based on C2.

[0110] For the 3rd time, based on Ant1, according to the first calibration sequence sent by Ant3 to Ant1 at the 3rd time and the first calibration sequence sent by Ant1 to Ant3 at the 1st time, the phase offset calibration factor C3 of Ant3 is calculated according to formula (1), so that Ant3 can be subsequently phase offset calibrated based on C3; and based on Ant2, according to the first calibration sequence sent by Ant2 to Ant3 at the 2nd time and the first calibration sequence sent by Ant3 to Ant2 at the 3rd time, the phase offset calibration factor C3 of Ant3 is calculated, so that Ant3 can be subsequently phase offset calibrated again based on C3.

[0111] For the 4th moment, according to the first calibration sequence sent by Ant4 to Ant1 at the 4th moment and the first calibration sequence sent by Ant1 to Ant4 at the 1st moment, the phase offset calibration factor C4 of Ant4 is calculated according to formula (1) based on Ant1 as a reference, so that the phase offset calibration of Ant4 can be performed based on C4 subsequently; and according to the first calibration sequence sent by Ant4 to Ant2 at the 4th moment and the first calibration sequence sent by Ant2 to Ant4 at the 2nd moment, the C4 of Ant4 is calculated based on Ant2 as a reference, so that the phase offset calibration of Ant4 can be performed based on C4 again subsequently; and according to the first calibration sequence sent by Ant4 to Ant3 at the 4th moment and the first calibration sequence sent by Ant3 to Ant4 at the 3rd moment, the C4 of Ant4 is calculated based on Ant3 as a reference, so that the phase offset calibration of Ant4 can be performed based on C4 again subsequently.

[0112] In step S603, the phase offset calibration of each antenna in the same RRU is performed based on the first phase offset calibration factor of each antenna in the same RRU.

[0113] In step S604, the second calibration sequence sent between different RRUs is measured to obtain the second phase offset calibration factor of each RRU, and the phase offset calibration of each antenna in each RRU is performed based on the second phase offset calibration factor of each RRU.

[0114] The second calibration sequence is sent by the BBU to the RRU through the Hub. For example, the second calibration sequence can be the same as the first calibration sequence sent by the representative antenna in the RRU.

[0115] The explanation of steps S603 to S604 can be referred to the related description in any embodiment of the present application, which will not be repeated here.

[0116] The air interface calibration method of the indoor distributed system in the embodiment of the present application can use frequency division multiplexing transmission between different antennas in the same RRU to send the first calibration sequence, which can improve the effectiveness of calibration measurement and calibration compensation between different antennas in the RRU.

[0117] The frequency division multiplexing transmission in the embodiment will be described in detail below in combination with embodiment A. Figure 6

[0118] ​Embodiment A: The frequency domain REs of the calibration sequences sent by different RRUs are staggered, so that even if the inter-RRU time domain signals are accumulated and combined at the Hub side, and the signals are demodulated to the frequency domain signals by OFDM (Orthogonal Frequency Division Multiplexing) at the BBU side, the transmission signals between different RRUs can still be distinguished. Thus, for each RRU, the phase offset calibration coefficient can be calculated according to formula (1) in the existing scheme.

[0119] For example, the REs occupied by the calibration sequences sent by different RRUs can be as shown in FIG. 1. Figure 7 The mutual transmission of the calibration sequences between the multiple antennas inside an RRU can follow the existing scheme, that is, the time is staggered and the mutual transmission is performed in turn (as shown in FIG. 2). Figure 8 The bidirectional channel estimation can be calculated, and then the point division processing is performed according to formula (1) to divide the channel gain of the air interface channel and obtain the phase offset calibration factor of each antenna (that is, between channels). The phase offset calibration factor obtained at different RE positions corresponds to different RRUs.

[0120] The uplink signals of different Hubs are not combined, and the same time-frequency resources can be reused. When performing the phase offset calibration for each antenna inside an RRU, the transmission power of the antenna should be controlled below a certain level to ensure that the antenna receiving the calibration sequence is not saturated, and the mutual interference of the reuse of the same time-frequency resources between Hubs during the air interface calibration can also be avoided.

[0121] Compared with the existing process, the following adjustments need to be made:

[0122] The BBU generates calibration sequences: the calibration sequences sent by different RRUs are different, and the BBU needs to generate the corresponding calibration sequences (or time domain calibration signals, downlink signals, downlink calibration signals) according to the REs occupied by each RRU and deliver them to the Hub.

[0123] The Hub transmission end: the calibration sequences sent by different RRUs are different, and the Hub needs to agree with the BBU on the RRU corresponding to the calibration sequence, and the calibration sequence is only sent by the specific RRU.

[0124] The Hub receiving end: the multi-path signals are combined according to the existing channel combination method.

[0125] Taking the BBU as the execution subject of the embodiments of the present application, for the BBU receiving end: the phase offset calibration factor of each antenna in different RRUs is obtained at different RE positions of the uplink signal.

[0126] The embodiments of the present application provide another air interface calibration method, Figure 9is a flow diagram of a third air interface calibration method of an indoor distributed system provided by an embodiment of the present application. It should be noted that the air interface calibration method can be executed independently, or can be executed in combination with any embodiment or possible implementation manner of the embodiments in the present application, or in combination with any technical solution in the related art, and the embodiments of the present application do not make any limitation in this regard.

[0127] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to each Hub.

[0128] The REs occupied by different antennas in the same RRU are different, and the REs occupied by the antennas of the same port in the plurality of RRUs connected to the same Hub are the same. For example, Ant1 in RRU1 and Ant1 in RRU2 occupy the same RE.

[0129] For any antenna, the first calibration sequence sent by the antenna is a calibration sequence generated by the BBU according to the second RE occupied by the antenna.

[0130] As an example, taking the case where the Hub is connected to four RRUs (RRU1, RRU2, RRU3, and RRU4) as an example, the REs occupied by the four RRUs can be as shown in Figure 10 , that is, Ant1 occupies RE4, Ant2 occupies RE8, Ant3 occupies RE12, and Ant4 occupies RE4, RE8, and RE12 at the same time.

[0131] In the embodiments of the present application, the RRU can generate a first calibration sequence corresponding to each antenna according to the RE occupied by each antenna, and send the first calibration sequence corresponding to each antenna to the Hub. The Hub can send each first calibration sequence to the corresponding antenna.

[0132] As shown in Figure 9 , in the case where the transmission mode is set to the time division multiplexing transmission mode, the air interface calibration method of the indoor distributed system can include the following steps:

[0133] In step S901, taking the jth antenna in the same RRU as a reference, the first calibration sequence is sent to the jth antenna through other antennas using the second REs occupied by the other antennas.

[0134] In the embodiments of the present application, in the case where the sending time of the first calibration sequence is reached, taking the jth antenna in the same RRU as a reference, the first calibration sequence is sent to the jth antenna through other antennas using the second REs occupied by the other antennas. Wherein, j is a positive integer, and the other antennas are the antennas in the same RRU except the jth antenna.

[0135] As an example, the REs occupied by each antenna are as shown in Figure 10 The structure of the indoor distributed system is as shown in Figure 11 The example is that each RRU contains 4 antennas, for any one RRU, such as RRU1, assuming that Ant4 is the reference, at the sending time of the first calibration sequence, the first calibration sequence can be sent to Ant4 through Ant1 occupying RE4, through Ant2 occupying RE8, and through Ant3 occupying RE12. Ant4, as the receiving antenna, receives the superimposed signals of all antennas.

[0136] At step S902, the first calibration sequence is sent to other antennas through the second RE occupied by the jth antenna using other antennas.

[0137] In the embodiment of the present application, at the sending time of the second calibration sequence, the first calibration sequence can be sent to other antennas through the second RE occupied by the jth antenna using other antennas.

[0138] Still taking the above example as an example, at the sending time of the second calibration sequence, the first calibration sequence can be sent to Ant1 through Ant4 occupying RE4, to Ant2 through Ant4 occupying RE8, and to Ant3 through Ant4 occupying RE12 (the REs occupied by Ant4 when sending the first calibration sequence can be as shown in Figure 12 Ant1, Ant2 and Ant3 respectively receive the first calibration sequence.

[0139] At step S903, calibration measurement is performed on the first calibration sequence received by the jth antenna and the first calibration sequence received by other antennas to obtain the first phase offset calibration factor of other antennas.

[0140] In the embodiment of the present application, calibration measurement can be performed on the first calibration sequence received by the jth antenna and the first calibration sequence received by other antennas to obtain the first phase offset calibration factor of other antennas.

[0141] Still taking the above example as an example, taking the execution subject as BBU as an example, at the sending time of the first calibration sequence, the first calibration sequence at RE4 position, RE8 position and RE12 position can be separated through OFDM demodulation at the BBU side, and is respectively used to calculate the channel estimation H 1→4 of Ant1->Ant4, the channel estimation H 2→4 of Ant2->Ant4, and the channel estimation H 3→4 of Ant3->Ant4.

[0142] At the sending time of the second calibration sequence, the BBU can obtain the reverse channel estimation H 4→1 (Ant4->Ant1 channel estimation), H 4→2 (Ant4->Ant2 channel estimation), H 4→3 (Ant4->Ant3 channel estimation). The BBU can use the existing scheme (such as formula (1)) to do point division processing on the bidirectional channel estimation, and divide the channel gain of the air interface channel to obtain the phase offset calibration factor of each antenna (i.e., channel), that is, the phase offset calibration factor C1 of Ant1, the phase offset calibration factor C2 of Ant2, and the phase offset calibration factor C3 of Ant3 (calibrated with Ant4 as the reference).

[0143] Step S904, based on the first phase offset calibration factor of each antenna in the same RRU, performing phase offset calibration on each antenna in the same RRU.

[0144] Step S905, performing calibration measurement on the second calibration sequence transmitted between different RRUs, obtaining the second phase offset calibration factor of each RRU, and performing phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU.

[0145] The second calibration sequence is transmitted by the BBU to the RRU through the Hub. For example, the second calibration sequence can be the same as the first calibration sequence transmitted by the representative antenna in the RRU.

[0146] The explanation of steps S904 to S905 can be referred to the related description in any embodiment of the present application, which will not be repeated here.

[0147] The air interface calibration method of the indoor distributed system in the embodiments of the present application can use time division multiplexing transmission between different antennas in the same RRU to transmit the first calibration sequence, which can improve the effectiveness of calibration measurement and calibration compensation between different antennas in the RRU.

[0148] The time division multiplexing transmission in the embodiments will be described in detail below in combination with Embodiment B. Figure 9

[0149] Embodiment B: The frequency domain REs of the calibration sequence transmitted by different antennas are staggered, and the calibration processes of different RRUs under the same Hub are staggered by time division.

[0150] For example, taking the BBU as an example of the execution subject of Embodiment B, at the sending time of the first calibration sequence to a certain RRU, taking antenna 4 as the reference, Ant1-3 as the transmitting antennas, and respectively transmitting the first calibration sequence in the frequency domain REs of 4, 8, and 12. Figure 10 ​The first calibration sequence is sent at the positions of RE4, RE8, and RE12, and Ant4 is used as a receiving antenna to receive the superimposed signals of all antennas. The BBU separates the first calibration sequence at the positions of RE4, RE8, and RE12 through OFDM demodulation and uses them to calculate the channel estimation H of Ant1->Ant4 respectively. 1→4 、Channel estimation H of Ant2->Ant4 2→4 、Channel estimation H of Ant3->Ant4 3→4 .

[0151] The reverse logic is the same: when the second calibration sequence is sent, Ant4 is used as the transmitting antenna, and Figure 12 The positions RE4, RE8, and RE12 shown in the figure send the first calibration sequence, and Ant1-3 serve as receiving antennas to receive the first calibration sequence respectively. The BBU obtains the reverse channel estimation H through the received signals at the positions RE4, RE8, and RE12 respectively. 4→1 、H 4→2 、H 4→3 .

[0152] The BBU can continue to use the existing solution (such as formula (1)), perform dot division on the bidirectional channel estimation, reduce the channel gain of the air interface channel, and obtain the phase offset calibration factors C1, C2, and C3 for each antenna (i.e., between channels) (aligned with Ant4 as the reference).

[0153] Compared with the existing process, the following adjustments need to be made:

[0154] BBU generates calibration sequence: The BBU can generate a calibration sequence (also called time domain calibration signal, downlink signal, downlink calibration signal) corresponding to each antenna based on the REs occupied by each antenna, and send it to the Hub.

[0155] Hub transmitter: During the calibration time of a certain RRU, the calibration sequence is only sent to that RRU.

[0156] Hub receiving end: During the calibration time of a certain RRU, the Hub only sends the uplink signal of the RRU to the BBU on the logical channel, instead of merging the data of multiple physical channels as for regular service data.

[0157] For the BBU receiving end: at different RE positions of the uplink signal, the phase deviation calibration factors of different antennas in the RRU are obtained respectively.

[0158] This embodiment of the application provides another air interface calibration method. Figure 13is a flow diagram of a method for air interface calibration of a fourth indoor distributed system provided in embodiments of the present application. It should be noted that the method for air interface calibration can be performed independently, or can be performed in combination with any of the embodiments or possible implementation manners in the embodiments of the present application, or can be performed in combination with any of the related technologies, and the embodiments of the present application do not make any limitation in this regard.

[0159] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to each Hub.

[0160] The plurality of RRUs connected to the same Hub occupy different cyclic shifts, and the plurality of antennas in the same RRU occupy different REs.

[0161] For any antenna, the first calibration sequence sent by the antenna is a calibration sequence generated by the BBU according to the cyclic shift occupied by the RRU to which the antenna belongs and the third RE occupied by the antenna.

[0162] In embodiments of the present application, the BBU can generate a calibration sequence for each RRU according to the cyclic shift occupied by each RRU, generate a first calibration sequence corresponding to each antenna according to the calibration sequence of each RRU and the RE occupied by each antenna in each RRU, and send the first calibration sequence corresponding to each antenna to the Hub, so that the Hub can send each first calibration sequence to the corresponding antenna.

[0163] As shown in Figure 13 , in the case of setting the transmission mode as a code division multiplexing transmission mode, the method for air interface calibration of the indoor distributed system can include the following steps:

[0164] In step S1301, the first calibration sequence is sent to the kth antenna in the same RRU through other antennas using the third RE occupied by each of the other antennas.

[0165] In embodiments of the present application, in the case of reaching the sending time of the first calibration sequence, the first calibration sequence can be sent to the kth antenna in the same RRU through other antennas using the third RE occupied by each of the other antennas. Wherein k is a positive integer, and the other antennas are antennas other than the kth antenna in the same RRU.

[0166] In step S1302, the first calibration sequence is sent to the other antennas through the kth antenna using the third RE occupied by the other antennas.

[0167] In the embodiment of the present application, when the sending time of the second calibration sequence is reached, the first calibration sequence can be sent to other antennas by the kth antenna using the third RE occupied by other antennas.

[0168] In step S1303, calibration measurement is performed on the first calibration sequence received by the kth antenna and the first calibration sequence received by other antennas to obtain the first phase offset calibration factor of other antennas.

[0169] In the embodiment of the present application, calibration measurement can be performed on the first calibration sequence received by the kth antenna and the first calibration sequence received by other antennas to obtain the first phase offset calibration factor of other antennas.

[0170] As an example, the structure of an indoor distributed system is shown in FIG. 8, and each RRU contains four antennas, and the calculation of the phase offset calibration factor of each antenna is similar to that of the embodiment B. Figure 14

[0171] In step S1304, the phase offset calibration is performed on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU.

[0172] In step S1305, calibration measurement is performed on the second calibration sequence sent between different RRUs to obtain the second phase offset calibration factor of each RRU, and the phase offset calibration is performed on each antenna in each RRU based on the second phase offset calibration factor of each RRU.

[0173] The second calibration sequence is sent by the BBU to the RRU through the Hub. For example, the second calibration sequence can be the same as the first calibration sequence sent by the representative antenna in the RRU.

[0174] The explanation of steps S1304 to S1305 can be referred to the related description in any embodiment of the present application, and will not be repeated here.

[0175] The air interface calibration method of the indoor distributed system in the embodiment of the present application can use code division multiplexing transmission between different antennas in the same RRU to send the first calibration sequence to each other, which can improve the effectiveness of calibration measurement and calibration compensation between different antennas in the RRU.

[0176] The code division multiplexing transmission in the embodiment will be described in detail below in combination with the embodiment C. Figure 13

[0177] ​​Embodiment C: Similar to Embodiment B, the frequency domain REs of the calibration sequence transmitted by different antennas can be staggered, and the phase offset calibration of different RRUs under the same Hub uses different calibration sequences (which can be different cyclic shifts of ZC (Zadoff-Chu) sequences). In this way, the Hub can directly combine and process the signals when performing the combination of the received signals of the uplink calibration sequence, and send them to the BBU. The BBU can separate the calibration sequences of different RRUs by code division.

[0178] The following adjustments need to be made with respect to the existing process:

[0179] The BBU generates calibration sequences: The BBU can generate calibration sequences for each RRU according to the cyclic shift occupied by each RRU, and then generate calibration sequences (or time domain calibration signals, downlink signals, downlink calibration signals) corresponding to each antenna according to the RE occupied by each antenna, and send them to the Hub.

[0180] The Hub transmission end: sends the corresponding calibration sequence for each RRU.

[0181] Taking the BBU as the execution subject of the embodiments of the present application, for the BBU receiving end: different antennas are distinguished by different RE positions of the uplink signal, and the uplink signals of different RRUs are separated by calibration code, and the phase offset calibration factor of different antennas in each RRU is obtained according to the uplink signal of each RRU.

[0182] The embodiments of the present application provide another air interface calibration method, Figure 15 is a flowchart of the fifth air interface calibration method of the indoor distributed system provided by the embodiments of the present application. It should be noted that the air interface calibration method can be executed alone, or can be executed in combination with any embodiment or possible implementation manner in the embodiments of the present application, or can be executed in combination with any technical solution in the related art, and the embodiments of the present application do not limit this.

[0183] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to each Hub.

[0184] As shown in Figure 15 , the air interface calibration method of the indoor distributed system can include the following steps:

[0185] Step S1501: Determine whether the indoor distributed system meets the triggering condition of the air interface calibration. If yes, execute step S1502 and subsequent steps, if not, return to step S1501. The triggering condition of the air interface calibration is pre-set.

[0186] In any one of the embodiments of the present application, the triggering condition of the air interface calibration can include, but is not limited to, at least one of the following:

[0187] First, a set period is reached; wherein the period length of the set period is determined according to the measurement period of the phase drift between different antennas in the indoor distributed system. For example, the period length of the set period can be one day, several hours, etc.

[0188] Second, at least one RRU is added to the indoor distributed system.

[0189] Third, at least one RRU in the indoor distributed system is switched from an operating state to an off state.

[0190] Fourth, the deployment location of at least one RRU in the indoor distributed system is changed.

[0191] Fifth, at least one RRU in the indoor distributed system is switched from a power-off state to a power-on state.

[0192] Sixth, the first network performance index obtained by the indoor distributed system using a non-codebook technology is lower than the second network performance index obtained by the indoor distributed system using a codebook technology, and the difference between the first network performance index and the second network performance index is greater than a third set threshold. Wherein the first network performance index and the second network performance index are the same network performance index, including but not limited to the following indicators: data transmission rate, bit error rate, spectrum utilization, coverage, etc.

[0193] It should be noted that the third set threshold corresponding to different network performance indicators can be different.

[0194] Step S1502, the first calibration sequence transmitted by the multiple antennas in the same RRU through the set transmission mode is calibrated and measured to obtain the first phase offset calibration factor of each antenna in the same RRU.

[0195] Step S1503, based on the first phase offset calibration factor of each antenna in the same RRU, the phase offset calibration of each antenna in the same RRU is performed.

[0196] Step S1504, the second calibration sequence transmitted by the different RRUs is calibrated and measured to obtain the second phase offset calibration factor of each RRU, and based on the second phase offset calibration factor of each RRU, the phase offset calibration of each antenna in each RRU is performed.

[0197] Wherein, the first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

[0198] The explanation of steps S1502 to S1504 can be referred to the related description in any of the embodiments of the present application, which will not be repeated here.

[0199] The air interface calibration method of the indoor distributed system in the embodiments of the present application can only perform phase offset calibration measurement and calibration compensation for different antennas in the same RRU in the indoor distributed system and perform phase offset calibration measurement and calibration compensation for different RRUs when the indoor distributed system meets the triggering condition of air interface calibration, which can not only reduce the error and distortion of signals in the transmission process, but also reduce resource consumption.

[0200] The embodiments of the present application provide another air interface calibration method, Figure 16 is a flow diagram of a sixth air interface calibration method of an indoor distributed system provided by the embodiments of the present application. It should be explained that the air interface calibration method can be executed alone, or can be executed in combination with any of the embodiments or possible implementation manners in the embodiments of the present application, or can be executed in combination with any of the related technologies, and the embodiments of the present application do not make any limitation in this regard.

[0201] The indoor distributed system includes a BBU, at least one Hub connected with the BBU, and a plurality of RRUs connected with each Hub.

[0202] As shown in Figure 16 The air interface calibration method of the indoor distributed system can include the following steps:

[0203] Step S1601, performing calibration measurement on first calibration sequences sent by multiple antennas in the same RRU to each other through setting a sending mode to obtain a first phase offset calibration factor of each antenna in the same RRU.

[0204] Step S1602, performing phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU.

[0205] The explanation of steps S1601 to S1602 can be referred to the related description in any of the embodiments of the present application, which will not be repeated here.

[0206] Step S1603, selecting an initial sending RRU from the indoor distributed system.

[0207] In the embodiments of the present application, one RRU can be randomly selected from the indoor distributed system as the initial sending RRU, or one RRU can be manually specified as the initial sending RRU according to network deployment, or other ways can be used to select the initial sending RRU from the indoor distributed system, and the embodiments of the present application do not make any limitation in this regard.

[0208] In step S1604, at least one round of cyclic calibration process is performed according to the initial sending RRU to determine the to-be-calibrated RRU in each round of cyclic calibration process from the indoor distributed system, and to determine the second phase offset calibration factor of the to-be-calibrated RRU, and to perform phase offset calibration on the to-be-calibrated RRU according to the second phase offset calibration factor of the to-be-calibrated RRU.

[0209] The first calibration sequence or the second calibration sequence is sent by the BBU to the RRU through the hub.

[0210] In the embodiments of the present application, at least one round of cyclic calibration process can be performed according to the initial sending RRU to determine the to-be-calibrated RRU in each round of cyclic calibration process from the indoor distributed system, and to determine the second phase offset calibration factor of the to-be-calibrated RRU, so that the phase offset calibration can be performed on the to-be-calibrated RRU according to the second phase offset calibration factor of the to-be-calibrated RRU.

[0211] In any one of the embodiments of the present application, the first round of cyclic calibration process in the at least one round of cyclic calibration process can include the following steps 1 to 5:

[0212] 1. The initial sending RRU is added to the calibrated list, and the second calibration sequence is sent to the first other RRU through the initial sending RRU. The first other RRU refers to the RRU in the indoor distributed system except the initial sending RRU.

[0213] 2. The RRU closest to the initial sending RRU in the first other RRU is taken as the to-be-calibrated RRU in the first round of cyclic calibration process.

[0214] In the embodiments of the present application, the second calibration sequence sent by the initial sending RRU can be measured by the other RRU to obtain a measurement value of the second calibration sequence, and the RRU closest to the initial sending RRU can be determined from the other RRU according to the measurement value of the second calibration sequence received by the other RRU, and the RRU closest to the initial sending RRU is taken as the to-be-calibrated RRU in the first round of cyclic calibration process.

[0215] The measurement value includes but is not limited to RSRP (Reference Signal Receiving Power, reference signal receiving power), RSSI (Received Signal Strength Indicator, received signal strength indicator), RSRQ (Reference Signal Receiving Quality, reference signal receiving quality), etc.

[0216] Taking the measured value as RSRP as an example, the RRU with the maximum RSRP can be taken as the RRU closest to the initial sending RRU.

[0217] 3. The to-be-calibrated RRU in the first round of the cyclic calibration process sends a second calibration sequence to a second other RRU.

[0218] The second other RRU is an RRU in the indoor distributed system other than the to-be-calibrated RRU in the first round of the cyclic calibration process, and the initial sending RRU is included in the second other RRU.

[0219] 4. A second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process is determined according to the second calibration sequence received by the to-be-calibrated RRU in the first round of the cyclic calibration process and the second calibration sequence received by the initial sending RRU.

[0220] In the embodiments of the present application, the channel estimation of the initial sending RRU->the to-be-calibrated RRU in the first round of the cyclic calibration process can be calculated according to the second calibration sequence received by the to-be-calibrated RRU in the first round of the cyclic calibration process, and the channel estimation of the to-be-calibrated RRU in the first round of the cyclic calibration process->the initial sending RRU can be calculated according to the second calibration sequence received by the initial sending RRU, and the second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process can be calculated according to the bidirectional channel estimations.

[0221] For example, the existing scheme (such as formula (1)) can be followed, and the bidirectional channel estimations can be divided by point to divide off the channel gain of the air interface channel, to obtain the second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process.

[0222] 5. The to-be-calibrated RRU in the first round of the cyclic calibration process is phase offset calibrated according to the second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process, and the to-be-calibrated RRU in the first round of the cyclic calibration process is added to the calibrated list.

[0223] In the embodiments of the present application, the to-be-calibrated RRU in the first round of the cyclic calibration process can be phase offset calibrated according to the second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process, and the to-be-calibrated RRU in the first round of the cyclic calibration process can be added to the calibrated list.

[0224] For example, for any one antenna in the to-be-calibrated RRU in the first round of the cyclic calibration process, the target phase offset calibration factor of the antenna can be determined according to the product of the second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process and the first phase offset calibration factor of the antenna, so that the antenna can be phase offset calibrated based on the target phase offset calibration factor of the antenna.

[0225] In any one of the embodiments of the present application, the non-first round (such as the qth round, where q is a positive integer greater than 1) of the cyclic calibration process in at least one round of the cyclic calibration process can comprise the following steps S1-S7:

[0226] S1, judging whether all RRUs in the indoor distributed system are contained in the calibrated list, if yes, performing the following S2, if not, performing S3 and the following steps.

[0227] S2, ending the cyclic calibration process.

[0228] S3, selecting the to-be-calibrated RRU of the qth round of the cyclic calibration process from the RRU not in the calibrated list, and adding the to-be-calibrated RRU of the qth round of the cyclic calibration process to the calibrated list. Wherein, q is a positive integer greater than 1.

[0229] As an example, each RRU can have a corresponding calibration timer, which can be started when the RRU sends the second calibration sequence.

[0230] In the present application, the RRU whose calibration timer has not timed out can be selected from the RRUs in the calibrated list as a reference RRU, and then it can be judged whether there is a first target RRU among the RRUs not in the calibrated list; wherein the first target RRU is the RRU that receives the second calibration sequence sent by the reference RRU, and the SNR of the second calibration sequence sent by the reference RRU received by the first target RRU is greater than a first set threshold. If there is a first target RRU among the RRUs not in the calibrated list, the first target RRU closest to the reference RRU can be selected as the to-be-calibrated RRU of the qth round of the cyclic calibration process. For example, the RSRP of the second calibration sequence sent by the reference RRU received by the first target RRU closest to the reference RRU is the largest.

[0231] And if there is no first target RRU among the RRUs not in the calibrated list, the following steps A-H can be performed:

[0232] A, based on the RSRP of all second calibration sequences received by each RRU not in the calibrated list, selecting the to-be-calibrated RRU of the qth round of the cyclic calibration process from the RRUs not in the calibrated list, and adding the to-be-calibrated RRU of the qth round of the cyclic calibration process to the calibrated list. For example, the RRU not in the calibrated list that receives the second calibration sequence with the largest RSRP can be selected as the to-be-calibrated RRU of the qth round of the cyclic calibration process.

[0233] B, sending the second calibration sequence by the to-be-calibrated RRU of the qth round of the cyclic calibration process to the RRUs in the calibrated list.

[0234] Further, the to-be-calibrated RRU of the qth round of the cyclic calibration process can also send the second calibration sequence to the RRU not located in the calibrated list.

[0235] C, judging whether there is a second target RRU in the calibrated list, if yes, performing subsequent steps D to F, if not, performing subsequent steps G to H. Wherein, the SNR of the second calibration sequence received by the second target RRU from the to-be-calibrated RRU of the qth round of the cyclic calibration process is greater than the first set threshold.

[0236] D, determining a third target RRU closest to the to-be-calibrated RRU of the qth round of the cyclic calibration process from the second target RRU.

[0237] In the embodiments of the present application, in the case that there is a second target RRU in the calibrated list, a third target RRU closest to the to-be-calibrated RRU of the qth round of the cyclic calibration process can be determined from the second target RRU. For example, the RSRP of the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process received by the third target RRU is the largest.

[0238] E, determining the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process received by the third target RRU, and according to the second calibration sequence sent by the third target RRU received by the to-be-calibrated RRU of the qth round of the cyclic calibration process.

[0239] In the embodiments of the present application, the channel estimation of the to-be-calibrated RRU of the qth round of the cyclic calibration process -> the third target RRU can be calculated according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process received by the third target RRU, and the channel estimation of the third target RRU -> the to-be-calibrated RRU of the qth round of the cyclic calibration process can be calculated according to the second calibration sequence sent by the third target RRU received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, so that the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process can be calculated according to the above-mentioned two-way channel estimation.

[0240] F, performing phase offset calibration on the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process. Wherein, the phase offset calibration manner of the to-be-calibrated RRU of the qth round of the cyclic calibration process is similar to the phase offset calibration manner of the to-be-calibrated RRU of the first round of the cyclic calibration process, and the implementation principle is similar, which will not be described here.

[0241] G, reselecting the initial sending RRU from the RRU not in the calibrated list.

[0242] In the embodiments of the present application, in the case that the second target RRU does not exist in the calibrated list, the initial sending RRU can be reselected from the RRU not in the calibrated list, for example, any or a random one of the RRU not in the calibrated list can be selected as the reselected initial sending RRU. That is, the RRU in the calibrated list does not need to be re-calibrated, and only the RRU not in the calibrated list needs to be calibrated.

[0243] For example, it is assumed that the RRU in the indoor distributed system is distributed in two independent areas (denoted as area 1 and area 2), wherein all the RRU in the area 1 have been traversed (that is, all the RRU in the area 1 are in the calibrated list), and all the RRU in the area 2 do not satisfy the mutual calibration condition with the area 1 (for example, there is no first target RRU in the RRU not in the calibrated list, and there is no second target RRU in the calibrated list), then one RRU in the area 2 can be reselected as the initial sending RRU.

[0244] H. performing at least one round of the cyclic calibration process according to the reselected initial sending RRU.

[0245] In the embodiments of the present application, at least one round of the cyclic calibration process can be re-executed according to the reselected initial sending RRU, that is, returning to step S1604.

[0246] S4, sending, by the to-be-calibrated RRU in the qth round of the cyclic calibration process, a second calibration sequence to a third other RRU. The third other RRU is an RRU in the indoor distributed system except the to-be-calibrated RRU in the qth round of the cyclic process.

[0247] S5, determining, from the RRU in the calibrated list, a calibrated RRU closest to the to-be-calibrated RRU in the qth round of the cyclic calibration process. For example, the RSRP of the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process received by the calibrated RRU is the largest.

[0248] S6, determining, according to the second calibration sequence sent by the calibrated RRU received by the to-be-calibrated RRU in the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process received by the calibrated RRU, a second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process.

[0249] In the embodiments of the present application, the channel estimation of the calibrated RRU-> the to-be-calibrated RRU in the qth round of the cyclic calibration process can be calculated according to the second calibration sequence transmitted by the calibrated RRU and received by the to-be-calibrated RRU in the qth round of the cyclic calibration process, and the channel estimation of the to-be-calibrated RRU-> the calibrated RRU in the qth round of the cyclic calibration process can be calculated according to the second calibration sequence transmitted by the to-be-calibrated RRU and received by the calibrated RRU in the qth round of the cyclic calibration process, so that the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process can be calculated according to the above-mentioned bidirectional channel estimations.

[0250] S7, phase offset calibration is performed on the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process. The phase offset calibration manner of the to-be-calibrated RRU in the qth round of the cyclic calibration process is similar to the phase offset calibration manner of the to-be-calibrated RRU in the first round of the cyclic calibration process, and the implementation principle is similar, which will not be described here.

[0251] In any one of the embodiments of the present application, the non-first round (for example, the qth round, where q is a positive integer greater than 1) of the at least one round of the cyclic calibration process can include the following steps S1' to S6':

[0252] S1', it is judged whether the calibrated list contains all the RRUs in the indoor distributed system, if yes, the subsequent S2' is executed, and if not, S3' and the subsequent steps are executed.

[0253] S2', the cyclic calibration process is ended.

[0254] S3', a plurality of sending RRUs corresponding to the qth round of the cyclic calibration process are selected from the calibrated list.

[0255] As an example, all the RRUs in the calibrated list can be used as the plurality of sending RRUs corresponding to the qth round of the cyclic calibration process.

[0256] As another example, a set number (for example, N, N is a positive integer greater than 1) of RRUs can be randomly selected from the calibrated list as the plurality of sending RRUs corresponding to the qth round of the cyclic calibration process.

[0257] As yet another example, a set number of RRUs can be selected in sequence from the calibrated list as the plurality of sending RRUs corresponding to the qth round of the cyclic calibration process. For example, the first RRU added to the calibrated list, the second RRU added to the calibrated list, …, the Nth RRU added to the calibrated list can be used as the plurality of sending RRUs corresponding to the qth round of the cyclic calibration process.

[0258] S4', taking the rest of the RRUs as the to-be-calibrated RRUs of the qth round of the cyclic calibration process, and sending the second calibration sequence to the multiple sending RRUs by the to-be-calibrated RRUs of the qth round of the cyclic calibration process. Wherein, the rest of the RRUs refers to the RRUs in the indoor distributed system except the RRUs in the calibrated list.

[0259] S5', determining the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second calibration sequence sent by the multiple sending RRUs and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the multiple sending RRUs.

[0260] As an example, for S4', for any one of the to-be-calibrated RRUs of the qth round of the cyclic calibration process, the fourth target RRU closest to the to-be-calibrated RRU can be determined from the multiple sending RRUs according to the measurement value (such as RSRP) of the second calibration sequence sent by the multiple sending RRUs and received by the to-be-calibrated RRU. For example, the RSRP of the second calibration sequence sent by the fourth target RRU and received by the to-be-calibrated RRU is the largest. Then, the second calibration sequence can be sent to the fourth target RRU by the to-be-calibrated RRU based on the code division multiplexing transmission mode.

[0261] Therefore, in this application, for S5', the second phase offset calibration factor of the to-be-calibrated RRU can be determined according to the second calibration sequence sent by the to-be-calibrated RRU and received by the fourth target RRU, and the second calibration sequence sent by the fourth target RRU and received by the to-be-calibrated RRU.

[0262] For example, the channel estimation of the to-be-calibrated RRU-> fourth target RRU can be calculated according to the second calibration sequence sent by the to-be-calibrated RRU and received by the fourth target RRU, and the channel estimation of the fourth target RRU-> to-be-calibrated RRU can be calculated according to the second calibration sequence sent by the fourth target RRU and received by the to-be-calibrated RRU, so that the second phase offset calibration factor of the to-be-calibrated RRU can be calculated according to the above-mentioned two-way channel estimation.

[0263] As another example, for S4', for any one of the to-be-calibrated RRUs of the qth round of the cyclic calibration process, the second calibration sequence can be sent to the multiple sending RRUs by the to-be-calibrated RRU based on the code division multiplexing transmission mode.

[0264] Thus, in the present application, for S5', the plurality of phase offset calibration factors corresponding to the to-be-calibrated RRU can be determined according to the second calibration sequence transmitted by the to-be-calibrated RRU and received by the plurality of transmitting RRUs, and according to the second calibration sequence transmitted by the plurality of transmitting RRUs and received by the to-be-calibrated RRU, and then the second phase offset calibration factor of the to-be-calibrated RRU can be determined according to the mean value of the plurality of phase offset calibration factors.

[0265] For example, assuming that the to-be-calibrated RRU is RRU5, and the plurality of transmitting RRUs are RRU3, RRU4 and RRU6 respectively, the channel estimation of RRU5->RRU3 can be calculated according to the second calibration sequence transmitted by RRU5 and received by RRU3, the channel estimation of RRU3->RRU5 can be calculated according to the second calibration sequence transmitted by RRU3 and received by RRU5, and thus the phase offset calibration factor of RRU5 can be calculated according to the channel estimation of RRU5->RRU3 and the channel estimation of RRU3->RRU5 by using formula (1).

[0266] Similarly, the channel estimation of RRU5->RRU4 can be calculated according to the second calibration sequence transmitted by RRU5 and received by RRU4, the channel estimation of RRU4->RRU5 can be calculated according to the second calibration sequence transmitted by RRU4 and received by RRU5, and thus the phase offset calibration factor of RRU5 can be calculated according to the channel estimation of RRU5->RRU4 and the channel estimation of RRU4->RRU5 by using formula (1).

[0267] Further, the channel estimation of RRU5->RRU6 can be calculated according to the second calibration sequence transmitted by RRU5 and received by RRU6, the channel estimation of RRU6->RRU5 can be calculated according to the second calibration sequence transmitted by RRU6 and received by RRU5, and thus the phase offset calibration factor of RRU5 can be calculated according to the channel estimation of RRU5->RRU6 and the channel estimation of RRU6->RRU5 by using formula (1).

[0268] Thus, in the present application, the mean value of the above-mentioned three phase offset calibration factors can be taken as the second phase offset calibration factor of RRU5.

[0269] S6', according to the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process, performing phase offset calibration on the to-be-calibrated RRU in the qth round of the cyclic calibration process.

[0270] The phase offset calibration manner of the to-be-calibrated RRU in the qth round of the cyclic calibration process is similar to the phase offset calibration manner of the to-be-calibrated RRU in the first round of the cyclic calibration process, and the implementation principle is similar, which will not be described here.

[0271] The air interface calibration method of the indoor distributed system can adopt a cyclic calibration manner to calibrate the phase offset of each RRU in the indoor distributed system, thereby improving the effectiveness of the phase offset calibration.

[0272] The embodiment of the present application provides another air interface calibration method, Figure 17 FIG. 7 is a flowchart of a seventh air interface calibration method of an indoor distributed system according to an embodiment of the present application. It should be noted that the air interface calibration method can be independently executed, or can be executed in combination with any embodiment or possible implementation manner of the embodiments of the present application, or can be executed in combination with any technical solution in the related art, and the embodiments of the present application do not make any limitation in this regard.

[0273] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and a plurality of RRUs connected to each Hub.

[0274] As Figure 17 The air interface calibration method of the indoor distributed system can include the following steps:

[0275] In step S1701, a first calibration sequence transmitted between a plurality of antennas in the same RRU through a set transmission manner is measured and calibrated to obtain a first phase offset calibration factor of each antenna in the same RRU.

[0276] In step S1702, each antenna in the same RRU is calibrated based on the first phase offset calibration factor of each antenna in the same RRU.

[0277] The explanation and description of steps S1701 to S1702 can be referred to the related description in any embodiment of the present application, and will not be repeated here.

[0278] In step S1703, a second calibration sequence transmitted between RRUs with a distance less than a second set threshold in the indoor distributed system is measured and calibrated to obtain an initial phase offset calibration factor of the RRU with the distance less than the second set threshold.

[0279] The first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

[0280] In the embodiment of the present application, the RRU (i.e., the adjacent RRU) with a distance less than the second set threshold can be determined from the indoor distributed system, and the second calibration sequence is transmitted between the RRUs (i.e., the adjacent RRUs) with the distance less than the second set threshold, so that the second calibration sequence transmitted between the RRUs (i.e., the adjacent RRUs) with the distance less than the second set threshold can be measured and calibrated to obtain the initial phase offset calibration factor of the RRU (i.e., the adjacent RRU) with the distance less than the second set threshold.

[0281] Step S1704, based on the least square method, the initial phase offset calibration factor of each RRU is adjusted to obtain the second phase offset calibration factor of each RRU.

[0282] In the embodiments of the present application, the initial phase offset calibration factor of all RRUs in the indoor distributed system can be adjusted based on the least square method to obtain the second phase offset calibration factor of each RRU.

[0283] Step S1705, based on the second phase offset calibration factor of each RRU, the phase offset calibration is performed on each antenna in each RRU.

[0284] The explanation of step S1705 can be referred to the related description in any embodiment of the present application, which will not be repeated here.

[0285] The air interface calibration method of the indoor distributed system in the embodiments of the present application can not only realize the phase offset calibration of the RRUs in the indoor distributed system through the maintenance of the calibrated list, but also can realize that the global optimal second phase offset calibration factor is obtained by measuring the receiving and transmitting phase difference information between the adjacent RRUs and introducing the least square method for adjustment, which can improve the accuracy of the phase offset calibration of each RRU.

[0286] In any embodiment of the present application, the present application proposes an implementation method of air interface calibration of RRU in and between Hubs in the Hub merging scenario. The logical channel after Hub merging is effectively utilized through time division, frequency division and code division, so that the BBU can obtain the channel phase offset information of each RRU to complete the air interface calibration.

[0287] That is, the present application gives the air interface calibration scheme of RRU inside, RRU between Hubs inside and RRU between Hubs. The basic strategy is that the calibration is performed for each RRU, and the existing scheme cannot be directly used for the channel after the merging of multiple RRUs. Different RRUs can be ensured to obtain the received signal of the uplink calibration sequence from a certain antenna (or channel) in a certain RRU through frequency division, time division and code division.

[0288] Specifically, taking the BBU as the execution subject of each embodiment of the present application as an example, the sending of the calibration sequence and the data transmission process in the air interface calibration process can be as shown in Figure 18 The implementation principle of the air interface calibration process can be as shown in Figure 19 The main steps include the following steps:

[0289] It should be noted that Figure 18 The air interface calibration process shown in is applicable to RRU calibration and RRU calibration. The difference is only thatFigure 18 Is the air interface channel between channels within the RRU or between RRUs?

[0290] Step 1, in the case that the indoor distributed system meets the triggering condition of air interface calibration, start calibration.

[0291] The triggering condition of air interface calibration includes at least one of the following: periodic triggering: set according to the statistical period of inter-channel phase drift measurement, such as one day or several hours; network deployment change related event triggering: such as adding new deployment RRU or closing certain RRU, or the deployment position of RRU changes; RRU re-powering: some RRUs are powered off and then powered on due to energy saving needs; downlink non-codebook transmission performance monitoring: such as monitoring that the non-codebook performance has a significant performance decline compared to the codebook.

[0292] Step 2, inter-channel calibration measurement and compensation within the RRU.

[0293] Step 2.1: inter-channel calibration measurement within the RRU: by mutually sending calibration sequences between multiple antennas in the same RRU (i.e. between channels), and performing calibration measurement on the calibration sequences sent by multiple antennas to each other, the phase offset calibration factor of each antenna within the same RRU is obtained.

[0294] Since the uplink signals of multiple RRUs are combined at the Hub, simultaneous calibration of multiple RRUs on the same time-frequency resource is not possible, and time division (embodiment B), frequency division (embodiment A), and code division (embodiment C) resources can be used to stagger the calibration of each RRU to achieve independent calibration of each channel.

[0295] Step 2.2: RRU internal compensation or phase offset calibration factor compensation process: after the BBU determines the phase offset calibration factor of each antenna, the phase offset calibration factor can be transmitted to the RRU for self-compensation by the RRU; or transmitted to the Hub, and after the downlink channel is separated, each antenna is compensated separately according to the phase offset calibration factor of each antenna in each RRU to align the phase difference of all channels within the RRU.

[0296] Taking the compensation of the sending end as an example: if the downlink data transmitted by the BBU to the RRU is frequency domain data (the RRU completes the conversion from frequency domain to time domain), the RRU is compensated according to the phase offset calibration factor;

[0297] If the downlink data transmitted by the BBU to the RRU is time domain data (the conversion from frequency domain to time domain is completed at the BBU side), the time offset information and phase offset information between channels need to be extracted from the phase offset calibration factor, and the compensation is completed in the time domain.

[0298] Step 3, Hub intra / inter-RRU calibration.

[0299] In the existing scheme, on the basis of intra-RRU calibration, a physical channel is selected from each RRU and mutual calibration is performed between the selected channel and other RRU, to obtain the difference between the transceiving phase differences of different RRUs. The mutual transceiving between different RRUs can be time-division staggered (which can be different Gp symbols in a radio frame, or different Gp in different radio frames). In the Hub merging scenario, this idea can be followed. Considering that the air interface channel attenuation of inter-RRU calibration is relatively large, a frequency division multiplexing mode is not introduced, and each RB only occupies a certain RE to improve the transmission power of a single RE.

[0300] In the Hub merging scenario, there are cases where each Hub covers separately, as shown in Figure 3 , and cases where two Hubs cross cover, as shown in Figure 4 , and no distinction is needed in the calibration process.

[0301] For inter-RRU calibration, each RRU (i.e., pico) only selects one channel to participate in the mutual calibration with other RRUs. At each moment, a certain pico acts as the transmitter to send the calibration sequence, and the other RRUs act as the receiver.

[0302] Taking the Hub cross coverage as shown in Figure 4 : At time 1, pico1 is the transmitter, and pico5, 2, 6, 3, 7, 4, and 8 are the receivers; at time 2, pico5 is the transmitter, and pico1, 2, 6, 3, 7, 4, and 8 are the receivers; and so on.

[0303] Since the bidirectional channel gain is point-divided in the inter-RRU calibration, the premise for eliminating the channel gain of the air interface channel is that the bidirectional air interface channel gains are equal. However, in the actual environment, the air interface channel will change over time, so the shorter the time of the inter-RRU mutual calibration sequence process, the closer the distance between two transmissions, and the better the calibration effect. In the case where the relative position relationship between the BBU and the RRUs is unknown, it is necessary to consider how to arrange the transmission order of the calibration sequence between the RRUs.

[0304] Taking the cross coverage scenario as shown in Figure 4 : When pico1 sends the calibration sequence, although other picos can receive the calibration sequence, only pico5, which is most closely related to pico1 and most likely to form a joint transmission condition, can meet the calibration SNR requirement (i.e., the SNR of the calibration sequence received by the pico is greater than a first set threshold). At this time, pico5 should be allowed to send the calibration sequence as soon as possible to complete the mutual calibration of pico1->pico5 and pico5->pico1.

[0305] In the present application, a list of RRUs that have completed calibration under the current BBU (denoted as calibrated list in the present application) can be maintained, and the calibrated list is emptied before each round of calibration. When a certain RRU and the nearest RRU complete calibration, both of the two RRUs can be put into the calibrated list, and when all RRUs enter the calibrated list, the current round of calibration ends.

[0306] The distance between RRUs can be determined by the uplink received power when the calibration sequence is transmitted. For example, when RRU1 transmits the calibration sequence, the uplink received power RSRP of the calibration sequence received by RRUs 5, 2, 6, 3, 7, 4, and 8 is the strongest, and RRU5 is the nearest RRU to RRU1.

[0307] After each RRU transmits the calibration sequence, a timer Timer valid can be started to count the validity of the calibration sequence transmitted by the RRU and measured by each RRU. When the timer expires, the calibration sequence transmitted by the RRU is no longer valid on other RRUs, and if the RRU needs to be calibrated with other RRUs, the RRU needs to retransmit the calibration sequence.

[0308] The specific scheme flow is as follows:

[0309] Step 3.1: Start inter-RRU calibration. First, select a starting RRU (denoted as initial transmitting RRU in the present application), for example, randomly select an RRU or manually specify an RRU according to network deployment as the starting RRU, and put the starting RRU into the calibrated list, for example, RRU1 in Figure 4 . Transmit the calibration sequence through the starting RRU, and determine the nearest RRU to the starting RRU as the candidate transmitting RRU (denoted as to-be-calibrated RRU in the present application) according to the received power of each antenna of the receiving end, for example, RRU5 in Figure 4 .

[0310] Step 3.2: Transmit the calibration sequence by the selected to-be-calibrated RRU. Other RRUs receive the calibration sequence and record the received power RSRP m→n and the received signal-to-noise ratio SNR m→n . Wherein m is the number of the RRU transmitting the calibration sequence, and n is the number of the RRU receiving the calibration sequence.

[0311] Due to the introduction of Hub merging, special processing is required at the Hub side when transmitting the calibration sequence, and transmission is performed only at specified or calibrated RRUs at a specific time, rather than being simultaneously distributed to different RRUs for downlink transmission.

[0312] Step 3.3: The surrounding RRUs receive the calibration sequence and calibration measurement.

[0313] For example, the calculation of the phase offset calibration factor between two RRUs can be completed, the phase offset calibration factor of the newly added RRU to be calibrated is calculated based on the RRUs in the calibrated list, and the RRU newly sending the calibration sequence is put into the calibrated list. That is, in the first round, RRU1->RRU5 and RRU5->RRU1 mutual calibration, the phase offset calibration factor of RRU5 is calculated based on RRU1, C5 is obtained, and RRU5 is calibrated by using C5. After that, RRU5 can be put into the calibrated list.

[0314] Among them, due to the introduction of Hub merging, the Hub receiving end needs special processing, and the uplink signals of multiple RRUs cannot be directly accumulated, but the received signals of the calibration sequences of all RRUs need to be respectively transmitted back to the BBU. When the uplink transmission channel between Hub and BBU is not limited, the received signals of the uplink calibration sequences of all RRUs can be directly transmitted back to the BBU through the Hub, and the BBU performs RRU screening, selects the RRU that meets the air interface calibration signal-to-noise ratio condition from the received signals of different channels according to the strength, and performs calibration. When the uplink transmission channel between Hub and BBU is limited, the Hub can complete the preliminary screening of RRUs, select the calibration sequence of the RRU with strong uplink received power RSRP to transmit back to the BBU, and then perform other processing.

[0315] Whether the Hub side needs to complete the screening of RRUs, the calibration sequence of the RRU needs to be transmitted separately, unlike the signal merging of multiple RRUs for normal uplink service data, the backhaul link interface of the GP symbol needs to be specially designed and modified.

[0316] Step 3.4: RRU inter-calibration compensation. The newly sent RRU (i.e. RRU5 in the first round) is compensated. Among them, the calibration compensation method is the same as the RRU internal calibration, which needs to be completed independently by the RRU or Hub for each RRU. For example, the phase offset calibration factor between RRUs can be multiplied by the phase offset calibration factor of each antenna in the RRU to obtain the final phase offset calibration factor corresponding to each antenna in the RRU, so that each antenna can be calibrated and compensated by using the final phase offset calibration factor of each antenna.

[0317] Step 3.5: Determine whether all RRUs are in the calibrated list (i.e., determine whether all RRUs have been calibrated), if yes, end the current round of calibration, if not, continue to execute the subsequent step 3.6.

[0318] Step 3.6: Select the next sending RRU: find the RRUm from the calibrated list whose timer Timer valid has not expired (Timer valid < MaxValidTime) and whose SNR m→n satisfies the calibration minimum SNR condition (i.e., SNR m→n is greater than the first set threshold) from all RRun that received the calibration sequence sent by RRUm, and select the RRU whose RSRP m→n is the highest. If the RRUm is the closest to the selected RRU, then the selected RRU is the next sending RRU. If the selected RRU is not in the calibrated list, then continue to select the RRU that is the second closest to the selected RRU as the next sending RRU. If the next sending RRU is found, then go back to step 3.2; otherwise, go to step 3.7, which is similar to step 3.1, and a sending RRU needs to be selected.

[0319] Step 3.7: If no other RRU that is not in the calibrated list can be associated according to step 3.6, but there are still RRU that are not in the calibrated list, then find the RRU whose historical received power RSRP is the highest in the current round of calibration from the remaining uncalibrated RRU as a new initial RRU, and send a calibration sequence. After the new initial RRU sends the calibration sequence, if there is a calibrated RRU in the calibrated list that satisfies the calibration minimum SNR condition, then select the RRU whose received power RSRP is the highest from the RRU in the calibrated list, and exchange calibration sequences with it (i.e., go back to step 3.2), and take the calibrated RRU as the reference to calculate the phase offset calibration factor for the new initial RRU (i.e., go back to step 3.3), so as to perform step 3.4 to compensate for the inter-RRU for the new initial RRU; if there is no calibrated RRU that satisfies the calibration minimum SNR condition, then treat it as a completely new initial RRU and go back to step 3.1.

[0320] On the basis of the above exchange of calibration sequences, different calibration sequences, i.e., code division multiplexing, can also be introduced. In step 3.6, multiple RRU can be selected to send different calibration sequences at the same time, and other RRU as the receiving end can obtain multiple sets of inter-RRU channel gains at the same time. In the calculation process of the phase offset calibration factor, the multiple sending RRU in code division multiplexing are all calibrated RRU in the calibrated list, and the following processing can be done:

[0321] Each RRU can only calculate the phase offset calibration factor for the nearest RRU; or each RRU exchanges calibration sequences with multiple surrounding RRUs to obtain multiple phase offset calibration factors, and average the multiple phase offset calibration factors; or a more optimal solution is that the calibrated list is no longer maintained, and the information of the transmission-reception phase difference between all adjacent RRUs is obtained by measurement, and a more complex total least squares model is introduced for global solution.

[0322] In summary, the scheme provided in the present application is suitable for RRU air interface calibration in the Hub merging scenario. By staggering the frequency domain, time domain resources or different sequences (code division) of the calibration sequence, the BBU side can obtain independent transmission-reception information of each physical channel to complete the calibration of the transmission-reception phase offset or phase difference. That is, the present application gives a generalization scheme for air interface calibration in the Hub merging scenario, which solves the problem that the air interface calibration mode of RRU-BBU direct connection cannot be directly applied in the Hub merging scenario, widens the application scenario of air interface calibration, and improves the feasibility of the application of the technology in actual commercial networks.

[0323] The technical solutions provided by the embodiments of the present application can be applied to various systems, especially 5G systems. For example, the applicable systems can be a Global System of Mobile communication (GSM) system, a Code Division Multiple Access (CDMA) system, a Wideband Code Division Multiple Access (WCDMA) General Packet Radio Service (GPRS) system, a long term evolution (LTE) system, an LTE Frequency Division Duplex (FDD) system, an LTE time division duplex (TDD) system, a Long Term Evolution Advanced (LTE-A) system, a Universal Mobile Telecommunication System (UMTS), a Worldwide interoperability for Microwave Access (WiMAX) system, a 5G New Radio (NR) system, and the like. The various systems all include terminal devices and network devices. The system can also include a core network part, such as an Evloved Packet System (EPS), a 5G system (5GS), and the like.

[0324] To implement the above embodiments, the present application further provides a network device. Figure 20 is a structural schematic diagram of a network device according to an embodiment of the present application. As shown in the figure, the network device can include a transceiver 2000, a processor 2010, and a memory 2020. Figure 20

[0325] ​The memory 2020 is configured to store a computer program; the transceiver 2000 is configured to receive and send data under the control of the processor 2010; the processor 2010 is configured to read the computer program in the memory 2020 and perform the following operations: performing calibration measurement on a first calibration sequence transmitted between multiple antennas in the same RRU by setting a transmission mode, to obtain a first phase offset calibration factor of each antenna in the same RRU; wherein the RRU is deployed in an indoor distributed system, the indoor distributed system includes a BBU, at least one Hub connected to the BBU, and multiple RRUs connected to the Hub; performing phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU; performing calibration measurement on a second calibration sequence transmitted between different RRUs, to obtain a second phase offset calibration factor of each RRU, and performing phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU; wherein the first calibration sequence or the second calibration sequence is transmitted from the BBU to the RRU through the Hub.

[0326] The transceiver 2000 is configured to receive and send data under the control of the processor 2010. In the above embodiment, the transceiver 2000 is configured to receive the first calibration sequence and the second calibration sequence, and send the first calibration sequence and the second calibration sequence. Figure 20 The bus architecture can include any number of interconnecting buses and bridges, and the various circuitry represented by the processor 2010 and the memory 2020 is linked together by the bus architecture, which can also link various other circuitry that is well known, such as, for example, peripheral devices, voltage stabilizers, and power management circuitry, but are not further described herein. The bus interface provides an interface to the bus architecture. The transceiver 2000 can be multiple elements, i.e., including a transmitter and a receiver, which provide a means for communicating with various other apparatuses over a transmission medium, including wireless channels, wired channels, optical cables, and the like. The processor 2010 is responsible for managing the bus architecture and general processing, and the memory 2020 can store data used by the processor 2010 in performing operations.

[0327] Optionally, the processor 2010 can be a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a CPLD (Complex Programmable Logic Device), and the processor can also adopt a multi-core architecture.

[0328] The processor 2010 calls a program stored in the memory 2020 to execute the calibration sequence according to the executable instructions obtained, and the calibration sequence is used to calibrate the first phase offset calibration factor of each antenna in the same RRU. Figures 5 to 17 The processor 2010 and the memory 2020 can also be physically arranged separately.

[0329] As a possible implementation, the REs occupied by the multiple RRUs connected to the same Hub are different, and the first calibration sequence is a calibration sequence generated by the BBU according to the first RE occupied by the same RRU; wherein, the sending mode includes frequency division multiplexing sending mode, and the frequency division multiplexing sending mode includes: in the case of reaching the i th moment, through the i th antenna in the same RRU, the first calibration sequence is sent to the remaining antennas; wherein, i is a positive integer, the first calibration sequence is sent by the i th antenna using the first RE, and the remaining antennas are the antennas in the same RRU except the i th antenna; the processor 2010 performs calibration measurement on the first calibration sequence sent by the multiple antennas in the same RRU through the set sending mode, to obtain the first phase offset calibration factor of each antenna in the same RRU, specifically: the first calibration sequence received by the i th antenna and the first calibration sequence received by the remaining antennas at different moments are calibrated and measured to obtain the first phase offset calibration factor of each antenna in the same RRU.

[0330] As a possible implementation, the REs occupied by the different antennas in the same RRU are different, and the REs occupied by the antennas of the same port in the multiple RRUs connected to the same Hub are the same; the first calibration sequence sent by any antenna is a calibration sequence generated by the BBU according to the second RE occupied by any antenna; wherein, the sending mode includes time division multiplexing sending mode, and the time division multiplexing sending mode includes: taking the j th antenna in the same RRU as a reference, through the other antennas using the second REs occupied by the other antennas, the first calibration sequence is sent to the j th antenna; wherein, j is a positive integer, and the other antennas are the antennas in the same RRU except the j th antenna; through the j th antenna using the second REs occupied by the other antennas, the first calibration sequence is sent to the other antennas; the processor 2010 performs calibration measurement on the first calibration sequence sent by the multiple antennas in the same RRU through the set sending mode, to obtain the first phase offset calibration factor of each antenna in the same RRU, specifically: the first calibration sequence received by the j th antenna and the first calibration sequence received by the other antennas are calibrated and measured to obtain the first phase offset calibration factor of the other antennas.

[0331] As a possible implementation manner, the first calibration sequence sent by any one of the antennas is a calibration sequence generated by the BBU according to the cyclic shift occupied by the RRU to which any one of the antennas belongs and the third RE occupied by any one of the antennas, different from the cyclic shift occupied by the multiple RRUs connected with the same Hub, different from the RE occupied by the multiple antennas in the same RRU; wherein, the sending mode includes a code division multiplexing sending mode, the code division multiplexing sending mode includes: taking the kth antenna in the same RRU as a reference, sending the first calibration sequence to the kth antenna through the third RE occupied by the other antennas; wherein, k is a positive integer, the other antennas are the antennas in the same RRU except the kth antenna; sending the first calibration sequence to the other antennas through the third RE occupied by the kth antenna; the processor 2010 performs calibration measurement on the first calibration sequence sent by the multiple antennas in the same RRU to each other through the set sending mode, and obtains the first phase offset calibration factor of each antenna in the same RRU, specifically: performing calibration measurement on the first calibration sequence received by the kth antenna and the first calibration sequence received by the other antennas to obtain the first phase offset calibration factor of the other antennas.

[0332] As a possible implementation manner, the processor 2010 performs phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU, specifically: for any one of the antennas in the same RRU, in a case where the downlink signal sent by the BBU to the same RRU is a frequency domain signal, performing phase offset compensation on any one of the antennas based on the first phase offset calibration factor of any one of the antennas; in a case where the downlink signal is a time domain signal, extracting time offset information and phase offset information from the first phase offset calibration factor of any one of the antennas; performing calibration compensation on any one of the antennas based on the time offset information and the phase offset information.

[0333] As a possible implementation manner, the processor 2010 performs calibration measurement on the second calibration sequence sent by the different RRUs to each other, obtains the second phase offset calibration factor of each RRU, and performs phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU, specifically: selecting an initial sending RRU from the indoor distributed system; performing at least one round of cyclic calibration process according to the initial sending RRU, to determine the RRU to be calibrated in each round of cyclic calibration process from the indoor distributed system, and determine the second phase offset calibration factor of the RRU to be calibrated, and perform phase offset calibration on the RRU to be calibrated according to the second phase offset calibration factor of the RRU to be calibrated.

[0334] As a possible implementation manner, the processor 2010 performs a first round of the at least one round of the cyclic calibration process, specifically: adding an initial sending RRU to the calibrated list, and sending a second calibration sequence to a first other RRU through the initial sending RRU; wherein the first other RRU refers to an RRU in the indoor distributed system except the initial sending RRU; taking an RRU closest to the initial sending RRU in the first other RRU as a to-be-calibrated RRU of the first round of the cyclic calibration process; sending a second calibration sequence to a second other RRU through the to-be-calibrated RRU of the first round of the cyclic calibration process; wherein the second other RRU refers to an RRU in the indoor distributed system except the to-be-calibrated RRU of the first round of the cyclic calibration process; determining a second phase offset calibration factor of the to-be-calibrated RRU of the first round of the cyclic calibration process according to the second calibration sequence received by the to-be-calibrated RRU of the first round of the cyclic calibration process and the second calibration sequence received by the initial sending RRU; and performing phase offset calibration on the to-be-calibrated RRU of the first round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the first round of the cyclic calibration process, and adding the to-be-calibrated RRU of the first round of the cyclic calibration process to the calibrated list.

[0335] As a possible implementation manner, the processor 2010 performs a qth round of the at least one round of the cyclic calibration process, specifically: judging whether all RRU in the indoor distributed system are contained in the calibrated list; if yes, ending the cyclic calibration process, and if not, selecting a to-be-calibrated RRU of the qth round of the cyclic calibration process from the RRU not in the calibrated list, and adding the to-be-calibrated RRU of the qth round of the cyclic calibration process to the calibrated list; wherein q is a positive integer greater than 1; sending a second calibration sequence to a third other RRU through the to-be-calibrated RRU of the qth round of the cyclic calibration process; wherein the third other RRU refers to an RRU in the indoor distributed system except the to-be-calibrated RRU of the qth round of the cyclic calibration process; determining an RRU closest to the to-be-calibrated RRU of the qth round of the cyclic calibration process from the RRU in the calibrated list; determining a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second calibration sequence sent by the calibrated RRU and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the calibrated RRU; and performing phase offset calibration on the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process.

[0336] As a possible implementation manner, when each RRU transmits the second calibration sequence, a calibration timer corresponding to the RRU is started; the processor 2010 executes selection of a to-be-calibrated RRU in the qth round of cyclic calibration process from the RRU not in the calibrated list, specifically: selecting a reference RRU whose calibration timer is not overdue from the calibrated list; judging whether there is a first target RRU among the RRU not in the calibrated list; the first target RRU is an RRU receiving the second calibration sequence transmitted by the reference RRU, and the SNR of the second calibration sequence received by the first target RRU is greater than a first set threshold; if the first target RRU exists, the first target RRU closest to the reference RRU is selected as the to-be-calibrated RRU in the qth round of cyclic calibration process.

[0337] As a possible implementation manner, the processor 2010 is further configured to: if the first target RRU does not exist, select the to-be-calibrated RRU in the qth round of cyclic calibration process from the RRU not in the calibrated list based on the RSRP of all the second calibration sequences received by each RRU not in the calibrated list, and add the to-be-calibrated RRU in the qth round of cyclic calibration process to the calibrated list; transmit the second calibration sequence by the to-be-calibrated RRU in the qth round of cyclic calibration process to the RRU in the calibrated list; judge whether there is a second target RRU in the calibrated list; the SNR of the second calibration sequence transmitted by the to-be-calibrated RRU in the qth round of cyclic calibration process received by the second target RRU is greater than the first set threshold; if the second target RRU exists, determine a third target RRU closest to the to-be-calibrated RRU in the qth round of cyclic calibration process from the second target RRU; determine the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of cyclic calibration process according to the second calibration sequence transmitted by the to-be-calibrated RRU in the qth round of cyclic calibration process received by the third target RRU, and according to the second calibration sequence transmitted by the third target RRU received by the to-be-calibrated RRU in the qth round of cyclic calibration process; and perform phase offset calibration on the to-be-calibrated RRU in the qth round of cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of cyclic calibration process.

[0338] As a possible implementation manner, the processor 2010 is further configured to: if the second target RRU does not exist, reselect the initial transmission RRU from the RRU not in the calibrated list; and reexecute at least one round of cyclic calibration process according to the reselected initial transmission RRU.

[0339] As a possible implementation manner, the processor 2010 executes the qth round of the loop calibration process in the at least one round of loop calibration process, specifically: judges whether all RRUs in the indoor distributed system are contained in the calibrated list; if yes, ends the loop calibration process, and if not, selects a plurality of sending RRUs corresponding to the qth round of the loop calibration process from the calibrated list; wherein q is a positive integer greater than 1; takes the remaining RRUs as the to-be-calibrated RRUs of the qth round of the loop calibration process, and sends the second calibration sequence to the plurality of sending RRUs through the to-be-calibrated RRUs of the qth round of the loop calibration process; wherein the remaining RRUs refer to the RRUs in the indoor distributed system except the RRUs in the calibrated list; determines the second phase offset calibration factor of the to-be-calibrated RRUs of the qth round of the loop calibration process according to the second calibration sequence sent by the plurality of sending RRUs and received by the to-be-calibrated RRUs of the qth round of the loop calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRUs of the qth round of the loop calibration process and received by the plurality of sending RRUs; and performs phase offset calibration on the to-be-calibrated RRUs of the qth round of the loop calibration process according to the second phase offset calibration factor of the to-be-calibrated RRUs of the qth round of the loop calibration process.

[0340] As a possible implementation manner, the processor 2010 executes the sending of the second calibration sequence to the plurality of sending RRUs through the to-be-calibrated RRUs of the qth round of the loop calibration process, specifically: for any to-be-calibrated RRU in the to-be-calibrated RRUs of the qth round of the loop calibration process, determines the fourth target RRU closest to the any to-be-calibrated RRU from the plurality of sending RRUs according to the RSRP of the second calibration sequence sent by the plurality of sending RRUs and received by the any to-be-calibrated RRU; and sends the second calibration sequence to the fourth target RRU through the any to-be-calibrated RRU based on the code division multiplexing transmission mode; and the processor 2010 executes the determination of the second phase offset calibration factor of the to-be-calibrated RRUs of the qth round of the loop calibration process according to the second calibration sequence sent by the plurality of sending RRUs and received by the to-be-calibrated RRUs of the qth round of the loop calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRUs of the qth round of the loop calibration process and received by the plurality of sending RRUs, specifically: determines the second phase offset calibration factor of the any to-be-calibrated RRU according to the second calibration sequence sent by the any to-be-calibrated RRU and received by the fourth target RRU, and according to the second calibration sequence sent by the fourth target RRU and received by the any to-be-calibrated RRU.

[0341] As a possible implementation manner, the processor 2010 performs sending, by a to-be-calibrated RRU in the qth round of cyclic calibration process, a second calibration sequence to a plurality of sending RRUs, specifically: for any to-be-calibrated RRU in the qth round of cyclic calibration process, the second calibration sequence is sent to the plurality of sending RRUs through the to-be-calibrated RRU based on a code division multiplexing sending manner; the processor 2010 performs determining, according to the second calibration sequence received by the to-be-calibrated RRU in the qth round of cyclic calibration process and sent by the plurality of sending RRUs and according to the second calibration sequence received by the plurality of sending RRUs and sent by the to-be-calibrated RRU in the qth round of cyclic calibration process, a second phase offset calibration factor of the to-be-calibrated RRU in the qth round of cyclic calibration process, specifically: determining, according to the second calibration sequence sent by any to-be-calibrated RRU and received by the plurality of sending RRUs and according to the second calibration sequence sent by the plurality of sending RRUs and received by any to-be-calibrated RRU, a plurality of phase offset calibration factors corresponding to any to-be-calibrated RRU; and determining the second phase offset calibration factor of any to-be-calibrated RRU according to a mean value of the plurality of phase offset calibration factors.

[0342] As a possible implementation manner, the processor 2010 performs calibration measurement on the second calibration sequences sent between different RRUs, to obtain a second phase offset calibration factor of each RRU, specifically: performing calibration measurement on the second calibration sequences sent between RRUs with a distance less than a second set threshold in the indoor distributed system, to obtain an initial phase offset calibration factor of the RRU with the distance less than the second set threshold; and adjusting the initial phase offset calibration factor of each RRU based on a least square method, to obtain a second phase offset calibration factor of each RRU.

[0343] As a possible implementation manner, the processor 2010 performs phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU, specifically: for any antenna, determining a target phase offset calibration factor of the any antenna according to a product of the second phase offset calibration factor of the RRU to which the any antenna belongs and the first phase offset calibration factor of the any antenna; and performing phase offset calibration on the any antenna based on the target phase offset calibration factor of the any antenna.

[0344] As a possible implementation method, the processor 2010 is also used to perform the following operations before executing calibration measurement of the first calibration sequence sent to each other by multiple antennas in the same RRU through a set transmission mode to obtain the first phase deviation calibration factor of each antenna in the same RRU: determining that the indoor distributed system meets the triggering conditions for air interface calibration; wherein the triggering conditions for air interface calibration include at least one of the following: reaching a set period; wherein the period length of the set period is determined based on the measurement period of the phase drift between different antennas in the indoor distributed system; at least one new RRU is added to the indoor distributed system; at least one RRU in the indoor distributed system is switched from a working state to a closed state; the deployment location of at least one RRU in the indoor distributed system changes; at least one RRU in the indoor distributed system is switched from a power-off state to a power-on state; the first network performance indicator obtained by the indoor distributed system using a non-codebook technology is lower than the second network performance indicator obtained by the indoor distributed system using a codebook technology, and the difference between the first network performance indicator and the second network performance indicator is greater than a third set threshold.

[0345] It should be noted that the network device provided in the embodiment of the present application can achieve the above Figures 5 to 17 All the method steps implemented in the method embodiment can achieve the same technical effects, and the parts and beneficial effects of this embodiment that are the same as those in the method embodiment will not be described in detail here.

[0346] In order to implement the above embodiment, the present application also provides an air interface calibration device for an indoor distributed system.

[0347] Figure 21 It is a structural diagram of an air interface calibration device for an indoor distributed system provided in an embodiment of the present application.

[0348] The indoor distributed system includes a BBU, at least one Hub connected to the BBU, and multiple RRUs connected to the Hub.

[0349] like Figure 21 As shown, the air interface calibration device 2100 of the indoor distributed system may include: a measuring unit 2110 , a calibration unit 2120 and a processing unit 2130 .

[0350] The measurement unit 2110 is configured to perform calibration measurement on the first calibration sequence transmitted by the multiple antennas in the same RRU through the set transmission mode, to obtain the first phase offset calibration factor of each antenna in the same RRU. The calibration unit 2120 is configured to perform phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU. The processing unit 2130 is configured to perform calibration measurement on the second calibration sequence transmitted between different RRUs, to obtain the second phase offset calibration factor of each RRU, and perform phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU; wherein the first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

[0351] As a possible implementation, the first calibration sequence is a calibration sequence generated by the BBU based on the first RE occupied by the same RRU, different from the RE occupied by the multiple RRUs connected to the same Hub, and the set transmission mode includes frequency division multiplexing transmission mode, which includes: at the ith moment, transmitting the first calibration sequence from the ith antenna in the same RRU to the remaining antennas; wherein i is a positive integer, the first calibration sequence is transmitted by the ith antenna using the first RE, and the remaining antennas are the antennas in the same RRU except the ith antenna; the measurement unit 2110 is specifically configured to: perform calibration measurement on the first calibration sequence received by the remaining antennas and the first calibration sequence received by the ith antenna at different moments, to obtain the first phase offset calibration factor of each antenna in the same RRU.

[0352] As a possible implementation, the REs occupied by different antennas in the same RRU are different, and the REs occupied by the antennas of the same port in the multiple RRUs connected to the same Hub are the same; the first calibration sequence transmitted by any antenna is a calibration sequence generated by the BBU based on the second RE occupied by the antenna; the set transmission mode includes time division multiplexing transmission mode, which includes: taking the jth antenna in the same RRU as a reference, transmitting the first calibration sequence to the jth antenna by the other antennas using the second REs occupied by the other antennas; wherein j is a positive integer, and the other antennas are the antennas in the same RRU except the jth antenna; transmitting the first calibration sequence to the other antennas by the jth antenna using the second REs occupied by the other antennas; the measurement unit 2110 is specifically configured to: perform calibration measurement on the first calibration sequence received by the jth antenna and the first calibration sequence received by the other antennas, to obtain the first phase offset calibration factor of the other antennas.

[0353] As a possible implementation manner, the first calibration sequence sent by any one of the antennas is a calibration sequence generated by the BBU according to the cyclic shift occupied by the RRU to which any one of the antennas belongs and the third RE occupied by any one of the antennas, different from the cyclic shift occupied by the multiple RRUs connected with the same Hub, and different from the RE occupied by the multiple antennas in the same RRU; the sending mode is set to include a code division multiplexing sending mode, and the code division multiplexing sending mode includes: taking the kth antenna in the same RRU as a reference, sending the first calibration sequence to the kth antenna through the third RE occupied by other antennas; wherein k is a positive integer, and the other antennas are antennas other than the kth antenna in the same RRU; sending the first calibration sequence to the other antennas through the third RE occupied by the kth antenna; the measurement unit 2110 is specifically configured to: perform calibration measurement on the first calibration sequence received by the kth antenna and the first calibration sequence received by the other antennas, to obtain the first phase offset calibration factor of the other antennas.

[0354] As a possible implementation manner, the calibration unit 2120 is specifically configured to: for any one of the antennas in the same RRU, in a case where the downlink signal sent by the BBU to the same RRU is a frequency domain signal, performing phase offset compensation on any one of the antennas based on the first phase offset calibration factor of any one of the antennas; in a case where the downlink signal is a time domain signal, extracting time offset information and phase offset information from the first phase offset calibration factor of any one of the antennas; and performing calibration compensation on any one of the antennas based on the time offset information and the phase offset information.

[0355] As a possible implementation manner, the processing unit 2130 is specifically configured to: select an initial sending RRU from the indoor distributed system; and perform at least one round of cyclic calibration process according to the initial sending RRU, to determine a to-be-calibrated RRU in each round of cyclic calibration process from the indoor distributed system, and determine a second phase offset calibration factor of the to-be-calibrated RRU, and perform phase offset calibration on the to-be-calibrated RRU according to the second phase offset calibration factor of the to-be-calibrated RRU.

[0356] As a possible implementation manner, the processing unit 2130 performs a first round of the at least one round of the cyclic calibration process, specifically: adding the initial sending RRU to the calibrated list, and sending the second calibration sequence to a first other RRU through the initial sending RRU; wherein the first other RRU refers to an RRU in the indoor distributed system except the initial sending RRU; taking an RRU closest to the initial sending RRU in the first other RRU as a to-be-calibrated RRU of the first round of the cyclic calibration process; sending the second calibration sequence to a second other RRU through the to-be-calibrated RRU of the first round of the cyclic calibration process; wherein the second other RRU refers to an RRU in the indoor distributed system except the to-be-calibrated RRU of the first round of the cyclic calibration process; determining a second phase offset calibration factor of the to-be-calibrated RRU of the first round of the cyclic calibration process according to the second calibration sequence received by the to-be-calibrated RRU of the first round of the cyclic calibration process and the second calibration sequence received by the initial sending RRU; and performing phase offset calibration on the to-be-calibrated RRU of the first round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the first round of the cyclic calibration process, and adding the to-be-calibrated RRU of the first round of the cyclic calibration process to the calibrated list.

[0357] As a possible implementation manner, the processing unit 2130 performs a qth round of the at least one round of the cyclic calibration process, specifically: judging whether all RRU in the indoor distributed system are contained in the calibrated list; if yes, ending the cyclic calibration process, and if not, selecting a to-be-calibrated RRU of the qth round of the cyclic calibration process from the RRU not in the calibrated list, and adding the to-be-calibrated RRU of the qth round of the cyclic calibration process to the calibrated list; wherein q is a positive integer greater than 1; sending the second calibration sequence to a third other RRU through the to-be-calibrated RRU of the qth round of the cyclic calibration process; wherein the third other RRU refers to an RRU in the indoor distributed system except the to-be-calibrated RRU of the qth round of the cyclic calibration process; determining an RRU closest to the to-be-calibrated RRU of the qth round of the cyclic calibration process from the RRU in the calibrated list; determining a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second calibration sequence sent by the calibrated RRU and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the calibrated RRU; and performing phase offset calibration on the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process.

[0358] As a possible implementation manner, when each RRU transmits the second calibration sequence, a calibration timer corresponding to the RRU is started; the processing unit 2130 is specifically configured to: select a reference RRU whose calibration timer does not time out from the calibrated list; determine whether there is a first target RRU in the RRU not in the calibrated list; the first target RRU is an RRU that receives the second calibration sequence transmitted by the reference RRU, and the SNR of the second calibration sequence received by the first target RRU is greater than a first set threshold; if there is the first target RRU, the first target RRU closest to the reference RRU is taken as a to-be-calibrated RRU in the qth round of the cyclic calibration process.

[0359] As a possible implementation manner, the processing unit 2130 is further configured to: if there is no first target RRU, select a to-be-calibrated RRU in the qth round of the cyclic calibration process from the RRU not in the calibrated list based on the RSRP of all the second calibration sequences received by each RRU not in the calibrated list, and add the to-be-calibrated RRU in the qth round of the cyclic calibration process to the calibrated list; transmit the second calibration sequence by the to-be-calibrated RRU in the qth round of the cyclic calibration process to the RRU in the calibrated list; determine whether there is a second target RRU in the calibrated list; the SNR of the second calibration sequence transmitted by the to-be-calibrated RRU in the qth round of the cyclic calibration process received by the second target RRU is greater than the first set threshold; if there is the second target RRU, determine a third target RRU closest to the to-be-calibrated RRU in the qth round of the cyclic calibration process from the second target RRU; determine the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second calibration sequence transmitted by the to-be-calibrated RRU in the qth round of the cyclic calibration process received by the third target RRU, and according to the second calibration sequence transmitted by the third target RRU received by the to-be-calibrated RRU in the qth round of the cyclic calibration process; and perform phase offset calibration on the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process.

[0360] As a possible implementation manner, the processing unit 2130 is further configured to: if there is no second target RRU, reselect the initial transmission RRU from the RRU not in the calibrated list; and reperform at least one round of the cyclic calibration process according to the reselected initial transmission RRU.

[0361] As a possible implementation manner, the processing unit 2130 performs the qth round of the cyclic calibration process in the at least one round of cyclic calibration process, specifically: judging whether all RRUs in the indoor distributed system are contained in the calibrated list; if yes, ending the cyclic calibration process, and if not, selecting a plurality of sending RRUs corresponding to the qth round of the cyclic calibration process from the calibrated list; wherein q is a positive integer greater than 1; taking the remaining RRUs as the to-be-calibrated RRUs of the qth round of the cyclic calibration process, and sending the second calibration sequence to the plurality of sending RRUs through the to-be-calibrated RRUs of the qth round of the cyclic calibration process; wherein the remaining RRUs refer to the RRUs in the indoor distributed system except the RRUs in the calibrated list; determining the second phase offset calibration factor of the to-be-calibrated RRUs of the qth round of the cyclic calibration process according to the second calibration sequence sent by the plurality of sending RRUs and received by the to-be-calibrated RRUs of the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRUs of the qth round of the cyclic calibration process and received by the plurality of sending RRUs; and performing phase offset calibration on the to-be-calibrated RRUs of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRUs of the qth round of the cyclic calibration process.

[0362] As a possible implementation manner, the processing unit 2130 is specifically configured to: for any to-be-calibrated RRU in the to-be-calibrated RRUs of the qth round of the cyclic calibration process, determining a fourth target RRU closest to the any to-be-calibrated RRU from the plurality of sending RRUs according to the RSRP of the second calibration sequence sent by the plurality of sending RRUs and received by the any to-be-calibrated RRU; sending the second calibration sequence to the fourth target RRU through the any to-be-calibrated RRU based on the code division multiplexing transmission mode; and determining the second phase offset calibration factor of the any to-be-calibrated RRU according to the second calibration sequence sent by the any to-be-calibrated RRU and received by the fourth target RRU, and according to the second calibration sequence sent by the fourth target RRU and received by the any to-be-calibrated RRU.

[0363] As a possible implementation manner, the processing unit 2130 is specifically configured to: for any to-be-calibrated RRU in the to-be-calibrated RRUs of the qth round of the cyclic calibration process, sending the second calibration sequence to the plurality of sending RRUs through the any to-be-calibrated RRU based on the code division multiplexing transmission mode; determining a plurality of phase offset calibration factors corresponding to the any to-be-calibrated RRU according to the second calibration sequence sent by the plurality of sending RRUs and received by the any to-be-calibrated RRU, and according to the second calibration sequence sent by the any to-be-calibrated RRU and received by the plurality of sending RRUs; and determining the second phase offset calibration factor of the any to-be-calibrated RRU according to the mean value of the plurality of phase offset calibration factors.

[0364] As a possible implementation manner, the processing unit 2130 is specifically configured to: perform calibration measurement on the second calibration sequence transmitted between the RRUs with a distance less than the second set threshold in the indoor distributed system to obtain an initial phase offset calibration factor of the RRU with the distance less than the second set threshold; and adjust the initial phase offset calibration factor of each RRU based on the least square method to obtain a second phase offset calibration factor of each RRU.

[0365] As a possible implementation manner, the processing unit 2130 is specifically configured to: for any antenna, determine a target phase offset calibration factor of the any antenna according to the product of the second phase offset calibration factor of the RRU to which the any antenna belongs and the first phase offset calibration factor of the any antenna; and perform phase offset calibration on the any antenna based on the target phase offset calibration factor of the any antenna.

[0366] As a possible implementation manner, the air interface calibration apparatus 2100 of the indoor distributed system can further include a determination unit configured to determine that the indoor distributed system satisfies a trigger condition of air interface calibration, wherein the trigger condition of air interface calibration includes at least one of the following: a set period is reached, wherein a period length of the set period is determined according to a measurement period of phase drift between different antennas in the indoor distributed system; at least one RRU is newly added in the indoor distributed system; at least one RRU in the indoor distributed system is switched from a working state to an off state; a deployment position of at least one RRU in the indoor distributed system is changed; at least one RRU in the indoor distributed system is switched from a power-off state to a power-on state; a first network performance index obtained by the indoor distributed system using a non-codebook technology is lower than a second network performance index obtained by the indoor distributed system using a codebook technology, and a difference between the first network performance index and the second network performance index is greater than a third set threshold.

[0367] It should be noted that the air interface calibration apparatus of the indoor distributed system provided by the embodiments of the present application can realize all the method steps achieved by the method embodiments described above and achieve the same technical effects, and therefore, the same parts and beneficial effects of the embodiments as the method embodiments will not be described in detail. Figures 5 to 17

[0368] ​It should be noted that the division of the unit in the embodiments of the present application is illustrative, and is only a logical function division. In actual implementation, another division manner can be used. In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit. When the integrated unit is realized in the form of a software functional unit and sold or used as an independent product, the integrated unit can be stored in a processor-readable storage medium. Based on this understanding, the technical solutions of the present application, essentially or the part that contributes to the prior art, or all or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network side device, etc.) or a processor to perform all or part of the steps of the methods in each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0369] In another aspect, the embodiments of the present application also provide a processor-readable storage medium, which stores a computer program. The computer program is used to make a processor execute the method shown in any of the embodiments of the present application. Figures 5 to 17 The processor-readable storage medium can be any available medium or data storage device that can be accessed by the processor, including but not limited to a magnetic memory (such as a floppy disk, a hard disk, a magnetic tape, a magneto-optical disk (MO), etc.), an optical memory (such as a CD, a DVD, a BD, a HVD, etc.), and a semiconductor memory (such as a ROM, an EPROM, an EEPROM, a non-volatile memory (NAND FLASH), a solid state disk (SSD)), etc.

[0370] In order to implement the above-mentioned embodiments, the present application further provides a computer program product. The computer program product includes a computer program, which, when executed by a processor, implements the method shown in any of the embodiments of the present application. Figures 5 to 17 The method shown in any of the embodiments of the present application.

[0371] Those skilled in the art will appreciate that embodiments of the present application can be readily used as software, hardware, or a combination of software and hardware. In one

[0372] The present application is described in reference to the flow diagrams and / or block diagrams of the methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flow diagrams and / or block diagrams, and combinations of blocks in the flow diagrams and / or block diagrams, can be implemented by computer executable instructions. Figure 1 one or more functions specified by one or more blocks Figure 1 means for performing the function specified by one or more blocks

[0373] These processor-executable instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable data devices to generate computer-implemented processes, thus the instructions executed on the computer or other programmable devices provide steps for implementing the flow Figure 1 one or more functions specified by one or more blocks Figure 1 means for performing the function specified by one or more blocks

[0374] These processor-executable instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable data devices to generate computer-implemented processes, thus the instructions executed on the computer or other programmable devices provide steps for implementing the flow Figure 1 one or more functions specified by one or more blocks Figure 1 means for performing the function specified by one or more blocks

[0375] Obviously, persons having ordinary skill in the art can make various modifications and variations without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims and their equivalents, it is intended that the present application embrace such modifications and variations.

Claims

1. An air interface calibration method for an indoor distributed system, characterized in that: The indoor distributed system comprises a baseband processing unit (BBU), at least one hub (Hub) connected to the BBU, and a plurality of radio remote units (RRU) connected to the Hub, comprising: The first calibration sequence transmitted by the multiple antennas in the same RRU through the set transmission mode is measured for calibration, and a first phase offset calibration factor of each antenna in the same RRU is obtained. The first phase offset calibration factor of each antenna in the same RRU is used to calibrate the phase offset of each antenna in the same RRU. The second calibration sequence transmitted by the different RRUs is measured for calibration, and a second phase offset calibration factor of each RRU is obtained, and the second phase offset calibration factor of each RRU is used to calibrate the phase offset of each antenna in each RRU. The first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

2. The method of claim 1, wherein, The first calibration sequence is a calibration sequence generated by the BBU according to the first RE occupied by the same RRU, which is different from the RE occupied by the multiple RRUs connected to the same Hub. The set transmission mode comprises frequency division multiplexing transmission mode, and the frequency division multiplexing transmission mode comprises: When the i-th moment is reached, the first calibration sequence is transmitted to the remaining antennas through the i-th antenna in the same RRU; wherein i is a positive integer, the first calibration sequence is transmitted by the i-th antenna using the first RE, and the remaining antennas are the antennas in the same RRU except the i-th antenna. The first calibration sequence transmitted by the multiple antennas in the same RRU through the set transmission mode is measured for calibration, and a first phase offset calibration factor of each antenna in the same RRU is obtained. The first calibration sequence received by the remaining antennas at different moments and the first calibration sequence received by the i-th antenna are measured for calibration to obtain the first phase offset calibration factor of each antenna in the same RRU.

3. The method of claim 1, wherein, The REs occupied by different antennas in the same RRU are different, and the REs occupied by the antennas of the same port in the multiple RRUs connected to the same Hub are the same; the first calibration sequence transmitted by any antenna is a calibration sequence generated by the BBU according to the second RE occupied by the any antenna; The set transmission mode comprises time division multiplexing transmission mode, and the time division multiplexing transmission mode comprises: The first calibration sequence is transmitted to the j-th antenna in the same RRU through the other antennas using the second REs occupied by the other antennas; wherein j is a positive integer, and the other antennas are the antennas in the same RRU except the j-th antenna; The first calibration sequence is transmitted to the other antennas through the j-th antenna using the second REs occupied by the other antennas; The first calibration sequence transmitted by the multiple antennas in the same RRU through the set transmission mode is measured for calibration, and a first phase offset calibration factor of each antenna in the same RRU is obtained. The first calibration sequence received by the jth antenna and the first calibration sequence received by the other antennas are subjected to calibration measurement to obtain the first phase offset calibration factor of the other antennas.

4. The method of claim 1, wherein, The first calibration sequence sent by any antenna is a calibration sequence generated by the BBU according to the cyclic shift occupied by the RRU to which the antenna belongs and the third RE occupied by the antenna, different from the cyclic shift occupied by the multiple RRUs connected to the same Hub and the RE occupied by the multiple antennas in the same RRU. The set transmission mode includes a code division multiplexing transmission mode, and the code division multiplexing transmission mode includes: The first calibration sequence is sent to the kth antenna in the same RRU by the other antennas through the third RE occupied by the other antennas, wherein k is a positive integer, and the other antennas are antennas other than the kth antenna in the same RRU. The first calibration sequence is sent to the other antennas by the kth antenna through the third RE occupied by the other antennas. The calibration measurement on the first calibration sequence sent by the multiple antennas in the same RRU to each other through the set transmission mode to obtain the first phase offset calibration factor of each antenna in the same RRU includes: The first calibration sequence received by the kth antenna and the first calibration sequence received by the other antennas are subjected to calibration measurement to obtain the first phase offset calibration factor of the other antennas.

5. The method of claim 1, wherein, The phase offset calibration of each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU includes: For any antenna in the same RRU, when the downlink signal sent by the BBU to the same RRU is a frequency domain signal, the phase offset compensation of the any antenna is based on the first phase offset calibration factor of the any antenna. When the downlink signal is a time domain signal, the time offset information and the phase offset information are extracted from the first phase offset calibration factor of the any antenna. The calibration compensation of the any antenna is based on the time offset information and the phase offset information.

6. The method of claim 1, wherein, The calibration measurement on the second calibration sequence sent by the multiple RRUs to each other to obtain the second phase offset calibration factor of each RRU and the phase offset calibration of each antenna in each RRU based on the second phase offset calibration factor of each RRU includes: An initial sending RRU is selected from the indoor distributed system; At least one round of cyclic calibration process is performed according to the initial sending RRU to determine the RRU to be calibrated in each round of cyclic calibration process from the indoor distributed system, determine the second phase offset calibration factor of the RRU to be calibrated, and perform the phase offset calibration of the RRU to be calibrated according to the second phase offset calibration factor of the RRU to be calibrated.

7. The method of claim 6, wherein, The first round of cyclic calibration process in the at least one round of cyclic calibration process includes: adding the initial sending RRU to a calibrated list, and sending a second calibration sequence to a first other RRU by the initial sending RRU, wherein the first other RRU refers to an RRU in the indoor distributed system other than the initial sending RRU; selecting, from the first other RRUs, an RRU closest to the initial sending RRU as a to-be-calibrated RRU in the first round of the cyclic calibration process; sending a second calibration sequence to a second other RRU by the to-be-calibrated RRU in the first round of the cyclic calibration process, wherein the second other RRU refers to an RRU in the indoor distributed system other than the to-be-calibrated RRU in the first round of the cyclic calibration process; determining a second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process according to the second calibration sequence received by the to-be-calibrated RRU in the first round of the cyclic calibration process and the second calibration sequence received by the initial sending RRU; performing phase offset calibration on the to-be-calibrated RRU in the first round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU in the first round of the cyclic calibration process, and adding the to-be-calibrated RRU in the first round of the cyclic calibration process to the calibrated list.

8. The method of claim 7, wherein, The qth round of the cyclic calibration process in the at least one round of the cyclic calibration process includes: determining whether all RRUs in the indoor distributed system are included in the calibrated list; if yes, ending the cyclic calibration process, and if no, selecting a to-be-calibrated RRU in the qth round of the cyclic calibration process from the RRUs not in the calibrated list, and adding the to-be-calibrated RRU in the qth round of the cyclic calibration process to the calibrated list, wherein q is a positive integer greater than 1; sending a second calibration sequence to a third other RRU by the to-be-calibrated RRU in the qth round of the cyclic calibration process, wherein the third other RRU refers to an RRU in the indoor distributed system other than the to-be-calibrated RRU in the qth round of the cyclic calibration process; determining a calibrated RRU closest to the to-be-calibrated RRU in the qth round of the cyclic calibration process from the RRUs in the calibrated list; determining a second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second calibration sequence sent by the calibrated RRU and received by the to-be-calibrated RRU in the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process and received by the calibrated RRU; performing phase offset calibration on the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process.

9. The method of claim 8, wherein, starting a calibration timer corresponding to each RRU when the RRU sends a second calibration sequence; the selecting of the to-be-calibrated RRU in the qth round of the cyclic calibration process from the RRUs not in the calibrated list includes: selecting a reference RRU whose calibration timer has not timed out from the calibrated list; determining whether a first target RRU exists in the RRUs not in the calibrated list, wherein the first target RRU is an RRU receiving a second calibration sequence sent by the reference RRU, and the SNR of the second calibration sequence received by the first target RRU is greater than a first preset threshold; if the first target RRU exists, taking the first target RRU closest to the reference RRU as a to-be-calibrated RRU in the qth round of the cyclic calibration process.

10. The method of claim 9, wherein, The method further comprises: if the first target RRU does not exist, selecting a to-be-calibrated RRU in the qth round of the cyclic calibration process from the RRUs not in the calibrated list based on the RSRP of all the second calibration sequences received by each RRU not in the calibrated list, and adding the to-be-calibrated RRU in the qth round of the cyclic calibration process to the calibrated list; sending, by the to-be-calibrated RRU in the qth round of the cyclic calibration process, a second calibration sequence to the RRUs in the calibrated list; determining whether a second target RRU exists in the calibrated list, wherein the SNR of the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process and received by the second target RRU is greater than the first preset threshold; if the second target RRU exists, determining a third target RRU closest to the to-be-calibrated RRU in the qth round of the cyclic calibration process from the second target RRU; determining a second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process and received by the third target RRU, and according to the second calibration sequence sent by the third target RRU and received by the to-be-calibrated RRU in the qth round of the cyclic calibration process; performing phase offset calibration on the to-be-calibrated RRU in the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU in the qth round of the cyclic calibration process.

11. The method of claim 10, wherein, The method further comprises: if the second target RRU does not exist, reselecting an initial sending RRU from the RRUs not in the calibrated list; re-executing at least one round of the cyclic calibration process according to the reselected initial sending RRU.

12. The method of claim 7, wherein, The qth round of the cyclic calibration process in the at least one round of the cyclic calibration process comprises: determining whether all the RRUs in the indoor distributed system are included in the calibrated list; if yes, ending the cyclic calibration process, and if no, selecting a plurality of sending RRUs corresponding to the qth round of the cyclic calibration process from the calibrated list, wherein q is a positive integer greater than 1; taking the remaining RRUs as to-be-calibrated RRUs in the qth round of the cyclic calibration process, and sending, by the to-be-calibrated RRUs in the qth round of the cyclic calibration process, a second calibration sequence to the plurality of sending RRUs, wherein the remaining RRUs refer to the RRUs in the indoor distributed system other than the RRUs in the calibrated list; determining, according to the second calibration sequences sent by the multiple sending RRUs and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequences sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the multiple sending RRUs, a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process; performing phase offset calibration on the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process.

13. The method of claim 12, wherein, The sending, by the to-be-calibrated RRU of the qth round of the cyclic calibration process, of the second calibration sequence to the multiple sending RRUs comprises: For any to-be-calibrated RRU of the qth round of the cyclic calibration process, determining, from the multiple sending RRUs, a fourth target RRU closest to the any to-be-calibrated RRU according to the RSRP of the second calibration sequence sent by the multiple sending RRUs and received by the any to-be-calibrated RRU; sending, by the any to-be-calibrated RRU, the second calibration sequence to the fourth target RRU based on a code division multiplexing transmission mode; The determining, according to the second calibration sequences sent by the multiple sending RRUs and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequences sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the multiple sending RRUs, a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process comprises: determining, according to the second calibration sequences sent by the any to-be-calibrated RRU and received by the fourth target RRU, and according to the second calibration sequences sent by the fourth target RRU and received by the any to-be-calibrated RRU, a second phase offset calibration factor of the any to-be-calibrated RRU.

14. The method of claim 12, wherein, The sending, by the to-be-calibrated RRU of the qth round of the cyclic calibration process, of the second calibration sequence to the multiple sending RRUs comprises: For any to-be-calibrated RRU of the qth round of the cyclic calibration process, sending, by the any to-be-calibrated RRU, the second calibration sequence to the multiple sending RRUs based on a code division multiplexing transmission mode; The determining, according to the second calibration sequences sent by the multiple sending RRUs and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequences sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the multiple sending RRUs, a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process comprises: determining, according to the second calibration sequences sent by the any to-be-calibrated RRU and received by the multiple sending RRUs, and according to the second calibration sequences sent by the multiple sending RRUs and received by the any to-be-calibrated RRU, a plurality of phase offset calibration factors corresponding to the any to-be-calibrated RRU; determining the second phase offset calibration factor of the any to-be-calibrated RRU according to the mean value of the plurality of phase offset calibration factors.

15. The method of claim 1, wherein, The calibration measurement on the second calibration sequences transmitted between different RRUs obtains a second phase offset calibration factor of each RRU, and the calibration measurement on the second calibration sequences transmitted between different RRUs includes: The calibration measurement on the second calibration sequences transmitted between different RRUs obtains a second phase offset calibration factor of each RRU, and the calibration measurement on the second calibration sequences transmitted between different RRUs includes: The calibration measurement on the second calibration sequences transmitted between different RRUs obtains a second phase offset calibration factor of each RRU, and the calibration measurement on the second calibration sequences transmitted between different RRUs includes:

16. The method of any one of claims 1-15, wherein, The phase offset calibration of each antenna in each RRU based on the second phase offset calibration factor of each RRU includes: For any antenna, the target phase offset calibration factor of the any antenna is determined according to the product of the second phase offset calibration factor of the RRU to which the any antenna belongs and the first phase offset calibration factor of the any antenna; The phase offset calibration of the any antenna is based on the target phase offset calibration factor of the any antenna.

17. The method of any one of claims 1-15, wherein, Before the calibration measurement on the first calibration sequences transmitted between multiple antennas in the same RRU through a set transmission mode obtains the first phase offset calibration factor of each antenna in the same RRU, the method further includes: The trigger condition of the air interface calibration is determined to be met; The trigger condition of the air interface calibration includes at least one of the following: A set period is reached, and a period length of the set period is determined according to a measurement period of phase drift between different antennas in the indoor distributed system; At least one RRU is newly added to the indoor distributed system; At least one RRU in the indoor distributed system is switched from an operating state to an off state; The deployment position of at least one RRU in the indoor distributed system is changed; At least one RRU in the indoor distributed system is switched from a power-off state to a power-on state; A first network performance index obtained by using a non-codebook technology by the indoor distributed system is lower than a second network performance index obtained by using a codebook technology by the indoor distributed system, and a difference between the first network performance index and the second network performance index is greater than a third set threshold.

18. A network device, comprising: Memory, transceiver, processor; Memory, for storing a computer program; transceiver, for transceiving data under the control of the processor; processor, for reading the computer program in the memory and performing the following operations: The calibration measurement on the first calibration sequences transmitted between multiple antennas in the same RRU through a set transmission mode obtains the first phase offset calibration factor of each antenna in the same RRU; wherein, the RRU is deployed in an indoor distributed system, and the indoor distributed system includes a baseband processing unit (BBU), at least one hub (Hub) connected to the BBU, and multiple RRUs connected to the Hub; The phase offset calibration of each antenna in the same RRU is based on the first phase offset calibration factor of each antenna in the same RRU. The second calibration sequence transmitted between different RRUs is measured to obtain a second phase offset calibration factor of each RRU, and each antenna in each RRU is calibrated based on the second phase offset calibration factor of each RRU. The first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

19. The network device of claim 18, wherein, The first calibration sequence is generated by the BBU according to the first RE occupied by the same RRU. The transmission mode includes frequency division multiplexing transmission mode, and the frequency division multiplexing transmission mode includes: When the i-th moment is reached, the first calibration sequence is transmitted to the remaining antennas through the i-th antenna in the same RRU; wherein i is a positive integer, the first calibration sequence is transmitted by the i-th antenna using the first RE, and the remaining antennas are the antennas in the same RRU except the i-th antenna. The processor performs calibration measurement on the first calibration sequence transmitted between the multiple antennas in the same RRU through the set transmission mode to obtain a first phase offset calibration factor of each antenna in the same RRU, and specifically: The first calibration sequence received by the i-th antenna and the first calibration sequence received by the remaining antennas are measured to obtain the first phase offset calibration factor of each antenna in the same RRU.

20. The network device of claim 18, wherein, The REs occupied by different antennas in the same RRU are different, and the REs occupied by the antennas of the same port in the multiple RRUs connected to the same Hub are the same; the first calibration sequence transmitted by any antenna is a calibration sequence generated by the BBU according to the second RE occupied by the any antenna; The transmission mode includes time division multiplexing transmission mode, and the time division multiplexing transmission mode includes: The first calibration sequence is transmitted to the j-th antenna in the same RRU through the other antennas using the second REs occupied by the other antennas; wherein j is a positive integer, and the other antennas are the antennas in the same RRU except the j-th antenna. The first calibration sequence is transmitted to the other antennas through the j-th antenna using the second REs occupied by the other antennas. The processor performs calibration measurement on the first calibration sequence transmitted between the multiple antennas in the same RRU through the set transmission mode to obtain a first phase offset calibration factor of each antenna in the same RRU, and specifically: The first calibration sequence received by the j-th antenna and the first calibration sequence received by the other antennas are measured to obtain the first phase offset calibration factor of the other antennas.

21. The network device of claim 18, wherein, The REs occupied by the multiple antennas in the same RRU are different, and the cyclic shifts occupied by the multiple RRUs connected to the same Hub are different; the first calibration sequence transmitted by any antenna is a calibration sequence generated by the BBU according to the cyclic shift occupied by the RRU to which the any antenna belongs and the third RE occupied by the any antenna; The set transmission mode includes a code division multiplexing transmission mode, and the code division multiplexing transmission mode includes: The first calibration sequence is transmitted to the kth antenna through the third RE occupied by the other antennas, and the kth antenna is used as a reference. The first calibration sequence is transmitted to the other antennas through the third RE occupied by the other antennas. The processor performs calibration measurement on the first calibration sequence transmitted between the multiple antennas in the same RRU through the set transmission mode, and obtains the first phase offset calibration factor of each antenna in the same RRU, and specifically: The first calibration sequence received by the kth antenna and the first calibration sequence received by the other antennas are calibrated and measured to obtain the first phase offset calibration factor of the other antennas.

22. The network device of claim 18, wherein, The processor performs phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU, and specifically: For any antenna in the same RRU, when the downlink signal transmitted by the BBU to the same RRU is a frequency domain signal, the first phase offset calibration factor of the any antenna is used for phase offset compensation of the any antenna; When the downlink signal is a time domain signal, the time offset information and the phase offset information are extracted from the first phase offset calibration factor of the any antenna; The any antenna is calibrated and compensated based on the time offset information and the phase offset information.

23. The network device of claim 18, wherein, The processor performs calibration measurement on the second calibration sequence transmitted between different RRUs, obtains the second phase offset calibration factor of each RRU, and performs phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU, and specifically: An initial transmission RRU is selected from the indoor distributed system; At least one round of cyclic calibration process is performed according to the initial transmission RRU to determine a to-be-calibrated RRU in each round of cyclic calibration process from the indoor distributed system, determine the second phase offset calibration factor of the to-be-calibrated RRU, and perform phase offset calibration on the to-be-calibrated RRU according to the second phase offset calibration factor of the to-be-calibrated RRU.

24. The network device of claim 23, wherein, The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission RRU in the first other RRU is used as the to-be-calibrated RRU in the first round of cyclic calibration process; and The processor performs the first round of cyclic calibration process in the at least one round of cyclic calibration process, and specifically: The initial transmission RRU is added to a calibrated list, and a second calibration sequence is transmitted to a first other RRU through the initial transmission RRU, wherein the first other RRU refers to an RRU in the indoor distributed system except the initial transmission RRU; The RRU closest to the initial transmission R sending, by the to-be-calibrated RRU of the first round of the round-robin calibration process, a second calibration sequence to a second other RRU; the second other RRU is an RRU in the indoor distributed system other than the to-be-calibrated RRU of the first round of the round-robin calibration process; determining, according to the second calibration sequence received by the to-be-calibrated RRU of the first round of the round-robin calibration process and the second calibration sequence received by the initial sending RRU, a second phase offset calibration factor of the to-be-calibrated RRU of the first round of the round-robin calibration process; performing, according to the second phase offset calibration factor of the to-be-calibrated RRU of the first round of the round-robin calibration process, phase offset calibration on the to-be-calibrated RRU of the first round of the round-robin calibration process, and adding the to-be-calibrated RRU of the first round of the round-robin calibration process to the calibrated list.

25. The network device of claim 24, wherein, The processor performs a qth round of the round-robin calibration process, and specifically: determining whether all RRU in the indoor distributed system are included in the calibrated list; if yes, ending the round-robin calibration process, and if no, selecting a to-be-calibrated RRU of the qth round of the round-robin calibration process from the RRU not located in the calibrated list and adding the to-be-calibrated RRU of the qth round of the round-robin calibration process to the calibrated list; q is a positive integer greater than 1; sending, by the to-be-calibrated RRU of the qth round of the round-robin calibration process, a second calibration sequence to a third other RRU; the third other RRU is an RRU in the indoor distributed system other than the to-be-calibrated RRU of the qth round of the round-robin calibration process; determining, from the RRU in the calibrated list, a calibrated RRU closest to the to-be-calibrated RRU of the qth round of the round-robin calibration process; determining, according to the second calibration sequence sent by the calibrated RRU and received by the to-be-calibrated RRU of the qth round of the round-robin calibration process and according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the round-robin calibration process and received by the calibrated RRU, a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the round-robin calibration process; performing, according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the round-robin calibration process, phase offset calibration on the to-be-calibrated RRU of the qth round of the round-robin calibration process.

26. The network device of claim 25, wherein, starting a calibration timer corresponding to the RRU when the RRU sends a second calibration sequence; The processor performs the operation of selecting a to-be-calibrated RRU of a qth round of the round-robin calibration process from the calibrated list, and specifically: selecting, from the calibrated list, a reference RRU whose calibration timer has not expired; determining, from the RRU not located in the calibrated list, whether there is a first target RRU; the first target RRU is an RRU that receives the second calibration sequence sent by the reference RRU, and the SNR of the second calibration sequence received by the first target RRU is greater than a first set threshold; if the first target RRU exists, the to-be-calibrated RRU of the qth round of the round-robin calibration process is the first target RRU closest to the reference RRU.

27. The network device of claim 26, wherein, The processor is further configured to perform the following operations: if the first target RRU does not exist, selecting a to-be-calibrated RRU of a qth round of the cyclic calibration process from RRU not in the calibrated list based on RSRP of all second calibration sequences received by each RRU not in the calibrated list, and adding the to-be-calibrated RRU of the qth round of the cyclic calibration process to the calibrated list; sending, by the to-be-calibrated RRU of the qth round of the cyclic calibration process, a second calibration sequence to the RRU in the calibrated list; determining whether a second target RRU exists in the calibrated list, wherein SNR of the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the second target RRU is greater than the first set threshold value; if the second target RRU exists, determining a third target RRU closest to the to-be-calibrated RRU of the qth round of the cyclic calibration process from the second target RRU; determining a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the third target RRU, and according to the second calibration sequence sent by the third target RRU and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process; performing phase offset calibration on the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process.

28. The network device of claim 27, wherein, The processor is further configured to perform the following operations: if the second target RRU does not exist, reselecting an initial sending RRU from RRU not in the calibrated list; re-executing at least one round of the cyclic calibration process according to the reselected initial sending RRU.

29. The network device of claim 24, wherein, The processor performs a qth round of the cyclic calibration process in the at least one round of the cyclic calibration process, and specifically: determining whether all RRU in the indoor distributed system are included in the calibrated list; if yes, ending the cyclic calibration process, and if no, selecting a plurality of sending RRU corresponding to the qth round of the cyclic calibration process from the calibrated list; wherein q is a positive integer greater than 1; taking the remaining RRU as to-be-calibrated RRU of the qth round of the cyclic calibration process, and sending, by the to-be-calibrated RRU of the qth round of the cyclic calibration process, a second calibration sequence to the plurality of sending RRU; wherein the remaining RRU refers to RRU in the indoor distributed system other than RRU in the calibrated list; determining a second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second calibration sequence sent by the plurality of sending RRU and received by the to-be-calibrated RRU of the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU of the qth round of the cyclic calibration process and received by the plurality of sending RRU; performing phase offset calibration on the to-be-calibrated RRU of the qth round of the cyclic calibration process according to the second phase offset calibration factor of the to-be-calibrated RRU of the qth round of the cyclic calibration process.

30. The network device of claim 29, wherein, The processor performs sending, by the to-be-calibrated RRU in the qth round of the cyclic calibration process, a second calibration sequence to the multiple sending RRUs, specifically: For any to-be-calibrated RRU in the qth round of the cyclic calibration process, the processor determines, from the multiple sending RRUs, a fourth target RRU closest to the any to-be-calibrated RRU according to the RSRP of the second calibration sequence sent by the multiple sending RRUs and received by the any to-be-calibrated RRU; The processor performs sending, by the any to-be-calibrated RRU, a second calibration sequence to the fourth target RRU based on a code division multiplexing transmission mode. The processor performs determining, by the to-be-calibrated RRU in the qth round of the cyclic calibration process, a second phase offset calibration factor of the to-be-calibrated RRU according to the second calibration sequence sent by the multiple sending RRUs and received by the to-be-calibrated RRU in the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process and received by the multiple sending RRUs, specifically: The processor performs determining, by the any to-be-calibrated RRU, a second phase offset calibration factor of the any to-be-calibrated RRU according to the second calibration sequence sent by the any to-be-calibrated RRU and received by the fourth target RRU, and according to the second calibration sequence sent by the fourth target RRU and received by the any to-be-calibrated RRU.

31. The network device of claim 29, wherein, The processor performs sending, by the to-be-calibrated RRU in the qth round of the cyclic calibration process, a second calibration sequence to the multiple sending RRUs, specifically: For any to-be-calibrated RRU in the qth round of the cyclic calibration process, the processor performs sending, by the any to-be-calibrated RRU, a second calibration sequence to the multiple sending RRUs based on a code division multiplexing transmission mode. The processor performs determining, by the to-be-calibrated RRU in the qth round of the cyclic calibration process, a second phase offset calibration factor of the to-be-calibrated RRU according to the second calibration sequence sent by the multiple sending RRUs and received by the to-be-calibrated RRU in the qth round of the cyclic calibration process, and according to the second calibration sequence sent by the to-be-calibrated RRU in the qth round of the cyclic calibration process and received by the multiple sending RRUs, specifically: The processor performs determining, by the any to-be-calibrated RRU, a plurality of phase offset calibration factors corresponding to the any to-be-calibrated RRU according to the second calibration sequence sent by the any to-be-calibrated RRU and received by the multiple sending RRUs, and according to the second calibration sequence sent by the multiple sending RRUs and received by the any to-be-calibrated RRU. The processor performs determining, by the any to-be-calibrated RRU, a second phase offset calibration factor of the any to-be-calibrated RRU according to a mean value of the plurality of phase offset calibration factors.

32. The network device of claim 18, wherein, The processor performs performing calibration measurement on the second calibration sequence sent between different RRUs, to obtain a second phase offset calibration factor of each RRU, specifically: The processor performs performing calibration measurement on the second calibration sequence sent between RRUs with a distance less than a second set threshold in the indoor distributed system, to obtain an initial phase offset calibration factor of the RRU with the distance less than the second set threshold. The processor performs adjusting, based on a least square method, the initial phase offset calibration factor of each RRU, to obtain a second phase offset calibration factor of each RRU.

33. The network device of any of claims 18-32, wherein, The processor performs phase offset calibration on each antenna in each RRU based on a second phase offset calibration factor of each RRU, specifically: For any antenna, the target phase offset calibration factor of the any antenna is determined according to the product of the second phase offset calibration factor of the RRU to which the any antenna belongs and the first phase offset calibration factor of the any antenna; The phase offset calibration is performed on the any antenna based on the target phase offset calibration factor of the any antenna.

34. The network device of any of claims 18-32, wherein, Before the processor performs calibration measurement on the first calibration sequence transmitted by setting a transmission mode among multiple antennas in the same RRU to each other to obtain the first phase offset calibration factor of each antenna in the same RRU, the processor is further configured to perform the following operations: Determine that the indoor distributed system satisfies a triggering condition of air interface calibration; The triggering condition of air interface calibration includes at least one of the following: A set period is reached; wherein the period length of the set period is determined according to the measurement period of the phase drift between different antennas in the indoor distributed system; At least one RRU is added to the indoor distributed system; At least one RRU in the indoor distributed system switches from an operating state to an off state; The deployment position of at least one RRU in the indoor distributed system changes; At least one RRU in the indoor distributed system switches from a power-off state to a power-on state; The first network performance index obtained by the indoor distributed system using a non-codebook technology is lower than the second network performance index obtained by the indoor distributed system using a codebook technology, and the difference between the first network performance index and the second network performance index is greater than a third set threshold.

35. An air interface calibration device for an indoor distributed system, characterized in that: The indoor distributed system includes a baseband processing unit (BBU), at least one hub (Hub) connected to the BBU, and a plurality of remote radio units (RRU) connected to the Hub, comprising: A measurement unit is configured to perform calibration measurement on a first calibration sequence transmitted by setting a transmission mode among multiple antennas in the same RRU to each other to obtain the first phase offset calibration factor of each antenna in the same RRU; A calibration unit is configured to perform phase offset calibration on each antenna in the same RRU based on the first phase offset calibration factor of each antenna in the same RRU; A processing unit is configured to perform calibration measurement on a second calibration sequence transmitted among different RRUs to obtain a second phase offset calibration factor of each RRU, and perform phase offset calibration on each antenna in each RRU based on the second phase offset calibration factor of each RRU. The first calibration sequence or the second calibration sequence is transmitted by the BBU to the RRU through the Hub.

36. A processor-readable storage medium, comprising: The processor readable storage medium stores a computer program, and the computer program is used to make the processor execute the method in any one of claims 1 to 17.

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